Rhenium(I)-tricarbonyl complexes with methimazole and its selenium analogue: Syntheses, characterization and cell toxicity.

{"full_text": " Journal of Inorganic Biochemistry 240 (2023) 112092\n\n\n Contents lists available at ScienceDirect\n\n\n Journal of Inorganic Biochemistry\n journal homepage: www.elsevier.com/locate/jinorgbio\n\n\n\n\nRhenium(I)-tricarbonyl complexes with methimazole and its selenium\nanalogue: Syntheses, characterization and cell toxicity\nFarideh Jalilehvand a, *, Valerie Brunskill a, Tran Si Bui Trung a, Isbel Lopetegui-Gonzalez b,\nCarrie S. Shemanko b, Benjamin S. Gelfand a, Jian-Bin Lin a\na\n Department of Chemistry, University of Calgary, Calgary, Alberta T2N 1N4, Canada\nb\n Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada\n\n\n\n\nA R T I C L E I N F O A B S T R A C T\n\nKeywords: This study explores the effect of a thione/selone ligand on the cell toxicity (in vitro) and light activity of diimine\nRhenium(I) tricarbonyl diimine complexes Re(CO)+ 3 complexes. Six rhenium(I) complexes with general formula fac-[Re(CO)3(N,N )X] were prepared,\n \u2032 +\nMethimazole where X = 2-mercapto-1-methylimidazole (methimazole; MMI), and 1-methylimidazole-2-selone (MSeI); N,N\u2032 =\n1-methylimidazole-2-selone\n 2,2\u2032 -bipyridine (bpy), 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (dmphen). Their tri\u00ad\nStructure\n flate salts were characterized using single-crystal X-ray diffraction, 1H, 13C and 2D NMR, UV\u2013vis and vibrational\nSpectroscopy\nCytotoxicity spectroscopy. Their cytotoxic properties were tested, showing significant cytotoxicity (IC50 = 8.0\u201355 \u03bcM) to\u00ad\n wards the human breast cancer cell line MDA-MB-231. The half-inhibitory concentration (IC50) for fac-[Re\n (CO)3(dmphen)(MMI)]+, the most toxic complex in this series (8.0 \u00b1 0.2 \u03bcM), was comparable to that of the\n corresponding aqua complex fac-[Re(CO)3(dmphen)(H2O)]+ with IC50 = 6.0 \u00b1 0.1 \u03bcM. The fac-[Re(CO)3(bpy)\n (MMI/MSeI)]+ complexes were somewhat less toxic towards the human embryonic kidney cell line HEK-293 T\n after 48 h of exposure. The stability of the complexes upon irradiation was monitored using UV\u2013vis spectroscopy,\n with no CO released when exposed to UV-A light (\u03bb = 365 nm).\n\n\n\n\n1. Introduction photodynamic therapy agents. These complexes are non-toxic in the dark\n at prescribed dosages, but when irradiated with visible light (penetrating\n Rhenium(I) diimine tricarbonyl complexes, fac-[Re(CO)3(N,N)X]+/0/\u2212 deeper into tissue than UV), they emit luminescence that in presence of\nwhere (N,N) = diimine and X = halide or an O, N, P or S-donor ancillary oxygen can generate reactive oxygen species (such as 1O2) that can lead to\nligand, have attracted great attention in recent years for their versatile cell death [14]. Others may exhibit photo-cytotoxic properties by releasing\napplications as catalysts [1,2], bio-imaging probes and potential drugs for toxic CO molecules upon irradiation [15], especially fac-[Re(CO)3(N,N)\ncancer treatment [3\u20137]. Such Re(I) complexes are generally inert with (PR3)]+ complexes where the ancillary phosphine group has a strong trans-\nslow ligand exchange rate due to the d6 low-spin electron configuration, directing influence [16,17].\nand are stable in a cellular environment [8,9]. Their properties can be Thus far, structures and properties of a few fac-[Re(CO)3(N,N)X]+/0/\u2212\nfinely tuned by changing the nature of the diimine and ancillary ligands complexes with axial S-donor ligands have been investigated [18\u201329],\n[10], affecting their level of cytotoxicity and ability to target different but not for a Se-donor ligand. Previous results from our group have shown\ncellular organelles [11\u201313]. Monitoring emissions from their long-lived how replacement of an aqua ligand with a negatively charged cysteinate\n3\n MLCT excited states (triplet state metal-to-ligand charge transfer) al\u00ad (a thiolate) or thiosulfate (S2O2\u2212\n 3 ) group could reduce the cytotoxicity of\nlows probing their cellular localization using confocal spectroscopy. The the fac-[Re(CO)3(bpy)(H2O)]+ complex by converting it to a neutral or\nquantum yield of such emissions can be tuned by selecting the diimine and negatively charged species [27,28]. The primary goal of this study was to\nancillary ligands [3]. The unique photophysical properties of some fac- compare the effect of neutral ancillary thione and selone ligands on the\n[Re(CO)3(N,N)X]+/0 complexes make them excellent candidates as cytotoxic properties of such complexes compared with the corresponding\n\n\n Abbreviations: MMI, Methimazole (2-mercapto-1-methylimidazole); MSeI, 1-methylimidazole-2-selone; bpy, 2,2\u2032 -bipyridine; phen, 1,10-phenanthroline; dmphen,\n2,9-dimethyl-1,10-phenanthroline; H2Cys, cysteine; HSQC, Heteronuclear single quantum coherence; TD-DFT, time-dependent density functional theory; DMEM,\nDulbecco\u2019s Modified Eagles Medium; PBS, Phosphate buffered saline; IC50, Half-maximal inhibitory concentration.\n * Corresponding author.\n E-mail address: faridehj@ucalgary.ca (F. Jalilehvand).\n\nhttps://doi.org/10.1016/j.jinorgbio.2022.112092\nReceived 28 September 2022; Received in revised form 24 November 2022; Accepted 2 December 2022\nAvailable online 5 December 2022\n0162-0134/\u00a9 2022 Elsevier Inc. All rights reserved.\n\fF. Jalilehvand et al. Journal of Inorganic Biochemistry 240 (2023) 112092\n\n\nfac-[Re(CO)3(N,N\u2032 )(H2O)]+ complex [12,27]. For this purpose, we chose normal human embryonic kidney cell line HEK-293 T, to investigate\nas ligands methimazole (2-mercapto-1-methylimidazole; MMI), and its how selective these complexes are for cancer cells.\nselenium analogue 1-methylimidazole-2-selone (MSeI); see Scheme 1\n[30\u201332]. 2. Experimental section\n Methimazole is an antithyroid drug that prevents thyroid hormone\nsynthesis [33,34]. Earlier studies have shown that thyroid hormones can 2.1. Materials\npromote tumor growth: \u201chypothyroidism inhibits tumor growth, while\nhyperthyroidism produces an opposite effect\u201d [35]. The idea behind Re(CO)5Cl, 2,2\u2032 -bipyridine, 1,10-phenantroline, 2,9-dimethyl-1,10-\nchoosing MMI as ligand was that in case its rhenium complexes go phenanthroline, Ag(CF3SO3), methimazole, 1-methylimidazole, n-\nthrough potential hydrolysis, the resulting species could have dual ef\u00ad butyllithium (1.6 M in hexane), selenium and NaBH4 were purchased\nfects: the hydrated rhenium complexes would still be cytotoxic [12], from Sigma-Aldrich and used without further purification. Toluene and\nwhile the free MMI ligands could reduce tumor growth by lowering the tetrahydrofuran (THF) were dried over sodium and benzophenone, and\nlevel of thyroid hormones. Free MSeI ligands may act as an antioxidant, then stored over 4 \u00c5 molecular sieves. Oxygen-free water was prepared\nsaving cells from oxidative damage [31]. The cytotoxicity and inhibitory by boiling distilled water and bubbling argon through it when cooling to\neffects of a water soluble Re(I) tricarbonyl complex with a diselenoether room temperature to remove dissolved O2. The starting materials fac-\nligand have been correlated to a significant decrease in the reactive [Re(CO)3(N,N\u2032 )Cl] (N,N\u2032 = bpy, phen, dmphen) [41], and the triflate\noxygen species produced by the cancer cells [36], as well as binding to salts of the aqua complexes fac-[Re(CO)3(bpy)(H2O)]+ (7; Re-bpy-\nDNA bases [37]. Aqua), fac-[Re(CO)3(phen)(H2O)]+ (8; Re-phen-Aqua) and fac-[Re\n The imidazoline-2-chalcogenone ligands are generally good \u03c3-donors (CO)3(dmphen)(H2O)]+ (9; Re-dmphen-Aqua) were prepared accord\u00ad\nand weak \u03c0-acceptors [38]. Methimazole is predominantly present in its ing to the previously published procedures [12], and characterized by\nstable thione form in the solid state and neutral aqueous solution, while measuring their unit cell dimensions and by NMR spectroscopy. A\nfor MSeI oxidation of the tautomeric selenol to diselenide (Scheme 1) in calibrated VWR Symphony SB70P pH meter was used for pH\nthe presence of air slowly decreases the initial selone concentration in measurements.\nsolution [31]. In the reported structures of multinuclear rhenium(I)\ncarbonyl complexes with methimazole, this bi-functional ligand forms a\nbridge between the Re(CO)+ 3 units [39,40].\n 2.2. Cell culture\n Here, we report syntheses and structural characterizations of the\ntriflate salts of six fac-[Re(CO)3(N,N\u2032 )X]+ complexes (1\u20136 in Scheme 1; The triple negative breast cancer cell line MDA-MB-231 and the\nX = MMI or MSeI; N,N\u2032 = bpy, phen or dmphen), and compare their human embryonic kidney cell line HEK-293 T were obtained from the\nstructures and in vitro cytotoxic effects on the human breast cancer cell American Type Culture Collection (ATCC), with frozen aliquots used\nline MDA-MB-231 with those reported for the corresponding aqua and within six months post thawing, and cultured with Dulbecco\u2019s Modified\nphosphine compounds (X = H2O, PR3). We also report their effect on the Eagle\u2019s Medium (DMEM; Invitrogen/Gibco), which was supplemented\n with heat-inactivated fetal bovine serum (10% v/v; Millipore Sigma),\n\n\n\n\nScheme 1. Top) Structures of methimazole (MMI) and its selenium analogue (MSeI) (left); selone \u2013 selenol tautomerism for MSeI (middle), and its oxidation product,\ndiselenide (right). Below) Structure of fac-[Re(CO)3(N,N\u2032 )X](CF3SO3) compounds prepared in this study.\n\n 2\n\fF. Jalilehvand et al. Journal of Inorganic Biochemistry 240 (2023) 112092\n\n\npenicillin (100 units/mL; Invitrogen/Gibco), streptomycin (100 \u03bcg/mL; 0.5 mmol) was mixed with Ag(OTf) (0.5 mmol) in 40 mL THF. The\nInvitrogen/Gibco) and L-glutamine (2 mM; Invitrogen). Cells were mixture was refluxed for 3 h in darkness, and then filtered to remove the\nincubated in a humidified incubator at 37 \u25e6 C with 5% CO2 and were sub- AgCl precipitate. The methimazole complexes 3 and 5 were obtained by\ncultured every 3\u20134 days for maintenance. adding solid MMI (0.5 mmol) to the filtrate, refluxing the mixture for 24\n h. For syntheses of the selenium analogues 4 and 6, the filtrate was\n2.3. Syntheses degassed using a Schlenk line, then adding a freshly prepared MSeI so\u00ad\n lution (0.5 mmol in 5 mL degoxygenated THF) and refluxing the mixture\n2.3.1. Synthesis of 2,2\u2032 -diselenobis(1-methylimidazole) for 24 h under argon.\n The diselenide (Scheme 1) and the selone ligand (MSeI) were pre\u00ad After removing the solvent (THF) through rotary evaporation, the\npared by a slight modification of a previously reported synthetic pro\u00ad remaining solid was dissolved (sometimes using sonication) in 6\u201310 mL\ncedure [31]. 1-Methylimidazole (12.18 mmol) was added to 100 mL of of a solvent to form crystals: MeOH for 2, EtOH for 4, and water: acetone\nfreshly prepared dry deoxygenated THF under argon atmosphere. The (1:1) mixture for 3, 5 and 6. Depending on the solvent, two crystalline\nsolution was cooled to \u2212 78 \u25e6 C in a dry-ice bath (acetone added) for 15 polymorphs of 1 were formed: 1a in water: acetone (1:1) mixture, and\nmin. Cooled n-butyllithium (7.6 mL, 1.6 M in hexane) was added and the 1b in water. Yellow crystals, which formed through slow evaporation of\nresulting pale yellow solution was stirred at \u2212 78 \u25e6 C for 30 min. After the solvent at room temperature, were filtered, washed with a small\nremoving the reaction flask from the dry-ice bath, the mixture was left amount of cold distilled water and then dried under vacuum.\nstirring at room temperature for 2 h. This solution was transferred with a fac-[Re(CO)3(bpy)(MMI)](CF3SO3) (1; Re-bpy-MMI). Elemental\nsyringe to another flask (purged with argon) containing selenium anal. Calcd for [Re(CO)3(C10H8N2)(C4H6N2S)](CF3SO3),\n(18.24 mmol) and stirred for another 12 h. The reaction mixture was (ReC18H14N4O6S2F3): %C 31.35, %H 2.05, %N 8.12; Found: %C 31.34,\nthen quenched with 20 mL cold deoxygenated water, and neutralized %H 2.08, %N 7.99. Yield 74%. 1H NMR (600 MHz, MeOD-d4): \u03b4H (ppm)\n(pH 6.7) by adding 1.0 mL concentrated HCl (12 N). This process led to = 9.06 (d, J = 4.8 Hz, 2H), 8.58 (d, J = 8.4 Hz, 2H), 8.30 (td, J = 7.8, 1.2\nthe formation of an orange organic layer on the top and an aqueous layer Hz, 2H), 7.73 (td, J = 6.6, 1.2 Hz, 2H), 7.14 (d, J = 1.8 Hz, 1H), 6.96 (d,\nwith unreacted selenium on the bottom. After decanting the organic J = 1.8 Hz, 1H), 3.35 (s, 3H). 13C NMR (151 MHz, MeOD-d4): \u03b4C (ppm)\nlayer, the aqueous layer was filtered to remove unreacted black solid = 198.0 (C11, C12), 190.1 (C13), 156.9 (C1, C1\u2032 ), 154.8 (C3, C3\u2032 ), 152.6\nselenium. Using a separatory funnel, the remaining product in the (C7), 141.6 (C5, C5\u2032 ), 129.3 (C4, C4\u2032 ), 125.5 (C6, C6\u2032 ), 123.9 (C8), 118.7\naqueous layer was extracted through shaking with two portions of 20 mL (C9), 35.1 (C10). IR (cm\u2212 1): \u1e7dC\u2261O = 2026, 1921, 1905.\nchloroform. All organic phases were combined, dried with anhydrous fac-[Re(CO)3(bpy)(MSeI)](CF3SO3) (2; Re-bpy-MSeI). Elemental\nNa2SO4 (~ 30 mg) and filtered. The clear orange solution was rotary anal. Calcd for [Re(CO)3(C10H8N2)(C4H6N2Se)](CF3SO3),\nevaporated to dryness at 40 \u25e6 C to afford the dark orange diselenide solid, (ReC18H14N4O6SeSF3): %C 29.35, %H 1.92, %N 7.61; Found: %C 29.30,\nwhich was purified by dissolving in hot chloroform and placed in the %H 1.78, %N 7.60. Yield 30%. 1H NMR (600 MHz, MeOD-d4): \u03b4H (ppm)\nfridge to crystallize. Yield 40%. 1H NMR (600 MHz, CDCl3): \u03b4H (ppm) = = 9.08 (d, J = 6.0 Hz, 2H), 8.53 (d, J = 8.4 Hz, 2H), 8.27 (td, J = 8.4, 1.8\n7.14 (d, J = 1.1 Hz, 2H), 7.03 (d, J = 1.1 Hz, 2H), 3.59 (s, 6H). 13C NMR Hz, 2H), 7.70 (td, J = 6.6, 1.2 Hz, 2H), 7.22 (d, J = 2.4 Hz, 1H), 7.02 (d,\n(600 MHz, CDCl3): \u03b4C (ppm) = 133.6, 131.0, 124.7, 35.4 [42]. J = 2.4 Hz, 1H), 3.36 (s, 3H). 13C NMR (151 MHz, MeOD-d4): \u03b4C (ppm)\n = 198.1 (C11, C12), 190.0 (C13), 156.7 (C1, C1\u2032 ), 154.8 (C3, C3\u2032 ), 141.3\n2.3.2. Synthesis of 1-methylimidazole-2-selone (MSeI) (C5, C5\u2032 ), 140.1 (C7), 129.2 (C4, C4\u2032 ), 125.4 (C6, C6\u2032 ), 124.9 (C8), 120.5\n To reduce the diselenide to selone, the above solid (4.72 mmol) was (C9), 36.7 (C10). IR (cm\u2212 1): \u1e7dC\u2261O = 2022, 1920, 1901.\nadded to 100 mL water, forming a yellow-orange cloudy mixture, to fac-[Re(CO)3(phen)(MMI)](CF3SO3) (3; Re-phen-MMI). Elemental\nwhich solid NaBH4 (11.90 mmol) was added. After stirring the reaction anal. Calcd for [Re(CO)3(C12H8N2)(C4H6N2S)](CF3SO3),\nmixture at room temperature over night, all diselenide dissolved. (ReC20H14N4O6S2F3): %C, 33.66; %H, 1.98; %N, 7.85; Found: %C 33.83;\nDichloromethane (20 mL) was added to the reaction flask and after %H, 1.96; %N, 7.90. Yield 93%. 1H NMR (600 MHz, MeOD-d4): \u03b4H\nstirring, the mixture was placed in a separatory funnel to separate the (ppm) = 9.45 (dd, J = 5.1, 1.4 Hz, 2H), 8.89 (dd, J = 8.3, 1.4 Hz, 2H),\norganic layer. The remaining product in the top aqueous layer was 8.24 (s, 2H), 8.06 (dd, J = 8.2, 5.1 Hz, 2H), 6.88 (d, J = 2.2 Hz, 1H), 6.71\nfurther extracted with two 10 mL portions of dichloromethane. The (d, J = 2.2 Hz, 1H), 3.10 (s, 3H). 13C NMR (151 MHz, MeOD-d4): \u03b4C\ndichloromethane extracts were combined, dried with anhydrous (ppm) = 197.9 (C11, C12), 190.1 (C13), 155.2 (C3, C3\u2032 ), 152.0 (C7),\nNa2SO4, and evaporated to dryness at room temperature using a rotary 147.6 (C1, C1\u2032 ), 140.7 (C5, C5\u2032 ), 132.6 (6, 6\u2032 ), 129.4 (C15, C15\u2032 ), 127.9\nevaporator. The resulting bright creamy colored solid, 1-methylimida\u00ad (C4, C4\u2032 ), 123.5 (C8), 118.2 (C9), 34.8 (C10). IR (cm\u2212 1): \u1e7dC\u2261O = 2024,\nzole-2-selone (MSeI), was characterized by NMR spectroscopy and 1923, 1910.\nstored in a glovebox to prevent diselenide formation. Yield 20%. 1H fac-[Re(CO)3(phen)(MSeI)](CF3SO3) (4; Re-phen-MSeI). Elemental\nNMR (600 MHz, CDCl3): \u03b4H (ppm) = 11.88 (br), 6.86 (d, J = 2.2 Hz, 1H), anal. Calcd for [Re(CO)3(C12H8N2)(C4H6N2Se)](CF3SO3),\n6.82 (d, J = 2.2 Hz, 1H), 3.69 (s, 3H). 13C NMR (600 MHz, CDCl3): \u03b4C (ReC20H14N4O6SeSF3): %C, 31.58; %H, 1.86; %N, 7.37%; Found: %C\n(ppm) = 152.1, 120.8, 116.5, 36.4 [42]. NMR spectra were also 33.44; %H, 1.80; %N, 7.37. Yield: 39%. 1H NMR (600 MHz, MeOD-d4):\nmeasured in MeOD-d4 (Fig. S4) for comparison with those of complexes \u03b4H (ppm) = 9.46 (dd, J = 5.1, 1.4 Hz, 2H), 8.86 (dd, J = 8.2, 1.3 Hz, 2H),\n1\u20136. 8.21 (s, 2H), 8.04 (dd, J = 8.2, 5.1 Hz, 2H), 6.90 (d, J = 2.4 Hz, 1H), 6.72\n (d, J = 2.4 Hz, 1H), 3.07 (s, 3H). 13C NMR (151 MHz, MeOD-d4): \u03b4C\n2.4. General synthetic procedure for complexes 1\u20136 (ppm) = 198.0 (C11, C12), 190.1 (C13), 155.3 (C3, C3\u2032 ), 147.3 (C1,\n C1\u2032 ), 140.4 (C5, C5\u2032 ), 139.5 (C7), 132.5 (C6, C6\u2032 ), 129.4 (C15, C15\u2032 ),\n Complex 1 was prepared by adding methimazole (MMI; 0.18 mmol) 127.8 (C4, C4\u2032 ), 124.6 (C8), 119.9 (C9), 36.3 (C10). IR (cm\u2212 1): \u1e7dC\u2261O =\nto a solution of fac-[Re(CO)3(bpy)(H2O)](CF3SO3) (0.17 mmol) in 20 mL 2020, 1908.\nTHF, refluxing the solution for 24 h. The same product was obtained in fac-[Re(CO)3(dmphen)(MMI)](CF3SO3) (5; Re-dmphen-MMI).\nsimilar yield, when the experiment was carried out at room temperature, Elemental anal. Calcd for [Re(CO)3(C14H12N2)(C4H6N2S)](CF3SO3),\nusing water as solvent. For preparing complex 2, a solution of freshly (ReC22H18N4O6S2F3): %C, 35.62; %H, 2.45; %N, 7.55; Found: %C 35.47;\nprepared 1-methylimidazole-2-selone (MSeI; 0.16 mmol) in 5 mL %H, 2.42; %N, 7.74. Yield 97%. 1H NMR (600 MHz, MeOD-d4): \u03b4H\ndeoxygenated THF was added to a solution of fac-[Re(CO)3(bpy)(H2O)] (ppm) = 8.66 (d, J = 8.3 Hz, 2H), 8.08 (s, 2H), 8.02 (d, J = 8.3 Hz, 2H),\n(CF3SO3) (0.17 mmol in 15 mL deoxygenated THF) and refluxed for 24 h 6.96 (d, J = 2.2 Hz, 1H), 6.85 (d, J = 2.2 Hz, 1H), 3.31 (s, 6H), 3.05 (s,\nunder argon atmosphere. 3H). 13C NMR (151 MHz, MeOD-d4): \u03b4C (ppm) = 197.8 (C11, C12),\n To prepare complexes 3\u20136, Re(CO)3(N,N\u2032 )Cl (N,N\u2032 = phen, dmphen; 189.9 (C13), 165.8 (C3, C3\u2032 ), 152.1 (C7), 148.7 (C1, C1\u2032 ), 140.9 (C5,\n\n 3\n\fF. Jalilehvand et al. Journal of Inorganic Biochemistry 240 (2023) 112092\n\n\nC5\u2032 ), 130.9 (C6, C6\u2032 ), 128.4 (C15, C15\u2032 ), 128.2 (C4, C4\u2032 ), 123.8 (C8), complexes 1 and 2 in DMEM (350 and 290 \u03bcM, respectively, for MDA-\n118.6 (C9), 34.8 (C10), 31.8 (C16). IR (cm\u2212 1): \u1e7dC\u2261O = 2022, 1903. MB-231 cells and 200 \u03bcM solutions containing 2% MeOH for HEK-\n fac-[Re(CO)3(dmphen)(MSeI)](CF3SO3) (6; Re-dmphen-MSeI). 293 T cells), 200 \u03bcM solutions of Re-phen complexes 3, 4 and 8 in DMEM\nElemental anal. Calcd for [Re(CO)3(C14H12N2)(C4H6N2Se)](CF3SO3), containing 2% MeOH, and Re-dmphen complexes 5, 6 (100 \u03bcM) and 9\n(ReC22H18N4O6SeSF3): %C, 33.51; %H, 2.30; %N, 7.10; Found: %C (60 \u03bcM) in DMEM with 3% MeOH. Higher concentrations of 9 turned\n33.86; %H, 2.37; %N, 7.16. Yield 83%. 1H NMR (600 MHz, MeOD-d4): turbid after an hour. In each case, appropriate amounts of complexes\n\u03b4H (ppm) = 8.63 (d, J = 8.3 Hz, 2H), 8.05 (s, 2H), 8.00 (d, J = 8.3 Hz, 3\u20136, 8 and 9 were first dissolved in 2.0 or 3.0 mL MeOH in a 100 mL\n2H), 6.98 (d, J = 2.1 Hz, 1H), 6.85 (d, J = 2.1 Hz, 1H), 3.31 (s, 6H), 3.07 volumetric flask, and then their volume was adjusted using the cell\n(s, 3H). 13C NMR (151 MHz, MeOD-d4): \u03b4C (ppm) = 198.0 (C11, C12), culture media. Stepwise dilution of the stock solutions using cell culture\n189.6 (C13), 165.9 (C3, C3\u2032 ), 148.7 (C1, C1\u2032 ), 141.5 (C7), 140.7 (C5, media (with 2% or 3% MeOH) led to a series of solutions with different\nC5\u2032 ), 130.8 (C6, C6\u2032 ), 128.4 (C15, C15\u2032 ), 128.2 (C4, C4\u2032 ), 124.8 (C8), concentrations. The procedure was repeated for all complexes 1\u20139\n120.3 (C9), 36.4 (C10), 32.0 (C16). IR (cm\u2212 1): \u1e7dC\u2261O = 2018, 1884. (containing 2\u20133% MeOH) and cisplatin prior to treating HEK-293 T cells.\n MDA-MB-231 breast cancer cells were seeded in black-walled clear-\n2.5. Physical measurements and methods bottom 96-well tissue culture plates at a density of 7500 cells/well, in a\n final volume of 100 \u03bcL of complete cell culture media, and cultured for\n2.5.1. Single-crystal X-ray diffraction ~36\u201348 h. Then the media was replaced with 100 \u03bcL of a freshly pre\u00ad\n Yellow single-crystals of 2 were obtained by slow evaporation of its pared diluted sample containing a drug (1\u20136, 8 or 9) in varying con\u00ad\nconcentrated solution in MeOH, and those of 1a, 3, 5 and 6 were crys\u00ad centrations in complete cell culture media. DMEM with 2% MeOH was\ntallized in water: acetone (1:1) mixture. Using water as solvent led to used as the vehicle for the Re-phen complexes 3, 4, 8, and DMEM with\nformation of single crystals of 1b. Crystals of 4 were not suitable for 3% MeOH for Re-dmphen complexes 5, 6 and 9. After 48 h incubation,\ncrystallography. the treatment was removed, cells were washed twice with 100 \u03bcL\n A suitable crystal was selected of each compound and diffraction phosphate buffered saline (PBS) and incubated with 100 \u03bcL of 10% v/v\ndata were obtained by means of a Bruker APEX-II CCD diffractometer at solution of alamarBlue reagent (Life Technologies Corporation) in\n173(2) K. Using Olex2 [43], the structures were solved with the ShelXT complete cell culture media; the plates were incubated for 2.5 h. The\n[44] structure solution program using Intrinsic Phasing and refined with fluorescence emission at 600 nm after excitation at 570 nm was\nthe ShelXL [45] refinement package using Least Squares minimisation. measured in a Spectramax M4 Microplate Reader. The percent control\n survival was calculated as (F/C) * 100, where F = fluorescence intensity\n2.5.2. NMR spectroscopy of the wells of interest, and C = average fluorescence intensity of the\n 1\n H, 13C and HSQC 2D NMR measurements were carried out at room wells containing cells incubated with complete cell culture media. The\ntemperature using a Bruker Avance III 600 MHz spectrometer. 1H NMR graphs were created using Graph Pad Prism software (version 9.3.0). In\nspectra of pure ligands (MMI and MSeI) in CDCl3 and those of rhenium order to calculate the half-inhibitory concentration (IC50), the percent\ncompounds in MeOD-d4 were collected by co-adding 32 scans and control survival vs logarithm of drug concentration graphs was adjusted\ninternally referenced using solvent residual signals at 7.26 and 3.31 to a logarithmic curve. The percent viability data are the mean of three\nppm, respectively [46,47]. 1H NMR spectra of 1\u20132 were also measured (for 1 and 2) or six (for 3\u20136, 8, 9) experimental replicates per concen\u00ad\nin 90%H2O (+ 10% MeOD-d4 used as internal reference) over a period of tration, and three independent experiments.\n48 h, each time collecting 32 scans using the zgesgp pulse sequence for The above procedure was repeated for the HEK-293 T cells: DMEM\nwater suppression via application of a shaped pulse. To compare the 1H with 2% MeOH was used as the vehicle for the Re-bpy and Re-phen\nNMR chemical shifts, the spectra of MMI and MSeI were also measured complexes (1\u20134, 7, 8), and DMEM with 3% MeOH for Re-dmphen\nin MeOD-d4. 13C NMR measurements were carried out at 151 MHz at complexes (5, 6, 9). For cisplatin, DMEM was added as the vehicle.\nroom temperature, using zgpg30 (except for 6) or UDEFT (for 6) pulse The cells were incubated with each drug for 48 h. The cell viability (%)\nsequence and broadband proton decoupling, a 240 ppm sweep width, data are representative of three independent experiments, each with six\n0.5 s delay between scans (3.0 s for 6) and 65 K data points, co-adding replicates.\n2000 scans for pure ligands MMI and MSeI in CDCl3 (and also in MeOD-\nd4 for comparison), and Re(I) complexes 1\u20136, and internally referenced 3. Results and discussion\nusing the CD3Cl and MeOD-d4 signals at 77.16 and 49.15 ppm, respec\u00ad\ntively [46]. The HSQC 2D NMR for 1\u20135 were obtained by co-adding 4\u20138 Reactions of diimine Re(I) tricarbonyl compounds, fac-[Re(CO)3(N,\nscans. N\u2032 )X](CF3SO3), (N,N\u2032 = bpy, phen, dmphen; X = H2O or THF), with\n methimazole and its selenium analogue in THF solution led to a series of\n2.5.3. FT-IR spectroscopy air-stable Re(I) complexes coordinated to these imidazoline-2-thione/\n IR spectra were measured using an Agilent Cary 630 FT-IR with a selone ligands, which were characterized by X-ray crystallography,\ndiamond ATR accessory, averaging 8 scans for each sample. elemental analysis, multinuclear (1H, 13C) and 2D NMR, UV\u2013vis and IR\n spectroscopic techniques. Scheme 2 displays the synthetic procedure for\n2.5.4. UV\u2013vis spectroscopy the water soluble compound fac-[Re(bpy)(CO)3(MSeI)](CF3SO3) (2),\n Electronic absorption spectra were obtained at room temperature which was crystallized from its methanol solution.\nwith a Cary 300 UV\u2013vis double-beam spectrophotometer using a 1 cm\npath-length quartz cuvette, with distilled water or 2% MeOH (10% 3.1. X-ray crystallography\nMeOH for 6) as reference. Stock solutions (200 \u03bcM) of the rhenium (I)\nbipyridine complexes (1, 2, 7) were prepared in distilled water and the Crystallization of the water soluble methimazole compound, fac-[Re\nothers in 2% MeOH (complex 6 in 10% MeOH) due to their limited (bpy)(CO)3(MMI)](CF3SO3) (Re-bpy-MMI; 1), led depending on the\nsolubility in water. Each sample was then further diluted using distilled solvent used (see the Experimental Section), to two polymorphs 1a and\nwater (or 2% or 10% MeOH) to 5.0 \u00d7 10\u2212 5 M, for which 3\u20135 scans were 1b. Evidently, their energy difference must be small, with the MMI ring\ncollected and averaged. stacked nearly above the bipyridine ligand in 1a, but in 1b adopting the\n opposite direction away from bipyridine closer to the equatorial\n2.5.5. Cell viability carbonyl ligands (Fig. 1). Crystal data, structural refinements, as well as\n To determine the cytotoxicity of 1\u20136, 8 and 9, their stock solutions selected bond distances and angles for 1a, 1b, fac-[Re(CO)3(bpy)(MSeI)]\nwere prepared in complete cell culture media using DMEM: Re-bpy (CF3SO3) (2; Re-bpy-MSeI), fac-[Re(CO)3(phen)(MMI)](CF3SO3) (3;\n\n 4\n\fF. Jalilehvand et al. Journal of Inorganic Biochemistry 240 (2023) 112092\n\n\n\n\nScheme 2. Synthetic procedure for the fac-[Re(CO)3(bpy)(MSeI)](CF3SO3) compound (2). The numbers in red refer to the carbon atoms associated with its crystal\nstructure and the 13C NMR signals described in the \u201cExperimental Section\u201d.\n\n\n\n\nFig. 1. Two polymorphs of fac-[Re(bpy)(CO)3(MMI)](CF3SO3): 1a crystallized from water: acetone (1:1), 1b from water. Only one of the two ion-pairs in the\nasymmetric unit of 1b is shown here. Thermal ellipsoids are shown at 50% probability level.\n\n\nRe-phen-MMI) and fac-[Re(CO)3(dmphen)(MSeI)](CF3SO3) (6; Re- In these structures, methimazole (MMI) and its selenium analogue\ndmphen-MSeI) are reported in Tables S1 and S2, with crystal structures (MSeI) appear in their thione and selone forms, respectively. The C7\u2013S\nof 2, 3 and 6 displayed in Fig. 2. The crystal structure of fac-[Re bond distances in the coordinated MMI in 1a, 1b and 3 are all longer\n(CO)3(dmphen)(MMI)](CF3SO3) (5; Re-dmphen-MMI) was disordered, (Table S2) than the C\u2013S distances in the pure MMI ligand, 1.682(2) and\nwith two slightly twisted orientations for the Re(I) complex (Fig. S1). 1.686(2) \u00c5 [48]. Similar elongation is observed for the C7\u2013Se distance\n The crystal structures of 1a and 2 are isomorphous with the same of the Re(I) bound selone group in 2 and 6 relative to the corresponding\nspace group. In all other crystal structures, the orientations of the imi\u00ad C\u2013Se distance in the pure MSeI ligand, 1.849(3) \u00c5 [42]. This observa\u00ad\ndazoline rings are different. Still one of the nitrogen atoms in the imi\u00ad tion is probably due to \u03c0-back donation from the filled Re(I) t2g orbitals\ndazoline ring (N1) forms a rather strong hydrogen-bond to the triflate to \u03c0* (C=S/Se), making the bond somewhat weaker and longer.\nions with N1\u2013H\u2026.O about 2.8\u20132.9 \u00c5. Such hydrogen bond ability The Re\u2013COaxial bond distances in the MMI/MSeI complexes 1a, 1b\nwould promote solubility of the complexes in the aqueous solution. and 2 (Re\u2013C axial = 1.91\u20131.92 \u00c5, Table S2) are longer for the CO ligands\n\n\n 5\n\fF. Jalilehvand et al. Journal of Inorganic Biochemistry 240 (2023) 112092\n\n\n\n\nFig. 2. Crystal structures of fac-[Re(CO)3(bpy)(MSeI)](CF3SO3) (2), fac-[Re(CO)3(phen)(MMI)](CF3SO3) (3) and fac-[Re(CO)3(dmphen)(MSeI)](CF3SO3) (6).\nDisordered components have been removed for clarity.\n\n\ntrans to the thione/selone groups than that for the CO ligand trans to the with phosphine ligands, [Re(CO)3(bpy)(PR3)]+ [16], the average Re\u2013P\naqua ligand in the crystal structure of fac-[Re(CO)3(bpy)(H2O)] bonds (2.43\u20132.44 \u00c5) are about 0.1\u20130.2 \u00c5 shorter than the corresponding\n(CF3SO3) (7; Re\u2013C axial = 1.882(10) \u00c5) [49]. Similar elongation is Re\u2013S and Re\u2013Se distances in 1a/1b and 2, respectively. Furthermore,\nobserved when comparing the influence of aqua and MMI ligands on the the Re\u2013COaxial bonds (1.96 \u00c5) are slightly longer than those in 1a/1b\nRe\u2013COaxial distances in fac-[Re(CO)3(phen)(H2O)](CF3SO3) (8) and fac- and 2 (1.91\u20131.92 \u00c5), implying that the phosphine ligands have even\n[Re(CO)3(phen)(MMI)](CF3SO3) (3) with Re\u2013Caxial 1.898(7) \u00c5 and stronger trans-influence than MMI and MSeI. An increasing \u03c3-donor and\n1.923(2) \u00c5, respectively [49]. The elongation is consistent with the \u03c0-acceptor ability of the PR3 ligands with \u03c0-competition for the same\nstronger sigma bond formed between the soft Re(I) ion and the soft S/Se metal orbitals is consistent with a weaker, longer trans Re\u2013COaxial bond\ndonor atom in the MMI and MSeI ligands, than with the aqua ligand, [15].\nleading to stronger trans influence on the Re\u2013COaxial bonds.\n The Re\u2013S bond lengths in the Re-MMI complexes 1a, 1b and 3,\n 3.2. Vibrational spectroscopy\nwhich vary over a narrow range 2.516(1) ~ 2.545(2) \u00c5, and the Re\u2013Se\nbond distance of 2.650(1) \u00c5 in the Re-MSeI complexes 2 and 6 are\n The characteristic C \u2261 O vibrational stretching bands that occur in\ncomparable with the average Re\u2013S and Re\u2013Se distances 2.516(2) \u00c5\n the 2040\u20131890 cm\u2212 1 range for the Re(I) aqua complexes 7\u20139, generally\nand 2.643(3) in the [Re(CO)3{HB(SImMe)3}] and [Re(CO)3{HB\n appear at lower frequencies for the complexes 1a \u2013 6 (Fig. S2 and Table\n(SeImMes)3}] complexes, respectively, where {HB(SImMe)3} = tris(2-\n S3). Such shift indicates weaker C \u2261 O bonds, probably because of\nmercapto-1-methylimidazolyl)hydroborate and {HB(SeImMes)3} = tris\n increased \u03c0-back-donation from the electron-rich Re(I) ions bound to the\n(2-seleno-1-mesitylimidazolyl)hydroborate [50,51].\n thione/selone ligands (relative to H2O) to \u03c0* of the carbonyl group\n In the previously reported crystal structures for similar complexes\n [50,52].\n\n 6\n\fF. Jalilehvand et al. Journal of Inorganic Biochemistry 240 (2023) 112092\n\n\n3.3. NMR spectroscopy\n\n The 1H and 13C NMR signals for C8\u2013H and C9\u2013H in Re(I)-bound\nMMI and MSeI in 1 and 2 showed a slight downfield shift (\u0394\u03b4H < 0.2\nppm, \u0394\u03b4C \u2264 3 ppm) relative to those of the pure ligands (see Table S4,\nFigs. S3\u2013S6), since transfer of electron density from the coordinated\nMMI/ MSeI ligands to the Re(I) ion has a deshielding effect on both the H\nand C atoms. Similar relative 13C downfield shifts were observed for the\nligands\u2019 C8 and C9 atoms in the Re-phen and Re-dmphen complexes\n3\u20136. However, the C8\u2013H and C9\u2013H proton NMR resonances in the Re-\nphen complexes 3 and 4 were somewhat shielded relative to those of\npure MMI and MSeI ligands, which could be due to stacking of the MMI/\nMSeI ligands above the phen ring, as shown in the crystal structure of the\nRe-phen-MMI complex (3) in Fig. 2.\n The 13C NMR signal for the carbene C7 atom (C\u2013S/Se) of the pure\nligands MIM (\u03b4C = 161.6 ppm) and MSeI (\u03b4C = 152.3 ppm) showed\nsignificant upfield shift (\u0394\u03b4C 9\u201313 ppm) in the 13C NMR spectra of the Re\n(I) complexes 1\u20136; see Figs. S3\u2013S10 and Table S4. Such an upfield shift of\nthe 13C signal has been attributed to decreasing \u03c0-acceptance character\nof the carbene C atom upon coordination [53]. In free N-heterocyclic\ncarbenes (NHCs), promotion of an electron from the \u03c3(NHC lone pair) to\nthe p\u03c0 acceptor orbital on the carbene C atom contributes to the para\u00ad\nmagnetic shielding term, leading to a downfield shift of carbene \u03b4C [54].\nIn imidazoline-2-chalcogenones such as MSeI, the \u03c0 backdonation Se\n(4py) \u2192 Se-C(\u03c0*) that contributes to a paramagnetic shielding term is\ndecreased upon Se(4py) \u2192 metal coordination, resulting in an upfield\nshift of the carbene \u03b4C [55,56].\n\n3.4. Electronic absorption spectroscopy\n\n The UV\u2013vis absorption spectra of the Re(I) complexes 1\u20139 displayed\nin Fig. 3 show that the band at 345 nm for the Re-bpy-Aqua complex (7)\nshifts to higher wavelengths (red-shift) to 362 and 367 nm for Re-bpy-\nMMI (1) and Re-bpy-MSeI (2), respectively. These electronic transi\u00ad\ntions are attributed to a metal-to-ligand charge transfer (MLCT) d(Re) \u2192\n\u03c0*(bpy); see the Computational Studies in the Supplementary Data. Also,\nthe intensity of the bands at 245 and ~ 300 nm increases noticeably for 1\nand 2, relative to 7. The spectra of Re-MMI complexes 3 and 5 show two\ndistinct features in the 255\u2013275 nm range.\n These complexes were stable in aqueous (or 2% MeOH) solutions\nwhen irradiated with UV-A light (\u03bb = 365 nm) for 2 h (Fig. S12),\notherwise observable changes in the UV\u2013vis spectra would be expected\nas a result of changes in the Re(I) coordination geometry [16]. The\nminor changes observed in the UV\u2013vis spectra in Fig. S12 are due to\nphoto-bleaching.\n\n3.5. Ligand exchange in aqueous media\n\n To check the stability of the complexes, and the possibility of MMI/\nMSeI ligand exchange with water molecules in aqueous media, 1H NMR\nspectra of the water soluble Re-bpy-MMI (1) and Re-bpy-MSeI (2)\ncomplexes were measured at different time intervals over a 48 h period\nin 90% H2O (+ 10% MeOD-d4 used as internal reference). As shown in\nFig. 4, the Re(I) methimazole complex (1) is rather stable in aqueous\nsolution with ~18% of the complex being hydrolyzed after 24 h and ~\n27% after 48 h (based on the relative peak integrals in the 9.1\u20139.2 ppm Fig. 3. UV\u2013vis absorption spectra of air-equilibrated aqueous media (5.0 \u00d7\nregion); peaks related to the hydrolyzed species are marked with (*). 10\u2212 5 M) of fac-[Re(N,N\u2032 )(CO)3X](CF3SO3) compounds: (top) N,N\u2032 = bpy, X =\nThe ligand exchange is much slower for the MSeI ligand in 2, as shown in MMI (1), MSeI (2), H2O (7); (middle) N,N\u2032 = phen, X = MMI (3), MSeI (4), H2O\nFig. S11, with only ~10% of the complex hydrolyzed after 24 h. Based (8); (below) N,N\u2032 = dmphen, X = MMI (5), MSeI (6), H2O (9). Common ab\u00ad\non these results, limited amount of free ligand from the hydrolysis sorption maxima are shown in black.\nprocess is released in the aqueous media at room temperature.\n human breast cancer cells (MDA-MB-231) and in the human embryonic\n3.6. Cytotoxicity kidney cells (HEK-293 T), checking the selectivity of these complexes\n towards cancerous vs. normal cells. The results are presented in Fig. 5,\n The effect of the Re(I) complexes 1\u20136 on cell viability was deter\u00ad S15 and Table 1.\nmined by testing varying concentrations of these complexes in the Complexes 1 and 2 with the MMI/MSeI ligands have significantly\n\n 7\n\fF. Jalilehvand et al. Journal of Inorganic Biochemistry 240 (2023) 112092\n\n\n\n\nFig. 4. 1H NMR spectra of fac-[Re(CO)3(bpy)(MMI)](CF3SO3) (1; Re-bpy-MMI) in (90% H2O + 10% MeOD-d4) over 48 h. Peaks shown with (*) are related to the\nhydrolysis products: the Re-bpy-Aqua (7) complex and the free MMI ligand.\n\n\n\n\nFig. 5. Cytotoxicity of the Re(I) complexes 1\u20139 in the human breast cancer cells (MDA-MB 231). Cells were incubated with each compound for 48 h. The error bars\nrepresent the standard deviation. The data were analyzed using a one-way ANOVA, followed by a Dunnett\u2019s Test; the asterisks represent significant differences in\ncomparison to the control group (no treatment), *: p < 0.05, **: p < 0.01. The data represent three independent experiments, each with three (for 1 and 2), six (for\n3\u20136, 8, 9) or nine (for 7 - from Ref [27]) experimental replicates.\n\n 8\n\fF. Jalilehvand et al. Journal of Inorganic Biochemistry 240 (2023) 112092\n\n\nhigher cytotoxicity towards MDA-MB-231 cells (Table 1) in comparison Table 1\nwith the two Re(I) complexes containing X = S-donor ligands that were IC50 values of the compounds in the human breast cancer cell line MDA-MB 231\npreviously studied in our group, i.e. the neutral cysteinate complex, fac- and the human embryonic kidney cell line HEK-293 T after 48 h treatmenta.\n[Re(CO)3(bpy)(HCys)], and the anionic fac-[Re(CO)3(bpy)(S2O3)]\u2212 Compound MDA-MB-231 IC50 (\u03bcM) HEK-293 T IC50 (\u03bcM)\n[27,28]. The reason is probably due to the cationic nature of these cisplatin 11 \u00b1 2b 23 \u00b1 1\nspecies and their higher cell membrane permeability that leads to higher fac-Re(CO)3(bpy)(HCys) > 100b\ncellular uptake through passive diffusion [57\u201359]. Na[fac-Re(CO)3(bpy)(S2O3)] > 100c\n Comparing the cytotoxicity of MMI vs. MSeI rhenium(I) complexes, Re-bpy-MMI (1) 55 \u00b1 2 72 \u00b1 2\n Re-bpy-MSeI (2) 55 \u00b1 3 80 \u00b1 2\nthe Re-MMI complexes 3 and 5 were somewhat more toxic with lower\n Re-bpy-Aqua (7) 26 \u00b1 3b 45 \u00b1 1\nIC50 relative to their selenium analogues 4 and 6, respectively, or with Re-phen-MMI (3) 35 \u00b1 1 35 \u00b1 1\nvery similar cytotoxicity (1 and 2 towards breast cancer cells). Of the Re-phen-MSeI (4) 45 \u00b1 1 38 \u00b1 1\nthree sets of diimine complexes tested in this study, the Re-dmphen Re-phen-Aqua (8) 19.0 \u00b1 0.7 31.0 \u00b1 0.8\ncomplexes (5, 6 and 9) displayed the highest toxicity. In each set, the Re-dmphen-MMI (5) 8.0 \u00b1 0.2 11.0 \u00b1 0.2\n Re-dmphen-MSeI (6) 14.0 \u00b1 0.4 15.0 \u00b1 0.4\naqua complexes fac-[Re(CO)3(N,N\u2032 )X]+ (X = H2O; 7\u20139) were generally Re-dmphen-Aqua (9) 6.0 \u00b1 0.1 20.0 \u00b1 0.4\nmore toxic towards the breast cancer cells than the corresponding X =\n a\nMMI/ MSeI complexes (1\u20136) with the lowest IC50 = 6.0 \u00b1 0.1 \u03bcM for fac- The values given as IC50 \u00b1 standard deviation represent three independent\n experiments, each with six replicates for the HEK-293 T cell line, and for the\n[Re(CO)3(dmphen)(H2O)]+ (9) (see Table 1). This value is comparable\n MDA-MB-231 cell line, each experiment with three (for 1 and 2), six (for 3\u20136, 8,\nto a range of reported IC50 values for this complex, tested in several cell\n 9) or nine (for cisplatin and 7) replicates.\nlines (other than MDA-MB 231), varying from 0.92 \u00b1 0.20 to 6.7 \u00b1 4.9 b\n Ref [27].\n(cell exposure time = 72 h) [12]. Remarkably, among the Re-dmphen c\n Ref [28].\ncomplexes, the Re-dmphen-Aqua (9) was the least toxic one towards\nHEK-293 T cells (IC50 = 20.0 \u00b1 0.4 \u03bcM), showing three times higher\n candidates as photo-activated anticancer agents.\nselectivity towards MDA-MB-231 breast cancer cells. The other Re-aqua\ncomplexes (7 and 8) as well as the Re-bpy complexes 1 and 2 were more\ntoxic and selective towards MDA-MB-231 than HEK-293 T cells, Crystallography data\nalthough to a lesser extent than 9. The Re-phen-MMI (3) and Re-phen-\nMSeI (4) complexes were found to be equally or more toxic towards CCDC 2201417\u20132201422 contain the supplementary crystallo\u00ad\nHEK-293 T human embryonic kidney cells, with Re-dmphen-MMI (5) graphic data for this paper. These data can be obtained free of charge via\nbeing the most toxic. www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_req\n The mechanism of action of these complexes is unknown. The ability uest@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallo\u00ad\nof 1 and 2 in generating 1O2 was tested using a direct detection method graphic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:\nas described earlier [27], giving negative results. It is unlikely that these +441,223 336,033.\nRe-MMI/MSeI complexes become activated through hydrolysis [60]; as\ndiscussed in Section 3.5, <10\u201320% of complexes 1 and 2 hydrolyzed Author statement\nover a 24 h period.\n Complexes 1\u20136 with a thione/ selone donor ligand seem to be more All authors contributed by performing the experiments and/or data\ntoxic (IC50 \u2264 55 \u03bcM for MDA-MB-231 cells) than phosphine complexes collection/ data analyses, discussed the results and commented on the\nfac-[Re(CO)3(N,N\u2032 )(PR3)]+ with similar diimine ligands [16]. However, manuscript. F.J. and V.B. wrote the manuscript with input from all other\nthese phosphine complexes exhibit photo-cytotoxicty, i.e. they have the authors.\nadvantage of having minimal toxicity in the dark (IC50 > 200 \u03bcM in HeLa\ncells), but become highly toxic upon irradiation with 365 nm light \u2013 an\nideal case for selectively targeting cancer cells. Note that irradiation of Declaration of Competing Interest\ncomplexes 1\u20135 with 365 nm light did not cause any changes in their\nUV\u2013vis. Spectra (see above). The authors declare that they have no known competing financial\n interests or personal relationships that could have appeared to influence\n4. Conclusion the work reported in this paper.\n\n Two series of diimine tricarbonyl rhenium(I) complexes with the soft Data availability\nand polarizable thione (methimazole; MMI) or selone (1-methyl\u00ad\nimidazole-2-selone; MSeI) ligands were reported for the first time: fac- Data will be made available on request.\n[Re(CO)3(N,N\u2032 )(MMI)]+ and fac-[Re(CO)3(N,N\u2032 )(MSeI)]+, where N,N\u2032\n= bpy, phen and dmphen. Their cytotoxicity on the human breast cancer Acknowledgements\n(MDA-MB-231) and the human embryonic kidney (HEK-293 T) cell lines\nwere determined in vitro. The highest toxicity was found for fac-[Re This work was financially supported by the Natural Sciences and\n(CO)3(dmphen)(MMI)]+ (5) with IC50 = 8.0 \u00b1 0.2 \u03bcM (for MDA-MB- Engineering Research Council of Canada (NSERC) funding reference\n231), similar to that of the corresponding aqua complex, fac-[Re numbers RGPIN 2016-04546 and 2022-02996 (FJ), Canada Foundation\n(CO)3(dmphen)(H2O)]+ with IC50 = 6.0 \u00b1 0.1 \u03bcM; the latter had three for Innovation (Grant no. 9479) and the Province of Alberta - Depart\u00ad\ntimes higher selectivity towards the cancer cells. Least toxic were the ment of Innovation and Science (FJ), University of Calgary SEED Grant\nwater soluble fac-[Re(CO)3(bpy)(MMI / MSeI)]+ complexes (1, 2; IC50 no. 1054307 (FJ), and the Alberta Cancer Foundation Grant no. 27246\n= 55 \u00b1 3 \u03bcM for the cancer cells and 72\u201380 \u03bcM for the normal cells). (CS). Theoretical calculations were performed using the computer re\u00ad\n These thione/ selone Re(I) complexes were significantly more cyto\u00ad sources provided by WestGrid (www.westgrid.ca) and Digital Research\ntoxic (IC50 \u2264 55 \u03bcM) than the corresponding fac-[Re(CO)3(N,N\u2032 )(PR3)]+ Alliance of Canada (alliancecan.ca). We are grateful to Professor Belinda\ncomplexes with a phosphine ligand that display little to no toxicity in the Heyne\u2019s group for testing the ability of 1 and 2 in generating 1O2. V.B.\ndark (IC50 > 200 \u03bcM in HeLa cells) [16]. However, unlike the phosphine acknowledges NSERC Undergraduate Student Research Award (USRA),\ncomplexes, they were stable in aqueous media and did not release a CO and is grateful to Mr. Miles Capper for providing a portion of the fac-[Re\nligand upon irradiation with 365 nm light, and are therefore not (CO)3(bpy)(H2O)](CF3SO3) complex (7) used for syntheses of 1 and 2.\n\n 9\n\fF. Jalilehvand et al. Journal of Inorganic Biochemistry 240 (2023) 112092\n\n\nAppendix A. Supplementary data [29] A. Go\u0301mez, G. Jara, E. Flores, T. Maldonado, F. Godoy, M. Mun\u0303oz-Osses, A. Vega,\n R. Mera, C. Silva, J. Pavez, New J. Chem. 44 (2020) 14171\u201314179.\n [30] G. Roy, G. Mugesh, Bioinorg. Chem. Appl. (2006) 1\u20139, 23214, https://www.\n Supplementary data to this article can be found online at https://doi. hindawi.com/journals/bca/2006/023214/.\norg/10.1016/j.jinorgbio.2022.112092. [31] G. Roy, G. Mugesh, J. Am. Chem. Soc. 127 (2005) 15207\u201315217.\n [32] K.P. Bhabak, G. Mugesh, Chem. Eur. J. 16 (2010) 1175\u20131185.\n [33] D.S. Cooper, N. Engl. J. Med. 352 (2005) 905\u2013917. https://www.nejm.org/doi/\nReferences full/10.1056/nejmra042972.\n [34] F. Isaia, M.C. Aragoni, M. Arca, F. Demartin, F.A. Devillanova, G. Floris, A. Garau,\n [1] K.A. Grice, C.P. Kubiak, in: M. Aresta, R. van Eldik (Eds.), Advances in Inorganic M.B. Hursthouse, V. Lippolis, R. Medda, F. Oppo, M. Pira, G. Verani, J. Med. Chem.\n Chemistry, Academic Press, 2014, pp. 163\u2013188. 51 (2008) 4050\u20134053.\n [2] J. Agarwal, E. Fujita, H.F. Schaefer, J.T. Muckerman, J. Am. Chem. Soc. 134 (2012) [35] E. Krashin, A. Piekie\u0142ko-Witkowska, M. Ellis, O. Ashur-Fabian, Front. Endocrinol.\n 5180\u20135186. 10 (2019), 1-23, 59, https://www.frontiersin.org/articles/10.3389/fendo.20\n [3] S. Hostachy, C. Policar, N. Delsuc, Coord. Chem. Rev. 351 (2017) 172\u2013188. 19.00059/full.\n [4] E.B. Bauer, A.A. Haase, R.M. Reich, D.C. Crans, F.E. K\u00fchn, Coord. Chem. Rev. 393 [36] P. Collery, V. Veena, A. Harikrishnan, D. Desmaele, Investig. New Drugs 37 (2019)\n (2019) 79\u2013117. 973\u2013983.\n [5] A. Leonidova, G. Gasser, ACS Chem. Biol. 9 (2014) 2180\u20132193. [37] P. Collery, A. Mohsen, A. Kermagoret, S. Corre, G. Bastian, A. Tomas, M. Wei,\n [6] K. Schindler, F. Zobi, Molecules 27 (2022), 1-25, 539, https://www.mdpi.com F. Santoni, N. Guerra, D. Desmae\u0308le, J. d\u2019Angelo, Investig. New Drugs 33 (2015)\n /1420-3049/27/2/539. 848\u2013860.\n [7] P. Collery, D. Desmaele, V. Vijaykumar, Curr. Pharm. Des. 25 (2019) 3306\u20133322. [38] H.-N. Zhang, W.-G. Jia, Q.-T. Xu, C.-C. Ji, Inorg. Chim. Acta 450 (2016) 315\u2013320.\n https://pubmed.ncbi.nlm.nih.gov/31475892/. [39] S. Ghosh, S.E. Kabir, S. Pervin, G.M.G. Hossain, D.T. Haworth, S.V. Lindeman, T.\n [8] C.C. Konkankit, J. Lovett, H.H. Harris, J.J. Wilson, Chem. Commun. 56 (2020) A. Siddiquee, D.W. Bennett, H.W. Roesky, Z. Anorg. Allgem. Chem. 635 (2009)\n 6515\u20136518. 76\u201387.\n [9] J.L. Wedding, H.H. Harris, C.A. Bader, S.E. Plush, R. Mak, M. Massi, D.A. Brooks, [40] S. Ghosh, S.E. Kabir, S. Pervin, A.K. Raha, G.M. Golzar Hossain, D.T. Haworth, S.\n B. Lai, S. Vogt, M.V. Werrett, Metallomics 9 (2017) 382\u2013390. https://pubs.rsc.org V. Lindeman, D.W. Bennett, T.A. Siddiquee, L. Salassa, H.W. Roesky, Dalton Trans.\n /en/content/articlelanding/2017/mt/c6mt00243a. (2009) 3510\u20133518.\n[10] K. Talukdar, S. Sinha Roy, E. Amatya, E.A. Sleeper, P. Le Magueres, J.W. Jurss, [41] J.M. Smieja, C.P. Kubiak, Inorg. Chem. 49 (2010) 9283\u20139289.\n Inorg. Chem. 59 (2020) 6087\u20136099. [42] V.K. Landry, M. Minoura, K. Pang, D. Buccella, B.V. Kelly, G. Parkin, J. Am. Chem.\n[11] R.-R. Ye, C.-P. Tan, M.-H. Chen, L. Hao, L.-N. Ji, Z.-W. Mao, Chem. Eur. J. 22 Soc. 128 (2006) 12490\u201312497.\n (2016) 7800\u20137809. [43] O.V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A. Howard, H. Puschmann, J. Appl.\n[12] K.M. Knopf, B.L. Murphy, S.N. MacMillan, J.M. Baskin, M.P. Barr, E. Boros, J. Crystallogr. 42 (2009) 339\u2013341. https://scripts.iucr.org/cgi-bin/paper?kk5042.\n J. Wilson, J. Am. Chem. Soc. 139 (2017) 14302\u201314314. [44] G.M. Sheldrick, Acta Crystallogr. A 71 (2015) 3\u20138. https://scripts.iucr.org/c\n[13] C.C. Konkankit, A.P. King, K.M. Knopf, T.L. Southard, J.J. Wilson, ACS Med. Chem. gi-bin/paper?sc5086.\n Lett. 10 (2019) 822\u2013827. [45] G.M. Sheldrick, Acta Crystallogr. C: Struc. Chem. 71 (2015) 3\u20138. https://scripts.iuc\n[14] L.C.-C. Lee, K.-K. Leung, K.K.-W. Lo, Dalton Trans. 46 (2017) 16357\u201316380. https: r.org/cgi-bin/paper?fa3356.\n //pubs.rsc.org/en/content/articlelanding/2017/dt/c7dt03465b. [46] G.R. Fulmer, A.J. Miller, N.H. Sherden, H.E. Gottlieb, A. Nudelman, B.M. Stoltz, J.\n[15] I. Chakraborty, J. Jimenez, W.M.C. Sameera, M. Kato, P.K. Mascharak, Inorg. E. Bercaw, K.I. Goldberg, Organometallics 29 (2010) 2176\u20132179.\n Chem. 56 (2017) 2863\u20132873. [47] https://www.chemicalbook.com/SpectrumEN_60-56-0_1HNMR.htm.\n[16] S.C. Marker, S.N. MacMillan, W.R. Zipfel, Z. Li, P.C. Ford, J.J. Wilson, Inorg. Chem. [48] G. Vampa, S. Benvenuti, F. Severi, L. Malmusi, L. Antolini, J. Heterocyclic Chem.\n 57 (2018) 1311\u20131331. 32 (1995) 227\u2013234.\n[17] K. Koike, N. Okoshi, H. Hori, K. Takeuchi, O. Ishitani, H. Tsubaki, I.P. Clark, M. [49] B. Salignac, P.V. Grundler, S. Cayemittes, U. Frey, R. Scopelliti, A.E. Merbach,\n W. George, F.P.A. Johnson, J.J. Turner, J. Am. Chem. Soc. 124 (2002) R. Hedinger, K. Hegetschweiler, R. Alberto, U. Prinz, Inorg. Chem. 42 (2003)\n 11448\u201311455. https://pubs.acs.org/doi/10.1021/ja017032m. 3516\u20133526. https://pubs.acs.org/doi/10.1021/ic0341744.\n[18] E. Hevia, J. Pe\u0301rez, L. Riera, V. Riera, I. del R\u00edo, S. Garc\u00eda-Granda, D. Miguel, Chem. [50] M. Minoura, V.K. Landry, J.G. Melnick, K. Pang, L. Marchio\u0300, G. Parkin, Chem.\n Eur. J. 8 (2002) 4510\u20134521. https://chemistry-europe.onlinelibrary.wiley. Commun. (2006) 3990\u20133992.\n com/doi/10.1002/1521-3765(20021004)8:19%3C4510::AID-CHEM4510%3E3.0. [51] R. Garcia, A. Paulo, A\u0302. Domingos, I. Santos, J. Organomet. Chem. 632 (2001)\n CO;2-L. 41\u201348. https://www.sciencedirect.com/science/article/abs/pii/S0022328X01008\n[19] D.C. Gerbino, E. Hevia, D. Morales, M.E.N. Clemente, J. Pe\u0301rez, L. Riera, V. Riera, 385.\n D. Miguel, Chem. Commun. (2003) 328\u2013329. https://pubs.rsc.org/en/content/ar [52] A. Vlc\u030cek, in: A.J. Lees (Ed.), Topics in Organometallic Chemistry: Photophysics of\n ticlelanding/2003/cc/b210860g. Organometallics, Springer - Verlag, Berlin, Heidelberg, 2010, pp. 73\u2013114. https\n[20] L. Cuesta, D.C. Gerbino, E. Hevia, D. Morales, M.E. Navarro Clemente, J. Pe\u0301rez, ://link.springer.com/chapter/10.1007/3418_2009_4.\n L. Riera, V. Riera, D. Miguel, I. del R\u00edo, S. Garc\u00eda-Granda, Chem. Eur. J. 10 (2004) [53] K. Srinivas, C. Naga Babu, G. Prabusankar, Dalton Trans. 44 (2015) 15636\u201315644.\n 1765\u20131777. https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ch [54] H.V. Huynh, Chem. Rev. 118 (2018) 9457\u20139492.\n em.200305577. [55] S.V.C. Vummaleti, D.J. Nelson, A. Poater, A. Go\u0301mez-Sua\u0301rez, D.B. Cordes, A.M.\n[21] L. Cuesta, M.A. Huertos, D. Morales, J. Pe\u0301rez, L. Riera, V. Riera, D. Miguel, Z. Slawin, S.P. Nolan, L. Cavallo, Chem. Sci. 6 (2015) 1895\u20131904. https://pubs.rsc.\n A. Mene\u0301ndez-Vela\u0301zquez, S. Garc\u00eda-Granda, Inorg. Chem. 46 (2007) 2836\u20132845. org/en/content/articlelanding/2015/sc/c4sc03264k.\n[22] S.E. Kabir, J. Alam, S. Ghosh, K. Kundu, G. Hogarth, D.A. Tocher, G.M.G. Hossain, [56] A. Liske, K. Verlinden, H. Buhl, K. Schaper, C. Ganter, Organometallics 32 (2013)\n H.W. Roesky, Dalton Trans. (2009) 4458\u20134467. 5269\u20135272.\n[23] R.F. Semeniuc, T.J. Reamer, J.P. Blitz, K.A. Wheeler, M.D. Smith, Inorg. Chem. 49 [57] F.L. Thorp-Greenwood, R.G. Balasingham, M.P. Coogan, J. Organomet. Chem. 714\n (2010) 2624\u20132629. (2012) 12\u201321.\n[24] R. Are\u0301valo, J. Pe\u0301rez, L. Riera, Inorg. Chem. 52 (2013) 6785\u20136787. [58] V. Ferna\u0301ndez-Moreira, F.L. Thorp-Greenwood, A.J. Amoroso, J. Cable, J.B. Court,\n[25] V. Ferna\u0301ndez-Moreira, H. Sastre-Mart\u00edn, Inorg. Chim. Acta 460 (2017) 127\u2013133. V. Gray, A.J. Hayes, R.L. Jenkins, B.M. Kariuki, D. Lloyd, C.O. Millet, C.F. Williams,\n[26] M. He, H.V. Ching, C. Policar, H.C. Bertrand, New J. Chem. 42 (2018) M.P. Coogan, Org. Biomol. Chem. 8 (2010) 3888\u20133901.\n 11312\u201311323. https://pubs.rsc.org/en/content/articlelanding/2018/nj/c [59] C. Otero, A. Carren\u0303o, R. Polanco, F.M. Llancalahuen, R. Arratia-Pe\u0301rez, M. Gacit\u00faa,\n 8nj01960f. J.A. Fuentes, Front. Chem. 7 (2019), 1-12, 454, https://www.frontiersin.org/artic\n[27] M.S. Capper, A. Enriquez Garcia, N. Macia, B. Lai, J.-B. Lin, M. Nomura, les/10.3389/fchem.2019.00454/full.\n A. Alihosseinzadeh, S. Ponnurangam, B. Heyne, C.S. Shemanko, F. Jalilehvand, [60] N. Wiratpruk, G.K. Bindra, A. Hamilton, M.D. Hulett, P.J. Barnard, Dalton Trans.\n J. Biol. Inorg. Chem. 25 (2020) 759\u2013776. 51 (2022) 7630\u20137643.\n[28] M.S. Capper, A. Enriquez Garcia, B. Lai, O.B. Wang, B.S. Gelfand, C.S. Shemanko,\n F. Jalilehvand, Dalton Trans. 50 (2021) 5968\u20135977.\n\n\n\n\n 10\n\f", "pages_extracted": 10, "text_length": 64515}