👤 M. A. Kinzhalov

A series of ESIPT-capable Ir^III-(acyclic diaminocarbene species) (ESIPT = Excited-state intramolecular proton transfer) exhibiting strong photoluminescence properties is described. The emission profile is strongly influenced by the nature of the azaheterocyclic fragment in the diaminocarbene ligand: pyrazine-derived species display phosphorescence bands red-shifted by approximately 100 nm compared to their pyridine analogues. This redshift is attributed to the luminescence of tautomerized species formed via an ESIPT process, wherein the iridium center enhances the basicity of the pyrazine ring, facilitating proton transfer from the C_carbene-NH groups. This interpretation is supported by the solvatochromic emission behavior of complexes prepared and corroborated by density functional theory calculations. Prepared Ir^III-(acyclic diaminocarbene species) complexes represent the first example of metal-organic luminophores in which the ESIPT mechanism involves direct participation of the metal center, resulting in orange emission. Show less

Abstract This article presents the synthesis and detailed structural investigation of a new palladium(II) heteroligand complex trans-[PdCl(CNXyl)2(C{CN(H)Xyl}2)]Cl, containing an acyclic diaminocarbene ligand and two isocyanide ligands. X-ray diffraction and NMR spectroscopy revealed that complex is stabilized both in the crystal and in solution by a system of N–H···Cl– hydrogen bonds formed between one chloride anion and two N–H groups of the diaminocarbene ligand (N–H···Cl–···H–N), with calculated energies of 3.8–5.4 kcal/mol. A Cambridge Structural Database search identified 22 other palladium(II) acyclic diaminocarbene complexes with similar N–H···X···H–N (X = Cl–, Br–, O=C<, O=S<, etc.) hydrogen-bonded systems. The complex demonstrated significant antiproliferative activity against the triple-negative breast cancer cell line MDA-MB-231, with an IC50 value of 5.55 ± 0.45 µM, which is four times higher than that of cisplatin. Show less

A series of cyclometalated platinum-(II) complexes bearing neutral isocyanide or acyclic diaminocarbene ancillary ligands were designed and developed. Their photophysical properties were systematically studied in different polymer systems: poly-(methyl methacrylate), polystyrene, poly-(isobornyl acrylate), and copolymers based on them. The dependence of luminescent characteristics on the concentration of the doped complex (0.5-10 wt %), composition, and properties of the polymer material was investigated as key factors for the measurement of quantum yields, excited-state lifetimes, and spectral profiles in routine studies. Show less

AbstractHydrolytically stable PdII and PtII complexes supported by acyclic diaminocarbene ligands represent a novel class of structural organometallic anticancer agents exhibiting nanomolar antiproliferative activity in a panel of cancer cell lines (IC50 0.07–0.81 μM) and up to 300‐fold selectivity for cancer cells over normal primary fibroblasts. The lead drug candidate was 300 times more potent than cisplatin in vitro and showed higher efficacy in reducing the growth of aggressive MDA‐MB‐231 xenograft tumors in mice. Show less

A new application for bis(cyclometalated) iridium(III) species containing ancillary acyclic diaminocarbene ligands, viz. for sensing of mercury(II) ions, is disclosed. A family of bis(cyclometalated) iridium(III) species supported by both parent isocyanide and acyclic diaminocarbene ligands was prepared, and their electrochemical and photophysical properties were evaluated, revealing efficient blue-green phosphorescence in solution with quantum yields of up to 55%. We uncovered that the photophysical properties of these complexes are dramatically altered by the presence of metal ions and that the complex [Ir(ppy)₂(CN){C(NH₂)(NHC₆H₄-4-X)}] with an ADC ligand reacts selectively with Hg²⁺ ions, enabling its use for sensing of mercury(II) ions in solution. The limit of detection was as low as 2.63 × 10^-7 M, and additional mechanistic studies indicated the formation of an unusual dinuclear iridium(III) cyclometalated intermediate, bridged by a mercury dicyano fragment as a driving force of mercury sensing. Show less

Bis-ADC complexes cis-[Pd{C(NHC6H4NH2)N(H)R}2]Cl2 (R = Xyl 4a, Cy 4b, C6H4-4-F 4c) and cis-[Pt{C(NHC6H4NH2)N(H)R}2]Cl2 (R = Xyl 5a, Cy 5b, C6H4-4-F 5c) were synthesized via the metal-mediated coupling of two isocyanide ligands in cis-[MCl2(CNR)2] (M = Pd, Pt; R = Xyl, Cy, C6H4-4-F) and 1,2-diaminobenzene. New compounds 4c and 5a–c were characterized by HR ESI+-MS, IR, and 1H, 13C{1H} and 195Pt{1H} NMR spectroscopy; the structures of 4a and 5a were elucidated by single-crystal X-ray diffraction. The stability of the ADC complexes in aqueous media (5 mM NaCl) was monitored by UV absorption spectroscopy, HR ESI+ mass spectrometry, and 195Pt{1H} NMR spectroscopy (for 5a). Molar conductivity measurements in MeOH (ΛM = 167–173 Ω−1 mol−1 cm2) indicate that, in this solvent, the ADC complexes exist as dicationic species of [A][Q]2 type. The ADC complexes binding to CT DNA was investigated by means of spectroscopic and hydrodynamic techniques including UV absorption and circular dichroism spectroscopy, fluorescence spectroscopy, low-gradient viscometry, flow birefringence, and AFM imaging. As a result, complexes 4a and 5a were shown to bind double-stranded DNA predominantly via the formation of monofunctional adducts in the major groove of the macromolecule. Binding of the ADC complexes also provokes the formation of a large number of intermolecular DNA–DNA contacts in solution. The antiproliferative activity of all prepared ADC complexes 4a–c and 5a–c was evaluated in vitro against three human carcinoma cell lines (HT-29, MDA-MB-231, and MCF-7) and two non-tumorigenic cell lines (L929 and RC-124) and compared to that of cisplatin. Among the compounds studied, complexes 4a and 5a appeared to be the most active species with IC50 values in MCF-7 cells of about 10 μM. Show less