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Cyclometalated Iridium(III) and Rhodium(III) Complexes Containing Naphthyridine Ligands: Synthesis, Characterization and Biological Studies
Journal of Inorganic and General Chemistry
ARTICLE
DOI: 10.1002/zaac.201600378
Zeitschrift für anorganische und allgemeine Chemie
Cyclometalated Iridium(III) and Rhodium(III) Complexes
Containing Naphthyridine Ligands: Synthesis, Characterization
and Biological Studies
Marion Graf,[a] Yvonne Gothe,[b] Nils Metzler-Nolte,[b] and Karlheinz Sünkel*[a]
Dedicated to Prof. Dr. Dr.h.c. Wolfgang Beck on the Occasion of his 85th Birthday
Abstract. The synthesis, crystal structure, and biological activity of (3);M=Ir(4)]aredescribed.Thenewcompoundswerepreparedby
new bis-cyclometalated compounds [M(ptpy) (4-chloro-2-methyl-1,8- thereactionof[{M(μ-Cl)(ptpy) } ](M=Rh,Ir)withthecorrespond-
2 2 2
naphthyridine)]PF [M = Rh (1); M = Ir (2); ptpy = 2-(p-tolyl)- ing naphthyridine ligands. Themolecular structures of compounds 1,
6
pyridinato] and [M(ptpy) (2-methyl-1,8-naphthyridine)]PF [M = Rh 3,and4wereconfirmedbysingle-crystalX-raydiffractionstudies.
2 6
Introduction
chiometric amounts of the ligands at ambient temperatures
Cyclometalated iridium(III) complexes have attracted con-
(Scheme1).
siderableinterestaselectroluminescentmaterialsforhighlyef-
The new compounds 1–4 were examined by NMR and IR
ficient organic light emitting devices (OLEDs),[1] labels for
spectroscopy,aswellasbymassspectrometry.TheFAB+mass
bioimaging,[2] and optical sensors.[3] Several IrIII and RhIII
spectra showed the molecular peaks for mononuclear com-
complexes exhibit high biological activity and thus group 9
plexes, asshown in Scheme1. However,a mononuclear com-
metal complexes are regarded as a potential source of novel
plex with a monodentate naphthyridine ligand cannot be fully
metallodrugs.[4] In the course of our studies on bis-cyclo-
excluded.Inthe1HNMRspectraofthecompoundsthesignals
metalated RhIII and IrIII complexes we examined several bio-
of the naphthyridine ligands were partially overlapping with
moleculesaswellassubstitutedphenanthrolinesorbipyridines
thesignalsofthetolylpyridinatoligand.Themajordifferences
as ancillaryligands.[5] Recently the invivo anticancer activity
between the spectra was the appearance of a singlet at δ ≈
of naphthyridine complexes was reported.[6] Naphthyridines
7.66ppm in the spectra of compounds 1 and 2, which was
are an interesting class of ligands. Although they are structur-
absent in the spectra of 3 and 4, and of a doublet at δ = 8.48
ally related to bipyridines and phenanthrolines, they have a
or8.60ppm,for3and4,respectively,whichwasabsentinthe
verysmall“chelatebite”andthustheycanactasmonodentate
spectraof1and2.Weassignthe singletstoH3(cid:2)andthedou-
or bidentate chelating or bridging ligands.[7]
blets to H4(cid:2) of the naphthyridine ligands. Together with the
Wenowinvestigatedthereactionofcyclometallatediridium
assignments, which we made earlier for the spectra of the re-
and rhodium complexes [M(μ-Cl)(ptpy) ] [ptpy = 2-(p-tolyl)
2 2 lated[M(ptpy) (Cl Me phen)]+compounds,[5m]itwaspossible
pyridinato] with 4-chloro-2-methyl-1,8-naphthyridine and 2- 2 2 2
toassignmostoftheprotonresonances.The13CNMRspectra
methyl-1,8-naphthyridine. Herein we describe the synthesis,
usually showed two resonances for each of the diastereotopic
thestructuralcharacterizationaswellasthebiologicalproper-
carbon atoms of the tolylpyridinato ligands and one signal for
ties of the obtained products.
each of the naphthyridine carbons. However, the resonances
for C12 in 4 and for C4(cid:2) in 3 and 4 could not be identified.
Results and Discussion
However, again discrimination between a mononuclear com-
Synthesis and Characterization of New Compounds plex with a monodentate or bidentate naphthyridine ligand is
The title compounds 1–4 were prepared by “bridge-split- not unambiguously possible. Therefore, a crystal structure
ting” reactions of [{M(μ-Cl)(ptpy) } ] (M = Rh, Ir) with stoi- study of all four compounds was undertaken.
2 2
* Prof.Dr.K.Sünkel
Fax:+49-89-218077774 Molecular Structures of Compounds 1, 3, and 4
E-Mail:suenk@cup.uni-muenchen.de
[a] DepartmentofChemistry Crystals of all compounds were obtained by crystallization
LudwigMaximiliansUniversityMunich
from mixtures of dichloromethane/methanol/isohexane at am-
Butenandtstr.9
81377Munich,Germany bient temperature. They were studied with a BRUKER D8
[b]AnorganischeChemieI Venture TXS (1, 2, 4) or an OXFORD XCalibur 2 (3) dif-
RuhrUniversityBochum
fractometer (further details see Experimental Section). All
Universitätsstr.150
44801Bochum,Germany structures could be solved and showed the naphthyridine li-
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Journal of Inorganic and General Chemistry
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Scheme1.Synthesisof1–4.
gand as a chelating N,N(cid:2)-donor. Unfortunately, the quality of
thecrystalsofcompound2wasnotsufficientforafullrefine-
ment. Selected ORTEP views of the cations of 1 and 4 are
shown in Figure1 and Figure2, respectively.
Figure2. Molecular structure of 4 in the crystal. Thermal ellipsoids
aredrawnatthe30%probabilitylevel.
for Ir; chelate angles N–C–M = 81.25(cid:3)0.25° for the Rh
compounds and 80.65(cid:3)0.15° for Ir). The structural param-
eters of the M-naphthyridine units together with the data of
Figure1. Molecular structure of 1 in the crystal. Thermal ellipsoids [Rh(OMe napy)(cod)](A)[7b]and[Cp*Ir(napy) ](PF ) (B)[7c]
aredrawnatthe30%probabilitylevel. 2 2 6 2
are collected in Table1.
All compounds show the expected octahedral coordination As can be seen from these data, all compounds, especially
withtwocyclometalated2-(p-tolyl)pyridinatoligandswiththe 1,haveaverysmallchelateangle.Whileincompounds3and
pyridine N atoms in trans configuration (N–M–N = 4 the M–N bond lengths are very similar (Δ = 0.02Å),
max
173.3(cid:3)0.6°). The bonding parameters of the M(ptpy) unit which is also observed in the Ir complex B with an unsubsti-
2
correspondtotheusualobservedonesforthiswellknowntype tuted naphthyridine ligand, the two M–N bonds in 1 are very
of compounds (distances M–N = 2.04(cid:3)0.01Å for the Rh different(Δ =0.12Å). Thelongerbond isassociated withthe
ptpy
compounds and 2.063(cid:3)0.005Å for Ir; distances M–C = Clsubstitutedpyridinering,whichisobviouslyamuchweaker
ptpy
1.976(cid:3)0.010Å for the Rh compounds and 2.001(cid:3)0.006Å donor. Such a bond asymmetry, although to a smaller extent
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Table1.Importantbondparametersofthemetal-naphthyridineunit. plexes and cisplatin are very similar for HT-29 cells, all com-
plexes exhibit a significant higher activity towards MCF-7
M–N (N–M–N) C–M–N
napy napy napy cells compared to cisplatin. These initial biological studies il-
1 2.340(5) 58.0(2) 176.0(2)
lustrate the high antiproliferative potential of our complexes
2.223(5) 155.9(2)
emphasisingthesuitabilityofiridiumcomplexesasnewprom-
3 2.215(2) 60.60(8) 170.94(10)
2.235(2) 162.76(10) ising anti-cancer agents.
4 2.195(6) 60.9(2) 170.1(3)
2.209(7) 162.4(3)
A 2.075(5) 63.6(2) – Conclusions
2.149(5)
B 2.147(11) 61.0(4) – The synthesis and characterization of four new bis-cyclo-
2.167(11) metalated compounds 1–4 along with their biological activity
were reported. All compounds exhibit cytotoxic effects
(Δ = 0.075Å), is also observed in B, which contains an oxo towards two cell lines (HT29 and MCF-7). The crystal and
substituentintheringwiththelongerbond.Theplanesofthe molecular structure of the new compounds 1, 3 and 4 were
threechelateringsincludeanglesof86(cid:3)1°inallcompounds; confirmed by X-ray crystal structure determination. 1 and 2
thetwohalvesofthenaphthyridineligandarenearlycoplanar showedsimilarcytotoxicitytocisplatin.Thecompound3was
(0.3° interplanar angle). less active. The compound 4 exhibited the greatest activity in
this series.
Biological Activity
Experimental Section
Recently IrIII complexes have gained considerable attention
GeneralProcedures:Allmanipulationswereperformedinanatmo-
asanticanceragents,astheyhaveshownpromisingantiprolif-
sphere of dry nitrogen using conventional Schlenk techniques. Sol-
erative activity toward several cancer cell lines.[4,5m] Similar
ventsweredriedwithstandardproceduresandstoredundernitrogen.
to this, different metal naphthyridine complexes were investi-
2-(p-Tolyl)pyridine and the naphthyridine ligands were purchased
gated for anticancer activity.[6]
from Sigma-Aldrich and used as received. The complexes
To obtain a first insight into the antitumor activity of com-
[{Ir(μ-Cl)(ptpy) } ]and[{Rh(μ-Cl)(ptpy) } ]weresynthesizedbythe
2 2 2 2
pounds1–4,theirinvitrotoxicitytowardsthecommonlyused literaturemethod.[5b]NMRspectrawererecordedwithaJeolEclipse
cancer cell lines HT-29 (human colon carcinoma) and MCF- 400. Chemical shifts were referenced to the solvent signal [δ =
7 (human breast carcinoma) was investigated (Table2). The 5.31ppm for 1H and 53.8ppm (CD Cl ) for 13C NMR spectra]. The
2 2
cytotoxicity was evaluated using the MTT assay, which mea- 13C resonances are given in the sequence C1–C13 of the tolyl-
suresthemitochondrialmetabolismintheentirecell.Allcom- pyridinatoandC2’–C7’;C4a,C8a,C Me forthenaphthyridineligands,
respectively.IRspectraweremeasuredinKBrpelletswithaMattson
pounds exhibit appreciable antiproliferative effects towards
Perkin-Elmer983Gspectrometer.Massspectrawereobtainedwitha
both cell lines in the lower micro molar range. Among com-
JeolMstationJMS700.Elementalanalyses(C,H,N)wereperformed
plexes 1–4, the greatest activity was observed for 4 with IC
50 by the Microanalytical Laboratory of the Department of Chemistry,
values of 2.83μM for HT-29 and 1.67μM for MCF-7. It is
LMUMunich,withaHeraeusElementarVarioELinstrument.
noticed, that the iridium complexes 2 and 4 feature a slightly
higher antiproliferative activity against both cancer cell lines CellCultureandCytotoxicity:Dulbecco’sModifiedEagle’sMedium
comparedtotheirrhodiumanalogues1and3,respectively.For (DMEM),containing10%FCS,1%penicillinandstreptomycin,was
a better comparison, the antiproliferative activity of the well- usedasgrowthmedium.MCF-7andHT-29cellsweredetachedfrom
thewellswithtrypsinandEDTA,harvestedbycentrifugationandre-
established chemotherapeutic agent cisplatin was investigated
suspendedincellculturemedium.Theassayswerecarriedouton96
under the same conditions. While the IC values of the com-
50 wellplateswith6000cellsperwellforbothcelllines.After24hof
incubation at 37°C and 10% CO , the cells were treated with the
2
Table2. Cytotoxicity data of the complexes toward MCF-7 and HT- compounds(withDMSOconcentrationsof0.5%)withafinalvolume
29cells.IC valuesareexpressedasmeans[μM]((cid:3)standarddevia-
50 of200μLperwell.Foranegativecontrol,oneseriesofcellswasleft
tion) of three independent experiments. Numbers are reported to two
untreated.Thecellswereincubatedfor48hfollowedbyadding50μL
relevantdigitsinallcasesforconsistency,thusresultinginapparently
MTT(2.5mg·mL–1).Afteranincubationtimeof2h,themediumwas
differentprecision.
removedand200μLDMSOwereadded.Theformazancrystalswere
Compound Cellline IC 50 /μM dissolved and the absorption wasmeasured at 550nm, using a refer-
1 HT29 6.10(cid:3)0.84 ence wavelength of 620nm. Each test was repeated in triplicates or
MCF-7 6.51(cid:3)0.10 quadruplicatesinatleastthreeindependentexperimentsforeachcell
2 HT29 5.4(cid:3)2.1 line.
MCF-7 4.0(cid:3)1.1
3 HT29 11.6(cid:3)2.8 GeneralSynthesisof1–4:Toasolutionof[{M(μ-Cl)(ptpy) } ](M=
2 2
MCF-7 9.5(cid:3)4.8 Rh, Ir) (0.15mmol) in 25mL of a mixture of CH Cl /MeOH/H O
2 2 2
4 HT29 2.83(cid:3)0.66 (1:1:0.5)thenaphthyridineligand(0.3mmol)wasaddedandthemix-
MCF-7 1.67(cid:3)0.80 turerefluxedwithstirringfor3h.Aftercoolingtoroomtemperature
Cisplatin HT-29 4.14(cid:3)0.31
KPF (0.4mmol)wasadded.Thesolventwasremovedtodrynessin
MCF-7 23.03(cid:3)0.25 6
vacuo and the residue dissolved in dichloromethane and chromato-
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graphedonaluminawithCH Cl /acetone(9:1)astheeluent.Thesolu- (4.09);N7.69(7.69)%.MS(FAB+):m/z=583.1[M+]complexcat-
2 2
tion was evaporated to dryness and the residue was redissolved in ion.1HNMR(400MHz,CD Cl ):δ=8.68(dd,J=4.6/1.6Hz,1H.
2 2
5mL of dichloromethane and the product was precipitated by slow H7’), 8.58 (dd, J = 8.3/1.6Hz, 1H. H5’), 8.48 (d, J = 8.5Hz, 1 H,
diffusionofisohexane. H4’),7.95and7.93(2m,2H,H3),7.91and7.89(2m,2H,H4),7.88/
7.83 (2m, 2 H, H6), 7.72 (dd, J = 8.3/4.7Hz, 1 H, H6’), 7.65/7.63
[Rh(ptpy) 2 (4-chloro-2-methyl-1,8-naphthyridine)]PF 6 (1): Yield: (2m,2H,H8),7.05(m,2H,H5),6.92/6.90(2m,2H,H9),6.11/6.08
90mg (48.8%). C 33 H 27 ClN 4 F 6 PRh (762.93): C 50.13 (calcd. 51.95); (2s,2 H,H11), 2.09(s, 3H,Me napy ), 2.11(s, 6H, Me ptpy ).13C{1H}
H3.66(3.57);N7.14(7.34)%.MS(FAB+):m/z=617.6[M+]com- NMR (101MHz, CD Cl ): δ = 164.95/164.87 (2d, J = 1.9Hz),
2 2 RhC
plex cation. 1H NMR (400MHz, CD 2 Cl 2 ): δ = 8.85 (dd, J = 8.5/ 119.84/119.76 (2d, J RhC = 1.6Hz), 139.2/138.9, 124.9/124.6, 149.6/
1.4Hz,1H,H5’),8.82(dd,J=4.7/1.5,1H,H7’),7.96and7.94(2m, 149.5, 140.8/140.7 (2d, J = 1.7Hz), 125.1/125.0, 123.3/123.2,
RhC
4H,H3+H4),7.86/7.84(2m,2H,H6),7.81(dd,J=8.4/4.7Hz,1H, 141.5/141.4,133.93/133.88,162.9/162.8(2d,J =35.3Hz),21.94/
RhC
H6’),7.65(s,1H,H3’),7.585/7.575(2d,J=7.9Hz,2H,H8),7.07 21.92; 165.9, 124.6, (C4 n.o.), 138.8, 127.1, 121.5, 157.8 (d, J =
RhC
(m, 2 H, H5), 6.84/6.82 (2m, 2 H, H9), 6.04/6.01 (2”s“, 2 H, H11), 1.9Hz),23.3.
2.06(s,3H,Me ),2.10(s,6H,Me ).13C{1H}NMR(101MHz,
napy ptpy
[Ir(ptpy) (2-methyl-1,8-naphthyridine)]PF (4): Yield: 130mg
CD Cl ): δ = 164.95/164.82 (2d, J = 1.8Hz), 119.92/119.86 (2d, 2 6
2 2 RhC
(64.4%). C H N F PIr (817.79): C 48.20 (calcd. 48.47); H 3.64
J =1.5Hz),138.9,125.2/125.1,149.62/149.56,140.89/140.87(2d, 33 28 4 6
RhC (3.45); N 6.74 (6.85)%. MS (FAB+): m/z = 673.19 [M+] complex
J =1.8Hz),126.8/125.8,123.4/123.3,141.5/141.4,133.98/133.95,
RhC cation. 1H NMR (400MHz, CD Cl ): δ = 8.75 (dd, J = 4.7/1.5Hz,
162.35/162.25(2d,J =35.5Hz),21.95/21.93;166.0,124.7,145.4, 2 2
RhC
1H.H7’),8.69(dd,J=8.4/1.6Hz,1H,H5’),8.60(d,J=8.6Hz,1
136.1,126.8,154.1,120.9,157.76(d,J =1.9Hz),23.3.
RhC
H,H4’),7.96and7.95(2m,2H,H3),7.94and7.90(2m,2H,H4),
[Ir(ptpy) (4-chloro-2-methyl-1,8-naphthyridine)]PF (2): Yield: 7.83/7.81(2dd, J= 7.4/1.4Hz,2 H,H6), 7.72(dd, J= 8.4/4.8Hz,1
2 6
98mg(46.2%).C H ClN F PIr(852.24):C46.37(calcd.46.51);H H, H6’), 7.62/7.58 (2d, J = 8.3Hz, 2 H, H8), 7.58 (d, J = 8.3Hz, 1
33 27 4 6
3.38(3.19);N6.42(6.57)%.MS(FAB+):m/z=707.15[M+]complex H,H3’),7.04/7.02(2m,2H,H5),6.84/6.82(2m,2H,H9),6.06/6.02
cation.1HNMR(400MHz,CD 2 Cl 2 ):δ=8.78(dd,J=8.4/1.6Hz,1 (2s,2H, H11),2.08(s,3H, Me napy ),2.07(s,6 H,Me ptpy ).13C{1H}
H,H5’),8.76(dd,J=4.3/1.5Hz,1H,H7’),7.96and7.94(2m,2H, NMR(101MHz,CD 2 Cl 2 ):δ=168.0/167.9,119.6/119.5,137.9/137.6,
H3),7.92and7.90(2m,2H,H4),7.89–7.84(m,2H,H6),7.82(dd, 123.99/123.95, 149.6/149.5, 142.2/141.6, 125.8, 123.2/123.1, 140.9/
J=8.5/4.7Hz,H6’),7.68(s,1H,H3’),7.635/7.625(2d,J=7.9Hz, 140.7,132.80/132.77,(C12n.o.),21.78/21.77;164.2,124.8,(C4n.o.),
2H,H8),7.07(m,2H,H5),6.93/6.91(2m,2H,H9),6.10/6.07(2s, 138.7,127.8,150.9,122.3,159.9,23.2.
2H,H11),2.22(s,3H,Me ),2.11(s,6H,Me ).13C{1H}NMR
napy ptpy X-ray Structural Determination: The structures were solved by di-
(101MHz, CD Cl ): δ = 167.83/167.80, 119.6/119.5, 138.84/138.82,
2 2 rectmethods(SIR97)andrefinedbyfull-matrixleast-squarescalcula-
124.09/124.05, 149.6, 141.6/141.5, 126.5, 123.4/123.2, 140.9/140.7, tionsonF2(SHELXL-2014/7),asimplementedintheWINGXstruc-
132.84/132.79, 141.68/141.64, 21.77/21.75; 164.2, 124.8, 144.1, ture package.[8] Details of the crystal data, data collection, structure
134.8,127.7,152.0,122.0,160.0,23.2.
solution,andrefinementparametersaresummarizedinTable3.
[Rh(ptpy) (2-methyl-1,8-naphthyridine)]PF (3): Yield: 120mg Crystallographicdata(excludingstructurefactors)forthestructuresin
2 6
(68.6%). C H N F PRh (728.48): C 53.95 (calcd.54.41); H, 4.09 this paper have been deposited with the Cambridge Crystallographic
33 28 4 6
Table3.Crystaldataandstructurerefinementdetailsforcompounds1,3,and4.
1 3 4
Empiricalformula C H ClF RhN P·½CH Cl C H F RhN P C H F IrN P
33 27 6 4 2 2 33 28 6 4 33 28 6 4
Formulaweight 805.38 728.47 817.76
Temperature/K 100(2) 293(2) 100(2)
Crystalsystem triclinic monoclinic monoclinic
Spacegroup P1¯ P2 /n P2 /n
1 1
a/Å 8.7417(4) 8.809(2) 8.7966(3)
b/Å 12.8605(6) 23.0867(4) 23.0409(8)
c/Å 14.7307(7) 14.940(3) 14.8530(5)
α/° 99.421(1) 90 90
β/° 99.062(1) 96.286(2) 96.198(19)
γ/° 90.047(1) 90 90
Volume/Å3 1612.73(13) 3020.15(11) 2992.83(18)
Z 2 4 4
ρ /g·cm–3 1.659 1.602 1.815
calc
μ/mm–1 0.812 0.687 4.584
θrangefordatacollection/° 2.313to26.430 4.179to26.372 2.242to26.412
Reflectionsmeasured 37354 15916 66154
R 0.0289 0.0283 0.0351
int
Observedreflections 6602 6133 6123
Parameters/restraints 436/0 409/0 409/0
R(F ) 0.0631 0.0370 0.0512
obs
R (F2) 0.1622 0.0457 0.0561
w
S 0.989 1.027 1.294
Maxelectrondensity/e·Å–3 2.543 0.862 6.463
Minelectrondensity/e·Å–3 –2.503 –0.554 –3.200
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DataCentre,CCDC,12UnionRoad,CambridgeCB21EZ,UK.Copies [3]a) C.S. Mak, D. Pentlehner, M. Stich, O. Wolfbeis, W.K. Chan,
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3, and 4 (Fax: +44-1223-336-033; E-Mail: deposit@ccdc.cam.ac.uk,
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http://www.ccdc.cam.ac.uk).
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Acknowledgements [4]Forareviewonbioactiveiridiumandrhodiumcomplexesasthera-
peuticagents see:a) C.-H.Leung,H.-J. Zhong,S.-H. Chan,d.-L.
Ma, Coord. Chem. Rev. 2013, 257, 1764, and references cited
TheauthorsaregratefultotheDepartmentofChemistryoftheLudwig therein; b) P.-K. Lee, H.-T. Law, H.-W. Liu, K.-W. Lo, Inorg.
MaximilianUniversityofMunichforsupportingtheseinvestigations. Chem.2011,50,8570;c)Y.Geldmacher,M.Oleszak,W.S.Sheld-
P. Mayer is acknowledged for collecting the X-ray crystal data. The rick,Inorg.Chim.Acta2012,393,84.
JohnsonMatthey plc,Reading, UK,is gratefullyacknowledgedfor a [5]a) M. Graf, H.-C. Böttcher, K. Sünkel, Inorg. Chim. Acta 2013,
generousloanofhydratediridiumchloride. 394, 363; b) H.-C. Böttcher, M. Graf, K. Sünkel, P. Mayer, H.
Krüger, Inorg. Chim. Acta 2011, 365, 103; c) H.-C. Böttcher, M.
Graf,K.Sünkel,H.Krüger,Inorg.Chim.Acta2011,370,523;d)
Keywords: Rhodium; Iridium; Naphthyridine; Cyclomet- H.-C. Böttcher, M. Graf, K. Sünkel, B. Salert, H. Krüger, Inorg.
alated compounds; Biological activity Chem. Commun. 2011, 14, 377; e) K. Sünkel, M. Graf, H.-C.
Böttcher, B. Salert, H. Krüger, Inorg. Chem. Commun. 2011, 14,
539; f) M.W. Thesen, H. Krüger, S. Janietz, A. Wedel, M. Graf,
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
M. Graf, Y. Gothe, N. Metzler-Nolte, K. Sünkel* ............ 1–6
Cyclometalated Iridium(III) and Rhodium(III) Complexes
Containing Naphthyridine Ligands: Synthesis, Characteriza-
tion and Biological Studies
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