Padavattan Govindaswamy

Ruthenium Porphyrin Compounds for Photodynamic Therapy of Cancer

Five 5,10,15,20-tetra(4-pyridyl)porphyrin (TPP) areneruthenium(II) derivatives and a p-cymeneosmium and two pentamethylcyclopentadienyliridium and -rhodium analogues were prepared and characterized as potential photosensitizing chemotherapeutic agents. The biological effects of all these derivatives were assessed on human melanoma tumor cells, and their cellular uptake and intracellular localization were determined. All molecules, except the rhodium complex which was not cytotoxic, demonstrated comparable cytotoxicity in the absence of laser irradiation. The ruthenium complexes exhibited excellent phototoxicities toward melanoma cells when exposed to laser light at 652 nm. Cellular uptake and localization microscopy studies of [Ru 4(eta (6)-C 6H 5CH 3) 4(TPP)Cl 8] and [Rh 4(eta (5)-C 5Me 5) 4(TPP)Cl 8] revealed that they accumulated in the melanoma cell cytoplasm in granular structures different from lysosomes. The fluorescent porphyrin moiety and the metal component were localized in similar structures within the cells. Thus, the porphyrin areneruthenium(II) derivatives represent a promising new class of organometallic photosensitizers able to combine chemotherapeutic activity with photodynamic therapeutic treatment of cancer.

Self-assembled hexanuclear arene ruthenium metallo-prisms with unexpected double helical chirality

Self-assembly of 2,4,6-tripyridyl-1,3,5-triazine (tpt) subunits with arene ruthenium building blocks and oxalato bridges affords cationic triangular metallo-prisms of the type [Ru6(arene)6(tpt)2(C2O4)3]6+ (arene = C6Me6 and p-Pr(i)C6H4Me); the unexpected double helical chirality of the metallo-prisms observed in the solid state persists in solution giving rise to two different stereodynamic processes as demonstrated by NMR enantiodifferentiation experiments.

Chiral or not chiral? A case study of the hexanuclear metalloprisms [Cp(6)M(6)(micro(3)-tpt-kappaN)(2)(micro-C2O4-kappaO)(3)]6+ (M = Rh, Ir, tpt = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine).

Cationic hexarhodium and hexairidium complexes with a trigonal prismatic architecture have been synthesised in good yield by self-assembly of the dinuclear oxalato-bridged complexes [Cp(2)M(2)(micro-C(2)O(4)-kappaO)Cl(2)] (M = Rh; 1: Ir; 2) with 2,4,6-tri(pyridine-4-yl)-1,3,5-triazine (tpt) in the presence of AgO(3)SCF(3). The trigonal prismatic cations [Cp(6)Rh(6)(micro(3)-tpt-kappaN)(2)(micro-C(2)O(4)-kappaO)(3)](6+) (3) and [Cp(6)Ir(6)(micro(3)-tpt-kappaN)(2)(micro-C(2)O(4)-kappaO)(3)](6+) (4) have been isolated as their triflate salts. The single-crystal X-ray structure analysis of [3][O(3)SCF(3)](6) shows two enantiomers in the racemic crystal (space group C2/c), the chirality being due to a twist of the two tpt units. By contrast, the single-crystal X-ray structure analysis of [4][O(3)SCF(3)](6) shows a perfectly eclipsed conformation of the tpt units, so that is not chiral in the crystal state (space group Fd3[combining macron]c). However, in solution, enantiodifferentiation in the presence of the chiral anion Delta-BINPHAT is observed by (1)H NMR spectrometry not only in the case of 3, but also in the case of 4. This suggests that the iridium derivative 4, which is not chiral in the solid state, adopts chiral conformations in solution.

Syntheses of (η6-p-cymene)ruthenium(II) piano-stool amine complexes: molecular structure of [(η6-C10H14)RuCl2(H2N-C6H4-p-Cl)]

The dimeric complex [{(η6-p-cymene)Ru(μ-Cl)Cl}2] (1) reacts with S,N-donor Schiff base ligands, para-substituted S-(thiophen-2-ylmethylene)phenylamines in methanol to give mononuclear amine complexes of the type [(η6-p-cymene)RuCl2(NH2–C6H4–p-X)] {X = H (2a); X = CH3 (2b); X = OCH3 (2c); X = Cl (2d); Br (2e) X = NO2 (2f), respectively} by hydrolysis of the imine group of the ligand after coordination to the metal. The complexes were characterized by analysis and IR and NMR spectroscopy. The molecular structure of [(η6-C10H14)RuCl2(H2N–C6H4–p-Cl)] (2d) was established by a single-crystal X-ray diffraction study.

Substitution reactions of diphenyl-2-pyridylphosphine with [(η5-C5Me5)M(μ-Cl)Cl]2 (M = Rh or Ir) dimers: Isolation of mono–, di– and chelating complexes

The reaction of [{(η5-C5Me5)M(μ-Cl)Cl}2] {where M = Rh (1), Ir (2)} with functionalized phosphine viz., diphenyl-2-pyridylphosphine (PPh2Py) in dichloromethane solvent yield neutral ϰ1-P-coordinated rhodium and iridium complexes [(η5-C5Me5)RhCl2(κ1-P-PPh2Py)]3 and [(η5-C5Me5) IrCl2(ϰ1-P-PPh2Py)]4. Reaction of complexes 1 and 2 with the ligand PPh2Py in methanol under reflux give bis-substituted complexes such as [(η5-C5Me5)RhCl(ϰ1-P-PPh2Py)2]+5 and [(η5-C5Me5)IrCl(ϰ1-P-PPh2Py)2]+6, whereas stirring in methanol at room temperature gives P-, N-chelating complexes of the type [(η5-C5Me5)RhCl(ϰ2-P-N-PPh2Py)]+ 7 and [(η5-C5Me5)IrCl(ϰ2-P-N-PPh2Py)]+8. Neutral ϰ1-P-coordinated complexes [(η5-C5Me5)RhCl2(ϰ1-P-PPh2Py)]3 and [(η5-C5Me5)IrCl2(ϰ1-P-PPh2Py)]4 easily undergo conversion to the cationic P-, N-chelating complexes [(η5-C5Me5)RhCl(ϰ2-P-N-PPh2Py)]+7 and [(η5-C5Me5) IrCl(ϰ2-P, N-PPh2Py)]+8 on stirring in methanol at room temperature. These complexes are characterized by FT-IR and FT-NMR spectroscopy as well as analytical methods. The molecular structures of the representative complexes [(η5-C5Me5)RhCl2(ϰ1-P-PPh2Py)]3, [(η5-C5Me5)IrCl2(ϰ1-P-PPh2Py)]4 and hexafluorophosphate salt of complex [(η5-C5Me5)IrCl(ϰ2-P-PPh2Py)2]+6 are established by single-crystal X-ray diffraction methods

Syntheses and characterization of η 5-pentamethylcyclopentadienyl rhodium(III) and iridium(III) complexes containing polypyridyls

Reaction of [(η 5-C5Me5)M(μ-Cl)Cl]2 {M = Rh (1), Ir (2)} and [(η 5-C5Me5)MCl2(DBT)] (DBT = dibenzothiophene) {M = Rh (3), Ir (4)} with polypyridyl ligands 2,3-bis(2-pyridyl)pyrazine (bpp), 2,3-bis(2-pyridyl)quinoxaline (bpq), 1,3,5-tris(2-pyridyl)-2,4,6-triazine (tptz), 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) and 4′-pyridyl-2,2′:6′,2′′-terpyridine (py-terpy) results in the formation of mononuclear cationic complexes, [(η 5-C5Me5)MCl(poly-py)]+ (poly-py = polypyridyl ligand). The complexes were isolated as hexafluorophosphate salts and characterized by IR and NMR spectroscopy.

Reactivity studies of (η6-arene)ruthenium(II) dimers with arylazoimidazole ligands: molecular structure of [(η6-p-cymene)RuCl(Me-C6H4-Nequals;N-C3H2N2-1-CH3)]PF6

The complexes [{(η 6-arene)Ru(μ-Cl)Cl}2] (arene = p-cymene (1), hexamethylbenzene reacts at low temperature with the arylazoimidazole (RaaiR′) ligands 2-(phenylazo)imidazole (Phai-H), 1-methyl-2-(phenylazo)imidazole (Phai-Me), 1-ethyl-2-(phenylazo)imidazole (Phai-Et), 2-(tolylazo)imidazole (Tai-H), 1-methyl-2-(tolylazo)imidazole (Tai-Me) and 1-ethyl-2-(tolylazo)imidazole (Tai-Et) to give complexes of the type [(η 6-arene)RuCl(RaaiR′)]+. The complexes were characterized by FTIR and 1H NMR and 13C {1H} NMR spectroscopy. The molecular structure of [(η 6-p-cymene)RuCl(Me-C6H4-N=N-C3H2N2-1-CH3)]PF6 was established by single-crystal X-ray diffraction methods.

Di-μ-chlorido-bis[chlorido(η5-pentamethylcyclopentadienyl)rhodium(III)] chloroform trisolvate

In the title dinuclear rhodium complex, [Rh2(C10H15)2Cl4]·3CHCl3, there are two independent centrosymmetric dinuclear complexes per unit cell.