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The cationic Ga(III) and Zn(II) phthalocyanines carrying N-methyl-pyridinium groups at eight peripheral β-positionshave been synthesized. These complexes are highly soluble in dimethyl sulfoxide (DMSO) and moderately soluble in water and phosphate buffered saline (PBS); both Ga(III)Cl and Zn(II) complexes have shown no aggregation in water up to 1.2 × 10−4 and 1.5 × 10−5 M, respectively. A higher water-solubility of Ga(III)Cl complex as compared to Zn(II) complex is ascribed to the presence of an axially coordinated chloride. The spectroscopic properties, photogeneration of singlet oxygen (1O2), and cytotoxicity of these complexes have been investigated. The absolute quantum yields (ΦΔabsolute) for the photogeneration of singlet oxygen using Ga(III)Cl and Zn(II) complexes have been determined to be 4.4 and 5.3%, respectively, in DMSO solution. The cytotoxicity and intracellular sites of localization of Ga(III)Cl and Zn(II) complexes have been evaluated in human HEp2 cells. Both complexes, localized intracellularly in multiple organelles, have shown no cytotoxicity in the dark. Upon exposure to a low light dose (1.5 J/cm2), however, Zn(II) complex has exhibited a high photocytotoxicity. The result suggests that Zn(II) complex can be considered as a potential photosensitizer for Photodynamic therapy (PDT).

Pyrrocorphin is an air-sensitive porphyrinoid with a highly reduced hexahydroporphyrin core. In contrast, pyrrolidine-fused pyrrocorphin (Pyr) obtained by successive 1,3-dipolar cycloaddition reactions of azomethine ylide to 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin is less air-sensitive. In order to reveal the effect of highly reduced porphyrin rings on the physicochemical properties of their metal complexes, we have prepared diamagnetic (S=0) Ni(II) complex Ni(II)(Pyr). The addition of excess pyridine (Py) to the toluene solution of Ni(II)(Pyr) yielded five-coordinate Ni(II)(Pyr)(Py), which was then completely converted to six-coordinate paramagnetic (S=1) Ni(II)(Pyr)(Py)2. The latter was characterized by UV-Vis, 1H NMR, CV, SQUID, and X-ray crystallography as well as DFT calculations. As compared with analogous complexes of porphyrin (Por), chlorin (Chl), and isobacteriochlorin (Iso) reported by Herges and co-workers (R. Herges et al., Inorg. Chem. 2015), Ni(II)(Pyr)(Py)2 has longer equatorial NiN and shorter axial NiN bonds. The CV study has shown a large decrease in HOMO-LUMO gap as the reduction of porphyrin ring proceeds, which has further been confirmed by UV-Vis and DFT calculation. Titration studies using 1H NMR and UV-Vis have shown that the first binding constant of pyridine toward Ni(II)(Pyr) is ca. 4 times as large as that of Ni(II)(Iso) and ca 230 times as large as that of Ni(II)(Por). Thus, we have concluded that the binding constant of pyridine to Ni(II) porphyrinoid increases by the following order: Por

Dinuclear rhodium(I) complexes, [Rh(4-Me-pf) (cod)]2 (1), [Rh(3,5-Me2-pf) (cod)]2 (2), [Rh(4-Me-pf) (nbd)]2 (3), [Rh(3,5-Me2-pf) (nbd)]2 (4), and [Rh(2,6-F2-pf) (nbd)]2 (5), have been synthesized and characterized by X-ray structure analysis, 1H, 13C, and 19F NMR, UV–vis, ESI-TOF-MS, and elemental analysis. In these complexes, two rhodium atoms are bridged by two formamidinato ligands and each rhodium atom is coordinated by one chelating cod or nbd ligand to form an approximately square planar coordination structure with two nitrogen atoms and two double bonds. The Rh··Rh distances are in the range of 3.2668 to 2.9726 A, suggesting a direct bonding interaction between two rhodium atoms. Variable temperature NMR studies in CD2Cl2 solution have revealed that 1–5 exhibit a novel dynamic behavior, that is, an interconversion between two enantiomers. The activation parameters for racemization have been determined by the line shape analyses of the 1H and 19F NMR spectra taken at various temperatures. Variable temperature NMR studies have also revealed that the rotation rates of the four aryl groups around N–C(aryl) bonds are extremely different in each complex. The cyclic voltammetry study has shown that the oxidation potentials corresponding to Rh23+/Rh2+ are 0.41 V in the cod complexes (1 and 2) while those in the nbd complexes (3–5) have shown negative shift by ca. 0.2 V. The reasons for the difference in dynamic behaviors and redox properties among these complexes have been discussed.

Lantern-type dinuclear complexes, cis-[Ru2{3,5-(CF3)2-pf}2(O2CMe)2Cl] and [Ru2{3,5-(CF3)2-pf}3(O2CMe)Cl] (3,5-(CF3)2-pf− = N,N′-bis[3,5-bis(trifluoromethyl)phenyl]formamidinate anion), were prepared and characterized. The cis-(2:2) and (3:1) arrangements of the formamidinate and acetate bridging ligands around the Ru25+ core were confirmed by the X-ray crystal analysis as well as 1H and 19F NMR spectra (measured at 25 °C in CD2Cl2), where paramagnetic shifts were observed for the signals due to the unpaired electrons in the dinuclear core. Variable-temperature magnetic moments (2–300 K) showed the existence of three unpaired electrons in the dinuclear units with the large D values (60 cm−1 for the cis-(2:2) Ru25+ complex and 50 cm−1 for the (3:1) Ru25+ complex). The electronic state with S = 3/2 was also ascertained by the EPR spectra measured in solid at 4 K and in frozen toluene/dichloromethane solution at 15 K, absorption spectra in dichloromethane and cyclic voltammograms (CVs) in THF using tetra-n-butyl ammonium perchlorate (TBAP) as electrolyte.