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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.

To determine the optimal conditions for the stabilization of cationic zinc phthalocyanine (ZnPc4+) monomers within an aqueous medium, the adsorption behavior of ZnPc4+ on the surface of an anionic clay nanosheet was investigated. It was determined that ZnPc4+ could be adsorbed as a monomer on the surface of an anionic clay nanosheet dispersed in an aqueous medium, containing up to 0.9 ZnPc4+ per cationic exchange site on the clay nanosheet. It was observed that the concentration of ZnPc4+ monomers in the aqueous solution was negligible when the concentration of ZnPc4+ was low. When ZnPc4+ monomers – after having been adsorbed on the surface of the anionic clay nanosheet – were photoexcited by visible light (690 nm) in the presence of 9,10-antracenediyl-bis(methylene) dimolonoic acid (ADMA), the typical absorbance of ADMA at 398 nm decreased with an increase in irradiation time. This is indicative of the photogeneration of a singlet oxygen in aqueous ZnPc4+, due to a highly stabilized ZnPc4+ monomer on anionic clay nanosheet surface. The external quantum yield of decomposed ADMA in the presence of the anionic clay nanosheet colloid in aqueous medium was measured to be 2.62 × 10−5.

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.

Homo- and hetero-dinuclear nickel(II), copper(II), and oxidovanadium(IV) complexes of a Schiff-base-fused phthalocyanine (pc) with bulky substituents, 2,6-dimethylphenoxy and t -butyl groups, were prepared and characterized. The introduced salen-like Schiff-base unit was shown to affect the spectral feature based on the pc unit in the near infrared region, the Q band being widely split over 600–800 nm. A fairly large ferromagnetic interaction ( J = 6.0 cm −1 ) was observed for the Cu II (pc)–Cu II (salen) homo-dinuclear complex, while an antiferromagnetic interaction ( J = −3.2 cm −1 ) was observed for the Cu II (pc)–V IV O(salen) hetero-dinuclear complex.

Lantern-type dinuclear complexes, cis-[Ru2(4-Me-pf)2(O2CMe)2Cl] and trans-[Ru2(2,6-Et2-pf)2(O2CMe)2Cl] (4-Me-pf− = N,N′-bis(4-methylphenyl)formamidinate ion and 2,6-Et2-pf− = N,N′-bis(2,6-diethylphenyl)formamidinate ion), were prepared and characterized. The dinuclear structures with cis- and trans-arrangements of the bridging ligands were confirmed by the X-ray crystal structures as well as 1H NMR spectra (298 K) in CD2Cl2, where the proton signals were observed at widely spread positions δ = − 80 to 25 ppm. Variable-temperature magnetic moments (2–300 K) showed the existence of three unpaired electrons in dinuclear units with large D values (65 cm− 1 for cis-Ru2II,III and 90 cm− 1 for trans-Ru2II,III).

Oxidation of essentially pure intermediate-spin iron(III) porphyrinates such as ruffled Fe(T i PrP)ClO 4 and saddled Fe(OETPP)ClO 4 produces the corresponding six-coordinate iron(III) porphyrin(por) radical cations [Fe(Por )(ClO 4 ) 2 ], where T i PrP and OETPP are dianions of 5,10,15,20-tetraisopropylporphyrin and 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin, respectively. Spin–spin interactions in these complexes are very much different; while ruffled [Fe(T i PrP )(ClO 4 ) 2 ] exhibits no antiferromagnetic coupling, saddled [Fe(OETPP )(ClO 4 ) 2 ] does exhibit it. The difference in magnetic behaviors has been explained in terms of the deformation mode and electron configuration of these complexes.

There are two types of electron configuration, (dxy)2(dxz, dyz)3 and (dxz, dyz)4(dxy)1, in low spin iron(III) porphyrin complexes. In order to reveal how the electronic effect of substituents affects the electron configuration of low spin iron(III) porphyrin complexes, we have examined the 13C NMR, 1H NMR, and EPR spectra of a series of tetrabutylammonium (dicyano)[meso-tetrakis(p-substituted phenyl)porphyrinato]ferrate(III), [Fe(p-X–TPP)(CN)2]−Bu4N+, in both CD2Cl2 and CD3OD solutions. The chemical shifts of the meso carbon signals, which sharply reflect the electron configuration of low spin iron(III), have changed to a great extent depending on the electron-donating or electron-withdrawing ability of the para-substituent. The isotropic shifts of the meso-carbon signals of [Fe(p-X–TPP)(CN)2]−Bu4N+ are determined on the basis of the meso-carbon chemical shifts of the corresponding diamagnetic cobalt(III) complexes, [Co(p-X–TPP)(CN)2]−Bu4N+. The plots of the isotropic shifts against Hammett σp values have yielded good linear lines with the slopes, −22 and −69 ppm, in CD2Cl2 and CD3OD, respectively. On the basis of these results, we have concluded that the electron-withdrawing groups at the phenyl para-positions stabilize the (dxy)2(dxz, dyz)3 state while the electron-donating groups at the same positions stabilize the (dxz, dyz)4(dxy)1 state. The conclusion is further supported by the 1H NMR and EPR results.

An annulated dinuclear palladium(II) phthalocyanine complex ( 1 ) was synthesized and characterized. It was found that 1 worked as a photo-catalyst for the decomposition of 1,3-diphenylisobenzofuran (DPBF) in aerated toluene under the irradiation of the light in the near-infrared (NIR) region (λ > 780 nm).

Dynamic NMR study of a series of meso-[Co(TRP)(L)2]Cl, where R is an alkyl group and L is a substituted imidazole, has been carried out. While the complexes with unhindered imidazole show no splitting of the signals, those with bulky imidazoles exhibit change in line shape, indicating the hindered imidazole rotation. The activation free energy increases as R and/or L become bulkier. Based on the red-shifted Soret and Q bands in the UV-Visible and the downfield shifted imidazole protons in the 1H NMR spectra of these complexes as compared with the meso unsubstituted complexes, it is concluded that the deformation of the porphyrin ring slows down the rate of rotation of the coordinated ligand.