No abstract

Two ruthenium(II) carbonyl complexes of porphycene, (carbonyl)(pyridine)(2,7,12,17-tetra-n-propylporphycenato)ruthenium(II) (1) and (carbonyl)(pyridine)(2,3,6,7,12,13,16,17-octaethylpor-phycenato)ruthenium(II) (2), have been structurally characterized by single-crystal X-ray diffraction analysis. Cyclic voltammetry has revealed that the porphycene complexes undergo multiple oxidations and reductions in dichloromethane and the reduction potentials are highly positive compared to porphyrin analogs. UV-light irradiation (400 nm or shorter wavelength region) of a benzene solution of 1 and 2 containing external pyridine leads to dissociation of the carbonyl ligand from the ruthenium(II) centers to give the corresponding bis-pyridine complexes. The identical reaction has been also studied for a porphyrin derivative (carbonyl)(pyridine)(2,3,7,8,12,13,17,18-octaethylporphyriato)ruthenum(II) (3). The first-order kinetic analysis has revealed that the photosubstitution of all of the compounds occurs in the order of 10-3 s-1 at 298 K but proceeds faster for complexes of porphycene (1 and 2) than that of porphyrin (3).

This paper reports synthesis and electrochemistry of six-coordinate ruthenium porphyrin isomers including six novel porphycene complexes with substituted pyridines in the axial positions, in which redox potential control of reversible RuII/RuIII processes is successfully achieved over a 0.7-V potential region by varying the axial ligands and tetrapyrrole ligand structure and substituents.

Green and yellow luminescent 4,4′‐dimethyl‐5,5′‐divinyl‐2,2′‐bipyrrole derivatives bearing ester and amide were synthesized from blue luminescent 5,5′‐diformyl‐4,4′‐dimethyl‐2,2′‐bipyrrole and diethyl malonate, 2,2‐dimethyl‐1,3‐dioxane‐4,6‐dione, 1,3‐dimethylbarbituric acid, and 1,3‐dihexylbarbituric acid under Knoevenagel condensation conditions. All the synthesized products clearly showed a red‐shifted π–π* transition absorption band in the visible region compared with the starting bipyrrole. Single‐crystal X‐ray diffraction analysis and 1H nuclear magnetic resonance (NMR) spectroscopy revealed that the carbonyl moiety interacts with NH to form an intramolecular hydrogen‐bonding. Out of the synthesized compounds, a Knoevenagel adduct of 1,3‐dimethylbarbituric acid showed fluorescence at 578 nm with an 88 % quantum efficiency in dichloromethane, which is the highest value for the bipyrrole system. The highly efficient yellow photoluminescence can be attributed to the rigid molecular structure of the compound. Density Functional Theory (DFT) calculation revealed that the rigid and planar structure is essential for the bathochromically shifted absorption and high photoluminescence quantum yield.