Masaoki Furue

Intramolecular energy transfer in covalently linked polypyridine rhenium(I)/ruthenium(II) complexes

Abstract A novel series of covalently-linked polypyridine Re(I)/Ru(II) binuclear complexes [LRe(I)(CO) 3 MebpyCH 2 CH(OH)CH 2 MebpyRu(II)(bpy) 2 ] (L = Cl, 4-methylpyridine, N-methylimidazole, or acetonitrile) 1 , has been synthesized. The emission spectra of 1 (excitation wavelength: 360 nm) showed a nearly complete quenching of Re I →π * (bpy) MLCT emission and the enhancement of Ru II →π * (bpy) MLCT emission. The rate constants (k en ) of the intramolecular energy transfer ranged from 1.7 × 10 8 to 1.2 × 10 9 s −1 . The relation between k en and the energy gap was discussed in terms of the energy gap law.

Synthesis and Photochemical Properties of Covalently-Linked Dimers of Ruthenium(II) Tris (Bipyridine) Complex: Comparison with Ru(II)(bpy)2 (Poly-4-Methyl-4′-Vinylbipyridine)

Abstract Covalently linked dimers of Ru(bpy)3 2+ (3 and 4) connected by two or three carbon atoms were synthesized as models for Ru(bpy)3 2+-containing vinyl polymer (1). The luminescence properties of 3 and 4 were compared with those of its component monomer, 4,4′-dimethyl-2,2′-bipyridine-bis(2,2′-bipyridine)ruthenium(II) complex (2). In excited 3 and 4, intramolecular interaction leading to enhanced quenching was not observed. Electron-transfer quenching of the excited dimer with methylviologen (MV2+) and the zwitterionic viologen, 1,1′-bis(3-sulfopropyl)4,4′-bipyridinium (SPV), was studied and compared with that of 1 and 2. The low quenching efficiency in 1, 3, and 4 systems can be ascribed to the steric hindrance of unexcited ruthenium complex. Energy migration between ruthenium complexes in the excited 1, 3, and 4 can be ruled out from the kinetic evidence.