Structure and photochemical properties of (mu-alkoxo)bis(mu-carboxylato)diruthenium complexes with naphthylacetate ligands.
Two new dinuclear Ru(III) complexes containing naphthalene moieties, K[Ru2(dhpta)(mu-O2CCH2-1-naph)2] (1) and K[Ru2(dhpta)(mu-O2CCH2-2-naph)2] (2) (H5dhpta = 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid, naph-1-CH2CO2H = 1-naphthylacetic acid, naph-2-CH2CO2H = 2-naphthylacetic acid), were synthesized. Complex 2 crystallized as an orthorhombic system having a space group of Pbca with unit cell parameters a = 10.6200(5) A, b = 20.270(1) A, c = 35.530(2) A, and Z = 8. EXAFS analysis of 1 and 2 in the solid states and in solution clarified that the dinuclear structures of 1 and 2 were kept in DMSO solutions. Variable-temperature magnetic susceptibility data indicated that the two Ru(III) centers are strongly antiferromagnetically coupled as shown by the large coupling constants, J = -581 cm(-1) (1) and -378 cm(-1) (2). In the cyclic voltammograms of 1 and 2, one oxidation peak and two reduction peaks which were assigned to the redox reaction of the ruthenium moieties were observed in DMF. The large conproportionation constants estimated from the reduction potentials of Ru(III)Ru(III) and Ru(III)Ru(II) indicated the great stability of the mixed-valent state. The mixed-valent species [Ru(III)Ru(II)(dhpta)(mu-O2CCH2-R)2](2-) (R = 1-naph (6) and R = 2-naph (7)) were prepared by controlled potential electrolysis of 1 and 2 in DMF. The electronic absorption spectra of 6 and 7 were similar to that of [Ru(III)Ru(II) (dhpta)(mu-O2CCH3)2](2-) which is a typical Class II type mixed-valent complex. The fluorescence decay of 1 and 2 indicated that there are two quenching processes which come from the excimer and monomer states. The short excimer lifetimes of 1 and 2 were ascribed to the energy transfer from the naphthyl moieties to the Ru centers. The different excimer ratio between 1 and 2 suggested that the excimer formation is affected by the conformation of the naphthyl moieties in the diruthenium(III) complexes.
Nakai
Misaki
M
Division of Material Science, Graduate School of Humanities and Sciences, Nara Women's University, Kitauoyanishimachi, Nara 630-8506, Japan.
Funabiki
Takuzo
T
Ohtsuki
Chikara
C
Harada
Masafumi
M
Ichimura
Akio
A
Tanaka
Rika
R
Kinoshita
Isamu
I
Mikuriya
Masahiro
M
Benten
Hiroaki
H
Ohkita
Hideo
H
Ito
Shinzaburo
S
Obata
Makoto
M
Yano
Shigenobu
S
D004563:Electrochemistry; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008280:Magnetics; D008958:Models, Molecular; D008968:Molecular Conformation; D009280:Naphthaleneacetic Acids / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010777:Photochemistry; D012428:Ruthenium / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013237:Stereoisomerism; D013696:Temperature
D008024:Ligands; D009280:Naphthaleneacetic Acids; D009942:Organometallic Compounds; C020424:2-naphthylacetic acid; D012428:Ruthenium