Valence Fluctionality of Trinuclear Ruthenium Complex Dimers

Ru_3(mu_3-O)(mu-CH_3CO_2)_6(CO)(L)(mu-L‘)Ru_3(mu_3-O)(mu-CH_3CO_2)_6(CO)(L)(L’=1，4-吡嗪，L=4-二甲氨基吡啶(1)，4-吡啶(2)，4-氰基吡啶(3)，或L‘=4，4’-联吡啶；L=4-二甲氨基吡啶(4)、吡啶(5)、4-氰基吡啶(6)。循环伏安分析表明，在1-5的氧化还原化学中，存在两个离散的可逆单电子还原，簇间电荷转移络合物被很好地定义。还原波的分裂E与三Ru团簇之间的电子耦合作用有关，从80 mV(5)到440 mV(1)。在6的情况下，还原波的分裂E是50 mV，没有定义簇间电荷转移络合物。在12,100 cm~(-1)~10，80…范围内，1-3的混合价态也显示出价间电荷转移带提供2180 cm^-1&gt；(1)到1310 cm^&lt；-1&gt；(3)范围内H_&lt；AB&gt；(3)的光谱估计。电子耦合的大小对n(CO)区1-6的单还原(-1)混合价态的红外光谱有很大的影响。在电子耦合相对较弱的情况下(4-6)，两个v(CO)带被清晰地分辨出来。在强电子耦合(1-3)的情况下，这些带展宽为单一的v(CO)吸收带。这些数据允许通过模拟(Bloch型方程)在9×10^&lt；11&gt；S^&lt；-1&gt；，5×10^&lt；11&gt；S^&lt；-1&gt；和约.1 x 10^&lt；11&gt；S^-1&gt；4，4‘-联吡啶桥联化合物4-6在-1混合价状态下表现出不受电子转移动力学强烈影响的红外线形。4的混合价态的速率常数接近用这种方法可以估计的下限，在1×10^&lt；10&gt；到1×10^&lt；11&gt；S^&lt；-1&gt；之间。较少

lntramolecular electron transfers within the mixed valence states of the ligand bridged hexaruthenium clusters Ru_3(mu_3-O)(mu-CH_3CO_2)_6(CO)(L)(mu-L')Ru_3(mu_3-O)(mu-CH_3CO_2)_6(CO)(L)(L' = 1,4-pyrazine ; L = 4-dimethyl-aminopyridine (1), pyridine (2), 4-cyanopyridine (3), or L' = 4,4'-bipyridine ; L = 4-dimethyl-aminopyridine (4), pyridine (5), 4-cyanopyridine (6) were examined. Two discrete and reversible single electron reductions are evident by cyclic voltammetry in the redox chemistry of 1 - 5, and the inter-cluster charge transfer complexes are well defined. The splitting of the reduction waves, E, is related to the electronic coupling H_<AB> between the triruthenium clusters, and varies from 80 mV for 5 to 440 mV for 1. In the case of 6, the splitting of the reduction waves, E, is < 50 mV and the inter-cluster charge transfer complex is not defined. The mixed valence states of 1 - 3 also exhibit intervalence charge transfer (ICT) bands in the region 12,100 cm^<-1> (1) to 10,80 … More 0 cm^<-1> (3) which provide spectroscopic estimates of H_<AB> in the range 2180 cm^<-1> (1) to 1310 cm^<-1> (3). The magnitude of the electronic coupling H_<AB> is found to strongly influence the IR spectra of the singly reduced (-1) mixed valence states of 1 - 6 in the n(CO) region. In the case of relatively weak electronic coupling (4 - 6), two v(CO) bands are clearly resolved. In the cases of strong electronic coupling (1 - 3), these bands broaden to a single v(CO) absorption band. These data allow the rate constants, kappa_c, for electron transfer in the mixed valence states of 1, 2, and 3 to be estimated by simulating dynamical effects (Bloch type equations) on v(CO) absorption bandshape at 9 x 10^<11> s^<-1>, 5 x l0^<11> s^<-1>, and ca . 1 x 10^<11> s^<-1>, respectively. The less strongly coupled 4,4'-bipyridine bridged complexes 4 - 6 exhibit IR lineshapes in the -1 mixed valence states that are not as strongly affected by electron transfer dynamics. The rate constant for the -1 mixed valence state of 4 is close to the lower limit that can be estimated by this approach, between 1 x 10^<10> and 1 x 10^<11> s^<-1>. Less