Ryabov Alexander D, Le Lagadec Ronan, Estevez Hebert, Toscano Ruben A, Hernandez Simon, Alexandrova Larissa, Kurova Viktoria S, Fischer Andreas, Sirlin Claude, Pfeffer Michel
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA.
Inorg Chem. 2005 Mar 7;44(5):1626-34. doi: 10.1021/ic048270w.
Redox potentials of photosensitive cyclometalated RuII derivatives of 2-phenylpyridine or 2-(4-tolyl)pyridine are controllably decreased by up to 0.8 V within several minutes. This is achieved by irradiation of the ruthena(II)cycles cis-[Ru(o-X-2-py)(LL)(MeCN)2]PF6 (2, X = C6H4 (a) or 4-MeC6H3 (b), LL = 1,10-phenanthroline or 2,2'-bipyridine). The cis geometry of the MeCN ligands has been confirmed by the X-ray structural studies. The sigma-bound sp2 carbon of the metalated ring is trans to LL nitrogen. Complexes 2 are made from [Ru(o-X-2-py)(MeCN)4]PF6 (1) and LL. This "trivial" ligand substitution is unusual because 1a reacts readily with phen in MeCN as solvent to give cis-[Ru(o-C6H4-2-py)(phen)(MeCN)2]PF6 (2c) in a 83% yield, but bpy does not afford the bpy-containing 2 under the same conditions. cis-[Ru(o-C6H4-2-py)(bpy)(MeCN)2]PF6 (2e) has been prepared in CH2Cl2 (74%). Studies of complexes 2c,e by cyclic voltammetry in MeOH in the dark reveal RuII/III quasy-reversible redox features at 573 and 578 mV (vs Ag/AgCl), respectively. A minute irradiation 2c and 2e converts them into new species with redox potentials of -230 and 270 mV, respectively. An exceptional potential drop for 2c is accounted for in terms of a photosubstitution of both MeCN ligands by methanol. ESR, 1H NMR, and UV-vis data indicate that the primary product of photolysis of 2c is an octahedral monomeric low-spin (S = 1/2) RuIII species, presumably cis-[RuIII(o-C6H4-2-py)(phen)(MeOH)2]2+. The primary photoproduct of bpy complex 2e is cis-[RuII(o-C6H4-2-py)(bpy)(MeCN)(MeOH)]+, and this accounts for a lower decrease in the redox potential. Irradiation of 2c in the presence of added chloride affords [(phen)(o-C6H4-2-py)ClRuIIIORuIVCl(o-C6H4-2-py)(phen)]PF6, a first mu-oxo-bridged mixed valent dimer with a cyclometalated unit. The structure of the dimer has been established by X-ray crystallography.
2-苯基吡啶或2-(4-甲苯基)吡啶的光敏环金属化RuII衍生物的氧化还原电位在几分钟内可控地降低了0.8 V。这是通过照射钌(II)环顺式-[Ru(o-X-2-py)(LL)(MeCN)2]PF6（2，X = C6H4 (a) 或4-MeC6H3 (b)，LL = 1,10-菲咯啉或2,2'-联吡啶）实现的。MeCN配体的顺式几何结构已通过X射线结构研究得到证实。金属化环的σ键合sp2碳与LL氮处于反位。配合物2由[Ru(o-X-2-py)(MeCN)4]PF6（1）和LL制备而成。这种“简单的”配体取代并不常见，因为1a在MeCN作为溶剂时很容易与菲咯啉反应，以83%的产率生成顺式-[Ru(o-C6H4-2-py)(phen)(MeCN)2]PF6（2c），但在相同条件下，联吡啶不能得到含联吡啶的2。顺式-[Ru(o-C6H4-2-py)(bpy)(MeCN)2]PF6（2e）已在CH2Cl2中制备（产率74%）。在黑暗中于MeOH中通过循环伏安法对配合物2c、e的研究分别揭示了RuII/III准可逆氧化还原特征，电位分别为573和578 mV（相对于Ag/AgCl）。对2c和2e进行一分钟的照射会将它们转化为新物种，氧化还原电位分别为 -230和270 mV。2c出现的异常电位下降是由于两个MeCN配体都被甲醇光取代。电子自旋共振（ESR）、1H核磁共振（NMR）和紫外可见（UV-vis）数据表明，2c光解的主要产物是八面体单核低自旋（S = 1/2）的RuIII物种，可能是顺式-[RuIII(o-C6H4-2-py)(phen)(MeOH)2]2+。联吡啶配合物2e的主要光产物是顺式-[RuII(o-C6H4-2-py)(bpy)(MeCN)(MeOH)]+，这解释了氧化还原电位下降较低的原因。在添加氯化物的情况下照射2c得到[(phen)(o-C6H4-2-py)ClRuIIIORuIVCl(o-C6H4-2-py)(phen)]PF6，这是第一个具有环金属化单元的μ-氧桥联混合价二聚体。二聚体的结构已通过X射线晶体学确定。
