Activation of Small Molecules Mediated by Photoredox reactions of Metal Complexes

制备了Tri-mu-oxobis(tetraphenylporphinatoniobium(V))，络合物1。用可见吸收光谱研究了醇、酚和氮碱在1的轴位上的配位行为。醇和酚在轴位配位为1，生成单核配合物[Nb(TPP)(O)(L)(HL)]，2.邻苯二酚作为双齿配体，生成一个配合物[Nb(TPP)(O)(HCAT)]，3.2，6-二叔丁基苯酚和氮碱不配位为1。在单齿配体如醇或酚的存在下，化合物1在可见光照射下被还原。在苯酚存在的情况下，1的有氧照射产生了超氧化物络合物，而在醇存在的情况下，有氧照射没有检测到这样的络合物。络合物3在好氧和厌氧条件下均不发生辐射反应。在未加配体的苯中，络合物1在有氧照射下形成超氧化物络合物，但在厌氧照射条件下不被还原。1的苯溶液在厌氧条件下脉冲照射后，由于三重态双自由基而显示出时间分辨的ESR信号。在好氧条件下，三重态物种激活了共存的分子氧。在厌氧脉冲照射下，络合物2产生相应的苯氧基。没有配位到1的添加剂在厌氧照射下不产生瞬时自由基物种。配位到1的添加剂的活化是通过轴向配位键的均裂来启动的。

Tri-mu-oxobis(tetraphenylporphinatoniobium(V)), complex 1, was prepared. Coordination behaviors of alcohols, phenols and nitrogen bases at the axial sites of 1 were followed by means of visible absorption spectroscopy. Alcohols and phenols coordinated to 1 at the axial site and resulted mononuclear complexes, [Nb(tpp)(O)(L)(HL)], 2. Catechol acted as a bidentate ligand and afforded a complex, [Nb(tpp)(O)(Hcat)], 3.2,6-di-t-butylphenol and nitrogen bases did not coordinate to 1.The complex 1 in benzene was reduced upon anaerobic irradiation with visible light in the presence of monodentate ligands such as alcohols or phenols. Aerobic irradiation of 1 gave superoxide complexes in the presence of phenols, while no such complexes were detected upon aerobic irradiation in the presence of alcohols. The complex 3 did not react upon irradiation under the both aerobic and anaerobic conditions. The complex 1 in benzene without addition of ligands gave a superoxide complex upon aerobic irradiation, but it was not reduced upon anaerobic irradiation conditions.A benzene solution of 1 showed a time resolved ESR signal due to a triplet biradical after pulsed irradiation under anaerobic conditions. The triplet species activated the coexisting molecular oxygen under aerobic conditions. The complex 2 gave corresponding phenoxyl radical upon anaerobic pulsed irradiation. The Additives which did not coordinated to 1 did not give transient radical species upon anaerobic irradiation. The activation of the additives coordinating to 1 was initiated by homolysis of the axial coordination bond.