Activation of Small Molecules Mediated by Photoredox reactions of Metal Complexes

制备了三氧化二氧（四苯基卟啉钠）配合物1。用可见吸收光谱法对1轴位上醇类、酚类和氮基的配位行为进行了研究。醇类和酚类在轴位与1配位，形成单核配合物[Nb(tpp)(O)(L)(HL)], 2。儿茶酚作为双齿配体，提供了一个配合物，[Nb(tpp)(O)(Hcat)], 3.2,6-二叔丁基苯酚和氮碱不配位于1。在单齿配体如醇或酚存在的情况下，苯中的配合物1在可见光厌氧照射下被还原。在苯酚存在的情况下，1的好氧照射产生超氧化物复合物，而在醇存在的情况下，好氧照射没有检测到这种复合物。配合物3在好氧和厌氧条件下辐照均不发生反应。未添加配体的苯中的配合物1在好氧照射条件下生成超氧配合物，在厌氧照射条件下不还原。1的苯溶液在厌氧条件下脉冲辐照后，由于三重态双自由基产生了时间分辨的ESR信号。三胞胎在好氧条件下激活了共存的分子氧。配合物2在厌氧脉冲照射下产生相应的苯氧基。与1不协调的添加剂在厌氧辐照下不产生瞬时自由基。与1配位的添加剂的活化是由轴向配位键的均裂引起的。

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.