Azole Functionalized Polyoxo-Titanium Clusters with Sunlight-Driven Dye Degradation Applications: Synthesis, Structure, and Photocatalytic Studies

Six polyoxo-titanium clusters (PTCs) with varying nuclearities containing Ti-N bonds and heteronuclearity, namely, [Ti-6(mu(3)-O)2(mu(2)-O)(2)(O3P-Phen)(2)(OiPr)(10)(1-hbta)(2)] (PTC-37), Ti-8(mu(3)-O)(2)(mu(2)-O)(2)(O3P-Phen)(2)(OiPr)(16)(adn)(2)(NO3)(2)] (PTC-38), [Ti-4(mu(3)-O)(mu(2)-O)(mu(2)-OiPr)2(OiPr)(4)(O3P-Phen)(3)(1,10-phn)](HOiPr) (PTC-39), [Ti-4(mu(3)-O)(mu(2)-OiPr)(3)(OiPr)(5)(O3P-Phen()3)(Im)] (PTC-40), [Ti4(mu(3)-O)(mu(2)-OiPr)(3)(OiPr)(5)(O3P-Phen)(3)(Im)][Ti3M(mu(3)-O)(mu(2)-OiPr)(3)(OiPr)(3)(O3P-Phen)(3)(Im)] (M = Co for PTC-41 and M = Zn for PTC-42; O3P-Phen = phenyl phosphonate, 1-hbta = 1-hydroxy benzotriazolate, adn = adenine, 1,10-phn = 1,10-phenanthroline, Im = imidazolate, and OiPr = isopropoxide) were prepared as crystalline samples and structurally characterized. Simultaneous doping of nitrogen and transition metal heteroatoms into the Ti-O clusters created complex chemical environments in the resulting hybrid materials. Thus, photocatalytic methylene blue degradation studies were performed to understand structure-property relationships in these Ti cluster-based materials. The complex chemical environment created in these novel molecular clusters had proved to exhibit ligand-dependent photocatalytic activities under normal sunlight. Adenine-functionalized PTC-38 presented moderate activities, while other PTCs all show rapid dye degradation.