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, [Ti6(μ3-O)2(μ2-O)2­(O3P-Phen)2(OiPr)10(1-hbta)2] (PTC-37), Ti8(μ3-O)2(μ2-O)2­(O3P-Phen)2­(OiPr)16(adn)2(NO3)2] (PTC-38), [Ti4(μ3-O)­(μ2-O)­(μ2-OiPr)2(OiPr)4­(O3P-Phen)3(1,10-phn)]­(HOiPr) (PTC-39), [Ti4(μ3-O)­(μ2-OiPr)3­(OiPr)5(O3P-Phen)3(Im)] (PTC-40), [Ti4(μ3-O)­(μ2-OiPr)3­(OiPr)5(O3P-Phen)3(Im)]­[Ti3M­(μ3-O)­(μ2-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.