Cooperative Effect of 3,3′,4,4′-Benzophenonetetracarboxylic Acid and 1,10-Phenanthroline under Solvothermal Conditions to Afford Two Novel Zinc(II) and Cadmium(II) Complexes

Abstract

Rational self-assembly of a flexible ligand 3,3′,4,4′-benzophenonetetracarboxylic acid and d10 transition metal salts in the presence of rigid bidentate ligand 1,10-phenanthroline yields two novel helical coordination polymers with different structural motifs; i.e., [Zn(H2bbtc)(phen)2 · 2H2O] n (1) and [Cd2(bbtc)(phen)4 · 2.25H2O] n (2) (H4bbtc = 3,3′,4,4′-benzophenonetetracarboxylic acid, phen = 1,10-phenanthroline), under solvothermal condition. One is hydrogen bonded and π–π stacked together into a network, and the other is a covalently coordinated 3D framework. The coordination polymers were characterized by FT-IR, UV/VIS and fluorescent spectroscopy, single crystal X-ray diffraction, elemental analysis and differential thermal analysis/thermogravimetry (DTA/TG). The most intriguing structural feature is that each complex exhibits novel helical-spaced chains by reason of two different ligands coordinating to the metal centers. Additionally, compounds 1 and 2 showed good fluorescence properties compared to the free ligands.