Pamoic acid in forming metallo-organic framework: Synthesis, characterization and first crystal structure of a dimeric Ti(IV) complex

Abstract

Two novel dinuclear Ti(IV) complexes of the ligand, 4,4'-methylene-bis (3-hydroxy-2-naphthalene carboxylic acid) (H(4)L) or pamoic acid having compositions, [(HL)(2)Ti(2)(mu-O)(DMF)(2)]center dot(DMF)(6) (1) and [(L)(2)Ti(2)(mu-O)(DMF)(2)]center dot(DMF)(4)(4,4'-Bipy-2H)(H(2)O),(2) have been synthesized and characterized by analytical and spectral methods and the structure has been established by single crystal XRD. Unlike the reported polymeric structures observed in case of H(4)L or pamoic acid, the anti-conformation of H(4)L changes to syn - orientation to avoid poly-metallic complex formation, as noticed in 1 and 2. The dimeric Ti(IV) units stack in the lattice to form helical columns and the space between the adjacent columns is being filled by the solvent molecules in 1 and solvent plus the protonated 4,4'-bipy in the lattice of 2 and thus the neighbor columns are connected through weak interactions. (c) 2009