Coordinated imidazolyl group site-directed assembly of Cd(II) coordination polymers based on tri-imidazolyl ligands

Abstract

Solvothermal reactions of CdCl2·2.5H2O and 1,4-benzenedicarboxylic acid (1,4-H2bdc) with 1,3-bis(1-imidazolyl)-5-[2-(1-imidazolyl)-phenoxymethyl]-benzene (otim), 1,3-bis(1-imidazolyl)-5-[3-(1-imidazolyl)-phenoxymethyl]-benzene (mtim) or 1,3-bis(1-imidazolyl)-5-[4-(1-imidazolyl)-phenoxymethyl]-benzene (ptim) at 150 °C gave rise to three cadmium(II) coordination polymers [Cd3(1,4-bdc)3(otim)2(H2O)]n (1), {[Cd(1,4-bdc)(mtim)]·0.5H2O}n (2) and {[Cd(1,4-bdc)(ptim)]·1.5H2O}n (3). Complexes 1–3 were characterized by elemental analysis, IR, powder X-ray diffraction, and single-crystal X-ray diffraction. In Compound 1, 3D [Cd(otim)]n units are reinforced by 1D helical chains [Cd(1,4-bdc)]n, resulting in 3-fold interpenetrating 3D framework. Compound 2 exhibits a 4-fold interpenetrating 3D framework formed by linking ladderlike [Cd(mtim)]n units with two pairs of 1,4-bdc bridges. Compound 3 can be considered as a 2-fold interpenetrating 3D pillared-layer framework in which 2D [Cd(ptim)]n layers are interconnected by 1,4-bdc pillars. The Schläfli symbols for these three 3D nets are (5·102)(5·7·82·102) (1), (42·6)(42·65·83) (2), and (63)(69·8) (3). The formation of 1–3 provided an interesting insight into coordinated group site effect on the construction of Cd(II)/tri-imidazolyl/dicarboxylate CPs under solvothermal conditions. The solid state luminescent properties of 1–3 at ambient temperature were also investigated, and 3 showed a high selectivity and sensitivity for acetone because of the quenching effect.