Effect of substituent groups on the structures of two semi-flexible bis(imidazole) directed Zn(II)-5-sulfoisophthalate coordination polymers: Syntheses, structures and photoluminescent properties

Abstract

Two new metal organic architectures, formulated as {(pbetixH(2))(0.5)[Zn(mu-sip)(mu-pbetix)(0.5)]}(n) (1) and {[Zn-2(mu-sip)(2)(pbisopix)(pbisopixH)(2)]center dot 4H(2)O}(n) (2), were synthesized based on the rarely employed 1,4-bis((2-ethylimidazol-1-yl)methyl)benzene (pbetix) and 1,4-bis((2-isopropylimidazol-1-yl)methyl)benzene (pbisopix) ligands, along with the 5-sulfoisophthalate (sip) ligand. Complexes 1 and 2 were synthesized in basic medium and under mild hydrothermal conditions. Both complexes were characterized by elemental analysis, FT-IR spectroscopy and single crystal X-ray diffraction studies. Crystallographic studies of complexes 1 and 2 reveal that the Zn(II) ions are mu-bridged by trianionic sip(3-) ligands in the bis(monodentate) coordination mode to generate 1D polymer chains. In the complexes, adjacent chains are linked by the bis(imidazole) ligands to form a 2D structure. Complex 1 is the first example containing a protonated bis(imidazole) ligand, namely the pbetixH(2) cation, while complex 2 is the first example with a monoprotonated bis(imidazole) ligand, namely pbisopixH. Topological analyses of the 2D coordination polymers reveal that complex 1 is a 3-fold polycatenated 4-connected uninodal net with the point symbol of {4(4).6(2)}, whereas complex 2 is a 3-connected uninodal net with the point symbol of 63. The thermal behavior, photoluminescent properties and topological analysis of the complexes are also discussed herein. (C) 2017 Elsevier Ltd. All rights reserved.