Identification of a robust and reproducible noncluster-type SBU: effect of coexistent groups on network topologies, helicity, and properties

The present work is part of our ongoing quest for a robust and reproducible noncluster-type secondary building unit (SBU) using pyrazole based ditopic ligands and benzene polycarboxylic acids. We report here the construction of a series of Zn(II) coordination polymers using a tailor-made SBU, designed with the proper utilization of the hydrogen bonds of a pyrazole-based ligand 4,4'-methylene-bispyrazole (H2MBP) and isophthalic acid (H(2)IPA), and its derivatives (R-H(2)IPA; R = OH, OCH3, CH3, tBu, Br, I, NH2, N-3). The results demonstrate that the substituent effect of R-isophthalates does play a decisive role in directing the structural assemblies of this system. One of the promising features of the 2D networks of this series is the presence of SBU-based helical motifs, which by and large remain elusive despite the plethora of reports on various SBU based networks. Throughout the series, hydrogen bonds, p-p interactions and other intermolecular interactions play a crucial role in stabilizing the resulting networks. Furthermore, some of these complexes exhibit some interesting photoluminescent properties in the solid state.