Assembly of anion-controlled cadmium(II) coordination polymers from the use of 2-acetyl-pyridyl-isonicotinoylhydrazone

Four Cd(II) coordination polymers have been synthesized, utilizing a tetradentate pyridine-based Schiff base ligand, namely 2-acetyl-pyridyl-isonicotinoylhydrazone (HL), and different anions (CH3COO-, N-3(-) SCN-). The products {[Cd-2(L)(2)(CH3COO)(2)].C2H5OH}(n) (1), {[Cd-1.5(L)(CH3COO)(N-3)(H2O)].C2H5OH}(n) (2), ([Cd(HL)(SCN)(2)].CH3OH}(n) (3) and [Cd-3(HL)(2)(SCN)(6)](n), (4), were characterized with single-crystal X-ray diffraction, IR spectroscopy, and luminescence studies. The ligand in 1 and 2 is singly-deprotonated and coordinates to the cadmium centre in the enolic form (=N-N=C-O) while in compounds 3 and 4 it coordinates in its neutral keto form (=N-NH-C=O). The tetradentate ligand in 2 acts as a linker and leads to the formation of a one-dimensional coordination polymer. The CH3COO- in 1 and SCN- in 3 and 4, further act as bridges, forming two-dimensional coordination polymers (1 and 3) and a three-dimensional network (4). Structural diversity is thus induced by the anions, due to the variable steric hindrance they impose as well as differing bridging capacity; metal-organic network formation is also evident via different Van der Waals forces. (C) 2016 Elsevier B.V. All rights reserved,