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

• Published in: Inorganica Chimica Acta Vol. 457; pp. 150 - 159
• Main Authors: Afkhami, F.A., Khandar, A.A., White, J.M., Guerri, A., Ienco, A., Bryant, J.T., Mhesn, N., Lampropoulos, C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2017; Elsevier Science Ltd
• Subjects: Anions; Cadmium; Chemical synthesis; Coordination polymers; Imines; Infrared spectroscopy; Ligands; Network formation; Polymers; Single crystals; Steric hindrance; Van der Waals forces; X-ray diffraction
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2016.12.009

The investigation of 2-acetyl-pyridine-isocotinoylhydrazone in Cd(II) chemistry is reported. Four different coordination polymers were produced from the anion dependence study. The coordination and bridging ability of the hydrazone ligand is crucial in the assembly of the resulting coordination networks. The chelate/bridging capacity of the ancillary ligands was also found to be a key factor for the structural diversity of the resulting materials. [Display omitted] 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−, N3−, SCN−). The products {[Cd2(L)2(CH3COO)2]·C2H5OH}n (1), {[Cd1.5(L)(CH3COO)(N3)(H2O)]·C2H5OH}n (2), {[Cd(HL)(SCN)2]·CH3OH}n (3) and [Cd3(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–NC–O) while in compounds 3 and 4 it coordinates in its neutral keto form (N–NH–CO). 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.