Three Co(II)-Coordination Polymers Based on 5-Tert Isophthalic Acid and Isomeric Bis(Imidazole) Ligands: Synthesis, Optical and Magnetic Properties

Abstract

Three new Co(II)-coordination polymers, namely {[Co<inf>3</inf>(µ<inf>3</inf>-tbip)(µ<inf>4</inf>-tbip)(µ<inf>4</inf>-tbip)(µ-H<inf>2</inf>O)(µ-obix)]·3H<inf>2</inf>O}<inf>n</inf> (1), [Co<inf>3</inf>(Htbip)(µ-Htbip)(µ<inf>4</inf>-tbip)(µ<inf>4</inf>-tbip)(H<inf>2</inf>O)(µ-mbix)]<inf>n</inf> (2) and [Co<inf>2</inf>(µ<inf>3</inf>-tbip)<inf>2</inf>(µ-pbix)]<inf>n</inf> (3) (tbip: 5-tert-butyl isophthalate, o, m, pbix: 1,X-bis(imidazol-1ylmethyl)benzene, X = 2, 3, 4) were systematically synthesized with H<inf>2</inf>tbip and isomeric bis(imidazole) linkers under hydrothermal conditions to investigate the influence of isomeric ligands on the structural diversity. They were characterized by elemental analysis, IR spectroscopy, single and powder X-ray diffractions. X-ray results showed that complexes 1 and 3 possessed 3D framework while complex 2 was 2D layer. In 1 and 2, trinuclear [Co<inf>3</inf>(COO)<inf>6</inf>(OH<inf>2</inf>)] and [Co<inf>3</inf>(COO)<inf>6</inf>] units were connected by tbip ligands to form 2D and 1D structures which were extended to form 3D and 2D structures by neutral ligands, respectively. Complex 3 was mutually interpenetrated each other to form 3D + 3D → 3D interpenetrated framework with crs/dia-e topology. In 2, tbip ligand displayed new coordination modes. Moreover, thermal, optical and magnetic properties of the complexes were also studied. © 2018 Elsevier Ltd