Structural diversity of a series of coordination polymers built from 5-substituted isophthalic acid with or without a methyl-functionalized N-donor ligand

Abstract

The reaction of X-H₂BDC (X = H, Br, NO₂ and CH₃) and methyl-functionalized dmbpy ligands with metal salts under different solvent media conditions generates nine structurally diverse zinc(II)/cadmium(II)-based coordination polymers (CPs), {[Zn₂(BDC)₂(DMF)₃]·DMF}_n (1), [Zn(BDC)₂(dmbpy)]_n (2), {[(Me₂NH₂)₂Zn₃(Br-BDC)₄]·3DMF·3H₂O}_n (3), [Zn₂(Br-BDC)₂(dmbpy)]_n (4), {[Zn₁₃(NO₂-BDC)₈(μ₃-OH)₂(μ₂-OH)₆(H₂O)₄]·12H₂O·2NO₃}_n (5), [Zn₂(NO₂-BDC)₂(dmbpy)(H₂O)₂]_n (6), {[Cd(NO₂-BDC)(dmbpy)_0.5(H₂O)]·(ACN)·H₂O}_n (7), [Zn(CH₃-BDC)(dmbpy)_0.5(H₂O)]_n (8), and [Zn(CH₃-BDC)(dmbpy)_0.5]_n (9) (H₂BDC = isophthalic acid, Br-H₂BDC = 5-bromoisophthalic acid, NO₂-H₂BDC = 5-nitroisophthalic acid, CH₃-H₂BDC = 5-methylisophthalic acid, dmbpy = 2,2′-dimethyl-4,4′-bipyridine, DMF = N,N-dimethylformamide, ACN = acetonitrile). All the compounds are synthesized using dual linkers (X-H₂BDC and dmbpy). 1 and 7–8 show a 2D (4,4) network when dinuclear metal ions and ligands are regarded as nodes and linkers, respectively. 2 is a wave-like chain with BDC ligands alternately pointing up and down. CPs 3–6 and 9 all exhibit 3D networks with 5-connected sqp, 6-connected jsm, 6-connected pcu, (3,4)-connected dmc and 6-connected jsm topologies, respectively. Furthermore, luminescence, thermogravimetric and chemical stability properties of these CPs were investigated. The results suggest that both organic ligands and solvent media influence the final resulting CPs.