Coordination polymers of various architectures built with mixed imidazole/benzimidazole and carboxylate donor ligands and different metal ions: syntheses, structural features and magnetic properties

Abstract

Ten coordination polymers {[Cd(L₁)₂]}_n (1), {[Cu(L₁)₂]}_n (2), {[Cd₂(L₁)₂(HCOO)₂(H₂O)]}n (3), {[Cd₂(L₁)4]·3H₂O}_n (4), {[Cd(L₁)(CH₃COO)]}_n (5), {[Cd(L₁)₂(C₅H₅N)]·2.5H₂O}_n (6), {[Zn(L₂)₂]}_n (7), {[Cd₂(L₂)₄]·H₂O}_n (8), {[Cd₃(L₂)₆(H₂O)]·2EtOH·H₂O}_n (9) and {[Cd(L₃)₂]·2DMF·4H₂O}_n (10), where HL₁ = 4-imidazole-1-yl-benzoic acid, HL₂ = 3-imidazole-1-yl-benzoic acid and HL₃ = 4-benzmidazole-1-yl-benzoic acid, have been synthesized under different experimental conditions. Their structures are determined by single-crystal X-ray diffraction analyses and further characterized by IR spectra, thermogravimetric (TG) and elemental analyses. The structure of 1 is a 2D → 2D (2D = two dimensional) interpenetrating network with (4,4) grid topology while 2 has an interesting Kagome structure. Compounds 4 and 6 crystallize in 4- and 3-fold interpenetrating diamondoid frameworks respectively. Compound 7 is a layered non-interpenetrating (4,4) grid network whereas 8 has an unprecedented self-penetrating structure with 2D framework. Compound 9 is a self-penetrating 3D structure while 10 crystallizes in a non-interpenetrating (4,4) square-grid with one-dimensional (1D) channels. From these results, it is demonstrated that the structures of the coordination polymers are strongly dependent on the geometry of L₁, L₂ and reaction conditions. Variable temperature magnetic susceptibility study of 2 has also been performed.