Structural diversity, magnetic property, or luminescence sensing of Co(ii) and Cd(ii) coordination polymers derived from designed 3,3′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoic acid

Abstract

Five novel coordination polymers (CPs), formulated as {[Co₃(μ₄-cpboda)₂(μ_1,1-OH₂)₂(2,2-bipy)₂]·1.5DMF·2H₂O}_n (1), {[Co₃(μ₃-cpboda)₂(4,4′-bpy)₃(H₂O)₂]·4H₂O}_n (2), {[Co(μ₂-H₂cpboda)₂(1,4-bib)₃(H₂O)₂]·H₂O·DMF·1.5HCOOH}_n (3), [Cd(μ₃-Hcpboda)(1,4-bib)]_n (4), and {[Cd₃(μ₄-cpboda)₂(μ_1,1-OH₂)₂(phen)₂]·2DMF·1.5H₂O}_n (5) (H₃cpboda = 3,3′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoic acid, 2,2-bipy = 2,2-bipyridine, 4,4′-bpy = 4,4′-bipyridine, 1,4-bib = 1,4-di(1H-imidazol-1-yl)benzene, phen = 1,10-phenanthroline) have been synthesized under solvothermal conditions and characterized by elemental analyses (EAs), single-crystal X-ray diffraction analyses, X-ray powder diffraction analyses (PXRD), FT-IR spectra, and thermogravimetric analyses (TGAs). The structural analyses reveal that these complexes have four 2D coordinate polymers and one 3D framework, in which metal ions are in octahedral coordination geometries in 1–3 and 5, but seven-coordinated disordered pentagonal bipyramids in 4. Complexes 1 and 5 represent linear trinuclear [M₃(μ_1,1-OH₂)₂(μ_1,3-COO)₄] SBUs in 1 (M = Co(II)) and in 5 (M = Cd(II)) based on a 3,4,6-connected net with a point symbol (3²·4)₂(3²·8³·9)₂(3⁴·4²·8²·9⁴·10³) net, complex 2 exhibiting a (3-c)₂(4-c)(4-c)₂ 3D structure with the (5²·6·8²·9)₂(5²·6²·9²)(5²·6)₂ topology and complexes 3 and 4 having a novel 2D framework with the point symbol of (4⁴·6²). Magnetization analyses disclose the antiferromagnetic (AF) behaviors between Co(II) ions in complexes 1 & 3 and S = 3/2 (Co²⁺) spin Heisenberg chains with alternating magnetic sequences (F/F/AF)_n in 2. Fluorescence measurements indicate that 4 and 5 are promising luminescence sensors for the detection of CrO₄²⁻ and Cr₂O₇²⁻ anions in aqueous solution.