Co(ii) coordination polymers supported by a benzenetetracarboxylate and bis-pyridyl-bis-amides with different flexibilities

Abstract

Hydrothermal reactions of Co(CH₃COO)₂·4H₂O and 1,2,4,5-benzenetetracarboxylic acid (1,2,4,5-H₄BTEC) with N,N′-bis(3-methylpyridyl)oxalamide (L¹), N,N′-bis(3-methylpyridyl)adipamide (L²) and N,N′-bis(3-methylpyridyl)sebacamide (L³) afforded [Co(L¹)_0.5(1,2,4,5-BTEC)_0.5(H₂O)]_n, 1, {[Co(L¹)(1,2,4,5-BTEC)_0.5(H₂O)]·H₂O}_n, 2, {[Co(L¹)_1.5(1,2,4,5-BTEC)_0.5(H₂O)]·3H₂O}_n, 3, [Co(L²)(1,2,4,5-BTEC)_0.5(H₂O)₂]_n, 4, and [Co₃(L³)(1,2,4,5-BTEC)_1.5(μ₂-OH₂)₂]_n, 5, which have been structurally characterized by using single crystal X-ray crystallography. Complexes 1, 3 and 5 are 3D frameworks with (4⁴·6²)(4⁶·6⁴)₂(4⁸·6⁶·8)-4,5,6T11, (6⁵·8)-dmp and (3·5²)₂(3¹²·4³⁴·5²⁰·6⁵²·7·8)(3²·4²·5²)₂ topologies, whereas 2 and 4 are 2D layers with (4·6²)₂(4²·6²·8²)-bex and (3²·8·9²·10)₂(3²·8⁴)-4,4L88, topologies, respectively. The different structural types and the rare 4,4L88 and unique (3·5²)₂(3¹²·4³⁴·5²⁰·6⁵²·7·8)(3²·4²·5²)₂ topologies demonstrate that combination of the flexible bis-pyridyl-bis-amides and the benzenetetracarboxylate ligand under suitable conditions may lead to the formation of complexes with interesting structural diversity. Evaluation of the structural transformations for 1–3 reveals the reversibility and selectivity for 3 and its desolvated counterpart upon water removal and adsorption, indicating the governing role of porosity.