Cobalt(ii) coordination polymers constructed from bis(N-pyrid-3-ylmethyl)adipoamide and polycarboxylic acids: reversible structural transformation upon proton delivery and removal

Abstract

Hydrothermal reactions of cobalt(II) salts and bis(N-pyrid-3-ylmethyl)adipoamide (L) with various polycarboxylic acids in water and NaOH solutions afforded {[Co(L)_0.5(1,3,5-HBTC)(H₂O)]·H₂O}_n (1,3,5-H₃BTC = benzene-1,3,5-tricarboxylic acid), 1, {[Co_1.5(L)_1.5(1,3,5-BTC)(H₂O)₄]·4H₂O}_n, 2, [Co(L)(5-tert-IPA)(H₂O)₂]_n (5-tert-H₂IPA = 5-tert-butylbenzene-1,3-dicarboxylic acid), 3, and {[Co(L)(5-NH₂-IPA)]·H₂O}_n (5-NH₂-H₂IPA = 5-aminoisophthalic acid), 4, respectively, which have been structurally characterized by using single crystal X-ray crystallography. Complexes 1–3 display two-dimensional (2D) networks, showing bey, bex and hcb topologies, respectively, while complex 4 exhibits a three-dimensional (3D) framework with the xww topology (standard representation), which can be further simplified as the tfz-d topology (cluster representation), revealing the structure-directing roles of the substituent groups on the polycarboxylate ligands. Reversible structural transformation upon delivery and removal of H⁺ in 1 and 2 is observed, which can be ascribed to the various bonding modes of the benzene-1,3,5-tricarboxylate anions and the flexible nature of L.