Two-Dimensional Coordination Polymer with a Non-interpenetrated (4,4) Net Showing Anion Exchange and Structural Transformation in Single-Crystal-to-Single-Crystal Fashion

A new non-interpenetrated two-dimensional (2D) rectangular-grid coordination polymer, {[Co(L)2(H2O)2]·(BF4)2·4DMF}n (1), has been synthesized using a new rod-like ligand, 3,5-bis(4-imidazol-1-ylphenyl)-[1,2,4]triazol-4-ylamine (L). Weakly H-bonded BF4− anions present within the voids can be exchanged by ClO4− and NO3− anions to generate {[Co(L)2(H2O)2]·(ClO4)2·2DMF·2H2O}n (2) and {[Co(L)2(H2O)2]·(NO3)2·2DMF·2H2O}n (3) in single-crystal-to-single-crystal (SC-SC) manner. In the case of exchange by Cl− ion, the crystallinity is not maintained, and so it is proven by IR spectroscopy, PXRD, and elemental analysis. In addition, 3 shows an interesting structural transformation (2D → 1D) with bond rupture/formation leading to the formation of a new coordination polymer, {[Co(L)2(H2O)2]·(NO3)2·2DMF·H2O}n, (5), again in SC-SC fashion.