Controlling interpenetration in CuCN coordination polymers by size of the pendant substituents of terpyridine ligands

Abstract

To systematically investigate the effect of the pendant groups of ligands on the assembly of coordination polymers (e.g, controlling interpenetration), four terpyridine ligands with bulky pendant groups, namely, 4′-(4-tolyl)-4,2′:6′,4′′-terpyridine (L1), 4′-(4-ethylphenyl)-4,2′:6′,4′′-terpyridine (L2), 4′-(4-isopropylphenyl)-4,2′:6′,4′′-terpyridine (L3), and 4′-biphenyl-4,2′:6′,4′′-terpyridine (L4) have been synthesized for comparative purposes. The reactions of CuCN and L1–L4 under the same solvothermal conditions provided four CuCN coordination polymers: [(CuCN)₂L1]_n (1), [(CuCN)₂L2]_n (2), [(CuCN)₂L3]_n (3), and {[(CuCN)₃L4_1.5]·H₂O}_n) (4), respectively. Single-crystal X-ray analyses reveal that compounds 1–3 are isostructural with the same topological 4-fold interpenetrated 3D CuCN networks, and compound 4 is a non-interpenetrated CuCN network. This success demonstrates that the interpenetration is suppressed by the alteration of the size of the pendant groups of terpyridine ligands.