Divergent topologies in luminescent zinc and cadmium substituted isophthalate coordination polymers constructed from long-spanning dipyridylamide ligand precursors

Abstract

Hydrothermal reaction of zinc or cadmium nitrate, a 5-position substituted isophthalic acid, and the long-spanning dipyridylamide ligand N,N′-(hexane-1,6-diyl)dinicotinamide (hdn) resulted in coordination polymers whose dimensionalities depend on the nature of the ring substituent and the metal coordination environment. The six new phases were characterized by single crystal X-ray diffraction. {[Zn2(hip)2(H2O)2(hdn)]·2H2O}n (1, hip=5-hydroxyisophthalate) shows a 1D ladder topology with [Zn(hip)(H2O)]n uprights spanned by disordered hdn rungs. {[Zn2(nip)2(hdn)2]·2H2O}n (2, nip=5-nitroisophthalate) displays a 1D ribbon motif with [Zn(nip)]n chains pillared by looped pairs of hdn ligands. [Zn3(tbip)2(nic)2]n (3, tbip=5-tert-butylisophthalate, nic=nicotinate) shows trimeric [Zn3(OCO)2] clusters connected into a 3D 8-connected 42464bcu net by tbip and in situ generated nic ligands. {[Cd2(ip)2(H2O)4(hdn)]·2H2O}n (4, ip=isophthalate) and {[Cd2(tbip)2(H2O)4(hdn)]·H2O}n (5) both show a ladder topology similar to that in 1. {[Cd(mip)(hdn)]·H2O}n (6, mip=5-methylisophthalate) manifests a 2D (4,4) grid topology based on linked dimeric [Cd2(OCO)2] units. Luminescent properties were probed; compounds 4 and 6 showed good ability to detect nitrobenzene in ethanol suspension.