Cadmium adipate coordination polymers prepared with isomeric pyridylamide precursors: pH-dependent in situ reaction chemistry and divergent dimensionalities

Abstract

Hydrothermal reaction of cadmium nitrate, adipic acid (H₂adp), and a pyridylnicotinamide precursor has afforded four new crystalline coordination polymer solids. The 1-D ribbon coordination polymer {[Cd₂(adp)(nic)₂(H₂O)₃(3-ampyr)]·5H₂O}_n (1, nic = nicotinate, 3-ampyr = 3-aminopyridine) resulted from in situ hydrolysis of the 3-pyridylnicotinamide (3-pna) precursor under basic conditions. Incipient voids within the crystal lattice of 1 contain T5(2)5(2)A(0) water molecule chains. Eschewing addition of extra base to the reaction mixture resulted in the isolation of the 3-D coordination polymer {[Cd₂(adp)(nic)₂(3-pna)₂]·6H₂O}_n (2), in which some of the 3-pna starting material remains intact. The underlying 5-connected 4⁶6⁴bnn 3-D network of 2 arises from the linkage of similar ribbon motifs to those observed in 1. Use of either 3-pyridylisonicotinamide (3-pina) or 4-pyridylnicotinamide (4-pna) precursors avoids any amide hydrolysis, affording the decorated (4,4) grid 2-D coordination polymer {[Cd(adp)(3-pina)]·H₂O}_n (3) or the 1-D chain compound {[Cd(adp)(4-pna)₂(H₂O)₂]·2H₂O}_n (4), respectively. Luminescent and thermal properties of these materials are also presented.