Donor disposition dependent dimensionality and in situ racemization in luminescent cadmium camphorate coordination polymers with dipyridylamide ligands

Hydrothermal reaction of cadmium nitrate, d-camphoric acid (H2d-cam), and either 3-pyridylnicotinamide (3-pna) or 3-pyridylisonicotinamide (3-pina) afforded coordination polymers whose dimensionality, topology, and chirality depend on the specific dipyridylamide isomer used. [Cd(d-cam)(3-pna)(H2O)2]n (1) displays a simple 1-D coordination polymer chain structure, anchored into a supramolecular 3-D lattice by inter-chain hydrogen bonding. In the case of the 3-pina dipyridylamide isomer, in situ racemization of d-cam occurred, producing [Cd(dl-cam)(3-pina)]n (2). Compound 2 has d-cam and l-cam ligands disordered over two sets of crystallographic positions. Compound 2 has 2-D (4,4) grid coordination polymer layer motifs in contrast to the 1-D structure of 1. Compounds 1 and 2 emit blue-violet light upon excitation with ultraviolet radiation, via π–π∗ molecular orbital transitions within the pyridyl rings of the dipyridylamide ligands. Thermal decomposition behavior is also discussed.