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.

Graphical abstractLuminescent cadmium camphorate coordination polymers with isomeric dipyridylamide ligands show different dimensionality and chirality depending on the specific isomer used during hydrothermal synthesis.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Cadmium camphorate coordination polymers with isomeric dipyridylamide ligands. ► 3-Pyridylnicotinamide affords 1-D chains with retention of d-camphorate chirality. ► 3-Pyridylisonicotinamide affords 2-D layers with racemization of camphorate chirality. ► Higher thermal stability for 2-D compound. ► Both emit blue-violet light upon ultraviolet excitation.