Luminescent cadmium 1,3-adamantanedicarboxylate coordination polymers with diverse topologies depending on dipyridylamide ligands

Abstract

Hydrothermal reaction of cadmium nitrate, 1,3-adamantanedicarboxylic acid (adcH2), and a hydrogen-bonding capable dipyridylamide ligand afforded five crystalline coordination polymers whose dimensionality depends on the dipyridylamide length and nitrogen donor disposition. The five new phases were structurally characterized via single-crystal X-ray diffraction. [Cd(adc)(4-pmina)]n (1, 4-pmina=4-pyridylmethylisonicotinamide) displays a (4,4) grid topology with [Cd(adc)]n chains pillared by the dipodal dipyridylamide ligands. {[Cd(adc)(4-pmna)(H2O)]·4H2O}n (2, 4-pmna=4-pyridylmethylnicotinamide) displays a similar layered topology, but with octameric water molecule clusters residing in the interlamellar regions. {[Cd(adc)(3-pna)(H2O)]·6H2O}n (3, 3-pna=3-pyridylnicotinamide) possesses 1-D ribbon submotifs due to the syn-conformation and shorter tether length of the dipyridylamide ligands. Compound 3 entrains intriguing “infinite” water molecule tapes comprised of 4- and 5-membered rings. {[Cd2(adc)2(3-pina)2]·H2O}n (4, 3-pina=3-pyridylisonicotinamide) manifests a 4-connected 3D 658cds topology. The minor coordination polymer chain product {[Cd(adc)(3-pyram)2(H2O)]·2H2O}n (5) was isolated along with 4 (3-pyram=3-pyridylamine). Luminescent behavior in 1–4 is attributed to intra-ligand molecular orbital transitions. The new phases were also surveyed for the ability to detect nitrobenzene in ethanol suspension. Thermal decomposition behavior is also discussed herein.