Control of chirality and catenation in cobalt and cadmium camphorate coordination complexes

Abstract

Hydrothermal reaction of either cobalt or cadmium nitrate, D-camphoric acid (H₂cam), and conformationally flexible dipyridylamide ligands produced five coordination networks which were structurally characterized by single-crystal X-ray diffraction. {[Co₂(DL-cam)₂(bdn)]·2H₂O}_n (1, bdn = N,N′-(butane-1,4-diyl)dinicotinamide) possesses {Co₂(OCO)₄} paddlewheel dimer-based [Co₂(DL-cam)₂] grid layers pillared by bdn ligands into a 6-connected 4¹²6³pcu network. In contrast, the cadmium analog {[Cd₂(D-cam)₂(bdn)₂]·5H₂O}_n (2) shows {Cd₂(OCO)₂} dimer-based [Cd₂(D-cam)₂] layers tethered by bdn ligands into an 8-connected 4²⁴6⁴bcu network. {[Co₂(D-cam)₂(pdn)]·2H₂O}_n (3, pdn = N,N′-(propane-1,3-diyl)dinicotinamide) manifests a self-penetrated 4⁴6⁸10 mab network in contrast to 1, and retains chirality. {[Cd₂(D-cam)₂(pdn)]·H₂O}_n (4) manifests {Cd₂(OCO)₄} paddlewheel dimer-based [Cd₂(D-cam)₂] grids, connected by exotridentate pbn ligands into a unique 3,7-connected 3D network with (3·5²)(3²4⁴5⁶6⁸7) topology derived from a rare non-self-penetrated 4⁹6⁶acs topology sublattice. {[Co₂(DL-cam)₂(pedn)]·2H₂O}_n (5, pedn = N,N′-(pentane-1,5-diyl)dinicotinamide) shows a hybrid structure of discrete slabs of 3D pcu network with interleaved 2D hxl (3,6) layers at random intervals, instead of the self-penetrated mab network seen in 3. The specific coordination environments and dipyridylamide lengths result in control of topology and self-penetration in this series of coordination networks. The cadmium complexes 2 and 4 were assayed for luminescent and nitrobenzene detection properties. Thermal properties of 1–5 are also discussed.