Crystal growth of the copper coordination polymer CuCPP

Abstract

Copper coordination polymer Cu(II)-2,5-bis(pyrazol-1-yl)1,4dihydroxybenzene (CuCPP) is formed by bridging Cu 2+ ions by the bidentate hydroquinon-based ligand in infinite polymer chains. The magnetic system can be described by the Heisenberg spin 1 2 chain model. It seems to be possible to adjust gently the coupling between the spins by synthetic modification of the ligand that opens a wide possibility for crystal engineering of magnetic chain systems. The main problem in the crystal growth of 1D coordination polymers is the binding anisotropy. Strong covalent bonds bind the atoms along the polymer chain, whereas the coupling between the chains is much weaker. This leads usually to an extreme anisotropy of the growth rate. Various experimental approaches were developed for the crystal growth of the polymer. Depending on the experimental conditions, crystals of two types were grown. Needles of length up to 100 μm and plates of area up to 250×100 μm 2 are formed. Single-crystal structure refinement was made on one of the crystals of the latter type. Possible mechanisms of polymer crystallization and crystal morphology are discussed based on the crystal structure of the polymer.