Unusual solvent-mediated hydrolysis of dicarboxylate monoester ligands in copper(ii) complexes toward simultaneous crystallization of new dicarboxylate derivatives

Abstract

A series of copper(II) complexes, [Cu(cmb)₂(im)₂] (1), [Cu(cmn)₂(im)₄] (3) and [Cu(cmp)₂(im)₂] (5), bearing various dicarboxylate monoester derivatives, [cmb = 2-carbomethoxy-benzoate; cmn = 8-carbomethoxy-naphthalene-1-carboxylate; cmp = 2-carbomethoxy-phenyl-2-benzoate], were generated from copper(II) acetate, imidazole (im) and an aromatic anhydride [phthalic, 1,8-naphthalic or biphenic anhydride for 1, 3 or 5, respectively]. Unusual solvent-mediated transformations of the crystals of two copper dicarboxylate monoester complexes to new crystals of the corresponding dicarboxylate derivatives by the hydrolysis of ester groups were observed and investigated. Crystals of 1 underwent a transformation to crystals of copper(II) phthalate 2D coordination polymer {[Cu₂(pht)₂(im)₄·H₂O]·H₂O}_n (2) (pht = phthalate) upon moistening with aqueous methanol. Similarly, crystals of 3, after wetting with aqueous dimethylformamide (DMF), were transformed to crystals of a metallacycle [Cu(nap)(im)(DMF)(H₂O)]₂ (4) (nap = 1,8-naphthalenedicarboxylate). In contrast to 1 and 3, the crystals of 5 were found to be stable under ambient conditions. Compounds 1–5 were characterized by IR and UV-vis spectroscopy and single crystal and powder X-ray diffraction. Topological analysis showed that in the 1→2 transformation the overall 2D network topology was modified from the 4-connected H-bonded sql net [Shubnikov tetragonal plane net] to the 3-connected metal–organic hcb net [Shubnikov hexagonal plane net/(6, 3)], whereas no topology change was detected during an analogous 3→4 transformation, with both structures exhibiting topologically equal H-bonded sql nets.