engleski

Influence of experimental conditions on the crystallization of a Schiff base coper(II) complex

In our work, we have focused on the crystallization of a copper(II) complex with a Schiff base ligand (n5a2MePy) derived from 2-hydroxy-1-naphthaldehyde and 5-amino-2-methoxypyridine that has peripheral groups which are potential halogen and hydrogen bond acceptors [1, 2]. The Cu(n5a2MePy)2 metal complex has been synthesized by heating of a stoichiometric mixture of copper(II) acetate monohydrate and n5a2MePy in a mixture of acetonitrile and methanol. In order to prepare a single crystal we recrystallized the obtained product by dissolving it in acetonitrile. The prepared solution was allowed to evaporate at room temperature and after three days a single crystal was isolated. In the crystal structure of the Cu(n5a2MePy)2 complex metal-organic subunits are connected by a pair of weak C–H∙∙∙π hydrogen bonds (d(C∙∙∙C) = 3.52 Å, (C–H∙∙∙O) = 133°) and form antiparallel chains along the b crystallographic axis. The chains are connected by a pair of weak C–H∙∙∙Npyridine hydrogen bonds (d(C∙∙∙N) = 3.49 Å, (C–H∙∙∙O) = 140°). Crystallising Cu(n5a2MePy)2 from tetrahydrofuran with the addition of a stoichiometric amount of tetrafluoro-1, 4-diiodobenzene (tfib) yielded a porous framework of Cu(n5a2MePy)2 hemihydrate. In the hemihydrate structure, the Cu(n5a2MePy)2 molecules are interconnected through C–H∙∙∙Omethoxy hydrogen bonds (d(C∙∙∙O) = 3.48 Å, (C–H∙∙∙O) = 145°), leaving voids in the form of channels along the b crystallographic axis. The voids are filled by disordered water molecules forming hydrogen bonded chains. It is interesting to note that the hemihydrate could only be obtained under the above conditions – changing the solvent or omitting tfib led to the crystallisation of anhydrous Cu(n5a2MePy)2 only.

crystallization, Schiff base complex

nije evidentirano