Isomerism in 1D Coordination Polymers of Cu(II) Complexes of N-(2-Hydroxybenzyl)-l-valine:  Influence of Solvent and Coordination Sphere on the Conformation

The reaction of the deprotonated N-(2-hydroxybenzyl)-l-valine ligand (“Sval”) with Cu(II) salts afforded [Cu2(Sval)2(H2O)3]n, 1, which has a 1D coordination polymeric structure cross-linked by strong hydrogen bonds to give 2D hydrogen-bonded coordination polymer in the solid state. Compound 1 can lose all the water molecules bonded to Cu(II) below 110 °C. However, recrystallization from aqueous solution of anhydrous 1 gave a supramolecular isomer, [Cu2(Sval)2(H2O)]n·2nH2O, 2. Interestingly, the thermal dehydration behavior of 2 is very similar to that of 1. Pseudo-supramolecular isomeric compounds of [Cu2(Sval)2(H2O)]n·0.5nC3H7OH, 3, and [Cu4(Sval)4(H2O)2(C4H9OH)]n·nC4H9OH, 4, were obtained when anhydrous 1 was recrystallized from 2-proponal and 1-butanol, respectively.