Metal ion binding patterns of acyclovir: molecular recognition between this antiviral agent and copper(II) chelates with iminodiacetate or glycylglycinate

In order to deepen on metal-binding patterns of acyclovir (acv), {Cu(IDA)(acv)]·2MeOH}_n (1) and Cu(glygly)(acv)]·H₂O (2) compounds have been synthesized and investigated by X-ray crystallography as well as spectral and thermal methods. These compounds have been chosen upon the assumption that iminodiacetate (IDA) and glycylglycinate (glygly) chelating ligands would bind copper(II) with mer-tridentate conformation, supplying two terminal H-acceptor carboxylate groups (IDA) or one H-acceptor carboxylate and one H-donor primary amino group (glygly). The main aim of this work was to clarify if the amino group of glygly can build an intra-molecular interligand H-bonding interaction to reinforce the Cu―N7(acv) bond. Our results are discussed in the context of an up-to-date critical look regarding the related structural information. From the viewpoint of molecular recognition, the structure of 1 shows that the chelate-nucleoside recognition only involves the Cu―N7(acv) coordination bond. In contrast, the molecular complex of 2 exhibits the Cu―N7(acv) coordination bond reinforced by an intra-molecular (glygly)N-H···O6(acv) interaction (2.961(3) Å, 140.5°).