María del Pilar Brandi-Blanco

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)]·H(2)O (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°).

Two intra-molecular inter-ligand C(aromatic)–H⋯O(carboxyl) interactions reinforce the formation of a single Cu(II)–N4(pza) bond in the molecular recognition between pyrazine-2-carboxamide (pza) and the (iminodiacetato)copper(II) chelate. Synthesis, molecular and crystal structure and properties of [Cu(IDA)(pza)(H2O)]·H2O

Abstract Aqua(pyrazine-2-carboxamide)(iminodiacetato)copper(II) monohydrate, [Cu(IDA)(pza)(H 2 O)]·H 2 O, was synthesised and characterised by thermal, spectral, magnetic and X-ray diffraction methods. Its crystal structure was solved to a final R 1=0.058. The Cu(II) atom exhibits a square base pyramidal coordination (type 4+1) with IDA ligand in mer -tridentate configuration [Cu–N(aliphatic) 1.986(7), Cu–O(carboxyl) 1.933(6) and 1.938(5) A], the Cu–N4(pza) bond [1.984(7) A] and Cu–O(apical aqua) bond [2.347(8) A]. The N4-monodentate ligand role of pza is in contrast with that of the N , O -bidentate pza-Cu(II) chelation in [Cu(pza) 2 (ClO 4 ) 2 ] or [Cu(acac)(pza)(ClO 4 )]·H 2 O. In the molecular recognition between Cu(IDA) chelate and pza the Cu–N4(pyridine-like) coordination mode is preferred because it enables the additional contribution of two weak intra-molecular inter-ligand C(aromatic)–H⋯O (IDA) interactions.