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

Aqua(pyrazine-2-carboxamide)(iminodiacetato)copper(II) monohydrate, [Cu(IDA)(pza)(H2O)] . H2O, was synthesised and characterised by thermal, spectral, magnetic and X-ray diffraction methods. Its crystal structure was solved to a final R1 = 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) Angstrom], the Cu-N4(pza) bond [1.984(7) Angstrom] and Cu-O(apical aqua) bond [2.347(8) Angstrom]. 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)(ClO4)(2)] or [Cu(acac)(pza)(ClO4)] . H2O. 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. (C) 2002 Elsevier Science B.V. All rights reserved.