Two intra-molecular inter-ligand C(aromatic)–<f>H⋯O</f>(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 <f>[Cu(IDA)(pza)(H2O)]·H2O</f>

Aqua(pyrazine-2-carboxamide)(iminodiacetato)copper(II) monohydrate, <f>[Cu(IDA)(pza)(H2O)]·H2O</f>, was synthesised and characterised by thermal, spectral, magnetic and X-ray diffraction methods. Its crystal structure was solved to a final <f>R1=0.058</f>. The Cu(II) atom exhibits a square base pyramidal coordination (type <f>4+1</f>) 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 <f>[Cu(pza)2(ClO4)2]</f> or <f>[Cu(acac)(pza)(ClO4)]·H2O</f>. 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)–<f>H⋯O</f> (IDA) interactions. [Copyright &y& Elsevier]