Aqua[N-(2,5-dihydroxybenzyl)iminodiacetato]copper(II)

The title complex, [Cu(C11H11NO6)(H2O)], contains a CuII atom in a distorted square-pyramidal geometry. The metal centre is coordinated in the basal sites by one water molecule and two carboxylate O atoms and one N atom of the tetradentate ligand [Cu—O range, 1.9376 (11)–1.9541 (12), Cu—N, 1.9929 (12) Å] while the apical site is occupied by a hydroquinone O donor atom [Cu—O, 2.3746 (12) Å]. Intermolecular hydrogen bonding interactions involving both hydroquinone hydroxy groups and the coordinated water as donors give a three-dimensional framework structure.

Data collection: CrystalClear (Rigaku/MSC, 2005); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXL97; software used to prepare material for publication: CrystalStructure (Rigaku/MSC, 2005).   (Dooley et al., 1998), tissue formation (Wang et al., 1996), photosynthesis (Calvo et al., 2000) and aerobic respiration (Iwata et al., 1998). These compounds are involved in interesting organic electron-and hydrogen-transfer systems, e.g. electron-transfer reactions between transition metal centers and p-quinone cofactors are vital for all life (Drouza et al., 2002), occurring in key biological processes. As part of a series of the studies (Huang et al., 2008), we report here the synthesis and structure of the title compound, a new Cu II complex with the related ligand 2-[N,Nbis(carboxylatomethyl)aminomethyl]hydroquinone. The molecular structure of the title compound [Cu (C 11 H 11 NO 6 (I) is shown in Fig. 1. The Cu II atom has a distorted square-pyramidal geometry with a τ parameter of 0.09 (Addison et al., 1984). The basal sites are occupied by one water molecule, as well as two carboxylate O atoms and one N atom of the ligand.
In the apical position, the O atom of the hydroxybenzene coordinates to the Cu II atom. All bond distances and bond angles have normal values. The crystal packing of (I) (Fig. 2) involves intermolecular O-H···O hydrogen bonds (Table 1). The non-coordinated carboxylate O2 atom accepts intermolecular hydrogen bonds from the coordinated hydroxy O (O5) of the hydroquinone ligand and from the coordinated water (O7). The non-coordinated carboxylate O4 atom is also an acceptor for a water H donor in an intermolecular hydrogen bond. The coordinated atom O3 accepts a hydrogen bond from the noncoordinated hydroquinone O (O6). These interactions result in a three-dimensional hydrogen-bonded framework structure.

Experimental
The ligand 2-[N,N-bis(carboxylatomethyl)aminomethyl]hydroquinone was prepared according to a literature procedure (Fan et al., 1992). The title complex was synthesized by the addition of CuCl 2 .2H 2 O (0.0850 g, 0.5 mmol) to 20 ml of a methanol solution containing the ligand (0.1275 g, 0.5 mmol). The resulting solution was stirred for 3 h at 60°C, and then cooled and filtered. Blue single crystal blocks were isolated from the solution at room temperature over six days.

Refinement
H atoms on C atoms were positoned geometrically with C-H aromatic = 0.93 Å and C-H aliphatic = 0.97 Å and treated as riding with U iso (H) = 1.2U eq (C).
supplementary materials sup-2 Figures   Fig. 1. A view of the molecular structure of (I) with the atom-numbering scheme and 30% displacement ellipsoids.