catena-Poly[[[(oxamide dioxime-[kappa]²N,N')copper(II)]-[mu]-L-tartrato-[kappa]⁴O¹,O²:O³,O⁴] tetra­hydrate]: a chiral nanochannel framework hosting solvent water molecules

The crystal structure of the title compound, {[Cu(C₄H₄O₆)(C₂H₆N₄O₂)]·4H₂O}_n, contains the central Cu^II cation in a distorted octa­hedral coordination, symmetrically chelated by the two imine N atoms of a neutral oxamide dioxime (H₂oxado) ligand [Cu-N = 1.9829 (16) Å] and unsymmetrically bis-chelated by two halves of the L-(+)-tartrate(2-) (tart) ligands, each half being linked to the Cu^II cation via the deprotonated carboxyl­ate group and protonated hy­droxy group [Cu-O = 1.9356 (14) and 2.4674 (13) Å, respectively]. The extended asymmetric unit is defined by twofold axes, one passing through the Cu^II cation and the centre of the oxamide dioxime (H₂oxado) ligand and the another two (symmetry related) bisecting the central C-C bonds of the tartrate ions. The structure is chiral, consisting of enantio­meric linear-chain polymers oriented along [001], with virtual monomeric {Cu(tart_0.5)₂(H₂oxado)} repeat units and with the chains inter­leaved face-to-face into `twin pillars'. Nanochannels exist, running parallel to the c axis and bisecting a and b, which host `double strings' of solvent water mol­ecules. Extensive hydrogen bonding (O-H...O and N-H...O) between the chains and solvent water mol­ecules, together with extended [pi]-[sigma] inter­actions, consolidate the bulk crystal structure.