Spectroscopic and structural studies of 6-(1-methylbenzimidazol-2-yl)-1H-pyridin-2-one and of an unusual T4(2)7(2)6(2)7(2) water tape stabilized by the copper(II) coordination polymer

The solid-state structures of 6-(1-methylbenzimidazol-2-yl)-1H-pyridin-2-one (HL) and the copper(II) complex Cu(L⁻)₂(OH₂)]·2H₂O (1) are established by X-ray crystallography and also by means of physicochemical and spectroscopic methods. The molecules of HL form a self-complementary head-to-tail hydrogen-bonded dimer through C-H?N and C-H?O contacts to give an infinite 1D chain. The copper(II) complex (1) is five-coordinate with distorted trigonal-bipyramidal (TBP) geometry of the N₄O donor atoms. The electronic and EPR data are in agreement with the X-ray structure of 1, showing that HL coordinates to copper(II) centre as a mono-anionic ligand through deprotonated pyridone N atom and the tertiary benzimidazole nitrogen atom to form a neutral complex in which the water molecule occupies the fifth position. The 1D water tape, T4(2)7(2)6(2)7(2) is anchored to the host through hydrogen bonds between coordinated water molecule O(3w)] as acting double H-donor, pyridone carbonyl groups O(2) and O(1)] as double H-acceptor and the lattice water molecules O(4w) and O(5w)] as double H-donor and single H-acceptor).