Nickel(II) complexes self-assembled from hexamethylenetetramine and isomeric nitrobenzoates: Structural diversity and supramolecular features

Three new nickel(II)-hmt complexes [Ni(2-nbz)(2)(mu 2-hmt)(H2O)(2)](n) (1), [Ni(3-nbz)(2)(hmt)(2)(H2O)(2)]center dot 2(3-nbzH) (2) and [Ni(4-nbz)(2)(mu 2-hmt)(H2O)(2)](n) (3) bearing isomeric nitrobenzoates [2-nbz = 2-nitrobenzoate, 3-nbz = 3-nitrobenzoate, 4-nbz = 4-nitrobenzoate and hmt = hexamethylenetetramine] have been synthesised by self-assembly and crystallographically characterised. Compounds 1 and 3 are zigzag chain 1D polymers whereas complex 2 is a monomer. Various weak forces, i.e. -NO2-pi, pi-pi and CH-pi interactions play a key role in stabilizing the structures of 1, 2 and 3, which are further extended into the distinct 1D (2), 2D (1) or 3D (3) H-bonded networks via the intermolecular O-H center dot center dot center dot N (1-3) and O-H center dot center dot center dot O (3) interactions involving the H2O ligands and hexamethylenetetramine and/or nitrobenzoate moieties. The H-bonded 2D and 3D networks in 1 and 3 have been topologically classified as trinodal 3,4,6-connected or 3,4,4-connected nets with the 3,4,6L6 or sqc69 topologies, respectively. (C) 2014 Elsevier Ltd. All rights reserved.