Water-mediated supramolecular architecture of Co(iii)–phenanthroline complexes: organizational control to 2D-layers and 3D-square cavities through substituted aryl carboxylate anions

Abstract

To explore the variation in the supramolecular architecture of cobalt(III)–1,10-phenanthroline–aryl carboxylate complexes in tune with aryl substitution, eight new supramolecular inorganic–organic framework complexes have been synthesized. These have the general formula [Co(phen)₂CO₃]L·nH₂O, where phen = 1,10-phenanthroline, L = 3-nitrobenzoate (P, Z = 2, n = 4; 1), 4-nitrobenzoate (P, Z = 2, n = 5; 2), 2-chloro-4-nitrobenzoate (P, Z = 2, n = 5; 3), 3-methyl-4-nitrobenzoate (P, Z = 2, n = 5; 4), 4-chlorobenzoate (P2₁/c, Z = 4, n = 7; 5), 2-iodobenzoate (P, Z = 2, n = 7; 6), 2-phenoxybenzoate (P, Z = 2, n = 8; 7) and 2-napthleneacetate (P2₁/c, Z = 4, n = 7; 8) and were unequivocally characterized by physicochemical methods, spectroscopic techniques and single crystal X-ray crystallography. Solubility, conductivity measurements and X-ray structure determination revealed the ionic nature of complexes 1–8. While the complexes 1–4, 7 and 8 prefer a 2D layer structure; the complexes 5 and 6 favor a 3D square cavity and in all these complexes, water molecules act as stabilizing linkers between anions and cations. The weak non-covalent interactions of the type O–H⋯O (carboxylate/water/carbonato), C–H⋯O (carboxylate/water/carbonato), π⋯π, C–H⋯π and anion⋯π interactions play a crucial role in stabilizing the crystal lattices.