Supramolecular architectures and photoluminescent properties of triethanolammonium 4-nitrobenzoate salt and its Ni(II) complexes

Abstract

Single crystals of new organic salt (HTEA)(4NB) (1) and its different types of Ni(II) complexes obtained from the same system NiCl2-compound 1 under various experimental conditions: [Ni(4NB)(TEA)(H2O)](4NB) (2), [Ni(4NB)(TEA)(H2O)](4NB)∙H2O (3), [Ni(TEA)2](4NB)2 (4) and Ni(BIC)2 (5), where TEA = triethanolammine, 4NB = 4-nitrobenzoate and BIC = N,N-bis(2-hydroxyethyl) glycinate, were successfully synthesized and structural characterized by FTIR spectroscopy and single crystal X-ray analysis. All new compounds represent supramolecular systems assembled by combining two or three organizing forces: metal-coordination (2–5), hydrogen bonds (1–5) and π-π stacking interactions (1–4). In compounds 2 and 3 the Ni(II) atom has an identical NO5 environment, while in complex 4 and 5 the metal centres have a N2O4 coordination core. The ionic coordination complexes 2–4 are arranged into 2D hydrogen-bonding layers and further assembled via π-π stacking interactions in supramolecular 3D network structures, while complex molecules of 5 are organized into a hydrogen-bonded network. This study emphasizes the first structurally characterized binary glycinate Ni(II) complex obtained from NiCl2·6H2O-(HTEA)(4NB) system. Comparative solid-state photoluminescent study of four Ni(II) coordination compounds and initial organic salt reveals a correlation between crystal structure/packing and luminescent properties.