A strongly fluorescent NiII complex with 2-(2-hy­droxy­eth­yl)pyridine ligands: synthesis characterization and theoretical analysis and comparison with a related polymeric CuII complex

摘要

The synthesis and characterization of di­aqua­bis­[2-(2-hy­droxy­eth­yl)pyridine-κ² N,O)nickel(II) dinitrate, [Ni(C7H9NO)2(H2O)2](NO3)2, under ambient conditions is reported and compared with catena-poly[[bis­[2-(2-hy­droxy­eth­yl)pyridine-κ² N,O]copper(II)]-μ-sulfato-κ² O:O′], [Cu(C7H9NO)2(SO4)]n [Zegh­ouan et al. (2016). Private communication (refcode 1481676). CCDC, Cambridge, England]. In the two complexes, the 2-(2-hy­droxy­eth­yl)pyridine ligands coordinate the metal ions through the N atom of the pyridine ring and the O atom of the hy­droxy group, creating a chelate ring. The Ni^II or Cu^II ion lies on an inversion centre and exhibits a slightly distorted MO4N2 octa­hedral coordination geometry, build up by O and N atoms from two 2-(2-hy­droxy­eth­yl)pyridine ligands and two water mol­ecules or two O atoms belonging to sulfate anions. The sulfate anion bridges the Cu^II ions, forming a polymeric chain. The photoluminescence properties of these complexes have been studied on as-synthesized samples and reveal that both compounds display a strong blue-light emission with maxima around 497 nm. From DFT/TDDFT studies, the blue emission appears to be derived from the ligand-to-metal charge-transfer (LMCT) excited state. In addition, the IR spectroscopic properties and thermogravimetric behaviours of both complexes have been investigated.