Investigation of electrical conductance properties, non-covalent interactions and TDDFT calculation of a newly synthesized copper(II) metal complex

Abstract

[Cu(pydc)(apy)]·3H2O (1) (pydcH2 = pyridine-2,6-dicarboxylic acid; apy = 2- aminopyridine) has been synthesized and characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction techniques. Crystallographic analysis tells that the complex 1 has distorted square pyramid geometry with pydcH2 coordinated as a tridentate ligand to each metal ion through two oxygen atoms of each carboxylate group and the nitrogen atom of the pyridine moiety. Three non-coordinated water molecules are present in the asymmetric unit and all are involved in constructing a (H2O)6 cluster with chair conformation like cyclohexane. Interestingly, The average O⋯O distance of 2.759 Å in water hexamer of Complex 1 is closer to the respective distance of ice (2.76 Å for ice Ih at 90 K) than to that of bulk liquid water (2.85 Å). Also, the average O–O–O bond angle of 107.96° is close to the tetrahedral angle in ice Ih form. Apart from water cluster, the aromatic molecules are engaged in several non-covalent interactions like NH … π, lone pair … π, π … π and hydrogen bonds. These types of non-covalent interactions attribute to the supramolecular framework of the studied molecule. The electrical conductivity in terms of current was measured at room temperature before and after annealed of the synthesized complex compound on thin film specimen of order 230 and 240 μA respectively with bias voltage 1 V. In addition, the electronic transitions of 1 were recorded and the electronic distribution of HOMO-LUMO was rationalized theoretically (through time-dependent density functional theory (TDDFT)).