Theoretical and electrochemical analysis of halogenated salmphen-type dinuclear copper(II) complex: The influence of halogenated ligands on bandgap

Abstract

The predictable control of energy levels in coordination polymer is an essential issue in molecular science. To explore a simple and feasible strategy for tuning the energy levels of Schiff base materials, the present work synthesized a novel halogen-substituted cofacial Schiff base compound, CuII2(2-Cl-Salmphen)2 (Cu-2-Cl-Salmphen), and the non-halogenated analogue CuII2(H-Salmphen)2 (Cu-H-Salmphen) was introduced for comparison. Experimental results show that the introduction of halogen atoms can effectively increase the absorbance and decrease the impedance of the compound. Further theoretical analyses revealed that the substitutional halogen atoms can not only enlarge the conjugation area but also change the electron density and the molecular orbital energy levels, thus enabling modulation of the bandgap values of the compounds. Besides, NCI studies have demonstrated that the substitution of halogens can form additional intermolecular interaction pathways, adjusting the interactions between adjacent molecules.