Two halogenated coplanar Schiff base complexes: Insights into the impact of halogen substitution on intermolecular interactions via theoretical calculations

The manipulation of intermolecular interaction intensities significantly influences a wide range of domains in material science, attracting widespread attention from researchers. In this study, we used a strategy distinct from the adjustment of molecular skeletons, through the introduction of different halogenated ligands, two new coplanar halogenated Schiff base complexes with large conjugate structure [Cu II (3,5-Cl-Salphmen)]·DMF( CuL 3,5-Cl ) and [Cu II (3Br-5Cl-Salphmen)]·DMF( CuL 3Br5Cl ), where 3,5-Cl-Salphmen( H 2 L 3,5-Cl ) = N,N′ -bis(3,5-dichlorosalicylidene)- diamine, 3Br-5Cl-Salphmen( H 2 L 3,5-Br ) = N,N′ -bis(3‑bromo-5-chlorosalicylidene)- diamine were obtained. The effects of different substituted atoms on molecular orbitals, energy levels, intermolecular interstrength are analyzed in detail by DFT theory calculations, and compared with Cu II -3,5-Br-Salphmen( CuL 3,5-Br ) and non-halogenated analogues Cu II -Salphmen( CuL H ). Analysis results show that the strategy of increasing molecular conjugation by the substitution of different halogen atoms can not only effectively modulate the charge distribution on the benzene ring but also can precisely control the binding energy as well as strength of intermolecular interactions .