A Novel CuI Coordination Polymer Featuring a Trimethylenediamine Schiff Base Ligand: Structural, Spectroscopic, Theoretical, and Molecular Docking Studies

Abstract

In this work, we synthesized a new polymeric Cu(I) complex, [Cu(L-4Br)I](n), derived from a Salpn-type Schiff base ligand (L-4Br = N,N '-bis(4-bromobenzylidene)propane-1,3-diamine). In addition to NMR studies, the crystal structure was determined using single-crystal X-ray diffraction (SC-XRD), revealing that the Schiff base copper complex forms a binuclear one-dimensional (1D) polymer. In this structure, copper and iodide atoms form polymeric linkages, while both imine nitrogen atoms of the Schiff base coordinate with the copper centers. The Schiff base and iodide ligands coordinate to the copper centers, resulting in a slightly distorted trigonal planar geometry around each Cu atom. Hirshfeld surface analysis revealed that H center dot center dot center dot I interactions are the dominant contributors to the supramolecular architecture, while the CuI pairs exhibit the highest interaction tendency, corresponding to the formation of polymeric bonds. The unit cell contains 11.1 % void space, indicating a minimal volume that suggests favorable mechanical properties. The molecular structure was optimized using the B3LYP functional with the Def2-TZVP basis set, showing good agreement between the calculated and experimental ICu and CuN bond lengths. Molecular electrostatic potential (MEP) analysis revealed electron-rich regions around electronegative atoms, particularly iodine and nitrogen, as potential sites for interactions with electrophilic species. NBO analysis indicated significant electron donation from halides to adjacent copper centers, highlighting their strong donor capability within the coordination sphere. The copper atoms exhibit positive NPA charges (similar to 0.35), confirming their electron-accepting role as metal centers. The optimized geometry of the complex [Cu(L-4Br)I](n) was used as input for molecular docking studies performed with AutoDock Vina. Binding constants (K-b) for DNA and BSA were calculated using the equation Delta G degrees(b) = -RTlnK(b), where the calculated negative Delta G degrees(b) values confirm the spontaneity of the binding processes.