Spectral Measurements of a Novel Charge Transfer Complex Formed by a Heterocyclic Aromatic Amine and 1,4-Dinitrobenzene: A Combined Experimental and DFT Approach
نویسندگان
1 Department of Chemistry, Ard.C., Islamic Azad University, Ardabil, Iran
2 Department of Chemistry, Ard.C., Islamic Azad University, Ardabil, Iran
3 Department of Chemistry, Ard.C., Islamic Azad University, Ardabil, Iran
4 Department of Chemistry, Ard.C., Islamic Azad University, Ardabil, Iran
doi
10.22036/pcr.2025.529463.2695چکیده
A new hydrogen-bonded charge transfer complex (HB-CTC) was synthesized using melamine (MA) as the electron donor and 1,4-dinitrobenzene (p-DNB) as the π-acceptor in a 1:1 ratio. Both experimental and computational techniques fully characterized this complex. The orange solid complex formed by refluxing in methanol displayed clear spectroscopic characteristics. The FTIR analysis confirmed the hydrogen bond (N–H∙∙∙O-), indicated by red-shifted NH₂ and NO₂ vibrations. NMR spectra showed distinct proton environments confirming the structure of the complex. UV-Vis studies revealed a new charge transfer absorption band at 266 nm. Density functional theory (DFT) calculations at the B3LYP/6-311G (d, p) level clarified the electronic structure, with the HOMO located on MA and the LUMO on p-DNB, revealing an energy gap of 3.113 eV. Thermodynamic data (ΔG°= -4.54 kcal/mol) and Mulliken/NBO analyses indicated that the formation is spontaneous and involves an efficient charge transfer (0.014 e from MA to p-DNB). This complex showed improved nonlinear optical properties, with its first- and second-order polarizabilities surpassing those of urea, pointing to potential optoelectronic applications. RDG and MEP analyses underscored the importance of stabilizing non-covalent interactions. This study offers a solid experimental and theoretical basis for developing CTCs with specific capabilities for materials science and organic electronics.
