FT-IR, NMR spectral analysis and theoretical NBO, FMOs, UV-Vis analysis of 7,7',8,8'-tetracyanoquinodimethane (TCNQ) in its ground and excited states by DFT and CIS methods

Abstract

The Gaussian 03W  program has been used for theoretical computations to compute optimal geometry, nuclear magnetic resonance (NMR), vibrational frequencies, natural atomic charges, natural bond orbital,( NBO), frontier molecular orbitals (FMOs), Ultraviolet-Visible (UV-Vis) analysis at DFT/B3LYP/6-31G(d) and ab initio CIS/6-31G(d) methods for 7,7',8,8'-tetracyanoquinodimethane (TCNQ) (C₁₂H₄N₄) in the ground as well as in the excited states. The ¹H, ¹³C and ¹⁵N NMR and further research is done on other molecular characteristics. The scaled vibrational frequencies and published works have been compared. The title molecule's infrared spectra are provided with a complete interpretation. In addition, stability of the molecule arising from hyperconjugative interactions. NBO analysis has been used to analyze charge delocalization. The findings demonstrate that charge in electron density (ED) in the  anti- bonding orbitals and E⁽²⁾ energies verifies that intra-molecular charge transfer (ICT)  is occurring within the molecule. The highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs)  energies that were computed demonstrate that charge transfer takes place inside the molecule.. Finally, the UV-Vis spectrum was measured in gas phase.