Structural Studies, NBO Analysis and Reactivity Descriptors of π-Extended Tetrathiafulvalene (exTTF) Connected to Thiophene Derivative

We report here a quantum chemical study of π-extended tetrathiafulvalene (exTTF) connected to thiophene derivative 1-4 performed at DFT/B3LYP with 6-31G (d,p) basis set using Gaussian 09w program package. The optimized parameters (bond lengths, bond angles and dihedral angles) are determined in this investigation. The most reactive sites for electrophilic and nucleophilic attack are also predicted from the MEP analysis and the results show clearly that the regions reveal the negative electrostatic potential are localized in the nitro functional group while the regions presenting the positive potential are localized in the hydrogen atoms of alkyl and cycled groups. The possible electronic transitions are determined by HOMO–LUMO orbital shapes and their energies, although HOMO-1, HOMO are confined on the π-conjugated spacer of TTF core and delocalized over the part of thiophene derivative, and LUMO, LUMO+1 are confined the part of thiophene derivative and delocalized on the π-conjugated spacer of TTF core which explained the charge transfer process in the molecular system. Global reactivity parameters of the studied molecules are also calculated it indicate that compound 2 is the more reactive. The natural bond orbital analysis indicates that the nonlinear optical activity of the molecules arises due to the π→π* transitions. The predicted NLO properties of the title compounds are much greater than the ones of urea, which means that are an attractive object for future studies of nonlinear optics.