Electronic structures and second-order nonlinear optical properties of a series of functionalized Sc3N@Ih–C80 derivatives

Abstract

Combination of porphyrin, tetrathiafulvalene (TTF), and trimetallic nitride template endohedral metallofullerenes (TNT-EMFs) chemistry is highly desired because this hybrid entity will possess the rich scientific heritage of porphyrin, TTF, and TNT-EMF. In the present paper, the electronic structure and second-order nonlinear optical (NLO) properties of a series of TNT-EMF derivatives have been calculated by density functional theory (DFT) and finite field (FF) method. Our DFT calculations well reproduce the geometrical structure of the known [5, 6]- and [6, 6]-benzyne monoadducts. Our DFT calculations show that the [5, 6]-benzyne monoadduct is the thermodynamic product because the calculated total energy including the electronic and zero-point corrected energies of [5, 6]-benzyne monoadduct is ∼4.9kcalmol−1 more stable than the [6, 6]-benzyne monoadduct. Two new molecular systems, porphyrin derivative (porphyrin+TNT-EMF) and TTF derivative (TTF+porphyrin+TNT-EMF) have been considered in this work. The optimized calculations show that introduction of porphyrin and TTF cannot significantly affects the geometry of the weak four-membered ring and Sc3N@Ih–C80. The electronic structure analysis shows that the TTF derivative possesses the smallest HOMO–LUMO gap (∼1.5eV) among all studied compounds in this work, and the one-electron-oxidized center will be the TTF unit. DFT–FF calculations show that the [6, 6]-benzyne monoadduct has a large static first hyperpolarizability relevant to the [5, 6]-benzyne monoadduct. Thus, the second-order optical nonlinearity may be an effective technique to determine the location of the functional groups on the cage surfaces of the TNT-EMF. A substantial enhancement in static first hyperpolarizability has been obtained in porphyrin and TTF derivatives according to our DFT–FF calculation. The calculated β values of porphyrin and TTF derivatives are ∼15 and ∼30 times as large as that of [5, 6]-monoadduct. The time-dependent (TD) DFT calculations confirm that the increasing trend of the static first hyperpolarizability. And the molecular orbital transition feature shows that the TTF unit does not display the electron donor character because of the non-planar arched structure.