DFT Study on the electronic and nonlinear optical characteristics of clososupercarboranes C2Bn-2Hn (n= 13-20)

Boron, an electron-deficient element with more valence orbitals than valence electrons, forms a large family of stable, in some cases exceedingly stable, cluster structures via multicenter bonding [1-3]. Among the members of this family, carboranes are polyhedral boron hydride clusters each having one or more of its B(H) vertices replaced by C(H) units. Carboranes have attracted considerable interest over the last half-century. They show extraordinary thermal stability and unusual chemical reactivity. Thus, these cluster compounds are finding a broad range of applications encompassing organic synthesis, drug design, polymers, cancer therapy, catalysis, metal −organic frameworks, electronic devices[1]. In our study, all plausible positional isomers positional isomers for closo-supercarboranes C2Bn −2Hn (n = 13 −20) were located, by systematically substituting two boron atoms of the corresponding closo-borane dianions BnHn2 − (n = 13 −20) with two carbon atoms. The calculation results also show that the two carbon atoms prefer to be as far apart as possible results indicate that CAD (carbon-atomsadjacent) isomers are in general less favorable. The B3LYP method along with 6-31+g(d) basis set was employed to investigate the nonlinear optical response of the most stable CAP (Cap= carbon-atoms-apart) isomers of closo supercarboranes C2Bn-2Hn (n=13-20) by interaction with the lithium alkali metal .All calculations are performed using Gaussian 09 software.The results reveal that the interacted carboranes are energetically favorable. The electronic properties are strongly sensitive to the interaction with the lithium. It is found that the supercarboranes C2Bn- 2Hn interacted with the lithium. The HOMO-LUMO gap (HLG= εL-εH ) calculated in terms of the highest occupied molecular orbital (εH ) and the lowest unoccupied molecular orbital ( εL) energies, is applied to explore electronic properties of the considered systems. The static first hyperpolarizability values are assessed by CAM-B3LYP/6-311+G(d). According to results, the CAP isomers of closo supercarboranes C2Bn-2Hn interacted with the alkali metals could be introduced as a promising innovative nonlinear optical boron-based nanomaterial.