A theoretical study on the stability difference of the borane BnHn2- and carborane C2Bn-2Hn (5 ≤ n ≤ 7) clusters

Abstract

In order to study the electronic structure and structural stability of borane BnHn2- and carborane C3Bn-2Hn (5≤n≤7) clusters, especially the stability difference between the borane B5H52- and carborane C3B3H5. The frontier orbital energy levels of the borane BnHn2- and carborane C3Bn-2Hn (5≤n≤7) clusters are calculated at CCSD(T)/aug-cc-pVXZ//B3LYP/def2-TZVPP level. The results are further analyzed by qualitative frontier orbital method based on the cap-ring interaction. The results reveal that: (1) the larger Egap(HOMO-LUMO energy gap) of carborane C3Bn-2Hn (5≤n≤7) clusters than borane BnHn2- (5≤n≤7) clusters originates from the more effective cap-ring orbital overlap of carborane C3Bn-2Hn (5≤n≤7) clusters than that of borane BnHn2- (5≤n≤7) clusters; (2) the smallest Egap of the borane B5H52- results from the highest energy level of the ring symmetry-adapted linear combination orbital of B5H52- cluster; and (3) the largest Egap of the carborane C3B3H5 is induced by the most effective cap-ring orbital interaction of C3B3H5 cluster.