title: Charge transfer and first hyperpolarizability: cage-like radicals C59X and lithium encapsulated Li@C59X (X=B, N).
abstract: Very recently, two new cage-like radicals (C59B and C59N) formed by a boron or nitrogen atom substituting one carbon atom of C60 were synthesized and characterized. In order to explore the structure-property relationships of combination the cage-like radical and alkali metal, the endohedral Li@C59B and Li@C59N are designed by lithium (Li) atom encapsulated into the cage-like radicals C59B and C59N. Further, the structures, natural bond orbital (NBO) charges, and nonlinear optical (NLO) responses of C59B, C59N, Li@C59B, and Li@C59N were investigated by quantum chemical method. Three density functional methods (BHandHLYP, CAM-B3LYP, and M05-2X) were employed to estimate their first hyperpolarizabilities (β tot) and obtained the same trend in the β tot value. The β tot values by BHandHLYP functional of the pure cage-like radicals C59B (1.30 × 10(3) au) and C59N (1.70 × 10(3) au) are close to each other. Interestingly, when one Li atom encapsulated into the electron-rich radical C59N, the β tot value of the Li@C59N increases to 2.46 × 10(3) au. However, when one Li atom encapsulated into the electron-deficient radical C59B, the β tot value of the Li@C59B sharply decreases to 1.54 × 10(2) au. The natural bond orbital analysis indicates that the encapsulated Li atom leads to an obvious charge transfer and valence electrons distribution plays a significant role in the β tot value. Further, frontier molecular orbital explains that the interesting charge transfer between the encapsulated Li atom and cage-like radicals (C59B and C59N) leads to differences in the β tot value. It is our expectation that this work will provide useful information for the design of high-performance NLO materials.
authors.affiliation: Institute of Functional Material Chemistry, Department of Chemistry, Northeast Normal University, Changchun, 130024, China.
authors.forename: Feng-Wei
authors.initials: FW
authors.lastname: Gao
authors.affiliation: Institute of Functional Material Chemistry, Department of Chemistry, Northeast Normal University, Changchun, 130024, China.
authors.forename: Rong-Lin
authors.initials: RL
authors.lastname: Zhong
authors.affiliation: Institute of Functional Material Chemistry, Department of Chemistry, Northeast Normal University, Changchun, 130024, China.
authors.forename: Shi-Ling
authors.initials: SL
authors.lastname: Sun
authors.affiliation: Institute of Functional Material Chemistry, Department of Chemistry, Northeast Normal University, Changchun, 130024, China. hlxu@nenu.edu.cn.
authors.forename: Hong-Liang
authors.initials: HL
authors.lastname: Xu
authors.affiliation: Institute of Functional Material Chemistry, Department of Chemistry, Northeast Normal University, Changchun, 130024, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Institute of Functional Material Chemistry, Department of Chemistry, Northeast Normal University, Changchun, 130024, China. zmsu@nenu.edu.cn.
authors.forename: Zhong-Min
authors.initials: ZM
authors.lastname: Su
keywords: Alkali metal; Cage-like radical; Charge transfer; First hyperpolarizability; NLO