Open-Shell Character and Second Hyperpolarizabilities of One-Dimensional Chromium(II) Chains: Size Dependence and Bond-Length Alternation Effect

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• 作者：Hitoshi Fukui ; Shota Takamuku ; Taishi Yamada ; Kotaro Fukuda ; Taku Takebayashi ; Yasuteru Shigeta ; Ryohei Kishi ; Beno卯t Champagne ; Masayoshi Nakano
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：August 18, 2014
• 年：2014
• 卷：53
• 期：16
• 页码：8700-8707
• 全文大小：445K
• ISSN：1520-510X

文摘

Using the long-range corrected spin-unrestricted density functional theory (LC-UBLYP) method, we have investigated the longitudinal third-order nonlinear optical (NLO) properties, i.e., the second hyperpolarizabilities 纬 of open-shell singlet one-dimensional (1D) extended metal atom chain (EMAC) systems, chromium(II) chains Cr^II_2n (n = 1鈥?), with different metal鈥搈etal bond lengths from the viewpoint of the open-shell character dependences of each d orbital contribution (d蟽, d蟺, d未) to 纬 and of the chain-length dependence of 纬. It turns out that the chain length dependences of the open-shell characters of d蟺 and d未 orbitals at any metal鈥搈etal bond length are negligible, while the d蟽 open-shell character decreases as a function of chain length. The systems display bell-shaped behaviors of 纬 as a function of the metal鈥搈etal bond length, in which the 纬 values attain maxima for intermediate d蟽 open-shell character. The maximum 纬 value (纬_max) exhibits remarkable enhancement as a function of chain length. It is also found that the bond length alternation (BLA) significantly affects the 纬 values and their chain-length dependences. The present results provide the guiding principles for designing transition-metal complexes with open-shell singlet 1D metallic chains exhibiting large third-order optical nonlinearity.