Compromise between conjugation length and charge-transfer in nonlinear optical η5-monocyclopentadienyliron(II) complexes with substituted oligo-thiophene nitrile ligands:: Synthesis, electrochemical studies and first hyperpolarizabilities
Compromise between conjugation length and charge-transfer in nonlinear optical η5-monocyclopentadienyliron(II) complexes with substituted oligo-thiophene nitrile ligands:: Synthesis, electrochemical studies and first hyperpolarizabilities
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DOI：
10.1016/j.jorganchem.2007.03.023
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发表时间：
2007-06-15
影响因子：
2.3
通讯作者：
Goovaerts, Etienne
中科院分区：
文献类型：
--
作者：
Garcia, M. Helena;Mendes, Paulo J.;Goovaerts, Etienne
合成并表征了一系列通式为[FeCp(P)(nc{SC4H2}(N)NO2)][PF6](P=dppe，(+)-Diop；n=1-3)的ETA(5)-单环戊二烯(II)与取代低聚硫吩腈的配合物。用循环伏安法研究了新化合物的电化学行为。为了揭示双光子共振效应和估算静态超极化率，用1.064和1.550微米两个基本波长的超瑞利散射测量了dppe配位络合物的二次超极化率。所获得的总体结果优于相关的ETA(5)-单环戊二烯(II)与对苯腈衍生物的配合物。尽管在1.064微米处的共振β随共轭配体中的噻吩基数目的增加而增加(最高可达910×10(-30)esu)，但静态值β(0)基本保持不变，如1.550微米的测量所示。结合电化学和光谱数据(IR、核磁共振、UV-Vis)，这种显著的β变化表明，共轭长度的增加与电荷转移效率的下降是平衡的。(C)2007年，爱思唯尔出版。
A systematic series of eta(5)-monocyclopentadienyliron(II) complexes with substituted oligo-thiophene nitrile ligands of general formula [FeCp(P_P)(NC{SC4H2}(n)NO2)] [PF6] (P_P = dppe, (+)-diop; n = 1-3) has been synthesized and characterized. The electrochemical behaviour of the new compounds was explored by cyclic voltammetry. Quadratic hyperpolarizabilities (beta) of the complexes with dppe coligands have been determined by hyper-Rayleigh scattering (HRS) measurements at two fundamental wavelengths of 1.064 and 1.550 mu m, to uncover the two-photon resonance effect and to estimate static beta values. The obtained overall results are found to be better than for the related eta(5)-monocyclopentadienyliron(II) complexes with p-benzonitrile derivatives. Although an increase of the resonant beta at 1.064 mu m with increasing number of thiophene units in the conjugated ligand was found (up to 910 x 10(-30) esu), the static values beta(0) remain practically unchanged, as shown by the 1.550 mu m measurements. Combined with the electrochemical and spectroscopic data (IR, NMR, UV-vis), this remarkable evolution of beta shows that the increase of conjugation length is balanced by a decrease in charge-transfer efficiency. (C) 2007 Published by Elsevier B.V.