School of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
J Am Chem Soc. 2010 Feb 10;132(5):1706-23. doi: 10.1021/ja908667p.
In this article, we describe a series of complexes with electron-rich cis-{Ru(II)(NH(3))(4)}(2+) centers coordinated to two pyridyl ligands bearing N-methyl/arylpyridinium electron-acceptor groups. These V-shaped dipolar species are new, extended members of a class of chromophores first reported by us (Coe, B. J. et al. J. Am. Chem. Soc. 2005, 127, 4845-4859). They have been isolated as their PF(6)(-) salts and characterized by using various techniques including (1)H NMR and electronic absorption spectroscopies and cyclic voltammetry. Reversible Ru(III/II) waves show that the new complexes are potentially redox-switchable chromophores. Single crystal X-ray structures have been obtained for four complex salts; three of these crystallize noncentrosymmetrically, but with the individual molecular dipoles aligned largely antiparallel. Very large molecular first hyperpolarizabilities beta have been determined by using hyper-Rayleigh scattering (HRS) with an 800 nm laser and also via Stark (electroabsorption) spectroscopic studies on the intense, visible d --> pi* metal-to-ligand charge-transfer (MLCT) and pi --> pi* intraligand charge-transfer (ILCT) bands. The latter measurements afford total nonresonant beta(0) responses as high as ca. 600 x 10(-30) esu. These pseudo-C(2v) chromophores show two substantial components of the beta tensor, beta(zzz) and beta(zyy), although the relative significance of these varies with the physical method applied. According to HRS, beta(zzz) dominates in all cases, whereas the Stark analyses indicate that beta(zyy) is dominant in the shorter chromophores, but beta(zzz) and beta(zyy) are similar for the extended species. In contrast, finite field calculations predict that beta(zyy) is always the major component. Time-dependent density functional theory calculations predict increasing ILCT character for the nominally MLCT transitions and accompanying blue-shifts of the visible absorptions, as the ligand pi-systems are extended. Such unusual behavior has also been observed with related 1D complexes (Coe, B. J. et al. J. Am. Chem. Soc. 2004, 126, 3880-3891).
在本文中，我们描述了一系列具有富电子顺式-{Ru(II)(NH(3))(4)}(2+)中心的配合物，这些中心与两个吡啶配体配位，配体上带有 N-甲基/芳基吡啶鎓电子受体基团。这些 V 形偶极体是我们首次报道的一类发色团的新的扩展成员（Coe，B. J.等。J. Am. Chem. Soc. 2005，127，4845-4859）。它们已被分离为其 PF(6)(-)盐，并通过使用各种技术进行了表征，包括（1）H NMR 和电子吸收光谱以及循环伏安法。可逆的 Ru(III/II)波表明，新的配合物是潜在的氧化还原开关发色团。四个配合物盐的单晶 X 射线结构已经获得；其中三个非对称结晶，但单个分子偶极子主要反向排列。通过使用 800nm 激光的超瑞利散射（HRS）和对强烈的可见 d --> pi金属到配体电荷转移（MLCT）和 pi --> pi 内配体电荷转移（ILCT）带的斯塔克（电吸收）光谱研究，确定了非常大的分子第一超极化率 beta。后一种测量方法提供了高达约 600 x 10(-30) esu 的总非共振 beta(0)响应。这些伪 C(2v)发色团显示出 beta 张量的两个重要分量，beta(zzz)和 beta(zyy)，尽管这些分量的相对重要性随所应用的物理方法而变化。根据 HRS，在所有情况下 beta(zzz)都占主导地位，而 Stark 分析表明，在较短的发色团中 beta(zyy)占主导地位，但对于扩展物种，beta(zzz)和 beta(zyy)相似。相比之下，有限场计算预测 beta(zyy)总是主要成分。时变密度泛函理论计算预测，随着配体 pi 体系的扩展，对于名义上的 MLCT 跃迁，ILCT 特征增加，并且可见吸收发生蓝移。与相关的 1D 配合物（Coe，B. J.等。J. Am. Chem. Soc. 2004，126，3880-3891）一样，也观察到了这种异常行为。
