Institut für Anorganische und Angewandte Chemie der Universität Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany.
Inorg Chem. 2009 Nov 16;48(22):10811-8. doi: 10.1021/ic901443x.
By comparing the absorption spectrum of pseudo trigonal planar Sm(eta(5)-C(5)Me(5))(3) (1) (KBr pellet, methylcyclohexane solution) with the previously assigned one of Sm(eta(5)-C(5)Me(4)H)(3) (2) a truncated experimental crystal field (CF) splitting pattern of the former compound could be derived in the NIR range. Because of its dark brown color, fluorescence is not observed from complex 1, and thus the CF splitting pattern in the low energy range could not be determined on the basis of luminescence measurements. However, comparing the FIR and MIR spectra (pellets) as well as the Raman spectra of oriented single crystals of 1 with those of La(eta(5)-C(5)Me(5))(3) (3) at least two additional CF levels could be detected. The free parameters of a phenomenological Hamiltonian were fitted to the thus extended CF splitting pattern of 1, leading to a reduced rms deviation of 15.0 cm(-1) for 21 assignments. On the basis of these phenomenological CF parameters, the global CF strength experienced by the Sm(3+) central ion was estimated, and seems to be the third largest one ever encountered in Sm(III) chemistry. The obtained Slater parameter F(2) and the spin-orbit coupling parameter zeta(4f) allow the insertion of compound 1 into empirical nephelauxetic and relativistic nephelauxetic series, respectively, of Sm(III) compounds. With its low F(2) value, complex 1 is the most covalent Sm(III) compound (considering only f electrons) found to date. The experimentally based non-relativistic molecular orbital scheme (in the f range) of complex 1 was set up and compared with the results of a previous Xalpha-SW calculation on the pseudo trigonal planar model compound Sm(eta(5)-C(5)H(5))(3). In the frame of the search for f-f and electronic Raman transitions, the vibrational spectra (FIR/MIR of pellets, Raman spectra of oriented single crystals) of compound 1 were recorded too, and partly assigned on the basis of the observed coincidences and polarizations.
通过比较假三角平面 Sm(eta(5)-C(5)Me(5))(3)（1）（KBr 压片、甲基环己烷溶液）的吸收光谱与之前分配的 Sm(eta(5)-C(5)Me(4)H)(3)（2）的光谱，可以在近红外范围内得出前者化合物的截断实验晶体场（CF）分裂模式。由于其深褐色，复合物 1 没有观察到荧光，因此不能基于荧光测量来确定低能范围的 CF 分裂模式。然而，通过比较 1 的远红外和中红外光谱（压片）以及各向同性单晶的拉曼光谱与 La(eta(5)-C(5)Me(5))(3)（3）的光谱，至少可以检测到另外两个 CF 能级。用经验哈密顿量拟合扩展的 CF 分裂模式，得到 21 个分配的均方根偏差为 15.0 cm(-1)。根据这些经验 CF 参数，估算了 Sm(3+)中心离子经历的全局 CF 强度，这似乎是在 Sm(III)化学中遇到的第三大强度。获得的 Slater 参数 F(2)和自旋轨道耦合参数 zeta(4f)允许将化合物 1 分别插入 Sm(III)化合物的经验螯合和相对论螯合系列中。由于其低 F(2)值，复合物 1 是迄今为止发现的最共价的 Sm(III)化合物（仅考虑 f 电子）。建立了基于实验的复合物 1 的非相对论分子轨道方案（在 f 范围内），并与以前的伪三角平面模型化合物 Sm(eta(5)-C(5)H(5))(3)的 Xalpha-SW 计算结果进行了比较。在寻找 f-f 和电子拉曼跃迁的过程中，还记录了化合物 1 的振动光谱（压片的远红外/中红外、各向同性单晶的拉曼光谱），并根据观察到的一致性和偏振进行了部分分配。
