Sato Hisako, Taniguchi Tohru, Nakahashi Atsufumi, Monde Kenji, Yamagishi Akihiko
Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
Inorg Chem. 2007 Aug 6;46(16):6755-66. doi: 10.1021/ic070300i. Epub 2007 Jul 11.
Vibrational circular dichroism (VCD) spectra of a series of [M(III)(acac)3] (acac = acetylacetonato; M = Cr, Co, Ru, Rh, Ir, and Al) and [M(III)(acac)2(dbm)] (dbm = dibenzoylmethanato; M = Cr, Co, and Ru) have been investigated experimentally and/or theoretically in order to see the effect of the central metal ion on the vibrational dynamics of ligands. The optical antipodes give the mirror-imaged spectra in the region of 1700-1000 cm(-1). The remarkable effect of the central metal ion is observed experimentally on the VCD peaks due to C-O stretches (1500-1300 cm(-1)) for both [M(III)(acac)3] and [M(III)(acac)2(dbm)]. In the case of Delta-[M(III)(acac)3], for example, the order of frequency of two C-O stretches (E and A2 symmetries) is dependent on the kind of a central metal ion as follows: E (-) > A2 (+) for M = Co, Rh, and Ir, while A2 (+) > E (-) for M = Cr and Ru. In the case of Delta-[M(III)(acac)2(dbm)], the order of frequency of three C-O stretches (A, B, and B symmetries) is as follows: A (-) > B (+) > B (+) for Co(III), B (+) > A (-) > B (-) for Cr(III), and A (-) > B (+) > B (-) for Ru(III). These results imply that the energy levels of C-O stretches are delicately affected by the kind of central metal ion. Since such detailed information is not obtained from the IR spectra alone, the VCD spectrum can probe the effect of the central metal ion on interligand cooperative vibration modes.
为了研究中心金属离子对配体振动动力学的影响，对一系列[M(III)(acac)3]（acac = 乙酰丙酮根；M = Cr、Co、Ru、Rh、Ir和Al）和[M(III)(acac)2(dbm)]（dbm = 二苯甲酰甲烷根；M = Cr、Co和Ru）进行了振动圆二色性（VCD）光谱的实验和/或理论研究。光学对映体在1700 - 1000 cm(-1)区域给出镜像光谱。实验观察到，对于[M(III)(acac)3]和[M(III)(acac)2(dbm)]，中心金属离子对归因于C - O伸缩振动（1500 - 1300 cm(-1)）的VCD峰有显著影响。例如，在Δ-[M(III)(acac)3]的情况下，两个C - O伸缩振动（E和A2对称性）的频率顺序取决于中心金属离子的种类，如下所示：对于M = Co、Rh和Ir，E (-) > A2 (+)；而对于M = Cr和Ru，A2 (+) > E (-)。在Δ-[M(III)(acac)2(dbm)]的情况下，三个C - O伸缩振动（A、B和B对称性）的频率顺序如下：对于Co(III)，A (-) > B (+) > B (+)；对于Cr(III)，B (+) > A (-) > B (-)；对于Ru(III)，A (-) > B (+) > B (-)。这些结果表明，C - O伸缩振动的能级受到中心金属离子种类的微妙影响。由于仅从红外光谱无法获得此类详细信息，VCD光谱可以探测中心金属离子对配体间协同振动模式的影响。
