RESONANCE RAMAN STUDIES OF THE EXCITED ELECTRONIC STATES OF (CN)5FEIII(IMIDAZOLE)2- AND (NH3)5RUIII(IMIDAZOLE)3+
RESONANCE RAMAN STUDIES OF THE EXCITED ELECTRONIC STATES OF (CN)5FEIII(IMIDAZOLE)2- AND (NH3)5RUIII(IMIDAZOLE)3+
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DOI：
10.1021/ja00299a005
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发表时间：
1985-01-01
影响因子：
15
通讯作者：
SHEPHERD, RE
中科院分区：
文献类型：
--
作者：
JONES, CM;JOHNSON, CR;SHEPHERD, RE
利用紫外和可见波长共振拉曼光谱和拉曼激发光谱对咪唑（imH）与（CN）5 Fe ~（2+）和（NH_3）5 Ru ~（3+）配合物的电子跃迁进行了归属。对于第一次，共振拉曼激发分布区分π和π之间的能力。轨道参与咪唑金属电荷转移跃迁（LMCT）的证明。在475（Fe）和425 nm（Ru）的吸收光谱中观察到的LMCT跃迁涉及咪唑π 1轨道，其具有与环的碳原子相关的主要电子密度。403（Fe）和297 nm（Ru）LMCT跃迁涉及从π 2咪唑轨道的跃迁，π 2咪唑轨道具有与氮原子相关的高电子密度。（CN）5 Fe（imH）2-和（NH3）5 Ru（imH）3+配合物的咪唑环模式被这些LMCT跃迁选择性地增强。Fe络合物在356 nm处具有Ru络合物中不存在的额外吸收带。在该频带内的激发导致C.tbd.N伸缩和宽的低频Fe. sbd的排他性增强。因此，356-nm吸收带被指定为d π振动。(Fe). rarw. CN LMCT。在403和475 nm吸收带内C tbDN伸缩也增强，这表明Fe和HCN π的强混合。轨道从对氘代和甲基取代的频率敏感性出发，我们将（CN）5 Fe（imH）2-的265 cm ~（-1）振动初步归属为Fe.sbd.N（imH）伸缩振动。在血红素蛋白（如Hb）中激发类似的LMCT跃迁不太可能产生足够的拉曼强度，以允许研究近端组氨酸-血红素相互作用。
UV and visible wavelength resonance Raman spectra and Raman excitation profiles were used to assign the electronic transitions of the imidazole (imH) complexes of (CN)5Fe2+ and (NH3)5Ru3+. For the 1st time, the ability of resonance Raman excitation profiles to distinguish between the .pi. orbitals involved in imidazole-metal charge-transfer transitions (LMCT) is demonstrated. LMCT transitions observed in the absorption spectrum at 475 (Fe) and 425 nm (Ru) involve the imidazole .pi.1 orbital which has major electron density associated with the carbon atoms of the ring. The 403 (Fe) and 297 nm (Ru) LMCT transitions involve transitions from the .pi.2 imidazole orbital which has high electron density associated with the nitrogen atoms. The imidazole ring modes of the (CN)5Fe(imH)2- and (NH3)5Ru(imH)3+ complexes are selectively enhanced by these LMCT transitions. The Fe complex has an additional absorption band at 356 nm that is not present in the Ru complex. Excitation within this band results in the exclusive enhancement of the C.tbd.N stretch and a broad low-frequency Fe.sbd.(C.tbd.N) vibration; thus, the 356-nm absorption band is assigned to a d.pi.(Fe) .rarw. CN LMCT. The C.tbd.N stretch is also enhanced within the 403 and 475 nm absorption bands which indicate a strong mixing of the Fe and HCN .pi. orbitals. From the frequency sensitivity to imh deuteration and methyl substitution we tentatively assign the 265-cm-1 vibration of (CN)5Fe(imH)2- to a Fe.sbd.N (imH) stretching vibration. It is unlikely that excitation into similar LMCT transitions in heme proteins such as Hb will result in sufficient Raman intensity to permit studies of proximal histidine-heme interactions.