METALLOPORPHYRIN GAS AND CONDENSED-PHASE RESONANCE RAMAN STUDIES - THE ROLE OF VIBRATIONAL ANHARMONICITIES AS DETERMINANTS OF RAMAN FREQUENCIES
METALLOPORPHYRIN GAS AND CONDENSED-PHASE RESONANCE RAMAN STUDIES - THE ROLE OF VIBRATIONAL ANHARMONICITIES AS DETERMINANTS OF RAMAN FREQUENCIES
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DOI：
10.1021/ja00363a006
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发表时间：
1983-01-01
影响因子：
15
通讯作者：
MURTAUGH, J
中科院分区：
文献类型：
--
作者：
ASHER, SA;MURTAUGH, J
报道了气相卟啉的第一共振拉曼光谱。对Ni(II)和Co(II)八乙基卟啉在气相和缩合溶液中的拉曼光谱进行了广泛的温度依赖研究，表明拉曼频率与温度有很大的关系。在气相和凝聚相样品之间观察到的微小频率差异表明，在烃类溶剂中发生的范德华相互作用不影响血红素的频率。拉曼频率与温度的关系显示出一个表观激活能。这种温度依赖性被解释为由高频振动和热填充低频振动之间的非简谐相互作用引起的。在40~600K温度范围内，观察到与血红素核大小相关的拉曼振动，频移高达15 cm-1。这些变化可以被解释为血红素环的扩展，因为低频振动是热填充的。血红素振动频率的大的温度依赖性可能解释了在光化学产生的瞬时拉曼研究中观察到的一些光谱漂移。在连接的血红素络合物的光解过程中，例如一氧化碳氧合血红蛋白和碳氧合肌红蛋白，预计会发生大于100K的瞬时血红素温度升高。这种温度升高将导致血红素拉曼振动向更低频率移动。
The first resonance Raman spectra of gas-phase porphyrins are reported. An extensive temperature-dependent study of the Raman spectra of Ni(II) and Co(II) octaethylporphine both in the gas phase and in condensed solution phases demonstrates a large temperature dependence of the Raman frequencies. The small frequency differences observed between the gas- and condensed-phase samples indicate that the van der Waals interactions occurring in hydrocarbon solvents do not affect the heme frequencies. The temperature dependence of the Raman frequencies shows an apparent activation energy. This temperature dependence is interpreted as arising from anharmonic interactions between high-frequency vibrations and thermally populated low-frequency vibrations. Frequency shifts as large as 15 cm-1 are observed between 40 and 600 K for the heme core size dependent Raman vibrations. These shifts may be interpreted as an expansion of the heme ring as low-frequency vibrations are thermally populated. The large temperature dependence of the heme vibrational frequencies may account for some of the spectral shifts observed in photochemically generated transient Raman studies in heme proteins. Transient heme temperature increases of greater than 100 K are expected to occur during photolysis of liganded heme complexes such as carbon monoxyhemoglobin and carbon monoxymyoglobin. This temperature increase will result in shifts to lower frequency for the heme Raman vibrations.