MODELING BLUE COPPER PROTEIN RESONANCE RAMAN-SPECTRA WITH THIOLATE-CU(II) COMPLEXES OF A STERICALLY HINDERED TRIS(PYRAZOLYL)BORATE
MODELING BLUE COPPER PROTEIN RESONANCE RAMAN-SPECTRA WITH THIOLATE-CU(II) COMPLEXES OF A STERICALLY HINDERED TRIS(PYRAZOLYL)BORATE
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DOI：
10.1021/ja00085a044
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发表时间：
1994-03-23
影响因子：
15
通讯作者：
SPIRO, TG
中科院分区：
文献类型：
--
作者：
QIU, D;KILPATRICK, LT;SPIRO, TG
蓝铜蛋白的共振拉曼光谱异常复杂，在400-cm-1区域至少有5个谱带。为了探索这种复杂性的来源，我们研究了LCuSR络合物[L=hydrotris(3，5-diisopropyl-1-pyrazolyl)borate]，]的RR谱，它们是已知的与蓝色铜位的结构和电子相似的化合物。当连接在S原子上的C原子缺少质子时，在430 cm~(-1)附近出现一个明显的谱带，该谱带归属于铜蓝中心和模型络合物的短键(约2.1埃)的伸缩模式。频率按R=叔丁基>；三苯甲基>；五氟苯基的顺序递减，与增加电子撤除对铜-S键强度的预期效果一致。在较低的频率下观察到较弱的谱带，这归因于硫代内弯曲和铜-N[吡唑]伸展坐标。这些指认得到了叔丁基硫酸酯络合物的正规配位分析的证实，它准确地再现了叔丁基取代基的过重氢的频率和同位素位移。当R=仲丁基时，400-cm~(-1)区域有三个明显的谱带，而不是一个。简正波分析表明，在这三种模式下，Cu-S伸缩与C-C-S和C-C-C弯曲坐标的广泛混合是由于弯曲坐标的不等价性和HC-CH扭转的参与造成的。讨论了蓝铜蛋白RR谱的意义。
The resonance Raman (RR) spectra of blue copper proteins are unusually complicated, with at least five bands in the 400-cm-1 region. To explore the sources of this complexity we have examined RR spectra of LCuSR complexes [L = hydrotris(3,5-diisopropyl-1-pyrazolyl)borate], which are known to be close structural and electronic analogs of the blue Cu site. When the C atom which is attached to the S atom lacks a proton, a single prominent band is seen near 430 cm-1, assignable to the stretching mode of a short (ca. 2.1 angstrom) Cu-S bond, which is characteristic of the blue Cu site, and of the model complexes. The frequency decreases in the order R = tert-butyl > triphenylmethyl > pentafluorophenyl, consistent with the expected effect of increasing electron withdrawal on the Cu-S bond strength. Weaker bands are seen at lower frequencies, which are attributed to thiolate internal bending and to Cu-N[pyrazole] stretching coordinates. These assignments were confirmed with a normal coordinate analysis for the tert-butylthiolate complex, which accurately reproduced the frequencies and isotope shifts for perdeuteration of the tert-butyl substituent. When R = sec-butyl, three prominent bands are seen in the 400-cm-1 region instead of one. Normal mode analysis shows extensive mixing of Cu-S stretching with C-C-S and C-C-C bending coordinates in these three modes, occasioned by the inequivalences in the bending coordinates and the involvement of HC-CH torsion. Implications for the blue copper protein RR spectra are discussed.