Effect of Solvent Polarity on the Vibrational Dephasing Dynamics of the Nitrosyl Stretch in an FeII Complex Revealed by 2D IR Spectroscopy
Effect of Solvent Polarity on the Vibrational Dephasing Dynamics of the Nitrosyl Stretch in an FeII Complex Revealed by 2D IR Spectroscopy
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DOI：
10.1021/jp4005345
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发表时间：
2013-07-25
影响因子：
2.9
通讯作者：
Khalil, Munira
中科院分区：
文献类型：
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作者：
Brookes, Jennifer F.;Slenkamp, Karla M.;Khalil, Munira
用二维红外光谱研究了硝普钠（SNP，Na-2[Fe（CN）（5）NO]中心点2 H（2）O）中亚硝酰伸缩振动（nu（NO））的振动退相动力学. SNP中的nu（NO）充当金属蛋白中发现的亚硝酰基配体的模型系统，所述金属蛋白在生物系统中的一氧化氮（NO）的运输和检测中起重要作用。我们进行了二维红外线的形状研究的努（NO）在以下溶剂：水，氧化氘，甲醇，乙醇，乙二醇，甲酰胺，和二甲亚砜。nu（NO）的振动溶致变色位移为52 cm（-1），范围从二甲基亚砜中的1884 cm（-1）到水中的1936 cm（-1）。在本研究中使用的溶剂中，nu（NO）的振动非谐性在21至28 cm（-1）之间变化。通过非线性响应理论拟合实验获得的二维红外光谱，获得了七种溶剂中SNP中nu（NO）的频率-频率相关函数（FFCFs）。拟合的二维红外线的形状显示，光谱扩散时间尺度的nu（NO）在SNP从0.8到4 ps变化，并与经验溶剂极性尺度呈负相关。我们比较我们的结果与实验确定的FFCF的其他带电的振动探针在极性溶剂和血红素蛋白的活性位点。我们的研究结果表明，振动退相动力学的nu（NO）在SNP反应的非均匀电场的波动所产生的极性溶剂周围的亚硝酰基和氰化物配体。发生在反式CN配体的溶质-溶剂相互作用是通过沿着Fe-NO键的π-背键网络在SNP中被感知的。
The vibrational dephasing dynamics of the nitrosyl stretching vibration (nu(NO)) in sodium nitroprusside (SNP, Na-2[Fe(CN)(5)NO]center dot 2H(2)O) are investigated using two-dimensional infrared (2D IR) spectroscopy. The nu(NO) in SNP acts as a model system for the nitrosyl ligand found in metalloproteins which play an important role in the transportation and detection of nitric oxide (NO) in biological systems. We perform a 2D IR line shape study of the nu(NO) in the following solvents: water, deuterium oxide, methanol, ethanol, ethylene glycol, formamide, and dimethyl sulfoxide. The frequency of the nu(NO) exhibits a large vibrational solvatochromic shift of 52 cm(-1), ranging from 1884 cm(-1) in dimethyl sulfoxide to 1936 cm(-1) in water. The vibrational anharmonicity of the nu(NO) varies from 21 to 28 cm(-1) in the solvents used in this study. The frequency-frequency correlation functions (FFCFs) of the nu(NO) in SNP in each of the seven solvents are obtained by fitting the experimentally obtained 2D IR spectra using nonlinear response theory. The fits to the 2D IR line shape reveal that the spectral diffusion time scale of the nu(NO) in SNP varies from 0.8 to 4 ps and is negatively correlated with the empirical solvent polarity scales. We compare our results with the experimentally determined FFCFs of other charged vibrational probes in polar solvents and in the active sites of heme proteins. Our results suggest that the vibrational dephasing dynamics of the nu(NO) in SNP reflect the fluctuations of the nonhomogeneous electric field created by the polar solvents around the nitrosyl and cyanide ligands. The solute solvent interactions occurring at the trans-CN ligand are sensed through the pi-back-bonding network along the Fe-NO bond in SNP.