Rozenberg M, Shoham G, Reva I, Fausto R
Department of Inorganic and Analytical Chemistry, The Hebrew University of Jerusalem, Jerusalem, Givat Ram 91904, Israel.
Spectrochim Acta A Mol Biomol Spectrosc. 2004 Jan;60(1-2):463-70. doi: 10.1016/s1386-1425(03)00251-8.
The FTIR spectra of both the pure NH and isotopically substituted ND (<10% and >90% D) polycrystalline cytosine were recorded in the range 400-4000 cm(-1) as a function of temperature (10-300 K). For the first time, uncoupled NH(D) stretching mode bands of amine and imine groups were observed in the spectra of isotopically diluted cytosine at low temperatures. These bands correspond to the three distinct H-bonds that are present in the crystal, in agreement with the available data obtained by structural methods. At least nine bands were observed below 1000 cm(-1) and, in consonance with their temperature and isotopic exchange behavior, were assigned to the NH proton out-of-the-plane bending modes. Six of these bands were found to correspond to additional "disordered" H-bonds, which could not be observed by structural methods. Empirical correlations of spectral and thermodynamic parameters enabled to estimate the contribution of the H-bonds to the sublimation enthalpy of the crystal, in agreement with independent experimental data.
在400 - 4000 cm⁻¹范围内，记录了纯NH和同位素取代的ND（<10%和>90% D）多晶胞嘧啶的傅里叶变换红外光谱（FTIR），其作为温度（10 - 300 K）的函数。首次在低温下同位素稀释的胞嘧啶光谱中观察到胺基和亚胺基未耦合的NH（D）伸缩模式带。这些谱带对应于晶体中存在的三种不同的氢键，这与通过结构方法获得的现有数据一致。在1000 cm⁻¹以下观察到至少九条谱带，根据它们的温度和同位素交换行为，将其归属于NH质子面外弯曲模式。发现其中六条谱带对应于额外的“无序”氢键，这是结构方法无法观察到的。光谱和热力学参数的经验相关性能够估计氢键对晶体升华焓的贡献，这与独立的实验数据一致。
