Baran J, Pawlukojć A, Majerz I, Malarski Z, Sobczyk L, Grech E
Institute of Low Temperature and Structural Research, Wrocław, Poland.
Spectrochim Acta A Mol Biomol Spectrosc. 2000 Aug;56A(9):1801-12. doi: 10.1016/s1386-1425(00)00239-0.
The infra-red (IR), Raman (R) and inelastic incoherent neutron scattering (IINS) spectra, particularly in low frequency region, of the title ionic adduct were studied. It is shown that all low frequency vibrations (below 200 cm(-1)) of (CH3)2N groups of protonated 1,8-bis(dimethylamino)naphthalene (DMAN)--clearly observed in IINS spectra--are sensitive to the environment, i.e. to the type of counterion forming short contacts with C-H bonds of methyl groups. The internal frequencies were also calculated by ab initio method. The results are consistent with numerous observations of the counteranion effect on the geometry of the protonated DMAN. The conclusions are compared with structural and NMR studies reported recently for the 1,8-bis(dimethylamino)naphthalene with dichloromaleic acid (DMAN x DCM) adduct. The single crystal R polarized spectra taken over the frequency range 20-3200 cm(-1) were analyzed in detail. We have shown that a substantial difference in the IR spectrum of the dichloromaleic acid (DCM) anion in the DMAN adduct and in the potassium salt results from different geometries of OHO hydrogen bonds. In the case of potassium salt the chains of longer intermolecular hydrogen bonds are formed described by means of a double minimum potential.
研究了标题离子加合物的红外（IR）、拉曼（R）和非弹性非相干中子散射（IINS）光谱，特别是低频区域的光谱。结果表明，质子化的1,8-双（二甲基氨基）萘（DMAN）的（CH3）2N基团的所有低频振动（低于200 cm(-1)）——在IINS光谱中清晰可见——对环境敏感，即对与甲基的C-H键形成短接触的抗衡离子类型敏感。还通过从头算方法计算了内部频率。结果与关于抗衡阴离子对质子化DMAN几何结构影响的大量观察结果一致。将这些结论与最近报道的1,8-双（二甲基氨基）萘与二氯马来酸（DMAN x DCM）加合物的结构和核磁共振研究进行了比较。详细分析了在20 - 3200 cm(-1)频率范围内采集的单晶R偏振光谱。我们已经表明，DMAN加合物和钾盐中二氯马来酸（DCM）阴离子的红外光谱存在显著差异，这是由于OHO氢键的不同几何结构所致。在钾盐的情况下，形成了由双势阱描述的较长分子间氢键链。
