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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >The hydrogen-bonded 2-pyridone dimer model system. 1. combined NMR and FT-IR spectroscopy study
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The hydrogen-bonded 2-pyridone dimer model system. 1. combined NMR and FT-IR spectroscopy study

机译：氢键2-吡啶酮二聚体模型系统。 1.结合核磁共振和傅立叶变换红外光谱研究

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摘要

2-Pyridone (PD), converting to 2-hydroxypyridine (HP) through a lactam-lactim isomerization mechanism, can form three different cyclic dimers by hydrogen bond formation: (PD)_2, (PD-HP), and (HP)_2. We investigate the complexation chemistry of pyridone in dichloromethane-d _2 using a combined NMR and Fourier transform infrared (FT-IR) approach. Temperature-dependent ~1H NMR spectra indicate that at low temperatures (<200 K) pyridone in solution predominantly exists as a cyclic (PD)_2 dimer, in exchange with PD monomers. At higher temperatures a proton exchange mechanism sets in, leading to a collapse of the doublet of ~(15)N labeled 2-pyridone. Linear FT-IR spectra indicate the existence of several pyridone species, where, however, a straightforward interpretation is hampered by extensive spectral overlap of many vibrational transitions in both the fingerprint and the NH/OH stretching regions. Two-dimensional IR correlation spectroscopy applied on concentration-dependent and temperature-dependent data sets reveals the existence of the (PD)_2 cyclic dimer, of PD-CD _2Cl_2 solute-solvent complexes, and of PD-PD chainlike dimers. Regarding the difference in effective time scales of the NMR and FT-IR experiments, milliseconds vs (sub)picoseconds, the cyclic dimers (PD-HP) and (HP)_2, and the chainlike conformations HP-PD, may function as intermediates in reaction pathways through which the protons exchange between PD units in cyclic (PD)_2.
机译：通过内酰胺-内酰胺异构化机制转化为2-羟基吡啶（HP）的2-吡啶酮（PD）可通过氢键形成形成三种不同的环状二聚体：（PD）_2，（PD-HP）和（HP）_2 。我们使用结合的NMR和傅立叶变换红外（FT-IR）方法研究了吡啶酮在二氯甲烷-d _2中的络合化学。温度相关的〜1H NMR光谱表明，在低温（<200 K）下，吡啶酮主要以环状（PD）_2二聚体形式存在，与PD单体交换。在更高的温度下，质子交换机制开始起作用，导致〜（15）N标记为2-吡啶酮的双峰折叠。线性FT-IR光谱表明存在几种吡啶酮类化合物，但是，指纹和NH / OH拉伸区域中许多振动跃迁的广泛光谱重叠阻碍了简单的解释。应用于浓度相关和温度相关数据集的二维红外相关光谱揭示了（PD）_2环状二聚体，PD-CD _2Cl_2溶质-溶剂络合物和PD-PD链状二聚体的存在。关于NMR和FT-IR实验的有效时间尺度的差异，毫秒与（亚）皮秒，环状二聚体（PD-HP）和（HP）_2以及链状构象HP-PD可能是环（PD）_2中PD单元之间质子交换所通过的反应途径。

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