Despite the effort deployed, the decryption of the vibrational spectra of amino acids in the high wavenumber region (2600–3600 cm⁻¹) remains a challenge for both spectroscopists and computational scientists. In this challenging context, the structures and vibrational spectra of five amino acid crystals (l-tyrosine, l-histidine, l-serine, l-serine monohydrate and DL-serine) have been investigated. Based on the results of DFT calculations performed in the solid state, the calculated vibrational spectra have been analyzed in order to clarify some controversies concerning previously published band assignments for the OH and NH stretching modes. Except for l-serine, which reveals three calculated IR bands at 3456, 3506 and 3507 cm⁻¹ ascribed to different OH stretching vibrations in the unit-cell, all the calculated fundamental bands for the other four compounds, including those due to the l-serine molecule as it exists in l-serine monohydrate crystal, are predicted to be below 3201 cm⁻¹. Because the structural and vibrational properties of the investigated molecules are strongly correlated to their own H-bonding networks, the previous theoretical studies based on non-periodic approaches have failed to give a correct description of the vibrational behaviors in the NH and OH stretching regions. In addition, a careful comparison of some previously published IR and Raman spectra of the studied anhydrous amino acids confirms the presence of certain additional bands. The possible origin of these bands is revealed in this study.

尽管付出了努力，但对高波数区（2600-3600 cm ^-1）中氨基酸的振动光谱的解密仍然是光谱学家和计算科学家面临的挑战。在这个具有挑战性的背景下，已经研究了五种氨基酸晶体（l-酪氨酸、l-组氨酸、l-丝氨酸、l-丝氨酸一水合物和 DL-丝氨酸）的结构和振动光谱。基于在固态下执行的 DFT 计算的结果，已对计算出的振动光谱进行了分析，以澄清有关先前公布的 O H 和 N H 拉伸模式的频带分配的一些争议。除了l-丝氨酸，在 3456、3506 和 3507 cm ^-1处显示三个计算的 IR 谱带，归因于晶胞中不同的 OH 伸缩振动，其他四种化合物的所有计算基本谱带，包括由l-丝氨酸分子引起的谱带由于它存在于l-丝氨酸一水合物晶体中，预计低于 3201 cm ^-1。由于所研究分子的结构和振动特性与其自身的氢键网络密切相关，以前基于非周期性方法的理论研究未能正确描述 N H 和 O中的振动行为H 拉伸区域。此外，对所研究的无水氨基酸的一些先前发表的 IR 和拉曼光谱的仔细比较证实了某些附加带的存在。本研究揭示了这些带的可能起源。