The structural and spectroscopic properties of a new triazolopyridine derivative (1,2,4-triazolo[4,3-a]pyridin-3-amine) are described in this paper. Its FTIR spectrum was recorded in the 100–4000 cm−1 range and its FT-Raman spectrum in the range 80–4000 cm−1. The molecular structure and vibrational spectra were analyzed using the B3LYP/6-311G(2d,2p) approach and the GAUSSIAN 16W program. The assignment of the observed bands to the respective normal modes was proposed on the basis of PED calculations. XRD studies revealed that the studied compound crystallizes in the centrosymmetric monoclinic space group P21/n with eight molecules per unit cell. However, the asymmetric unit contains two 1,2,4-triazolo[4,3-a]pyridin-3-amine molecules linked via N–H⋯N hydrogen bonds with a R22(8) graph. The stability of the studied molecule was considered using NBO analysis. Electron absorption and the luminescence spectra were measured and discussed in terms of the calculated singlet, triplet, HOMO and LUMO electron energies. The Stokes shifts derived from the optical spectra were equal to 9410 cm−1 for the triazole ring and 7625 cm−1 for the pyridine ring.

中文翻译：

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1,2,4-三唑并[4,3-a]吡啶-3-胺的结构和光学性质

本文描述了一种新的三唑并吡啶衍生物（1,2,4-三唑并[4,3-a]吡啶-3-胺）的结构和光谱特性。其 FTIR 光谱记录在 100-4000 cm-1 范围内，其 FT-拉曼光谱记录在 80-4000 cm-1 范围内。使用 B3LYP/6-311G(2d,2p) 方法和 GAUSSIAN 16W 程序分析分子结构和振动光谱。在 PED 计算的基础上提出了将观察到的波段分配给各自的正常模式。XRD 研究表明，所研究的化合物在中心对称单斜晶系空间群 P21/n 中结晶，每个晶胞有 8 个分子。然而，不对称单元包含两个 1,2,4-三唑并[4,3-a]吡啶-3-胺分子，通过 N-H⋯N 氢键与 R22(8) 图连接。使用 NBO 分析考虑所研究分子的稳定性。根据计算的单重态、三重态、HOMO 和 LUMO 电子能量测量和讨论电子吸收和发光光谱。三唑环的斯托克斯位移等于 9410 cm-1，吡啶环的斯托克斯位移等于 7625 cm-1。