Crystal Structure, Matrix-Isolation FTIR, and UV-Induced Conformational Isomerization of 3-Quinolinecarboxaldehyde

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• 作者：Nihal Ku艧 ; Marta Sofia Henriques ; Jos茅 Ant贸nio Paix茫o ; Leszek Lapinski ; Rui Fausto
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：September 25, 2014
• 年：2014
• 卷：118
• 期：38
• 页码：8708-8716
• 全文大小：454K
• ISSN：1520-5215

文摘

The crystal structure of 3-quinolinecarboxaldehyde (3QC) has been solved, and the compound has been shown to crystallize in the space group P2₁/c (monoclinic) with a = 6.306(4), b = 18.551(11), c = 6.999(4) 脜, 尾 = 106.111(13)掳, and Z = 4. The crystals were found to exhibit pseudomerohedral twinning with a twin law corresponding to a two-fold rotation around the monoclinic (100) reciprocal lattice axis (or [4 0 1] in direct space). Individual molecules adopt the syn conformation in the crystal, with the oxygen atom of the aldehyde substituent directed toward the same side of the ring nitrogen atom. In the gas phase, the compound exists in two nearly isoenergetic conformers (syn and anti), which could be successfully trapped in solid argon at 10 K, and their infrared spectra are registered and interpreted. Upon in situ irradiation of matrix-isolated 3QC with UV light (位 > 315 nm), significant reduction of the population of the less stable anti conformer was observed, while that of the conformational ground state (syn conformer) increased, indicating occurrence of the anti 鈫?syn isomerization. Upon irradiation at higher energy (位 > 235 nm), the syn 鈫?anti reverse photoreaction was observed. Interpretation of the structural, spectroscopic, and photochemical experimental data received support from quantum chemical theoretical results obtained at both DFT/B3LYP (including TD-DFT investigation of excited states) and MP2 levels, using the 6-311++G(d,p) basis set.