1. Terahertz response of DL-alanine: experiment and theory
T J Sanders, J L Allen, J Horvat, R A Lewis Phys Chem Chem Phys. 2021 Jan 6;23(1):657-665. doi: 10.1039/d0cp05432a.
The terahertz (THz) spectrum of dl-alanine has been measured for the first time at cryogenic temperatures and with a pure sample. Several sharp absorptions are observed, over a wide frequency range (0.8-4.8 THz), at 8 K. The sample structure and purity were confirmed with both Raman spectroscopy and X-ray diffraction. Temperature dependent spectra revealed redshifting, with increasing temperature, for all modes except one at 2.70 THz. This mode exhibits blueshifting until ≈120 K, where it starts to redshift. A Bose-Einstein distribution has been used to model the frequency shift with temperature for the four lowest energy modes. Strong correlations between the fits and data indicate that these modes are caused by phonon excitation in an anharmonic potential. Density functional theory has also been used to identify the origin of these low frequency modes. They are attributed to large scale molecular vibrations.
2. dl-Alanine Covalently Bonded Giant Arsenotungstate with Rapid Photochromic and Decent Proton Conduction Properties
Kangting Zheng, Dongsheng Yang, Bingxue Niu, Yajing Ye, Pengtao Ma, Jingping Wang, Jingyang Niu Inorg Chem. 2022 Dec 19;61(50):20222-20226. doi: 10.1021/acs.inorgchem.2c03494. Epub 2022 Dec 8.
A dl-alanine covalently bonded giant arsenotungstate, namely, Na3Ba11H16[(AsW9O33)6{W2O5(H2O)(dl-Ala)}2{W3O6(H2O)(dl-Ala)}2{W2O5(dl-Ala)}] (1; dl-Ala = dl-alanine), has been synthesized and is composed of six [AsW9O33]9- fragments fused together via two [W2O5(H2O)(dl-Ala)]+ segments, two [W3O6(H2O)(dl-Ala)]5+ segments, and a [W2O5(dl-Ala)]+ segment. This complex represents the first carboxylate-based hybrid polyoxotungstate without the introduction of lanthanide ions. Besides, compound 1 demonstrates not only fast photochromic properties but also interesting proton conductivity properties, with an achieved conductivity of 2.830 × 10-4 S·cm-1 (65 °C, 75% relative humidity).
3. DL-Alanine
M Subha Nandhini, R V Krishnakumar, S Natarajan Acta Crystallogr C. 2001 May;57(Pt 5):614-5. doi: 10.1107/s010827010100261x. Epub 2001 May 15.
A determination of the structure of the title compound, C3H7NO2, leads to an accurate description of its molecular dimensions and crystal packing. As in the structure of the L-isomer, the molecules aggregate into alternating layers, each consisting of only one type of isomer. The molecules in each layer are interconnected through head-to-tail sequences generated by a cell translation and a 2(1) screw axis. Adjacent layers are interconnected by head-to-tail sequences generated by a glide plane.
