Low-wavenumber Raman spectra of l-tyrosine, l-tyrosine hydrochloride, and l-tyrosine hydrobromide crystals at high temperatures

Publication date: Available online 3 August 2019Source: Journal of Physics and Chemistry of SolidsAuthor(s): C.A.A.S. Santos, R.J.C. Lima, P.F. Façanha Filho, A.O. dos Santos, J.A. Lima, P.T.C. FreireAbstractCrystals of l-tyrosine and semiorganic l-tyrosine hydrochloride and l-tyrosine hydrobromide, known for their nonlinear optical properties, were studied by Raman spectroscopy in the temperature range from 298 to 453 K. Hydrogen bonding at room temperature and thermal decomposition are correlated with Raman bands in the low-wavenumber region at approximately 120 cm−1. The detailed analysis of these bands and the temperature dependence of their wavenumbers show an interesting correlation between hydrogen bonds, vibrational properties, and thermal decomposition. In particular, we note a correlation between the lengths of the N–H … X bonds and the wavenumber of a low-wavenumber band and that the introduction of Br and Cl in the l-tyrosine hydrochloride and l-tyrosine hydrobromide structures does not substantially modify the O–H⋯O bonds when compared with the l-tyrosine crystal. Additionally, the hydrophobic character of the interactions apparently does not change during heating, and there is no evidence for the breakdown of the hydrophobic interactions.Graphical abstract

Source: Journal of Physics and Chemistry of Solids - August 3, 2019 Category: Physics Source Type: research