To cite this article: Najwa-Alyani, M. N. N., Abdullah, N. A. F. & Ang, L. S. (2018). Stability analysis on the polymorphic compound of thiourea derivatives: 1,3-bis(1-(4-methylphenyl)ethyl)thiourea. J. Phys. Sci., 29(Supp. 1), 17–23, https://doi.org/10.21315/jps2018.29.s1.3
Polymorphism is the ability of a compound to form more than one crystalline
form in the solid state. Compounds having this ability would display different stabilities for different forms, hence affecting its applicability. Symmetrically substituted thiourea derivatives have been shown to be polymorphic due to the flexibility of the C–N bond. One of this type of compounds, known as 1,3-bis(1-(4-methylphenyl)ethyl)thiourea, is studied on its stabilities and ability to exist in different forms. Since the molecule of this compound was experimentally found to exist in trans-trans configuration, the stability of the cis-trans and cis-cis configurations are assessed using theoretical calculations. Rotations along the C–N bonds are performed using Gaussian 09 suite program. Level of method B3LYP, complemented by basis set DEF2-TZVP, is used. The stability of the molecules in different configurations is then studied in terms of its interactions using reduced density gradient. Apart from the original trans-trans configuration, with the difference of 0.024 eV, cis-trans configuration are also possible to exist. Next possible configuration is cis-cis with relative energy 1.8412 eV. Both the non-covalent CH…HN and CH…S interactions are found to provide stabilising effect in the cis-trans and trans-trans configurations.