Computational and experimental structural analysis of 3-benzoyl-1,1-dimethyl-thiourea and its polymorph

Abstract 3-benzoyl-1,1-dimethyl-thiourea (3BDMT) is an important derivative of thiourea that has potential applications in different fields like medical, coordination and organic chemistry, pharmaceuticals, material science, and agriculture. This potential remains underexplored, leading to a lack of biological activity, electronic properties, or detailed structural characteristics of 3BDMT in the literature. This study discovered a new polymorph of 3BDMT and focuses on providing detailed information of the crystal structure, packing, molecular geometry, chemical stability, electronic properties, Hirshfeld surface (HS), and the interactions unique to both existing Form I and new Form II of 3BDMT. We used both experimental and computational approaches to establish this structural-property relationship. Form I and the new Form II were formed by concomitant crystallization and were characterized and confirmed by X-ray diffraction, differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy techniques. The existing Form I and new Form II of 3BDMT have different morphologies and crystal packing, resulting in different energy of interaction, stability, and structural properties. The geometry of the experimental structures was in excellent agreement with the calculated geometry of the molecules at the B3LYP-D3/def2-TZVP level of theory. The presence of π⋅⋅⋅π stacking energies in the new Form II contributes to its energy of interaction and making the structure more stable than the existing Form I . This correlates with the higher enthalpy of melting observed in the DSC analysis for the new Form II 3BDMT structure. This finding suggests that both structures are chemically stable, but the new Form II is more stable than the existing Form I . The compounds’ chemical stability is essential in the synthesis and formulation of the molecules for applications and the exploration of the compounds’ biological and catalytic activities. The large theoretical energy gap of 3.98 eV in both existing Form I and new Form II of 3BDMT indicates that the molecules are stable and might be chemically reactive, making them useful in organic synthesis, coordination, and chemistry. Since the synthesis of various thiourea groups has shown that there is potential for the thiourea derivatives, the discoveries from this study have shed insight and could help in harnessing the potential applications of 3BDMT.