Synthesis and crystal structure of N,N-dimethylformamide solvate of thiocyanuric acid

Abstract

Considerable attention has been paid recently to crystal engineering; which involves the design and preparation of new crystalline molecular solids with desired properties [1–4]. Crystalline materials with specific properties find applications in petrochemical industry for separation and purification. Moreover, crystal engineering provides products designed for manufacturing catalysts and high-valued chemicals for specific purposes. Recently, crystalline materials find application in pharmaceutical, food and microelectronic industries [5]. The main two strategies that are used for crystal engineering are based on hydrogen bonding and coordination bonding [6]. Since the hydrogen bonding is usually stronger and more directional than the other methods, more new crystal materials have been prepared based on this method. We are here able to design crystalline materials based on hydrogen bonding and study their solid state structures. N, N-dimethylformamide (DMF)-solvate of thiocyanuric acid (TCUA) and dimethyl sulfoxide (DMSO)-solvate of thiocyanuric acid (TCUA) were successfully prepared at room temperature in the presence of aqueous solution of sodium nitrate (NaNO3). To the best of our knowledge, this study presents the easy, modest, and rapid method to prepare co-crystal formation based on thiocyanuric acid (TCUA) and solvent-containing hydrogen bonding functionality. In this paper, we present the most effective method to synthesize the co-crystals of (TCUA), and as evidence, the crystal structure of (TCUA) in DMF is fully studied and presented in this paper. The N,N-dimethylformamide (DMF)-solvate of thiocyanuric acid (TCUA) was successfully prepared at room temperature, and was characterized spectroscopically by nuclear magnetic resonance (NMR) and single-crystal X-ray diffraction (SXRD). The asymmetric unit of the title compound contains one molecule of thiocyanuric acid (TCUA) features an almost planar six-membered ring having exocyclic C-S thione double bonds and one molecule of N,N-dimethylformamide (DMF). It was crystallized in the monoclinic, P21/c with unit cell parameters of a = 9.6255 (4) Å, b = 12.6864 (5) Å, c = 9.1367 (4) Å, β = 90.095 (2)°, V = 1115.71 (8) Å3, Z = 4. The structure is composed of 1-D TCUA ribbons formed via N–H–S hydrogen bonds. The ribbons are separated by DMF molecules, which are bridged to the ribbons by N–H–O hydrogen bonds. The ribbons and their DMF molecules form 2-D sheets which are in turn π-stacked to build up a layered, 3-D structure. The proton and carbon-13 NMR studies confirmed the formation of such solvate between DMF and TCUA.