Resumo:

Intermolecular interactions are important for the understanding of molecular self-organization of new solids with desired physical and chemical properties. In this work crystals of bis[(1-diaminomethylene)thiouron-1-ium] naphthalene-1,5-disulfonate were grown using solution growth technique. A single-crystal sample was characterized by X-ray diffraction and FTIR spectroscopy. The compound crystallizes in centrosymmetric group C2/c of the monoclinic system. The conformations of the cation bis[1-(diaminomethylene)thiouron-1-ium] and the anion naphthalene 1,5-disulfonate are shown in figure 1. Experimental: Commercially available 2-imino-4-thiobiuret, which is in the fact the tautomeric form (schemme 1), 1-(diaminomethylene)thiourea and the 1,5-naphthalenedisulfonic acid tetrahydrate were added to hot water in a molar proportion of 2:1. After several days, transparent colourless crystals were formed. The crystals have been separated by filtration and dried in air. Analysis: Calculated for C14H20N8O6S4: C, 32.05; N, 21.26; O, 18.30; S, 24.45 and H, 3.84%. Found: C, 31.88; N, 21.32; O, 18.63; S, 24.39 and H, 3.78%. A colourless 0.05 mm x 0.02 mm x 0.05 mm sample was mounted on a Gemini Oxford CCD Diffractometer provided with a liquid nitrogen low-temperature device. IR data measured with an ABB Bomen MB 3000 FTIR spectrometer using KBr pellets. Comments: The X-ray analysis shows that the sulfonate group is deprotonated and the protons are transferred to the central nitrogen atom of 1-(diaminomethylene)thiourea molecule. The asymmetric unit (figure 1) is formed by one unit of cation 1-(diaminomethylene)thiouron-1-ium and a half of the anion naphthalene-1,5 disulfonate, the other half of the compound is obtained by inversion at the centre of the naphthalene ring. At room and low temperature, the system remains isostructural. The conformation of the cation is not strictly planar, but twisted, stabilized by one intramolecular hydrogen bond N3-H3B···S1 in a S(6) graph set (table 2). Both arms of the 1-(diaminomethylene)thiouron-1-ium are rotated around C-N bond involving the central N1 atom. Compared to neutral 1-(diaminomethylene)thiourea, where the observed dihedral angle is 22.2(1)°, the protonation on N1 reduces the steric effect of lone pair of electrons and the dihedral angle decreases to 6.0(3)°. The conformation of the anion compares to bis(dihydronium) naphthalene-1,5-disulfonate, with one oxygen (O3) laying on the ring. In the crystal (figures 2 and 3) the opposite charges interact via almost linear hydrogen bonds forming three graph sets