I. INTRODUCTION
A biocide is a chemical substance or microorganism, which can deter, render harmless, or exert a controlling effect on any harmful organism by chemical or biological means, and therefore are commonly used in medicine, agriculture, forestry, and industry. In particular, methylene bis(thiocyanate) (MBT, Figure 1) is a microbiocidal agent mainly used in industrial water cooling systems and paper mills as an inhibitor of algae, fungi, and bacteria (Braun et al., Reference Braun, Birck, Singer, Schnuelle, van der Woude and Löhr2006). The crystal structure of MBT was studied from single-crystal X-ray diffraction (Konnert and Britton, Reference Konnert and Britton1971) and is reported in the CSD-database with refcode MEDTCN (Allen, Reference Allen2002; CSD, version 5.35, February).
Figure 1. Structural formula of methylene bis(thiocyanate).
This compound crystallize in the monoclinic space-group I2/c (No. 15), a non-standard setting of C2/c (No. 15), with a = 6.667(11) Å, b = 8.042(13) Å, c = 11.101(19) Å, and β = 105.25(25)°. Recently, experimental and theoretical vibrational studies using density functional theory (DFT) calculation was performed for this molecule (Fernández et al., Reference Fernández, Gómez, Tótaro, Coronel and Varetti2013). However, an experimental X-ray powder diffraction pattern for MBT has not been reported in the PDF-database (ICDD, Reference Kabekkodu2011). In this paper, we present powder X-ray diffraction data for well-synthesized MBT.
II. EXPERIMENTAL
A. Synthesis
MBT was prepared reacting sodium thiocyanate (NaSCN) and methylene bromide (CH2Br2), following a procedure reported in the literature (Muthusubramanian et al., Reference Muthusubramanian, Sundara Rao and Mitra2003). MBT, an organosulfur compound, is a yellow granular solid with sulfur-like smell (m.p. 102–104 °C).
B. Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy
The FTIR absorption spectrum was obtained as KBr pellet using a Perkin-Elmer 1600 spectrometer. 1H-NMR and 13C-NMR spectra were recorded on a Bruker Avance 400 model spectrometer in DMSO-d6 solution. Infrared spectrometry showed stretching vibrations; 3017, 2956, and 1380 cm−1 (CH2), 2168 cm−1 (C–N), 867 cm−1 (S–C–S), 700 cm−1 (S–CN), and NMR; 1H NMR (400 MHz, DMSO-d 6) δ = 4.92 (s, H2). 13C NMR (100.6 MHz, DMSO-d 6) δ = 119.16 (CN), 37.88 (CH2).
C. X-ray powder diffraction data
For the X-ray analysis, a small quantity of the sample was ground mechanically in an agate mortar and pestle. The resulting fine powder, sieved to 106 μm, was mounted on a flat zero-background holder covered with a thin layer of petroleum jelly. The X-ray powder diffraction data were collected at room temperature 293(1) K, in θ/θ reflection mode using a Philips diffractometer with PW-1150/25 goniometer and monocromatized CuKα radiation (λ = 1.5406 Å). The diffractometer was operated at 40 kV and 25 mA. The specimen was scanned from 10° to 80°2θ, with a step size of 0.02° and counting time of 10 s per step. Silicon (SRM 640) was used as an external standard. The analytical software package WinPLOTR (Roisnel and Rodríguez-Carvajal, Reference Roisnel and Rodriguez-Carvajal2001) was used to establish the positions of the peaks and to determine the peak intensities of the diffraction peaks.
III. RESULTS AND DISCUSSION
The X-ray powder pattern of MBT is shown in Figure 2. The 20 first peak positions were indexed using the program DICVOL06 (Boultif and Louër, Reference Boultif and Louër2004), which gave a unique solution in a monoclinic cell. The systematic absences study (hkl: h + l = 2n) indicated an I-type cell consistent with the reported crystal structure (Konnert and Britton, Reference Konnert and Britton1971). The complete powder diffraction dataset was reviewed in the monoclinic space group I2/c, using the program NBS*AIDS83 (Mighell et al., Reference Mighell, Hubbard and Stalick1981). All measured lines were indexed and were consistent with the monoclinic space group I2/c (No. 15). From this analysis, the refined unit-cell parameters obtained were: a = 6.6888(4) Å, b = 8.0616(6) Å, c = 11.089(1) Å, β = 105.33(1), V = 576.68(7) Å3, and Z = 4, with figures of merit M 20 = 56.0 (de Wolff, Reference de Wolff1968) and F 30 = 43.8 (0.0079, 87) (Smith and Snyder, Reference Smith and Snyder1979). The resulting X-ray powder diffraction data for MBT, together with the observed and calculated 2θ, the d-spacing's as well as the relative intensities of the reflections, are given in Table I. In order to confirm the unit-cell parameters, an Le Bail refinement (Le Bail, Reference Le Bail2005) of the whole diffraction pattern without the structural model was carried out using the FULLPROF program (Rodríguez-Carvajal, Reference Rodriguez-Carvajal2013). Figure 3 shows a very good fit between the observed and calculated patterns.
Figure 2. X-ray powder diffraction pattern of methylene bis(thiocyanate).
Figure 3. (Color online) Le Bail refinement of methylene bis(thiocyanate).
Table I. X-ray powder diffraction data of methylene bis(thiocyanate).
ACKNOWLEDGEMENTS
This work was supported by Consejo de Desarrollo Científico, Humanístico y Tecnológico (CDCHTA-ULA, grant no. C-1853-13-A), FONACIT (Fondo Nacional de Investigaciones Científicas, grant no. LAB-97000821) in Venezuela, and CONICET (Consejo Nacional de Investigaciones Científicas), UNLP (Universidad Nacional de La Plata), and CIUNT (Consejo de Investigaciones de la Universidad Nacional de Tucumán) in Argentina.
SUPPLEMENTARY MATERIALS AND METHODS
The supplementary material for this article can be found at http://www.journals.cambridge.org/PDJ
