*3.3. Synthesis of Anhydrous 1,2-Bis[(1-methyl-1H-imidazole-2-yl)thio]ethane (2a)*

Method (A) Dihydrochloride tetrahydrate **2b** (300 mg) was dissolved in 30 mL of water and neutralized with 1M Na2CO<sup>3</sup> to pH 7.0, followed by extraction with dichloromethane (3 × 10 mL), washed with brine and dried with anhydrous Na2SO4. Evaporation of the solvent in vacuo to dryness yielded crude 1,2-bis[(1-methyl-1*H*-imidazole-2-yl)thio]ethane (**2a**, 160 mg, 84%) in a form of white powder. Recrystallization of dry crude **2a** from dry dichloromethane under low humidity conditions gave pure anhydrous **2a**. Melting point (DSC, onset): 89 ◦C (lit: 88-90 ◦C) [5], <sup>1</sup>H NMR (DMSO-*d6*, 600 MHz/ppm): N-CH<sup>3</sup> (s, 6H) 3.57, H-C4 (d, 2H) 7.24 *J* = 1.2 Hz, H-C5 (d, 2H) 6.94 *J* = 1.2 Hz, S-CH<sup>2</sup> (s, 4H) 3.21; <sup>13</sup>C NMR (DMSO-*d6*, 151 MHz/ppm): N-CH<sup>3</sup> 32.79, C4 123.29, C5 128.53, C2 139.23, S-CH<sup>2</sup> 33.30. The structure of **2a** was confirmed by single crystal X-ray diffraction analysis.

Method (B) Dihydrate **2c** (100 mg) was dried under reduced pressure of 200 mbar at 55 ◦C for 60 min and anhydrous form **2a** (71 mg, 81%) was obtained. DSC thermogram and XRPD diffractogram of the obtained sample were identical to the thermogram and diffractogram of the **2a** sample obtained by Method A.
