*3.4. Synthesis of 1,2-Bis[(1-methyl-1H-imidazole-2-yl)thio]ethane Dihydrate (2c)*

Method (A) Crude **2a** obtained by neutralization of dihydrochloride tetrahydrate **2b** (160 mg) was dissolved in an acetone/water mixture (1:1). After prolonged standing of the solution without stirring at room temperature, crystals of the pure dihydrate form **2c** (133 mg, 73%) were obtained. Melting point (DSC, onset, 65 ◦C). Structure of **2c** was confirmed by the single crystal X-ray diffraction analysis.

Method (B) Pure anhydrous form **2a** (300 mg) was dissolved in an acetone/water mixture (1:1). After prolonged standing of the solution without stirring at room temperature, pure crystals of the dihydrate form **2c** (238 mg, 70%) were obtained. DSC thermogram and XRPD diffractogram of the so obtained sample were identical to the thermogram and diffractogram of the **2c** sample obtained by Method A.
