“…Theoretical approaches provide useful insights for studying molecular systems before going into experimental investigations. Density functional theory (DFT) has been widely used as a theoretical approach (Anafcheh et al., 2016; Anafcheh and Ghafouri, 2014; Dheivamalar and Sugi, 2015; Handy et al., 1993; Handy et al., 1996; Hassani and Tavakol, 2014; Helgaker et al., 1999; Lee and Boo, 1996; Li et al., 2015; Stephens et al., 1994). Piperazine and its derivatives have been the target of research in the production of anti-microbial and anti-carcinogenic pharmacological agents, in a series of therapeutic processes and in the synthesis of complexes and clathrates (Beyeh et al., 2010; Hatnapure et al., 2012; Long et al., 2010; Parlak et al., 2009a, 2009b).…”