octahedral the sixth position being occupied by other chlorine
atoms linked to adjacent molecules with the resulting formation
of either dimers or longer chains [15]. The conformation of the
piperazine six-membered ring can be described in terms of Cremer
& Pople puckering coordinates [16], i.e. evaluating the parameters
Q (total puckering amplitude), q2, q3, h and u. Their calculated
value for N1–C1–C2–N2–C3–C4 ring is: Q = 0.564 Å, q2 = 0.025 Å,
q3 = 0.564 Å, h = 177.39 and u = 118.44 corresponding to the
most stable chair conformation (Fig. 3).