The crystal structures, Hirshfeld surface analyses and energy frameworks of two hexa-thia-pyrazino-phane regioisomers; 2,5,8,11,14,17-hexa-thia-[9.9](2,6,3,5)-pyrazino-phane and 2,5,8,11,14,17-hexa-thia-[9.9](2,5,3,6)-pyrazino-phane.

The title thia-pyrazino-phanes, 2,5,8,11,14,17-hexa-thia-[9.9](2,6,3,5)-pyrazino-phane, C16H24N2S6, (I), and 2,5,8,11,14,17-hexa-thia-[9.9](2,5,3,6)-pyrazino-phane, C16H24N2S6, (II), are regioisomers; m-bis L1 and p-bis L1, respectively. Both compounds have a central tetra-2,3,5,6-methyl-ene-pyrazine unit with two -S-CH2-CH2-S-CH2-CH2-S- chains, linking the methyl-ene C atoms at positions 2 and 6 and 3 and 5 on the pyrazine ring of I, but linking the methyl-ene C atoms at positions 2 and 5 and 3 and 6 on the pyrazine ring of II. Both compounds crystallize with half a mol-ecule in the asymmetric unit. The whole mol-ecule of I is generated by inversion symmetry, with the pyrazine ring being located about a center of symmetry. The whole mol-ecule of II is generated by twofold rotation symmetry, with the pyrazine N atoms being located on the twofold rotation axis. In compound I, there are pairs of intra-molecular C-H⋯S contacts present, but none in compound II. In the crystal of I, there are no significant inter-molecular inter-actions present, while in the crystal of II, mol-ecules are linked by pairs of C-H⋯S hydrogen bonds, forming corrugated layers lying parallel the ac plane. The Hirshfeld surfaces and the energy frameworks of the two regioisomers indicate little difference in the inter-atomic contacts, which are dominated by dispersion forces.