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-pyrazino-phane, CHNS, (), and 2,5,8,11,14,17-hexa-thia-9.9-pyrazino-phane, CHNS, (), are regioisomers; -bis L1 and -bis L1, respectively. Both compounds have a central tetra-2,3,5,6-methyl-ene-pyrazine unit with two -S-CH-CH-S-CH-CH-S- chains, linking the methyl-ene C atoms at positions 2 and 6 and 3 and 5 on the pyrazine ring of , but linking the methyl-ene C atoms at positions 2 and 5 and 3 and 6 on the pyrazine ring of . Both compounds crystallize with half a mol-ecule in the asymmetric unit. The whole mol-ecule of is generated by inversion symmetry, with the pyrazine ring being located about a center of symmetry. The whole mol-ecule of is generated by twofold rotation symmetry, with the pyrazine N atoms being located on the twofold rotation axis. In compound , there are pairs of intra-molecular C-H⋯S contacts present, but none in compound . In the crystal of , there are no significant inter-molecular inter-actions present, while in the crystal of , mol-ecules are linked by pairs of C-H⋯S hydrogen bonds, forming corrugated layers lying parallel the 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.