Three trithiadiazepines and a trithiatriazepine

The structures of 6‐nitro‐1,3λ 4 δ 2 ,5,2,4‐trithiadiazepine [C 2 HN 3 O 2 S 3 , ( 1 )], 6,7‐dinitro‐1,3λ 4 δ 2 ,5,2,4‐trithiadiazepine [C 2 N 4 O 4 S 3 , ( 2 )], 1,3λ 4 δ 2 ,5,2,4‐trithiadiazepine‐6,7‐dicarbonitrile [C 4 N 4 S 3 , ( 3 )] and 7‐acetyl‐1,3λ 4 δ 2 ,5,2,4,6‐trithiatriazepine [C 3 H 3 N 3 OS 3 , ( 4 )] presented here include the most precise determinations of these seven‐membered 10 π‐electron aromatic ring systems published to date. Both ( 2 ) and ( 3 ) are sited around crystallographic twofold axes with half a molecule per asymmetric unit. Comparison with other published derivatives of these rings reveals the effect of substituents on bonding, conformations and intermolecular interactions, including π‐stacking. The deformation density analysis of ( 2 ) is consistent with the expected bonding electron density from other theoretical and experimental studies.