Binary and ternary charge-transfer complexes using 1,3,5-tri­nitro­benzene

Three binary and one ternary charge-transfer complexes have been made using 1,3,5-tri­nitro­benzene, viz. 1,3,5-tri­nitro­benzene–2-acetylnaphthalene (1/1), C(6)H(3)N(3)O(6)·C(12)H(10)O, (I), 1,3,5-tri­nitro­benzene–9-bromo­anthracene (1/1), C(14)H(9)Br·C(6)H(3)N(3)O(6), (II), 1,3,5-tri­nitro­benzene–methyl red (1/1), C(15)H(15)N(3)O(2)·C(6)H(3)N(3)O(6), (III) (systematic name for methyl red: 2-{(E)-[4-(di­methyl­amino)­phen­yl]diazen­yl}benzoic acid), and 1,3,5-tri­nitro­benzene–1-naphthoic acid–2-amino-5-nitro­pyridine (1/1/1), C(6)H(3)N(3)O(6)·C(11)H(8)O(2)·C(5)H(5)N(3)O(2), (IV). All charge-transfer complexes show alternating donor and acceptor stacks, which have weak C—H⋯O hydrogen bonds perpendicular to the stacking axis. In addition, complex (IV) is a crystal engineering attempt to modify the packing of the stacks by inserting a third mol­ecule into the structure. This third mol­ecule is stabilized by strong hydrogen bonds between the carb­oxy­lic acid group of the donor mol­ecule and the pyridine acceptor mol­ecule.