C–H ⋯ O hydrogen bond patterns in crystalline nitro compounds: studies in solid-state molecular recognition

Several C–H ⋯ O hydrogen bond patterns (I–V) have been studied in the crystal structures of organic nitro compounds. It is shown that NO2 and NMe2 groups have complementary functionalities in C–H ⋯ O mediated molecular recognition in the solid state (pattern I). The role of co-operativity in stabilising these weakly hydrogen bonded networks has been studied computationally by examining aggregates of the prototype molecule N,N-dimethylnitroamine. Other geometrically characteristic C–H ⋯ O patterns (II–V) are found commonly in these crystal structures especially among nitroalkenes and nitroaromatics and such patterns are expected to be of utility in supramolecular assembly.