Role of alkyl chain linker in the conformational preferences of N′-phenylalkylsquaramates and bis-N,N′-diphenylalkylsquaramides

Conformational space of small molecules can be exploited to deploy the hierarchical nature of intermolecular interactions, such as hydrogen bonding and π-stacking in the crystal structures. Modulation of conformational space was achieved by varying the alkyl chain length in N′-phenylalkylsquaramates and bis-N,N′-diphenylalkylsquaramides, which were synthesized by condensation of dimethyl squarate with the corresponding phenyl alkylamines. In the crystal structures of these compounds, even though the catemeric N–H···O hydrogen bonding is the primary interaction and hierarchy in the secondary interactions consisting of π-stacking and H···H bonding leads to a large variation in molecular structures in the solid state.

Conformational variation in the alkyl chain linker connected to central squaramide unit is contingent to the variation in partner chain length.