Supramolecular aggregation of m-nitrobenzoic acid by C-H - O and O-H - O hydrogen bondings in the crystalline charge-transfer complexes with aromatichydrocarbons

Charge-transfer complexation of m-nitrobenzoic acid (1) with aromatic hydro carbons was found to exhibit size and shape selectivity: naphthalene or its 2,7-dimethyl and 2,3,6,7-tetramethyl derivatives failed to afford crystall ine complexes with 1 whereas yellow crystals containing a stoichiometric am ount of 2,3- or 2,6-dimethylnaphthalene, biphenylene, or anthracene were ob tained by the direct method in CH2Cl2. X-ray analyses on these complexes ha ve revealed dimer formation of 1 by O-H ... O hydrogen bonding, yet the imp ortant structural motif observed as a common feature is the two-dimensional sheetlike network, in which the dimers of 1 are further connected by C-H . .. O hydrogen bonding to form a series of inclusion lattices that incorpora te hydrocarbon guests. Such a supramolecular aggregation by C-H ... O bondi ng was proven to take a significant part in the recognition properties of 1 to differentiate the dimethylnaphthalene isomers in its complexation proce ss.