Self-Assembly of Organometallic−Organic Hybrid Supramolecular Arrays from Ferrocenyl Dipyridines and Aromatic Carboxylic Acids

The ferrocenyl bipyridines, 1,1‘-bis[2-(4-pyridyl)vinyl]ferrocene (1a) and 1,1‘-bis[2-(3-methyl-4-pyridyl)vinyl]ferrocene (1b), were cocrystallized with aromatic acids such as 4-alkoxybenzoic acids (2), terephthalic
acid (3a), isophthalic acid (3b), phthalic acid (3c), and trimesic acid (4). Eight complexes were obtained as single
crystals, and their crystal structures were successfully determined by X-ray analysis. When 1a was assembled with
2, a [1 + 2] self-assembly occurred, to generate supramolecular arrays in which one molecule of 1a and two molecules
of 2 were held together through hydrogen bonding. In the cocrystallization of ferrocenyl bipyridines with benzene
dicarboxylic acid (3a, 3b, and 3c), proton transfer occurred depending on the kind of benzene dicarboxylic acid.
Thus, the cocrystals of 1a+·3b-, 1b+·3b-, and 1b+·3c- consist of proton-transferred ionic supramolecular species,
whereas that of 1b·3a are composed of [2 + 2] assembled cyclic supramolecular structures. Complexation of 1a with
4 afforded the [2 + 3] self-assembly with an intriguing prismatic cagelike structure.