The hydrogen bond directed molecular recognition between 1,1‘-bis(ethenyl-4-pyridyl)ferrocene (1) and (±)-1,1‘-binaphthol (2)/(−)-1,1‘- binaphthol ((−)-2) has been studied by
cocrystallization in different solvents. Single-crystal X-ray structures reveal that 3:2, 2:1,
and 1:1 complexes (3, 4, and 5, respectively) of 1,1‘-bis(ethenyl-4-pyridyl)ferrocene (1) and
(±)-1,1-binaphthol (2) are formed in tetrahydrofuran, methanol, and ethanol, respectively.
5 has a noncentrosymmetric packing arrangement, and an efficiency of 0.3 times that of
urea in second-harmonic generation has been measured at 1295 nm. An X-ray crystal
structure of 6, 1:1 complex of 1 with (−)-2 in ethanol, reveals that all the molecular dipoles
are aligned in the same direction (i.e, a polar crystal), but 6 has modest nonlinear optical
properties (ca. 0.4 times that of urea).