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Molecular Motions in Fluctional Crystals: N‐Base Adducts of Bis(1,5‐cyclooctanediylboryl) Oxide
Author(s) -
Yalpani Mohamed,
Köster Roland,
Boese Roland
Publication year - 1992
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19921250206
Subject(s) - chemistry , adduct , mesophase , pyridine , molecule , crystallography , quinuclidine , intermolecular force , premelting , base (topology) , oxide , stereochemistry , phase (matter) , organic chemistry , melting point , mathematical analysis , mathematics
Abstract The adducts of bis(1,5‐cyclooctanediylboryl) oxide ( 1 ) with quinuclidine ( 2a ) and with pyridine ( 2b ) show an unusually large premelting endothermic phase transition. 2a has been investigated by 11 B‐NMR spectroscopy in the solid state and at various temperatures in its mesophase. The significant differences in the lattice packings of the molecules of the thermally stable adducts of 1 with 4‐methyl‐, 3‐bromo‐, and 4‐(dimethylamino)pyridine ( 2c—e ; X‐ray structural analysis) from those of 2a and 2b suggests that it is the unique molecular arrangement in the respective lattices of the latter two adducts which allows a smooth transition to a two‐dimensionally ordered mesophase. This is stabilized by intermolecular fluctuation of the N‐base molecules between the boron atoms of the neighbouring molecules of 1 .