Mj. Politi et al., NEAR-INFRARED SPECTROSCOPIC INVESTIGATION OF INCLUSION COMPLEXES BETWEEN CYCLODEXTRINS AND AROMATIC-COMPOUNDS, Journal of physical chemistry, 99(38), 1995, pp. 14137-14141
Near infrared (NIR) absorption in the 900-1800 nm region has been used
to characterize and measure the association constants of the inclusio
n complexes between aromatic compounds (e.g., phenol, 4-chlorophenol,
sodium 2-naphthalenesulfonate, and sodium 2-pyrenesulfonate) and alpha
-, beta-, and gamma-cyclodextrin. It was found that the NIR method is
particularly suited for this type of study because upon forming comple
xes, the oscillator strengths of the C-H stretching [Delta nu = 2 (at
similar to 1650 nm) and 3 (at similar to 1120 nm)] overtone bands of t
he aromatic guest compounds were increased by at least 2-5-fold. The o
bserved increases are rationalized in terms of the enhancement in the
anharmonicity and the libration motions of the guest molecule in the C
D cavity. This enhancement effect facilitates the calculation of the a
ssociation constants of the inclusion complexes. As expected, the calc
ulated values are in relatively good agreement with previously determi
ned values.