A FLUORESCENT TEMPERATURE PROBE BASED ON THE ASSOCIATION BETWEEN THE EXCITED-STATES OF 4-(N,N-DIMETHYLAMINO)BENZONITRILE AND BETA-CYCLODEXTRIN

A temperature probe based on the fluorescence properties of the mo exc ited states of 4-(N,N-dimethylamino)benzonitrile (DMABN) in equilibriu m with beta-cyclodextrin (CD) in aqueous solution is presented. The fl uorescence intensity of the Franck-Condon excited state (FB) as a func tion of temperature shows a straight line with a correlation better th an 0.99 in the 283-308 K temperature interval. On the other hand, the fluorescence intensity of the misted internal charge-transfer state (F A) remains constant in the same temperature interval because the bindi ng of DMABN in the A state to CD is isoenthalpic and entropy driven. It is found that the FA/FB ratio is independent of the excitation inte nsity at a specified temperature, shows a linear relationship with tem perature, and allows temperature measurements with a resolution of +/- 2.5 K.