Studies on interactions of excited cadmium and mercury atoms with secondary and tertiary alkyl- and silylamines in gas phase

The Cd(3P1)- and Hg(3P1)-photosensitized emissions of some secondary and tertiary alkyl- and silylamines have been investigated under conditions of steady illumination at 493 and 298 K, respectively. The emission bands were observed at around 440 nm in the cadmium-photosensitized reactions of these amines. In contrast, no appreciable emission bands were observed in the mercury-photosensitized reactions of these amines. However, upon addition of tert-butyl alcohol to the amine-mercury system, an emission band evolved at around 350 nm in the mercury-photosensitization. The peak-wavelengths for secondary and tertiary alkyl- and silylamines are slightly shorter than the values predicted from the correlations between the peak wavelength and the first ionization energy obtained in the cadmium- and mercury-photosensitized luminescence of ammonia and primary amines. The quenching efficiencies of the cadmium and mercury resonance lines by secondary alkyl- and silylamines are higher than those by tertiary alkyl- and silylamines. These observations suggest that the steric hindrance by the alkyl and silyl groups to the approach of the nitrogen atom in the amines to excited cadmium and mercury atoms seems to be an important factor for the stabilization of the exciplexes and the quenching of the resonance lines. The behavior of silylamines is similar to that of alkylamines in cadmium- and mercury-photosensitized reactions.

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► Cd- and Hg-photosensitized emissions of alkyl- and silylamines were investigated.
► The emissions from Hg-exciplexes of silylamines were observed for the first time.
► The Cd- and Hg-amine exciplexes possessed charge-transfer character.
► Secondary amines quenched Cd and Hg emissions more effectively than tertiary amines.
► The substituents of amines sterically affect their approach to excited Cd and Hg atoms.