Surface Photochemistry: Organic Molecules within Nanocavities of Calixarenes

Luis   F.   Vieira Ferreira; Isabel   L.   Ferreira Machado

Abstract

In order to gain more information regarding photochemical processes in heterogeneous environments (opaque or powdered samples) laser induced time resolved luminescence and diffuse reflectance transient absorption spectroscopies were used for the study of benzophenone (and other neutral organic molecules) as guests and p-tert-butylcalix[n]arenes with n = 4, 6 and 8 (HnCLX[n]) and partially or totally O-propylated p-tert-butylcalix[4]arenes (HnPrmCLX[4], n = 2, 1 and 0; m = 2, 3 and 4, respectively) were used as hosts. One of the main conclusions was that the solid support can deeply affect or even control the photochemistry of an adsorbed probe. A simple new methodology for lifetime distribution analysis of the decay of the probes included into calixarenes and other nanocavities was applied with success for decay data obtained with the use of intensified charge couple devices, i.e. intensified charge couple devices, ICCDs. Diffuse reflectance laser flash photolysis and gas chromatography - mass spectrometry techniques also provided complementary information, the former about transient species and the latter regarding the final products formed after light absorption.

Keywords: Calixarenes, inclusion complex formation, nanocavities, time resolved laser induced luminescence spectroscopy, diffuse reflectance laser flash photolysis