Abstract
In this paper the temperature dependence of radiative deactivation of Pd- and Pt-porphin triplet states in Shpol'skii matrices has been studied in the temperature range of 4.2-210 K, Dramatic changes in the phosphorescence spectra, with increasing temperature, were observed. It has been proposed that this is due to the inclusion of thermally activated states of the Studied molecules in the ...
Abstract
In this paper the temperature dependence of radiative deactivation of Pd- and Pt-porphin triplet states in Shpol'skii matrices has been studied in the temperature range of 4.2-210 K, Dramatic changes in the phosphorescence spectra, with increasing temperature, were observed. It has been proposed that this is due to the inclusion of thermally activated states of the Studied molecules in the processes of radiative deactivation of triplet states. For Pd-porphin the T-1 -> T-0, emission is merely observed at liquid helium temperature. An increase in temperature leads to the activation of several radiative T-i -> S-0 transitions, so additional bands appear in the phosphorescence spectrum. In the case of Pt-porphin, temperature activation takes place as early as at liquid helium temperature. The degeneracy lifting of lowest T-1,T-2 states due to crystal field splitting was observed for both Pd- and Pt-porphins. The splitting value delta = Delta E(T-2 - T-1) has been measured in different matrices and the dependencies on both the metal ion in the given matrix and the matrix type for the given metal ion, have been revealed. The possibility of designing the luminescent molecular thermometers for cryogenic temperatures based on the high temperature sensitivity of the Pd- and Pt-porphin phosphorescence in n-alkane matrices. has been discussed. The workability of the dependence of Pd- and Pt-porphin phosphorescent properties on temperature in the design of the molecular thermometer family for the temperature range from a few K LIP to temperatures close to the melting point of n-alkane matrix ( 150200 K) is demonstrated. Copyright (C) 2008 Society of Porphyrins & Phthalocyanines.
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