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Organic pigments such as phthalocyanines (I), naphthalocyanines (II), and diimides of perylenetetracarboxylic acid (III) are of basic as well as application-related interest

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We report on persistent spectral hole-burning studies of phthalocyanine-zinc derivatives encapsulated in the pores of an A1P04-5 alumophosphate molecular sieve. Persistent holes are only formed if the porous crystal is saturated with additional solvent molecules, e.g. water or chloroform. The characteristics of the hole formation indicate that the burning mechanism is non-photochemical due to interaction with the two-level systems of the amorphous solvent shell within the pores. The hydrated molecular sieve allows efficient hole formation up to 80 K, the highest temperature for which stable non-photochemical holes have been reported so far. This is attributed to the combined effect of a stiff matrix and a hydrogen-bonded amorphous environment leading to a high Debye-Waller factor. The inorganic crystal provides a stiff framework in which water constitutes an amorphous hydrogen-bonded environment containing an appreciable number of high-barrier two-level systems.The data are discussed in the context of the prerequisites of high-temperature hole-burning, especially the distribution of barriers and the temperature dependence of the Debye-Waller factor.