Effect of temperature on the conformation of dibenzotropone adsorbed on montmorillonites

Z. Grauer*, S. Yariv, L. Heller-Kallai, D. Avnir

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

The nature of the adsorption complex formed between dibenzotropone (DBT) and montmorillonite at elevated temperatures is strongly dependent on the interlayer cations. This was shown by electronic and IR spectra, by X-ray diffraction, and by study of the effects of gradual heating of the samples on these analyses. All samples exhibited significant red shifts of the electronic spectra of DBT into the visible range. These red shifts are attributed to two factors, both contributing to the enhancement of the tropylium planar character of DBT: hydrogen-bonding of acidic interlayer water to the carbonyl group, imparting positive charge to the tropone ring; and π interactions between the aromatic moiety and the oxygen planes. The position of the maximum was temperature-dependent for Cu-, Ni-, Al- and Fe-montmorillonites, for which heating (100°) under vacuum increased the red shift. The organic molecule assumes a planar conformation and is oriented parallel to the clay layers. IR spectra confirming this conformational orientation of DBT are discussed. The basal spacings of the DBT montmorillonite associations depend on the number of water and DBT sheets present in the interlayers. Layers with one or two sheets of DBT and with up to two sheets of water could be distinguished, leading to a maximum spacing of 20.4 Å.

Original languageEnglish
Pages (from-to)49-64
Number of pages16
JournalJournal of Thermal Analysis
Volume26
Issue number1
DOIs
StatePublished - Jan 1983

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