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High-Temperature Reversible Martensitic Transition in an Excited-State Intramolecular Proton Transfer Fluorophore
journal contribution
posted on 2019-10-16, 22:16 authored by Fabio Borbone, Angela Tuzi, Antonio Carella, Domenica Marabello, Stefano Luigi Oscurato, Stefano Lettieri, Pasqualino Maddalena, Roberto CentoreReversible
martensitic transitions in molecular crystals are an
unusual phenomenon, and most of the cases reported in the literature
occur at relatively low temperatures. The title compound, 2-(5-(benzo[d]thiazol-2-yl)-1,3,4-oxadiazol-2-yl)-5-(diethylamino)phenol
(DBOX), reveals an interesting and rich polymorphism,
characterized by a reversible single-crystal-to-single-crystal transition
occurring at 185 °C. The transition can be repeated several times
on a single crystal without degradation and/or damage. The crystal
structure of this high-temperature phase (II) and two low-temperature
polymorphs (I and III) are solved by single-crystal X-ray analysis
to fully elucidate the mechanism of the reversible I → II transition.
Changes in the molecular packing are preceded by anomalous thermal
expansion and evolve as slipping/rotation motions of molecular dimers,
activated by steric disengagement along the anomalous expansion direction
and resulting in the reversible contraction of the long crystal axis
and lateral expansion. Uncommon panchromatic- and white-emitting fluorescence
properties of the reported compound are also described.
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crystal axissingle-crystal X-ray analysiscrystal structureexpansion directionExcited-State Intramolecular Proton Transfer Fluorophore Reversible martensitic transitionsHigh-Temperature Reversible Martensitic TransitionIIItitle compoundUncommon panchromaticIIDBOXwhite-emitting fluorescence propertiessteric disengagementsingle-crystal-to-single-crystal transition
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