The Ambiguous Origin of Thermochromism in Molecular Crystals of Dichalcogenides: Chalcogen Bonds versus Dynamic Se-Se/Te-Te Bonds

Sajesh P Thomas; Ashi Singh; Arnaud Grosjean; Khidhir Alhameedi; Thomas Bjørn E Grønbech; Ross Piltz; Alison J Edwards; Bo B Iversen

doi:10.1002/anie.202311044

The Ambiguous Origin of Thermochromism in Molecular Crystals of Dichalcogenides: Chalcogen Bonds versus Dynamic Se-Se/Te-Te Bonds

Angew Chem Int Ed Engl. 2023 Nov 6;62(45):e202311044. doi: 10.1002/anie.202311044. Epub 2023 Sep 28.

Authors

Sajesh P Thomas^{1

2}, Ashi Singh¹, Arnaud Grosjean^{3

4}, Khidhir Alhameedi³, Thomas Bjørn E Grønbech², Ross Piltz⁵, Alison J Edwards⁵, Bo B Iversen²

Affiliations

¹ Department of Chemistry, Indian Institute of Technology Delhi, New Delhi, 110016, India.
² Department of Chemistry and iNano, Aarhus University, Langelandsgade 140, Aarhus, 8000, Denmark.
³ School of Molecular Sciences, University of Western Australia, Perth, WA 6009, Australia.
⁴ National Synchrotron Radiation Research Center, Hsinchu 30076 (Taiwan).
⁵ Australian Centre for Neutron Scattering, ANSTO, Lucas Heights, NSW 2234, Australia.

PMID: 37718313
DOI: 10.1002/anie.202311044

Abstract

We report thermochromism in crystals of diphenyl diselenide (dpdSe) and diphenyl ditelluride (dpdTe), which is at variance with the commonly known mechanisms of thermochromism in molecular crystals. Variable temperature neutron diffraction studies indicated no conformational change, tautomerization or phase transition between 100 K and 295 K. High-pressure crystallography studies indicated no associated piezochromism in dpdSe and dpdTe crystals. The evolution of the crystal structures and their electronic band structure with pressure and temperature reveal the contributions of intramolecular and intermolecular factors towards the origin of thermochromism-especially the intermolecular Se⋅⋅⋅Se and Te⋅⋅⋅Te chalcogen bonds and torsional modes of vibrations around the dynamic Se-Se and Te-Te bonds. Further, a co-crystal of dpdSe with iodine (dpdSe-I₂ ) and an alloy crystal of dpdSe and dpdTe implied a predominantly intramolecular origin of the observed thermochromism associated with vibronic coupling.

Keywords: Chalcogen Bond; Dynamic Bonds; Molecular Crystal; Structure-Property Relation; Thermochromism.

Abstract

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