Abstract
The polycyclic aromatic hydrocarbon (PAH) triphenylene (TP) has been reacted with halo-pentafluorobenzene (XF5, X = Br, I) and 1,4-dihalo-tetrafluorobenzene (X2F4, X = Br, I) to yield the corresponding cocrystals TP·BrF5, TP·Br2F4, TP·IF5, and TP·I2F4 form I. These materials have been synthesized by dissolving TP into an excess of liquid or molten coformer, and single crystals have been grown via seeding chloroform solutions. They have been fully characterized by a combination of techniques including X-ray diffraction, Raman spectroscopy, and luminescence spectroscopy in the solid state. TP·I2F4 form I was found to undergo a single-crystal to single-crystal (SCSC) polymorphic phase transition induced by temperature (when cooled down to 100 K) leading to the new form TP·I2F4 form II, which is transformed back into the first structure when brought again at RT. This behavior was confirmed also by Raman spectroscopy. Upon cocrystallization and as a result of the external heavy atom effect, all crystalline mat...
Highlights
Solid luminescent materials constitute an attractive field of research, from a theoretical point of view, and because of their potential applications in the development of optoelectronic devices
TP·I2F4 form I was found to undergo a single-crystal to single-crystal (SCSC) polymorphic phase transition induced by temperature leading to the new form TP·I2F4 form II, which is transformed back into the first structure when brought again at RT
Single crystal XRD analysis for all cocrystals had to be carried out at low temperature (100K) because all samples suffered degradation under the X-ray beam except TP·I2F4 formI, for which it was possible to collect an additional dataset at RT
Summary
Solid luminescent materials constitute an attractive field of research, from a theoretical point of view, and because of their potential applications in the development of optoelectronic devices. A material can be considered an UOP emitter when its luminescence lifetime is longer than 100 ms.[4]. It has been reported for polymers,[9,10] host-guest systems,[11,12,13] carbon dots dispersed into polymeric matrices,[14] self-assembled supramolecular frameworks or H-aggregates[15] as well as in single-component small molecules like iminodibenzyl[16] and carbazol-derivatives based crystalline materials.[17].
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