Bulk Inclusions of Double Pyridazine Molecular Rotors in Hexagonal Tris(o-phenylene)cyclotriphosphazene

0507863 - ÚOCHB 2020 RIV US eng J - Journal Article
Kaleta, Jiří - Bastien, Guillaume - Wen, Jin - Dračínský, Martin - Tortorici, E. - Císařová, I. - Beale, P. D. - Rogers, C. T. - Michl, Josef
Bulk Inclusions of Double Pyridazine Molecular Rotors in Hexagonal Tris(o-phenylene)cyclotriphosphazene.
Journal of Organic Chemistry. Roč. 84, č. 13 (2019), s. 8449-8467. ISSN 0022-3263. E-ISSN 1520-6904
Institutional support: RVO:61388963
Keywords : solid state * surface inclusion * motion
OECD category: Organic chemistry
Impact factor: 4.335, year: 2019
Method of publishing: Limited access
https://pubs.acs.org/doi/10.1021/acs.joc.9b00553

A new generation of double pyridazine molecular rotors differing in intramolecular dipole-dipole spacing was synthesized. All rotor molecules formed bulk inclusions in a tris(o-phenylenedioxy)cyclotriphosphazene (TPP) host. Results of dielectric spectroscopy were fitted to a pair of nine-state models that accounted for interactions of neighboring dipoles at either an aligned or opposed possible orientation of the local threefold dipole rotation potentials within a channel of the TPP host. The results indicate dipole- dipole interaction strengths at the 100 to 200 K scale that lead dipoles to preferentially populate a subset of low-energy configurations. They also reveal that pyridazines with ethynyl substituents in 3- and 6-positions have slightly higher rotational barriers (3.2-3.5 kcal/mol) than those carrying one ethynyl and one tert-butyl group (1.9-3.0 kcal/mol). Upon cooling, these barriers reduce the rate of thermal transitions between the potential wells so much that the inclusions cannot achieve ordered dipolar ground states.
Permanent Link: http://hdl.handle.net/11104/0298820