Kaleta Jiří, Bastien Guillaume, Wen Jin, Dračínský Martin, Tortorici Edward, Císařová Ivana, Beale Paul D, Rogers Charles T, Michl Josef
Institute of Organic Chemistry and Biochemistry of the CAS , Flemingovo nám. 2 , 166 10 Prague 6 , Czech Republic.
Department of Chemistry , University of Colorado , Boulder , Colorado 80309-0215 , United States.
J Org Chem. 2019 Jul 5;84(13):8449-8467. doi: 10.1021/acs.joc.9b00553. Epub 2019 Jun 14.
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.
合成了新一代分子内偶极-偶极间距不同的双哒嗪分子转子。所有转子分子在三（邻苯二氧基）环三磷腈（TPP）主体中形成大量包合物。介电谱结果拟合为一对九态模型，该模型考虑了在TPP主体通道内局部三重偶极旋转势的对齐或相反可能取向时相邻偶极的相互作用。结果表明，在100至200K范围内，偶极-偶极相互作用强度使偶极优先占据低能量构型的一个子集。结果还表明，在3位和6位带有乙炔基取代基的哒嗪比带有一个乙炔基和一个叔丁基的哒嗪具有略高的旋转势垒（3.2 - 3.5千卡/摩尔）。冷却时，这些势垒极大地降低了势阱之间的热跃迁速率，以至于包合物无法达到有序的偶极基态。
