New types of imine switches containing an alkylated para-bis(2-thienyl)phenylene moiety have been synthesized and studied. A bis substituted 2,4-diiminotoluene with phenylene-thienyl unit has also been synthesized and studied to evaluate the bifunctional switching of the imine bonds. Fast E/Z response in toluene and acetonitrile under 365 nm UV-light illumination was observed. It was found that the thermally unstable Z isomers are recovered to E ones in the dark by different rate constants depending on the solvent polarity, which refers to the T-type photochromic switches. The DFT calculations have shown that the switched Z forms are characterized by near perpendicular (T-shaped) orientation of the aromatic amine rings with respect to the thiophene one. The emission exhibited a significant bathochromism varying the solvent polarity, with Stokes shifts reaching values in the order 10 000 cm-1, while the absorption remained almost unaffected. Therefore, the relationship between E/Z switching response and solvent sensitivity of the emissions was estimated. The behaviour of the compounds suggests a rapid T-type E/Z/E isomerization cycle and dynamic control over the light-driven geometrical changes of the imine bond.
Fast E/Z UV-light response T-type photoswitching of phenylene-thienyl imines
Blasi, Davide;
2022-01-01
Abstract
New types of imine switches containing an alkylated para-bis(2-thienyl)phenylene moiety have been synthesized and studied. A bis substituted 2,4-diiminotoluene with phenylene-thienyl unit has also been synthesized and studied to evaluate the bifunctional switching of the imine bonds. Fast E/Z response in toluene and acetonitrile under 365 nm UV-light illumination was observed. It was found that the thermally unstable Z isomers are recovered to E ones in the dark by different rate constants depending on the solvent polarity, which refers to the T-type photochromic switches. The DFT calculations have shown that the switched Z forms are characterized by near perpendicular (T-shaped) orientation of the aromatic amine rings with respect to the thiophene one. The emission exhibited a significant bathochromism varying the solvent polarity, with Stokes shifts reaching values in the order 10 000 cm-1, while the absorption remained almost unaffected. Therefore, the relationship between E/Z switching response and solvent sensitivity of the emissions was estimated. The behaviour of the compounds suggests a rapid T-type E/Z/E isomerization cycle and dynamic control over the light-driven geometrical changes of the imine bond.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
