Title : Photochemical and thermal reactivity of bipyridyl-functionalized hydrazones and their ON / OFF functionality
Arylizatin hydrazones in the presence of basic ions (F-, CH3 COO- ) provide the corresponding anions by the NH group hydrogen cleavage located on the hydrazone moiety. The charge delocalization in the anion molecule is reflected in the UV-VIS spectra by the formation of a new, intensively batochromically shifted absorbent band. Hydrazone 1 titration with fluoride ions results in formation of new intensive but hypsochromically shifted absorbent band. By NH-hydrogen substitution for the methyl group is achieved the fact that the UV-VIS titration record is the same as in the above cited works – with hypsochromically shifted absorbent band. The different behavior of the studied hydrazones in the presence of F- ions is illustrated on the scheme 1.
By the NH hydrogen cleavage from the hydrazone, respectively B1-Z or B2-Z anion formation, the intramolecular hydrogen bond is extinguished. The thermodynamic stability of the Z isomer is reduced. Suitable conditions for the thermal Z-E isomerization of anion A2-Z, respectively B2-Z are formed. In the case of hydrazone 1, the N-anion A1-Z transformation to anion B1-Z must be carried out first. Anions C1-E and C2-E are photochemically transformed to Z isomers of this anions and they undergo the thermic Z-E isomerization again.
Audience Take Away:
- The audience can get information about behavior of new bipyridyl-functionalized hydrazones.
- This information can help them to use hydrazones as photoswitches in their research.
- This work can help other researchers to explain behavior of hydrazones in the presence of basic anions.