Acylhydrazone Switches: E/Z Stability Reversed by Introduction of Hydrogen Bonds. Issue 48 (21st November 2018)

• Record Type: Journal Article
• Authors: Lu, Chaocao; Htan, Bu; Ma, Chunmiao; Liao, Rong‐Zhen; Gan, Quan
• Is Part Of: European journal of organic chemistry. Issue 48(2018)
• Page Start: 7046
• Page End: 7050
• Publication Date: 2018-11-21
• Subjects: Hydrogen bonds -- Molecular switches -- Isomerization -- Supramolecular chemistry -- Crystallography; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201801466
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract : We report a series of acylhydrazone‐based switches, of which double bond rotation can be stimulated by a pH response. The switches prefer Z rather than E configuration in the ground state because of the intramolecular hydrogen bonding, which was analyzed both thermodynamically and kinetically. Solvation studies show a linear relationship between the isomerization energy in Z/E states (Δ G E/Z o ) of the switches and the hydrogen bond basicity scales ( β and DN ) of the solvent. This solvent effect was also found to be relative to the skeleton of compound, the less shield of hydrogen bond domain the more sensitivity to the solvent environment. By introducing multiple intramolecular hydrogen bonds, the Z isomer completely predominates for compound 4, offering an advantage over a full E/Z isomerization switching. Abstract : Intramolecular hydrogen bonds prefer acylhydrazone switches adopting Z rather than E configuration in the ground state. This unusual stability can raise energy difference of E/Z isomers, and thus provides access to a complete and efficient isomerization switching cycle by a pH response.