Dendritic Groups Substituted Kekulé‐Benzene‐Bridged Bis(triarylamine) Mixed‐valence Systems: Syntheses, Characterization and Electronic Coupling Properties. Issue 13 (6th April 2020)

• Record Type: Journal Article
• Authors: Ou, Ya‐Ping; Wang, Aihui; Zhang, Fuxing; Hu, Fang
• Is Part Of: ChemistrySelect. Volume 5:Issue 13(2020)
• Page Start: 4111
• Page End: 4117
• Publication Date: 2020-04-06
• Subjects: Insulated molecular wires -- Triarylamine -- Dendritic protected groups -- NIR absorptions -- electronic coupling; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.202000158
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: Alkoxy‐substituted phenyl‐bridged triarylamine compounds 1 –3 of three different sizes were synthesized and characterized by nuclear magnetic resonance, elemental analysis, and X‐ray single diffraction. Their electronic coupling properties were investigated by electrochemistry, UV‐vis‐near‐infrared (NIR) spectroscopy, and density functional theory calculations. Electrochemistry experiment results with small potential difference reveal that unresolved electronic coupling occurred between two NAr2 termini. Observable electronic coupling of mixed‐valence 1 + –3 + were exhibited by NIR absorptions, and electronic coupling parameter H ab was calculated by the Hush theory formula from experimental characteristic intervalence charge‐transfer transitions. The results revealed that the electron coupling of 1 + –3 + gradually increased with the alkoxy size of the substituents (from methoxy to dendritic groups) attached to the central phenyl bridge. These findings are supported by the increasing gradient trend of spin density contributions of bridge linkers (terphenyl) (1 + : 23 %; 2 + : 30 %; 3 + : 38 %) and further prove that introducing protected groups, such as large dendritic groups in bridge cores, can effectively enlarge electronic coupling. Abstract : We described the syntheses and characterization of three alkoxy‐substituted 1, 4‐phenyl bridged TPA derivatives 1 –3, and investigated their electronic coupling properties by electrochemistry, UV‐vis‐NIR spectral and theoretical calculations. NIR spectroscopy analysis and spin density distribution calculations from mixed‐valence species revealed electron coupling of 1 + –3 + gradually increased with the alkoxy size of the substituents (from methoxy to dendritic groups) attached to the central phenyl bridge. The results concluded that introducing large alkoxy chain can effectively enlarge electronic coupling.