Ethynyl‐Bridged Bis‐quinolinium Dyes: Studies of the Dependence of Different Types of Conjugation on Spectroscopic Properties

Abstract Dicationic bis‐quinolinium salts possessing different types of conjugation are presented in which the hetareniums separated by acetylenic or 1,4‐diethynylbenzene spacers. Cross‐conjugation is induced interconnections via 3‐positions heteroareniums, and realized 2,2/2,4/4,4‐interconnections. We also synthesized mixed cross‐conjugated/conjugated 2,3/4,3‐interconnected species. The determine charge distribution according to rules resonance translate into characteristic 13 C NMR as well UV‐Vis‐spectroscopic properties, LUMO geometries, chemical properties. found that triple bond's frequencies sensitive spectroscopic indicators for type conjugation. Combining cross‐conjugated conjugated structure elements dicationic dyes bonds without additional benzene spacer results considerable bathochromic shifts UV‐Vis absorption maxima [Δλ max ≈100 nm]. A transfer was calculated from HOMO partial structure.