Efficient access to conjugated 4,4′-bipyridinium oligomers using the Zincke reaction: synthesis, spectroscopic and electrochemical properties

Abstract

The cyclocondensation reaction between rigid, electron-rich aromatic diamines and 1,1'-bis(2,4-dinitrophenyl)-4,4'-bipyridinium (Zincke) salts has been harnessed to produce a series of conjugated oligomers containing up to twelve aromatic/heterocyclic residues. These oligomers exhibit discrete, multiple redox processes accompanied by dramatic changes in electronic absorption spectra.

Thermotropic Liquid-Crystalline and Light-Emitting Properties of Bis(4-aalkoxyphenyl) Viologen Bis(triflimide) Salts

“…The 4-n-alkoxyanilines were prepared in accordance with the modified literature procedure [41]. The bis(4-alkoxyphenyl)-4,4-bipyridinium dichloride (EV1Cl, EV6Cl, EV8Cl, EV10Cl, EV12Cl, EV14Cl, EV16Cl, EV18Cl, and EV20Cl) with alkyl chains of different lengths were synthesized as shown in Scheme 1 [42][43][44]. The synthetic route was based on a two-step procedure involving the aromatic nucleophilic substitution between the 1-chloro-2,4-dinitrobenzene and 4,4-bipyridine to give the Zincke salt and its subsequent ANRORC (anionic ring opening and ring closing) reaction with the corresponding 4-n-alkoxyanilines.…”

Strong ion pair charge transfer interaction of 1,8-naphthalimide–bipyridinium conjugates with basic anions – towards the development of a new type of turn-on fluorescent anion sensors

“…7, the signals of the bipyridinium units and the ethylene bridges disappeared from the spectra, marking the region of the unpaired spin density. 39…”

Prediction of cathodic E 1/2 1 and E 1/2 2 values for viologen-containing conjugated unimers and dimers from calculated p K b values of the aromatic substituents

“…Synthesis of the dimeric series of compounds started with double addition of Zincke salt 5 17 to 3-3'-dimethoxybenzidine (6), which we have shown previously to be a good partner in the Zincke reaction. 9 Addition of 1-chloro-2,4-dinitrobezene to intermediate 7 resulted in the formation of di-Zincke salt 8 which was the common intermediate for the synthesis of the series of di-viologen conjugated systems 2a-h. As can be seen from Table 1, the target di-viologen compounds (2a-2i) were mostly isolated in good yields, although 2c and 2f could not be isolated cleanly under these general reaction conditions.…”

“…7 They are also emerging as key components of functional MOFs including those used for carbon sequestering. 8 Very recently, synthetic and analytical studies of conjugated rod-like viologen containing compounds by our group 9 and by Zhao et al 10 have shown them to exhibit unique redox properties and self-assembly characteristics.…”

“…Herein, we use the optimized Zincke-type 13 reaction conditions reported previously 9,14 in a modular synthesis to produce a library of 18 π-conjugated unimers (1a-i) and dimers (2a-i) containing either one or two viologen residues respectively. The members of each series differ in the substitution patterns on the non-viologen, aromatic rings.…”