Triphenylamine Functionalized Unsymmetrical Quinoxalines

Abstract

A family of unsymmetrical quinoxalines 11-18 of types D-A-π-D and D-A-A'-D' have been designed and synthesized by the Suzuki, Heck, Sonogashira, Ullmann coupling and [2 + 2] cycloadditionÀ retroelectrocyclic ring opening reactions. A systematic study was performed to explore the effect of donor, acceptor and π-linker on the triphenylamine functionalized quinoxalines. The electronic absorption spectra of the ethynyl bridged quinoxaline 14 show red shifted absorption in the high-energy region compared to quinoxaline 13. The quinoxalines 17 and 18 exhibit red shifted absorption in the near-infrared (NIR) region due to the incorporation of strong TCNE/TCNQ acceptor units. The TGA data reveals that triphenylethylene substituted quinoxaline 15 shows higher thermal stability compared to other quinoxalines. The electrochemical data exhibit strong electronic communication in quinoxalines 11-18. The incorporation of TCNE/TCNQ acceptor units results in greater stabilization of LUMO levels and low HOMOÀ LUMO energy gap in 17 and 18 which was supported by computational studies.

Accelerated Intramolecular Charge Transfer in Tetracyanobutadiene- and Expanded Tetracyanobutadiene-Incorporated Asymmetric Triphenylamine–Quinoxaline Push–Pull Conjugates

“…The compounds were purified by column chromatography and fully characterized by 1 H and 13 C NMR and HRMS techniques before physicochemical studies. 42 The effect of introducing TCBD and exTCBD into the D−A system, 1 in benzonitrile, is shown in Figure 2a. The peak maximum of 1 was located at 440 nm.…”

“…Synthesis of compounds 1–3 is reported by us earlier . For triphenylamine-linked quinoxaline, 1 , a multi-step synthetic procedure involving Pd-catalyzed Sonogashira cross-coupling was employed.…”

Phenazine‐based supramolecular photosensitizing assemblies: A “smart” selectivity control on catalytic activity of Pd(II) nanoparticles

“…The reaction between 11‐bromodibenzo[ a , c ]phenazine 1 21 and N , N ‐dipyridylamine (DPA) 2 in DMF at 140°C furnished the target compound N , N ‐di(pyridine‐2‐yl)dibenzo[ a , c ]phenazine‐11‐amine PPA in 30% yield (Scheme 2). [ 22 ] The 1 H NMR spectrum of PPA exhibits four doublets corresponding to protons at 9.33, 9.25, 8.86, and 8.35 ppm (1H , 1H, 2H, 1H), a double doublet corresponding to protons at 8.44 ppm (2H), and two multiplets corresponding to protons at 7.96–7.79, 7.29–7.25 ppm (8H, 4H). The high‐resolution mass spectrum of PPA shows a base peak at 450.1712 corresponding to [M+H] + .…”

“…The reaction between 11-bromodibenzo[a,c]phenazine 1 21 and N,N-dipyridylamine (DPA) 2 in DMF at 140 • C furnished the target compound N,N-di(pyridine-2yl)dibenzo[a,c]phenazine-11-amine PPA in 30% yield (Scheme 2). [22] The After complete characterization of PPA, photophysical behaviour of PPA was examined by using UV-vis and fluorescence spectroscopy. The THF solution of PPA exhibits absorption bands at 314 nm due to π-π* transitions of phenazine moiety and at 435 nm due to intramolecular charge transfer state.…”

Phenothiazine and phenothiazine-5,5-dioxide-based push–pull derivatives: synthesis, photophysical, electrochemical and computational studies

“…The longer wavelength transition is associated with intramolecular charge transfer (ICT) from the donor phenothiazine to acceptor TCBD unit. 6,50,52,53 Similarly, the cyclohexa-2,5diene-1,4-diylidene-expanded TCBD substituted PTZ 3 and phenothiazine-5,5-dioxide functionalized cyclohexa-2,5-diene-1,4-diylidene-expanded TCBD substituted PTZ 6 exhibit two strong absorption bands at 400 nm, 675 nm and 373 nm, 535 nm, respectively. The TCBD and cyclohexa-2,5-diene-1,4diylidene-expanded TCBD functionalized PTZ 2 and 3 exhibit absorption bands at a higher wavelength region than PTZ 5 and 6, reflecting the weak donor ability of the phenothiazine-5,5dioxide unit.…”