ISSN:
0009-2940
Keywords:
Chromophores, combined
;
Azobenzene
;
(Phenyl)methylium
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Phenylazo-Substituted Triphenylmethylium SystemsTriphenylmethanols (or their ethers) bearing phenylazo groups react with trifluoroacetic acid to give deeply colored solutions of the tritylium ions 7+ - 9+, (RC6H4N = N-C6H4)n+ C(C6H5)3-n (R = H, Me, C1, NOz, MeO, H2N, Me2N), whose long wavelengths VIS absorptions and lowfield 1H- NMR signals are consistent with the existence of through- conjugated n-electron systems. After addition of trifluorometh- anesulfonic acid significant hypsochromic shifts of the VIS bands as well as additional proton deshieldings in the 1HNMR spectrum are observed, which are in accordance with the formation of proximally azo-protonated phenylazotrity- lium ions 7+·H+, 8+·2H+, and 9+·3H+, (RC6H4N=NH- C6H4)nC(C6H53 - n. Fully analogous acid-strength-dependent ionisation/protonation reactions result for the overall p-sub- stituted ions 17+, 18+, (RC6H4N= NC6H4)C(C6H4R)2 (R, R' = Me, MeO, Me2N), as well as for the azobistritylium system,102+ (C6H5)2CC6H4N=NC6H4(C6H52, and its azoxy deriv- ative 112+. The linearly extended bis- and trisazo systems 19+, 22+, MeC6H4N = N(C6H4N = N)1,2C6H4C(C6H5)2 and the (ph+e-ny1azo)styryl system 20+, MeC6 H4N = NC6H4CH = CHC6H4C- (C6H5), in trifluoroacetic acid do not show any significant color changes relativ to the corresponding monofunctional parent types. In trifluoromethanesulfonic acid, however, compounds 19+, 22+ exhibit the usual bathochromic shifts of the longest wavelength VIS absorptions accompanying the increasing protonation of the polyazo systems. In the case of the tritylium ions containing azomethine bridges, 24+, only for the methoxy derivative 24b+ indications for the existence of the conjuga- tively extended tritylium system (MeOC6H4N = CHC6H,)C- (C6H5)2 are found. The amide derivatives 26+ - 29+, on the other hand, present no clues for the existence of through-con- jugated systems of the kind ArC(OH)=NC6H4Ckz and ArN = C(OH)C6H4CAr2, respectively.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19901231120
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