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Title: Azonium-ammonium tautomerism and inclusion complexation of 4-amino-2′, 3-dimethylazobenzene
Authors: Prabhu, A Antony Muthu
Venkatesh, G
Sankaranarayanan, R K
Siva, S
Rajendiran, N
Keywords: Spectral studies;Tautomerism;Inclusion compounds;Azo compounds;Azobenzenes;Aminoazobenzenes;Cyclodextrins
Issue Date: Apr-2010
Publisher: CSIR
Abstract: The spectral characteristics of 4-amino-2′,3-dimethylazobenzene (GBC), 4-aminoazobenzene (AAB) and azobenzene (AB) have been studied in various solvents, varying hydrogen ion concentrations and in -cyclodextrin (-CD). The inclusion complexes of GBC, AAB and AB with -CD have been analysed by UV-visible, fluorometry, FT-IR, 1H NMR, SEM and Cache-DFT methods. The solvent study shows that the azo form is present only in GBC and AAB molecules. No significant spectral difference is observed in GBC indicating that the presence of two methyl groups does not effectively change the spectral behaviour as compared to that of AAB. In acid solutions, unusual red shift is observed in the monocation suggesting that the azonium-ammonium tautomer is present in both molecules. The absorption maximum at ~500 nm, is due to the azonium cation while that at ~320 nm originates from the ammonium cation. In -CD solutions, the increase in the fluorescence intensity and large bathochromic shift in S1 state indicates that both GBC and AAB form 2:2 inclusion complex, whereas AB forms 1:1 inclusion complex. Also, head-to-head dimer is formed in both the aminoazobenzene compounds.
Page(s): 407-417
Appears in Collections:IJC-A Vol.49A(04) [April 2010]

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