137929-28-3Relevant academic research and scientific papers
Supercritical fluid tuning of reactions rates: The cis-trans isomerization of 4-4′-disubstituted azobenzenes
Dillow, Angela K.,Brown, James S.,Liotta, Charles L.,Eckert, Charles A.
, p. 7609 - 7617 (1998)
Remarkable tuning of reaction rates has been achieved for the isomerization of several dye molecules in supercritical fluid solvents using both small pressure changes and small additions of cosolvents. Rates of the thermal cis-trans relaxation were measured spectroscopically following irradiation for three dyes in supercritical carbon dioxide and ethane, pure and with several polar and protic cosolvents. The results are explained in terms of local density and composition enhancements, as well as by a change of mechanism due to strong hydrogen bonding. This study demonstrates the versatility of supercritical fluid solvents both to examine reaction mechanisms and as a means to tune rates.
Studies on UV/VIS Absorption Spectra of Azo Dyes. XV. An Analysis of the Absorption Spectra of 4,4'-Diaminoazobenzenes
Haessner, C.,Mustroph, H.
, p. 113 - 119 (2007/10/02)
In the visible absorption spectrum 4,4'-bis-diethylaminoazobenzene shows two absorption maxima (λmax = 426 nm and λmax = 477 nm) with high intensity.Quantum chemical calculations and examinations by peak separation of six 4-substituted azobenzenes and six 4'-substituted 4-diethylaminoazobenzenes (1a-k) indicate that the longest wavelenght band is due to a n-?* transition and the other band is due to a ?-?*-transition.This is verified using an inrement system for ?-?* absorption maxima.A linear relation is found between intensity ratios of the two bands and the HAMMETT-?-constants of the substituents.With increasing electron releasing tendency of the substituents the absorption intensity of the n-?*-band increases.
