scholarly journals Laser Induced Fluorescence of 4-N,N-Dimethylaminobenzonitrile (DMABN) and Related Compounds

1988 ◽  
Vol 9 (4-6) ◽  
pp. 317-337 ◽  
Author(s):  
Anita C. Jones ◽  
David Phillips
Keyword(s):  
Polar Solvent ◽  
Cyano Group ◽  
Solvent Molecule ◽  
Laser Induced Fluorescence ◽  
Solvent Mixtures ◽  
Decay Kinetics ◽  
Dimethylamino Group ◽  
Fluorescence Studies ◽  
Decay Times ◽  
Related Compounds

The role of polar solvent in determining the photophysics of normal (b*) and anomalous (a*) fluorescence from 4-N,N-dimethylaminobenzonitrile (DMABN) and related compounds has been investigated by means of picosecond time-resolved fluorescence studies in non-polar/polar solvent mixtures, and by electronic spectroscopic studies on complexes of 1:1 stoichiometry prepared by nozzle expansion. The solution phase results indicate clearly that a DMABN-polar solvent complex is formed initially in either ground or excited state, and that this rearranges to a geometry from which the b* to a* state transition can occur. Specific solvent-solute interactions are clearly indicated by this work, and these lead to the necessity of modelling b* state decay kinetics in solution by a distribution of decay times.Laser induced fluorescence studies of jet-cooled solvated complexes of DMABN and the related molecule 4-aminobenzonitrile (4-ABN) provide evidence for the existence of 1:1 complexes involving interaction of a protic solvent molecule with either the cyano group or the amino group. In the case of 4-ABN both types of complex are fluorescent whereas in the case of DMABN, those complexes involving interaction with the dimethylamino group appear to be non-emissive. This behaviour may be due to formation of DMABN-solvent exciplex which constitutes a dark state under jet-cooled conditions. Neither the DMABN bare molecule nor the observed 1:1 solvated complexes exhibit a* emission in the jet.

Some piperazino analogues of methadone and related ketones: a novel conversion of an N-carbethoxy to a triethylmethyl group

1969 ◽  
Vol 47 (13) ◽  
pp. 2413-2419
Author(s):  
J. R. Dimmock ◽  
N. J. Harper ◽  
R. Islam ◽  
A. F. Casy
Keyword(s):  
Cyano Group ◽  
Magnesium Bromide ◽  
Dimethylamino Group ◽  
Ethyl Magnesium Bromide ◽  
Derivatives Of ◽  
Related Compounds

A number of derivatives of methadone and related compounds have been prepared, where the dimethylamino group has been replaced by a 4-substituted piperazino function. The preparation of these compounds involved the reaction of N-ω-cyanoalkyl-N′-carbethoxy piperazines with ethyl magnesium bromide, and various products were obtained. These included replacement of the N′-carbethoxy group by a triethylmethyl function and cleavage of the carbethoxy group. In some cases the ω-cyano group reacted to give the corresponding ketone. Reactions of 1-benzyl-4-carbethoxy piperazine with ethyl magnesium bromide and phenyl magnesium bromide gave no evidence for the formation of the triethylmethyl group. However, cleavage of the carbethoxy group occurred and there was evidence for the formation of the corresponding amide.

The tryptophan fluorescence lifetime puzzle. A study of decay times in aqueous solution as a function of pH and buffer composition

1981 ◽  
Vol 59 (7) ◽  
pp. 1037-1044 ◽  
Author(s):  
Eva Gudgin ◽  
Ricardo Lopez-Delgado ◽  
William R. Ware
Keyword(s):  
Tryptophan Fluorescence ◽  
Fluorescence Decay ◽  
Low Ph ◽  
Decay Kinetics ◽  
Decay Component ◽  
Diffusion Controlled ◽  
Double Exponential ◽  
Decay Times ◽  
Fluorescence Decay Kinetics ◽  
Buffer Composition

Tryptophan fluorescence decay kinetics have been systematically investigated in aqueous solutions as a function of pH as well as in a variety of buffer solutions. Below pH 7.0, the decay appears to be double exponential with a subnanosecond component confirming the previous findings of Rayner and Szabo (3). In the low pH region, where the proton concentration becomes kinetically significant, tryptophan fluorescence is collisionally quenched by [H+] with diffusion controlled rate and no experimental evidence is found regarding the appearance at low pH of a new tryptophan molecular species, namely the cationic form. At pH ≥ 7.0, the decay becomes triple-exponential with the appearance of a long component whose contribution to the total emission intensity increases rapidly with increasing pH at the expense of the other two. Lifetimes and relative intensities of each decay component depend in a complex way on pH and on the buffer chemical composition.

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