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Reductive photocyanation of 1,10-phenanthroline in aqueous media
- Source :
- Journal of Photochemistry and Photobiology A: Chemistry. 174:149-155
- Publication Year :
- 2005
- Publisher :
- Elsevier BV, 2005.
-
Abstract
- Reductive photocyanation of 1,10-phenanthroline (phen) took place in an aqueous NaCN solution, yielding 5-cyano-5,6-dihydro-1,10-phenanthroline (Hphen-CN) with the reaction and quantum yields of 5–50% and 10 −3 to 10 −4 , respectively. The photoreaction in the presence of Mg 2+ (aerated conditions) improved the reaction quantum yield by a factor of ∼7 as compared to that without Mg 2+ , through coordination of Mg 2+ with phen: phen:Mg 2+ complex. The fluorescence lifetimes of phen and the phen:Mg 2+ complex were ∼3 and ∼10 ns, respectively, and the fluorescence of the phen:Mg 2+ complex was shown to be quenched more efficiently by a cyanide ion as compared to that of phen itself. The fluorescence quenching percents of phen by NaCN in the absence and presence of Mg 2+ were 3 and 24%, respectively, and the eight-fold increase in the quenching percent in the presence of Mg 2+ gave rise to the approximately seven-fold increase in the reaction quantum yield. On the basis of such results, we proposed that the present photocyanation reaction proceeded via electron transfer from a cyanide ion to the excited singlet-states of phen and/or the phen:Mg 2+ complex as the primary step: anion radical (S N-R 1Ar*) mechanism. The characteristic features of the present photoreaction of phen in the presence of Mg 2+ and the possible reaction mechanisms are discussed in detail.
Details
- ISSN :
- 10106030
- Volume :
- 174
- Database :
- OpenAIRE
- Journal :
- Journal of Photochemistry and Photobiology A: Chemistry
- Accession number :
- edsair.doi...........62e33e1198c187b720170c937aef0617