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Fluorescence emission properties of 8-azaisoguanine and its N-methyl derivatives: Ground- and excited-state tautomerism ☆

Paper ID Volume ID Publish Year Pages File Format Full-Text
28314 44069 2012 7 PDF Available
Title
Fluorescence emission properties of 8-azaisoguanine and its N-methyl derivatives: Ground- and excited-state tautomerism ☆
Abstract

Fluorescence emission properties of 8-aza-isoguanine (z8isoGua) and some of its N-methyl derivatives are described. Two fluorescence bands, with maxima at ∼360 and ∼420 nm and distinct decay times, are observed in 8-azaisoguanine and its N(8)-methyl derivative, in aqueous medium at pH 4–5 and 5–9, respectively, where both compounds adopt neutral forms in their ground states. The long-wavelength band is not observed in non-aqueous solvents, but is enhanced at least twofold in the presence of 0.5–1 M buffer ions (phosphate or acetate), and is also sensitive to deuterium isotope exchange. The N(3)-methyl-and N(3),N(8)-dimethyl derivatives exhibit single-band fluorescence, centered at ∼370 nm, indicating that the 420 nm band observed in z8isoGua and N(8)-methyl-z8isoGua should be ascribed to the transfer of the N(3)–H proton in the excited state of the molecules to the N(1) nitrogen. A similar phenomenon is observed for the cationic forms of z8isoGua and N(8)-methyl-z8isoGua, which in aqueous medium, exhibit fluorescence centered at ∼420 nm. This type of microenvironment-sensitive emission is useful for biochemical applications.

► 8-azaisoguanine and its N(8)-methyl-derivative exhibit dual emission in aqueous medium. ► Dual emission is absent in N(3)-methyl derivatives. ► The dual emission shows marked solvent, isotope and buffer concentration effects. ► Proposed interpretation: prototropic N(1)H ↔ N(3)H phototautomerism.

Keywords
IsoGua, isoguanine; z8isoGua, 8-aza-isoguanine (IUPAC name: 7-amino-3H-1,2,3-triazolo[4,5-d]pyrimidine-5(6H)-one)8-Azapurines; 8-Azaisoguanine; Fluorescence; Tautomerism; Excited-state proton transfer; Salt and isotope effects
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Fluorescence emission properties of 8-azaisoguanine and its N-methyl derivatives: Ground- and excited-state tautomerism ☆
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 237, 1 June 2012, Pages 64–70
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us