title: Synthesis, photophysical, photochemical, and computational studies of coumarin-labeled nicotinamide derivatives.
abstract: The syntheses and photophysical/photochemical properties of two amide-tethered coumarin-labeled nicotinamides are described. Photochemical studies of 6-bromo-7-hydroxycoumarin-4-ylmethylnicotinamide (BHC-nicotinamide) revealed an unexpected solvent effect. This result is rationalized by computational studies of the different protonation states using TD-DFT with the M06L/6-311+G** method with implicit and explicit solvation models. Molecular orbital energies responsible for the λ(max) excitation show that the functionalization of the coumarin ring results in a strong red-shift from 330 to 370 nm when the pH of solution is increased from 3.06 to 8.07. From this MO analysis, a model for solvent interactions has been proposed. The BHC-nicotinamide proved to be photochemically stable, which is also interpreted in terms of NBO calculations. The results provide a set of principles for the rational design of either photostable labeling reagents or photolabile cage compounds.
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, Indiana 46556, USA.
authors.forename: Pauline
authors.initials: P
authors.lastname: Bourbon
authors.forename: Qian
authors.initials: Q
authors.lastname: Peng
authors.forename: Guillermo
authors.initials: G
authors.lastname: Ferraudi
authors.forename: Cynthia
authors.initials: C
authors.lastname: Stauffacher
authors.forename: Olaf
authors.initials: O
authors.lastname: Wiest
authors.forename: Paul
authors.initials: P
authors.lastname: Helquist
mesh_terms: D003374:Coumarins / Q000138:chemical synthesis* / Q000737:chemistry*; D018360:Crystallography, X-Ray; D015394:Molecular Structure; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry*; D010777:Photochemistry; D011789:Quantum Theory
chemical_list: C574110:6-bromo-7-hydroxycoumarin-4-ylmethylnicotinamide; D003374:Coumarins; D009536:Niacinamide; C030123:coumarin