title: Femtosecond studies of charge-transfer mediated proton transfer in 2-butylamino-6-methyl-4-nitropyridine N-oxide.
abstract: We have unraveled the effects of an amino substituent in the ortho position on the excited-state dynamics of 4-nitropyridine N-oxide by studying the picosecond fluorescence kinetics and femtosecond transient absorption of a newly synthesized compound, 2-butylamino-6-methyl-4-nitropyridine N-oxide, and by quantum chemical calculations. Similar to the parent compound, the S(1) state of the target molecule has significant charge-transfer character and shows a large (approximately 8000 cm(-1)) static Stokes shift in acetonitrile. Analysis of the experimental and the theoretical results leads, however, to a new scenario in which this intramolecular charge transfer triggers in polar, aprotic solvents an ultrafast (around 100 fs) intramolecular proton transfer between the amino and the N-O group. The electronically excited N-OH tautomer is subsequently subject to solvent relaxation and decays with a lifetime of approximately 150 ps to the ground state.
authors.affiliation: Van't Hoff Institute for Molecular Sciences, University of Amsterdam, The Netherlands.
authors.forename: Benedek
authors.initials: B
authors.lastname: Poór
authors.forename: Natalia
authors.initials: N
authors.lastname: Michniewicz
authors.forename: Mihaly
authors.initials: M
authors.lastname: Kallay
authors.forename: Wybren Jan
authors.initials: WJ
authors.lastname: Buma
authors.forename: Miklós
authors.initials: M
authors.lastname: Kubinyi
authors.forename: Anna
authors.initials: A
authors.lastname: Szemik-Hojniak
authors.forename: Irena
authors.initials: I
authors.lastname: Deperasiñska
authors.forename: Aniela
authors.initials: A
authors.lastname: Puszko
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
mesh_terms: D003198:Computer Simulation; D008968:Molecular Conformation; D015394:Molecular Structure; D011522:Protons; D011725:Pyridines / Q000737:chemistry*; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry; D013997:Time Factors
chemical_list: C521932:2-butylamino-6-methyl-4-nitropyridine N-oxide; D011522:Protons; D011725:Pyridines; D012997:Solvents