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Pregled bibliografske jedinice broj: 756931

Časopis

Autori: Basarić, Nikola; Thomas, S. Suma; Blažek Bregović, Vesna; Cindro, Nikola; Bohne, Cornelia
Naslov: Phototautomerization in pyrrolylphenylpyridine terphenyl systems
Izvornik: Journal of organic chemistry (0022-3263) 80 (2015), 9; 4430-4442
Vrsta rada: članak
Ključne riječi: excited state proton transfer (ESPT); pyridine; pyrrole; laser flash photolysis; inclusion complexes; cucurbit[7]uril
Sažetak:
[4-(2-Pyrrolyl)phenyl]pyridines 2-4 were synthesized and their photophysical properties and reactivity in phototautomerization reactions investigated by fluorescence spectroscopy and laser flash photolysis (LFP). The pKa for the protonation of the pyridine nitrogen in 2-4 was determined by UV-vis and fluorescence titration (pKa = 5.5 for 4). On excitation in polar protic solvents 2-4 populate charge transfer (CT) states leading to an enhanced basicity of the pyridine (pKa*≈ 12) and enhanced acidity of pyrrole (pKa*≈ 8-9) enabling excited state proton transfer (ESPT). ESPT gives rise to phototautomers and significantly quenches the fluorescence of 2-4. Phototautomers 2-T and 4-T were detected by LFP with strong transient absorption maxima at 390 nm. Phototautomers 2-T and 4-T decayed by competing uni- and bimolecular reactions. However, at pH 11 the decay of 4-T followed exponential kinetics with a rate constant of 4.2 ×106 s-1. The pyridinium salt 4H+ forms a stable complex with cucurbit[7]uril (CB[7]) with 1:1 stoichiometry (β11 = (1.0 ± 0.2) × 105 M-1, [Na+] = 39 mM). Complexation to CB[7] increased the pKa for 4H+ (pKa =6.9) and changed its photochemical reactivity. Homolytic cleavage of the pyrrole NH leads to the formation of an N-radical because of the decreased acidity of the pyrrole in the inclusion complex.
Projekt / tema: 02.05/25, NSERC
Izvorni jezik: ENG
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bazama podataka:
Current Contents Connect (CCC)
Scopus
SCI-EXP, SSCI i/ili A&HCI
Science Citation Index Expanded (SCI-EXP) (sastavni dio Web of Science Core Collectiona)
Kategorija: Znanstveni
Znanstvena područja:
Kemija
URL Internet adrese: http://pubs.acs.org/doi/abs/10.1021/acs.joc.5b00275
Broj citata:
Altmetric:
DOI: 10.1021/acs.joc.5b00275
URL cjelovitog teksta:
Google Scholar: Phototautomerization in pyrrolylphenylpyridine terphenyl systems
Upisao u CROSBI: Enidija Lukša (Enidija.Luksa@irb.hr), 31. Ožu. 2015. u 10:14 sati



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