sbornik_s_2011.pdf

XI. Workshop of Physical Chemists and Electrochemists´11 Brno
Tab. 1: Overview of investigated 4-anilinoquinazolines.
A B C D
-Br
-Br
-Cl
2. EXPERIMENT
EPR in situ photochemical experiments were performed upon UVA irradiation of 4anilinoquinazolines
in dimethylsulfoxide (DMSO) applying an EPR spin trapping
technique to observe short living radical intermediates. 5,5-Dimethyl-1-pyrroline N-oxide
(DMPO) and 5-ethoxy carbonyl-5-methyl-1-pyrroline N-oxide (EMPO) were used as
spin trapping agents. The photoinduced production of singlet oxygen during the
excitation of 4-anilinoquinazolines was followed in acetonitrile (ACN) solutions in the
presence of 4-hydroxy-2,2,6,6-piperidine (TMP). The solutions of 4-anilinoquinazolines
containing spin traps or TMP were mixed directly before the EPR measurements, then
carefully saturated with air and immediately transferred to a small quartz flat cell
optimized for the TE102 cavity of the EPR spectrometer EMX (Bruker, Germany). The
samples were irradiated at 295 K directly in the EPR resonator, and the EPR spectra
recorded in situ during continuous photoexcitation.
3. RESULTS AND DISCUSSION
The generation of paramagnetic species upon photoexcitation of studied
anilinoquinazoline derivatives (Tab. 1) was investigated in DMSO solutions by in situ EPR
spin trapping technique. Applying DMPO as a spin trapping agent dominating
photoinduced twelve line EPR signal was observed. This signal was attributed to the
superoxide radical anion spin adduct ( DMPO-O2 – ), considering good agreement of spin
Hamiltonian parameters, obtained from simulation analysis, with the hyperfine coupling
constants of DMPO-O2 – in DMSO. In addition to the major spin adduct, DMPO-OCH3
- 43 -
-H -H
-
NO
2
-H
-H
-
CH
3
N-phenyl-6bromo-2morpholinoquinazoline-4amine
(QA1)
N-(2nitrophenyl)-6bromo-2morpholinoquinazoline-4amine
(QA2)
N-(4methylphenyl)-6chloro-2-phenylquinazoline-4amine
(QA3)