TY - JOUR
T1 - Superoxide radical anion adduct of 5,5-dimethyl-1-Pyrroline N-oxide. 4. Conformational effects on the EPR hyperfine splitting constants
AU - Villamena, Frederick A.
AU - Liu, Yangping
AU - Zweier, Jay L.
PY - 2008/12/11
Y1 - 2008/12/11
N2 - Spin trapping has been commonly employed in the detection of superoxide radical anion in chemical and biological systems; hence, accurate interpretation of the hyperfine splitting constants (hfsc's) arising from the O 2•- adducts (also referred to as hydroperoxyl (HO2•) radical adducts) of various nitrones is important. In this work, the nature of the relevant hfsc's was investigated by examining the effect of conformational changes in the hydroperoxyl moiety of the O2•- adducts of 5,5-dimethyl-l-pyrroline N-oxide (DMPO), 5-ethoxycarbonyl-5-methyl-1-pyrroline N-oxide (EMPO), 5-diethoxyphosphoryl-5-methyl-l-pyrroline N-oxide (DEPMPO), 5-carbamoyl-5- methyl-1-pyrroline N-oxide (AMPO), and 7-oxa-l-azaspiro[4.4]non-1-en-6-one N-oxide, (CPCOMPO) on the magnitude of aN, aβ-H, and aγ-H. Conformational change around the substituents and their effect on the hfsc's were also explored. Results indicate that a β-H is most sensitive to conformational changes of the hydroperoxyl and substituent groups relative to hfsc's of other nuclei. The orbital overlap between the C-H σ-orbital and the SOMO of the nitroxyl nitrogen plays a crucial factor in determining the magnitude of the a β-H. The hfsc values for the O2•- adducts were predicted with high accuracy by using a low-cost computational method at the PCM(water)/BHandHLYP/EPR-III//B3LYP/6-31G* level of theory without taking into account the explicit water interaction.
AB - Spin trapping has been commonly employed in the detection of superoxide radical anion in chemical and biological systems; hence, accurate interpretation of the hyperfine splitting constants (hfsc's) arising from the O 2•- adducts (also referred to as hydroperoxyl (HO2•) radical adducts) of various nitrones is important. In this work, the nature of the relevant hfsc's was investigated by examining the effect of conformational changes in the hydroperoxyl moiety of the O2•- adducts of 5,5-dimethyl-l-pyrroline N-oxide (DMPO), 5-ethoxycarbonyl-5-methyl-1-pyrroline N-oxide (EMPO), 5-diethoxyphosphoryl-5-methyl-l-pyrroline N-oxide (DEPMPO), 5-carbamoyl-5- methyl-1-pyrroline N-oxide (AMPO), and 7-oxa-l-azaspiro[4.4]non-1-en-6-one N-oxide, (CPCOMPO) on the magnitude of aN, aβ-H, and aγ-H. Conformational change around the substituents and their effect on the hfsc's were also explored. Results indicate that a β-H is most sensitive to conformational changes of the hydroperoxyl and substituent groups relative to hfsc's of other nuclei. The orbital overlap between the C-H σ-orbital and the SOMO of the nitroxyl nitrogen plays a crucial factor in determining the magnitude of the a β-H. The hfsc values for the O2•- adducts were predicted with high accuracy by using a low-cost computational method at the PCM(water)/BHandHLYP/EPR-III//B3LYP/6-31G* level of theory without taking into account the explicit water interaction.
UR - http://www.scopus.com/inward/record.url?scp=58149218363&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=58149218363&partnerID=8YFLogxK
U2 - 10.1021/jp8070579
DO - 10.1021/jp8070579
M3 - Article
C2 - 19012384
AN - SCOPUS:58149218363
SN - 1089-5639
VL - 112
SP - 12607
EP - 12615
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 49
ER -