Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR
Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced fo...
Ausführliche Beschreibung
Gespeichert in:
| Autor*in: |
|---|
| Format: |
E-Artikel |
|---|---|
| Sprache: |
Englisch |
| Erschienen: |
1997 |
|---|
| Umfang: |
14 |
|---|
| Reproduktion: |
Springer Online Journal Archives 1860-2002 |
|---|---|
| Übergeordnetes Werk: |
in: JBIC - 1996, 2(1997) vom: Feb., Seite 242-255 |
| Übergeordnetes Werk: |
volume:2 ; year:1997 ; month:02 ; pages:242-255 ; extent:14 |
| Links: |
|---|
| Katalog-ID: |
NLEJ206167822 |
|---|
| LEADER | 01000caa a22002652 4500 | ||
|---|---|---|---|
| 001 | NLEJ206167822 | ||
| 003 | DE-627 | ||
| 005 | 20210706193940.0 | ||
| 007 | cr uuu---uuuuu | ||
| 008 | 070528s1997 xx |||||o 00| ||eng c | ||
| 035 | |a (DE-627)NLEJ206167822 | ||
| 040 | |a DE-627 |b ger |c DE-627 |e rakwb | ||
| 041 | |a eng | ||
| 245 | 1 | 0 | |a Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR |
| 264 | 1 | |c 1997 | |
| 300 | |a 14 | ||
| 336 | |a nicht spezifiziert |b zzz |2 rdacontent | ||
| 337 | |a nicht spezifiziert |b z |2 rdamedia | ||
| 338 | |a nicht spezifiziert |b zu |2 rdacarrier | ||
| 520 | |a Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge. | ||
| 533 | |f Springer Online Journal Archives 1860-2002 | ||
| 700 | 1 | |a Davydov, R. M. |4 oth | |
| 700 | 1 | |a Ménage, Stéphane |4 oth | |
| 700 | 1 | |a Fontecave, M. |4 oth | |
| 700 | 1 | |a Gräslund, Astrid |4 oth | |
| 700 | 1 | |a Ehrenberg, A. |4 oth | |
| 773 | 0 | 8 | |i in |t JBIC |d 1996 |g 2(1997) vom: Feb., Seite 242-255 |w (DE-627)NLEJ188989765 |w (DE-600)1464026-0 |x 1432-1327 |7 nnns |
| 773 | 1 | 8 | |g volume:2 |g year:1997 |g month:02 |g pages:242-255 |g extent:14 |
| 856 | 4 | 0 | |u http://dx.doi.org/10.1007/s007750050130 |
| 912 | |a GBV_USEFLAG_U | ||
| 912 | |a ZDB-1-SOJ | ||
| 912 | |a GBV_NL_ARTICLE | ||
| 951 | |a AR | ||
| 952 | |d 2 |j 1997 |c 2 |h 242-255 |g 14 | ||
| matchkey_str |
article:14321327:1997----::ievlnoordediocmlxsrdcdyailtceu |
|---|---|
| hierarchy_sort_str |
1997 |
| publishDate |
1997 |
| allfields |
(DE-627)NLEJ206167822 DE-627 ger DE-627 rakwb eng Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR 1997 14 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge. Springer Online Journal Archives 1860-2002 Davydov, R. M. oth Ménage, Stéphane oth Fontecave, M. oth Gräslund, Astrid oth Ehrenberg, A. oth in JBIC 1996 2(1997) vom: Feb., Seite 242-255 (DE-627)NLEJ188989765 (DE-600)1464026-0 1432-1327 nnns volume:2 year:1997 month:02 pages:242-255 extent:14 http://dx.doi.org/10.1007/s007750050130 GBV_USEFLAG_U ZDB-1-SOJ GBV_NL_ARTICLE AR 2 1997 2 242-255 14 |
| spelling |
(DE-627)NLEJ206167822 DE-627 ger DE-627 rakwb eng Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR 1997 14 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge. Springer Online Journal Archives 1860-2002 Davydov, R. M. oth Ménage, Stéphane oth Fontecave, M. oth Gräslund, Astrid oth Ehrenberg, A. oth in JBIC 1996 2(1997) vom: Feb., Seite 242-255 (DE-627)NLEJ188989765 (DE-600)1464026-0 1432-1327 nnns volume:2 year:1997 month:02 pages:242-255 extent:14 http://dx.doi.org/10.1007/s007750050130 GBV_USEFLAG_U ZDB-1-SOJ GBV_NL_ARTICLE AR 2 1997 2 242-255 14 |
| allfields_unstemmed |
(DE-627)NLEJ206167822 DE-627 ger DE-627 rakwb eng Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR 1997 14 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge. Springer Online Journal Archives 1860-2002 Davydov, R. M. oth Ménage, Stéphane oth Fontecave, M. oth Gräslund, Astrid oth Ehrenberg, A. oth in JBIC 1996 2(1997) vom: Feb., Seite 242-255 (DE-627)NLEJ188989765 (DE-600)1464026-0 1432-1327 nnns volume:2 year:1997 month:02 pages:242-255 extent:14 http://dx.doi.org/10.1007/s007750050130 GBV_USEFLAG_U ZDB-1-SOJ GBV_NL_ARTICLE AR 2 1997 2 242-255 14 |
| allfieldsGer |
(DE-627)NLEJ206167822 DE-627 ger DE-627 rakwb eng Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR 1997 14 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge. Springer Online Journal Archives 1860-2002 Davydov, R. M. oth Ménage, Stéphane oth Fontecave, M. oth Gräslund, Astrid oth Ehrenberg, A. oth in JBIC 1996 2(1997) vom: Feb., Seite 242-255 (DE-627)NLEJ188989765 (DE-600)1464026-0 1432-1327 nnns volume:2 year:1997 month:02 pages:242-255 extent:14 http://dx.doi.org/10.1007/s007750050130 GBV_USEFLAG_U ZDB-1-SOJ GBV_NL_ARTICLE AR 2 1997 2 242-255 14 |
| allfieldsSound |
(DE-627)NLEJ206167822 DE-627 ger DE-627 rakwb eng Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR 1997 14 nicht spezifiziert zzz rdacontent nicht spezifiziert z rdamedia nicht spezifiziert zu rdacarrier Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge. Springer Online Journal Archives 1860-2002 Davydov, R. M. oth Ménage, Stéphane oth Fontecave, M. oth Gräslund, Astrid oth Ehrenberg, A. oth in JBIC 1996 2(1997) vom: Feb., Seite 242-255 (DE-627)NLEJ188989765 (DE-600)1464026-0 1432-1327 nnns volume:2 year:1997 month:02 pages:242-255 extent:14 http://dx.doi.org/10.1007/s007750050130 GBV_USEFLAG_U ZDB-1-SOJ GBV_NL_ARTICLE AR 2 1997 2 242-255 14 |
| language |
English |
| source |
in JBIC 2(1997) vom: Feb., Seite 242-255 volume:2 year:1997 month:02 pages:242-255 extent:14 |
| sourceStr |
in JBIC 2(1997) vom: Feb., Seite 242-255 volume:2 year:1997 month:02 pages:242-255 extent:14 |
| format_phy_str_mv |
Article |
| institution |
findex.gbv.de |
| isfreeaccess_bool |
false |
| container_title |
JBIC |
| authorswithroles_txt_mv |
Davydov, R. M. @@oth@@ Ménage, Stéphane @@oth@@ Fontecave, M. @@oth@@ Gräslund, Astrid @@oth@@ Ehrenberg, A. @@oth@@ |
| publishDateDaySort_date |
1997-02-01T00:00:00Z |
| hierarchy_top_id |
NLEJ188989765 |
| id |
NLEJ206167822 |
| language_de |
englisch |
| fullrecord |
<?xml version="1.0" encoding="UTF-8"?><collection xmlns="http://www.loc.gov/MARC21/slim"><record><leader>01000caa a22002652 4500</leader><controlfield tag="001">NLEJ206167822</controlfield><controlfield tag="003">DE-627</controlfield><controlfield tag="005">20210706193940.0</controlfield><controlfield tag="007">cr uuu---uuuuu</controlfield><controlfield tag="008">070528s1997 xx |||||o 00| ||eng c</controlfield><datafield tag="035" ind1=" " ind2=" "><subfield code="a">(DE-627)NLEJ206167822</subfield></datafield><datafield tag="040" ind1=" " ind2=" "><subfield code="a">DE-627</subfield><subfield code="b">ger</subfield><subfield code="c">DE-627</subfield><subfield code="e">rakwb</subfield></datafield><datafield tag="041" ind1=" " ind2=" "><subfield code="a">eng</subfield></datafield><datafield tag="245" ind1="1" ind2="0"><subfield code="a">Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR</subfield></datafield><datafield tag="264" ind1=" " ind2="1"><subfield code="c">1997</subfield></datafield><datafield tag="300" ind1=" " ind2=" "><subfield code="a">14</subfield></datafield><datafield tag="336" ind1=" " ind2=" "><subfield code="a">nicht spezifiziert</subfield><subfield code="b">zzz</subfield><subfield code="2">rdacontent</subfield></datafield><datafield tag="337" ind1=" " ind2=" "><subfield code="a">nicht spezifiziert</subfield><subfield code="b">z</subfield><subfield code="2">rdamedia</subfield></datafield><datafield tag="338" ind1=" " ind2=" "><subfield code="a">nicht spezifiziert</subfield><subfield code="b">zu</subfield><subfield code="2">rdacarrier</subfield></datafield><datafield tag="520" ind1=" " ind2=" "><subfield code="a">Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge.</subfield></datafield><datafield tag="533" ind1=" " ind2=" "><subfield code="f">Springer Online Journal Archives 1860-2002</subfield></datafield><datafield tag="700" ind1="1" ind2=" "><subfield code="a">Davydov, R. M.</subfield><subfield code="4">oth</subfield></datafield><datafield tag="700" ind1="1" ind2=" "><subfield code="a">Ménage, Stéphane</subfield><subfield code="4">oth</subfield></datafield><datafield tag="700" ind1="1" ind2=" "><subfield code="a">Fontecave, M.</subfield><subfield code="4">oth</subfield></datafield><datafield tag="700" ind1="1" ind2=" "><subfield code="a">Gräslund, Astrid</subfield><subfield code="4">oth</subfield></datafield><datafield tag="700" ind1="1" ind2=" "><subfield code="a">Ehrenberg, A.</subfield><subfield code="4">oth</subfield></datafield><datafield tag="773" ind1="0" ind2="8"><subfield code="i">in</subfield><subfield code="t">JBIC</subfield><subfield code="d">1996</subfield><subfield code="g">2(1997) vom: Feb., Seite 242-255</subfield><subfield code="w">(DE-627)NLEJ188989765</subfield><subfield code="w">(DE-600)1464026-0</subfield><subfield code="x">1432-1327</subfield><subfield code="7">nnns</subfield></datafield><datafield tag="773" ind1="1" ind2="8"><subfield code="g">volume:2</subfield><subfield code="g">year:1997</subfield><subfield code="g">month:02</subfield><subfield code="g">pages:242-255</subfield><subfield code="g">extent:14</subfield></datafield><datafield tag="856" ind1="4" ind2="0"><subfield code="u">http://dx.doi.org/10.1007/s007750050130</subfield></datafield><datafield tag="912" ind1=" " ind2=" "><subfield code="a">GBV_USEFLAG_U</subfield></datafield><datafield tag="912" ind1=" " ind2=" "><subfield code="a">ZDB-1-SOJ</subfield></datafield><datafield tag="912" ind1=" " ind2=" "><subfield code="a">GBV_NL_ARTICLE</subfield></datafield><datafield tag="951" ind1=" " ind2=" "><subfield code="a">AR</subfield></datafield><datafield tag="952" ind1=" " ind2=" "><subfield code="d">2</subfield><subfield code="j">1997</subfield><subfield code="c">2</subfield><subfield code="h">242-255</subfield><subfield code="g">14</subfield></datafield></record></collection>
|
| series2 |
Springer Online Journal Archives 1860-2002 |
| ppnlink_with_tag_str_mv |
@@773@@(DE-627)NLEJ188989765 |
| format |
electronic Article |
| delete_txt_mv |
keep |
| collection |
NL |
| remote_str |
true |
| illustrated |
Not Illustrated |
| issn |
1432-1327 |
| topic_title |
Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR |
| format_facet |
Elektronische Aufsätze Aufsätze Elektronische Ressource |
| format_main_str_mv |
Text Zeitschrift/Artikel |
| carriertype_str_mv |
zu |
| author2_variant |
r m d rm rmd s m sm m f mf a g ag a e ae |
| hierarchy_parent_title |
JBIC |
| hierarchy_parent_id |
NLEJ188989765 |
| hierarchy_top_title |
JBIC |
| isfreeaccess_txt |
false |
| familylinks_str_mv |
(DE-627)NLEJ188989765 (DE-600)1464026-0 |
| title |
Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR |
| spellingShingle |
Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR |
| ctrlnum |
(DE-627)NLEJ206167822 |
| title_full |
Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR |
| journal |
JBIC |
| journalStr |
JBIC |
| lang_code |
eng |
| isOA_bool |
false |
| recordtype |
marc |
| publishDateSort |
1997 |
| contenttype_str_mv |
zzz |
| container_start_page |
242 |
| container_volume |
2 |
| physical |
14 |
| format_se |
Elektronische Aufsätze |
| title_sort |
mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 k studied by epr |
| title_auth |
Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR |
| abstract |
Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge. |
| abstractGer |
Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge. |
| abstract_unstemmed |
Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge. |
| collection_details |
GBV_USEFLAG_U ZDB-1-SOJ GBV_NL_ARTICLE |
| title_short |
Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR |
| url |
http://dx.doi.org/10.1007/s007750050130 |
| remote_bool |
true |
| author2 |
Davydov, R. M. Ménage, Stéphane Fontecave, M. Gräslund, Astrid Ehrenberg, A. |
| author2Str |
Davydov, R. M. Ménage, Stéphane Fontecave, M. Gräslund, Astrid Ehrenberg, A. |
| ppnlink |
NLEJ188989765 |
| mediatype_str_mv |
z |
| isOA_txt |
false |
| hochschulschrift_bool |
false |
| author2_role |
oth oth oth oth oth |
| up_date |
2024-07-06T06:13:02.246Z |
| _version_ |
1803809070511030272 |
| fullrecord_marcxml |
<?xml version="1.0" encoding="UTF-8"?><collection xmlns="http://www.loc.gov/MARC21/slim"><record><leader>01000caa a22002652 4500</leader><controlfield tag="001">NLEJ206167822</controlfield><controlfield tag="003">DE-627</controlfield><controlfield tag="005">20210706193940.0</controlfield><controlfield tag="007">cr uuu---uuuuu</controlfield><controlfield tag="008">070528s1997 xx |||||o 00| ||eng c</controlfield><datafield tag="035" ind1=" " ind2=" "><subfield code="a">(DE-627)NLEJ206167822</subfield></datafield><datafield tag="040" ind1=" " ind2=" "><subfield code="a">DE-627</subfield><subfield code="b">ger</subfield><subfield code="c">DE-627</subfield><subfield code="e">rakwb</subfield></datafield><datafield tag="041" ind1=" " ind2=" "><subfield code="a">eng</subfield></datafield><datafield tag="245" ind1="1" ind2="0"><subfield code="a">Mixed-valent μ-oxo-bridged diiron complexes produced by radiolytic reduction at 77 K studied by EPR</subfield></datafield><datafield tag="264" ind1=" " ind2="1"><subfield code="c">1997</subfield></datafield><datafield tag="300" ind1=" " ind2=" "><subfield code="a">14</subfield></datafield><datafield tag="336" ind1=" " ind2=" "><subfield code="a">nicht spezifiziert</subfield><subfield code="b">zzz</subfield><subfield code="2">rdacontent</subfield></datafield><datafield tag="337" ind1=" " ind2=" "><subfield code="a">nicht spezifiziert</subfield><subfield code="b">z</subfield><subfield code="2">rdamedia</subfield></datafield><datafield tag="338" ind1=" " ind2=" "><subfield code="a">nicht spezifiziert</subfield><subfield code="b">zu</subfield><subfield code="2">rdacarrier</subfield></datafield><datafield tag="520" ind1=" " ind2=" "><subfield code="a">Abstract Several dinuclear diferric complexes were prepared, bridged by only an oxo ion, by an oxo ion and additionally one or two carboxylate groups, or by two hydroxo ions. Frozen solutions of these EPR-silent diferric complexes were radiolytically reduced by γ-irradiation at 77 K. The reduced forms gave EPR spectra typical of mixed-valent diiron species with S = 1/2. The yield was about 50% at high doses. With 57Fe replacing 56Fe the spectral features were broadened because of hyperfine interaction with one or both of the 57Fe nuclei. All oxo-bridged complexes give mixed-valent species with unbroadened EPR spectra observable up to 110 K. The anisotropy is small, Δg = g 1–g 3<0.07, and g av = (g 1+g 2+g 3)/3 falls in the range 1.93–1.96. Annealing at T≥115 K causes the EPR spectra to change and finally become more anisotropic, 0.14<Δg<0.32 and to have smaller g av, 1.78<g av<1.89. These spectra are observable only at T≤35 K. Radiolytic reduction of the diferric complexes with hydroxo bridges leads directly without annealing to this second type of mixed-valent species. The annealing-induced transition from a primary to a secondary mixed-valent species in the case of an oxo-bridged diferric starting complex is suggested to be a structural relaxation including protonation of the bridge. Annealing at temperatures above ca. 180 K and final thawing causes the mixed-valent dinuclear species to disappear, probably by disintegration to mononuclear species. These mixed-valent species are useful models for similar species in proteins, where primary-type species may take part in transient electron transfer, and the secondary-type species are usually more persistent forms in redox reactions. For proteins, available data show that there is a tendency for both primary and secondary species to have larger g anisotropy, Δg, and smaller g av, than obtained with the models. These differences suggest that the diiron centers of proteins are affected by their specific surroundings. Our results also show that the nature of the bridge, oxo or hydroxo, may not always safely be determined from a measured J value. Measurement of the EPR parameters, Δg, g av and limiting temperature of observation (relaxation properties) of a mixed-valent complex, or, in the case of a diferric complex, of the primary mixed-valent species induced by radiolysis at 77 K, offers an alternative empirically based method to determine the nature of the bridge.</subfield></datafield><datafield tag="533" ind1=" " ind2=" "><subfield code="f">Springer Online Journal Archives 1860-2002</subfield></datafield><datafield tag="700" ind1="1" ind2=" "><subfield code="a">Davydov, R. M.</subfield><subfield code="4">oth</subfield></datafield><datafield tag="700" ind1="1" ind2=" "><subfield code="a">Ménage, Stéphane</subfield><subfield code="4">oth</subfield></datafield><datafield tag="700" ind1="1" ind2=" "><subfield code="a">Fontecave, M.</subfield><subfield code="4">oth</subfield></datafield><datafield tag="700" ind1="1" ind2=" "><subfield code="a">Gräslund, Astrid</subfield><subfield code="4">oth</subfield></datafield><datafield tag="700" ind1="1" ind2=" "><subfield code="a">Ehrenberg, A.</subfield><subfield code="4">oth</subfield></datafield><datafield tag="773" ind1="0" ind2="8"><subfield code="i">in</subfield><subfield code="t">JBIC</subfield><subfield code="d">1996</subfield><subfield code="g">2(1997) vom: Feb., Seite 242-255</subfield><subfield code="w">(DE-627)NLEJ188989765</subfield><subfield code="w">(DE-600)1464026-0</subfield><subfield code="x">1432-1327</subfield><subfield code="7">nnns</subfield></datafield><datafield tag="773" ind1="1" ind2="8"><subfield code="g">volume:2</subfield><subfield code="g">year:1997</subfield><subfield code="g">month:02</subfield><subfield code="g">pages:242-255</subfield><subfield code="g">extent:14</subfield></datafield><datafield tag="856" ind1="4" ind2="0"><subfield code="u">http://dx.doi.org/10.1007/s007750050130</subfield></datafield><datafield tag="912" ind1=" " ind2=" "><subfield code="a">GBV_USEFLAG_U</subfield></datafield><datafield tag="912" ind1=" " ind2=" "><subfield code="a">ZDB-1-SOJ</subfield></datafield><datafield tag="912" ind1=" " ind2=" "><subfield code="a">GBV_NL_ARTICLE</subfield></datafield><datafield tag="951" ind1=" " ind2=" "><subfield code="a">AR</subfield></datafield><datafield tag="952" ind1=" " ind2=" "><subfield code="d">2</subfield><subfield code="j">1997</subfield><subfield code="c">2</subfield><subfield code="h">242-255</subfield><subfield code="g">14</subfield></datafield></record></collection>
|
| score |
7.397934 |