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Electronic and spatial structures of water-soluble dinitrosyl iron complexes with thiol-containing ligands underlying their ability to act as nitric oxide and nitrosonium ion donors.

Vanin AF, Burbaev DSh - J Biophys (2012)

Bottom Line: Similarly, the {(RS(-))(2)Fe(+)(NO(+))(2)}(+) structure describing the distribution of unpaired electron density in M-DNIC corresponds to the low-spin (S = 1/2) state with a d(7) electron configuration of the iron atom and predominant localization of the unpaired electron on MO(d(z2)) and the square planar structure of M-DNIC.On the other side, the formation of molecular orbitals of M-DNIC including orbitals of the iron atom, thiolate and nitrosyl ligands results in a transfer of electron density from sulfur atoms to the iron atom and nitrosyl ligands.Most probably, the S-nitrosating effect of nitrosyl ligands is a result of weak binding of thiolate ligands to the iron atom under conditions favoring destabilization of M-DNIC.

View Article: PubMed Central - PubMed

Affiliation: N. N. Semyonov Institute of Chemical Physics, Russian Academy of Sciences, Kosygin Street 4, Moscow 119991, Russia.

ABSTRACT
The ability of mononuclear dinitrosyl iron commplexes (M-DNICs) with thiolate ligands to act as NO donors and to trigger S-nitrosation of thiols can be explain only in the paradigm of the model of the [Fe(+)(NO(+))(2)] core ({Fe(NO)(2)}(7) according to the Enemark-Feltham classification). Similarly, the {(RS(-))(2)Fe(+)(NO(+))(2)}(+) structure describing the distribution of unpaired electron density in M-DNIC corresponds to the low-spin (S = 1/2) state with a d(7) electron configuration of the iron atom and predominant localization of the unpaired electron on MO(d(z2)) and the square planar structure of M-DNIC. On the other side, the formation of molecular orbitals of M-DNIC including orbitals of the iron atom, thiolate and nitrosyl ligands results in a transfer of electron density from sulfur atoms to the iron atom and nitrosyl ligands. Under these conditions, the positive charge on the nitrosyl ligands diminishes appreciably, the interaction of the ligands with hydroxyl ions or with thiols slows down and the hydrolysis of nitrosyl ligands and the S-nitrosating effect of the latter are not manifested. Most probably, the S-nitrosating effect of nitrosyl ligands is a result of weak binding of thiolate ligands to the iron atom under conditions favoring destabilization of M-DNIC.

No MeSH data available.


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Mentions: Previous studies showed that the synthesis of DNIC with non-thiol ligands is accompanied by the formation of nitrous oxide (N2O) [42]. This finding prompted us to suggest a hypothetical mechanism of M-DNIC formation, of N2O formation, in particular [39, 43]. We proceeded from the assumption that binding of two NO molecules to Fe2+ ions results in their disproportionation and conversion into nitrosonium and nitroxyl ions (NO+ and NO−, resp.). Protonation of the latter yields nitroxyl (HNO), which leaves the coordination sphere of Fe2+. Recombination of two nitroxyl molecules gives nitrous oxide (Scheme 1); subsequent incorporation of the NO molecule into M-DNIC instead of nitroxyl is accompanied by a transfer of the unpaired electron from the latter to iron and formation of the {Fe+(NO+)2} fragment and, as a consequence, of M-DNIC with thiol-containing (RS−) ligands of the formula {(RS−)2Fe+(NO+)2}+ with a d7configuration of the iron atom ({Fe(NO)2}7 according to the Enemark-Feltham classification [44]). (For the presence in DNIC of only two thiol-containing ligands see below). The concomitant formation of nitrous oxide (N2O) in the course of M-DNIC synthesis and the involvement of three NO molecules in the formation of one M-DNIC were confirmed in more recent studies [45, 46].


Electronic and spatial structures of water-soluble dinitrosyl iron complexes with thiol-containing ligands underlying their ability to act as nitric oxide and nitrosonium ion donors.

Vanin AF, Burbaev DSh - J Biophys (2012)

© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3306989&req=5

Mentions: Previous studies showed that the synthesis of DNIC with non-thiol ligands is accompanied by the formation of nitrous oxide (N2O) [42]. This finding prompted us to suggest a hypothetical mechanism of M-DNIC formation, of N2O formation, in particular [39, 43]. We proceeded from the assumption that binding of two NO molecules to Fe2+ ions results in their disproportionation and conversion into nitrosonium and nitroxyl ions (NO+ and NO−, resp.). Protonation of the latter yields nitroxyl (HNO), which leaves the coordination sphere of Fe2+. Recombination of two nitroxyl molecules gives nitrous oxide (Scheme 1); subsequent incorporation of the NO molecule into M-DNIC instead of nitroxyl is accompanied by a transfer of the unpaired electron from the latter to iron and formation of the {Fe+(NO+)2} fragment and, as a consequence, of M-DNIC with thiol-containing (RS−) ligands of the formula {(RS−)2Fe+(NO+)2}+ with a d7configuration of the iron atom ({Fe(NO)2}7 according to the Enemark-Feltham classification [44]). (For the presence in DNIC of only two thiol-containing ligands see below). The concomitant formation of nitrous oxide (N2O) in the course of M-DNIC synthesis and the involvement of three NO molecules in the formation of one M-DNIC were confirmed in more recent studies [45, 46].

Bottom Line: Similarly, the {(RS(-))(2)Fe(+)(NO(+))(2)}(+) structure describing the distribution of unpaired electron density in M-DNIC corresponds to the low-spin (S = 1/2) state with a d(7) electron configuration of the iron atom and predominant localization of the unpaired electron on MO(d(z2)) and the square planar structure of M-DNIC.On the other side, the formation of molecular orbitals of M-DNIC including orbitals of the iron atom, thiolate and nitrosyl ligands results in a transfer of electron density from sulfur atoms to the iron atom and nitrosyl ligands.Most probably, the S-nitrosating effect of nitrosyl ligands is a result of weak binding of thiolate ligands to the iron atom under conditions favoring destabilization of M-DNIC.

View Article: PubMed Central - PubMed

Affiliation: N. N. Semyonov Institute of Chemical Physics, Russian Academy of Sciences, Kosygin Street 4, Moscow 119991, Russia.

ABSTRACT
The ability of mononuclear dinitrosyl iron commplexes (M-DNICs) with thiolate ligands to act as NO donors and to trigger S-nitrosation of thiols can be explain only in the paradigm of the model of the [Fe(+)(NO(+))(2)] core ({Fe(NO)(2)}(7) according to the Enemark-Feltham classification). Similarly, the {(RS(-))(2)Fe(+)(NO(+))(2)}(+) structure describing the distribution of unpaired electron density in M-DNIC corresponds to the low-spin (S = 1/2) state with a d(7) electron configuration of the iron atom and predominant localization of the unpaired electron on MO(d(z2)) and the square planar structure of M-DNIC. On the other side, the formation of molecular orbitals of M-DNIC including orbitals of the iron atom, thiolate and nitrosyl ligands results in a transfer of electron density from sulfur atoms to the iron atom and nitrosyl ligands. Under these conditions, the positive charge on the nitrosyl ligands diminishes appreciably, the interaction of the ligands with hydroxyl ions or with thiols slows down and the hydrolysis of nitrosyl ligands and the S-nitrosating effect of the latter are not manifested. Most probably, the S-nitrosating effect of nitrosyl ligands is a result of weak binding of thiolate ligands to the iron atom under conditions favoring destabilization of M-DNIC.

No MeSH data available.