Acid-induced reduction of nitrites(NO_(2)-)to nitric oxide(NO)at Cu/Fe centers is one of the key steps in the nitrogen cycle and serves as an essential path to NO generation.In this study,we report the acid-catalysed ...Acid-induced reduction of nitrites(NO_(2)-)to nitric oxide(NO)at Cu/Fe centers is one of the key steps in the nitrogen cycle and serves as an essential path to NO generation.In this study,we report the acid-catalysed conversion of NO_(2)-to NO at the Cu^(II)centers in Cu^(II)-nitrito complexes,[(Me_(2)BPMEN)Cu^(II)(NO_(2)-)]+(1)and[(H_(2)BPMEN)Cu^(II)(NO_(2)-)]+(2).Both the Cu^(II)-NO_(2)-complexes showed the formation of NO(g)along with H_(2)O_(2)when reacted with one equivalent acid(H6^(+))via the N-O bond homolysis of the presumed Cu^(II)-nitrous acid([Cu-ONOH]^(2+))intermediate.However,the H_(2)O_(2)amount decreased with time or an increase in H6^(+)and completely disappeared when H6^(+)was more than about two equivalents accompanied by the generation of H_(2)O.We detected the released NO(g)by using headspace gas chromatography/mass spectrometry;moreover,the NO(g)evolution was confirmed by the formation of a significant amount of{CoNO}^(8),[(12-TMC)Co(NO)]^(2+)up to(90±5%)in the above reactions.Mechanistic investigations using^(15)N-labeled-^(15)NO_(2)-and^(18)O-labeled-^(16)O^(14)N^(18)O-revealed that the N-atom in NO is derived from the^(18)ONO-ligand,which was further confirmed by the detection of^(15)NO and N^(18)O gas in headspace gas chromatography/mass spectrometry.We also monitored and characterized the formation of H_(2)O_(2)(one equivalent of H6^(+))and H_(2)O(two equivalents of H6^(+))and the results describe the rationale behind biological NO_(2)-reduction reactions generating NO along with H_(2)O.We observed more than 90%recovery of(1)after 10 catalytic cycles of NO(g)generation.展开更多
Here,we report the nitric oxide dioxygenation(NOD)reactions of Ni^(III)-peroxo,[(12-TMC)Ni^(III)(O_(2)^(2-))]^(+)(Ni^(III)-O_(2)^(2-),1),and Co^(III)-peroxo,[(12-TMC)Co^(III)(O_(2)^(2-))]^(+)(Co^(III)-O_(2)^(2-),2),co...Here,we report the nitric oxide dioxygenation(NOD)reactions of Ni^(III)-peroxo,[(12-TMC)Ni^(III)(O_(2)^(2-))]^(+)(Ni^(III)-O_(2)^(2-),1),and Co^(III)-peroxo,[(12-TMC)Co^(III)(O_(2)^(2-))]^(+)(Co^(III)-O_(2)^(2-),2),complexes bearing N-tetramethylated cyclam(TMC)ligands.The reaction of complex 1 with nitric oxide(NO)generates Ni^(II)-nitrato complex[(12-TMC)Ni^(II)(NO_(3)^(-))]^(+)(Ni^(II)-NO_(3)^(-),3).However,in contrast to the NOD reaction of 1,compound 2 produces Co^(II)-nitrito complex,[(12-TMC)Co^(II)(NO_(2)^(-))]^(+)(Co^(II)-NO_(2)^(-),4),with O_(2)gas formation.Results suggested the formation of a presumptive Ni-peroxynitrite([Ni-PN]^(+),[Ni-ONOO^(-)]^(+))intermediate,in the NOD reaction of 1,prior to the generation of Ni^(II)-NO_(3)^(-)(3).Although the end product of the reaction of 2 with NO is different from that of 1,the mechanistic study explored by using 2,4-di-tert-butylphenol(2,4-DTBP)suggested that the reaction of 2 with NO also occurs via a presumed Co-peroxynitrite([Co-PN]^(+),[Co-ONOO^(-)]^(+))intermediate.Furthermore,exploring these NOD reactions and tracking the oxygen atom using 18O-labeled hydrogen peroxide(H_(2)^(18)O_(2))revealed that two oxygen atoms of 3(Ni^(II)-18O_(2)N^(16)O^(-))and one oxygen atom of 4(Co^(II)-18ON^(16)O^(-))are derived from the peroxo(O_(2)^(2-))moieties of 1 and 2,respectively.Furthermore,we have explored the M-peroxo regeneration from NOD products(3 and 4),and for the first time,we have observed the formation of M^(III)-O_(2)^(2-)complexes,1 and 2,upon treatment with H_(2)O_(2)and triethylamine(TEA),respectively.This work is the first-ever report which showed the exact NO dioxygenase(NOD)enzyme catalytic cycle.Furthermore,we have also explored the NO activation of 3 and 4,and surprisingly,we observed the formation of Co-nitrosyl(5)from 4 upon reaction with NO;in contrast,3 was unreactive towards NO.Evidence supporting the formation of[Ni-PN]^(+)and[Co-PN]^(+)intermediates is also presented.展开更多
基金supported by Grants-in-Aid(CRG/2021/003371)from SERB-DST.P.B.Kulbir,thank IISER Tirupati for their fellowship.
文摘Acid-induced reduction of nitrites(NO_(2)-)to nitric oxide(NO)at Cu/Fe centers is one of the key steps in the nitrogen cycle and serves as an essential path to NO generation.In this study,we report the acid-catalysed conversion of NO_(2)-to NO at the Cu^(II)centers in Cu^(II)-nitrito complexes,[(Me_(2)BPMEN)Cu^(II)(NO_(2)-)]+(1)and[(H_(2)BPMEN)Cu^(II)(NO_(2)-)]+(2).Both the Cu^(II)-NO_(2)-complexes showed the formation of NO(g)along with H_(2)O_(2)when reacted with one equivalent acid(H6^(+))via the N-O bond homolysis of the presumed Cu^(II)-nitrous acid([Cu-ONOH]^(2+))intermediate.However,the H_(2)O_(2)amount decreased with time or an increase in H6^(+)and completely disappeared when H6^(+)was more than about two equivalents accompanied by the generation of H_(2)O.We detected the released NO(g)by using headspace gas chromatography/mass spectrometry;moreover,the NO(g)evolution was confirmed by the formation of a significant amount of{CoNO}^(8),[(12-TMC)Co(NO)]^(2+)up to(90±5%)in the above reactions.Mechanistic investigations using^(15)N-labeled-^(15)NO_(2)-and^(18)O-labeled-^(16)O^(14)N^(18)O-revealed that the N-atom in NO is derived from the^(18)ONO-ligand,which was further confirmed by the detection of^(15)NO and N^(18)O gas in headspace gas chromatography/mass spectrometry.We also monitored and characterized the formation of H_(2)O_(2)(one equivalent of H6^(+))and H_(2)O(two equivalents of H6^(+))and the results describe the rationale behind biological NO_(2)-reduction reactions generating NO along with H_(2)O.We observed more than 90%recovery of(1)after 10 catalytic cycles of NO(g)generation.
文摘Here,we report the nitric oxide dioxygenation(NOD)reactions of Ni^(III)-peroxo,[(12-TMC)Ni^(III)(O_(2)^(2-))]^(+)(Ni^(III)-O_(2)^(2-),1),and Co^(III)-peroxo,[(12-TMC)Co^(III)(O_(2)^(2-))]^(+)(Co^(III)-O_(2)^(2-),2),complexes bearing N-tetramethylated cyclam(TMC)ligands.The reaction of complex 1 with nitric oxide(NO)generates Ni^(II)-nitrato complex[(12-TMC)Ni^(II)(NO_(3)^(-))]^(+)(Ni^(II)-NO_(3)^(-),3).However,in contrast to the NOD reaction of 1,compound 2 produces Co^(II)-nitrito complex,[(12-TMC)Co^(II)(NO_(2)^(-))]^(+)(Co^(II)-NO_(2)^(-),4),with O_(2)gas formation.Results suggested the formation of a presumptive Ni-peroxynitrite([Ni-PN]^(+),[Ni-ONOO^(-)]^(+))intermediate,in the NOD reaction of 1,prior to the generation of Ni^(II)-NO_(3)^(-)(3).Although the end product of the reaction of 2 with NO is different from that of 1,the mechanistic study explored by using 2,4-di-tert-butylphenol(2,4-DTBP)suggested that the reaction of 2 with NO also occurs via a presumed Co-peroxynitrite([Co-PN]^(+),[Co-ONOO^(-)]^(+))intermediate.Furthermore,exploring these NOD reactions and tracking the oxygen atom using 18O-labeled hydrogen peroxide(H_(2)^(18)O_(2))revealed that two oxygen atoms of 3(Ni^(II)-18O_(2)N^(16)O^(-))and one oxygen atom of 4(Co^(II)-18ON^(16)O^(-))are derived from the peroxo(O_(2)^(2-))moieties of 1 and 2,respectively.Furthermore,we have explored the M-peroxo regeneration from NOD products(3 and 4),and for the first time,we have observed the formation of M^(III)-O_(2)^(2-)complexes,1 and 2,upon treatment with H_(2)O_(2)and triethylamine(TEA),respectively.This work is the first-ever report which showed the exact NO dioxygenase(NOD)enzyme catalytic cycle.Furthermore,we have also explored the NO activation of 3 and 4,and surprisingly,we observed the formation of Co-nitrosyl(5)from 4 upon reaction with NO;in contrast,3 was unreactive towards NO.Evidence supporting the formation of[Ni-PN]^(+)and[Co-PN]^(+)intermediates is also presented.
