title: Syntheses, structures, and reactivities of (Fe-NO)6 nitrosyls derived from polypyridine-carboxamide ligands: photoactive NO-donors and reagents for S-nitrosylation of alkyl thiols.
abstract: Two new iron nitrosyls derived from two designed pentadentate ligands N,N-bis(2-pyridylmethyl)-amine-N'-(2-pyridylmethyl)acetamide and N,N-bis(2-pyridylmethyl)-amine-N'-[1-(2-pyridinyl)ethyl]acetamide (PcPy(3)H and MePcPy(3)H, respectively, where H is the dissociable amide proton) have been structurally characterized. These complexes are similar to a previously reported (Fe-NO)6 complex, [(PaPy(3))Fe(NO)](ClO(4))(2) (1) that releases NO under mild conditions. The present nitrosyls, namely [(PcPy(3))Fe(NO)](ClO(4))(2) (2) and [(MePcPy(3))Fe(NO)](ClO(4))(2) (3), belong to the same (Fe-NO)6 family and exhibit (a) clean (1)H NMR spectra in CD(3)CN indicating S = 0 ground state, (b) almost linear Fe-N-O angles (177.3(5) degrees and 177.6(4) degrees for 2 and 3, respectively), and (c) N-O stretching frequencies (nu(NO)) in the range 1900-1925 cm(-)(1). The binding of NO at the non-heme iron centers of 1-3 is completely reversible and all three nitrosyls rapidly release NO when exposed to light (50 W tungsten bulb). In addition to acting as photoactive NO-donors, these complexes also nitrosylate thiols such as N-acetylpenicillamine, 3-mercaptopropionic acid, and N-acetyl-cysteine-methyl-ester in yields that range from 30 to 90% in the absence of light. The addition of alkyl or aryl thiolate (RS(-)) to the (Fe-NO)6 complexes in the absence of dioxygen results in the reduction of the iron metal center to afford the corresponding (Fe-NO)7 species.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
authors.forename: Raman K
authors.initials: RK
authors.lastname: Afshar
authors.forename: Apurba K
authors.initials: AK
authors.lastname: Patra
authors.forename: Marilyn M
authors.initials: MM
authors.lastname: Olmstead
authors.forename: Pradip K
authors.initials: PK
authors.lastname: Mascharak
mesh_terms: D000577:Amides / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007202:Indicators and Reagents; D007501:Iron / Q000737:chemistry; D008024:Ligands; D008956:Models, Chemical; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000138:chemical synthesis / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D010777:Photochemistry; D011108:Polymers / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D000577:Amides; D007202:Indicators and Reagents; D008024:Ligands; D009589:Nitrogen Oxides; D009942:Organometallic Compounds; D011108:Polymers; D011725:Pyridines; D013438:Sulfhydryl Compounds; D009569:Nitric Oxide; C073661:dinitrosyl iron complex; D007501:Iron