title: Synthesis, characterization, and spectroscopy of model molybdopterin complexes.
abstract: The preparation and characterization of new model complexes for the molybdenum cofactor are reported. The new models are distinctive for the inclusion of pterin-substituted dithiolene chelates and have the formulation Tp(*)MoX(pterin-R-dithiolene) (Tp(*)=tris(3,5,-dimethylpyrazolyl)borate), X=O, S, R=aryl. Syntheses of Mo(4+) and (5+) complexes of two pterin-dithiolene derivatives as both oxo and sulfido compounds, and improved syntheses for pterinyl alkynes and [Et(4)N][Tp(*)Mo(IV)(S)S(4)] reagents are described. Characterization methods include electrospray ionization mass spectrometry, electrochemistry, infrared spectroscopy, electron paramagnetic resonance and magnetic circular dichroism. Cyclic voltammetry reveals that the Mo(5+/4+) reduction potential is intermediate between that for dithiolenes with electron-withdrawing substituents and simple dithiolates chelates. Electron paramagnetic resonance and magnetic circular dichroism of Mo(5+) complexes where X=O, R=aryl indicates that the molybdenum environment in the new models is electronically similar to that in Tp(*)MoO(benzenedithiolate).
authors.affiliation: Department of Chemistry, Bryn Mawr College, Bryn Mawr, PA 19010, USA. sburgmay@brynmawr.edu
authors.forename: Sharon J Nieter
authors.initials: SJ
authors.lastname: Burgmayer
authors.forename: Mary
authors.initials: M
authors.lastname: Kim
authors.forename: Rebecca
authors.initials: R
authors.lastname: Petit
authors.forename: Amy
authors.initials: A
authors.lastname: Rothkopf
authors.forename: Alison
authors.initials: A
authors.lastname: Kim
authors.forename: Shadia
authors.initials: S
authors.lastname: BelHamdounia
authors.forename: Ying
authors.initials: Y
authors.lastname: Hou
authors.forename: Arpad
authors.initials: A
authors.lastname: Somogyi
authors.forename: Diana
authors.initials: D
authors.lastname: Habel-Rodriguez
authors.forename: Antonio
authors.initials: A
authors.lastname: Williams
authors.forename: Martin L
authors.initials: ML
authors.lastname: Kirk
mesh_terms: D002942:Circular Dichroism; D003067:Coenzymes / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D009682:Magnetic Resonance Spectroscopy; D008667:Metalloproteins / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D000090006:Molybdenum Cofactors; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D011621:Pteridines / Q000737:chemistry*; D011622:Pterins / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D003067:Coenzymes; D008667:Metalloproteins; D000090006:Molybdenum Cofactors; D009942:Organometallic Compounds; D011621:Pteridines; D011622:Pterins; C490076:pyranopterin; C022261:molybdopterin