title: Syntheses, structures, and photochemistry of manganese nitrosyls derived from designed Schiff base ligands: potential NO donors that can be activated by near-infrared light.
abstract: Two manganese nitrosyls, namely, [Mn(SBPy(3))(NO)](ClO(4))(2) (1) and [Mn(SBPy(2)Q)(NO)](ClO(4))(2) (2), have been synthesized by using designed pentadentate Schiff base ligands N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-aldimine (SBPy(3)) and N,N-bis(2-pyridyl methyl)amine-N-ethyl-2-quinoline-2-aldimine (SBPy(2)Q). Reaction of NO(g) with [Mn(SBPy(3))(MeOH)](ClO(4))(2) and [Mn(SBPy(2)Q)(EtOH)](ClO(4))(2) in MeCN affords 1 and 2, respectively, in good yields. Narrow-width peaks in the (1)H NMR spectra and strong nu(NO) at 1773 cm(-1) (of 1) and 1759 cm(-1) (of 2) confirm a strongly coupled {low-spin Mn(II)-NO*}formulation for both these {Mn-NO}(6) nitrosyls. In MeCN, 1 exhibits two strong absorption bands with lambda(max) at 500 and 720 nm. These bands red shift to 550 and 785 nm in case of 2 because of substitution of the pyridyl-imine moiety of SBPy(3) with quinolyl-imine moiety in the SBPy(2)Q ligand frame. Exposure of solutions 1 and 2 to near-infrared (NIR) light (780 nm, 5 mW) results in rapid bleaching of the orange and fuchsia solutions, and free NO is detected in the solutions by an NO-sensitive electrode. The high quantum yield values (Phi) of 1 (0.580 +/- 0.010, lambda(irr) = 550 nm, MeCN) and 2 (0.434 +/- 0.010, lambda(irr) = 550 nm, MeCN) and in particular their sensitivity to NIR light of 800-950 nm range strongly suggest that these designed manganese nitrosyls could be used as NIR light-triggered NO donors.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA.
authors.forename: C Gianna
authors.initials: CG
authors.lastname: Hoffman-Luca
authors.forename: Aura A
authors.initials: AA
authors.lastname: Eroy-Reveles
authors.forename: Jose
authors.initials: J
authors.lastname: Alvarenga
authors.forename: Pradip K
authors.initials: PK
authors.lastname: Mascharak
mesh_terms: D007097:Imines / Q000737:chemistry; D007259:Infrared Rays; D008024:Ligands; D008345:Manganese / Q000737:chemistry*; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D010777:Photochemistry / Q000379:methods; D011725:Pyridines / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D007097:Imines; D008024:Ligands; C469210:N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-aldimine; D011725:Pyridines; D012545:Schiff Bases; D009569:Nitric Oxide; D008345:Manganese