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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.

SUBMITTER: Hoffman-Luca CG

PROVIDER: S-EPMC4826278 | biostudies-literature | 2009 Oct

REPOSITORIES: biostudies-literature

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Syntheses, structures, and photochemistry of manganese nitrosyls derived from designed Schiff base ligands: potential NO donors that can be activated by near-infrared light.

Hoffman-Luca C Gianna CG Eroy-Reveles Aura A AA Alvarenga Jose J Mascharak Pradip K PK

Inorganic chemistry 20091001 19

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) ...[more]

PMID: 19722518

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Project description:A new family of dicopper(I) complexes [CuI2RL](X)2 (R=H, 1X, R=tBu, 2X and R=NO2, 3X, X=CF3SO3, ClO4, SbF6, or BArF, BArF=[B{3,5-(CF3)2C6H3}4]-), where RL is a Schiff-base ligand containing two tridentate binding sites linked by a xylyl spacer, has been prepared and characterized, and its reaction with O2 has been studied. The complexes were designed with the aim of reproducing structural aspects of the active site of type 3 dicopper proteins; they contain two three-coordinate copper sites and a rather flexible podand ligand backbone. The solid-state structures of 1ClO4, 2CF3SO3, 2ClO4, and 3BArF.CH3CN have been established by single-crystal X-ray diffraction analysis. 1ClO4 adopts a polymeric structure in the solid state while 2CF3SO3, 2ClO4, and 3BArF.CH3CN are monomeric. The complexes have been studied in solution by means of 1H and 19F NMR spectroscopy, which put forward the presence of dynamic processes. 1-3BArF and 1-3CF3SO3 in acetone react rapidly with O2 to generate metaestable [CuIII2(mu-O)2(RL)]2+ 1-3(O2) and [CuIII2(mu-O)2(CF3SO3)(RL)]+ 1-3(O2)(CF3SO3) species, respectively, that have been characterized by UV-vis spectroscopy and resonance Raman analysis. Instead, reaction of 1-3BArF with O2 in CH2Cl2 results in intermolecular O2 binding. DFT methods have been used to study the chemical identities and structural parameters of the O2 adducts, and the relative stability of the CuIII2(mu-O)2 form with respect to the CuII2(mu-eta2:eta2-O2) isomer. The reaction of 1X, X = CF3SO3 and BArF, with O2 in acetone has been studied by stopped-flow UV-vis exhibiting an unexpected very fast reaction rate (k=3.82(4)x10(3) M-1 s-1, DeltaH=4.9+/-0.5 kJ.mol-1, DeltaS=-148+/-5 J.K-1.mol-1), nearly 3 orders of magnitude faster than in the parent [CuI2(m-XYLMeAN)]2+. Thermal decomposition of 1-3(O2) does not result in aromatic hydroxylation. The mechanism and kinetics of O2 binding to 1X (X=CF3SO3 and BArF) are discussed and compared with those associated with selected examples of reported models of O2-processing copper proteins. A synergistic role of the copper ions in O2 binding and activation is clearly established from this analysis.

Dataset Information

Syntheses, structures, and photochemistry of manganese nitrosyls derived from designed Schiff base ligands: potential NO donors that can be activated by near-infrared light.

Publications

Syntheses, structures, and photochemistry of manganese nitrosyls derived from designed Schiff base ligands: potential NO donors that can be activated by near-infrared light.

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