50262-98-1Relevant academic research and scientific papers
Photoluminescent properties of cadmium selenide in contact with solutions and films of metalloporphyrins: Nitric oxide sensing and evidence for the aversion of an analyte to a buried semiconductor-film interface
Ivanisevic, Albena,Reynolds, Mark F.,Burstyn, Judith N.,Ellis, Arthur B.
, p. 3731 - 3738 (2000)
The band-edge photoluminescence (PL) intensity of etched n-CdSe single crystals is quenched reversibly by adsorption of the trivalent metalloporphyrins, MTPPCl (TPP = tetraphenylporphyrin; M = Mn, Fe, Co) in nitrogen-saturated methylene chloride solution. The PL responses are concentration dependent and can be fit to the Langmuir adsorption isotherm model to yield binding constants of ～103-104 M-1. The MTPPCl compounds react irreversibly with NO in solution to form nitrosyl adducts, and these compounds reversibly enhance the CdSe PL intensity when adsorbed onto the semiconductor surface, also with binding constants of ～103-104 M-1. Films of MTPPCl were prepared on CdSe substrates by solvent evaporation. These coatings serve as transducers for NO detection: while the bare CdSe surface shows no response to NO gas relative to N2, the coated surfaces reversibly enhance the PL intensity (CoTPPCl) or quench it (MnTPPCl and FeTPPCl), with binding constants on the order of ～1 atm-1. In contrast to the PL results, which are particularly sensitive to the semiconductor-film interface, electronic and IR spectral changes of the bulk film induced by NO binding were irreversible. The UV-vis and IR spectra could be spectroscopically mimicked by preformed nitrosyl adduct films that were prepared by solvent evaporation of MTPPCl (M = Co, Fe) and MTPP (M = Co) solutions that had been exposed to NO. These films, however, lack transduction capability, as the PL intensity is the same in NO and N2 ambients. For the films prepared from FeTPPCl and CoTPPCl, the saturation of IR and UV-vis spectral changes occurs at NO pressures at least 10-fold lower than observed for PL changes. These results indicate that NO has a strong aversion to binding at the semiconductor-film interface as opposed to the bulk film environment. Steric and electronic contributions to these observed effects are discussed.
Ferric Heme-Nitrosyl Complexes: Kinetically Robust or Unstable Intermediates?
McQuarters, Ashley B.,Kampf, Jeff W.,Alp, E. Ercan,Hu, Michael,Zhao, Jiyong,Lehnert, Nicolai
, p. 10513 - 10528 (2017/09/12)
We have determined a convenient method for the bulk synthesis of high-purity ferric heme-nitrosyl complexes ({FeNO}6 in the Enemark-Feltham notation); this method is based on the chemical or electrochemical oxidation of corresponding {FeNO}7 precursors. We used this method to obtain the five- and six-coordinate complexes [Fe(TPP)(NO)]+ (TPP2- = tetraphenylporphyrin dianion) and [Fe(TPP)(NO)(MI)]+ (MI = 1-methylimidazole) and demonstrate that these complexes are stable in solution in the absence of excess NO gas. This is in stark contrast to the often-cited instability of such {FeNO}6 model complexes in the literature, which is likely due to the common presence of halide impurities (although other impurities could certainly also play a role). This is avoided in our approach for the synthesis of {FeNO}6 complexes via oxidation of pure {FeNO}7 precursors. On the basis of these results, {FeNO}6 complexes in proteins do not show an increased stability toward NO loss compared to model complexes. We also prepared the halide-coordinated complexes [Fe(TPP)(NO)(X)] (X = Cl-, Br-), which correspond to the elusive, key reactive intermediate in the so-called autoreduction reaction, which is frequently used to prepare {FeNO}7 complexes from ferric precursors. All of the complexes were characterized using X-ray crystallography, UV-vis, IR, and nuclear resonance vibrational spectroscopy (NRVS). On the basis of the vibrational data, further insight into the electronic structure of these {FeNO}6 complexes, in particular with respect to the role of the axial ligand trans to NO, is obtained.
