A positive myocardial inotropic effect achieved using HNO/NO(-) , compared with NO⋅, triggered attempts to explore novel nitroxyl donors for use in clinical applications in vascular and myocardial pharmacology. To develop M-NO complexes for nitroxyl chemistry and biology, modulation of direct nitroxyl-transfer reactivity of dinitrosyl iron complexes (DNICs) is investigated in this study using a Fe(III) -porphyrin complex and proteins as a specific probe. Stable dinuclear {Fe(NO)2 }(9) DNIC [Fe(μ-(Me) Pyr)(NO)2 ]2 was discovered as a potent nitroxyl donor for nitroxylation of Fe(III) -heme centers through an associative mechanism. Beyond the efficient nitroxyl transfer, transformation of DNICs into a chemical biology probe for nitroxyl and for pharmaceutical applications demands further efforts using in vitro/in vivo studies.
The adsorption of methyl red (MR) isomers (ortho, meta, and para) on metal-organic frameworks (MOFs) was investigated by using a fluorescence quenching technique. All three MR isomers were found to quench the fluorescence of MOFs effectively. Nonlinear fluorescence quenching trends were observed in Stern-Volmer plots. A modified nonlinear Stern-Volmer equation with the concepts of multiple adsorption sites, adsorption strength, and quencher accessibility was successfully adopted to fit the fluorescence quenching data. The fitted parameters were correlated with the structural properties of MRs and MOFs. The order of quenching efficiency was found to be m-MR > p-MR > o-MR for all MOFs. This indicates that MR molecules not only adsorb via carboxylate-metal bonding but also adsorb through π-π interactions between the aromatic rings of MR and linker molecules in MOFs. The position of the carboxylate group in MRs and the structure of the linkers in MOFs are the key factors affecting the fluorescence quenching efficiency.
The carbonization
of various types of metal–organic frameworks
(MOFs) was carried out under N2 gas flow and high temperature.
The formation of carbonized MOFs (CMOFs) was monitored by Raman spectroscopy.
In addition to the well-known D and G bands in Raman spectra, the
salient G′ band feature was observed only in Mn-, Fe-, Co-,
and Ni-containing CMOFs. On the other hand, CMOFs containing other
metals (Al, Cr, V, Cu, and Zr) do not show the G′ band. Furthermore,
the G′ band was also observed when we mixed the nitrate salts
of Mn(II), Fe(III), and Co(II) with Al-containing MOFs using the same
treatment conditions as in the formation of CMOFs. The G′ band
is known to be related to the stacking order of graphitic layers.
The presence of the Raman G′ band in CMOFs can be ascribed
to the catalytic activity of Mn, Fe, Co, and Ni. The trend of the
G′ band to G band intensity ratio resembles the “volcano
curve” in the description of the behavior of catalytic activities
of transition metals. The G′ bands in Mn-, Fe-, Co-, and Ni-containing
CMOFs were well-fitted with two-component peaks which indicates that
these CMOFs have well-stacked graphitic structures.
Four lithium coordination polymers, [Li3(BTC)(H2O)6] (1), [Li3(BTC)(H2O)5] (2), [Li3(BTC)(μ2-H2O)] (3), and [Li(H2BTC)(H2O)] (4) (H3BTC = 1,3,5-benzenetricarboxylatic acid), have been synthesized and characterized. All the structures have been determined using single crystal X-ray diffraction studies. Complexes 1 and 2 have two-dimensional (2-D) sheets, whereas complex 3 has three-dimensional (3-D) frameworks and complex 4 has one-dimensional (1-D) tubular chains. The crystal-to-crystal transformation was observed in 1–3 upon removal of water molecules, which accompanied the changes in structures and ligand bridging modes. Furthermore, the electrochemical properties of complexes 3 and 4 have been studied to evaluate these compounds as electrode materials in lithium ion batteries with the discharge capacities of 120 and 257 mAhg−1 in the first thirty cycles, respectively.
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