Altering the Coordination of Iron Porphyrins by Ionic Liquid Nanodomains in Mixed Solvent Systems

The solvent environment around iron porphyrin complexes was examined using mixed molecular/RTIL (room temperature ionic liquid) solutions. The formation of nanodomains in these solutions provides different solvation environments for substrates that could have significant impact on their chemical reactivity. Iron porphyrins (Fe(P)), whose properties are sensitive to solvent and ligation changes, were used to probe the molecular/RTIL environment. The addition of RTILs to molecular solvents shifted the redox potentials to more positive values. When there was no ligation change upon reduction, the shift in the E° values were correlated to the Gutmann acceptor number, as was observed for other porphyrins with similar charge changes. As %RTIL approached 100 %, there was insufficient THF to maintain coordination and the E° values were much more dependent upon the %RTIL. In the case of FeIII(P)(Cl), the shifts in the E° values were driven by the release of the chloride ion and its strong attraction to the ionic liquid environment. The spectroscopic properties and distribution of the FeII and FeI species into the RTIL nanodomains were monitored with visible spectroelectrochemistry, 19F NMR and EPR spectroscopy. This investigation shows that coordination and charge delocalization (metal versus ligand) in the metalloporphyrins redox products can be altered by the RTIL fraction in the solvent system, allowing an easy tuning of their chemical reactivity

Tetrabenzoporphyrin and -mono-, - Cis -di- and tetrabenzotriazaporphyrin derivatives: Electrochemical and spectroscopic implications of meso CH Group replacement with nitrogen

Nonperipherally hexyl-substituted metal-free tetrabenzoporphyrin (2H-TBP, 1a) tetrabenzomonoazaporphyrin (2H-TBMAP, 2a), tetrabenzo-cis-diazaporphyrin (2H-TBDAP, 3a), tetrabenzotriazaporphyrin (2H-TBTAP, 4a), and phthalocyanine (2H-Pc, 5a), as well as their copper complexes (1b-5b), were synthesized. As the number of meso nitrogen atoms increases from zero to four, Îmax of the Q-band absorption peak becomes red-shifted by almost 100 nm, and extinction coefficients increased at least threefold. Simultaneously the blue-shifted Soret (UV) band substantially decreased in intensity. These changes were related to the relative electron-density of each macrocycle expressed as the group electronegativity sum of all meso N and CH atom groups, âχR. X-ray photoelectron spectroscopy differentiated between the three different types of macrocyclic nitrogen atoms (the Ninner, (NH)inner, and Nmeso) in the metal-free complexes. Binding energies of the Nmeso and Ninner,Cu atoms in copper chelates could not be resolved. Copper insertion lowered especially the cathodic redox potentials, while all four observed redox processes occurred at larger potentials as the number of meso nitrogens increased. Computational chemical methods using density functional theory confirmed 1b to exhibit a Cu(II) reduction prior to ring-based reductions, while for 2b, Cu(II) reduction is the first reductive step only if the nonperipheral substituents are hydrogen. When they are methyl groups, it is the second reduction process; when they are ethyl, propyl, or hexyl, it becomes the third reductive process. Spectro-electrochemical measurements showed redox processes were associated with a substantial change in intensity of at least two main absorbances (the Q and Soret bands) in the UV spectra of these compounds

A One-Pot Synthesis of a 243-Allyl Dendrimer under Ambient Conditions

Hydrosilylation of a nonaallyl dendritic core using HSi(Me)2Cl followed by reaction with a phenolate dendronic brick bearing three allyl groups, followed by repetition of this sequence of reactions twice, allows a one-pot synthesis of a 243-allyl dendrimer under ambient conditions

Cross olefin metathesis for the selective functionalization, ferrocenylation, and solubilisation in water of olefin-terminated dendrimers, polymers, and gold nanoparticles and for a divergent dendrimer construction

Olefin cross metathesis was used to efficiently functionalize, polyolefin dendrimers, polymers, and gold nanoparticles using the second-generation Grubbs catalyst. In these structures, the tethers were lengthened to prevent the facile cross metathesis that otherwise predominates in polyolefin dendrimers having short tethers. This synthetic strategy allows the one-step access to polyacid, polyester, and polyferrocenyl structures from polyolefins. Cross metathesis is also used to efficiently achieve an iterative divergent dendritic construction. All the cross metathesis reactions were monitored by H-1 NMR showing the chemio-, regio-, and stereoselectivity. MALDI-TOF mass spectrometry was a very useful technique to confirm the efficiency of this synthetic strateg

Linguistic features employed to mark focus by a group of British speakers

Informe de Seminario para optar al grado de Licenciado en Lengua y Literatura Ingles

Cytotoxic and Proinflammatory Effects of Metal-Based Nanoparticles on THP‑1 Monocytes Characterized by Combined Proteomics Approaches

Thorough characterization of toxic effects of nanoparticles (NP) is desirable due to the increasing risk of potential environmental contamination by NP. In the current study, we combined three recently developed proteomics approaches to assess the effects of Au, CuO, and CdTe NP on the innate immune system. The human monocyte cell line THP-1 was employed as a model. The anticancer drugs camptothecin and doxorubicin were used as positive controls for cell death, and lipopolysaccharide was chosen as a positive control for proinflammatory activation. Despite equivalent overall toxicity effect (50 ± 10% dead cells), the three NP induced distinctly different proteomics signatures, with the strongest effect being induced by CdTe NP, followed by CuO and gold NP. The CdTe toxicity mechanism involves down-regulation of topoisomerases. The effect of CuO NP is most reminiscent of oxidative stress and involves up-regulation of proteins involved in heat response. The gold NP induced up-regulation of the inflammatory mediator, NF-κB, and its inhibitor TIPE2 was identified as a direct target of gold NP. Furthermore, gold NP triggered activation of NF-κB as evidenced by phosphorylation of the p65 subunit. Overall, the combined proteomics approach described here can be used to characterize the effects of NP on immune cells

Electron flow in large metallomacromolecules and electronic switching of nanoparticle stabilization: Click ferrocenyl dentromers that reduce AuIII to Au nanoparticles

Click ferrocenyl-terminal dentromers, a family of arene-cored dendrimers with triple branching (9-Fc, 27-Fc, 81-Fc, and 243-Fc), reduce AuIII to ferricinium dentromer-stabilized Au nanoparticles (AuNPs). Cyclic voltammetry studies in CH2Cl2 show reversible CV waves with some adsorption for the 243-Fc dentromer and the number of redox groups found, 255±25, by using the Bard–Anson method, is close to the theoretical number of 243. The dentromers reduce aqueous HAuCl4 to water-soluble ferricinium chloride dentromer-stabilized AuNPs with core sizes between 30 and 47 nm. These triazolylferricinium dentromer-stabilized AuNPs are reduced by cobaltocene to cobalticinium chloride and ferrocene dentromer weakly stabilized AuNPs together with a redshift of the AuNP plasmon. The weakness of the AuNP stabilization is characterized by dentromer extraction with CH2Cl2 along with irreversible AuNP agglomeration for the 9, 27, and 81-ferrocenyl dentromer, with only the 243-ferrocenyl dentromer-AuNP withstanding this process. Altogether, this demonstrates the electronic switching of the dentromer-mediated AuNP stabilization