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Metal complexes of corrole
No full textThe coordination chemistry of corrole is one of the most intriguing aspects of this contracted porphyri- noid, for both theoretical and practical reasons. Corrole, in fact, shows a remarkable coordinative versa- tility, and several elements have been coordinated in formally high oxidation states, because of its trianionic character as ligand and the high electron density. These features, however, prompt corrole to show a non innocent ligand character, making difficult to elucidate the electronic structure of the corresponding complexes. These characteristics make corrole complexes of interest for a wide range of application fields, going from catalysis to chemical sensors. The important progresses in the synthetic pathways of this macrocycle have also been an important factor to widen the ‘‘periodic table” of metallocorroles, which is now large as much as that of the corresponding metalloporphyrins. All these features make corrole one of the most popular macrocycle in the porphyrinoids field. This is confirmed by the impressive number of the published articles related to metal complexes of corrole in the 2016–2018 period, which is the focus of this review
Fast Optical Sensing of Metals: A Case Study of Cu2+ Assessment in Soils
No full textIn this paper we report an application of a novel porphyrin ligand, Zn(II)TPP-BPI-crown (ZnPC), functionalized with two dibenzo-crown-ether moieties as cation-sensitive ionophore. The test on the optical response of ZnPC ligand inside PVC-based polymeric membranes towards different cations (Na+, K+, Li+, Ca2+, Mg2+, Co2+, Cd2+, Pb2+, Zn2+, Cu2+ and NH4+) were performed. The influence of the lipophilic site functionalization on the ZnPC optode response was investigated. The visibly (naked eye) observed color change of sensing material from green to red demonstrated the suitability of the ZnPC-based optodes to perform fast monitoring of Cu(II) ions in the concentration range between 6.6 × 10-7 and 2.4 × 10-2 mol l-1, with a low detection limit (estimated by s/n = 3 method) of 0.03 mg l-1, which is lower than WHO guideline value of 2 mg l-1 for natural waters. The membranes with the best composition were deposited onto paper support and employed for the express analysis of copper(II) ion in aqueous soil extracts. The results obtained were in a good agreement with a standard ASS method, thus suggesting the utility of developed sensors for aims of express environmental monitoring
Porphyrinoid thin films for chemical sensing
No full textThin film deposition of porphyrinoids is a critical step for the development of reliable chemical sensors. The binding properties, in liquid phase, of these compounds should be in fact preserved as much as possible in the solid state, to allow an efficient recognition of target analytes. However, the solid-state arrangements of these macrocycles could offer additional binding mechanisms that exceed those possible to the single molecules allowing to even enhance the superb binding versatility of porphyrinoids. In this manuscript, we have reviewed mostly our approach for the thin film deposition of porphyrinoids, going from the simple, noncontrolled techniques to the preparation of composite inorganic/organic materials. All these opportunities drive the aggregation of porphyrinoids by supramolecular interactions and the possibility to merge their properties with those of inorganic materials open the way to an almost unlimited possibility to prepare optimized sensing layers
Energy transfer and excitation processes in thin films of rare-earth organic complexes for NIR emission
No full textWe have synthesized and studied the excitation-emission properties of three erbium-coordinating porphyrin-based complexes for solid state films with emission in the 1530-nm band. In two of these complexes the C-H groups of the organic part (ligand) have been substituted with C-F and/or C-Br ones in order to assess the role of the deactivation by the vibronic levels in the strong quenching of NIR emission. Time-resolved phosphorescence measurements have also been carried out in gadolinium analogues to verify the influence of substitution on the singlet-triplet intersystem crossing processes. The observed increase in the NIR emission is not consistent with the complete removal of quenching and the presence of other mechanisms for deactivation should be investigated
Demetalation of corrole complexes: an old dream turning into reality
No full textDifferent strategies for the demetalation of corrole complexes have been developed, using copper complexes of corrole as model compounds.,Best results were obtained using the acidic mixture CHCl3/H2SO,, which allowed the almost complete removal of copper ions from both mesotriaryl-, beta-octaalkyl- and fully substituted corroles. This route reduced both the decomposition of the starting complex and the formation of isocorrole species produced by oxidation of the corrole ring in the acidic conditions necessary for the demetalation reaction. To investigate the scope of the reaction, the same approach was later extended to other metal complexes of corrole, such as cobalt, manganese, iron and germanium derivatives. Although not always successful, this approach demonstrated that in the case of corrole it is also possible to obtain a reversible coordination of metal ions, a route of synthetic interest for further functionalization of the corrole ring. Copyright (c) 2008 Society of Porphyrins & Phthalocyanines
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The self-aggregation of porphyrins with multiple chiral centers in organic/aqueous media: the case of sugar: the steroid-porphyrin conjugates
Full text linkAn overview of the solvent-driven aggregation of a series of chiral porphyrin derivatives studied by optical methods (uv/vis, fluorescence, cd and rls spectroscopies) is herein reported; the investigated porphyrins are characterized by the presence in the meso-positions of glycol-, steroidal- and glucosteroidal moieties, conferring amphiphilicity and solubility in aqueous media to the primarily hydrophobic porphyrin platform. Aggregation of the macrocycles is driven by a change in bulk solvent composition, forming architectures with supramolecular chirality, steered by the stereogenic centers on the porphyrin peripheral positions. The aggregation behavior and chiroptical properties of the final aggregated species strongly depend on the number and stereogenicity of the ancillary groups that dictate the mutual spatial arrangement of the porphyrin chromophores and their further organization in larger structures, usually detectable by different microscopies, such as AFM and SEM. Kinetic studies are fundamental to understand the aggregation mechanism, which is frequently found to be dependent on the substrate concentration. Additionally, Molecular Mechanics calculations can give insights into the intimate nature of the driving forces governing the self-assembly process. The critical use of these combined methods can shed light on the overall self-assembly process of chirally-functionalized macrocycles, with important implications on the development of chiral porphyrin-based materials
Electrochemistry and spectroelectrochemistry of b-pyrazino-fused tetraarylporphyrins in nonaqueous media
No full textBis-porphyrins containing a b,b′-fused pyrazino (Pz) linking group were examined by
electrochemistry and thin-layer UV-visible spectroelectrochemistry in PhCN containing 0.1 M tetran-butylammonium perchlorate (TBAP) as supporting electrolyte. The investigated compounds are represented as M(TPP)-Pz-(TPP)M, where TPP is the dianion of tetraphenylporphyrin and M = Zn(II),
Cu(II) or Ag(II). The effect of the linking Pz group on the redox potentials and UV-visible spectra
of the neutral, electroreduced and electrooxidized bis-porphyrins is discussed and the data compared to what is observed for related monoporphyrins and earlier characterized bis-porphyrins containing a tetraazaanthracene (TA) linking group and the same central metal ions. The Cu(II) and Zn(II) Pz linked
bis-porphyrins exhibit a relatively strong interaction between the two equivalent porphyrin macrocycles as evidenced by UV-visible spectra of the neutral compounds and characteristic splitting of redox processes for three of the four electron transfer reactions, the one exception being the first oxidation, where no splitting of potentials is observed in the formation of the bisporphyrin bis-cation radical,
[M(TPP)-Pz-(TPP)M]2+. The first oxidation and first reduction of the bis-porphyrin with two Ag(II)
central metal ions occurs via two overlapping one-electron transfer steps in each process indicating equivalent, but non-interacting redox centers. This difference in redox behavior is due to differences in the site of electron transfer, metal centered for the Ag(II) bisporphyrins, which undergo Ag(II)/Ag(III) and Ag(II)/Ag(I) processes as compared to only ring centered electron transfers for the Cu(II) and Zn(II) derivatives. The Pz-linked Zn(II) bis-porphyrins have a larger average HOMO–LUMO gap (2.01 V) as
compared to related tetraazaanthracene linked bis-porphyrins (1.67 V), which were earlier characterized in the literature, but the gap is smaller than that for the mono-porphyrins with the same central metal ions (2.17 V). Each redox reaction of the investigated bisporphyrins was characterized by thin-layer spectroelectrochemistry
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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