Synthesis, structural studies and photochemistry of cobalt(III) complexes of anthracenylcyclam macrocycles

This work reports the syntheses, structures and some photochemistry in DMF of the cobalt complexes trans-[CoIII( 2)Cl2]Cl·0.5CH3OH and trans-[CoIII( 3)Cl2]Cl·4H2O, where 2 is 6-(anthracen-9-ylmethyl)-1,4,8,11-tetraazacyclotetradecane-5,7-dione and 3 is 6-(anthracen-9-ylmethyl)-1,4,8,11-tetraazacyclotetradecane. In the preparation of the macrocyclic ligand, 3, the formation of a polycyclic bis(aminal) intermediate and its subsequent acid hydrolysis to 3 is a cleaner route than the traditional procedure in which the analogous dioxocyclam 2 is reduced with borane reagents. The crystal structure of trans-[CoIII( 3)Cl2]Cl·4H2O shows that the macrocycle adopts the trans-III conformation, in which the anthracene moiety is extended away from the cobalt ion and the anthracene to Co separation is 7.22 . For the related complex trans-[CoIII( 2)Cl2]Cl·0.5CH3OH, however, the anthracene is bent over the highly conjugated tetracycle and significant interactions between the anthracene and the complex occur. A novel new complex, trans-[Co( 12)Cl2](where 12 is 5,7-hydroxy-6-oxo-1,4,8,11-tetraazacyclotetradecane-4,7-diene) which is a degradation product of the complex trans-[CoIII( 2)Cl2]Cl is also reported

Tandem chemiluminescence-flow injection analysis for dimethoate determination

This work was supported by the Ministry of Education and Science of Spain (Project CTM2006-11991) and FEDER funds.Catalá Icardo, M.; López Paz, JL.; Choves Barón, C. (2010). Tandem chemiluminescence-flow injection analysis for dimethoate determination. Luminescence. 25:235-236. https://doi.org/10.1002/bio.1217S2352362

Viewing scenes of the history of chemistry through the opera glass

Artistic creation has always reflected the spirit of the moment and opera has not been an exception. There are several examples of operas which appeared at key moments of the development of science, portraying them. Additionally there are also operas that emerged after scientific events or the lifetime of the scientists they were inspired on. In what concerns chemistry, the first category could be exemplified by the apothecary operas (already discussed by the author in a previous paper of this journal) while the others could be illustrated by recent operas such as Dr. Atomic or Madame Curie. Continuing our endeavor of establishing relations between opera and chemistry, and considering that history of science plays an important role in the process of teaching and learning sciences, some milestones of the history of chemistry are here revisited through the opera glass. The operas analyzed have been grouped in the following categories: Operas of Fire and Metallurgy, Operas of the Philosophers of Antiquity, Operas of Alchemy, Operas of the Age of Enlightenment, Operas of the Revolutions and Operas of Entropy.Thanks are due to the Foundation for Science and Technology (FCT–Portugal) and FEDER (European Fund for Regional Development)-COMPETE/QREN/EU for financial support through the research unity PEst-C/QUI/UI686/2013.

Speciation, Luminescence, and Alkaline Fluorescence Quenching of 4-(2-methylbutyl)aminodipicolinic acid (H2MEBADPA)

4-(2-Methylbutyl)aminodipicolinic acid (H2MEBADPA) has been synthesized and fully characterized in terms of aqueous phase protonation constants (pKa\u27s) and photophysical measurements. The pKa\u27s were determined by spectrophotometric titrations, utilizing a fully sealed titration system. Photophysical measurements consisted of room temperature fluorescence and frozen solution phosphorescence as well as quantum yield determinations at various pH, which showed that only fully deprotonated MEBADPA2– is appreciably emissive. The fluorescence of MEBADPA2– has been determined to be quenched by hydroxide and methoxide anions, most likely through base-catalyzed excited-state tautomerism or proton transfer. This quenching phenomenon has been quantitatively explored through steady-state and time-resolved fluorescence measurements. Utilizing the determined pKas and quenching constants, the fluorescent intensity of MEBADPA2– has been successfully modeled as a function of pH

An integrated assessment of the Good Environmental Status of Mediterranean Marine Protected Areas

Este artículo contiene 11 páginas, 2 figuras, 2 tablas.Local, regional and global targets have been set to halt marine biodiversity loss. Europe has set its own policy targets to achieve Good Environmental Status (GES) of marine ecosystems by implementing the Marine Strategy Framework Directive (MSFD) across member states. We combined an extensive dataset across five Mediterranean ecoregions including 26 Marine Protected Areas (MPAs), their reference unprotected areas, and a no-trawl case study. Our aim was to assess if MPAs reach GES, if their effects are local or can be detected at ecoregion level or up to a Mediterranean scale, and which are the ecosystem components driving GES achievement. This was undertaken by using the analytical tool NEAT (Nested Environmental status Assessment Tool), which allows an integrated assessment of the status of marine systems. We adopted an ecosystem approach by integrating data from several ecosystem components: the seagrass Posidonia oceanica, macroalgae, sea urchins and fish. Thresholds to define the GES were set by dedicated workshops and literature review. In the Western Mediterranean, most MPAs are in good/high status, with P. oceanica and fish driving this result within MPAs. However, GES is achieved only at a local level, and the Mediterranean Sea, as a whole, results in a moderate environmental status. Macroalgal forests are overall in bad condition, confirming their status at risk. The results are significantly affected by the assumption that discrete observations over small spatial scales are representative of the total extension investigated. This calls for large-scale, dedicated assessments to realistically detect environmental status changes under different conditions. Understanding MPAs effectiveness in reaching GES is crucial to assess their role as sentinel observatories of marine systems. MPAs and trawling bans can locally contribute to the attainment of GES and to the fulfillment of the MSFD objectives. Building confidence in setting thresholds between GES and non-GES, investing in long-term monitoring, increasing the spatial extent of sampling areas, rethinking and broadening the scope of complementary tools of protection (e.g., Natura 2000 Sites), are indicated as solutions to ameliorate the status of the basin.This article was undertaken within the COST Action 15121 MarCons (http://www.marcons-cost.eu, European Cooperation in Science and Technology), the Interreg MED AMAre Plus (Ref: 8022) and the project PO FEAMP 2014-2020 Innovazione, sviluppo e sostenibilita ` nel settore della pesca e dell’acquacoltura per la Regione Campania (ISSPA 2.51). M.C.U., A.B. have been funded by the project MEDREGION (European Commission DG ENV/MSFD, 2018 call, Grant Agreement 110661/ 2018/794286/SUB/ENV.C2). Aegean Sea data were retrieved from the project PROTOMEDEA (www.protomedea.eu), funded by DG for Marine Affairs and Fisheries of the EC, under Grant Agreement SI2.721917. JB acknowledges support from the Spanish Ministry of Science and Innovation (Juan de la Cierva fellowship FJC 2018-035566-I).With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S).Peer reviewe

Synthesis and prospective study of the use of thiophene thiosemicarbazones as signalling scaffolding for the recognition of anions

A family of phenyl-thiosemicarbazone dyes have been prepared and their interactions with anions monitorized via UV-Vis, fluorescence and 1H NMR titrations. Additionally quantum chemical calculations and electrochemical studies completed the studies carried out. The phenyl-thiosemicarbazone dyes show a modulation of their hydrogen-bonding and electron-donating capabilities as a function of the chemical groups attached and display two different chromo-fluorogenic responses towards anions in acetonitrile solutions. The more basic anions fluoride and cyanide are able to induce the dual coordination-deprotonation processes for all the receptors studied, whereas acetate only interacts with receptors 2, 3, 6, 7, 8, 9 and dihydrogen phosphate displays sensing features only with the more acidic receptors 6. Coordinative hydrogen bonding interactions is indicated by a small bathochromic shift, whilst deprotonation results in the appearance of a new band at ca. 400-450 nm corresponding to a colour change from colourless-yellow to yellow-red depending on the receptor. In the emission fluorescence, hydrogen bonding interaction is visible through the enhancement of the emission band, whereas deprotonation induced the growth of a new red-shifted emission. The chromo-fluorogenic behaviour could be explained on the basis of the deprotonation tendency of the binding sites and the proton affinity of the anions. PM3 and 1H NMR calculations are in agreement with the existence of the dual complexation-deprotonation process, whereas both studies are in discrepancy in relation to which is the proton involved in the deprotonation. Electrochemical studies carried with receptor 3 showed a quite complex redox behaviour and anodic shifts of the reduction peaks in the presence of the basic anions fluoride, cyanide and acetate.Fundação para a Ciência e a Tecnologia (FCT

A Microcalorimetric Determination of the Enthalpies of Formation in Solution of Nickel(II) Complexes with Tetraaza Macrocyclic Ligands of Varying Size

The heats of formation of Ni complexes with tetraaza macrocyclic ligands of varying ring size, (12-15 members) were detd. by destroying the complexes in aq. soln. with alk. cyanide. The octahedral-square-planar equil. were investigated, and the results are presented as ΔH° for both octahedral, blue and when possible, square-planar, yellow species. Like the Cu(II) system, the blue, octahedral series exhibits a max. in ΔH° with [14]aneN4. This is discussed in terms of the relative size of the ligand and the metal ion. The unexpected reversal of ΔH° for the 2 square-planar complexes is rationalized in terms of expected ligand transformations

Chelating properties of linear aliphatic tetraamines with some bivalent transition metal ions. 1,5,8,12-Tetraazadodecane (3,2,3-tet)

The basicity consts. of 1,5,8,12-tetraazadodecane (3,2,3-tet) were detd. potentiometrically in 0.5 M KNO3 at 25°. The equil. between 3,2,3-tet and Ni2+, Cu2+, and Zn ions were investigated under similar conditions. The basicity consts. of 3,2,3-tet are compared with those of other tetraamines. The order is related to the inductive effect of the constituent groups in the mol. Two complexes were found with both Ni(II) and Cu(II): the 1:1 complex [ML]2+ and a protonated species [MHL]3+. In addn. to these 2 complexes, Zn formed the hydroxo complex [ZnLOH]+ at high pH. It is shown that an alternating sequence of 5- and 6-membered rings increases complex stability

Thermochemical Consequences of Delocalization in Metal Biguanide Complexes

The thermodn. function ΔH° and ΔS° for the reaction of biguanide with Ni(II) and Cu(II) ions in 0.1 M KCl were detd. at 25°. The reaction is strongly exothermic with the formation of 1:2 metal-ligand complexes. The ligand stabilization due to π-delocalization and formation of metal-N bonds are both responsible for the high exothermic effect of the complex formation