Komplexe zwischen Eisen(II)- und Tartrat-Ion

The formation of complexes between iron(II) and tartrate ion (L) has been studied at 25° C in 1m-NaClO₄, by using a glass electrode. The e.m.f. data are explained with the following equilibria: $$\begin{gathered} Fe^{2 + } + L \rightleftarrows FeL log \beta _1 = 1,43 \pm 0,05 \hfill \\ Fe^{2 + } + 2L \rightleftarrows FeL_2 log \beta _2 = 2,50 \pm 0,05 \hfill \\\end{gathered} $$ The protonation constants of the tartaric acid have been determinated: $$\begin{gathered} H^ + + L \rightleftarrows HL logk_1 = 3,84 \pm 0,03 \hfill \\ 2H^ + + L \rightleftarrows H_2 L logk_2 = 6,43 \pm 0,02 \hfill \\\end{gathered}$$ .     

Enabling Racemization of Axially Chiral Subphthalocyanine-Tetracyanobutadiene-Aniline Enantiomers by Triplet State Photogeneration

In recent years, several tetracyanobuta-1,3-diene (TCBD) conjugates have been prepared by linking the tetracyano unit to various electroactive moieties. These push–pull conjugates, besides showing interesting physicochemical properties, are axially chiral, a feature arising from the restricted rotation around the central bond of the butadiene. Yet, only in a few cases, separation and isolation of the enantiomers have been successfully achieved, owing to the configurational lability of the corresponding enantiopure species. Herein, we report the first example of photo- and electroactive TCBD-based derivatives showing unprecedented configurational stability and a peculiar light-triggered enantiomer conversion mechanism enabled by triple-state photogeneration. These systems represent a nice addition to the fast-increasing arsenal of artificial, light-controllable molecular switches.     

Electrochemical Monitoring of the Early Events of Hydrogen Peroxide Production by Mitochondria

Mitochondria consume oxygen in the respiratory chain and convert redox energy into ATP. As a side process, they produce reactive oxygen species (ROS), whose physiological activities are still not understood. However, current analytical methods cannot be used to monitor mitochondrial ROS quantitatively and unambiguously. We have developed electrochemical biosensors based on peroxidase‐redox polymer‐modified electrodes, providing selective detection of H₂O₂ with nanomolar sensitivity, linear response over five concentration decades, and fast response time. The release of H₂O₂ by mitochondria was then monitored under phosphorylating or inhibited respiration conditions. We report the detection of two concomitant regimes of H₂O₂ release: large fluxes (hundreds of nM ) under complex III inhibition, and bursts of a few nM immediately following mitochondria activation. These unprecedented bursts of H₂O₂ are assigned to the role of mitochondria as the hub of redox signaling in cells.     

Synthesis and Investigation of Electro-Optical Properties of H-Shape Dibenzofulvene Derivatives

We have synthetized two classes of dibenzofulvene-arylamino derivatives with an H-shape design, for a total of six different molecules. The molecular structures consist of two D-A-D units connected by a thiophene or bitiophene bridge, using diarylamino substituents as donor groups anchored to the 2,7- (Group A) and 3,6- (Group B) positions of the dibenzofulvene backbone. The donor units and the thiophene or bithiophene bridges were used as chemico-structural tools to modulate electro-optical and morphological-electrical properties. A combination of experiments, such as absorption measurements (UV-Vis spectroscopy), cyclic voltammetry, ellipsometry, Raman, atomic force microscopy, TD-DFT calculation and hole-mobility measurements, were carried out on the synthesized small organic molecules to investigate the differences between the two classes and therefore understand the relevance of the molecular design of the various properties. We found that the anchoring position on dibenzofulvene plays a crucial key for fine-tuning the optical, structural, and morphological properties of molecules. In particular, molecules with substituents in 2,7 positions (Group A) showed a lower structural disorder, a larger molecular planarity, and a lower roughness.     

Panchromatic Fluorescence Emission from Thienosquaraines Dyes: White Light Electrofluorochromic Devices

Electrofluorochromic devices (EFCDs) that allow the modulation of the light emitted by electroactive fluorophores are very attractive in the research field of optoelectronics. Here, the electrofluorochromic behaviour of a series of squaraine dyes was studied for the first time. In solutions, all compounds are photoluminescent with maxima located in the range 665–690 nm, characterized by quantum yields ranging from 30% to 4.1%. Squaraines were incorporated in a polymer gel used as an active layer in all-in-one gel switchable EFCDs. An aggregation induced quenching occurs in the gel phase, causing a significant decrease in the emission quantum yield in the device. However, the squaraines containing the thieno groups (thienosquaraines, TSQs) show a panchromatic emission and their electrofluorochromism allows the tuning of the fluorescence intensity from 500 nm to the near infrared. Indeed, the application of a potential difference to the device induces a reversible quenching of their emission that is significantly higher and occurs at shorter switching times for TSQs-based devices compared to the reference squaraine dye (DIBSQ). Interestingly, the TSQs fluorescence spectral profile becomes more structured under voltage, and this could be explained by the shift of the aggregates/monomer equilibrium toward the monomeric species, due to electrochemical oxidation, which causes the disassembling of aggregates. This effect may be used to modulate the colour of the fluorescence light emitted by a device and paves the way for conceiving new electrofluorochromic materials based on this mechanism.     

A Study on Diflunisal: Solubility,Acid Constants and Complex Formation with Calcium(II) and Magnesium(II)

The properties of diflunisal, a widely used analgesic, were studied in physiologic solutions, 0.15 mol·dm^?3 NaCl. Solubility and protonation constants were determined and its behavior as ligand towards Ca(II) and Mg(II) was investigated. Solubility and protonation constants of diflunisal at 25 °C and 0.15 mol·dm^?3 were obtained from electromotive force measurements of galvanic cells using coulometric titrations. The experimental data yielded the solubility, s, of –log₁₀ s = 3.86 ± 0.02 and the protonation constants log₁₀ K ₁ = 11.98 ± 0.10 and log₁₀ K ₂ = 3.86 ± 0.03. Equilibria between diflunisal and Ca(II) and Mg(II) were investigated by means of electromotive force measurements and by comparing solubilities of diflunisal in the presence and absence of Ca(II) or Mg(II), respectively. Experimental data were explained by assuming the formation of 1:1 complexes for Ca(II) and Mg(II) along with evaluating the relative stability constants.     

Stonebrood and chalkbrood in Apis mellifera causing fungi: in vitro sensitivity to some essential oils

Aim of the present study was to evaluate the in vitro antimycotic activity of 17 chemically defined essential oils (EOs) both alone and as a mixture, against agents responsible for stonebrood caused by Aspergillus flavus, and chalkbrood caused by Ascosphaera apis in European honeybees. Cinnamomum zeylanicum yielded the lowest MIC value against A. flavus, but was not effective against A. apis, while Litsea cubeba and Pelargonium graveolens appeared to be effective against all checked fungi. Aspergillus niger showed the lower sensitivity. Two mixtures composed by L. cubeba, C. zeylanicum and Cymbopogon flexuosus (M1) and by L. cubeba, C. zeylanicum, P. graveolens and C. flexuosus (M2), respectively, were tested, both resulting effective. The components of M1 showed a synergistic effect. The use of mixtures allowed to decrease the total amount of EOs. The use of these products could be of interest for an alternative natural approach in honeybee disease management.     

Intense Ground‐State Charge‐Transfer Interactions in Low‐Bandgap,Panchromatic Phthalocyanine–Tetracyanobuta‐1,3‐diene Conjugates

A cycloaddition–retroelectrocyclization reaction between tetracyanoethylene and two zinc phthalocyanines (Zn^IIPcs) bearing one or four anilino‐substituted alkynes has been used to install a strong, electron‐accepting tetracyanobuta‐1,3‐diene (TCBD) between the electron‐rich Zn^IIPc and aniline moieties. A combination of photophysical, electrochemical, and spectroelectrochemical investigations with the Zn^IIPc‐TCBD‐aniline conjugates, which present panchromatic absorptions in the visible region extending all the way to the near infrared, show that the formal replacement of the triple bond by TCBD has a dramatic effect on their ground‐ and excited‐state features. In particular, the formation of extremely intense, ground‐state charge‐transfer interactions between Zn^IIPc and the electron‐accepting TCBD were observed, something unprecedented not only in Pc chemistry but also in TCBD‐based porphyrinoid systems.