Acid–Base‐Controlled Stereoselective Metalation of Overhanging Carboxylic Acid Porphyrins: Consequences for the Formation of Heterobimetallic Complexes

Overhanging carboxylic acid porphyrins have revealed promising ditopic ligands offering a new entry in the field of supramolecular coordination chemistry of porphyrinoids. Notably, the adjunction of a so‐called hanging‐atop (HAT) Pb^II cation to regular Pb^II porphyrin complexes allowed a stereoselective incorporation of the N‐core bound cation, and an allosterically controlled Newton’s cradle‐like motion of the two Pb^II ions also emerged from such bimetallic complexes. In this contribution, we have extended this work to other ligands and metal ions, aiming at understanding the parameters that control the HAT Pb^II coordination. The nature of the N‐core bound metal ion (Zn^II, Cd^II), the influence of the deprotonation state of the overhanging COOH group and the presence of a neutral ligand on the opposite side (exogenous or intramolecular), have been examined through ¹H NMR spectroscopic experiments with the help of radiocrystallographic structures and DFT calculations. Single and bis‐strap ligands have been considered. They all incorporate a COOH group hung over the N‐core on one side. For the bis‐strap ligands, either an ester or an amide group has been introduced on the other side. In the presence of a base, the mononuclear Zn^II or Cd^II complexes incorporate the carbonyl of the overhanging carboxylate as apical ligand, decreasing its availability for the binding of a HAT Pb^II. An allosteric effector (e.g., 4‐dimethylaminopyridine (DMAP), in the case of a single‐strap ligand) or an intramolecular ligand (e.g., an amide group), strong enough to compete with the carbonyl of the hung COO^?, is required to switch the N‐core bound cation to the opposite side with concomitant release of the COO^?, thereby allowing HAT Pb^II complexation. In the absence of a base, Zn^II or Cd^II binds preferentially the carbonyl of the intramolecular ester or amide groups in apical position rather than that of the COOH. This better preorganization, with the overhanging COOH fully available, is responsible for a stronger binding of the HAT Pb^II. Thus, either allosteric or acid–base control is achieved through stereoselective metalation of Zn^II or Cd^II. In the latter case, according to the deprotonation state of the COOH group, the best electron‐donating ligand is located on one or the other side of the porphyrin (COO^?>CONHR>COOR>COOH): the lower affinity of COOH for Zn^II and Cd^II, the higher for a HAT Pb^II. These insights provide new opportunities for the elaboration of innovative bimetallic molecular switches.     

Physico-Chemical and Phytochemical Characterization of Moroccan Wild Jujube “Zizyphus lotus (L.)” Fruit Crude Extract and Fractions

Wild jujube “Ziziphus lotus (L.) Desf.” belongs to the Rhamnaceae family and is a traditionally herbaceous medicinal plant. It is very common in arid and semi-arid regions and is currently used for its antidiabetic, sedative, analgesic, anti-inflammatory and hypoglycemic activities. The aim of the present work was to characterize the physico-chemical properties and the phytochemical profile of wild jujube sample collected from the Guercif region, in order to determine the polyphenolic compounds and the antioxidant ability Analyses were carried out directly after the harvest for the determination of pH, refractive index, total soluble solid (°Brix), dry matter, sugar/acidity, total sugars, reducing sugars, as well as lipid and protein content. Results showed that the investigated fruit is acidic (pH 4.9 ± 0.23) and rich in sugars (80.2 g/100 g ± 3.81). The GC-MS analysis of the fruit revealed a number of volatile compounds, as many as 97, belonging to different chemical classes. The HPLC-DAD-ESI/MS analysis showed the presence of a total of 20 polyphenolic compounds in both EtOAc and MeOH-water extracts. Among them, p-Hydroxybenzoic acid was the most abundant in the EtOAc extract (185.68 µg/100 mg ± 0.5) whereas Quercetin 3-O-rhamnoside-7-O-glucoside was found in higher amounts in the MeOH-water extract (25.40 µg/100 mg ± 0.5). These components have medical interest, notably for human nutrition, as well as health benefits and therapeutic effects. Therefore, Moroccan jujube “Zizyphus lotus (L.)” fruit may have potential industrial applications for food formulations.     

Doubly inelastic collisions with relativistic heavy ions and target recoil momentum spectroscopy

We consider relativistic collisions of heavy hydrogenlike ions with hydrogen and helium atoms in which the ion-atom interaction causes both colliding particles to change their internal states. Concentrating on the study of the longitudinal momentum spectrum of the atomic recoil ions, we discuss the role of relativistic and higher order effects, predict a surprisingly strong influence of the projectile's electron on the momentum transfer, and show that the important information about the doubly inelastic collisions could be obtained in experiment merely by measuring the recoil momentum spectrum.     

Unprecedented incorporation of α-emitter radioisotope 213Bi into porphyrin chelates with reference to a daughter isotope mediated assistance mechanism

For the first time, α-emitter radioisotope (213)Bi has been incorporated into porphyrin chelates, with rates matching with the short period of the radionuclide. An in situ transmetalation mechanism involving the daughter isotope (209)Pb is expected to boost the (213)Bi radiolabeling process.     

Radiation field and resonant two-center dielectronic transitions in relativistic ion-atom collisions

We consider projectile-electron excitation and loss in relativistic collisions of ionic projectiles with excited atoms. We show that under certain conditions electron transitions in the ion and atom can be resonantly coupled in the collision via the radiation field. The resonance becomes possible due to the Doppler effect, has a well-defined impact energy threshold, and clearly manifests itself in the cross sections. Since the range of the ion-atom interaction in the resonance case is very long, the presence of other atoms in the target medium as well as the size of the space occupied by the medium have to be taken into account. As a result, the cross section may become dependent on the density of the target atoms and/or the target size.     

Translocation-coupled transmetalation at the origin of a dinuclear lead porphyrin complex: implication of a hanging-atop coordination mode

Translocation of a lead cation from the N-core of a porphyrin to a hanging carboxylate group is coupled to a transmetalation process with a second lead cation, leading to a dinuclear species. A novel hanging-atop coordination mode is responsible for the dynamic and stereocontrolled binding of lead to the porphyrin core.     

Synthesis and antibacterial activity of N-[2-(2-naphthyl)ethyl]piperazinyl quinolones

A series of N-[2-(2-naphthyl)ethyl]piperazinyl quinolones containing a carbonyl related functional groups (oxo- or oxyimino-) on the ethyl spacer was synthesized and evaluated for antibacterial activity. The synthesis of N-[2-(2-naphthyl)ethyl]piperazinyl quinolones was achieved through the versatile and efficient synthetic route that involved reaction of piperazinyl quinolones with appropriate α-bromoketone or α-bromooxime derivatives. The structures of new compounds were confirmed by elemental analysis, IR and NMR spectra. Antibacterial data indicated that some of the new N-[2-(2-naphthyl)ethyl]piperazinyl quinolones showed good antibacterial activity and modification of the position 8 and N-1 substituent on quinolone ring, and ethyl spacer functionality produced significant changes in activity against Gram-positive and Gram-negative bacteria.