Designing Powerful Biindole-Based Inherently Chiral Selectors: Enhancing Enantiodiscrimination by Core Functionalization with Additional Coordination Elements.

Among inherently chiral selectors of axial stereogenicity, usually resulting in very good enantiodiscrimination performances, the biindole-based family has the additional advantage of very easy functionalization of the two nitrogen atoms with a variety of substituents with desirable properties. Aiming to evaluate the possibility of exploiting such feature to enhance the enantiodiscrimination ability of the archetype structure, a series of three inherently chiral monomers were designed and synthesized, characterised by a 2,2'-biindole atropisomeric core conjugated to bithiophene wings enabling fast and regular electrooligomerization, and functionalised at the nitrogen atoms with an ethyl, a methoxyethyl, or a hydroxyethyl substituent. Nitrogen alkylation was also exploited to obtain for the first time the chemical resolution of the biindole selectors without employing chiral HPLC.

Coordination-triggered redox activity of early and late lanthanide calix[4]arene complexes.

The methylation of -butylcalix[4]arene in the distal 1,3-phenolic sites provides HL = {-butylcalix[4](OMe)(OH)arene}. This unit acts as a rigid coordinating ligand to early and late lanthanide metal ions, enabling the construction of two families of mononuclear compounds featuring (N(Bu))[LnL(acac)]·CHCN (Ln = Pr (1), Nd (2), Ho (3), and Er (4)) and (N(Bu))[LnL{MoO(OMe)(NO)}]·CHCl (Ln = Nd (5) and Er (6)). The metal ions adopt distorted bicapped trigonal prismatic coordination environments, resulting in slow relaxation of the magnetization for 4.

Propyl-phthalimide Cyclotricatechylene-Based Chemosensor for Sulfosulfuron Detection: Hybrid Computational and Experimental Approach.

The detection of trace amounts of sulfosulfuron, a pesticide of increasing importance, has become a pressing issue, prompting the development of effective chemosensors. In this study, we functionalized cyclotricatechylene (CTC) with propyl-phthalimide due to the presence of electronegative oxygen and nitrogen binding sites. Our optimized ligand displayed the highest docking score with sulfosulfuron, and experimental studies confirmed a significant fluorescence enhancement upon its interaction with sulfosulfuron.

Synthesis of Thiapillar[6]arenes Bearing Redox-Active (Hydro)quinone Groups. Electrochemical and XRD Study.

Pillar[]arenes are among the newest members of the macrocyclic family. Nevertheless, their conformational behavior and binding properties as well as redox properties of dealkylated pillar[]arenes are well-studied. At the same time, introducing a heteroatom into a cyclophane macrocycle is already known to alter all the above properties drastically.

Sulphonamidic Groups as Electron-Withdrawing Units in Ureido-Based Anion Receptors: Enhanced Anion Complexation versus Deprotonation.

A sulphonamidic moiety was utilized as an electron-withdrawing group for enhancement of anion complexation features of urea-based receptors. A series of receptors varying in acidity of sulphonamidic and urea NH groups was synthesized and thoroughly tested. The individual complexation properties reflect deprotonation/complexation equilibrium in a given molecule as a function of the substitution.

The Impact of Huge Structural Changes on Electron Transfer and Measurement of Redox Potentials: Reduction of -12-Carborane.

A massive structural change accompanies electron capture by the 1,2-dicarba--dodecaborane cage molecule (). Bimolecular electron transfer (ET) by pulse radiolysis found a reduction potential of = -1.92 V vs Fc for and rate constants that slowed greatly for ET to or from when the redox partner had a potential near this .

The cone-tetranitrocalix[4]arene tetraradical tetraanion as an electrochemically generated ligand for heavier alkali metal cations.

Four-electron electrochemical reduction of the cone-tetranitrocalix[4]arene in DMF results in the stable tetraradical tetraanion. The positive shift of the reduction potential of the title compound with an increasing concentration of alkali metal ions is caused by complex formation. The tetranitrocalix[4]arene thus represents an electrochemically generated ligand - a promising receptor/sensor - for alkali metal ions.

Role of pre-corrosion of Fe on its efficiency in remediation systems: An electrochemical study.

The duration of in-situ generation of iron corrosion products (FeCPs) prior the remediation process (so called "aging" of metallic iron (Fe)), was found as the key parameter affecting the efficiency of Fe for water remediation. Batch experiments were performed in buffered solutions (pH 4.0, 4.

Crystal structure of 2--butyl-2,3-di-hydro-1-benzo[]pyrrol-1-one.

The asymmetric unit of the title compound, CHNO, comprises two sym-metry-independent mol-ecules which differ mainly in the conformations of the -butyl groups. The mol-ecules contain an essentially planar five-membered 3-pyrroline ring incorporating a carbonyl substituent (pyrrolinone) which forms part of an isoindolinone skeleton. The planarity of the pyrrole ring is compared to other structures with isoindolinone.

Electrochemical Oxidation of [1-X-12-I-CBMe] Anions: Formation of Borenium Ylides [12-Dehydro-1-X-CBMe] and Iodonium Ylide Anions [{12-(1-X-CBMe)}I].

Cyclic voltammograms of 12-iodinated icosahedral carborane anions [1-X-12-I-CBMe] (X = H, CH, CH, CH, CH, CH, and COOCH) show two one-electron anodic oxidation peaks at the Pt electrode in liquid SO. Oddly, the first is irreversible and the second partially reversible. Mass spectrometry of the principal anionic product of preparative anodic oxidation of [1-H-12-I-CBMe], identical with the anionic product of its reaction with [EtSi-H-SiEt] and/or EtSi, allows it to be identified as the iodonium ylide anion [{12-(1-H-CBMe)}I].

Anodic Oxidation of 18 Halogenated and/or Methylated Derivatives of CBH.

Anodic oxidation of [CBH] and 18 of its halogenated and/or methylated derivatives was examined. Reversible oxidation was found for four of the anions in liquid SO and for four more in 1,1,1,3,3,3-hexafluoroisopropyl alcohol. The oxidation occurred at ∼1 V (for [CBMe]) up to more than 4 V (for [1-H-(2-6)-F-(7-12)-(CF)-CB]) relative to ferrocene/ferricinium.

A study of the planarity of the pyrrolone fragment in 2-isopropyl-2,3-dihydro-1H-isoindol-1-one.

Orthophthalaldehyde (o-phthalaldehyde, OPA) is an aromatic dialdehyde bearing two electron-withdrawing carbonyl groups. The reactions of OPA with primary amines are broadly applied for the synthesis of important heterocyclic compounds with biological relevance. A number of such reactions have been investigated recently and several structures of condensation products have been reported, however, the complex reaction mechanism is still not fully understood and comprises concurrent as well as consecutive reactions.

Covalent dimers of 1,3-diphenylisobenzofuran for singlet fission: synthesis and electrochemistry.

The synthesis of covalent dimers in which two 1,3-diphenylisobenzofuran units are connected through one phenyl substituent on each is reported. In three of the dimers, the subunits are linked directly, and in three others, they are linked via an alkane chain. A seventh new compound in which two 1,3-diphenylisobenzofuran units share a phenyl substituent is also described.

Electrochemical and quantum chemical investigation of tetranitrocalix[4]arenes: molecules with multiple redox centers.

The calix[4]arene skeleton is electrochemically inactive, but it is a useful stable frame for building "smart" molecules and supramolecular assemblies. Suitable substitution on the upper (and/or lower) rim leads to unusual and surprising properties in this system. Polynitrocalix[4]arenes with reducible nitro groups located at the upper rim represent molecules with multiple redox centers where the potential for interactions between them is the focus of interest.

Measured and calculated oxidation potentials of 1-X-12-Y-CB11Me10- anions.

Cyclic voltammetry of 31 icosahedral carborane anions 1-X-12-Y-CB(11)Me(10)(-) at a Pt electrode in liquid SO(2) revealed a completely reversible one-electron oxidation even at low scan rates, except for the anions with Y = I, which are oxidized irreversibly up to a scan rate of 5.0 V/s, and the anion with X = COOH and Y = H, whose oxidation is irreversible at scan rates below 1.0 V/s.

Imidazole as a donor/acceptor unit in charge-transfer chromophores with extended π-linkers.

Eleven new, stable, push-pull systems that feature 4,5-bis[4-(N,N-dimethylamino)phenyl]imidazole and 4,5-dicyanoimidazole as the donor and acceptor moieties and the systematically extended and varied π-linker were prepared and investigated. Evaluation of the measured UV/Vis spectra, electrochemical data (cyclic voltammetry (CV), rotating-disc voltammetry (RDV), and polarography) and calculated β and γ polarizabilities showed efficient charge transfer (CT) in biimidazole-type chromophores. Push-pull system 27, which features a planar thiophene-derived π-linker, was revealed to be the most efficient chromophore within the studied series.

New approaches to the characterization of carbon paste electrodes using the ohmic resistance effect and qualitative carbon paste indexes.

In this article, some new approaches to characterize the carbon paste mixtures and the respective carbon paste electrodes (CPEs) are presented, discussed, and critically evaluated. Particular attention has been paid to the changes of the ohmic resistance, relative to the dependence on composition of the CPE, the materials used, the time, and the position of storage. Four types of carbon pastes were examined, and for the interpretation of experimental data, a new simple model of "close-packing of spheres" has been applied.

2-(2-Hydroxy-ethyl)-3-[(2-hydroxy-ethyl)imino]isoindolin-1-one.

In the crystal structure of the title compound, C(12)H(14)N(2)O(3), mol-ecules are packed into layers parallel to (100). Each layer contains centrosymmetric dimers formed by a pair of strong O-H⋯N hydrogen bonds with an R(2) (2)(10) motif, while strong O-H⋯O hydrogen bonds forming C(10) chains connect mol-ecules into a two-dimensional network. Additional stabilization is supplied by weak C-H⋯O hydrogen bonds and weak π-π stacking inter-actions with centroid-centroid distances in the range 3.

4-Amino-3-methyl-6-phenyl-1,2,4-triazin-5(4H)-one (metamitron) and 4-amino-6-methyl-3-phenyl-1,2,4-triazin-5(4H)-one (isometamitron).

The title structures, both C(10)H(10)N(4)O, are substitutional isomers. The N-N bond lengths are longer and the C=N bond lengths are shorter by ca 0.025 A than the respective average values in the C=N-N=C group of asymmetric triazines; the assessed respective bond orders are 1.

Synthesis of the isolable biradicals *(CH3B)11C-C triple bond C-C(BCH3)11* and trans-*(CH3B)11C-CH=CH-C(BCH3)11*.

A synthesis of ethene and ethyne derivatives carrying the anionic -C(BCH3)11- substituent on one or both carbon atoms is described. Two-electron oxidation of the dianions yielded the stable and isolable electroneutral title biradicals.

Electroreduction of aromatic oximes: diprotonation, adsorption, imine formation, and substituent effects.

Aromatic oximes are reduced in aqueous solution in a four-electron process. The reducible species in the pH range 5-8 is a diprotonated form of the oxime. This species is generated in the course of electrolysis in the vicinity of the electrode surface from the adsorbed neutral form of the oxime.

An investigation into the initial degradation steps of four major dye chromophores: study of their one-electron oxidation and reduction by EPR, ENDOR, cyclic voltammetry, and theoretical calculations.

The degradation of dyes is frequently initiated by one-electron oxidation or reduction; however, relatively little is known about the initially formed radicals. Acid Green 25 (AG25), Crystal Violet (CVI), Methylene Blue (MB), and Acid Orange 7 (AO7), representing paradigms of four types of commercial organic dyes, were therefore investigated in terms of their redox behavior. Their redox potentials in MeCN and buffered aqueous solutions were determined by cyclic voltammetry.

Ferrocene-modified purines as potential electrochemical markers: synthesis, crystal structures, electrochemistry and cytostatic activity of (ferrocenylethynyl)- and (ferrocenylethyl)purines.

Palladium-catalyzed Sonogashira cross-coupling reactions of halopurines 9-benzyl-6-chloropurine (2 a), 9-benzyl-8-bromoadenine (2 b), and 9-benzyl-2-chloroadenine (2 c) with ethynylferrocene (1) gave the corresponding (ferrocenylethynyl)purines 3 a-c in moderate to good yields. Catalytic hydrogenation of these alkynes over Pd/C afforded the respective saturated [2-(ferrocenyl)ethyl]purines 4 a-c. The crystal structures 3 a, 3 b, 4 a and 4 b as determined by X-ray diffraction show interesting solid-state interactions, markedly different for purines 3 a and 4 a on one hand and adenines 3 b and 4 b that possess a free amino group on the other.