One electron oxidation of triferrocenylmethanol: Synthesis, metal atom dynamics, electron delocalization, and the crystal structure of [Fc 3COH]+ PF6 -

The title compound 2 was prepared and its crystal structure was determined at 100 K. The neat solid was examined by temperature dependent 57Fe Mössbauer effect (ME) spectroscopy over the interval 92 < T < 318 K, and evidences two diamagnetic Fe(II) sites and one paramagnetic Fe(III) site. The latter shows spin–lattice relaxation, but there is no evidence of electron delocalization among the three iron sites in the above temperature interval. The mean-square-amplitude-of-vibration of the diamagnetic iron site has been determined from the recoil-free fraction ME resonance, and compared to the neutral Fc3COH homologue (1). The ME dynamical data are in good agreement with the Ui,j value at 100 K extracted from the crystallographic results. The ME parameters at 5 K have also been determined with the sample compound embedded in a paraffin wax matrix as well as pelletized with BN

Structural Chemistry of Copper(I) and Silver(I) Complexes with Triisopropylphosphane Sulfide, Selenide and Telluride Ligands

Phosphanchalkogenide sind von Bedeutung für die Koordination von Schwermetallen und den Aufbau und Abbau von Metallchalchogenid-Clustern (z. B. Fenske-Clustern), deren Eigenschaften zurzeit viel Beachtung finden. Hinsichtlich des Pearson-Konzeptes der harten und weichen Säuren und Basen, sollten Phosphantelluride (R3P=Te) ausgezeichnete Liganden gegenüber “weichen” Schwermetallkationen sein. Trotzdem sind sehr wenige Komplexe mit Phosphantellurid-Liganden in der Literatur bekannt. Zum Studium der Eingeschaften von Trialkylphosphantelluriden gegenüber Münzmetallen in der Lösung und im Festkörper wurden die Komplexe von Triisopropylphosphanchalkogeniden mit Kupfer(I), Silber(I) und Gold(I) untersucht. R3PTe-Cu(I) und R3PTe-Au(I) Komplexe (R=Me, iPr, tBu) wurden nur als intermediäre Spezies beobachtet, während die Silber(I)-Komplexe eine größere Stabilität mit zunehmenden Donoreigenschaften der R-Gruppe und abhängig von Natur des Anions aufweisen. Mit sehr schwach Nukleophilen (SbF6-Anion) bilden sich ionische und /oder supramolekulare Strukturen, während mit zunehmender Nukleophilie molekulare Strukturen erhalten wurden. Die besseren Donoreigenschaften von Tellur verglichen mit Schwefel oder Selen sind sehr gut in Komplexen mit Silber(I)-halogeniden zu beobachten. Der iPr3PTeAgI-Komplex zeigt in der Festkörperstruktur eine Tellur-Verbrückte Struktur, während iPr3PSAgCl-Komplex eine Chlor-Verbrückte Struktur mit terminalen Phosphansulfidliganden besitzt.With regard to the Pearson concept of hard and soft acids and bases, phosphane tellurides (R3P=Te) should be excellent ligands towards “soft” heavy metal cations. Their role as sources of phosphanes and of elemental tellurium allows them to contribute to the formation and decomposition of metal telluride clusters (like Fenske-typ coinage metal chalcogenide clusters), still R3P=Te complexes are extremely rare. To study the particular properties of the trialkylphosphane telluride ligands towards coinage metals in solution and in solid state, the coordination chemistry of triisopropylphosphane chalcogenides (iPr3PS, iPr3PSe and iPr3PTe) with silver(I), copper(I) and gold(I) salts was investigated. R3PTe-Cu(I) and Au(I) complexes (R = tBu, iPr, Me) are only transient species in solution, whereas in Ag(I) case, the basicity of R groups and the nature of the anion have an important role. The stability of complexes increases with increasing of R group branching. Less nucleophilic anions (SbF6 anion) led to the formation of ionic and/or supramolecular structures, while with increasing of anions nucleophilicity ([N(SO2CH3)2] or halides anions) molecular structures are obtained. The better donor proprieties of tellurium towards sulphur or selenium can be observed in the case of complexes with silver(I) halides. In the case of complex with phosphane telluride ligand iPr3PTeAgI a tellurium-bridge structure was obtain, while the complex iPr3PSAgCl shows in solid state a chlor-bridge structure with terminal phosphane sulphide ligands

Regio- and Stereoselective 1,2-Carboboration of Ynamides with Aryldichloroboranes.

AbstractCatalyst‐free 1,2‐carboboration of ynamides is presented. Readily available aryldichloroboranes react with alkyl‐ or aryl‐substituted ynamides in high yields with complete regio‐ and stereoselectivity to valuable β‐boryl‐β‐alkyl/aryl α‐aryl substituted enamides which belong to the class of trisubstituted alkenylboronates. The 1,2‐carboboration reaction is experimentally easy to conduct, shows high functional group tolerance and broad substrate scope. Gram‐scale reactions and diverse synthetic transformations convincingly demonstrate the synthetic potential of this method. The reaction can also be used to access 1‐boraphenalenes, a class of boron‐doped polycyclic aromatic hydrocarbons

The Effect of Regioisomerism on the TADF Properties of Organic Dyes

The properties of thermally activated delayed fluorescence (TADF) chromophores are highly dependent on the molecular design. The choice of the donor (D) and acceptor (A) group are as important as the choice of the π-linker and the substitution positions. Herein, the influence of regioisomerism through the substitution pattern of 9,9’-spirobi[fluorene] (SBF) on the TADF characteristics is investigated. In our studies, phenothiazine and carbonitrile have been chosen as D and A groups, and their substitution varied among the 2, 2’, 7 and 7’ positions of the spiro core resulting in two pairs of regioisomers. Depending on these changes, the physical properties differ from one to another with changes in emission wavelength maximum, photoluminescence quantum yield (PLQY), fluorescence lifetime and thermal stability. Three of the investigated molecules exhibit TADF properties in solid phase as thin films and crystals

Exploring substituent effects in reversible photoswitchable low molecular weight arylazoisoxazole adhesives

The design of reusable responsive materials is of utmost importance to reduce the unsustainable use of valuable resources. Inspired by our initial work on the application of arylazoisoxazoles (AIZ) as reusable photoresponsive adhesives, we aim to uncover generalizations to their adhesive properties and optimize their molecular design. To achieve this goal, a molecular library of AIZ with different substitution patterns has been synthesized and examined for their adhesive properties. Several of the photoreversible low molecular weight adhesives in the library exhibited significantly enhanced (&gt; 500%) weight-bearing capacities. This study broadens the understanding of AIZ as photoresponsive adhesives, shedding light on their limitations and the opportunities to improve their performance alike.</p

Direct Light-Enabled Access to α-Boryl Radicals: Application in the Stereodivergent Synthesis of Allyl Boronic Esters

Operationally simple strategies to assemble boron containing organic frameworks are highly enabling in organic synthesis. While conventional retrosynthetic logic has engendered many platforms focusing on the direct formation of C−B bonds, α-boryl radicals have recently reemerged as versatile open-shell alternatives to access organoborons via adjacent C−C bond formation. Direct light-enabled α-activation is currently contingent on photo- or transition metal-catalysis activation to efficiently generate radical species. Here, we disclose a facile activation of α-halo boronic esters using only visible light and a simple Lewis base to enable homolytic scission. Intermolecular addition to styrenes facilitates the rapid construction of highly versatile E-allylic boronic esters. The simplicity of activation permits the strategic merger of this construct with selective energy transfer catalysis to enable the complimentary stereodivergent synthesis of Z-allylic boronic esters

Energy Transfer (EnT) Catalysis of Non‐Symmetrical Borylated Dienes: Origin of Reaction Selectivity in Competing EnT Processes

Energy transfer catalysis (EnT) has had a profound impact on contemporary organic synthesis enabling the construction of higher in energy, complex molecules, via efficient access to the triplet excited state. Despite this, intermolecular reactivity, and the unique possibility to access several reaction pathways via a central triplet diradical has rendered control over reaction outcomes, an intractable challenge. Extended chromophores such as non‐symmetrical dienes have the potential to undergo [2+2] cycloaddition, [4+2] cycloaddition or geometric isomerisation, which, in combination with other mechanistic considerations (site‐ and regioselectivity), results in chemical reactions that are challenging to regulate. Herein, we utilise boron as a tool to probe reactivity of non‐symmetrical dienes under EnT catalysis, paying particular attention to the impact of boron hybridisation effects on the target reactivity. Through this, a highly site‐ and regioselective [2+2] cycloaddition was realised with the employed boron motif effecting reaction efficiency. Subtle modifications to the core scaffold enabled a [4+2] cycloaddition, while a counterintuitive regiodivergence was observed in geometric isomerisation versus [2+2] cycloaddition. The observed reactivity was validated via a mechanistic investigation, determining the origin of regiodivergence and reaction selectivity in competing EnT processes

Synthesis and Characterization of Poly-NHC-Derived Silver(I) Assemblies and Their Transformation into Poly-Imidazolium Macrocycles

Part of the “RSEQ-GEQO Prize Winners” Special CollectionThree metallosupramolecular assemblies composed of two bis-NHCs and two silver atoms, [4](PF6)2, two tetra-NHCs and foursilver atoms, [7](PF6)4, and two tri-NHCs and three silver atoms[8](BF4)3, have been prepared. Assemblies [4](PF6)2and [7](PF6)4feature NHC ligands decorated with terminal olefin groups.Irradiation of [4](PF6)2yielded complex [5](PF6)2with twoterminal cyclobutane rings linking the two bis-NHC ligands.Liberation of the macrocyclic tetrakisimidazolium salt H4-6(PF6)4was achieved by reaction of [5](PF6)2with NH4Cl/NH4PF6. No [2+2] cycloaddition was observed upon irradiation of [7](PF6)4,apparently due to an unfavorable orientation of the olefingroups. Irradiation of complex [8](BF4)3with three internal pairsof olefin groups leads to [9](BF4)3as a mixture of two isomersthat differ on the relative orientation of the internal cyclobutanerings. Reaction of [9](BF4)3with NH4Cl/NH4BF4yields an isomermixture of the novel cage-line hexakisimidazolium salt H6-10(BF4)6Three poly-imidazolium salts with appended olefins were obtained. Subsequent reaction with Ag2O enabled the preparation of the related poly-NHC-derived silver assemblies, which, depending on the relative orientation of the pendant olefins, underwent [2+2] cyclization of the olefins upon irradiation. The macrocyclic poly-imidazolium salts can be achieved by de-metallation using NH4Cl.Funding for open access charge: CRUE-Universitat Jaume

Toward a Neutral Single-Component Amidinate Iodide Aluminum Catalyst for the CO₂ Fixation into Cyclic Carbonates

A new iodide aluminum complex ({AlI(κ⁴-naphbam)}, 3) supported by a tetradentate amidinate ligand derived from a naphthalene-1,8-bisamidine precursor (naphbamH, 1) was obtained in quantitative yield via reaction of the corresponding methyl aluminum complex ({AlMe(κ⁴-naphbam)}, 2) with 1 equiv of I₂ in CH₂Cl₂ at room temperature. Complexes 2 and 3 were tested and found to be active as catalysts for the cyclic carbonate formation from epoxides at 80 °C and 1 bar of CO₂ pressure. A first series of experiments were carried out with 1.5 mol % of the alkyl complex 2 and 1.5 mol % of tetrabutylammonium iodide (TBAI) as a cocatalyst; subsequently, the reactions were carried out with 1.5 mol % of iodide complex 3 as a single-component catalyst. Compound 3 is one of the first examples of a nonzwitterionic halide single-component aluminum catalyst producing cyclic carbonates. The full catalytic cycle with characterization of all minima and transition states was characterized by quantum chemistry calculations (QCCs) using density functional theory. QCCs on the reaction mechanism support a reaction pathway based on the exchange of the iodine contained in the catalyst by 1 equiv of epoxide, with subsequent attack of I⁻ to the epoxide moiety producing the ring opening of the epoxide. QCCs triggered new insights for the design of more active halide catalysts in future explorations of the field