Stereoselective Wittig Olefination as a Macrocyclization Tool. Synthesis of Large Carbazolophanes

<i>Z</i>-Selective Wittig olefination was applied to the synthesis of large carbazolophanes containing up to eight heteroaromatic subunits. A number of strategies were devised and tested, showing that cyclooligomerization yields can be significantly improved by using one-component schemes involving heterobifunctional reactants. [4]- and [6]­Carbazolophanes were characterized in the solid state, revealing compact, highly folded structures. Electronic and steric effects of substitution and chain length on the Wittig olefination rates and <i>Z</i>-selectivities were explored theoretically using DFT calculations

Impact of Group 13 Metals on Cp₂TiCl₂ Reduction and Structural Characterization of Resulting Compounds

The aim of the current study was to examine the effects of group 13 metals on Cp₂TiCl₂ reduction in the presence of 2-methoxy­ethanol (MeO­Et­OH) or ethanol (EtOH) and the compositions of the resulting products. Direct reaction of Cp₂TiCl₂ and M [Al, Al (Fe contaminated), Ga, In] in toluene/​alcohol for 2 h gave a new family of uncommon homo- and heterometallic compounds: [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]­[Ti₂­(μ,η²-OEt­OMe)₃­(η²-OEt­OMe)₂­Cl₄] (<b>1</b>), [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]Cl (<b>2</b>), [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]­[Cp₂Ti­(η²-HOEt­OMe)]­[FeCl₄] (<b>3</b>), [Cp₂Ti­(η²-HOEt­OMe)]­[Ga₂Cl₆]_0.25­[Cl]_0.5 (<b>4</b>), [Cp₃Ti₂­(μ-OEt)₂­(OEt)]­[GaCl₄] (<b>5</b>), [CpTi­(μ,η²-OEt­OMe)­Cl]₂ (<b>6</b>), and [Cp₃Ti₂­(μ,η²-OEt­OMe)­(μ-OEt­OMe)­Cl] (<b>7</b>). The reaction with indium for 48 h resulted in isolation of [TiIn₂­(μ,η²-OEt­OMe)₄­(OEt­OMe)₂­Cl₄] (<b>8</b>), [In₂­(μ-OEt­OMe)₂­(HOEt­OMe)₄­Cl₄]₂ (<b>9</b>), and [Ti­(OEt­OMe)₄] (<b>10</b>). The complexes were characterized using elemental analysis, IR and NMR spectroscopies, and, for <b>1</b>–<b>9</b>, single-crystal X-ray diffraction. The use of metallic gallium and indium to reduce Cp₂­TiCl₂ opens up a previously unexplored path that may provide access to novel and unique compounds

Impact of Group 13 Metals on Cp₂TiCl₂ Reduction and Structural Characterization of Resulting Compounds

The aim of the current study was to examine the effects of group 13 metals on Cp₂TiCl₂ reduction in the presence of 2-methoxy­ethanol (MeO­Et­OH) or ethanol (EtOH) and the compositions of the resulting products. Direct reaction of Cp₂TiCl₂ and M [Al, Al (Fe contaminated), Ga, In] in toluene/​alcohol for 2 h gave a new family of uncommon homo- and heterometallic compounds: [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]­[Ti₂­(μ,η²-OEt­OMe)₃­(η²-OEt­OMe)₂­Cl₄] (<b>1</b>), [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]Cl (<b>2</b>), [Cp₂­Ti₂Al­(μ,η²-OEt­OMe)₄­Cl₂]­[Cp₂Ti­(η²-HOEt­OMe)]­[FeCl₄] (<b>3</b>), [Cp₂Ti­(η²-HOEt­OMe)]­[Ga₂Cl₆]_0.25­[Cl]_0.5 (<b>4</b>), [Cp₃Ti₂­(μ-OEt)₂­(OEt)]­[GaCl₄] (<b>5</b>), [CpTi­(μ,η²-OEt­OMe)­Cl]₂ (<b>6</b>), and [Cp₃Ti₂­(μ,η²-OEt­OMe)­(μ-OEt­OMe)­Cl] (<b>7</b>). The reaction with indium for 48 h resulted in isolation of [TiIn₂­(μ,η²-OEt­OMe)₄­(OEt­OMe)₂­Cl₄] (<b>8</b>), [In₂­(μ-OEt­OMe)₂­(HOEt­OMe)₄­Cl₄]₂ (<b>9</b>), and [Ti­(OEt­OMe)₄] (<b>10</b>). The complexes were characterized using elemental analysis, IR and NMR spectroscopies, and, for <b>1</b>–<b>9</b>, single-crystal X-ray diffraction. The use of metallic gallium and indium to reduce Cp₂­TiCl₂ opens up a previously unexplored path that may provide access to novel and unique compounds

Expanded Hexapyrrolohexaazacoronenes. Near-Infrared Absorbing Chromophores with Interrupted Peripheral Conjugation

A family of azacoronenes containing up to two saturated bridges at the periphery was synthesized from substituted hexapyrrolylbenzenes using a two-step condensation–aromatization procedure. The introduction of peripheral bridges provides access to nonplanar, sterically crowded systems that display complex reactivity patterns, involving stereospecific aromatization of bridges and nucleophile additions. Despite the interrupted conjugation on the periphery, the new azacoronenes have easily accessible higher oxidation levels, and a quadruply charged species was chemically generated by reaction with SbCl₅. These oxidized species show extensive π-electron conjugation and are efficient UV–vis–NIR absorbers, active up to ca. 2400 nm. Interruption of peripheral conjugation is shown to induce a tendency toward biradicaloid electron configurations in doubly oxidized species

Expanded Hexapyrrolohexaazacoronenes. Near-Infrared Absorbing Chromophores with Interrupted Peripheral Conjugation

A family of azacoronenes containing up to two saturated bridges at the periphery was synthesized from substituted hexapyrrolylbenzenes using a two-step condensation–aromatization procedure. The introduction of peripheral bridges provides access to nonplanar, sterically crowded systems that display complex reactivity patterns, involving stereospecific aromatization of bridges and nucleophile additions. Despite the interrupted conjugation on the periphery, the new azacoronenes have easily accessible higher oxidation levels, and a quadruply charged species was chemically generated by reaction with SbCl₅. These oxidized species show extensive π-electron conjugation and are efficient UV–vis–NIR absorbers, active up to ca. 2400 nm. Interruption of peripheral conjugation is shown to induce a tendency toward biradicaloid electron configurations in doubly oxidized species

Bandgap Engineering in π‑Extended Pyrroles. A Modular Approach to Electron-Deficient Chromophores with Multi-Redox Activity

A family of bandgap-tunable pyrroles structurally related to rylene dyes was computationally designed and prepared using robust, easily scalable chemistry. These pyrroles show highly variable fluorescence properties and can be used as building blocks for the synthesis of electron-deficient oligopyrroles. The latter application is demonstrated through the development of π-extended porphyrins containing naphthalenediamide or naphthalenediimide units. These new macrocycles exhibit simultaneously tunable visible and near-IR absorptions, an ability to accept up to 8 electrons via electrochemical reduction, and high internal molecular free volumes. When chemically reduced under inert conditions, the most electron-deficient of these macrocycles revealed reversible formation of eight charged states, characterized by remarkably red-shifted optical absorptions, extending beyond 2200 nm. Such features make these oligopyrroles of interest as functional chromophores, charge-storage materials, and tectons for crystal engineering

Synthesis, structural characterization and catalytic potential of oxidovanadium(IV) and dioxidovanadium(V) complexes with thiazole-derived NNN-donor ligand

<p>Reaction between the tridentate NNN donor ligand, (<i>E</i>)-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)benzo[<i>d</i>]thiazole (HL), and V₂O₅ in ethanol gave a new vanadium(V) complex, [VO₂L] (<b>1</b>), while the similar reaction by using [V^IVO(acac)₂] as the metal source gave two different types of crystals related to compounds [VO₂L] (<b>1</b>) and [V^IVO(acac)L] (<b>2</b>). The molecular structures of the complexes were determined by single-crystal X-ray diffraction and spectroscopic characterization was carried out by means of FT-IR, UV–vis and NMR experiments as well as elemental analysis. The oxidovanadium(IV) and dioxidovanadium(V) species were used as catalyst precursors for olefin oxidation in the presence of hydrogen peroxide (H₂O₂) as an oxidant. Under similar experimental conditions, the presence of <b>1</b> resulted in higher oxidation conversion than <b>2</b>.</p

First Oxido-Bridged Cubo-Octahedral Hexanuclear Rhenium Clusters

The first discrete hexanuclear metal clusters with cores adopting the M₆(μ-O)₁₂ cubo-octahedral topology have been synthesized in the course of a simple one-pot reaction. We present a new class of rhenium clusters which are the first hexanuclear rhenium complexes with 12 bridging ligands and the first clusters with octahedrally arranged Re atoms bridged only by O atoms forming a unique cube-like Re₆(μ-O)₁₂ unit. Our synthetic strategy demonstrates a new approach to the syntheses of polynuclear rhenium complexes under mild conditions. We discovered that the [Re₆(μ-O)₁₂­(3-Mepy)₆]­BPh₄ cluster compound has the ability to undergo reversible or/and quasireversible redox reactions without changing spatial structure and overall geometry. Subsequently, a reduction reaction of [Re₆(μ-O)₁₂­(3-Mepy)₆]­BPh₄ was performed successfully and almost quantitatively resulting in the formation of the molecular [Re₆(μ-O)₁₂­(3-Mepy)₆] complex

Synthesis and X-ray single crystal structure analysis of a new 2-chlorobenzyl ammonium salt of phosphonic acid

<p></p> <p>An efficient synthesis of a new 2-chlorobenzyl ammonium salt of phosphonic acid from the reaction of diethyl phosphite with 2-chlorobenzyl amine is described at moderate temperature in catalyst- and solvent-free conditions. The structure of this phosphonic acid salt was confirmed by FT-IR, ¹H, ¹³C, and ³¹P NMR spectroscopy, and single crystal X-ray structure analysis.</p

Synthesis of Bis(phenanthropyrroles) via a Tandem Scholl Oxidation

An electron-rich 3,4-diarylpyrrole is shown to undergo a tandem inter- and intramolecular Scholl oxidation, providing access to bis­(phenanthropyrroles), a new class of bipyrrole derivatives with extended π conjugation. Intermolecular coupling of two pyrrole molecues is found to be the initial step of this reaction. Bis­(phenanthropyrroles) are characterized by restricted rotation around the α–α bond and exhibit strong blue fluorescence and large Stokes shifts