27 research outputs found
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 Cp<sub>2</sub>TiCl<sub>2</sub> Reduction and Structural Characterization of Resulting Compounds
The aim of the current study was
to examine the effects of group 13 metals on Cp<sub>2</sub>TiCl<sub>2</sub> reduction in the presence of 2-methoxyethanol (MeOEtOH)
or ethanol (EtOH) and the compositions of the resulting products.
Direct reaction of Cp<sub>2</sub>TiCl<sub>2</sub> and M [Al, Al (Fe
contaminated), Ga, In] in toluene/alcohol for 2 h gave a new
family of uncommon homo- and heterometallic compounds: [Cp<sub>2</sub>Ti<sub>2</sub>Al(μ,η<sup>2</sup>-OEtOMe)<sub>4</sub>Cl<sub>2</sub>][Ti<sub>2</sub>(μ,η<sup>2</sup>-OEtOMe)<sub>3</sub>(η<sup>2</sup>-OEtOMe)<sub>2</sub>Cl<sub>4</sub>] (<b>1</b>), [Cp<sub>2</sub>Ti<sub>2</sub>Al(μ,η<sup>2</sup>-OEtOMe)<sub>4</sub>Cl<sub>2</sub>]Cl (<b>2</b>), [Cp<sub>2</sub>Ti<sub>2</sub>Al(μ,η<sup>2</sup>-OEtOMe)<sub>4</sub>Cl<sub>2</sub>][Cp<sub>2</sub>Ti(η<sup>2</sup>-HOEtOMe)][FeCl<sub>4</sub>] (<b>3</b>), [Cp<sub>2</sub>Ti(η<sup>2</sup>-HOEtOMe)][Ga<sub>2</sub>Cl<sub>6</sub>]<sub>0.25</sub>[Cl]<sub>0.5</sub> (<b>4</b>), [Cp<sub>3</sub>Ti<sub>2</sub>(μ-OEt)<sub>2</sub>(OEt)][GaCl<sub>4</sub>] (<b>5</b>), [CpTi(μ,η<sup>2</sup>-OEtOMe)Cl]<sub>2</sub> (<b>6</b>), and
[Cp<sub>3</sub>Ti<sub>2</sub>(μ,η<sup>2</sup>-OEtOMe)(μ-OEtOMe)Cl]
(<b>7</b>). The reaction with indium for 48 h resulted in isolation
of [TiIn<sub>2</sub>(μ,η<sup>2</sup>-OEtOMe)<sub>4</sub>(OEtOMe)<sub>2</sub>Cl<sub>4</sub>] (<b>8</b>), [In<sub>2</sub>(μ-OEtOMe)<sub>2</sub>(HOEtOMe)<sub>4</sub>Cl<sub>4</sub>]<sub>2</sub> (<b>9</b>), and [Ti(OEtOMe)<sub>4</sub>] (<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 Cp<sub>2</sub>TiCl<sub>2</sub> opens up a previously
unexplored path that may provide access to novel and unique compounds
Impact of Group 13 Metals on Cp<sub>2</sub>TiCl<sub>2</sub> Reduction and Structural Characterization of Resulting Compounds
The aim of the current study was
to examine the effects of group 13 metals on Cp<sub>2</sub>TiCl<sub>2</sub> reduction in the presence of 2-methoxyethanol (MeOEtOH)
or ethanol (EtOH) and the compositions of the resulting products.
Direct reaction of Cp<sub>2</sub>TiCl<sub>2</sub> and M [Al, Al (Fe
contaminated), Ga, In] in toluene/alcohol for 2 h gave a new
family of uncommon homo- and heterometallic compounds: [Cp<sub>2</sub>Ti<sub>2</sub>Al(μ,η<sup>2</sup>-OEtOMe)<sub>4</sub>Cl<sub>2</sub>][Ti<sub>2</sub>(μ,η<sup>2</sup>-OEtOMe)<sub>3</sub>(η<sup>2</sup>-OEtOMe)<sub>2</sub>Cl<sub>4</sub>] (<b>1</b>), [Cp<sub>2</sub>Ti<sub>2</sub>Al(μ,η<sup>2</sup>-OEtOMe)<sub>4</sub>Cl<sub>2</sub>]Cl (<b>2</b>), [Cp<sub>2</sub>Ti<sub>2</sub>Al(μ,η<sup>2</sup>-OEtOMe)<sub>4</sub>Cl<sub>2</sub>][Cp<sub>2</sub>Ti(η<sup>2</sup>-HOEtOMe)][FeCl<sub>4</sub>] (<b>3</b>), [Cp<sub>2</sub>Ti(η<sup>2</sup>-HOEtOMe)][Ga<sub>2</sub>Cl<sub>6</sub>]<sub>0.25</sub>[Cl]<sub>0.5</sub> (<b>4</b>), [Cp<sub>3</sub>Ti<sub>2</sub>(μ-OEt)<sub>2</sub>(OEt)][GaCl<sub>4</sub>] (<b>5</b>), [CpTi(μ,η<sup>2</sup>-OEtOMe)Cl]<sub>2</sub> (<b>6</b>), and
[Cp<sub>3</sub>Ti<sub>2</sub>(μ,η<sup>2</sup>-OEtOMe)(μ-OEtOMe)Cl]
(<b>7</b>). The reaction with indium for 48 h resulted in isolation
of [TiIn<sub>2</sub>(μ,η<sup>2</sup>-OEtOMe)<sub>4</sub>(OEtOMe)<sub>2</sub>Cl<sub>4</sub>] (<b>8</b>), [In<sub>2</sub>(μ-OEtOMe)<sub>2</sub>(HOEtOMe)<sub>4</sub>Cl<sub>4</sub>]<sub>2</sub> (<b>9</b>), and [Ti(OEtOMe)<sub>4</sub>] (<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 Cp<sub>2</sub>TiCl<sub>2</sub> 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 SbCl<sub>5</sub>. 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 SbCl<sub>5</sub>. 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 V<sub>2</sub>O<sub>5</sub> in ethanol gave a new vanadium(V) complex, [VO<sub>2</sub>L] (<b>1</b>), while the similar reaction by using [V<sup>IV</sup>O(acac)<sub>2</sub>] as the metal source gave two different types of crystals related to compounds [VO<sub>2</sub>L] (<b>1</b>) and [V<sup>IV</sup>O(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 (H<sub>2</sub>O<sub>2</sub>) 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 M<sub>6</sub>(μ-O)<sub>12</sub> 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 Re<sub>6</sub>(μ-O)<sub>12</sub> unit. Our
synthetic strategy demonstrates a new approach to the syntheses of
polynuclear rhenium complexes under mild conditions. We discovered
that the [Re<sub>6</sub>(μ-O)<sub>12</sub>(3-Mepy)<sub>6</sub>]BPh<sub>4</sub> 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 [Re<sub>6</sub>(μ-O)<sub>12</sub>(3-Mepy)<sub>6</sub>]BPh<sub>4</sub> was performed successfully and almost quantitatively
resulting in the formation of the molecular [Re<sub>6</sub>(μ-O)<sub>12</sub>(3-Mepy)<sub>6</sub>] 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, <sup>1</sup>H, <sup>13</sup>C, and <sup>31</sup>P 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