Reversible dimerization of decaniobate

Three different solvates of TBA₆[Nb₁₀O₂₈] (TBA = tetra-n-butylammonium) were structurally characterized. The results revealed that two water molecules are hydrogen-bonded to the terminal oxygens of the [Nb₁₀O₂₈]⁶⁻ anion in the same manner in all of the solvates. Decaniobate [Nb₁₀O₂₈]⁶⁻ dimerizes by the action of HCl to form icosaniobate [Nb₂₀O₅₄]⁸⁻, while icosaniobate breaks up into decaniobate [Nb₁₀O₂₈]⁶⁻ by the action of TBAOH. Decaniobate also dimerizes spontaneously to form icosaniobate [Nb₂₀O₅₄]⁸⁻ in CH₂Cl₂ even if no acid is added to the solution. The reaction was followed by IR spectroscopy, and the results suggested the reaction is second order with respect to the concentration of [Nb₁₀O₂₈]⁶⁻.     

Zwitterionic Corroles: Regioselective Nucleophilic Pyridination of a Doubly Linked Biscorrole

Pyridine attacks : Nucleophilic addition of pyridine derivatives to a doubly linked corrole, which is a stable singlet biradical species, occurs at the bay area with high regioselectivity to provide zwitterionic dimers (see picture; Ar=C₆F₅). Charge transfer between the anionic corrole and the pyridinium groups induces effective fluorescence quenching of the corrole dimer, which can be utilized for selective fluoride ion recognition.

     

Synthesis of Orthorhombic Mo‐V‐Sb Oxide Species by Assembly of Pentagonal Mo6O21 Polyoxometalate Building Blocks

Mix and match : The pentagonal [Mo₆O₂₁]^n? polyoxomolybdate building block assembles with other sources of Mo, V, and Sb ions to form an orthorhombic Mo‐V‐Sb oxide. The first single‐crystal X‐ray analysis of an orthorhombic Mo–V‐based oxide, a promising catalyst for light alkane selective oxidation known as the “M1 phase”, revealed the structure of the compound.

     

Synthesis and properties of oxygen‐, methylene‐, and alkylene‐bridged poly(dithiafulvene)s

Polymerization by cycloaddition between aldothioketene and its alkynethiol tautomer (derived in situ from a diyne) leading to the formation of dithiafulvene unit‐linked polymers has been studied. Two aromatic diynes [bis(4‐ethynyldiphenyl)methane ( 1a ) and 4,4′‐diethynyldiphenyl ether) ( 1b )] were used as starting materials with the aim of obtaining non‐π‐conjugated methylene‐ and oxygen‐bridged aromatic poly(dithiafulvene)s. The poly(dithiafulvene) derived from bis(4‐ethynyldiphenyl)methane can be considered as an interesting precursor to a small band‐gap polymer having alternating aromatic and quinonoid moieties. Further, two aliphatic diynes [1,7‐octadiyne ( 3a ) and 1,9‐decadiyne ( 3b )] were subjected to cycloaddition polymerization to obtain aliphatic poly(dithiafulvene)s containing localized electron‐rich dithiafulvene units. The polymers obtained were characterized by IR, ¹H NMR, gel permeation chromatography, and cyclic voltammetry. The electron‐donating property of the polymers was evident from the charge‐transfer (CT) complex formation with an electron acceptor 7,7,8,8‐teracyanoquinodimethane. The CT complexes were characterized by IR, ¹H NMR, and ultraviolet–visible spectroscopies. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3593–3603, 2001     

Synthesis of poly(cyclodiborazane)s by allylboration polymerization of dicyano compounds with trimethallylborane

Allylboration polymerization of α, ω-dicyanoalkanes with trimethallylborane produced the corresponding poly(cyclodiborazane)s in high yields. This polymerization includes the allylboration reaction of cyano groups and the following dimerization of iminoborane species. The intermediate iminoborane species were detected by IR measurement. The poly(cyclodiborazane)s obtained were found to be more stable toward air than those prepared by allylboration polymerization using triallylborane.     

The birch reduction of heterocyclic compounds V Birch reduction of 2‐ and 5‐acylfuran‐3‐carboxylic acids and reductive elimination of 2‐(arylmethoxymethyl)furan‐3‐carboxylic acids

The Birch reduction of 2‐ and 5‐acylfuran‐3‐carboxylic acid 1 and 4 gave 2‐acyl‐2,3‐dihydrofuran‐3‐carboxylic acid 2 and 5‐acyltetrahydrofuran‐3‐carboxylic acid 5 , respectively. Further examination of the reductive elimination was also studied on 2‐(arylmethoxymethyl)furan‐3‐carboxylic acids 7.     

Kinetics of Si2H2 produced by the 193 nm photolysis of disilane

Si₂H₂ species were produced through the 193 nm excimer laser photolysis of Si₂H₆. Time‐resolved photoionization mass spectrometry was employed to study the reaction kinetics of Si₂H₂. The lower limit of self‐reaction of Si₂H₂ was estimated, k(Si₂H₂ + Si₂H₂) ≥ (1.7 ± 0.5) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹, through analysis of the decay traces. This rate constant was independent of a total pressure on the entire pressure range (p_total = 1–7 Torr). No reaction of Si₂H₂ with H₂, CH₄, SiH₄, and Si₂H₆ was confirmed. The decay rates of Si₂H₂ reacting with O₂, NO, and HCl exhibit negative dependence on the total pressure. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 136–141, 2001     

Lewis-Pairing-Induced Electrochemiluminescence Enhancement from Electron Donor-Acceptor Diads Decorated with Tris(pentafluorophenyl)borane as an Electrochemical Protector

This study reports an effective peripheral decoration of organic donor-acceptor diads with B(C₆F₅)₃ for stabilizing electrogenerated radical ions. By employing a common p-type organic semiconductor benzothienobenzothiophene (BTBT) as the donor, tetracoordinate boron complexes showed improved solution electrochemiluminescence (ECL) intensity, reaching a 156-fold increase compared to that of the parent diad. The unprecedented Lewis-pairing-induced ECL enhancement is attributed to the multiple roles of B(C₆F₅)₃: 1) redistributing frontier orbitals, 2) facilitating electrochemical excitation, and 3) restricting molecular motions. Furthermore, B(C₆F₅)₃ converted the molecular arrangement of BTBT from conventional 2D herringbones into 1D π-stacks. This robust, highly ordered columnar nanostructure allowed red-shifting of the crystalline film ECL with electrochemical doping through the electronic coupling pathways of BTBT. Our approach will facilitate the development of elaborate metal-free ECL systems.     

Synthesis of well-defined azido and amino end-functionalized polystyrene by atom transfer radical polymerization

Mono and difunctional polystyrenes containing active halogenated end groups were prepared by atom transfer radical polymerization (ATRP). Substitution reactions were explored to convert the halogen termini to azido groups, followed by readuction to form the amino functional polymer. Quantitative conversion of the end groups was observed in each transformation reaction. ¹H NMR demonstrated the formation of the azide from the bromide functionality without elimination. The difunctional α,ω-diaminopolystyrene was reacted with terephthaloyl chloride in a condensation process to produce chain-extended polystyrene containing amide bonds along the polymer backbone.