Adaptation of Dynamic Covalent Systems of Imine Constituents to Medium Change by Component Redistribution under Reversible Phase Separation

A dynamic covalent library of interconverting imine constituents, dissolved in an acetonitrile/water mixture, undergoes constitutional reorganization upon phase separation induced by a physical stimulus (heat) or a chemical effector (inorganic salt, carbohydrate, organic solvent). The process has been made reversible, regenerating the initial library upon phase reunification. It represents the behavior of a dynamic covalent library upon reversible phase separation and its adaptation to a phase change, with up-regulation in each phase of the fittest constituents by component selection. Finally, the system exemplifies the splitting of a 2D (square) constitutional dynamic network into a 3D (cube) one

The R₃O⁺···H⁺ Hydrogen Bond: Toward a Tetracoordinate Oxadionium(2+) Ion

Oxatriquinanes are tricyclic oxonium ions which are known to possess remarkable solvolytic stability compared to simple alkyl oxonium salts. Their rigid, hemispherical structure presents an oxygen at the apex of three fused five-membered rings. While trivalent oxygen species like these have been well described in the literature, the ability of oxygen to enter into a fourth covalent bonding relationship has been visited in theory and suggested by the outcome of certain reactions conducted in superacidic media, but has never been established by the characterization of a stable, persistent R₃OH²⁺ or R₄O²⁺ ion. In this study, the nucleophilicity of the oxatriquinane oxygen was evaluated first by a series of protonation studies using the Brønsted superacid H­(CHB₁₁Cl₁₁) both in the solid state and in liquid HCl solution. The interaction of the oxatriquinane oxygen with a bridging carbocation was also examined. A strong case could be made for the occurrence of hydrogen bonding between H­(CHB₁₁Cl₁₁) and oxatriquinane using IR spectroscopy. Under the most forcing protonation conditions, the oxatriquinane ring is cleaved to give a bridged, dicationic, protonated tetrahydrofuran–carbenium ion

Quantitative Dedoping of Conductive Polymers

Although doping is a cornerstone of the inorganic semiconductor industry, most devices using organic semiconductors (OSCs) make use of intrinsic (undoped) materials. Recent work on OSC doping has focused on the use of dopants to modify a material’s physical properties, such as solubility, in addition to electronic and optical properties. However, if these effects are to be exploited in device manufacturing, a method for dedoping organic semiconductors is required. Here, we outline two chemical strategies for dedoping OSC films. In the first strategy, we use an electron donor (a tertiary amine) to act as competitive donor. This process is based on a thermodynamic equilibrium between ionization of the donor and OSC and results in only partial dedoping. In the second strategy, we use an electron donor that subsequently reacts with the p-type dopant to create a nondoping product molecule. Primary and secondary amines undergo a rapid addition reaction with the dopant molecule 2,3,5,6-tetrafluoro-7,7,8,8,-tetracyanoquinodimethane (F4TCNQ), with primary amines undergoing a further reaction eliminating HCN. Under optimized conditions, films of semiconducting polymer poly­(3-hexylthiophene) (P3HT) dedoped with 1-propylamine (PA) reach as-cast fluorescence intensities within 5 s of exposure to the amine, eventually reaching 140% of the as-cast values. Field-effect mobilities similarly recover after dedoping. Quantitative fluorescence recovery is possible even in highly fluorescent polymers such as PFB, which are expected to be much more sensitive to residual dopants. Interestingly, treatment of undoped films with PA also yields increased fluorescence intensity and a reduction in conductivity of at least 2 orders of magnitude. These results indicate that the process quantitatively removes not only F4TCNQ but also intrinsic p-type impurities present in as-cast films. The dedoping strategies outlined in this article are generally applicable to other p- and n-type molecular dopants in OSC films

Intramolecular Energy and Electron Transfer within a Diazaperopyrenium-Based Cyclophane

Molecules capable of performing highly efficient energy transfer and ultrafast photoinduced electron transfer in well-defined multichromophoric structures are indispensable to the development of artificial photofunctional systems. Herein, we report on the synthesis, characterization, and photophysical properties of a rationally designed multichromophoric tetracationic cyclophane, <b>DAPP­Box⁴⁺</b>, containing a diaza­pero­pyrenium (DAPP²⁺) unit and an extended viologen (Ex­BIPY²⁺) unit, which are linked together by two <i>p</i>-xylylene bridges. Both ¹H NMR spectroscopy and single-crystal X-ray diffraction analysis confirm the formation of an asymmetric, rigid, box-like cyclophane, <b>DAPP­Box⁴⁺</b>. The solid-state superstructure of this cyclophane reveals a herringbone-type packing motif, leading to two types of π···π interactions: (i) between the Ex­BIPY²⁺ unit and the DAPP²⁺ unit (π···π distance of 3.7 Å) in the adjacent parallel cyclophane, as well as (ii) between the Ex­BIPY²⁺ unit (π···π distance of 3.2 Å) and phenylene ring in the closest orthogonal cyclophane. Moreover, the solution-phase photophysical properties of this cyclophane have been investigated by both steady-state and time-resolved absorption and emission spectroscopies. Upon photoexcitation of <b>DAPP­Box⁴⁺</b> at 330 nm, rapid and quantitative intramolecular energy transfer occurs from the ^1*Ex­BIPY²⁺ unit to the DAPP²⁺ unit in 0.5 ps to yield ^1*DAPP²⁺. The same excitation wavelength simultaneously populates a higher excited state of ^1*DAPP²⁺ which then undergoes ultrafast intramolecular electron transfer from ^1*DAPP²⁺ to Ex­BIPY²⁺ to yield the DAPP^3+•–Ex­BIPY^+• radical ion pair in τ = 1.5 ps. Selective excitation of DAPP²⁺ at 505 nm populates a lower excited state where electron transfer is kinetically unfavorable

Intramolecular Energy and Electron Transfer within a Diazaperopyrenium-Based Cyclophane

Molecules capable of performing highly efficient energy transfer and ultrafast photoinduced electron transfer in well-defined multichromophoric structures are indispensable to the development of artificial photofunctional systems. Herein, we report on the synthesis, characterization, and photophysical properties of a rationally designed multichromophoric tetracationic cyclophane, <b>DAPP­Box⁴⁺</b>, containing a diaza­pero­pyrenium (DAPP²⁺) unit and an extended viologen (Ex­BIPY²⁺) unit, which are linked together by two <i>p</i>-xylylene bridges. Both ¹H NMR spectroscopy and single-crystal X-ray diffraction analysis confirm the formation of an asymmetric, rigid, box-like cyclophane, <b>DAPP­Box⁴⁺</b>. The solid-state superstructure of this cyclophane reveals a herringbone-type packing motif, leading to two types of π···π interactions: (i) between the Ex­BIPY²⁺ unit and the DAPP²⁺ unit (π···π distance of 3.7 Å) in the adjacent parallel cyclophane, as well as (ii) between the Ex­BIPY²⁺ unit (π···π distance of 3.2 Å) and phenylene ring in the closest orthogonal cyclophane. Moreover, the solution-phase photophysical properties of this cyclophane have been investigated by both steady-state and time-resolved absorption and emission spectroscopies. Upon photoexcitation of <b>DAPP­Box⁴⁺</b> at 330 nm, rapid and quantitative intramolecular energy transfer occurs from the ^1*Ex­BIPY²⁺ unit to the DAPP²⁺ unit in 0.5 ps to yield ^1*DAPP²⁺. The same excitation wavelength simultaneously populates a higher excited state of ^1*DAPP²⁺ which then undergoes ultrafast intramolecular electron transfer from ^1*DAPP²⁺ to Ex­BIPY²⁺ to yield the DAPP^3+•–Ex­BIPY^+• radical ion pair in τ = 1.5 ps. Selective excitation of DAPP²⁺ at 505 nm populates a lower excited state where electron transfer is kinetically unfavorable

Correction to “A Hafnium-Based Metal–Organic Framework as a Nature-Inspired Tandem Reaction Catalyst”

Correction to “A Hafnium-Based Metal–Organic Framework as a Nature-Inspired Tandem Reaction Catalyst

A Hafnium-Based Metal–Organic Framework as a Nature-Inspired Tandem Reaction Catalyst

Tandem catalytic systems, often inspired by biological systems, offer many advantages in the formation of highly functionalized small molecules. Herein, a new metal–organic framework (MOF) with porphyrinic struts and Hf₆ nodes is reported. This MOF demonstrates catalytic efficacy in the tandem oxidation and functionalization of styrene utilizing molecular oxygen as a terminal oxidant. The product, a protected 1,2-aminoalcohol, is formed selectively and with high efficiency using this recyclable heterogeneous catalyst. Significantly, the unusual regioselective transformation occurs only when an Fe-decorated Hf₆ node and the Fe–porphyrin strut work in concert. This report is an example of concurrent orthogonal tandem catalysis