Anion-Responsive Colorimetric and Fluorometric Red-Shift in Triarylborane Derivatives: Dual Role of Phenazaborine as Lewis Acid and Electron Donor.

Photophysical modulation of triarylboranes (TABs) through Lewis acid-base interactions is a fundamental approach in sensing anions. Yet, design principles for anion-responsive TABs displaying significant red-shift in absorption and photoluminescence (PL) have remained elusive. Herein, a new strategy for modulating photophysical properties of TABs in red-shift mode has been presented, endowing a nitrogen-bridged triarylborane (1,4-phenazaborine: PAzB) with a contradictory dual role as a Lewis acid and an electron donor. Following the strategy, PAzB derivatives connected with an electron-deficient azaaromatic have been developed, and these compounds display distinct red-shift in absorption and PL in response to an anion. Spectroscopic analyses and quantum chemical calculations have revealed the formation of tetracoordinate borate upon the addition of fluoride, narrowing the HOMO-LUMO gap and enhancing charge transfer character in the excited state. This approach has also been demonstrated in modulating photophysical properties of solid-state films.

Water-dispersible donor-acceptor-donor π-conjugated bolaamphiphiles enabling a humidity-responsive luminescence color change.

Novel water-dispersible donor-acceptor-donor π-conjugated bolaamphiphiles, having dibenzophenazine as the acceptor and heteroatom-bridged amphiphilic diarylamines as the donors, have been developed. The materials displayed a distinct photoluminescence color change in response to humidity in a poly(vinylalcohol) matrix.

Correction: Water-dispersible donor-acceptor-donor π-conjugated bolaamphiphiles enabling a humidity-responsive luminescence color change.

Correction for 'Water-dispersible donor-acceptor-donor π-conjugated bolaamphiphiles enabling a humidity-responsive luminescence color change' by Tomoya Enjou et al., Chem. Commun., 2024, https://doi.org/10.1039/d3cc05749f.

Photoexcitation of (diarylmethylene)amino benziodoxolones for alkylamination of styrene derivatives with carboxylic acids.

The alkylamination of alkenes using pristine carboxylic acids was achieved by the photoexcitation of (diarylmethylene)amino benziodoxolones (DABXs), which serve as both an oxidant and an aminating reagent (an iminyl radical precursor). The developed method is a simple photochemical reaction without the need for external photosensitizers and shows a broad substrate scope for aliphatic carboxylic acids leading to the formation of primary, secondary, and tertiary alkyl radicals, thus enabling the facile synthesis of various structurally complex amines. Mechanistic investigations including transient absorption spectroscopy measurements using a laser flash photolysis (LFP) method disclosed the unique photochemical reactivity of DABXs, which undergoes homolysis of their I-N bonds to give an iminyl radical and ortho-iodobenzoyloxy radical, the latter of which participates in the single-electron oxidation of carboxylates.

Amino-λ3 -iodane-Enabled Electrophilic Amination of Arylboronic Acid Derivatives.

In this report, we describe the use of amino-λ3 -iodanes in the electrophilic amination of arylboronic acids and boronates. Iodine(III) reagents with transferable amino groups, including one with an NH2 group, were synthesized and used in the amination, allowing the synthesis of a wide range of primary and secondary (hetero)arylamines. Mechanistic studies by DFT calculations indicate that the reaction proceeds through an electrophilic amination process from a tetravalent borate complex with a B-N dative bond.

On-surface synthesis of nitrogen-doped nanographene with an [18]annulene pore on Ag(111).

On-surface synthesis is of importance to fabricate low dimensional carbon-based nanomaterials with atomic precision. Here, we synthesize nitrogen-doped nanographene with an [18]annulene pore and its dimer through sequential reactions of debromination, aryl-aryl coupling, cyclodehydrogenation and C-N coupling on Ag(111) from 3,12-dibromo-7,8-diaza[5]helicene. The inner structures of the products were characterized with scanning tunneling microscopy with a CO terminated tip at low temperature. Furthermore, the first four unoccupied electronic states of the nanographene were investigated with a combination of scanning tunneling spectroscopy and theoretical calculations. Except for the LUMO + 2 state observed at +1.3 V, the electronic states at 500 mV, 750 mV and 1.9 V were attributed to the superatom molecular orbitals at the [18]annulene pore, which were significantly shifted towards the Fermi level due to the hybridization with the confined surface state.

Femtosecond Spectroscopy on a Dibenzophenazine-Cored Macrocycle Exhibiting Thermally Activated Delayed Fluorescence.

The photophysics of a thermally activated delayed fluorescence (TADF) emitting macrocycle consisting of two dibenzo[a,j]phenazine acceptor moieties bridged by two N,N,N',N'-tetraphenylene-1,4-diamine donor units was scrutinized in solution by steady-state and time-resolved spectroscopy. The fluorescence lifetime of the compound proved to be strongly solvent-dependent. It ranges from 6.3 ns in cyclohexane to 34 ps in dimethyl sulfoxide. In polar solvents the fluorescence decay is predominantly due to internal conversion. In non-polar ones radiative decay and intersystem crossing contribute. Contrary to the behaviour in polymer matrices (S. Izumi et al., J. Am. Chem. Soc. 2020, 142, 1482) the excited state decay is not predominantly due to prompt and delayed fluorescence. The solvent-dependent behaviour is analyzed with the aid of quantum chemical computations.

Tris(pentafluorophenyl)borane-Catalyzed Stereospecific Bromocyanation of Styrene Derivatives with Cyanogen Bromide.

We, herein, report on the bromocyanation of styrene derivatives with cyanogen bromide in the presence of tris(pentafluorophenyl)borane which functions as a Lewis acid catalyst that can effectively activate cyanogen bromide. This reaction proceeds through a stereospecific syn-addition. The protocol is operationally simple and provides practical access to ß-bromonitriles.

α-Amination of Carbonyl Compounds by Using Hypervalent Iodine-Based Aminating Reagents Containing a Transferable (Diarylmethylene)amino Group.

Hypervalent iodine-based aminating reagents containing a transferable (diarylmethylene)amino group can be used for the α-amination of simple carbonyl compounds such as esters, amides, and ketones in the presence of a lithium base. The (diarylmethylene)amino groups of the products can be readily modified, thus providing access to primary amines and diarylmethylamines. The developed method features transition-metal-free conditions and a simple one-pot procedure without the need to prepare enolate equivalents separately, thus offering a general and practical approach to the synthesis of a wide variety of α-amino carbonyl compounds. Experimental mechanistic investigations indicate that this amination proceeds through a unique radical coupling of an α-carbonyl radical with an iminyl radical; they are generated through a single-electron transfer between a lithium enolate and the hypervalent iodine reagent.

Stereospecific Oxycyanation of Alkenes with Sulfonyl Cyanide.

Oxycyanation of alkenes would allow the direct construction of useful ß-hydroxy nitrile scaffolds. However, only limited examples of such reactions have been reported, and some problems including limited substrate scope and the lack of diastereocontrol in the case of the oxycyanation of internal alkenes have arisen. We herein report on the intermolecular oxycyanation of alkenes using p-toluenesulfonyl cyanide (TsCN) in the presence of tris(pentafluorophenyl)borane (B(C6 F5 )3 ) as a catalyst, affording products that contain a sulfinyloxy group and a cyano group at the vicinal position. The reaction features a stereospecific syn-addition. The reaction also shows a broad substrate scope with good functional group tolerance. Mechanistic investigations by experimental studies and density functional theory (DFT) calculations revealed that the reaction proceeds via an unprecedented stereospecific mechanism through the electrophilic cyanation of alkenes, in which B(C6 F5 )3 efficiently activates TsCN through the coordination of the cyano group to the boron center.

3,11-Diaminodibenzo[a,j]phenazine: Synthesis, Properties, and Applications to Tröger's Base-Forming Ladder Polymerization.

A new class of diamino-substituted π-extended phenazine compound was synthesized, and its photophysical properties were investigated. The U-shaped diaminophenazine displayed photoluminescence in solution with moderate quantum yield. The diamino aromatic compound was found applicable to the poly-condensation with formaldehyde to form Tröger's base ladder polymer. The obtained microporous ladder polymer features high CO2 adsorption selectivity against N2 , most likely due to the presence of basic nitrogen atoms in the phenazine rings.

Comparative study of thermally activated delayed fluorescent properties of donor-acceptor and donor-acceptor-donor architectures based on phenoxazine and dibenzo[a,j]phenazine.

A new thermally activated delayed fluorescence (TADF) compound based on a donor-acceptor (D-A) architecture (D = phenoxazine; A = dibenzo[a,j]phenazine) has been developed, and its photophysical properties were characterized. The D-A compound is applicable as an emitting material for efficient organic light-emitting diodes (OLEDs), and its external quantum efficiency (EQE) exceeds the theoretical maximum of those with prompt fluorescent emitters. Most importantly, comparative study of the D-A molecule and its D-A-D counterpart from the viewpoints of the experiments and theoretical calculations revealed the effect of the number of the electron donor on the thermally activated delayed fluorescent behavior.

Dibenzophenazine-Based TADF Emitters as Dual Electrochromic and Electroluminescence Materials.

Previous work has reported the synthesis of donor-acceptor-donor molecules based on dibenzophenazine acceptor group, presenting thermally activated delayed fluorescent (TADF) properties and their application in the assembly of highly efficient electroluminescent devices. Herein, we focus on the characterisation of charge carrier species through UV-Vis-NIR spectroelectrochemical and potentiostatic EPR techniques, in addition to the investigation of electropolymerisation properties of some compounds depicted in this study. The promising electrochromic features of both small molecules and conjugated polymers led to the assembly and investigation of electrochromic devices, evidencing the materials' versatility, applied in such different approaches as electrochromic windows and electroluminescent devices. Furthermore, the assembled OLEDs provided high efficiencies, with small roll-off, EQEs up to 20.5 % and luminance values up to 85 000 cd/m2 .

Dual-photofunctional organogermanium compound based on donor-acceptor-donor architecture.

A dual-photofunctional organogermanium compound based on a donor-acceptor-donor architecture that exhibits thermally activated delayed fluorescence and mechano-responsive luminochromism has been developed. The developed compound was successfully applied as an emitter for efficient organic light-emitting diodes.

Intramolecular C-H Amination of N-Alkylsulfamides by tert-Butyl Hypoiodite or N-Iodosuccinimide.

1,3-Diamines are an important class of compounds that are broadly found in natural products and are also widely used as building blocks in organic synthesis. Although the intramolecular C-H amination of N-alkylsulfamide derivatives is a reliable method for the construction of 1,3-diamine structures, the majority of these methods involve the use of a transition-metal catalyst. We herein report on a new transition-metal-free method using tert-butyl hypoiodite (t-BuOI) or N-iodosuccinimide (NIS), enabling secondary non-benzylic and tertiary C-H amination reactions to proceed. The cyclic sulfamide products can be easily transformed into 1,3-diamines. Mechanistic investigations revealed that amination reactions using t-BuOI or NIS each proceed via different pathways.

The Impact of C2 Insertion into a Carbazole Donor on the Physicochemical Properties of Dibenzo[a,j]phenazine-Cored Donor-Acceptor-Donor Triads.

Novel electron donor-acceptor-donor (D-A-D) compounds comprising dibenzo[a,j]phenazine as the central acceptor core and two 7-membered diarylamines (iminodibenzyl and iminostilbene) as the donors have been designed and synthesized. Investigation of their physicochemical properties revealed the impact of C2 insertion into well-known carbazole electron donors on the properties of previously reported twisted dibenzo[a,j]phenazine-core D-A-D triads. Slight structural modification caused a drastic change in conformational preference, allowing unique photophysical behavior of dual emission derived from room-temperature phosphorescence and triplet-triplet annihilation. Furthermore, electrochemical analysis suggested sigma-dimer formation and electrochemical polymerization on the electrode. Quantum chemical calculations also rationalized the experimental results.

Tris(pentafluorophenyl)borane-Catalyzed Formal Cyanoalkylation of Indoles with Cyanohydrins.

Despite the significant achievements related to the C3 functionalization of indoles, cyanoalkylation reactions continue to remain rather limited. We herein report on the formal C3 cyanoalkylation of indoles with cyanohydrins in the presence of a tris(pentafluorophenyl)borane (B(C6F5)3) catalyst. It is noteworthy that cyanohydrins are used as a cyanoalkylating reagent in the present reaction, even though they are usually used as only a HCN source. Mechanistic investigations revealed the unique reactivity of the B(C6F5)3 catalyst in promoting the decomposition of a cyanohydrin by a Lewis acidic activation through the coordination of the cyano group to the boron center. In addition, a catalytic three-component reaction using indoles, aldehydes as a carbon unit, and acetone cyanohydrin that avoids the discrete preparation of each aldehyde-derived cyanohydrin is also reported. The developed methods provide straightforward, highly efficient, and atom-economic access to various types of synthetically useful indole-3-acetonitrile derivatives containing α-tertiary or quaternary carbon centers.

Near Fermi Superatom State Stabilized by Surface State Resonances in a Multiporous Molecular Network.

Two-dimensional honeycomb molecular networks confine a substrate's surface electrons within their pores, providing an ideal playground to investigate the quantum electron scattering phenomena. Besides surface state confinement, laterally protruding organic states can collectively hybridize at the smallest pores into superatom molecular orbitals. Although both types of pore states could be simultaneously hosted within nanocavities, their coexistence and possible interaction are unexplored. Here, we show that these two types of pore states do coexist within the smallest nanocavities of a two-dimensional halogen-bonding multiporous network grown on Ag(111) studied using a combination of scanning tunneling microscopy and spectroscopy, density functional theory calculations, and electron plane wave expansion simulations. We find that superatom molecular orbitals undergo an important stabilization when hybridizing with the confined surface state, following the significant lowering of its free-standing energy. These findings provide further control over the surface electronic structure exerted by two-dimensional nanoporous systems.

Diastereodivergent Intermolecular 1,2-Diamination of Unactivated Alkenes Enabled by Iodine Catalysis.

The stereospecific, substrate (nitrogen source)-controlled intermolecular anti- and syn-1,2-diaminations of unactivated alkenes using the same catalysis (an iodine catalyst) is reported. The combined use of the two potential methods provides access to all of the disastereomeric forms of 1,2-diamines in spite of the availability of E- and Z-alkenes, and the resulting products can be readily converted into free vicinal diamines.

Heavy-Atom-Free Room-Temperature Phosphorescent Organic Light-Emitting Diodes Enabled by Excited States Engineering.

Room temperature phosphorescence materials offer great opportunities for applications in optoelectronics, due to their unique photophysical characteristics. However, heavy-atom-free organic emitters that can realize distinct electrophosphorescence are rarely exploited. Herein a new approach for designing heavy-atom-free organic room temperature phosphorescence emitters for organic light-emitting diodes is presented. The subtle tuning of the singlet and triplet excited states energies by appropriate choice of host matrix allows tailored emission properties and switching of emission channels between thermally activated delayed fluorescence and room temperature phosphorescence. Moreover, an efficient and heavy-atom-free room temperature phosphorescence organic light-emitting diode using the developed emitter is realized.