Metal oxide charge transfer complex for effective energy band tailoring in multilayer optoelectronics

Metal oxides are intensively used for multilayered optoelectronic devices such as organic light-emitting diodes (OLEDs). Many approaches have been explored to improve device performance by engineering electrical properties. However, conventional methods cannot enable both energy level manipulation and conductivity enhancement for achieving optimum energy band configurations. Here, we introduce a metal oxide charge transfer complex (NiO:MoO3-complex), which is composed of few-nm-size MoO3 domains embedded in NiO matrices, as a highly tunable carrier injection material. Charge transfer at the finely dispersed interfaces of NiO and MoO3 throughout the entire film enables effective energy level modulation over a wide work function range of 4.47 – 6.34 eV along with enhanced electrical conductivity. The high performance of NiO:MoO3-complex is confirmed by achieving 189% improved current efficiency compared to that of MoO3-based green OLEDs and also an external quantum efficiency of 17% when applied to blue OLEDs, which is superior to 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile-based conventional devices.

Organic charge transfer complex at the boundary between superconductors and insulators: critical role of a marginal part of conduction pathways

κ-ET2Cu[N(CN)2]I (ET = bis(ethylenedithio)tetrathiafulvalene) has previously been reported as both a superconductor and an insulator. Examination of each single crystal revealed that the electrical properties are governed by slight differences...

Decoding key transient inter-catalyst interactions in a metallaphotoredox-catalysed cross-electrophile coupling reaction

Metallaphotoredox chemistry has recently witnessed a renaissance through the use of abundant first-row transition metals combined with suitable photocatalysts. The intricate details arising from the combination of two (or more) catalytic components during the reaction and specially the inter-catalyst interactions remain poorly understood. As a representative example of a catalytic process featuring such intricacies, we here present a meticulous study of the mechanism of a cobalt-organophotoredox catalysed allylation of aldehydes. Importantly, the commonly proposed elementary steps in reductive metallaphotoredox chemistry are more complex than previously assumed. After initial reductive quenching, a transient charge-transfer complex forms that interacts with both the transition-metal catalyst, as well as the catalytic base. Surprisingly, the former interaction leads to deactivation due to induced charge recombination, while the latter promotes deprotonation of the electron donor, which is a crucial step in order to promote productive catalysis, but is often neglected. Due to the low efficiency of this process, the overall catalytic reaction is photon-limited and the cobalt catalyst remains in a dual resting state awaiting photoinduced reduction. These new insights are of general importance to the synthetic community, as photoredox chemistry has become a powerful tool used in the creation of elusive compounds through carbon-carbon bond formations. Understanding the underlying factors that determine the efficiency of such reactions provides a conceptually stronger reactivity paradigm to empower future approaches to synthetic challenges that rely on dual metallaphotoredox catalysis.

Visualization of Charge-Transfer Complex for the Detection of 2, 4, 6-Trinitrotoluene Using Terahertz Chemical Microscope

This study focuses on the visualization of a charge-transfer complex, namely a Meisenheimer complex, for the detection of uncharged 2, 4, 6-trinitrotoluene (TNT) explosives by developing a terahertz chemical microscope (TCM) imaging system. The organic amine 3-aminopropyltriethoxysilane (APTES) was immobilized on an SiO2-film-coated TCM sensing plate, where it interacted with TNT molecules. The surface electrical potential distribution of TNT, APTES, and the charge-transfer complex was mapped. An electrical potential shift occurred due to the formation of a charge-transfer complex between the electron-rich amino-silane APTES and electron-deficient TNT molecules on the surface of the sensing plate. The electrical imaging and detection of TNT explosives by using the TCM imaging system were demonstrated by measuring the amplitude of the terahertz pulse caused by this electrical potential shift. N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane and N1-(3-trimethoxysilylpropyl)diethylenetriamine were used for further evaluation and comparison of color changes arising from the amine-TNT interactions. The results have shown that TCM imaging is a promising method for the detection of uncharged TNT explosives at a low (sub-parts-per-million) concentration.

Radical Perfluoroalkylation Enabled by a Catalytically Generated Halogen Bonding Complex and Visible Light Irradiation

Despite the many recent advances in exploiting stoichiometric charge-transfer complexes in visible light promoted single-electron redox reactions, catalytic approaches to charge-transfer complex formation remain limited. This report describes the radical perfluoroalkylation of electron-rich (hetero)arenes and iodoperfluoroalkylation of alkenes and alkynes promoted by a substituted hydroquinone catalyst. Mechanistic and computational studies indicate that the reaction is initiated by the formation of a visible light absorbing halogen bonding complex between the hydroquinone catalyst and the perfluoroalkyl iodide radical precursor.

Studies of Some Strained Organic Molecules

<p>The characterisation of rare examples of C1-substituted cyclopropanaphthalenes has been achieved with silanes (104) and (112) by employing the C1 anion (106). With toluene, N,N-dimethylacetamide, and cyclopropanaphthalene (58) this same anion gives the novel 6-methyl-7H-dibenzo[b,g]fluorene (179), a formal dimer of cycloproparene (58). Hydrocarbon (179) is the sole dibenzo[b,g]hydrocarbon characterised and this has required extensive spectroscopic study with confirmation from X-ray analysis. A possible new route to alkylidenecyclopropanaphthalenes (114) employing lithiate (170) and either cycloproparene (58) or its disilyl analogue (105) was found to offer no advantage over known procedures. Application of the protocols embodied in this procedure to brominated synthons (114o) and (114p) has afforded novel pi-extended methylidene compounds (197a) and (199) in low yield. Cyclopentadienylidene (197a) has also been prepared in better yield from benzophenone-containing methylidenecycloproparene (200). Initial attempts to obtain (200) from anion (193) and N,N-dimethylbenzamide were unsuccessful and gave instead the new phenol (114q). The first acylcycloproparenes (189) and (202) have been obtained in modest yield from anion (103) and N,N-dimethyl-acetamide, and -benzamide. With N,N-dimethyl-carbamoyl chloride anion (103) gives the bis-amide (205). With hydrochloric acid these acylcycloproparenes give rise to 2,3-disubstituted naphthalenes rather than 2-substituted naphthalenes that typically arise from protonation at the aromatic ring. Thermolysis leads to ring expansion and naphthofuran formation. Enolate formation from the 1-acyl-cyclopropanaphthalenes (189) and (202) and anion capture at oxygen affords the first cyclopropanaphthalenylidene enol ethers (219) and (220). 1H-Cyclopropa[b]naphthalene-3,6-dione (154) adds buta-1,3-diene across the enedione Pi-bond to give the tetrahydrocyclopropanthraquinone (160). Enolisation of (160) provides phenolate (234) that can be diverted to ether (229) or oxidised to the dihydroanthraquinone (230). Dehydrogenation of (229) is readily achieved and gives the first anthraquinone of the cycloproparene series 1H-cyclopropa[b]anthracene-3,8-dione (162); quinone (162) is only the second cyclopropaquinone to have been characterised. Alternative routes to quinone (162) and its 3,8-dimethoxy analogue (163) have been examined with a view to providing the first alkylidenecyclopropanthracenes. The first examples of cross-conjugated dithiole-containing cycloproparenes, (169) and (267), have been prepared from cyclopropanthraquinone (162) but they are unstable solids. The pi-extended dithiole-containing methylidene compound (273) has been prepared in good yield from Wittig-Horner olefination of the benzoylmethylidene compound (200). Evidence was obtained to support the formation of a charge-transfer complex from it. Ketones already carrying a conjugated dithiole moiety participate in the Peterson olefination with the alpha-silyl anion (106) and give the new pi-extended methylidenecyclopropanaphthalenes (274) and (277) of limited stability.</p>