Spotlight on Zinc: Exploring the Visible Light Responsiveness of Zinc Complexes.

Group 12 element zinc(II)-based d complexes have long been known for their inherent colorlessness, which has limited their applications in visible light-driven photophysical and photochemical applications, despite the attractiveness of inexpensive and low-toxicity zinc metal. Based on precedents with nickel(0) and copper(I) complexes, which also adopt the d electronic configuration, achieving a visible light response from zinc(II) complexes seems feasible; however, investigations and proactive design strategies specifically tailored to zinc remain lacking. In this context, the present invited concept paper highlights zinc's potential for visible light responsiveness and evaluates how molecular designs can achieve this capability.

Four- and three-coordinate planar iron(II) complexes supported by bulky organosilyl ligands.

The ligand exchange reaction of (THF)Fe[Si(SiMe)] with 2 equivalents of an N-heterocyclic carbene (NHC) led to the formation of a square-planar iron(II) complex with -oriented -Si(SiMe) ligands. Conversely, the introduction of a -coordinate bidentate organosilyl ligand instead of -Si(SiMe) resulted in the formation of a square planar iron(II) complex supported by a -coordinate bidentate organosilyl ligand. A three-coordinate planar iron(II) bis(silyl) complex was also synthesized using a -coordinate bidentate organosilyl ligand and a cyclic (alkyl)(amino)carbene auxiliary ligand.

Visible Light Responsive Dinuclear Zinc Complex Consisting of Proximally Arranged Two d -Zinc Centers.

So far, Zn(II)-based d complexes have been known to be colorless unless they are accompanied by chromophoric groups, and therefore both fundamental and advanced photophysical performance of Zn centers of complexes, especially in visible-light regions has been unexplored. Here, we first demonstrate a dinuclear Zn(II) complex that shows visible light absorption using an orbital distributed over closely contacted two Zn centers experimentally determined by X-ray crystallography. A contrastive study demonstrated that intermetallic orbital interaction in dinuclear Zn(II) complex is responsible for capturing visible light to exhibit orangish yellow color, whereas an analogous one without such an interaction is colorless.

Operando ESR observation in thermally activated delayed fluorescent organic light-emitting diodes.

Organic light-emitting diodes (OLEDs) using thermally activated delayed fluorescence (TADF) materials have advantages over OLEDs using conventional fluorescent materials or high-cost phosphorescent materials, including higher efficiency and lower cost. To attain further high device performance, clarifying internal charge states in OLEDs at a microscopic viewpoint is crucial; however, only a few such studies have been performed. Here, we report a microscopic investigation into internal charge states in OLEDs with a TADF material by electron spin resonance (ESR) at a molecular level.

Dinuclear and tetranuclear group 10 metal complexes constructed from linear tetrasilane comprising both Si-H and Si-Si moieties.

The activation of Si-H bonds and/or Si-Si bonds in organosilicon compounds by transition-metal species plays a crucial role for the production of functional organosilicon compounds. Although group-10-metal species are frequently used to activate Si-H and/or Si-Si bonds, so far, systematic investigation to clarify the preferences of these metal species with respect to the activation of Si-H and/or Si-Si bonds remain elusive. Here, we report that platinum(0) species that bear isocyanide or N-heterocyclic-carbene (NHC) ligands selectively activates the terminal Si-H bonds of the linear tetrasilane Ph(H)SiSiPhSiPhSi(H)Ph in a stepwise manner, whereby the Si-Si bonds remain intact.

A Donor-Acceptor 10-Cycloparaphenylene and Its Use as an Emitter in an Organic Light-Emitting Diode.

Here, we explored the possibility of using cycloparaphenylenes (CPP) within a donor-acceptor TADF emitter design. contains four electron-donating moieties connected to a . In the 15 wt % doped in CzSi film, showed sky-blue emission with λ = 475 nm, Φ = 29%, and triexponential emission decays with τ of 4.

Imidazole Acceptor for Both Vacuum-Processable and Solution-Processable Efficient Blue Thermally Activated Delayed Fluorescence.

The members of the imidazole family have been widely used for electron transporting, host, conventional fluorescent, and phosphorescent materials. Although the imidazole core also has great potential as an acceptor segment of deep-blue thermally activated delayed fluorescence (TADF) owing to its high triplet energy, the emission color of imidazole-based TADF organic light-emitting diodes (OLEDs) has so far been limited to blue to green. In this work, four acridan-imidazole systems are theoretically designed aiming for deep- or pure-blue emitters.

Highly Efficient and Stable Blue Organic Light-Emitting Diodes based on Thermally Activated Delayed Fluorophor with Donor-Void-Acceptor Motif.

Thermally activated delayed fluorophores (TADF) with donor-acceptor (D-A) structures always face strong conjugation between donor and acceptor segments, rendering delocalized new molecular orbitals that go against blue emission. Developing TADF emitters with blue colors, high efficiencies, and long lifetimes simultaneously is therefore challenging. Here, a D-void-A structure with D and A moieties connected at the void-position where the frontier orbital from donor and acceptor cannot be distributed, resulting in nonoverlap of the orbitals is proposed.

Effect of a twin-emitter design strategy on a previously reported thermally activated delayed fluorescence organic light-emitting diode.

In this work we showcase the emitter in which we employed a twin-emitter design of our previously reported material, . This new system presented a red-shifted emission at 488 nm compared to that of at 475 nm and showed a comparable photoluminescence quantum yield of 57.1% in a 20 wt % CzSi film versus 63.

Exact Solution of Kinetic Analysis for Thermally Activated Delayed Fluorescence Materials.

The photophysical analysis of thermally activated delayed fluorescence (TADF) materials has become instrumental for providing insights into their stability and performance, which is not only relevant for organic light-emitting diodes but also for other applications such as sensing, imaging, and photocatalysis. Thus, a deeper understanding of the photophysics underpinning the TADF mechanism is required to push materials design further. Previously reported analyses in the literature of the kinetics of the various processes occurring in a TADF material rely on several a priori assumptions to estimate the rate constants for forward and reverse intersystem crossing.

Multichromophore Molecular Design for Thermally Activated Delayed-Fluorescence Emitters with Near-Unity Photoluminescence Quantum Yields.

Three multichromophore thermally activated delayed fluorescence (TADF) molecules, , , and , were synthesized and characterized. These molecules were designed by connecting the TADF moiety 4,5-di(9-carbazol-9-yl)phthalonitrile () to different positions of a central benzene ring scaffold. Three highly soluble emitters all exhibited near-quantitative photoluminescence quantum yields (Φ) in toluene.

Molecular Vibration Accelerates Charge Transfer Emission in a Highly Twisted Blue Thermally Activated Delayed Fluorescence Material.

In the development of new organic light-emitting diodes, thermally activated delayed fluorescence (TADF) materials have drawn interest because of their ability to upconvert electrically generated triplet excitons into singlets. Efficient TADF requires a well-balanced large transition dipole moment (μ) between the lowest excited singlet state (S) and the ground state (S) and a small energy splitting (Δ) between S and the lowest triplet state (T). However, a number of highly twisted donor-acceptor-type TADF molecules have been reported to exhibit high performance in OLEDs, although these molecules may sacrifice μ in exchange for a very small Δ.

Efficient Direct Reverse Intersystem Crossing between Charge Transfer-Type Singlet and Triplet States in a Purely Organic Molecule.

The front cover artwork is provided by the group of Prof. Hironori Kaji, Dr. Yoshimasa Wada, and Mr.

Efficient Direct Reverse Intersystem Crossing between Charge Transfer-Type Singlet and Triplet States in a Purely Organic Molecule.

In the field of organic light-emitting diodes, thermally activated delayed fluorescence (TADF) materials have achieved great performance. The key factor for this performance is the small energy gap (ΔE ) between the lowest triplet (T ) and singlet excited (S ) states, which can be realized in a well-separated donor-acceptor system. Such systems are likely to possess similar charge transfer (CT)-type T and S  states.

Thiophene-Fused Naphthodiphospholes: Modulation of the Structural and Electronic Properties of Polycyclic Aromatics by Precise Fusion of Heteroles.

For polycyclic aromatics with heterole-fused structures, the orientation of fused heterole rings as well as the geometry of their fused structures has a large impact on the physicochemical properties. In this study, a series of isomers of thiophene-fused naphthodiphospholes was designed and synthesized. Systematic investigation unveiled the explicit impact of heterole-fused structures on their structural and electronic properties.

Conformation Control of Iminodibenzyl-Based Thermally Activated Delayed Fluorescence Material by Tilted Face-to-Face Alignment With Optimal Distance (tFFO) Design.

In organic light-emitting diodes (OLEDs), all triplet excitons can be harvested as light via reverse intersystem crossing (RISC) based on thermally activated delayed fluorescence (TADF) emitters. To realize efficient TADF, RISC should be fast. Thus, to accomplish rapid RISC, in the present study, a novel TADF emitter, namely, TpIBT-tFFO, was reported.

Thermally Activated Delayed Fluorescent Materials Combining Intra- and Intermolecular Charge Transfers.

A novel thermally activated delayed fluorescent (TADF) compound, 9-(3-((4,6-diphenyl-1,3,5-triazin-2-yl)oxy)phenyl)-3,6-diphenyl-9 H-carbazole (PhCz- o-Trz), with a donor-σ-acceptor (D-σ-A) motif is developed. A flexible small space σ-junction is adopted to partly suppress the intramolecular charge transfer (intra-CT) while inversely enhancing the intermolecular charge transfer (inter-CT) between D/A moieties, realizing the coexistence of both intra-CT and inter-CT in an amorphous aggregate. The coexistence of dual CTs increases the complexity of the singlet and triplet state mixing, enhancing the triplet-to-singlet spin-flip transition and thereby the TADF emission.

Adamantyl Substitution Strategy for Realizing Solution-Processable Thermally Stable Deep-Blue Thermally Activated Delayed Fluorescence Materials.

Highly efficient solution-processable emitters, especially deep-blue emitters, are greatly desired to develop low-cost and low-energy-consumption organic light-emitting diodes (OLEDs). A recently developed class of potentially metal-free emitters, thermally activated delayed fluorescence (TADF) materials, are promising candidates, but solution-processable TADF materials with efficient blue emissions are not well investigated. In this study, first the requirements for the design of efficient deep-blue TADF materials are clarified, on the basis of which, adamantyl-substituted TADF molecules are developed.

Clinical characteristics and computed tomography findings in children with 2009 pandemic influenza A (H1N1) viral pneumonia.

In this article we review the clinical characteristics and computed tomography (CT) findings in children with 2009 pandemic H1N1 influenza viral pneumonia. The medical charts of 88 children with pandemic H1N1 influenza virus infection, admitted to our hospital in Japan from 10 August to 28 December 2009, were reviewed; we compared the clinical features of these children with those of 61 children admitted with seasonal influenza A during the previous 3 seasons. Of 88 patients, 53 (60%) had radiographic findings consistent with pneumonia and 34 patients underwent a chest computed tomography (CT) scan.

Synchronization index of neural spike trains in response to simulated vowel signal stimuli in the presence of a pseudo-spontaneous activity.

This article presents a statistical analysis of neural spike trains in an auditory nerve fiber (ANF) model stimulated extracellularly by simulated vowel electric stimuli under the case where a high-rate pulsatile waveform is presented as a conditioner for increasing the across-fiber-independency, i.e., desynchronization.

Irritated seborrheic keratosis of the external ear canal.

Although a seborrheic keratosis is not rare on the skin of the trunk, extremities, head and neck of an elderly person, it is uncommon to originate in the external ear canal. Even rarer, an irritated subtype may arise in this location. We report the case of a 63-year-old man with an irritated seborrheic keratosis arising in the right external ear canal, who first presented with a bloody discharge from his right ear canal 3 years and 10 months before the subsequent operation.