Electron Transfer Enhanced by a Minimal Energetic Driving Force at the Organic-Semiconductor Interface.

Energetic driving force for electron transfer must be minimized to realize efficient optoelectronic devices including organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). Exploring dynamics of a charge transfer (CT) state at an interface leads to a comprehension of the relationship between energetics, electron transfer efficiency, and device performance. Here, we investigate the electron transfer from the CT state to the triplet excited state (T1) in upconversion OLEDs with 45 material combinations. By analyzing the CT emission and the singlet excited state emission from triplet-triplet annihilation via dark T1, their energetics and electron transfer efficiencies are extracted. We demonstrate that the CT→T1 electron transfer is enhanced by the stronger CT interaction and a minimal energetic driving force (<0.1 eV), which is explained using the Marcus theory with a small reorganization energy of <0.1 eV. Through our analysis, a novel donor-acceptor combination for the OLED is developed and shows an efficient blue emission with an extremely low turn-on voltage of 1.57 V. This work provides a solution to control interfacial CT state toward efficient optoelectronic devices without energy loss.

Visible-Light-Induced Reductive Coupling of Arylacetylenes with Benzothiazole Sulfones.

In this study, we propose heavy-metal-free reductive coupling of arylacetylenes with benzothiazole sulfones. The reactions of alkyl or benzylic benzothiazole sulfones with arylacetylenes are successfully performed in the presence of Hantzsch esters and K2CO3 under visible-light irradiation to afford 1,2-disubstituted alkenes in moderate to good yields, with Z-isomer as the major product. The utility of this protocol is expanded to α-deuterative coupling using a deuterated Hantzsch ester, furnishing the corresponding alkenes with high deuterium incorporation.

5,11-Diazadibenzo[hi,qr]tetracene: Synthesis, Properties, and Reactivity toward Nucleophilic Reagents.

5,11-Diazadibenzo[hi,qr]tetracene was synthesized as a new nitrogen-substituted polycyclic heteroaromatic compound by Pd-catalyzed cycloisomerization of an alkyne precursor followed by oxidative cyclization with bis(trifluoroacetoxy)iodobenzene. The substitution of imine-type nitrogen atoms significantly enhanced its electron-accepting character and facilitated the direct nucleophilic addition of arylamines under strongly basic conditions to afford the desired amino-substituted products. The introduction of amino groups induced a remarkable red-shift in their absorption spectra; the tetrasubstituted product exhibited intense near-infrared absorbing property. Furthermore, the π-electronic system, which includes a redox-active 1,4-diazabutadiene moiety, underwent reversible interconversion to its corresponding reduced form upon reduction with NaBH4 and aerobic oxidation.

Influence of N-Substituents on Photovoltaic Properties of Singly Bay-Linked Dimeric Perylene Diimides.

The influence of N-substituents on the photovoltaic properties of singly bay-linked perylene diimides (diPDIs) was systematically investigated to understand the aromatic-aliphatic balance, which is beneficial for achieving high device performance in organic photovoltaic (OPV) systems. The synthesis of various N-substituted diPDIs was successfully achieved using a newly developed one-step procedure, resulting in sufficiently high yields. Detailed investigations of seven variants of diPDIs demonstrated that the primary alkyl substituents, particularly the 2-ethylhexyl group, induce the self-organized growth of thin films with high crystallinity. This is beneficial for enhancing the device performance of bulk heterojunction (BHJ) systems. The results presented herein reveal the important roles of alkyl side chains as hydrophobic solubilizing auxiliaries or primary determinants in the control of the active layer nanomorphology. This offers a valuable guideline that is essential for developing high-performance organic semiconductor materials for future practical applications.

[Resection of Anterior Mediastinal Tumor Followed by Left Brachiocephalic Vein Reconstruction;Report of a Case].

A 65-year-old man was referred to our hospital because of an abnormal shadow on a chest radiogram. Swelling of the face and upper limbs were noted. Enhanced computed tomography showed a 62×101 mm mass in the anterior mediastinum with invasion to the superior vena cava (SVC) and the right upper lobe of the lung. Surgical resection through a sternotomy was performed. The mediastinal tumor was resected along with the left brachiocephalic vein, the part of SVC wall and the partial right upper lobe of the lung with a clamp on the proximal SVC, followed by a left brachiocephalic vein reconstruction. There has been no evidence of recurrence after 1 year. This procedure may be an efficacious technical option in case of anterior mediastinal invasive tumor.

Porphyrin-Stabilized Nitrenium Dication.

An azepine-fused NiII -porphyrin dimer was synthesized by oxidative amination of ß-ß linked NiII -porphyrin dimer, and its N-aryl congener was synthesized by twofold Buchwald-Hartwig amination of ß-to-ß linked and dichlorinated NiII -porphyrin dimer. Oxidation of the NH congener gave neutral aminyl radical and nitrenium ion successively in a similar manner to the previously reported NH-bridged NiII -porphyrin dimer. Oxidation of the N-aryl congener afforded formal nitrenium dication in a single-step two-electron oxidation. Stable nitrenium dications that are isoelectronic to neutral trivalent boron compounds and tertiary carbocations are rare. The chemical stability of the nitrenium dication was improved by chlorine substitution at the most reactive ß-position. The structural, optical, magnetic, electrochemical properties of these compounds were fully characterized.

Selective Formation of Helical Tetrapyrrin-Fused Porphyrins by Oxidation of ß-to-ß Linked meso-Aminoporphyrin Dimers.

Oxidation of ß-to-ß directly linked and sulfur-bridged meso-amino NiII -porphyrin dimers with PbO2 gave helical tetrapyrrin (biliverdin analogue)-fused NiII -porphyrins. These ring cleaving reactions differ markedly from the previously reported oxidation of a ß-ß linked NiII -porphyrin dimer carrying one amino group, which gave an azepine-fused porphyrin dimer. The tetrapyrrin-fused NiII -porphyrins display intense NIR absorption bands at 1200-1400 nm and reversible redox processes because of the highly π-conjugated networks and rigid structures. These tetrapyrrin-fused NiII -porphyrins were separated to stable enantiomers, which showed clear Cotton effects in their CD spectra with Δϵ of 102 order.

Triplet-Triplet Annihilation-Based Upconversion Sensitized by a Reverse Micellar Assembly of Amphiphilic Ruthenium Complexes.

We have developed a new photon upconversion (UC) system utilizing a new amphiphilic sensitizer 1a that comprises a hydrophilic ruthenium complex and a lipophilic bisanthracene appendage. At concentrations higher than 5 µM in toluene, the sensitizer 1a formed a reverse micellar assembly which facilitated the triplet sensitization of 9,10-diphenylanthracene (DPA) more efficiently than homogeneously dispersed solutions to enhance the UC efficiency up to 38.2%. The Stern-Volmer analyses revealed the stepwise triplet-triplet energy transfers (TTET): (1) intramicellar energy transfer from the ruthenium core to the bisanthracene surface and (2) diffusion-dependent energy transfer from the surface to DPA. On these bases, it can be assumed that the reverse micellar assemblies accelerate the former TTET process to enhance the UC efficiency.

A 1,5-Naphthyridine-Fused Porphyrin Dimer: Intense NIR Absorption and Facile Redox Interconversion with Its Reduced Congener.

PtII -catalyzed cyclization of ß-to-ß ethynylene-bridged meso-amino NiII porphyrin dimer 4 followed by oxidation with PbO2 afforded 1,5-naphthyridine-fused porphyrin dimer 5 in good yield. This dimer possesses a redox-active 1,4-diazabutadiene linkage that is interconvertible with its reduced 1,2-diaminoethene linkage upon treatments with NaBH4 or PbO2 . The dimer 5 exhibits an intense NIR absorption and a narrow HOMO-LUMO gap with a remarkably low reduction potential mainly due to effective bonding interactions in the LUMO through the 1,4-diazabutadiene linkage. In contrast, the reduced dimer 7 is fairly electron-rich with high HOMO energy and shows a relatively large HOMO-LUMO gap compared to that of 5.

meso-Functionalization of Boron(III) Subporphyrin with Boron(III) meso-Lithiosubporphyrin.

Boron(III) meso-lithiosubporphyrin was prepared by bromine-lithium exchange of B-tolyl BIII meso-bromosubporphyrin with n-butyllithium at -98 °C. The resulting subporphyrinyllithium was treated with various electrophiles such as benzophenone, N,N-dimethylformamide, CO2 , chlorotrimethylsilane, N-fluorobenzenesulfonimide, and dimesitylboryl fluoride to give the corresponding meso-functionalized BIII subporphyrins. The nucleophile was also used to construct BIII subporphyrin dimers such as bis(BIII subporphyrinyl)ketone, bis(BIII subporphyrinyl)carbinol, and disilane-bridged BIII subporphyrin dimer. The structural, optical, and electrochemical properties of these meso-functionalized BIII subporphyrins were examined by UV/Vis absorption and fluorescence spectroscopy, electrochemical studies, and DFT calculations.

Stable Diporphyrinylaminyl Radical and Nitrenium Ion.

Nitrenium ions, isoelectronic nitrogen counterparts of carbenes, are important intermediates in various biological and chemical processes. Herein we describe the first synthesis and characterization of a stable nitrenium ion without resonance stabilization by adjoining amino groups. Namely, a stable salt of a diporphyrinylnitrenium ion was synthesized by stepwise oxidation of the corresponding diporphyrinylamine through a stable aminyl radical. The nitrenium ion exhibits characteristic features such as a singlet ground state, enhanced double-bond character of the central C-N bonds, no reactivity toward water and methanol, and negative solvatochromic behavior.

Diphenylphosphine-Oxide-Fused and Diphenylphosphine-Fused Porphyrins: Synthesis, Tunable Electronic Properties, and Formation of Cofacial Dimers.

Diphenylphosphine-oxide-fused NiII porphyrin 8 was synthesized from 3,5,7-trichloroporphyrin 5 via a reaction sequence of nucleophilic aromatic substitution with lithium diphenylphosphide, oxidation with H2 O2 , and palladium-catalyzed intramolecular cyclization. Reduction of 8 with HSiCl3 gave diphenylphosphine-fused NiII porphyrin 9. The embedded P=O and P moieties serve as a strong electron-accepting and electron-donating group to perturb the optical and electrochemical properties of the NiII porphyrin. NiII porphyrin 9 is diamagnetic with a low-spin NiII center in solution but becomes paramagnetic with a five-coordinated NiII center with high-spin (S=1) state in the solid state. Diphenylphosphine-oxide-fused ZnII porphyrin 10 was also synthesized and shown to form a face-to-face dimer with mutual O-Zn bonds in the crystal and in nonpolar and moderately polar solvents. The dimerization of 10 in CDCl3 has been revealed to be an entropy-driven process with a large entropy gain (ΔSD =207 J K-1 mol-1 ).

[Malignant Pleural Mesothelioma Presenting Refractory Pneumothorax Successfully Treated by Intrapleural Administration of Diluted Fibrin Glue;Report of a Case].

Malignant pleural mesothelioma sometimes accompanies intractable neumothorax due to the visceral pleural invasion of the tumor. A 68-years-old man was found to have massive pleural effusion and pleural mass combined with pneumothorax by computed tomography(CT). CT guided biopsy revealed the mass to be malignant pleural mesothelioma. Since continuous air leakage was observed by chest drainage, pleurodesis by OK-432 twice and bronchial occlusion by Endobronchial Watanabe Spigot (EWS)were performed. But air leakage continued, and the surgery was performed, however the treatment failed to stop the air leakage. Finally, the intrapleural administration of diluted fibrin glue was challenged and the air leakage stopped immediately after the treatment.

Metal-Free Approach to Biaryls from Phenols and Aryl Sulfoxides by Temporarily Sulfur-Tethered Regioselective C-H/C-H Coupling.

We have developed metal-free regiocontrolled dehydrogenative C-H/C-H cross-coupling of aryl sulfoxides with phenols by means of trifluoroacetic anhydride. Because the reaction would proceed through an interrupted Pummerer reaction followed by sulfonium-tethered [3,3]-sigmatropic rearrangement, the C-H/C-H coupling takes place exclusively between the ortho positions of both substrates. Various functional groups including carbonyl, halo, siloxy, and even boryl moieties are compatible. The biaryl products naturally possess hydroxy and sulfanyl groups, which allows the products to be useful synthetic intermediates, as evidenced by the syntheses of π-expanded heteroarenes such as unprecedented 7,12-dioxa[8]helicene.

Directly Diphenylborane-Fused Porphyrins.

Mono- and bis(diphenylborane)-fused porphyrins were synthesized from the corresponding ß-(2-trimethylsilylphenyl)-substituted porphyrins through the sequence of Si-B exchange reaction, intramolecular bora-Friedel-Crafts reaction, and ring-closing Si-B exchange reaction. Effective electronic interactions of the empty p-orbital of the boron atom with the porphyrin π-circuit lead to red-shifted absorption spectra and substantially decreased LUMO energy levels. Pyridine adds at the boron center to cause disruption of the electronic interaction of the boron atom with large association constants (1.9-17×10(4) m(-1)) depending on the central metal at the porphyrin. The Zn(II) complex behaved as a hetero-dinuclear Lewis acid, exhibiting regioselective binding of pyridines at the boron or the zinc center.

Porphyrinylboranes Synthesized via Porphyrinyllithiums.

As the most nucleophilic porphyrins, meso- or ß-lithiated porphyrins were generated by iodine-lithium exchange reactions of the corresponding iodoporphyrins with n-butyllithium at -98 °C. Porphyrinyllithiums thus prepared were used for synthesis of dimesitylporphyrinylboranes through reactions with fluorodimesitylborane. The boryl groups proved to serve as an electron-accepting unit to alter the photophysical and electrochemical properties. In addition, 5-diarylamino-15-dimesitylboryl-substituted donor-accepter porphyrins showed increased intramolecular charge-transfer character in the S1 state. Furthermore, the reaction of ß-lithiated porphyrin with dichloromesitylborane provided a boron-bridged porphyrin dimer, which exhibited a conjugative interaction between two porphyrin units through the vacant p-orbital on the boron center.

Peripherally Silylated Porphyrins.

Silylation of peripherally lithiated porphyrins with silyl electrophiles has realized the first synthesis of a series of directly silyl-substituted porphyrins. The meso-silyl group underwent facile protodesilylation, whereas the ß-silyl group was entirely compatible with standard work-up and purification on silica gel. The meso-silyl group caused larger substituent effects to the porphyrin compared with the ß-silyl group. Silylation of ß-lithiated porphyrins with 1,2-dichlorodisilane furnished ß-to-ß disilane-bridged porphyrin dimers. A doubly ß-to-ß disilane-bridged Ni(II)-porphyrin dimer was also synthesized from a ß,ß-dilithiated Ni(II)-porphyrin and characterized by X-ray crystallographic analysis to take a steplike structure favorable for interporphyrinic interaction. Denickelation of ß-silylporphyrins was achieved upon treatment with a 4-tolylmagnesium bromide to yield the corresponding freebase porphyrins.

Synthesis and catalytic activities of porphyrin-based PCP pincer complexes.

2,18-Bis(diphenylphosphino)porphyrins undergo peripheral cyclometalation with group 10 transition-metal salts to afford the corresponding porphyrin-based PCP pincer complexes. The porphyrinic plane and the PCP-pincer unit are apparently coplanar, with small strain. The catalytic activities of the porphyrin-based pincer complexes at the periphery were investigated in the allylation of benzaldehyde with allylstannane and in the 1,4-reduction of chalcone to discover the electronic interplay between the inner metal and the outer metal in catalysis.

Synthesis of direct ß-to-ß linked porphyrin arrays with large electronic interactions: branched and cyclic oligomers.

Direct ß-to-ß linked branched and cyclic porphyrin trimers and pentamers have been synthesized by the Suzuki-Miyaura coupling of ß-borylporphyrins and ß-bromoporphyrins. The cyclic porphyrin trimer, the smallest directly linked cyclic porphyrin wheel to date, and its twined pentamer, exhibit small electrochemical HOMO-LUMO gaps, broad nonsplit Soret bands, and red-shifted Q-bands, thus indicating large electronic interactions between the constituent porphyrin units.

Wavily Curved Perylene Diimides: Synthesis, Characterization, and Photovoltaic Properties.

Solubility enhancement is a key issue for developing the perylene diimide-based functional materials. Introduction of curved structure proved an effective solubilizing method without employing steric repulsion. In this work, wavily curved perylene diimides were developed as a new family of highly soluble curved perylene diimides. Moreover, their conformational dynamics, aggregating properties, electronic properties, and photovoltaic performances were thoroughly examined in comparison to the previously reported isomer exhibiting an arched curvature. The waved isomer demonstrated heightened rigidity and a greater propensity for aggregation compared to the arched isomer, likely attributed to its more planar structure. Each benzoxepin unit played a role in cancelling out the curvature on the opposite side. While the difference in the molecular curvature did not cause significant alterations in the photophysical and electron-accepting properties, we identified that the modulation of the curved structure is effective in controlling the morphology of the photoelectric conversion layer.