Bowl-Shaped Kekulene Analogues: Cycloarenes with two Five-Membered Rings.

Kekulene, a cycloarene composed of 12 fused benzene rings in a circular arrangement, exhibits a highly planar and robust structure. Kekulene has been the subject of investigation into its aromaticity and electronic structure, particularly in relation to the cyclic benzenoid. We have successfully synthesized novel bowl-shaped kekulene analogues with five-membered rings incorporated into the kekulene structure. The results of DFT calculations and VT-NMR spectra indicate that inversion of their concave-convex structures occurs at room temperature. The NICS and AICD plots predict that the Clar's type resonance structure is found in a manner analogous to the pristine kekulene, albeit with the interruption of the π-conjugation on the sp3 carbons at the five-membered rings. Despite the presence of the Clar's resonance structure, the Diels-Alder reaction proceeded smoothly with a dienophile, in contrast to the behavior of planar kekulene derivatives. This study will lead to the creation of novel bowl-shaped compounds and development of reactivity in aromatic compounds.

Quantitative Analysis of Photochemical Reactions in Pentacene Precursor Films.

On-surface reactions are rapidly gaining attention as a chemical technique for synthesizing organic functional materials, such as graphene nanoribbons and molecular semiconductors. Quantitative analysis of such reactions is essential for fabricating high-quality film structures, but until our recent work using p-polarized multiple-angle incidence resolution spectrometry (pMAIRS), no analytical technique is available to quantify the reaction rate. In the present study, the pMAIRS technique is employed to analyze the photochemical reaction from 6,13-dihydro-6,13-ethanopentacene-15,16-dione to pentacene in thin films. The spectral analysis on a pMAIRS principle readily reveals the photoconversion rate accurately without other complicated calculations. Thus, this study underlines that the pMAIRS technique is a powerful tool for quantitative analysis of on-surface reactions, as well as molecular orientation.

Conflicting Aromaticity in Trirhodium(I) Rosarin.

Aromaticity is one of the most important and widely used concepts in chemistry. Among the various experimentally discovered and theoretically predicted compounds that possess different types of aromaticity, conflicting aromaticity, where aromatic and antiaromatic electron delocalization is present in one molecule simultaneously, remains one of the most controversial and elusive concepts, although theoretically predicted 15 years ago. In this work, we synthesized a novel conflicting aromatic trirhodium complex that contains a σ-aromatic metal fragment surrounded by the π-antiaromatic organic ligand and characterized it by nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry, and X-ray single crystal structure analysis. Experimental characterization and quantum chemical calculations confirm the unique conflicting aromaticity of the synthesized trirhodium molecule. Thus, this novel conflicting aromatic molecule expands the family of aromatic compounds. This discovery will enable researchers to develop and understand the phenomena of conflicting aromaticity in chemistry.

One-Dimensionally Arranged Quantum-Dot Superstructures Guided by a Supramolecular Polymer Template.

Colloidal quantum dots (QDs) exhibit important photophysical properties, such as long-range energy diffusion, miniband formation, and collective photoluminescence, when aggregated into well-defined superstructures, such as three-dimensional (3D) and two-dimensional (2D) superlattices. However, the construction of one-dimensional (1D) QD superstructures, which have a simpler arrangement, is challenging; therefore, the photophysical properties of 1D-arranged QDs have not been studied previously. Herein, we report a versatile strategy to obtain 1D-arranged QDs using a supramolecular polymer (SP) template. The SP is composed of self-assembling cholesterol derivatives containing two amide groups for hydrogen bonding and a carboxyl group as an adhesion moiety on the QDs. Upon mixing the SP and dispersed QDs in low-polarity solvents, the QDs self-adhered to the SP and self-arranged into 1D superstructures through van der Waals interactions between the surface organic ligands of the QDs, as confirmed by transmission electron microscopy. Furthermore, we revealed efficient photoinduced fluorescence resonance energy transfer between the 1D-arranged QDs by an in-depth analysis of the emission spectra and decay curves.

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments.

The "precursor approach" has proved particularly valuable for the preparation of insoluble and unstable π-conjugated polycyclic compounds (π-CPCs), which cannot be synthesized via in-solution organic chemistry, for their improved processing, as well as for their electronic investigation both at the material and single-molecule scales. This method relies on the synthesis and processing of soluble and stable direct precursors of the target π-CPCs, followed by their final conversion in situ, triggered by thermal activation, photoirradiation or redox control. Beside well-established reactions involving the elimination of carbon-based small molecules, i.e., retro-Diels-Alder and decarbonylation processes, the late-stage extrusion of chalcogen fragments has emerged as a highly promising synthetic tool to access a wider variety of π-conjugated polycyclic structures and thus to expand the potentialities of the "precursor approach" for further improvements of molecular materials' performances. This review gives an overview of synthetic strategies towards π-CPCs involving the ultimate elimination of chalcogen fragments upon thermal activation, photoirradiation and electron exchange.

Possibilities and Limitations in Monomer Combinations for Ternary Two-Dimensional Covalent Organic Frameworks.

The diversity and complexity of covalent organic frameworks (COFs) can be largely increased by incorporating multiple types of monomers with different topologies or sizes. However, an increase in the number of monomer types significantly complicates the COF formation process. Accordingly, much remains unclear regarding the viability of monomer combinations for ternary or higher-arity COFs. Herein, we show that, through an extensive examination of 12 two-nodes-one-linker ([2 + 1]) combinations, monomer-set viability is determined primarily by the conformational strain originating from disordered monomer arrangements, rather than other factors such as the difference in COF formation kinetics between monomers. When monomers cannot accommodate the strain associated with the formation of a locally disordered, yet crystalline framework, the corresponding [2 + 1] condensation yields a mixture of different COFs or an amorphous polymer. We also demonstrate that a node-linker pair that does not form a binary COF can be integrated to generate a single-phase framework upon addition of a small amount of the third component. These results will clarify the factors behind the successful formation of multicomponent COFs and refine their design by enabling accurate differentiation between allowed and disallowed monomer combinations.

An Atropisomerism Study of Large Cycloarylenes: [n]Cyclo-4,10-Pyrenylenes' Case.

An atropisomerism of large cycloarylenes was studied using [n]cyclo-4,10-pyrenylenes (n=6-21) as an illustrative example with two simple assumptions: (1) alternating configurations (R,S,R,S,…) are thermodynamically most stable, and (2) three consecutive identical configurations (R,R,R or S,S,S) are prevented. Ni-mediated coupling of a 5,9-diiodopyrene gave a series of directly-linked cyclic pyrene oligomers in one-pot reaction. As-synthesized cyclic hexamer was assigned as an (R,S,S,R,R,S) structure, converted into an (R,S,R,S,R,S)-form upon heating. Cyclic heptamer consists of two types of C2 symmetric structures predicted from assumption (2), one of which was convergent to one another by heating. Three atropisomers of cyclic octamer were analyzed from the possible five candidates by means of 1 H nuclear magnetic resonance (NMR) spectroscopy, and the conversion process to (R,S,R,S,R,S,R,S) configurations upon heating was investigated. In total, according to two simple rules, the analysis of atropisomerism could be performed smoothly.

Highly Robust and Antiaromatic Rhenium(I) Rosarin.

1ReH•Cl, a highly robust and antiaromatic rhenium(I) complex of triarylrosarin, is synthesized. The 1H NMR spectrum of 1ReH•Cl shows upfield-shifted pyrrole protons and highly downfield-shifted inner protons that confirm its antiaromatic nature, with density functional theory calculations strongly supporting this interpretation. Antiaromatic 1ReH•Cl absorbs from the UV to near-IR region of the optical spectrum; cyclic voltammetry, thin-layer UV-vis spectroelectrochemistry, and spin-density distributions clearly reveal that the rosarin backbone of 1ReH•Cl undergoes redox chemistry. The X-ray structure of 1ReH•Cl shows a fully coordinated and protonated inner cavity that effectively prevents proton-coupled electron transfer when treated with an acid. A remarkably negative NICS(0) value, clockwise anisotropy of the induced current density ring current, and the aromatic shielded inner cavity in the 2D ICSS(0) map reveal that the T1 state of 1ReH•Cl is aromatic based on Baird's rule.

Intraoperative Three-Dimensional Fluorescein Angiography-Guided Pars Plana Vitrectomy for the Treatment of Proliferative Diabetic Retinopathy: The Maximized Utility of the Digital Assisted Vitrectomy.

PURPOSE: To show the usefulness of the intraoperative three-dimensional fluorescein angiography (3D-FA)-guided pars plana vitrectomy. METHODS: The NGENUITY 3D visualization system was used for the digital assisted vitrectomy. Three-dimensional fluorescein angiography-guided pars plana vitrectomy was performed in three patients with vitreous hemorrhage secondary to proliferative diabetic retinopathy. We investigated both whether several angiographic findings can be successfully displayed on the screen during 3D-FA and whether pars plana vitrectomy can be performed simultaneously on the same screen while implementing 3D-FA. RESULTS: In all cases, the abnormal FA findings including hypofluorescence due to non-perfusion areas, and the hyperfluorescence due to macular edema and fibrovascular proliferative membrane were successfully displayed on the screen. The segmentation and delamination of fibrovascular proliferative membrane and panretinal photocoagulation for detected non-perfusion areas were able to be performed on the same screen while implementing 3D-FA. CONCLUSION: Three-dimensional fluorescein angiography-guided pars plana vitrectomy is a novel approach that fully utilizes the advantages of digital assisted vitrectomy and a promising option for the treatment of proliferative diabetic retinopathy.

Enhanced Four-Electron Oxygen Reduction Selectivity of Clamp-Shaped Cobalt(II) Porphyrin(2.1.2.1) Complexes.

The molecular structure, electrochemistry, spectroelectrochemistry and electrocatalytic oxygen reduction reaction (ORR) features of two CoII porphyrin(2.1.2.1) complexes bearing Ph or F5 Ph groups at the two meso-positions of the macrocycle are examined. Single crystal X-ray analysis reveal a highly bent, nonplanar macrocyclic conformation of the complex resulting in clamp-shaped molecular structures. Cyclic voltammetry paired with UV/Vis spectroelectrochemistry in PhCN/0.1 M TBAP suggest that the first electron addition corresponds to a macrocyclic-centered reduction while spectral changes observed during the first oxidation are consistent with a metal-centered CoII /CoIII process. The activity of the clamp-shaped complexes towards heterogeneous ORR in 0.1 M KOH show selectivity towards the 4e- ORR pathway giving H2 O. DFT first-principle calculations on the porphyrin catalyst indicates a lower overpotential for 4e- ORR as compared to the 2e- pathway, consistent with experimental data.

Microscopic Structures, Dynamics, and Spin Configuration of the Charge Carriers in Organic Photovoltaic Solar Cells Studied by Advanced Time-Resolved Spectroscopic Methods.

Organic photovoltaics (OPVs) are promising solutions for renewable energy and sustainable technologies and have attracted much attention in recent years. Two types of organic semiconductors are used as donor materials to fabricate OPV cells. One type is a photoconductive polymer, and the other type is a small-molecule-based compound. The discovery of a bulk-heterojunction (BHJ) structure using a mixture of p- and n-type organic semiconductors has dramatically increased the power conversion efficiency (PCE) of OPV cells. In this feature article, we review our recent studies on organic BHJ thin films and OPVs by using advanced time-resolved spectroscopic techniques. Two topics regarding the microscopic behaviors of the charge carriers are discussed. The first topic is focused on how to quantify the local mobility of the charge carriers. Here, we discuss charge carrier dynamics in diketopyrrolopyrrole-linked tetrabenzoporphyrin (DPP-BP) BHJ thin films studied by time-resolved terahertz spectroscopy on a subpicosecond to several tens of picoseconds time scale and by transient photocurrent measurements on a microsecond time scale. The second topic concerns the spin configuration and interaction of the electron and hole of the polaron pairs in polymer-based BHJ thin films and OPV cells studied by the time-resolved electron paramagnetic resonance method, time-resolved simultaneous optical and electrical detection, and measurement of the magnetoconductance effect.

Synthesis of oligoacenes using precursors for evaluation of their electronic structures.

Acenes, which are hydrocarbons comprising linearly fused benzene rings, have attracted considerable attention owing to their electronic structures and utility as organic electronic materials. However, the ease with which oligoacenes undergo oxidation increases with the number of linearly fused benzene rings owing to the increased energy of the highest occupied molecular orbital. The synthesis of naked oligoacenes with seven or more benzene rings is difficult because their open-shell structure renders them unstable. The recent development of a precursor method has enabled the in situ synthesis of oligoacenes under specific conditions and the spectroscopic observation of oligoacene in single crystals, in film matrices and under cryogenic conditions. Scanning tunneling microscopy and non-contact atomic force microscopy under ultra-high vacuum conditions have also made significant advances in the study of oligoacenes and oligoazaacenes. This paper reviews the recent progress in the synthesis of oligoacenes using precursors, with a particular focus on the chemical structures, synthesis, and reactivity of the precursors. The electronic properties of oligoacenes are also discussed in relation to the number of fused benzene rings, including their energy levels and spin states. These results will contribute to the synthesis and development of carbon nanomaterials with applications in the field of organic electronics.

Synthesis, Characterization, and Electrochemistry of Copper Dibenzoporphyrin(2.1.2.1) Complexes.

Three copper dibenzoporphyrin(2.1.2.1) complexes having two dipyrromethene units connected through o-phenylen bridges and 4-MePh, Ph, or F5Ph substituents at the meso positions of the dipyrrins were synthesized and characterized according to their spectral, electrochemical, and structural properties. As indicated by the single-crystal X-ray structures, all three derivatives have highly bent molecular structures, with angles between each planar dipyrrin unit ranging from 89° to 85°, indicative of a nonaromatic molecule. The insertion of copper(II) into dibenzoporphyrins(2.1.2.1) induced a change in the macrocyclic cavity shape from rectangular in the case of the free-base precursors to approximately square for the metalated copper derivatives. Solution electron paramagnetic resonance (EPR) spectra at 100 K showed hyperfine coupling of the Cu(II) central metal ion and the N nucleus in the highly bent molecular structures. Electrochemical measurements in CH2Cl2 or N,N-dimethylformamide (DMF) containing 0.1 M tetrabutylammonium perchlorate (TBAP) were consistent with ring-centered electron transfers and, in the case of reduction, were assigned to electron additions involving two equivalent π centers on the bent nonaromatic molecule. The potential separation between the two reversible one-electron reductions ranged from 230 to 400 mV in DMF, indicating a moderate-to-strong interaction between the equivalent redox-active dipyrrin units of the dibenzoporphyrins(2.1.2.1). The experimentally measured highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps ranged from 2.14 to 2.04 eV and were smaller than those seen for the planar copper tetraarylporphyrins(1.1.1.1), (Ar)4PCu.

INTRAOPERATIVE OPTICAL COHERENCE TOMOGRAPHY FOR REAL-TIME VISUALIZATION OF THE POSITIONAL RELATIONSHIP BETWEEN BUCKLING MATERIAL AND RETINAL BREAKS DURING SCLERAL BUCKLING FOR RHEGMATOGENOUS RETINAL DETACHMENT.

PURPOSE: To report the usefulness of a new surgical method using intraoperative optical coherence tomography that can more accurately place the buckling material for scleral buckling using a noncontact wide-angle viewing system with a cannula-based chandelier endoilluminator for the treatment of rhegmatogenous retinal detachment. METHODS: The medical records of 12 eyes of 11 patients with rhegmatogenous retinal detachment treated with scleral buckling combined with real-time intraoperative optical coherence tomography observation were retrospectively reviewed. RESULTS: Real-time observations of the positional relationship between the protrusion of buckling material and retinal breaks with intraoperative optical coherence tomography revealed that retinal breaks were not properly placed on the protrusion of the buckling material in five eyes, requiring the intraoperative repositioning of the buckling material. Eventually, the scleral buckling combined with real-time intraoperative optical coherence tomography observation yielded the initial anatomical success rates of 100% without noteworthy intraoperative or postoperative complications. CONCLUSION: This procedure is a novel approach that enables safer and more accurate placement of the buckling material and may contribute to improving the outcomes of scleral buckling in the future.

Binuclear Rhodium(I) Complex of a Dimethylvinylene-Bridged Distorted Hexaphyrin(2.1.2.1.2.1).

A highly distorted binuclear rhodium(I) complex, 2Rh, was successfully synthesized from hexaphyrin(2.1.2.1.2.1) containing dimethylvinylene-bridges between dipyrrin units. IR spectroscopy, 1H NMR spectroscopy, and X-ray crystallography revealed that the complex 2Rh consists of two rhodium(I) ions coordinated to two dipyrrin units. Rh complexation induced a transformation from a trans-/cis-/trans- to trans-/cis-/cis-conformation on the dimethylvinylene-bridges. This is the first example of rhodium(I)-ion-induced cis-/trans-isomerization in the porphyrin derivatives. Theoretical calculations of 2Rh predicted the presence of intramolecular charge-transfer absorption due to the distorted molecular structure.

LONG-TERM EFFECT OF CYSTOTOMY WITH OR WITHOUT THE FIBRINOGEN CLOT REMOVAL FOR REFRACTORY CYSTOID MACULAR EDEMA SECONDARY TO DIABETIC RETINOPATHY.

PURPOSE: To show the long-term effect of cystotomy with or without fibrinogen clot removal for refractory cystoid macular edema secondary to diabetic retinopathy. METHODS: Retrospective analyses of the medical records of 30 eyes of 30 patients with refractory cystoid macular edema secondary to diabetic retinopathy who had followed up for 12 months after the surgery were performed. RESULTS: There were 15 men and 15 women. The mean ± SD age was 68.4 ± 7.9 years. The best-corrected visual acuity (logarithm of the minimal angle of resolution) at 12 months after the surgery (0.33 ± 0.25, Snellen equivalent, 20/42) was statistically better than the preoperative best-corrected visual acuity (0.45 ± 0.33, Snellen equivalent, 20/56) (P < 0.01). The central sensitivity on microperimetry (dB) was not statistically changed between preoperatively (24.0 ± 4.9) and 12 months after the surgery (24.1 ± 4.0) (P = 0.75). The central retinal thickness on optical coherence tomography (µm) at 12 months after the surgery (300.3 ± 99.0) was statistically improved compared with the preoperative central retinal thickness (565.6 ± 198.7) (P < 0.01). During the follow-up period, cystoid macular edema relapsed in seven of 30 eyes. The preoperative cystoid cavity reflectivity on optical coherence tomography in patients with fibrinogen clot removal (n = 16) was significantly higher than that in patients without fibrinogen clot removal (n = 14) (P < 0.04). CONCLUSION: The cystotomy with or without fibrinogen clot removal may be a promising treatment option for refractory cystoid macular edema secondary to diabetic retinopathy.

Improvement of visual function and ocular and systemic symptoms following blepharoptosis surgery.

Purpose: To study the changes of the visual function and ocular and systemic symptoms following blepharoptosis surgery.Methods: Seventy-eight involutional blepharoptosis patients (72.1 ± 6.4 years) underwent levator advancement procedure. Before and at 2 months after the surgery, OPD-Scan III (Nidek) was used to measure corneal astigmatism, total higher order aberrations (HOAs), and area ratio (AR), an index of the objective contrast sensitivity. FVA-100 (Nidek) was used to determine the functional visual acuity (FVA) and visual maintenance ratio (VMR). The ocular and systemic symptoms were also determined by a questionnaire using visual analogue scale (VAS) scores.Results: Before surgery, the corneal astigmatism, HOAs, AR, FVA, and VMR were 1.56 ± 0.52 diopters (D), 0.23 ± 0.24 µm, 14.8 ± 4.2%, 0.68 ± 0.32 logMAR units and 0.76 ± 0.06, respectively. After surgery, these values were 1.29 ± 0.41 D, 0.19 ± 0.21 µm, 18.6 ± 3.4%, 0.31 ± 0.18 logMAR units and 0.88 ± 0.03, respectively. Corneal astigmatism and HOAs were significantly reduced after surgery (P=0.007 and P=0.023, paired t test, respectively), and AR, FVA and VMR were significantly improved after surgery (P=0.033, P=0.012 and P=0.016, respectively). The VAS scores significantly improved after surgery, and this improvement was positively and significantly correlated with the increase of the AR (r=0.421, P=0.003) and the VMR (r=0.497, P =0.005).Conclusions: Blepharoptosis surgery is visual functionally beneficial and can help to reduce the ocular and systemic symptoms.

Acridino[2,1,9,8-klmna]acridine Bisimides: An Electron-Deficient π-System for Robust Radical Anions and n-Type Organic Semiconductors.

We report the synthesis and properties of acridino[2,1,9,8-klmna]acridine bisimide (AABI), a nitrogen-doped anthanthrene with two imide functionalities. AABI exhibits excellent electron affinity as evident by its low-lying LUMO level (-4.1 eV vs. vacuum). Single-electron reduction of one AABI derivative afforded the corresponding radical anion, which was stable under ambient conditions. Photoconductivity measurements suggest that the intrinsic electron mobility of an N-phenethyl AABI derivative obeys a band-transport model. Accordingly, an electron mobility of 0.90 cm2 V-1 s-1 was attained with the corresponding single-crystal organic field-effect transistor (OFET) device. The vacuum-deposited OFET device consisting of a polycrystalline sample exhibited high electron mobility of up to 0.27 cm2 V-1 s-1 even in air. This study demonstrates that dual incorporation of both imide substituents and imine-type nitrogen atoms is an effective strategy to create novel electron-deficient π-systems.

Dinaphthothiepine Bisimide and Its Sulfoxide: Soluble Precursors for Perylene Bisimide.

The synthesis and properties of dinaphtho[1,8-bc:1',8'-ef]thiepine bisimide (DNTBI) and its oxides are described. Their molecular design is conceptually based on the insertion of a sulfur atom into the perylene bisimide (PBI) core. These sulfur-inserted PBI derivatives adopt nonplanar structures, which significantly increases their solubility in common organic solvents. Upon electron injection, light irradiation, or heating, DNTBI and its sulfoxides undergo sulfur extrusion reactions to furnish PBI. The photoinduced and thermal sulfur extrusion reactions proceed almost quantitatively. This unique reactivity enabled the fabrication of a high-performance solution-processed n-type organic field-effect transistor with an electron mobility of up to 0.41 cm2 V-1 s-1.

Visible-Light-Induced Heptacene Generation under Ambient Conditions: Utilization of Single-crystal Interior as an Isolated Reaction Site.

The photo-induced generation of unstable molecules generally requires stringent conditions to prevent oxidation and the concomitant decomposition of the products. The visible-light-induced conversion of two heptacene precursors to heptacene was studied. Single crystals of bis- and mono-α-diketone-type heptacene precursors (7-DK2 and 7-DK1, respectively), were prepared to investigate the effect of precursor structure on reactivity. The photoirradiation of a 7-DK2 single crystal cleaved only one α-diketone group, forming an intermediate bearing a pentacene subunit, while that of a 7-DK1 single crystal gave rise to characteristic absorption peaks of heptacene and their increase in intensity with photoirradiation time, indicating the generation of heptacene without decomposition. Heptacene production was not observed when the precursors were photoirradiated in solution, implying that the single crystal interior provided isolation from the external environment, thus preventing heptacene oxidation.