Triple Isomerism in 3D Covalent Organic Frameworks.

Isomerism in covalent organic frameworks (COFs) has scarcely been known. Here, for the first time we show 3D COFs with three framework isomers or polymorphs constructed from the same building blocks. All isomers were obtained as large (>10 µm) crystals; although their crystal shapes were distinctly different, they showed identical FT-IR and solid-state NMR spectra. Our structural analyses revealed unprecedented triple isomerism in 3D COFs (noninterpenetrated dia, qtz, and 3-fold interpenetrated dia-c3 nets). Furthermore, this Communication reports the first known COF with qtz topology for which the structure determination was based on Rietveld analysis. We achieved triple framework isomerism by reticulating a tetrahedral building block with a flexible junction and a linear building block with PEO side chains and by varying solution compositions. Our energy calculations, along with the discovery of interisomer transition, revealed that the isomer with qtz topology was a kinetic isomer. Thus, this simple yet little-explored concept of reticulating only flexible building blocks is an effective pathway to significantly broaden the diversity of 3D COFs, which have been proposed for a myriad of applications.

Peripheral Fusion of Carbon-Based Aromatic Rings to B4N4-Heteropentalene Leading to Close π-Stacking in the Solid State.

π-Electronic molecules with a BN-heterocyclic and carbon-based aromatic hybrid ring system (h-CBN) are interesting in that they potentially exhibit synergistic properties arising from the two different π-systems. Here we report the synthesis and properties of a h-CBN-type molecule (1) having a bicyclic B4N4-heteropentalene core fused with extended aromatic rings. This molecule exhibits excellent chemical stability despite the absence of bulky substituents for kinetic protection, which in turn provides effective stacking of the π-system upon crystallization. Depending on the crystallization solvent, 1 forms two polymorphs, i. e., the α- and ß-phases. While both phases have one-dimensional columnar structures, the π-stacking geometries associated with the transfer integrals of the frontier orbitals are different, resulting in a twofold difference in the electrical conducting properties. We also found that upon thermal vacuum deposition, 1 gives an amorphous film, which serves as a host material for a red phosphorescent OLED device (maximum external quantum efficiency: 15.5 and 13.3 % at 0.1 and 2.5 mA, respectively).

Phosphonic acid anchored tripodal molecular films on indium tin oxide.

Whereas monopodal self-assembling monolayers (SAMs) are most frequently used for surface and interface engineering, tripodal SAMs are less popular due to the difficulty in achieving a reliable and homogeneous bonding configuration. In this context, in the present study, the potential of phosphonic acid (PA) decorated triptycene (TripPA) for formation of SAMs on oxide substrates was studied, using indium tin oxide (ITO) as a representative and application-relevant test support. A combination of several complementary experimental techniques was applied and a suitable monopodal reference system, benzylphosphonic acid (PPA), was used. The resulting data consistently show that TripPA forms well-defined, densely packed, and nearly contamination-free tripodal SAMs on ITO, with the similar parameters and properties as the monopodal reference system. Modification of wetting properties and work function of ITO by non-substituted and cyano-decorated TripPA SAMs was demonstrated, showing a potential of this tripodal system for surface engineering of oxide substrates.

Conversion surgery for esophageal and esophagogastric junction cancer.

As a result of the recent advances in first-line treatment including chemotherapy, radiation therapy, targeted therapy, and immune checkpoint inhibitor immunotherapy (ICI) for locally advanced/metastatic initially unresectable esophageal and esophagogastric junction cancer, surgery aiming at cure after initial treatment, so-called "conversion surgery" has become more common in this field. Several studies have indicated encouraging survival outcomes for patients after conversion surgery with R0 resection. However, various issues, such the utility and the safety of conversion surgery remain unclear. In this review, we will focus on the surgical treatment for initially unresectable esophageal and esophagogastric junction cancer after first- or later- line treatment and review recent evidence regarding the safety and the efficacy of conversion surgery. Multidisciplinary treatment including surgery may serve as a novel treatment strategy for esophageal and esophagogastric junction cancer, thus provide a curative treatment option and potentially contribute to better prognosis for initially untreatable diseases.

Modification of the lesser curvature incision line enhanced gastric conduit perfusion as determined by indocyanine green fluorescence imaging and decreased the incidence of anastomotic leakage following esophagectomy.

AIM: This study aimed to investigate the effectiveness of a modified incision line on the lesser curvature for gastric conduit formation during esophagectomy in enhancing the perfusion of gastric conduit as determined by indocyanine green fluorescence imaging and reducing the incidence of anastomotic leakage. METHODS: A total of 272 patients who underwent esophagectomy at our institute between 2014 and 2022 were enrolled in this study. These patients were divided based on two different types of cutlines on the lesser curvature: conventional group (n = 141) following the traditional cutline and modified group (n = 131) adopting a modified cutline. Gastric conduit perfusion was assessed by ICG fluorescence imaging, and clinical outcomes after esophagectomy were evaluated. RESULTS: The distance from the pylorus to the cutline was significantly longer in the modified group compared with the conventional group (median: 9.0 cm vs. 5.0 cm, p < 0.001). The blood flow speed in the gastric conduit wall was significantly higher in the modified group than that in the conventional group (median: 2.81 cm/s vs. 2.54 cm/s, p = 0.001). Furthermore, anastomotic leakage was significantly lower (p = 0.024) and hospital stay was significantly shorter (p < 0.001) in the modified group compared with the conventional group. Multivariate analysis identified blood flow speed in the gastric conduit wall as the only variable significantly associated with anastomotic leakage. CONCLUSIONS: ICG fluorescence imaging is a feasible, reliable method for the assessment of gastric conduit perfusion. Modified lesser curvature cutline could enhance gastric conduit perfusion, promote blood circulation around the anastomotic site, and reduce the risk of anastomotic leakage after esophagectomy.

Insights into Thermal Transport through Molecular π-Stacking.

π-Stacking, which is a ubiquitous structural motif in assemblies of aromatic compounds, is well-known to provide a transport pathway for charge carriers and excitons, while its contribution to thermal transport is still unclear. Herein, based on detailed experimental observations of the thermal diffusivity, thermal conductivity, and specific heat of a single-crystalline triphenylene featuring a one-dimensionally π-stacked structure, we describe the nature of thermal transport through the π-stacked columns. We reveal that acoustic phonons are responsible for thermal transport through the π-stacked columns, which exhibit crystal-like behavior. Importantly, the thermal energy stored as intramolecular vibrations can also be transported by coupling to the acoustic phonons. In contrast, in the direction perpendicular to the π-stacked columns, an amorphous-like thermal transport behavior dominates. The present finding offers deep insight into nanoscale thermal transport in organic materials, where the constituent molecules exist as discrete entities linked together by weak intermolecular interactions.

Synthesis and Properties of B4 N4 -Heteropentalenes Fused with Polycyclic Hydrocarbons.

Hybrid molecules of π-conjugated carbon rings and BN-heterocyclic rings (h-CBNs) fused with each other have been a rare class of compounds due to the limited availability of their synthetic methods. Here we report the synthesis of new h-CBNs featuring a B4 N4 -heteropentalene core and polycyclic aromatic hydrocarbon wings. Using 1,2-azaborinine derivatives as a building block, we developed a rational synthetic protocol that allows the formation of a B4 N4 ring in a stepwise manner, resulting in the fully fused ABA-type triblock molecules. Thus, three derivatives of 1 bearing naphthalene (1Naph ), anthracene (1Anth ), or phenanthrene (1Phen ) wings fused with the B4 N4 core were synthesized and characterized. Among them, 1Phen , which displays the highest triplet-state energy, was found to serve a host material for phosphorescent OLED devices, for which a maximum external quantum efficiency of 13.7 % was recorded. These findings may promote the synthesis of various types of h-CBNs aiming at new properties arising from the synergy of two different π-electronic systems.

Effectiveness of computed tomography scoring for the early diagnosis of anastomotic leakage after esophagectomy.

PURPOSE: Anastomotic leakage after esophagectomy is associated with increased mortality; therefore, early diagnosis is highly important. This study aimed to identify the characteristic computed tomography (CT) findings of cervical anastomotic leakage after esophagectomy for esophageal cancer and evaluate the effectiveness of CT scoring in screening the anastomotic leakage. METHODS: Overall, 91 patients who underwent thoracoscopic esophagectomy with cervical esophago-gastric anastomosis were included. We investigated the correlation between anastomotic leakage and the presence of the microbubble sign, evident air retention, and fluid collection in the cervical and mediastinal regions. CT findings were scored, and the cutoff value was set to 2 points on the receiver operating characteristic curve. The patients were divided into two groups based on the CT score (≥ 2 points and ≤ 1 point). RESULTS: CT findings of the microbubble sign (p = 0.01; odds ratio [OR], 8.545; 95% confidence interval [CI], 1.596-45.73), cervical air retention (p < 0.01; OR, 12.43; 95% CI, 2.084-74.17), and cervical fluid collection (p < 0.01; OR, 9.359; 95% CI, 1.753-49.96) significantly correlated with anastomotic leakage. The ≥ 2-point CT score group showed a significantly higher incidence of anastomotic leakage than the ≤ 1-point group (p < 0.01; OR, 16.28; 95% CI [4.704-56.38]). A ≥ 2-point CT score had higher sensitivity (84.2%) than upper gastrointestinal series (36.8%). CONCLUSION: The presence of microbubble sign, air retention, and fluid collection in the cervical area correlated with anastomotic leakage after cervical anastomosis in thoracoscopic esophagectomy. CT scores are useful early anastomotic leakage detectors.

Capturing the Trajectory of Metal-Ion-Cluster Formation: Stepwise Accumulation of Zn(II) Ions in a Robust Coordination Space Formed by a Rigid Tridentate Carboxylate Ligand.

Organic ligand-directed synthesis of metal-ion clusters with a well-defined number and arrangement of metal ions is an important subject toward the development of functional inorganic-organic nanohybrids. Here we report the synthesis of multinuclear Zn-oxo clusters using a triptycene-based rigid ligand (H3L) featuring three metal-coordination sites arranged in a triangular shape. Upon complexation of H3L with zinc acetate dihydrate, a decanuclear Zn-oxo cluster and multinuclear Zn-oxo clusters with a smaller number of Zn(II) ions were formed as the final product and its intermediates, respectively. A comparison of the X-ray structure of the final product with those of the intermediates revealed the cluster-formation process, where four triptycene ligands preorganize to form a robust coordination space to which Zn(II) ions accumulate in a stepwise manner. This stepwise metal-ion accumulation, along with the formation of a large tetrahedral decanuclear Zn-oxo cluster, highlights the potential of ligand design using 1,8,13-substituted triptycenes for the development of various metal-ion clusters.

Understanding the evolution of the Raman spectra of molecularly p-doped poly(3-hexylthiophene-2,5-diyl): signatures of polarons and bipolarons.

Molecular doping is a key process to increase the density of charge carriers in organic semiconductors. Doping-induced charges in polymer semiconductors result in the formation of polarons and/or bipolarons due to the strong electron-vibron coupling in conjugated organic materials. Identifying the nature of charge carriers in doped polymers is essential to optimize the doping process for applications. In this work, we use Raman spectroscopy to investigate the formation of charge carriers in molecularly doped poly(3-hexylthiophene-2,5-diyl) (P3HT) for increasing dopant concentration, with the organic salt dimesityl borinium tetrakis(penta-fluorophenyl)borate (Mes2B+ [B(C6F5)4]-) and the Lewis acid tris(pentafluorophenyl)borane [B(C6F5)3]. While the Raman signatures of neutral P3HT and singly charged P3HT segments (polarons) are known, the Raman spectra of doubly charged P3HT segments (bipolarons) are not yet sufficiently understood. Combining Raman spectroscopy measurements on doped P3HT thin films with first-principles calculations on oligomer models, we explain the evolution of the Raman spectra from neutral P3HT to increasingly doped P3HT featuring polarons and eventually bipolarons at high doping levels. We identify and explain the origin of the spectral features related to bipolarons by tracing the Raman signature of the symmetric collective vibrations along the polymer backbone, which - compared to neutral P3HT - redshifts for polarons and blueshifts for bipolarons. This is explained by a planarization of the singly charged P3HT segments with polarons and rather high order in thin films, while the doubly charged segments with bipolarons are located in comparably disordered regions of the P3HT film due to the high dopant concentration. Furthermore, we identify additional Raman peaks associated with vibrations in the quinoid doubly charged segments of the polymer. Our results offer the opportunity for readily identifying the nature of charge carriers in molecularly doped P3HT while taking advantage of the simplicity, versatility, and non-destructive nature of Raman spectroscopy.

Tetraaryldiborane(4) Can Emit Dual Fluorescence Responding to the Structural Change around the B-B Bond.

We report the successful synthesis of tetramesityldiborane(4) (Mes4 B2 ) through the reductive coupling of a dimesitylborinium ion. Owing to the steric protection conferred by the mesityl groups, Mes4 B2 shows exceptional chemical stability and remains intact in water. Single-crystal X-ray analysis revealed that Mes4 B2 has an orthogonal geometry, where the B-B center is completely hidden by the mesityl groups. Remarkably, Mes4 B2 emits dual fluorescence at 460 and 620 nm, both in solution and in the solid state. Theoretical calculations showed that Mes4 B2 in the excited S1 state adopts a twisted or planar geometry, which is responsible for the shorter- or longer-wavelength fluorescence, respectively. The intensity ratio of the dual fluorescence is sensitive to the viscosity of the medium, which suggests that Mes4 B2 has potential as a ratiometric viscosity sensor.

Visualization of Thermal Transport Properties of Self-Assembled Monolayers on Au(111) by Contact and Noncontact Scanning Thermal Microscopy.

Thermal transport properties of patterned binary self-assembled monolayers (SAMs) on Au(111) were examined using scanning thermal microscopy (SThM) with both contact and noncontact methods. We fabricated two-dimensional (2D) patterns with two separate domains of n-hexadecanethiol/benzenethiol, benzenethiol/n-butanethiol, or n-hexadecanethiol/n-butanethiol. In the experimental setup, the efficiency of thermal transport from a SThM tip to the SAM surface can be evaluated in terms of the temperature change at the SThM tip. In the contact regime, where a SThM tip physically contacts the SAM surface, direct thermal transport through the SAM and radiation-based thermal transport through the space where SAMs exist may contribute to a drop in temperature at the tip. In the noncontact regime, thermal transport relies on radiation-based heat dissipation from the heated tip to the SAMs. 2D mapping of the spatial temperature distribution on SAMs reflects the difference in thermal transport properties of the two SAM domains. We found that the contact method is effective for visualizing the temperature contrast, which reflects the thermal transport properties of the constituent molecules when the domains of the SAMs have a similar height, while the noncontact method allows visualization of the temperature distribution, which is related to the height of each domain of the SAMs, rather than the chemical structures of the constituent molecules. Combination of contact and noncontact SThM enables 2D imaging of thermal transport properties and topographic imaging simultaneously and represents a new technique for investigating the thermal properties of materials surfaces, which is essential for nanoscale thermal management.

Features of the complications for intracorporeal Billroth-I and Roux-en-Y reconstruction after laparoscopic distal gastrectomy for gastric cancer.

PURPOSE: Recently, the Roux-en-Y procedure (R-Y) and delta-shaped Billroth-I anastomosis (DB-I) have become prevalent as intracorporeal gastroenteric anastomosis methods after laparoscopic distal gastrectomy (LDG) for gastric cancer. However, the differences in postoperative outcomes between the two methods have not been clarified. Hence, this retrospective study aimed to reveal the features of the complications of the R-Y versus DB-I after LDG. METHODS: The study cohort comprised patients with gastric cancer who underwent DB-I or R-Y after LDG from January 2013 to May 2016. Patient characteristics and surgical and postoperative variables were analyzed. To compensate for intergroup differences in baseline characteristics, estimated propensity scores were used to perform one-on-one matching between the groups. RESULTS: A total of 564 patients were included, and propensity score matching created a matched cohort of 149 pairs in the DB-I and R-Y groups. The incidence of short-term complications such as gastrointestinal fistula classified as Clavien-Dindo grade IIIa or above was significantly greater in the DB-I group than the R-Y group (14.1% versus 4.7%, p=0.004). In contrast, the R-Y was associated with long-term complications such as internal hernia and tended to result in a slightly higher readmission rate in the R-Y group compared with the DB-I group (2.7% versus 6.0%, p=0.128). CONCLUSION: DB-I after LDG was associated with a significantly higher rate of short-term complications compared with the R-Y, whereas characteristic long-term complications tended to be observed after the R-Y. These differences should be considered during the selection of the reconstruction method and postoperative management of LDG.

Observation of Borane-Olefin Proximity Interaction Governing the Structure and Reactivity of Boron-Containing Macrocycles.

While attractive interactions between borane and olefin have been postulated to trigger various boron-mediated organic transformations, proximity structures of these functional groups, other than the formation of weak van der Waals complexes, have never been directly observed. Here we show that a close intramolecular borane-olefin interaction operates in macrocyclic systems containing borane and olefinic groups obtained by multi-step 1,2-carboboration between a strained alkyne and 9-borafluorene derivatives. Depending on Lewis acidity of the borane moiety and the size of the macrocycles, the magnitude of interaction changes, resulting in different reaction modes. The whole picture of the multi-step reactions has been revealed experimentally with theoretical supports. The present finding may not only provide a deeper understanding of the fundamental boron-mediated interaction but also lead to the development of new organic transformations involving molecular activation by boranes.

An Air- and Water-Stable B4 N4 -Heteropentalene Serving as a Host Material for a Phosphorescent OLED.

Replacement of the carbon-carbon bonds of antiaromatic compounds with polar boron-nitrogen bonds often provides isoelectronic BN compounds with excellent thermodynamic stability and interesting photophysical properties. By this element-substitution strategy, we synthesized a new B4 N4 -heteropentalene derivative, 1, which is fully substituted with mesityl groups. Owing to kinetic protection by the sterically bulky substituents, 1 is remarkably stable toward air and even water. Single-crystal X-ray analysis of 1 revealed the bonding characteristics of the B4 N4 -heteropentalene structure. In a glassy matrix, 1 emitted short-wavelength phosphorescence with an onset at 350 nm, indicating that the triplet energy is substantially high. DFT calculations reasonably explained the ground- and excited-state electronic structures of 1 as well as its emission properties. Motivated by the high-energy triplet state of 1, we used it as a host material to fabricate a phosphorescent organic light-emitting diode with an external quantum efficiency of 15 %.

An Element-Substituted Cyclobutadiene Exhibiting High-Energy Blue Phosphorescence.

1,3,2,4-Diazadiboretidine, an isoelectronic heteroanalogue of cyclobutadiene, is an interesting chemical species in terms of comparison with the carbon system, whereas its properties have never been investigated experimentally. According to Baird's rule, Hückel antiaromatic cyclobutadiene acquires aromaticity in the lowest triplet state. Here we report experimental and theoretical studies on the ground- and excited-state antiaromaticity/aromaticity as well as the photophysical properties of an isolable 1,3,2,4-diazadiboretidine derivative. The crystal structure of the diazadiboretidine derivative revealed that the B2 N2 ring adopts a planar rhombic geometry in the ground state. Yet, theoretical calculations showed that the B2 N2 ring turns to a square geometry with a nonaromatic character in the lowest triplet state. Notably, the diazadiboretidine derivative has the lowest singlet and triplet states lying at close energy levels and displays blue phosphorescence.

Chiral crystal-like droplets displaying unidirectional rotational sliding.

The self-assembly of organic molecules into supramolecular materials with structural ordering beyond the nanometre scale is challenging. Here, we report the spontaneous self-assembly of a chiral discotic triphenylene derivative into millimetre-sized droplets. The structure of the droplets is characterized by high positional and orientational ordering and a three-dimensional integrity similar to that of single crystals. Notwithstanding, these assemblies slide when placed on a vertical substrate demonstrating their fluid nature. X-ray imaging shows that during the sliding process the internal crystal-like structure is maintained and that the droplets undergo clockwise or counterclockwise unidirectional rotation, depending on the chirality of their molecular components. Rheological measurements suggest that this rotational behaviour might result from the distinct yield stress between the (R)- and (S)-enantiomers. Overall, our findings demonstrate that molecular chirality can determine the movement direction of a supramolecular structure, thus expanding the fundamental understanding of the structure and dynamics of soft materials.

Steam induced by the activation of energy devices under a wet condition may cause thermal injury.

BACKGROUND: During esophagectomy for esophageal cancer, meticulous attention is needed to prevent thermal injury to the vital organs, such as the recurrent laryngeal nerve (RLN) and tracheobronchus. In order to clarify the novel mechanism behind thermal injury induced by energy devices, we investigated the temperature of steam with the use of two different devices under wet and dry conditions. METHODS: An ultrasonic device (Sonicision™) and a vessel sealing device (Ligasure™) were studied. We evaluated the temperature at the tip of the devices and the steam when the devices were activated under different grasping ranges, under four different combinations of device and muscle, and under four different wet/dry conditions (dry-dry, dry-wet, wet-dry, and wet-wet). RESULTS: Although the maximum temperature of the devices was significantly higher with Sonicision™ than with Ligasure™, the maximum temperature of the steam was significantly higher with Ligasure™ than with Sonicision™ in almost all situations. At 1 mm away from Sonicision™, the critical temperature more than 60 °C was observed only when used with one-third grasping range under the wet-dry or the wet-wet conditions. In case of Ligasure™, high-temperature steam was observed when used with one-third grasping under the wet-dry or the wet-wet condition and two-third grasping under the dry-wet, the wet-dry, or the wet-wet condition. Under the wet condition, the emission of steam from the non-grasping part of Ligasure™ caused a spike in temperature that exceeded the critical temperature. CONCLUSION: We demonstrated that the use of energy devices under a wet condition generates steam from the non-grasping part of the devices. The temperatures of steam from Ligasure™ were significantly higher than that from Sonicision™. To prevent thermal injury to the vital organs, a very attentive and meticulous surgical technique is imperative considering the characteristics of each device.

Electric-Field-Controllable Conductance Switching of an Overcrowded Ethylene Self-Assembled Monolayer.

Molecular isomerism has been discussed from the viewpoint of the tiniest switch and memory elements in electronics. Here, we report an overcrowded ethylene-based molecular conductance switch, which fulfills all the essential requirements for implementation into electronic devices, namely, electric-field-controllable reversible conductance change with a molecular-level spatial resolution, robust conformational bistability under ambient conditions, and ordered monolayer formation on electrode surfaces. The conformational state of this overcrowded ethylene, represented by a folded or twisted conformer, is susceptible to external environments. Nanoscopic measurements using scanning tunneling microscopy techniques, together with theoretical simulations, revealed the electronic properties of each conformer adsorbed on Au(111). While the twisted conformer prevails in the molecularly dispersed state, upon self-assembly into a monolayer, a two-dimensional network structure of the folded conformer is preferentially formed due to particular intermolecular interaction. In the monolayer state, folded-to-twisted and its reverse isomerization can be controlled by the modulation of electric fields.

Triptycene Tripods for the Formation of Highly Uniform and Densely Packed Self-Assembled Monolayers with Controlled Molecular Orientation.

When employing self-assembled monolayers (SAMs) for tuning surface and interface properties, organic molecules that enable strong binding to the substrate, large-area structural uniformity, precise alignment of functional groups, and control of their density are highly desirable. To achieve these goals, tripod systems bearing multiple bonding sites have been developed as an alternative to conventional monodentate systems. Bonding of all three sites has, however, hardly been achieved, with the consequence that structural uniformity and orientational order in tripodal SAMs are usually quite poor. To overcome that problem, we designed 1,8,13-trimercaptomethyltriptycene (T1) and 1,8,13-trimercaptotriptycene (T2) as potential tripodal SAM precursors and investigated their adsorption behavior on Au(111) combining several advanced experimental techniques and state-of-the-art theoretical simulations. Both SAMs adopt dense, nested hexagonal structures but differ in their adsorption configurations and structural uniformity. While the T2-based SAM exhibits a low degree of order and noticeable deviation from the desired tripodal anchoring, all three anchoring groups of T1 are equally bonded to the surface as thiolates, resulting in an almost upright orientation of the benzene rings and large-area structural uniformity. These superior properties are attributed to the effect of conformationally flexible methylene linkers at the anchoring groups, absent in the case of T2. Both SAMs display interesting electronic properties, and, bearing in mind that the triptycene framework can be functionalized by tail groups in various positions and with high degree of alignment, especially T1 appears as an ideal docking platform for complex and highly functional molecular films.