[A case of small intestinal endometriosis with bowel obstruction and perforation].

A 47-year-old woman was referred to our hospital with recurring lower abdominal pain persisting for more than 2 weeks. Imaging modalities showed small bowel obstruction caused by a mass lesion in the terminal ileum. Despite undergoing fasting, rehydration, and decompression through an ileus tube, her symptoms persisted. Furthermore, the condition deteriorated on day 4, with the onset of her menstrual period. An emergency surgery was conducted on the 7th day after hospitalization. Surgical observations indicated severe stenosis around the ileocecal valve and ileal perforation approximately 40cm from the oral stricture. As a result, ileocecal resection was performed. Pathological examination revealed endometrial tissue infiltration through the mucosal lamina propria to the ileal subserosa. Thus, the patient was identified with intestinal endometriosis of the ileocecum. Endometriosis of the small bowel is an uncommon condition that eventually causes intractable bowel obstruction. Although preoperative diagnosis is considered challenging, intestinal endometriosis should be included in the differential diagnosis in cases of bowel obstruction in women of childbearing age.

Factors, Including Clinical Trial Eligibility, Associated with Induction of Third-Line Treatment for Advanced Gastric Cancer.

INTRODUCTION: Third-line chemotherapy has been suggested to improve survival in patients with gastric cancer. This study aimed to identify factors associated with the induction of third-line chemotherapy for advanced gastric cancer, focusing on patient eligibility for clinical trial. METHODS: We retrospectively analyzed 335 patients treated for unresectable or recurrent gastric cancer between April 2009 and May 2020. The patients were grouped into those that met the key eligibility criteria for clinical trial (136 patients, 40.6%) and those that did not (199 patients, 59.4%) before receiving first-line chemotherapy. RESULTS: The overall survival (OS) was 16.8 months (95% CI: 14.0-19.6) and 9.3 months (95% CI: 7.8-11.0) in the eligible and ineligible group, respectively. Multivariate analyses to identify the risk factors associated with the induction of third-line chemotherapy revealed ineligibility of clinical trial (OR 1.95; 95% CI: 1.15-3.31), number of metastatic sites (OR 1.99; 95% CI: 1.23-3.22), low albumin concentration (OR 2.24; 95% CI: 1.14-4.38), and a lack of complete or partial response to first-line treatment (OR 1.85; 95% CI: 1.05-3.26). Indeed, in responders to first-line treatment for ineligible patients, the median OS was 17.7 months (95% CI: 10.6-27.9), respectively. CONCLUSIONS: Treatment outcomes were different for those eligible for clinical trials and those who were not. However, this study suggested that patients who responded to first-line treatment have more favorable prognosis when treated with salvage chemotherapy, even if they were deemed ineligible for clinical trials.

Partially Oxidized Purely Organic Zwitterionic Neutral Radical Conductor: Multi-step Phase Transitions and Crossover Caused by Intra- and Intermolecular Electronic Interactions.

Formation of a partially charge-transfer or partially oxidized/reduced state has been one of the most important requirements for the development of highly conducting molecular materials, such as organic metals and superconductors. This requirement has been fulfilled by combining appropriate electron-donor and acceptor molecules to construct multi-component molecular complexes/salts, such as (TTF+0.59)(TCNQ-0.59) and (BEDT-TTF+0.5)2X-, where TTF = tetrathiafulvalene, TCNQ = tetracyanoquinodimethane, BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene, and X = monovalent inorganic anion. Here, we propose a methodology to fulfill this requirement by a single neutral molecule; namely, we have connected two TTF+0.5-type partially oxidized π-skeletons through a boron anion to design a purely organic zwitterionic neutral radical {[(PDT-TTF-Cat)2]+B-}•. This molecule was successfully obtained as air-stable crystals containing solvent tetrahydrofuran (THF) molecules. Measurements of electrical resistivity, magnetic susceptibility, and X-ray diffraction reveal that the partially oxidized state is certainly formed, which enables realization of a 3/4-filled electron band. Furthermore, this system has intramolecular charge degrees of freedom, attributable to the two TTF+0.5 π-skeletons introduced into the molecule. The resulting interplay of intra- and intermolecular charge degrees of freedom (or simply, intra- and intermolecular electronic interactions) has led to multi-step phase transitions and crossover, providing unique strongly correlated electron properties, such as the formation of a three-dimensional charge-ordered dimer-Mott insulating state and its melting triggered by disorder-order transformation of the co-crystallized solvent THF molecules at low temperatures.

Double-σ-Bonded Close-Shell Dimers and Peroxy-Linked Open-Shell Dimer Derived from a C3 Symmetric Trioxophenalenyl Neutral Diradical.

A novel neutral diradical of π-extended phenalenyl derivative having three oxo-groups, tri-tert-butyl-1,4,7-trioxophenalenyl, and two types of the corresponding σ-dimers were investigated. Quantum chemical calculations showed that the neutral diradical is in triplet ground state having doubly degenerate singly occupied molecular orbitals. The neutral diradical undergoes a σ-dimerization, generating two types of σ-dimers immediately after the preparation. One of the σ-dimers, which was selectively generated in the crystalline state, was a close-shell dimer linked through double-σ-bonds on the phenalenyl skeleton with a long C-C bond length of 1.66 Å. The other σ-dimer, which existed only in the solution state, was a peroxy-linked open-shell dimer in which one σ-bond was formed between two oxygen atoms. Furthermore, the temperature-dependent 1 H NMR and ESR spectra revealed that these σ-dimers are in equilibrium in the solution state by the reversible σ-bond formation/cleavage via the neutral diradical as a key intermediate.

Reversible Insulator-Metal Transition by Chemical Doping and Dedoping of a Mott Insulator.

The chemical carrier doping of molecular Mott insulators has been poorly investigated to date due to its difficulty. In this study, iodine doping of a molecular Mott insulator, lithium phthalocyanine crystallized in the x-form (x-LiPc), was performed to obtain metallic x-LiPcI. Crystal structure analysis revealed that iodine atoms penetrated channels of x-LiPc and formed one-dimensional chains. The Raman spectroscopy of x-LiPcI indicated the existence of linear I5 - , demonstrating a transition from a half-filled band of the Mott insulating state to a 2/5-filled band of the metallic state. Electrical resistivity measurements confirmed the metallic nature of x-LiPcI, whereas a thermally activated behavior was observed for pristine x-LiPc. Furthermore, the x-LiPc Mott insulator was reproduced by dedoping iodine from x-LiPcI, suggesting that the electronic state can be reversibly tuned between the Mott insulating and metallic states by chemical doping and dedoping.

Synthesis and Physical Properties of Trioxotriangulene Having Methoxy and Hydroxy Groups at α-Positions: Electronic and Steric Effects of Substituent Groups and Intramolecular Hydrogen Bonds.

New 4,8,12-trioxotriangulene (TOT) neutral radical derivatives having three methoxy and hydroxy groups at the α-positions were synthesized, and the substituent effects on the electronic spin and redox properties were elucidated in the theoretical and experimental methods. Due to the small SOMO coefficients at the α-positions of TOT, the methoxy groups in the TOT neutral radical had negligible effects on the electronic spin structure and redox ability. On the other hand, methoxy groups greatly increased the LUMO energy having large coefficients at α-positions and, thus, caused a remarkable negative-potential shift of the redox wave of anion species involving the dianion and trianion species. Converting the methoxy groups to hydroxy groups caused a dramatic change in the electronic structure of TOT, where the intramolecular hydrogen bonds between hydroxy groups and oxo groups strongly attracted a minus charge on the TOT skeleton. The HOMO energy of the monoanion species was significantly reduced, causing a blue shift of the HOMO-LUMO transition and an anodic shift of the redox potential. In addition, due to the steric repulsion smaller than that of the methoxy group, the hydroxy derivative showed a more planar molecular structure and a strong π-stacking ability.

Small intestinal mucosal injury and its risk factors in patients with gastrointestinal cancer who developed complicated fluoropyrimidine-induced diarrhea.

BACKGROUND: Diarrhea is a common adverse event of fluoropyrimidine-based chemotherapy. However, limited data are available on the frequency and risk factors of complicated chemotherapy-induced diarrhea (CID) and small intestinal mucosal damage. In this current study, we aimed to determine the incidence of complicated CID and mucosal injury among patients with complicated CID receiving fluoropyrimidine via small bowel capsule endoscopy (CE) and determined baseline risk factors associated with complicated CID. METHODS: In total, 536 patients with advanced or recurrent gastrointestinal cancer who received fluoropyrimidine-based chemotherapy were retrospectively analyzed. Diarrhea was evaluated using the Common Terminology Criteria for Adverse Events version 4. Complicated CID was defined according to the American Society of Clinical Oncology guidelines. To evaluate small intestinal mucosal injury in patients with complicated CID, CE was performed. Multivariate analysis was performed to identify risk factors for complicated CID. RESULTS: Total number of 32 (6%) patients developed complicated CID. Complicating symptoms were noted in 25 (78%) patients, with cramping, vomiting, and sepsis being observed in 15 (60%), 8 (32%), and 3 (12%) patients, respectively. Among the 13 patients who underwent CE, 11 (85%) showed abnormal findings. Multivariate analysis revealed that oral fluoropyrimidine administration was a risk factor for complicated CID (odds ratio 2.95; 95% confidence interval 1.06-8.19). CONCLUSIONS: Despite the relatively low incidence of complicated CID, mucosal injury of small intestine was common in patients with complicated fluoropyrimidine-induced diarrhea and oral fluoropyrimidine was an independent risk factor.

[A case of Lemmel syndrome caused by food residue in giant juxtapapillary diverticulum].

A woman in her 70s was admitted to our hospital because of epigastric pain and anorexia. Laboratory evaluations revealed elevated levels of liver transaminases, biliary enzymes, and amylase. CT and MRCP showed dilatation of the bile and pancreatic ducts and a large juxtapapillary diverticulum filled with contents. There were no gallstones or tumors present. Our differential diagnosis included obstruction of the papilla of Vater, so we performed an urgent ERCP. Endoscopic examination showed the juxtapapillary diverticulum filled with food residue;however, we were unable to locate the papilla of Vater. We rinsed out and removed food residue from the diverticulum using a retrieval balloon catheter used for gallstones. After the endoscopic removal of the food residue, the patient's epigastric pain immediately subsided and her cholangitis and pancreatitis improved gradually.

Strong Hydrogen Bonds at the Interface between Proton-Donating and -Accepting Self-Assembled Monolayers on Au(111).

Hydrogen-bonding heterogeneous bilayers on substrates have been studied as a base for new functions of molecular adlayers by means of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRAS), and density functional theory (DFT) calculations. Here, we report the formation of the catechol-fused bis(methylthio)tetrathiafulvalene (H2Cat-BMT-TTF) adlayer hydrogen bonding with an imidazole-terminated alkanethiolate self-assembled monolayer (Im-SAM) on Au(111). The heterogeneous bilayer is realized by sequential two-step immersions in solutions for the individual Im-SAM and H2Cat-BMT-TTF adlayer formations. In the measurements by AFM, a grained H2Cat-BMT-TTF adlayer on Im-SAM is revealed. The coverage and the chemical states of H2Cat-BMT-TTF on Im-SAM are specified by XPS. On the vibrational spectrum measured by IRAS, the strong hydrogen bonds between H2Cat-BMT-TTF and Im-SAM are characterized by the remarkably red-shifted OH stretching mode at 3140 cm-1, which is much lower than that for hydrogen-bonding water (typically ∼3300 cm-1). The OH stretching mode frequency and the adsorption strength for the H2Cat-BMT-TTF molecule hydrogen bonding with imidazole groups are quantitatively examined on the basis of DFT calculations.

Thermal transport in electrospun vinyl polymer nanofibers: effects of molecular weight and side groups.

Understanding and enhancing thermal transport in polymers is of great importance, and is necessary to enable next-generation flexible electronics, heat exchangers, and energy storage devices. Over the past several decades, significant enhancement of the thermal conductivity of polymeric materials has been achieved, but several key questions related to the effects of molecular structure on thermal transport still remain. By studying a series of electrospun vinyl polymer nanofibers, we investigate the relationship between thermal conductivity and both molecular chain length and side group composition. For polyethylene nanofibers with different molecular weights, the measured thermal conductivity increases monotonically with molecular chain length, as energy transport along molecular chains is more efficient than between chains. The observed trend is also consistent with structural characterization by Raman spectroscopy, which shows enhanced crystallinity as molecular weight increases. Further, by comparing the measured thermal conductivity of vinyl polymer nanofibers with different side groups, we found that phonons travel along polymer chains more effectively when the side groups are either lighter or more symmetric. These experimental results help reveal the underlying correlation between the molecular structure and thermal conductivity of polymer nanofibers, providing valuable insights into the design of polymeric materials with enhanced thermal conductivity.

Theoretical study of the H/D isotope effect on phase transition of hydrogen-bonded organic conductor κ-H3(Cat-EDT-TTF)2.

κ-H3(Cat-EDT-TTF)2 (H-TTF) is a hydrogen-bonded π-electron system which was found to reveal C2/c symmetry at 50-293 K, while its isotopologue, κ-D3(Cat-EDT-TTF)2 (D-TTF), showed the phase transition at 185 K from C2/c to P1[combining macron]. To elucidate the origin of such a difference, we calculated the potential energy curves (PECs) for the hydrogen transfer along the H-bonds in these conductors. We found that both the π-stacking and the hydrogen nuclear quantum effect drastically affected the hydrogen transfer energy. By taking account of both effects, we obtained a symmetric single-well effective PEC for H-TTF, which indicated that the hydrogen was always located at the center of the H-bond. By contrast, the effective PEC of D-TTF was a low-barrier double-well, indicating that the position of the H-bonded deuterium would change according to the temperature. We concluded that the π-stacking and the nuclear quantum effect were the key factors for the appearance of phase transition only in D-TTF.

Hydrogeochemistry and quality of surface water and groundwater in the vicinity of Lake Monoun, West Cameroon: approach from multivariate statistical analysis and stable isotopic characterization.

With the use of conventional hydrogeochemical techniques, multivariate statistical analysis, and stable isotope approaches, this paper investigates for the first time surface water and groundwater from the surrounding areas of Lake Monoun (LM), West Cameroon. The results reveal that waters are generally slightly acidic to neutral. The relative abundance of major dissolved species are Ca(2+) > Mg(2+) > Na(+) > K(+) for cations and HCO3 (-) â‰« NO3 (-) > Cl(-) > SO4 (2-) for anions. The main water type is Ca-Mg-HCO3. Observed salinity is related to water-rock interaction, ion exchange process, and anthropogenic activities. Nitrate and chloride have been identified as the most common pollutants. These pollutants are attributed to the chlorination of wells and leaching from pit latrines and refuse dumps. The stable isotopic compositions in the investigated water sources suggest evidence of evaporation before recharge. Four major groups of waters were identified by salinity and NO3 concentrations using the Q-mode hierarchical cluster analysis (HCA). Consistent with the isotopic results, group 1 represents fresh unpolluted water occurring near the recharge zone in the general flow regime; groups 2 and 3 are mixed water whose composition is controlled by both weathering of rock-forming minerals and anthropogenic activities; group 4 represents water under high vulnerability of anthropogenic pollution. Moreover, the isotopic results and the HCA showed that the CO2-rich bottom water of LM belongs to an isolated hydrological system within the Foumbot plain. Except for some springs, groundwater water in the area is inappropriate for drinking and domestic purposes but good to excellent for irrigation.

Modulation of a Molecular π-Electron System in a Purely Organic Conductor that Shows Hydrogen-Bond-Dynamics-Based Switching of Conductivity and Magnetism.

New important aspects of the hydrogen-bond (H-bond)-dynamics-based switching of electrical conductivity and magnetism in an H-bonded, purely organic conductor crystal have been discovered by modulating its tetrathiafulvalene (TTF)-based molecular π-electron system by means of partial sulfur/selenium substitution. The prepared selenium analogue also showed a similar type of phase transition, induced by H-bonded deuterium transfer followed by electron transfer between the H-bonded TTF skeletons, and the resulting switching of the physical properties; however, subtle but critical differences due to sulfur/selenium substitution were detected in the electronic structure, phase transition nature, and switching function. A molecular-level discussion based on the crystal structures shows that this chemical modification of the TTF skeleton influences not only its own π-electronic structure and π-π interactions within the conducting layer, but also the H-bond dynamics between the TTF π skeletons in the neighboring layers, which enables modulation of the interplay between the H-bond and π electrons to cause such differences.

Characteristics of MPO-ANCA-positive granulomatosis with polyangiitis: a retrospective multi-center study in Japan.

We studied the clinico-pathological differences among PR3-ANCA-positive granulomatosis with polyangiitis (PR3-GPA), MPO-ANCA-positive GPA (MPO-GPA) and microscopic polyangiitis (MPA). ANCA-associated vasculitis (AAV) was classified using the European Medicines Agency classification. We retrospectively analyzed 38 patients with GPA and 41 with MPA treated in eight hospitals in Japan. Of the patients with GPA, 17 were positive for MPO-ANCA, and 15 for PR3-ANCA. All patients with MPA were MPO-ANCA positive. The mean ages of those with MPO-GPA were 69.6 years old, 10 years older than those with PR3-GPA. The majority (82 %) of patients with MPO-GPA were woman, a significantly greater proportion than for PR3-GPA. We also found that ear, nose and throat (ENT), nervous system involvement were significantly more common in MPO-GPA, but renal function was less impaired than those with MPA. Both PR3-GPA and MPO-GPA relapsed more frequently than MPA, but overall survival was significantly better (P < 0.01 and P < 0.05, respectively). Univariate analysis identified the following factors as predictors of a poor prognosis: MPA (P < 0.01), pulmonary UIP pattern (P < 0.005) Cr ≥ 1.7 mg/dl (P < 0.01) and absence of ENT involvement (P < 0.05), which were characteristics of MPA. In our cohort, MPO-GPA was most likely to affect older women and was associated with otitis media, nervous system involvement, mild renal impairment and more favorable outcome. It is clinically useful to differentiate MPO-GPA from MPA and PR3-GPA in patients with AAV.

[Streptococcal Toxic Shock-like Syndrome due to Streptococcus suis Serotype 2 in a Japanese Pig Farmer].

Streptococcus suis is a major swine pathogen. It has recently been recognized as an emerging zoonosis that causes mainly meningitis and sepsis in human. In particular, toxic shock-like syndrome (TSLS) caused by this pathogen has a high mortality rate. However, misidentification of S. suis by conventional biochemical and commercial identification tests is not rare. The patient was a 71-year-old man who worked as a pig farmer who was admitted for fever, oliguria and subcutaneous hemorrhage. He was diagnosed as having septic shock and blood culture was positive for Gram-positive cocci, mainly diplococcus. This pathogen was identified with S. suis with using MALDI-TOF MS analysis, though a commercial Gram-Positive bacteria identification kit revealed viridans streptococci. His clinical features met the diagnostic criteria of TSLS, and ceftriaxone and clindamycin were administered. On admission day 28, he was discharged in good condition.

Flow and geochemical modeling of drainage from Tomitaka mine, Miyazaki, Japan.

The chemistry and flow of water in the abandoned Tomitaka mine of Miyazaki, western Japan were investigated. This mine is located in a non-ferrous metal deposit and acid mine drainage issues from it. The study was undertaken to estimate the quantities of mine drainage that needs to be treated in order to avoid acidification of local rivers, taking into account seasonal variations in rainfall. Numerical models aimed to reproduce observed water levels and fluxes and chemical variations of groundwater and mine drainage. Rock-water interactions that may explain the observed variations in water chemistry are proposed. The results show that: (1) rain water infiltrates into the deeper bedrock through a highly permeable zone formed largely by stopes that are partially filled with spoil from excavations (ore minerals and host rocks); (2) the water becomes acidic (pH from 3 to 4) as dissolved oxygen oxidizes pyrite; (3) along the flow path through the rocks, the redox potential of the water becomes reducing, such that pyrite becomes stable and pH of the mine drainage becomes neutral; and (4) upon leaving the mine, the drainage becomes acidic again due to oxidation of pyrite in the rocks. The present numerical model with considering of the geochemical characteristics can simulate the main variations in groundwater flow and water levels in and around the Tomitaka mine, and apply to the future treatment of the mine drainage.

Synthesis of racemic and chiral BEDT-TTF derivatives possessing hydroxy groups and their achiral and chiral charge transfer complexes.

Chiral molecular crystals built up by chiral molecules without inversion centers have attracted much interest owing to their versatile functionalities related to optical, magnetic, and electrical properties. However, there is a difficulty in chiral crystal growth due to the lack of symmetry. Therefore, we made the molecular design to introduce intermolecular hydrogen bonds in chiral crystals. Racemic and enantiopure bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) derivatives possessing hydroxymethyl groups as the source of hydrogen bonds were designed. The novel racemic trans-vic-(hydroxymethyl)(methyl)-BEDT-TTF 1, and racemic and enantiopure trans-vic-bis(hydroxymethyl)-BEDT-TTF 2 were synthesized. Moreover, the preparations, crystal structure analyses, and electrical resistivity measurements of the novel achiral charge transfer salt θ(21)-[(S,S)-2]3[(R,R)-2]3(ClO4)2 and the chiral salt α'-[(R,R)-2]ClO4(H2O) were carried out. In the former θ(21)-[(S,S)-2]3[(R,R)-2]3(ClO4)2, there are two sets of three crystallographically independent donor molecules [(S,S)-2]2[(R,R)-2] in a unit cell, where the two sets are related by an inversion center. The latter α'-[(R,R)-2]ClO4(H2O) is the chiral salt with included solvent H2O, which is not isostructural with the reported chiral salt α'-[(S,S)-2]ClO4 without H2O, but has a similar donor arrangement. According to the molecular design by introduction of hydroxy groups and a ClO4 (-) anion, many intermediate-strength intermolecular hydrogen bonds (2.6-3.0 Å) were observed in these crystals between electron donor molecules, anions, and included H2O solvent, which improve the crystallinity and facilitate the extraction of physical properties. Both salts are semiconductors with relatively low resistivities at room temperature and activation energies of 1.2 ohm cm with E a = 86 meV for θ(21)-[(S,S)-2]3[(R,R)-2]3(ClO4)2 and 0.6 ohm cm with E a = 140 meV for α'-[(R,R)-2]2ClO4(H2O), respectively. The variety of donor arrangements, θ(21) and two kinds of α'-types, and their electrical conductivities of charge transfer complexes based upon the racemic and enantiopure (S,S)-2, and (R,R)-2 donors originates not only from the chirality, but also the introduced intermolecular hydrogen bonds involving the hydroxymethyl groups, perchlorate anion, and the included solvent H2O.

Hydrogen-bond-dynamics-based switching of conductivity and magnetism: a phase transition caused by deuterium and electron transfer in a hydrogen-bonded purely organic conductor crystal.

A hydrogen bond (H-bond) is one of the most fundamental and important noncovalent interactions in chemistry, biology, physics, and all other molecular sciences. Especially, the dynamics of a proton or a hydrogen atom in the H-bond has attracted increasing attention, because it plays a crucial role in (bio)chemical reactions and some physical properties, such as dielectricity and proton conductivity. Here we report unprecedented H-bond-dynamics-based switching of electrical conductivity and magnetism in a H-bonded purely organic conductor crystal, κ-D3(Cat-EDT-TTF)2 (abbreviated as κ-D). This novel crystal κ-D, a deuterated analogue of κ-H3(Cat-EDT-TTF)2 (abbreviated as κ-H), is composed only of a H-bonded molecular unit, in which two crystallographically equivalent catechol-fused ethylenedithiotetrathiafulvalene (Cat-EDT-TTF) skeletons with a +0.5 charge are linked by a symmetric anionic [O···D···O](-1)-type strong H-bond. Although the deuterated and parent hydrogen systems, κ-D and κ-H, are isostructural paramagnetic semiconductors with a dimer-Mott-type electronic structure at room temperature (space group: C2/c), only κ-D undergoes a phase transition at 185 K, to change to a nonmagnetic insulator with a charge-ordered electronic structure (space group: P1). The X-ray crystal structure analysis demonstrates that this dramatic switching of the electronic structure and physical properties originates from deuterium transfer or displacement within the H-bond accompanied by electron transfer between the Cat-EDT-TTF π-systems, proving that the H-bonded deuterium dynamics and the conducting TTF π-electron are cooperatively coupled. Furthermore, the reason why this unique phase transition occurs only in κ-D is qualitatively discussed in terms of the H/D isotope effect on the H-bond geometry and potential energy curve.

Gapless quantum spin liquid in an organic spin-1/2 triangular-lattice κ-H3(Cat-EDT-TTF)2.

We report the results of SQUID and torque magnetometry of an organic spin-1/2 triangular-lattice κ-H(3)(Cat-EDT-TTF)(2). Despite antiferromagnetic exchange coupling at 80-100 K, we observed no sign of antiferromagnetic order down to 50 mK owing to spin frustration on the triangular lattice. In addition, we found nearly temperature-independent susceptibility below 3 K associated with Pauli paramagnetism. These observations suggest the development of gapless quantum spin liquid as the ground state. On the basis of a comparative discussion, we point out that the gapless quantum spin liquid states in organic systems share a possible mechanism, namely the formation of a band with a Fermi surface possibly attributed to spinons.

Protonation of pyridyl-substituted TTF derivatives: substituent effects in solution and in the proton-electron correlated charge-transfer complexes.

Protonated pyridyl-substituted tetrathiafulvalene electron-donor molecules (PyH(+)-TTF) showed significant changes in the electron-donating ability and HOMO-LUMO energy gap compared to the neutral analogues and gave a unique N(+)-H⋅⋅⋅N hydrogen-bonded (H-bonded) dimer unit in the proton-electron correlated charge-transfer (CT) complex crystals. We have evaluated these features from the viewpoint of the molecular structure of the PyH(+)-TTF derivatives, that is, the substitution position of the Py group and/or the presence or absence of the ethylenedithio (EDT) group. Among 2-PyH(+)-TTF (1 oH(+)), 3-PyH(+)-TTF (1 mH(+)), 4-PyH(+)-TTF (1 pH(+)), and 4-PyH(+)-EDT-TTF (2 pH(+)) systems, the para-pyridyl-substituted donors 1 pH(+) and 2 pH(+) exhibit more marked changes upon protonation in solution; a larger redshift in the intramolecular CT absorption band and a larger decrease in the electron-donating ability. Furthermore, the EDT system 2 pH(+) has the smallest intramolecular Coulombic repulsion energy. These differences are reasonably interpreted by considering the energy levels and distributions of the HOMO and LUMO obtained by quantum chemical calculations. Such substituent effects related to protonation were also examined by comparing the structure and properties of a new H-bonded CT complex crystal based on 2 pH(+) with those of its 1 pH(+) analogue recently prepared by us: Both of them form a similar type of H-bonded dimer unit, however, its charge distribution as well as the overall molecular arrangement, electronic structure, and conductivity were significantly modulated by the introduction of the EDT group. These results provide a new insight into the structural and electronic features of the PyH(+)-TTF-based proton-electron correlated molecular conductors.