peri-Benzo-Diindenotetracenyl: Helically π-Extended Allyl Radical with Robust Stability.

Here is described the synthesis and characterization of a stable hydrocarbon radical, peri-benzo-diindenotetracenyl, with a helical structure. Although the helical π-radical has no peripheral substituents, it was stable in the solid and solutions. According to the X-ray diffraction analysis and quantum chemical calculations, the radical was best described as an allyl radical fused by five Clar's sextets. The optically resolved enantiomers exhibited mirror image CD spectra with |gCD| of 2.4×10-4 at 522 nm. The racemization barrier was determined to be 95.9 kJ/mol at 298 K, which is compatible with that of [5]helicene (108 kJ/mol).

[22]Pentaphyrins(2.0.1.1.0) Displaying N-Fusion, Pyrrole-Rearrangement, and Dimerization Reactions Upon Oxidation and Metalation.

Exploration of expanded porphyrins with unprecedented reactivities has remained important. Here [22]pentaphyrins(2.0.1.1.0) were synthesized as a constitutional isomer of sapphyrin by acid-catalyzed cyclization of 1,14-dibromo-5,10-diaryltripyrrin with 1,2-di(pyrro-2-ly)ethenes. These pentaphyrins display roughly planar structures and varying aromaticities depending upon the vinylene structures. The 19,20-ditolyl pentaphyrin gave an N-fused product and an unprecedented pyrrole-rearranged product, depending upon the oxidation conditions. Remarkably, upon the metalation with CuCl, the N-fused product and the pyrrole-rearranged product afforded an inner b-b coupled face-to-face CuII complex dimer and an outer b-b coupled lateral CuII complex dimer, respectively, in fairly good yields. Further, [22]pentaphyrin(2.0.1.1.0) fused with a NiII porphyrin was effectively dimerized upon oxidation with MnO2 to give a 16-16' directly linked dl-dimer.

Optically Distinguishable Electronic Spin-isomers of a Stable Organic Diradical.

Herein, we introduce a model of electronic spin isomers, the electronic counterpart of nuclear spin isomers, by using a stable organic diradical. The diradical, composed of two benzotriazinyl radicals connected by a rigid triptycene skeleton, exhibits a small singlet-triplet energy gap of -3.0 kJ/mol, indicating ca. 1:1 coexistence of the two spin states at room temperature. The diradical shows characteristic near-IR absorption bands, which are absent in the corresponding monoradical subunit. Variable temperature measurements revealed that the absorbance of the NIR band depends on the abundance of the singlet state, allowing us to identify the NIR band as the singlet-specific absorption band. It enables photoexcitation of one of the two spin states coexisting in thermal equilibrium. Transient absorption spectroscopy disclosed that the two spin states independently follow qualitatively different excited-state dynamics. These results demonstrate a novel approach to the design and study of electronic spin isomers based on organic diradicals.

POLD1 Is Required for Cell Cycle Progression by Overcoming DNA Damage in Malignant Pleural Mesothelioma.

BACKGROUND/AIM: The prognosis of patients with malignant pleural mesothelioma (MPM) remains poor due to lack of effective therapeutic targets. DNA damage caused by long-time exposure to asbestos fibers has been associated with the development of MPM, with mutations at genes encoding DNA damage repair (DDR)-related molecules frequently expressed in patients with MPM. The present study was designed to identify novel therapeutic targets in MPM using large public databases, such as The Cancer Genome Atlas (TCGA) and Genotype Tissue Expression project (GTEx) focused on DDR pathways. MATERIALS AND METHODS: The correlations between mRNA expression levels of DDR-related genes and overall survival (OS) were analyzed in mesothelioma patients in TCGA mesothelioma (TCGA-MESO) datasets. The anti-tumor effects of small interfering RNAs (siRNA) against DDR-related genes associated with OS were subsequently tested in MPM cell lines. RESULTS: High levels of mRNA encoding DNA polymerase delta 1, catalytic subunit (POLD1) were significantly associated with reduced OS in patients with MPM (p<0.001, Log-rank test). In addition, siRNA targeting POLD1 (siPOLD1) caused cell cycle arrest at the G1/S checkpoint and induced apoptosis involving accumulation of DNA damage in MPM cell lines. CONCLUSION: POLD1 plays essential roles in overcoming DNA damage and cell cycle progression at the G1/S checkpoint in MPM cells. These findings suggest that POLD1 may be a novel therapeutic target in MPM.

A Triply Linked Porphyrin-Norcorrole Hybrid with Singlet Diradical Character.

Norcorrole Ni(II) complexes have recently received considerable attention because they are readily accessible antiaromatic molecules. Their high stability under ambient conditions and ease of synthesis have enabled the exploration of the intrinsic properties of antiaromatic molecules. Here, we report the synthesis and properties of meso-meso singly linked porphyrin-norcorrole hybrids and a triply linked porphyrin-norcorrole hybrid. The singly linked and triply linked porphyrin-norcorrole hybrids were fully characterized, including an X-ray structural analysis. Due to their orthogonal conformation, the singly linked hybrids maintain the individual electronic properties of their porphyrin and norcorrole subunits, while the triply linked hybrid shows a significantly smaller electrochemical HOMO-LUMO gap (0.45 eV) than that of Ni(II) dimesitylnorcorrole (1.08 eV). Furthermore, the triply linked hybrid exhibits singlet diradical characteristics, as confirmed by VT NMR, ESR, and SQUID experiments.

Immunologic Significance of CD80/CD86 or Major Histocompatibility Complex-II Expression in Thymic Epithelial Tumors.

Introduction: Unresectable or recurrent thymic epithelial tumors (TETs) have a poor prognosis, and treatment options are limited. This study aimed to investigate the immunologic significance of CD80/CD86 or major histocompatibility complex class II (MHC-II) expression in TETs, as potential predictive biomarkers for immune checkpoint inhibitors (ICIs). Methods: We analyzed CD80, CD86, MHC class I (MHC-I), and MHC-II expression in TETs using immunohistochemistry and investigated their association with T-cell infiltration or ICI efficacy. In addition, we generated CD80- or MHC-II-expressing mouse tumors, evaluated the effects of ICIs, and analyzed tumor-infiltrating lymphocytes. We also performed tumor-rechallenge experiments in vivo. Results: We found that approximately 50% and 30% of TETs had high expression of CD80/CD86 and MHC-II in tumor cells, respectively, and that this expression was related to T-cell infiltration in clinical samples. In mouse models, both CD80 and MHC-II increase the effects of ICIs. In addition, senescent T cells and long-lived memory precursor effector T cells were significantly decreased and increased, respectively, in tumor-infiltrating lymphocytes from CD80-expressing tumors, and rechallenged tumors were completely rejected after the initial eradication of CD80-expressing tumors by programmed cell death protein 1 blockade. Indeed, patients with CD80-high thymic carcinoma had longer progression-free survival with anti-programmed cell death protein 1 monoclonal antibody. Conclusions: Half of the TETs had high expression of CD80/CD86 or MHC-II with high T-cell infiltration. These molecules could potentially increase the effects of ICIs, particularly inducing a durable response. CD80/CD86 and MHC-II can be predictive biomarkers of ICIs in TETs, promoting the development of drugs for such TETs.

Near-Infrared-Responsive Hydrocarbons Designed by π-Extension of Indeno[1,2,3,4-pgra]perylene at the 1,2,12-Positions.

The relationship between the overall electronic structure of π-conjugated molecules and the arrangement of their constituent elements is of fundamental importance. Establishing rational design guidelines for conjugated hydrocarbons with narrow HOMO-LUMO gaps is useful to develop near-infrared (NIR) responsive dyes and redox-active materials. This study describes the synthesis and properties of three conjugated hydrocarbons, i. e., an indenonaphthoperylene, an indenoterrylene, and a diindenoterrylene. These molecules exhibit NIR absorption despite the absence of significant antiaromaticity and diradical character. Notably, the indenonaphthoperylene exhibits red-to-NIR emission in the 620-850 nm region. The indenoterrylene and the diindenoterrylene exhibit NIR absorption tailing to 870 and 940 nm, respectively. Moreover, the effect of the π-extension of indenoperylene is disclosed in order to propose guidelines for achieving a narrow HOMO-LUMO gap with negligible antiaromaticity and diradical character.

Facile Formation of Stable Neutral Radicals and Cations from [22]Smaragdyrin BF2 Complexes.

meso-Trimesityl-substituted [20]smaragdyrin freebase was synthesized by p-toluenesulfonic acid catalyzed reaction of 5-mesityldipyrromethane and 2,14-dibromodipyrrin in an improved yield of 63 %. Unexpectedly, treatment of the [20]smaragdyrin freebase with BF3 ⋅ OEt2 and triethylamine (TEA) gave a stable radical species, in which the BF2 unit is coordinated at the tripyrrin site, probably by ready release of a hydrogen atom of a [22]smaragdyrin BF2 complex. Similar treatment of [22]smaragdyrin free base produced another [22]smaragdyrin BF2 complex, in which the BF2 unit is coordinated at the dipyrrin site. The tripyrrin site coordinated neutral radical was oxidized with AgSbF6 to give a stable antiaromatic cation; this was reduced with NaBH4 to its 22π congener, which was easily oxidized back to the neutral radical in the air and rearranged to thermodynamically stable dipyrrin site coordinated [22]smaragdyrin BF2 complex upon treatment with BF3 ⋅ OEt2 and TEA. Further, the dipyrrin site coordinated [22]smaragdyrin BF2 complex was similarly oxidized to a stable neutral radical and a stable cation in a stepwise manner. This work demonstrates a rare ability of smaragdyrin BF2 complexes to exist in multiple redox states, particularly forming a stable neutral radical by facile release of a hydrogen atom.

Predicting pathological highly invasive lung cancer from preoperative [18F]FDG PET/CT with multiple machine learning models.

PURPOSE: The efficacy of sublobar resection of primary lung cancer have been proven in recent years. However, sublobar resection for highly invasive lung cancer increases local recurrence. We developed and validated multiple machine learning models predicting pathological invasiveness of lung cancer based on preoperative [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) and computed tomography (CT) radiomic features. METHODS: Overall, 873 patients who underwent lobectomy or segmentectomy for primary lung cancer were enrolled. Radiomics features were extracted from preoperative PET/CT images with the PyRadiomics package. Seven machine learning models and an ensemble of all models (ENS) were evaluated after 100 iterations. In addition, the probability of highly invasive lung cancer was calculated in a nested cross-validation to assess the calibration plot and clinical usefulness and to compare to consolidation tumour ratio (CTR) on CT images, one of the generally used diagnostic criteria. RESULTS: In the training set, when PET and CT features were combined, all models achieved an area under the curve (AUC) of ≥ 0.880. In the test set, ENS showed the highest mean AUC of 0.880 and smallest standard deviation of 0.0165, and when the cutoff was 0.5, accuracy of 0.804, F1 of 0.851, precision of 0.821, and recall of 0.885. In the nested cross-validation, the AUC of 0.882 (95% CI: 0.860-0.905) showed a high discriminative ability, and the calibration plot indicated consistency with a Brier score of 0.131. A decision curve analysis showed that the ENS was valid with a threshold probability ranging from 3 to 98%. Accuracy showed an improvement of more than 8% over the CTR. CONCLUSION: The machine learning model based on preoperative [18F]FDG PET/CT images was able to predict pathological highly invasive lung cancer with high discriminative ability and stability. The calibration plot showed good consistency, suggesting its usefulness in quantitative risk assessment.

Heptagon-Embedded π-Expanded Thieno- and N-Methylpyrrolo-Pyridazines with Substantial Out-of-Plane Dipole Moment.

Herein, we describe the synthesis and characterization of fully fused tetraphenylthieno[3,4-d]pyridazine 1 and N-methylpyrrolo[3,4-d]pyridazine 2 with two embedded seven-membered rings. Owing to the incorporated heptagon, 1 and 2 exhibited Cs-symmetric saddle conformations in the solid state with mean plane deviation around 0.38 Å. π-Expanded thienopyridazine 1 showed a one-dimensional (1-D) columnar packing along the b axis with net dipole moment aligning perpendicular to the b axis in the polar crystal system Pc. On the other hand, 2 formed a partially π-stacked brick-work structure. In addition to the Cs-symmetric saddle conformations found in the crystals, density functional theory (DFT) calculation found C2-symmetric twisted conformations of both 1 and 2 close in energy to the saddle conformations. The barrier of conformational interconversion was calculated to be 32 (1) and 31 kJ·mol-1 (2), and the interconversion occurs fast even at -60 °C as evidenced by variable-temperature (VT)-NMR studies. While 1 and 2 have moderately curved structures, optical and electrochemical studies revealed effective π-conjugation over the fused diphenylene units, which is also supported by DFT calculation. As the result of the intrinsic large dipole moment of thieno- and pyrrolo-pyridazines and the notably curved structure, 1 (2) has a substantial out-of-plane dipole moment of 2.0 (3.3) D in the saddle conformations.

π-Expansion of 2,3,6,7-Tetraazanaphthalene with Two Embedded Heptagons: Highly Twisted Structure and Lone-Pair/π* Interaction in the Crystal.

Synthesis and characterization of doubly diphenylene-fused 2,3,6,7-tetraazanaphthalene 1 are described. Single-crystal X-ray diffraction analysis showed the highly twisted structure of 1 with a degree of twisting of 13.0°/Å, which is one of the largest values for a π-system. In the crystal, molecules of 1 formed an orthogonal one-dimensional column with π-stacking of diphenylene moieties and a short intermolecular C···N distance due to lone-pair/π* interaction, which is a rare example of lone-pair/π* interaction in a supramolecular assembly.

Doubly linked chiral phenanthrene oligomers for homogeneously π-extended helicenes with large effective conjugation length.

Helically twisted conductive nanocarbon materials are applicable to optoelectronic and electromagnetic molecular devices working on the nanometer scale. Herein, we report the synthesis of per-peri-perbenzo[5]- and [9]helicenes in addition to previously reported π-extended [7]helicene. The homogeneously π-extended helicenes can be regarded as helically fused oligo-phenanthrenes. The HOMO-LUMO gap decreased significantly from 2.14 to 1.15 eV with increasing helical length, suggesting the large effective conjugation length (ECL) of the π-extended helical framework. The large ECL of π-extended helicenes is attributed to the large orbital interactions between the phenanthrene subunits at the 9- and 10-positions, which form a polyene-like electronic structure. Based on the experimental results and DFT calculations, the ultrafast decay dynamics on the sub-picosecond timescale were attributed to the low-lying conical intersection.

Large Enhancement of the Single-Molecular Conductance of a Molecular Wire through a Radical Substituent.

Invited for the cover of this issue are Ryuto Yasui, Daiki Shimizu, and Kenji Matsuda at Kyoto University. The image depicts a comparison of the molecular conductance of radical-substituted and non-radical-substituted molecular wires evaluated by STM. Read the full text of the article at 10.1002/chem.202104242.

Large Enhancement of the Single-Molecular Conductance of a Molecular Wire through a Radical Substituent.

The single-molecular conductance between two π-conjugated wires with and without a radical substituent has been compared. Specifically, methyl- and iminonitroxide-substituted 4-(biphenyl-4-yl)pyridine wires bound onto a porphyrin template were subjected to scanning tunneling microscopy (STM) apparent-height measurement at the interface between highly oriented pyrolytic graphite (HOPG) and octan-1-oic acid. Statistical analysis of the STM images revealed that the radical-substituted wire has 3.2±1.7-fold higher conductance than the methyl-substituted reference. Although density functional theory (DFT) calculation suggests that only 17 % of the SOMO is distributed on the wire moiety, the effect was significant. This study presents the potential of radical substituents to achieve high conductivity in molecular wires.

Formation of Stable NiIII N-Confused Porphyrins Aided by a 3-Ethoxy Group.

We report the synthesis, characterization, and reactivities of two stable NiIII N-confused porphyrin (NCP) complexes. Metalation of 3-OEt NCP 1 with NiCl2 ⋅ 6H2 O in CHCl3 /EtOH gave 3-OEt NiII NCP 3 initially, which was easily oxidized in air to form the NiIII complex of NCP inner C-oxide 4. Bis-ethoxy-modified NiIII complex 5 was synthesized by oxidation of 3 with PIFA in ethanol and CHCl3 . The structures of 4 and 5 were determined by single-crystal X-ray diffraction analysis. An unusually long NiIII -C bond (2.170(9) Å) was observed in 4. The g-factor (g>2.1) observed in the EPR spectra of 4 and 5 further confirmed that they are paramagnetic NiIII complexes. Comparative experiments showed that the 3-ethoxy group plays an important role in the formation of 4 and 5. Reduction of 4 and 5 with NaBH4 regenerated complex 3.

Expression level of BTN3A1 on the surface of CD14+ monocytes is a potential predictor of γδ T cell expansion efficiency.

Human γδ T cells expressing Vγ9Vδ2 T cell receptors exert a robust response to pathogens and malignant cells. These cells are activated by BTN3A1, which is expressed by pathogen-derived phosphoantigens (pAgs) or host-derived pAgs that accumulate in transformed cells or in cells exposed to aminobisphosphonates. Activated Vδ2 (+) T cells exert multiple effector functions; therefore, they are a promising candidate for immunotherapy. However, not all donors have γδ T cells with adequate proliferative activity. Here, we performed ex vivo culture of γδ T cells from 20 healthy donors and explored factors that may affect their expansion efficiency. Consistent with previous studies, we found that amplification of γδ T cells requires CD14+ monocytes to act as accessory cells. We also show here that surface expression of BTN3A1 by monocytes correlates positively with γδ T cell expansion. Moreover, treatment with BTN3A1-Fc increased the expansion efficiency of peripheral blood mononuclear cells (PBMCs) from donors harboring γδ T cells with poor expansion capacity. Taken together, the data suggest that the level of BTN3A1 expressed on the surface of monocytes is a useful biomarker for predicting the degree of expansion of γδ T cells.

Human Vγ9Vδ2 T cells exert anti-tumor activity independently of PD-L1 expression in tumor cells.

Human γδ T cells expressing Vγ9Vδ2 T cell receptors play a crucial role in the innate immune system and have an attracted interest as effector cells in adoptive cellular immunotherapy. However, the efficacy of adoptive cellular immunotherapy for the treatment of tumors requires overcoming the immunosuppressive microenvironment. αß T cell inhibition in the tumor microenvironment is associated with programmed death-ligand 1 (PD-L1) expression level. Vγ9Vδ2 T cells (abbreviated as γδ T cells here) exert potent cytotoxic effects in various cancers; however, γδ T cell activity in relation to the level of PD-L1 expression in cancer cells remains unclear, and the association between the PD-1/PD-L1 axis and γδ T cell cytotoxicity needs to be investigated. In this study, PD-1 blockade did not increase the cytotoxicity of γδ T cells against PD-L1high cancer cells. However, the anti-PD-L1 monoclonal antibody (mAb) enhanced the cytotoxicity of γδ T cells against a subset of cancer cells, whereas PD-L1 knockdown did not increase the cytotoxicity of γδ T cells. We also found that the expression levels of PD-L1 were positively correlated with the changes of γδ T cells cytotoxicity induced by anti-PD-L1 mAb. These observations suggest that anti-PD-L1 mAb treatment adds ADCC activity to the cytotoxicity of γδ T cells itself against PD-L1high cancer cells. The present results suggest that ex vivo expanded γδ T cells have antitumor activity independently of PD-L1 expression and may be promising effector cells for γδ T cell immunotherapy.

Circularly Polarized Luminescence Designed from Molecular Orbitals: A Figure-Eight-Shaped [5]Helicene Dimer with D2 Symmetry.

Although many chiral molecules exhibiting circularly polarized luminescence (CPL) have been reported recently, few molecular design guidelines are known for increasing the dissymmetry factor for CPL (glum). We demonstrate that a figure-eight-shaped molecule with D2 symmetry has excellent chiroptical properties (Φf = 0.08, |glum| = 1.5 × 10-2), which are attributed to the parallel arrangement of µ and m as well as a good |µ|/|m| ratio.

Balancing Charge Transfer and Frenkel Exciton Coupling Leads to Excimer Formation in Molecular Dimers: Implications for Singlet Fission.

Photoexcitation of molecular chromophore aggregates can form excimer states that play a significant role in photophysical processes such as charge and energy transfer as well as singlet fission. An excimer state is commonly defined as a superposition of Frenkel exciton and charge transfer states. In this work, we investigate the dynamics of excimer formation and decay in π-stacked 9,10-bis(phenylethynyl)anthracene (BPEA) covalent dimers appended to a xanthene spacer, where the electronic coupling between the two BPEA molecules is adjusted by changing their longitudinal molecular slip distances. Using exciton coupling calculations, we quantify the relative contributions of Frenkel excitons and charge transfer states and find that there is an upper and lower threshold of the charge transfer contribution for efficient excimer formation to occur. Knowing these thresholds can aid the design of molecular aggregates that optimize singlet fission.

Figure-eight Octaphyrin Bis-Ge(IV) Complexes: Synthesis, Structures, Aromaticity, and Chiroptical Properties.

Highly twisted structures of expanded porphyrin provide a prominent basis to unravel the relationship between aromaticity and chirality. Here we report the synthesis of bis-Ge(IV) complexes of [38]octaphyrin that display rigid figure-eight structures. Two bis-Ge(IV) [38]octaphyrin isomers with respect to the stereochemistry of the axial hydroxy groups on the germanium ions were obtained and found to be aromatic. Upon oxidation with MnO2 , these [38]octaphyrin complexes were converted to a single syn-type isomer of [36]octaphyrin with retained figure-eight conformation. The enantiomers have been successfully separated by HPLC equipped with a chiral stationary phase. While aromatic [38]octaphyrin Ge(IV) complexes showed quite large molar circular dichroism of up to Δϵ=1500 M-1 cm-1 with a dissymmetry factor gabs of 0.035, weakly antiaromatic [36]octaphyrin Ge(IV) complexes underscored moderate values; Δϵ=540 M-1 cm-1 with gabs of 0.023. Thus, the figure-eight octaphyrin scaffold has been proved to be an attractive platform for novel chiroptical materials with tunable aromaticity.