Organoboron-based multiple-resonance emitters: synthesis, structure-property correlations, and prospects.

Boron-based multiple-resonance (MR) emitters exhibit the advantages of narrowband emission, high absolute photoluminescence quantum yield, thermally activated delayed fluorescence (TADF), and sufficient stability during the operation of organic light-emitting diodes (OLEDs). Thus, such MR emitters have been widely applied as blue emitters in triplet-triplet-annihilation-driven fluorescent devices used in smartphones and televisions. Moreover, they hold great promise as TADF or terminal emitters in TADF-assisted fluorescence or phosphor-sensitised fluorescent OLEDs. Herein we comprehensively review organoboron-based MR emitters based on their synthetic strategies, clarify structure-photophysical property correlations, and provide design guidelines and future development prospects.

π-Extended 9b-Boraphenalenes: Synthesis, Structure, and Physical Properties.

Boraphenalenes, compounds in which one carbon atom in the phenalenyl skeleton is replaced with a boron atom, have attracted attention for their solid-state and electronic structures; however, the construction of boraphenalene skeletons remains challenging because of the lack of suitable methods. Through this study, we showed that the tandem borylative cyclization of C3-symmetric dehydrobenzo[12]annulenes produces a new class of fully fused boron-atom-embedded polycyclic hydrocarbons possessing a 9b-boraphenalene skeleton. The obtained compounds exhibited high electron-accepting characteristics, and their two-step redox process was reversible in the reductive region, involving interconversion of 9b-boraphenalene between Hückel aromaticity and antiaromaticity. Notably, the benzo[b]fluorene-fused derivative exhibited a stepwise single-crystal-to-single-crystal (SCSC) phase transition triggered by thermal annealing. Intermolecular electron coupling calculation of the crystal structures suggested a significant improvement of charge transporting ability associated with the SCSC phase transition. Moreover, adequate photoconductivity was observed for the single crystals before and after the SCSC phase transition through flash photolysis-time-resolved microwave conductivity.

"Core-Shell" Wave Function Modulation in Organic Narrowband Emitters.

Efficient red-green-blue primary luminescence with an extraordinarily narrow band and durability is crucial for advanced display applications. Recently, the emergence of multiple-resonance (MR) from short-range atomic interactions has been shown to induce extremely narrow spectral widths in pure organic emitters. However, achieving wide-range color tuning without compromising color purity remains a persistent challenge for MR emitters. Herein, the concept of electronic donor/acceptor "core-shell" modulation is proposed within a boron/nitrogen (B/N) MR skeleton, enabling the rational utilization of intramolecular charge transfer to facilitate wavelength shift. The dense B atoms localized at the center of the molecule effectively compress the electron density and stabilize the lowest unoccupied molecular orbital wave function. This electron-withdrawing core is embedded with peripheral electron-donating atoms. Consequently, doping a single B atom into a deep-blue MR framework led to a profound bathochromic shift from 447 to 624 nm (∼0.8 eV) while maintaining a narrow spectral width of 0.10 eV in this pure-red emitter. Notably, organic light-emitting diodes assisted by thermally activated delayed fluorescence molecules achieved superb electroluminescent stability, with an LT99 (99% of the initial luminance) exceeding 400 h at an initial luminance of 1000 cd m-2, approaching commercial-level performance without the assistance of phosphors.

Intrauterine exposure to chorioamnionitis and neuroanatomical alterations at term-equivalent age in preterm infants.

PURPOSE: Infants born to mothers with chorioamnionitis (CAM) are at increased risk of developing adverse neurodevelopmental disorders in later life. However, clinical magnetic resonance imaging (MRI) studies examining brain injuries and neuroanatomical alterations attributed to CAM have yielded inconsistent results. We aimed to determine whether exposure to histological CAM in utero leads to brain injuries and alterations in the neuroanatomy of preterm infants using 3.0- Tesla MRI at term-equivalent age. METHODS: A total of 58 preterm infants born before 34 weeks of gestation at Nagoya University Hospital between 2010 and 2018 were eligible for this study (CAM group, n = 21; non-CAM group, n = 37). Brain injuries and abnormalities were assessed using the Kidokoro Global Brain Abnormality Scoring system. Gray matter, white matter, and subcortical gray matter (thalamus, caudate nucleus, putamen, pallidum, hippocampus, amygdala, and nucleus accumbens) volumes were evaluated using segmentation tools (SPM12 and Infant FreeSurfer). RESULTS: The Kidokoro scores for each category and severity in the CAM group were comparable to those observed in the non-CAM group. White matter volume was significantly smaller in the CAM group after adjusting for covariates (postmenstrual age at MRI, infant sex, and gestational age) (p = 0.007), whereas gray matter volume was not significantly different. Multiple linear regression analyses revealed significantly smaller volumes in the bilateral pallidums (right, p = 0.045; left, p = 0.038) and nucleus accumbens (right, p = 0.030; left, p = 0.004) after adjusting for covariates. CONCLUSIONS: Preterm infants born to mothers with histological CAM showed smaller volumes in white matter, pallidum, and nucleus accumbens at term-equivalent age.

One-Shot Construction of BN-Embedded Heptadecacene Framework Exhibiting Ultra-narrowband Green Thermally Activated Delayed Fluorescence.

BN-embedded nonacene, tridecacene, and heptadecacene frameworks were constructed using one-shot quadruple, sextuple, and octuple borylation reactions, respectively. The key to success is the judicious choice of borylating reagents and long-chain alkyl-substituted carbazolyl groups as boron-trapping groups, which suppressed the decrease in HOMO energy and insolubilization associated with borylation. Based on the product yields, each electrophilic C-H borylation proceeded in >99% yield, which is the best efficiency reported so far for C-H borylation reactions. Owing to the multiple resonance effects of boron and nitrogen, the prepared acenes exhibited ultra-narrowband green thermally activated delayed fluorescence with full-width at half-maximum of 12-16 nm; moreover, their kRISC values were in the order of 105 s-1. We fabricated an organic light-emitting diode by employing the nonacene as an emitter, which exhibited high external quantum efficiency (EQE) of 28.7%. The device also showed a minimum efficiency roll-off with an EQE of 25.8% at 1000 cd m-2.

Sequential Multiple Borylation Toward an Ultrapure Green Thermally Activated Delayed Fluorescence Material.

Multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitters have emerged as an important component of organic light-emitting diodes (OLEDs) because of their narrowband emission and high exciton utilization efficiency. However, the chemical space of MR-TADF emitters remains mostly unexplored because of the lack of suitable synthetic protocols. Herein, we demonstrate a sequential multiple borylation reaction that provides new synthetically accessible chemical space. ω-DABNA, the proof-of-concept material, exhibited narrowband green TADF with a full width at half-maximum of 22 nm and a small singlet-triplet energy gap of 13 meV. The OLED employing it as an emitter exhibited electroluminescence at 512 nm, with Commission International de l'Éclairage coordinates of (0.13, 0.73) and a high external quantum efficiency (EQE) of 31.1%. Moreover, the device showed minimum efficiency roll-off, with an EQE of 29.4% at 1000 cd m-2.

Stereoselective Synthesis and Characterization of Indenone Azine-Based Electron-Accepting π-Conjugated Systems.

Indenone azines, in which the exocyclic C=C bond in dibenzopentafulvalene is replaced by an azine moiety (C=N-N=C), have been synthesized as novel electron-accepting π-conjugated scaffolds. Structural modulation at the 7,7'-positions of indenone azines enabled stereoselective syntheses of diastereomers in which the configurations of the two C=N bonds are E,E or Z,Z. X-ray crystallographic analyses revealed that all the indenone azines exhibit high coplanarity in contrast to the twisted frameworks of dibenzopentafulvalene derivatives, resulting in the formation of densely π-stacked structures. Electrochemical measurements and quantum chemical calculations revealed the electron-accepting character of indenone azines comparable to isoindigo dyes. In particular, the intramolecular hydrogen bonds of 7,7'-dihydroxy-substituted derivatives impart enhanced electron-accepting character and significantly red-shifted photoabsorption. This study demonstrates that indenone azines represent a promising candidate as electron-accepting building blocks for optoelectronic materials.

Stereoselective Synthesis and Characterization of Indenone Azine-Based Electron-Accepting π-Conjugated Systems.

Invited for the cover of this issue is the group of Aiko Fukazawa at Kyoto University. The image depicts a N-N component replacing the one originally located between the exocyclic C=C bond of a cross-conjugated dibenzofulvalene. Read the full text of the article at 10.1002/chem.202300181.

Current status of neonatal jaundice management in Japan.

BACKGROUND: This nationwide survey aimed to determine the status of jaundice management in Japan. METHODS: A questionnaire about bilirubin level measurements and neonatal jaundice treatment was sent to 330 institutions providing neonatal care. The responses were analyzed according to institution level. RESULTS: Of 330 institutions, 172 responded (52.1% response rate). Total bilirubin levels were measured in the central laboratory using spectrophotometry at 134 institutions and a blood gas analyzer at 81 institutions. Unbound bilirubin (UB) levels were measured by 79 institutions, while transcutaneous bilirubin measurements were taken at 63 institutions. There was no association between institution level and UB or transcutaneous bilirubin measurement. For phototherapy criteria, the Murata-Imura criteria were adopted by 67 institutions, Nakamura criteria by 36, and Morioka criteria by 39. Light-emitting diodes (LED) were used by 160 institutions versus fluorescent lights by 31. When a blue LED was used, 119 institutions used the high mode. There is no standard for increasing light intensity. No association was found between institution level and phototherapy criteria. UB was measured in 14 of 63 institutions using the Murata-Imura criteria. CONCLUSIONS: There is a large variation in the management and treatment of neonatal jaundice among institutes in Japan.

Mortality and morbidity of extremely low birth weight infants in Japan, 2015.

BACKGROUND: In Japan, the mortality rate of extremely low birth weight (ELBW) infants is notably low in comparison with other developed countries, but the prevalence of chronic lung disease (CLD) and retinopathy of prematurity (ROP) is relatively high. This study aimed to estimate the mortality and morbidity of ELBW infants born in 2015 who were admitted to neonatal intensive care units (NICUs) in Japan and to examine the factors that affected the short-term outcomes of these infants. We also compared the mortality of ELBW infants born in 2005, 2010, and 2015. METHODS: We analyzed the mortality, morbidity, and factors related to short-term outcomes of ELBW infants, using data from 2782 infants born in 2015 and registered at NICUs in Japan. RESULTS: The mortality rates during NICU stays were 17.0%, 12.0%, and 9.8% for ELBW infants born in 2005, 2010, and 2015, respectively. Among ELBW infants born in 2015, multiple logistic regression analysis showed that short gestational age and low birthweight Z-score contributed to the increased risk of death. Births by cesarean section and antenatal corticosteroid administration were significantly associated with a reduced risk of death. Among infants who survived, CLD was observed in 53.1% and ROP requiring treatment was observed in 30.4%. CONCLUSIONS: Mortality in ELBW infants decreased significantly from 2005 to 2015. As CLD and ROP may affect quality of life and long-term outcomes of infants who survived, prevention strategies and management for these complications are critical issues in neonatal care in Japan.

Antenatal corticosteroids-to-delivery interval associates cord blood S100B levels.

AIM: Antenatal corticosteroids (ACS) are recommended for women at risk of preterm birth before 34 weeks' gestation. However, adverse effects of ACS on the fetal brain have also been reported. The time interval from ACS administration to delivery (ACS-to-delivery interval) might alter the effect of ACS on the fetal brain. This study aimed to evaluate the effect of ACS-to-delivery interval on cord blood S100 calcium-binding protein B (S100B) levels as a biomarker of brain damage. METHODS: Women who delivered between 2012 and 2020 at a tertiary medical center were divided into three groups according to ACS use and ACS-to-delivery interval, retrospectively: non-ACS, ACS ≤7 days, and ACS >7 days. Patients who did not complete the ACS regimen were excluded. The primary outcome was cord blood S100B levels. RESULTS: Cord blood S100B levels were significantly lower in the ACS ≤7 days group than in the non-ACS and ACS >7 days groups. In the multiple regression analysis, birth ≤7 days after ACS showed a significant negative association with S100B level (p < 0.001). CONCLUSIONS: Reduced S100B levels were observed in infants born ≤7 days after ACS but not in infants born >7 days after ACS. These findings suggest the importance of ACS timing to optimize its effects on the fetal brain, although further studies are required to identify these mechanisms.

Antenatal prediction models for outcomes of extremely and very preterm infants based on machine learning.

PURPOSE: Predicting individual risks for adverse outcomes in preterm infants is necessary for perinatal management and antenatal counseling for their parents. To evaluate whether a machine learning approach can improve the prediction of severe infant outcomes beyond the performance of conventional logistic models, and to identify maternal and fetal factors that largely contribute to these outcomes. METHODS: A population-based retrospective study was performed using clinical data of 31,157 infants born at < 32 weeks of gestation and weighing ≤ 1500 g, registered in the Neonatal Research Network of Japan between 2006 and 2015. We developed a conventional logistic model and 6 types of machine learning models based on 12 maternal and fetal factors. Discriminative ability was evaluated using the area under the receiver operating characteristic curves (AUROCs), and the importance of each factor in terms of its contribution to outcomes was evaluated using the SHAP (SHapley Additive exPlanations) value. RESULTS: The AUROCs of the most discriminative machine learning models were better than those of the conventional models for all outcomes. The AUROCs for in-hospital death and short-term adverse outcomes in the gradient boosting decision tree were significantly higher than those in the conventional model (p = 0.015 and p = 0.002, respectively). The SHAP value analyses showed that gestational age, birth weight, and antenatal corticosteroid treatment were the three most important factors associated with severe infant outcomes. CONCLUSION: Machine learning models improve the prediction of severe infant outcomes. Moreover, the machine learning approach provides insight into the potential risk factors for severe infant outcomes.

Antenatal corticosteroids and outcomes of small for gestational age infants born at 24-31 gestational weeks: a population-based propensity score matching analysis.

PURPOSE: To evaluate the effect of antenatal corticosteroid (ACS) treatment on neonatal outcomes in small for gestational age (SGA) infants born at 24-31 gestational weeks compared with non-SGA infants. METHODS: A population-based retrospective study was conducted that analyzed clinical data from the Neonatal Research Network of Japan database, which enrolls neonates born at < 32 gestational weeks and weighing 1500 g or less (n = 22,414). Propensity score matching (with the ratio of ACS to no-ACS groups of 1:1) was performed in SGA (n = 7028) and non-SGA (n = 15,386) infants, respectively. Univariate logistic and interaction analyses were performed to compare the short-term neonatal outcomes of infants with and without ACS treatment in utero. RESULTS: In the SGA and non-SGA infants, ACS treatment significantly reduced in-hospital mortality (odds ratio 0.67 95% confidence interval [0.50-0.88] and 0.62 [0.50-0.78], respectively), respiratory distress syndrome (0.77 [0.69-0.87] and 0.63 [0.58-0.68], respectively), and composite adverse outcomes (0.73 [0.58-0.91] and 0.57 [0.50-0.65], respectively). ACS treatment also significantly reduced intraventricular hemorrhage (grade III/IV), periventricular leukomalacia, and sepsis in the non-SGA infants, but not in the SGA infants. However, interaction analyses revealed no significant differences between the SGA and non-SGA infants in the efficacy of ACS treatment on short-term outcomes except for respiratory distress syndrome. CONCLUSIONS: ACS treatment was associated with beneficial effects on mortality, respiratory distress syndrome, and adverse composite outcomes in extremely and very preterm SGA infants, with similar efficacy on all neonatal outcomes except for respiratory distress syndrome observed in the non-SGA infants.

Spiroborate-Based Host Materials with High Triplet Energies and Ambipolar Charge-Transport Properties.

Organic light-emitting diodes (OLEDs) receive considerable attention because of their commercial use in flat panel displays. Herein, highly efficient spiroborate-based host materials are reported for use in blue OLEDs. Our designed spiroborates (SBOX) were simple to synthesize and exhibited high triplet excitation energies, narrow S-T gaps, and balanced charge carrier mobilities. A blue OLED containing one of the designed spiroborates, SBON, as a host exhibited a high external quantum efficiency (27.6 %) and low turn-on voltage (3.7 V) compared to those observed using 3,3'-di(9H-carbazol-9-yl)-1,1'-biphenyl (17.6 % and 4.5 V, respectively), indicating their potential as host materials in OLEDs.

Pulmonary hypertension with bronchopulmonary dysplasia: Aichi cohort study.

BACKGROUND: The incidence of pulmonary hypertension (PH) associated with bronchopulmonary dysplasia (BPD) has not been investigated in regional cohorts. The aim of this study was to clarify the incidence of PH associated with BPD in all very low birthweight infants (VLBWIs) born during the study period in Aichi Prefecture, Japan. METHODS: We conducted a retrospective observational cohort study of all VLBWIs born in Aichi Prefecture. The inclusion criteria were VLB, birth between 1 January 2015 and 31 December 2015, and admission to any neonatal intensive care unit in Aichi Prefecture. BPD28d and BPD36w were defined as the need for supplemental oxygen or any respiratory support at 28 days of age or 36 weeks of postmenstrual age (PMA). The primary outcome was the incidence of PH after 36 weeks' PMA (PH36w) in VLBWIs with BPD28d and BPD36w. The secondary outcomes were the clinical factors related to PH36w in BPD36w patients. Mann-Whitney U-test and Fisher's exact test were used for univariate analysis. Differences were considered statistically significant at P < 0.05. Risk ratio (RR) and 95% confidence interval (CI) were also evaluated. RESULTS: A total of 441 patients were analyzed. A total of 217 and 131 patients met the definition of BPD28d and BPD36w, respectively. Nine patients were diagnosed with PH36w (4.2% and 6.9% of the BPD28d and BPD36w patients, respectively). The presence of oligohydramnios (RR, 2.71; 95% CI: 1.55-4.73, P = 0.014) and sepsis (RR, 3.62; 95% CI: 1.51-8.63, P = 0.025) was significant in the PH36w patients. CONCLUSIONS: The incidence of PH36w was 4.2% and 6.9% in the BPD28d and BPD36w patients, respectively. Oligohydramnios and sepsis were significantly associated with PH36w in VLBWIs.

A predictive scoring system for small diaphragmatic defects in infants with congenital diaphragmatic hernia.

PURPOSE: To develop a predictive score for small diaphragmatic defects in infants with congenital diaphragmatic hernia (CDH) for determining thoracoscopic surgery indication. METHODS: The Japanese CDH Study Group cohort was randomly divided into derivation (n = 397) and validation (n = 396) datasets. Using logistic regression, a prediction model and weighted scoring system for small diaphragmatic defects were created from derivation dataset and validated with validation dataset. RESULTS: Six weighted variables were selected: no hydramnios, 1 point; 1 min Apgar score of 5-10, 1 point; apex type of the lung (left lung is detected radiographically in apex area), 1 point; oxygenation index < 8, 1 point; abdominal nasogastric tube (tip of the nasogastric tube is detected radiographically in the abdominal area), 2 points; no right-to-left flow of ductus arteriosus, 1 point. In validation dataset, rates of small diaphragmatic defects for Possible (0-3 points), Probable (4-5 points), and Definite (6-7 points) groups were 36%, 81%, and 94%, respectively (p < 0.001). Additionally, sensitivity, specificity, positive predictive value, and C statistics were 0.78, 0.79, 0.88, 0.76, and 0.45, 0.94, 0.94, 0.70 for Probable and Definite groups, respectively. CONCLUSION: Our scoring system effectively predicted small diaphragmatic defects in infants with CDH.

Prenatal predictors of mortality in fetuses with congenital diaphragmatic hernia: a systematic review and meta-analysis.

PURPOSE: This study aimed to evaluate prenatal predictors of mortality in fetuses with congenital diaphragmatic hernia (CDH). METHODS: A systematic literature search was performed to identify relevant observational studies that evaluated the ability of lung-to-head ratio (LHR), observed-to-expected LHR (o/e-LHR), observed-to-expected total fetal lung volume (o/e-TFLV), lung-to-thorax transverse area ratio (L/T ratio), intrathoracic herniation of the liver and the stomach, and side of diaphragmatic hernia, using a threshold for the prediction of mortality in fetuses with CDH. Study quality was assessed using the QUADAS-2 tool. Hierarchical summary receiver operating characteristic curves were constructed. RESULTS: A total of 50 articles were included in this meta-analysis. The QUADAS-2 tool identified a high risk of bias in more than one domain scored in all parameters. Among those parameters, the diagnostic odds ratio of mortality with o/e-LHR < 25%, o/e-TFLV < 25%, and L/T ratio < 0.08 were 11.98 [95% confidence interval (CI) 4.65-30.89], 11.14 (95% CI 5.19-23.89), and 10.28 (95% CI 3.38-31.31), respectively. The predictive values for mortality were similar between the presence of liver herniation and retrocardiac fetal stomach position. CONCLUSIONS: This systematic review suggests that o/e-LHR, o/e-TFLV, and L/T ratio are equally good predictors of neonatal mortality in fetuses with isolated CDH.

The efficacy of the postnatal nasogastric tube position as a prognostic marker of left-sided isolated congenital diaphragmatic hernia.

PURPOSE: The prenatal diagnosis of the stomach position in congenital diaphragmatic hernia (CDH) has been a reliable prognostic factor, but few studies have focused on the postnatal position. We therefore evaluated the significance of the nasogastric (NG) tube position just after birth. METHODS: The Japanese CDH Study Group database enrolled 1037 CDH neonates over 15 years. In our multicenter retrospective study, 464 cases of left-sided isolated CDH with prenatal diagnoses were divided into two groups: NG tube below the diaphragm (BD; n = 190) or above the diaphragm (AD; n = 274). The primary outcome was the 90-day survival rate, and the secondary outcomes were mechanical ventilation duration, hospitalization duration, and recurrence rate. RESULTS: The BD group had a significantly higher 90-day survival rate (98.4 vs. 89.4%, p < 0.001), shorter mechanical ventilation (11 vs. 19 days, p < 0.001), shorter hospitalization (38 vs. 59 days, p < 0.001), and lower recurrence rate (p = 0.002) than the AD group. A multivariate analysis showed that BD (adjusted odds ratio, 3.68; 95% confidence interval 1.02-13.30) was a favorable prognostic factor for the 90-day survival. CONCLUSION: The assessment of the NG tube position revealed it to be a reliable prognostic factor of left-sided isolated CDH. Therefore, it should be included as a routine assessment.

Dithieno[a,e]pentalenes: Highly Antiaromatic Yet Stable π-Electron Systems without Bulky Substituents.

Invited for the cover of this issue are Aiko Fukazawa and co-workers at Kyoto University and Nagoya University. The image depicts the π-electrons as people to highlight the effect of fused aromatic rings in the antiaromatic π-electron systems. Read the full text of the article at 10.1002/chem.202004244.

Dithieno[a,e]pentalenes: Highly Antiaromatic Yet Stable π-Electron Systems without Bulky Substituents.

Dithieno[a,e]penalenes (DTPs) with various substituents were synthesized as a class of antiaromatic compounds. Annulation of thiophene rings imparts the pentalene moiety with high thermal stability even without bulky substituents, while retaining antiaromaticity. The higher magnitude of antiaromaticity in DTPs, in addition to the differences in the electronic structures of the fused aromatic rings, resulted in a narrower HOMO-LUMO gap than that of the corresponding dibenzo[a,e]pentalene analog, giving rise to red-shifted electronic absorption that reaches the near-infrared region. Moreover, systematic investigations on the solid-state packing structure revealed that DTPs prefer offset face-to-face packing motifs rather than face-centered π-π stacking. In particular, the thienyl-substituted DTP bearing hydrophilic side chains exhibited thermochromic behavior in polar solvents, which was ascribed to the formation of aggregates.