A dimeric o-carboranyl triarylborane compound
(2) with a biphenylene bridge group was prepared and
characterized. Also, its solid-state structure was determined via
X-ray diffraction. Treatment of 2 with an excess amount
of KF in the presence of 18-crown-6 formed a dimer-type potassium
salt, [2·F2][K·18-crown-6]2; its structure was fully confirmed by multinuclear NMR spectroscopy.
UV–vis titration experiments carried out in THF showed that 2 binds fluoride ions with a binding constant (K) of 8.5 × 105 M–1. The linear
decline of the UV/vis absorption of 2 upon titration
with fluoride suggested that the triarylborane moieties acted as independent
binding sites, which were not affected by each other. Contrary to
a single emission (λem = 376 nm) of 2 assignable to an intramolecular charge transfer (ICT) transition
at 298 K in THF, a broad low-energy emission band was additionally
observed at 77 K, which is dominant in the film state. The TD-DFT
calculation on the first excited singlet state (S1) of 2 shows that the low-energy emission band originates from
the CT nature between carborane and triarylborane groups. Aggregation-induced
emission (AIE) of 2 was clearly confirmed by enhanced
photoluminescence intensity (λem = 489 nm) upon increasing
the water fraction (f
w) in the THF solution
of 2, and it further accounts for the intense emission
in the solid state. Interestingly, the emission spectrum of a film
sample of 2 upon addition of two equivalents of fluoride
ion was was mostly similar to that of [2·F2][K·18-crown-6]2, indicating that the ICT-based AIE
nature of 2 could be red-shifted by fluoride binding.
Polysomnography (PSG) is currently considered the gold standard for assessing sleep quality. However, the numerous sensors that must be attached to the subject can disturb sleep and limit monitoring to within hospitals and sleep clinics. If data could be obtained without such constraints, sleep monitoring would be more convenient and could be extended to ordinary homes. During rapid-eye-movement (REM) sleep, respiration rate and variability are known to be greater than in other sleep stages. Hence, we calculated the average rate and variability of respiration in an epoch (30 s) by applying appropriate smoothing algorithms. Increased and irregular respiratory patterns during REM sleep were extracted using adaptive and linear thresholds. When both parameters simultaneously showed higher values than the thresholds, the epochs were assumed to belong to REM sleep. Thermocouples and piezoelectric-type belts were used to acquire respiratory signals. Thirteen healthy adults and nine obstructive sleep apnea (OSA) patients participated in this study. Kappa statistics showed a substantial agreement (kappa > 0.60) between the standard and respiration-based methods. One-way ANOVA analysis showed no significant difference between the techniques for total REM sleep. This approach can also be applied to the non-intrusive measurement of respiration signals, making it possible to automatically detect REM sleep without disturbing the subject.
Novel salen-Al/triarylborane dyad complexes were prepared and characterized with their corresponding mononuclear compounds. The UV-vis and photoluminescence experiments for dyads exhibited photoinduced energy transfer from borane to the salen-Al moiety in an intramolecular manner. Theoretical calculation and fluoride titration results further supported these intramolecular energy-transfer features.
Multiple o‐carborane substituted compounds, mono‐, 1,3‐bis‐, and 1,3,5‐tris[2‐(4‐butylphenyl)‐o‐carboran‐1‐yl]benzene (1–3), were prepared and characterized by multinuclear NMR spectroscopy and elemental analysis. The solid‐state structures of 2 and 3 were also confirmed by single‐crystal X‐ray diffraction. While the mono‐carborane compound 1 was nonemissive in the solution state at 298 K, the photoluminescence (PL) spectra of 2 and 3 exhibited weak‐to‐moderate emission (λem = 352 nm for 2 and 363 nm for 3 in THF). Compounds 2 and 3 showed intriguing dual emission bands (λem = 361 and 537 nm for 2 and λem = 387 and 520 nm for 3) at 77 K, and in film, of which the low‐energy band was dominant in the solid state. TD‐DFT calculations on the S1 optimized structures suggested that the low‐energy fluorescence of 2 and 3 was attributed to the π(4‐butylphenyl) → π*(phenylene‐o‐carborane) intramolecular charge‐transfer transition. The low‐energy electronic transition of 2 and 3 was apparently associated with aggregation‐induced emission, and an enhanced emission intensity (λem = ca. 570 nm for 2 and λem = ca. 550 nm for 3) was observed upon increasing the water fraction (fw) in THF/water mixtures. Furthermore, the PL spectroscopic experiments of poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) polymer films doped with 3 revealed the excellent electron‐accepting properties of 3.
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