An η3‐Bound Allyl Ligand on Magnesium in a Mechanochemically Generated Mg/K Allyl Complex

Milling two equivalents of K[1,3‐(SiMe₃)₂C₃H₃] (=K[A′]) with MgX₂ (X=Cl, Br) produces the allyl complex [K₂MgA′₄] ( 1 ). Crystals grown from toluene are of the solvated species [((η⁶‐tol)K)₂MgA′₄] ([ 1 ?2(tol)]), a trimetallic monomer with both bridging and terminal (η¹) allyl ligands. When recrystallized from hexanes, the unsolvated 1 forms a 2D coordination polymer, in which the Mg is surrounded by three allyl ligands. The C?C bond lengths differ by only 0.028 Å, indicating virtually complete electron delocalization. This is an unprecedented coordination mode for an allyl ligand bound to Mg. DFT calculations indicate that in isolation, an η³‐allyl configuration on Mg is energetically preferred over the η¹‐ (σ‐bonded) arrangement, but the Mg must be in a low coordination environment for it to be experimentally realized. Methyl methacrylate is effectively polymerized by 1 , with activities that are comparable to K[A′] and greater than the homometallic magnesium complex [{MgA′₂}₂].     

利用手持技术探究酸碱性对高锰酸钾氧化性的影响

高锰酸钾作为常用的氧化剂,其氧化性强弱与体系酸碱性相关。通过手持技术,利用氧化还原电势(ORP)传感器和pH传感器去探究体系酸碱性对高锰酸钾氧化性的影响。实验发现:pH在酸性条件下,高锰酸钾溶液的氧化性明显增强,随着体系pH的减小,氧化性继续增强;在碱性条件下,其氧化性明显减弱,随着体系pH的增大,其氧化性继续减弱。实际实验中需要根据各种综合因素选用适宜酸碱性的高锰酸钾溶液做氧化剂。     

Wearable Multiparameter Platform Based on AlGaN/GaN High‐electron‐mobility Transistors for Real‐time Monitoring of pH and Potassium Ions in Sweat

Biosensors based on field‐effect transistor (FET) structures have attracted considerable attention because they offer rapid, inexpensive parallel sensing and ultrasensitive label‐free detection. However, long‐term repeatable detection cannot be performed, and Ag/AgCl reference electrode design is complicated, which has hindered FET biosensors from becoming truly wearable health‐monitoring platforms. In this paper, we propose a novel wearable detection platform based on AlGaN/GaN high‐electron‐mobility transistors (HEMTs). In this platform, a sweatband was used to continuously collect sweat, and a pH detecting unit and a potassium ion detecting unit were formed by modifying different sensitive films to realize the long‐term stable and repeatable detection of pH and potassium ions. Experimental data show that the wearable detection platform based on AlGaN/GaN HEMTs has good sensitivity (pH 3–7 sensitivity is 45.72 μA/pH; pH 7.4–9 sensitivity is 51.073 μA/pH; and K⁺ sensitivity is 4.94 μA/lgα_K⁺), stability (28 days) and repeatability (the relative standard deviation (RSD) of pH 3–7 sensitivity is 2.6 %, the RSD of pH 7.4–9 sensitivity is 2.1 %, and the RSD of K⁺ sensitivity is 7.3 %). Our newly proposed wearable platform has excellent potential for predictive analytics and personalized medical treatment.     

Preparation of Functionalized Aryl,Heteroaryl, and Benzylic Potassium Organometallics Using Potassium Diisopropylamide in Continuous Flow

We report the preparation of lithium‐salt‐free KDA (potassium diisopropylamide; 0.6 m in hexane) complexed with TMEDA (N,N,N′,N′‐tetramethylethylenediamine) and its use for the flow‐metalation of (hetero)arenes between ?78 °C and 25 °C with reaction times between 0.2 s and 24 s and a combined flow rate of 10 mL min^?1 using a commercial flow setup. The resulting potassium organometallics react instantaneously with various electrophiles, such as ketones, aldehydes, alkyl and allylic halides, disulfides, Weinreb amides, and Me₃SiCl, affording functionalized (hetero)arenes in high yields. This flow procedure is successfully extended to the lateral metalation of methyl‐substituted arenes and heteroaromatics, resulting in the formation of various benzylic potassium organometallics. A metalation scale‐up was possible without further optimization.     

Reversibly Switching the Charge State and Adsorption Location of A Single Potassium Atom on Ultrathin CuO Films

Potassium (K) cations are spontaneously formed upon thermal deposition of low‐coverage K onto an ultrathin CuO monolayer grown on Cu(110) and they were explored by low‐temperature scanning tunneling microscopy (STM) and X‐ray photoemission spectroscopy. The formed K cations are highly immobile and thermally stable. The local work function around an individual K cation decreases by 1.5±0.3 eV, and a charging zone underneath it is established within about 1.0 nm. The cationic and neutral states of the K atom are switchable upon application of an STM bias voltage pulse, which is simultaneously accompanied by an adsorption site relocation.     

Facile Synthesis of Dibenzopentalene Dianions and Their Application as New π‐Extended Ligands

Reduction of phenyl(silyl)ethynes with potassium followed by quenching with iodine gave dibenzopentalenes in moderate yields. The intermediates of the reactions, dipotassium dibenzopentalenides, were isolated. The first dibenzopentalene–transition‐metal complex was successfully synthesized. The ruthenium atoms are located above the six‐membered rings. However, X‐ray diffraction analysis and theoretical calculations revealed that the aromatic nature of the five‐membered rings was retained. The cyclic voltammetry of the Ru complex revealed two oxidation waves with relatively large separation.     

Heterobimetallic s‐Block Hydrides by σ‐Bond Metathesis

Reactions between PhSiH₃ and alkali‐metal diamidoalkylmagnesiates ([M{N(SiMe₃)₂}₂MgBu], M=Li, Na, K) provide either selective alkyl metathesis or the formation of polyhydride aggregates contingent upon the identity of the Group 1 metal. In the case of [M{N(SiMe₃)₂}₂MgBu], this reactivity results in a structurally unprecedented dodecametallic decahydride cluster species.     

Potassium Carbonate–Mediated Efficient and Convenient Synthesis of 3-Methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones

Unprecedented cyclization was observed during N-sulfonylation of 3-[1-(phenylhydrazono)-ethyl]-chromen-2-one in pyridine, affording 3-methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones. To avoid use of noxious pyridine, reaction was tried in different basic conditions and the best results were obtained with potassium carbonate in acetone. A wide range of substrates bearing either electron-donating or electron-withdrawing substituents on phenylhydrazine ring were compatible with the developed methodology. Rapid access of starting material, 3-acetylcoumarin, excellent yields of products, and use of environmentally benign base and solvent for the cyclization make this strategy an efficient and convenient method for synthesis of 3-methyl-1-phenylchromeno[4,3-c]pyrazol-4(1H)-ones.     

A B3LYP study on counterpoise-corrected geometry optimizations for hydrated complexes of [K(H2O)n] and [Na(H2O)n]

We report the basis set dependencies and the basis set superposition errors for the hydrated complexes of K⁺ and Na⁺ ions in relation to the recent studies of the KcsA potassium channel. The basis set superposition errors are estimated by the geometry optimizations at the counterpoise-corrected B3LYP level. The counterpoise optimizations alter the hydration distances by about 0.02–0.03 Å. The enthalpies and free energies for K⁺ + n(H₂O) → [K(H₂O)_n]⁺ and Na⁺ + n(H₂O) → [Na(H₂O)_n]⁺ (n = 1–6) are compared between the theoretical and experimental values. The results show that the addition of diffuse functions to K, Na, and O species are effective. However, it is also found that the counterpoise corrections using diffuse functions work so as to underestimate the free energies for the complexes with increasing the hydration number. The stabilization energies in aqueous solution are larger for a Na⁺ ion than for a K⁺ ion, suggesting the contributions of their dehydration processes to the ion selectivity of the KcsA potassium channel. The changes in coordination distance between the isolated [K(H₂O)₈]⁺ and the [K(H₂O)₈]⁺ in the KcsA potassium channel indicate the importance of hydrogen bondings between the first hydration shell and the outer hydration shells.     

胞外高钾对大鼠背根神经元超极化电流的影响

应用全细胞膜片钳技术研究了胞外高钾对大鼠背根神经元（DRG）超极化电流（Ih）的影响．结果表明,Ih随着胞外钾离子浓度的增大而增大,同时随着外加刺激电压的增高而增强．当胞外钾离子浓度[Kext]为4,8和16mmol／L时,半数激活电压V1/2分别为-98±1．9,-106±1．3（p〈0．05）和-110±1．0mV（p〈0．05）,其对应的最大电流的峰值分别为1085±340,1576±409和2124±614pA,与4mmol／L比较,后者分别增长了45％和92％．胞外高钾使,Ih激活曲线显著左移,说明高Kext改变了超极化电流的激活过程．提高细胞外钾离子浓度,可以使早期钾通道（又称快通道）的激活时间常数增大,使晚期钾通道（又称慢通道）激活时间常数减小．当胞外钾离子浓度由4mmol／L升高到8和16mmol／L时,翻转电位右移,但不具有显著性差异．结果提示,细胞外高浓度钾可增强大鼠背根神经元超极化电流,Ih,改变Ih的激活过程,从而提高了神经元的兴奋性,产生不正常的动作电位,对神经细胞产生损伤．