Spectroscopic Measurement of a Halogen Bond Energy

Halogen bonding (XB) has emerged as an important bonding motif in supramolecules and biological systems. Although regarded as a strong noncovalent interaction, benchmark measurements of the halogen bond energy are scarce. Here, a combined anion photoelectron spectroscopy and density functional theory (DFT) study of XB in solvated Br^? anions is reported. The XB strength between the positively‐charged σ‐hole on the Br atom of the bromotrichloromethane (CCl₃Br) molecule and the Br^? anion was found to be 0.63 eV (14.5 kcal mol^?1). In the neutral complexes, Br(CCl₃Br)_1,2, the attraction between the free Br atom and the negatively charged equatorial belt on the Br atom of CCl₃Br, which is a second type of halogen bonding, was estimated to have interaction strengths of 0.15 eV (3.5 kcal mol^?1) and 0.12 eV (2.8 kcal mol^?1).     

离子选择性微电极用于原位测量离子扩散系数

扩散系数是描述物质扩散过程的重要参数,而用膜池法、放射性或荧光示踪法、分子动力学模拟等现有方法无法原位进行生物体系中离子扩散系数的实时测量。 本文利用离子选择性微电极响应迅速、高选择性、高灵敏度、高空间分辨率、对样品无污染等优势,通过分析单个植物细胞原生质体在培养液中破裂时所形成的离子浓度脉冲信号,建立了相应的点源扩散模型,推导出了描述离子浓度随时间变化的理论公式,并通过该公式对实验测得的脉冲信号进行拟合,得到了离子的扩散系数,从而建立了一种用离子选择性微电极原位测定离子扩散系数的新方法,并将其应用于芦荟细胞原生质体破裂时离子扩散系数的测定,得到了Ca²⁺、Na⁺和K⁺的扩散系数分别为(6.51±0.12)×10^-6、(2.93±0.15)×10^-5和(3.03±0.35)×10^-5 cm²/s。 对比发现,拟合得到的Ca²⁺、Na⁺和K⁺扩散系数均略高于已报道的数值(纯水中),这一现象的产生可能是因为原生质体是在低渗液中吸水膨胀,细胞膜内压力升高产生内外压力差,该压力差会加速细胞破裂时离子的扩散。 这一方法对生物体系无干扰,较好地解决了生物体系中离子扩散系数原位实时测量的难题。     

Impact of Positional Isomerism on Pathway Complexity in Aqueous Media

Pathway complexity has become an important topic in recent years due to its relevance in the optimization of molecular assembly processes, which typically require precise sample preparation protocols. Alternatively, competing aggregation pathways can be controlled by molecular design, which primarily rely on geometrical changes of the building blocks. However, understanding how to control pathway complexity by molecular design remains elusive and new approaches are needed. Herein, we exploit positional isomerism as a new molecular design strategy for pathway control in aqueous self‐assembly. We compare the self‐assembly of two carboxyl‐functionalized amphiphilic BODIPY dyes that solely differ in the relative position of functional groups. Placement of the carboxyl group at the 2‐position enables efficient pairwise H‐bonding interactions into a single thermodynamic species, whereas meso‐substitution induces pathway complexity due to competing hydrophobic and hydrogen bonding interactions. Our results show the importance of positional engineering for pathway control in aqueous self‐assembly.     

Ruthenium bipyridyl compounds with two terminal alkynyl ligands

Compounds of the form Ru(X2bipy)(PPh3)2(-C triple bond CC6H4NO2-p)2(X2bipy = 4,4'-X(2)-2,2'-bipyridine, X = Me 3a, Br 3b, I 3c) have been synthesised from the mono-alkynyl precursors Ru(X2bipy)(PPh3)2(-C triple bond CC6H4NO2-p)Cl (X = Me 2a, Br 2b, I 2c); the former are the first ruthenium bis-alkynyl compounds that also contain a bipyridyl ligand. Spectroelectrochemical investigation of 3a shows that the metal is readily oxidised to form the ruthenium(III) compound 3a+, and will also undergo a single-electron reduction at each nitro group to form 3a2-. ESR and UV/visible spectra of these redox congeners are presented. We also report the synthesis of [Ru(Me2bipy)(PPh3)2(-C triple bond CBut)(N triple bond N)][PF6] during the attempted synthesis of Ru(Me2bipy)(PPh3)2(-C triple bond CBut)2, and report its X-ray crystal structure and IR spectrum. X-Ray crystal structures of 3b and 3c(as two different solvates) are presented, and the nature of the intermolecular interactions seen therein is discussed. Z-Scan measurements on Ru(Me2bipy)(PPh3)2(-C triple bond CR)Cl (R = C6H4NO2-p2a, But, Ph, C6H4Me) are also reported, and show that Ru(Me2bipy)(PPh3)2(-C triple bond CR)Cl (R = C6H4NO2-p2a, Ph) exhibit moderate third-order non-linearities.     

Magnetic structure variation in manganese-oxide clusters

Negative-ion photoelectron spectroscopy and ab initio simulations are used to study the variation in magnetic structure in Mn(x)O(y) (x = 3, 4[semicolon] y = 1, 2) clusters. The ferrimagnetic and antiferromagnetic ground-state structures of Mn(x)O(y) are 0.16-1.20 eV lower in energy than their ferromagnetic isomers. The presence of oxygen thus stabilizes low-spin isomers relative to the preferred high-spin ordering of bare Mn(3) and Mn(4). Each cluster has a preferred overall magnetic moment, and no evidence is seen of competing states with different spin multiplicities. However, non-degenerate isomags, which possess the same spin multiplicity but different arrangements of local moments, do contribute additional features and peak broadening in the photoelectron spectra. Proper accounting for all possible isomags is shown to be critical for accurate computational prediction of the spectra.     

Comparison of model predictions with measured proton-induced production of nickel and iridium isotopes

Journal of Radioanalytical and Nuclear Chemistry - Calculations were performed to support method development for simultaneous production of Ni and Ir isotopes. The work scope included development...     

Highly stable aqueous rechargeable Zn-ion battery: The synergistic effect between NaV_6O_(15) and V_2O_5 in skin-core heterostructured nanowires cathode

The aqueous rechargeable Zn-ion batteries based on the safe,low cost and environmental benignity aqueous electrolytes are one of the most compelling candidates for large scale energy storage applications.However,pursuing suitable insertion materials may be a great challenge due to the strong electrostatic interaction between Zn^{^(2+})and cathode materials.Hence,a novel NaV₆O₁₅/V₂O₅ skin-core heterostructure nanowire is reported via a one-step hydrothermal method and subsequent calcination for high-stable aqueous Zn-ion batteries(ZIBs).The NaV₆O₁₅/V₂O₅ cathode delivers high specific capacity of 390 m Ah/g at 0.3 A/g and outstanding cycling stability of 267 m Ah/g at 5 A/g with high capacity retention over 92.3%after 3000 cycles.The superior electrochemical performances are attributed to the synergistic effect of skin-core heterostructured NaV₆O₁₅/V₂O₅,in which the sheath of NaV₆O₁₅ possesses high stability and conductivity,and the V₂O₅ endows high specific capacity.Besides,the heterojunction structure not only accelerates intercalation kinetics of Zn²⁺transport but also further consolidates the stability of the layers of V₂O₅ during the cyclic process.This work provides a new perspective in developing feasible insertion materials for rechargeable aqueous ZIBs.     

Asymmetric total synthesis of (+)-monocerin

A concise asymmetric total synthesis of (+)-monocerin has been accomplished. The cis-fused furobenzopyranone of monocerin was efficiently constructed via a Lewis acid-mediated stereoselective cyclization of 1,2,4-triols intermediate.     

Correlation of the gradient diffusion coefficients of human lactoferrin with interparticle interactions validated by photon correlation spectroscopy

The gradient diffusion coefficients of recombinant human lactoferrin, a glycoprotein that is of commercial interest, have been extensively investigated theoretically and experimentally. A theoretical prediction was developed to allow calculation of the thermodynamic coefficient in terms of the electrostatic repulsive forces, London-van der Waals forces, entropic forces and additional interactions of unknown source and determination of the hydrodynamic coefficient by a perturbation theory method. In addition, dilute limit calculations were carried out for both of them. The thermodynamic and hydrodynamic coefficients were incorporated in the generalised Stokes-Einstein equation to calculate the gradient diffusion coefficient. Dynamic light scattering experiments were also conducted under different physiochemical conditions in which the gradient diffusion coefficients and the mean sizes of the macromolecules were measured. It was shown that of the theoretical approaches studied, good quantitative agreement between theory and experiment was found.     

Highly Regio‐ and Stereoselective Hydrosilylation of Alkynes Catalyzed by Tridentate Cobalt Complexes

Several cobalt complexes bearing tridentate (NNN) ligands were synthesized and served as precatalysts for alkyne hydrosilylation with Ph₂SiH₂. For terminal alkynes, the catalyst L2 b‐CoCl₂ was selected, and resulted in the corresponding α‐vinylsilanes with high (Markovnikov) regioselectivity and extensive functional‐group tolerance. For internal diaryl alkynes, the catalyst L2 c‐CoCl₂ exhibited the best activity, and afforded E‐selective vinylsilanes through syn‐addition in excellent yield under mild conditions.