Adsorption of sodium ions and hydrated sodium ions on a hydrophobic graphite surface via cation-π interactions

Using density functional theory computation, we show that sodium ions and hydrated sodium ions can be strongly adsorbed onto a hydrophobic graphite surface via cation-π interactions. The key to this eation-π interaction is the coupling of the delocalized π states of graphite and the empty orbitals of sodium ions. This finding implies that the property of the graphite surface is extremely dependent on the existence of the ions on the surface, suggesting that the hydrophobic property of the graphite surface may be affected by the existence of the sodium ions.

4-(3-苯丙基)吡啶基于cation-π相互作用作为烷基化残留物荧光传感器

4-(3-苯丙基)吡啶发生烷基化反应所生成的吡啶盐的荧光强度显著增加,可以被用来作为烷基化残留物的荧光传感器。本文主要通过研究这种吡啶和与之对应的吡啶盐与α-环糊精通过的主客体相互作用的荧光性质验证这种cation–π相互作用存在。

Cation-πinteractions regulate electrocatalytic water oxidation over iridium single atoms supported on conjugated polymers

Designing cost-effective and high-performing metal catalysts is significant for many renewable energy conversion technologies.Lowering metal loading without sacrificing activity and durability is highly desired for the catalyst design,especially for those reactions where the noble metals deliver the best catalyzing performance.Single-atom catalysts(SACs)with maximal metalatom utilization,homogeneous and tailorable active sites have emerged as promising catalyst candidates,where the local coordination structures of the metal atoms in SACs largely determine the reaction kinetics.Previous design strategies of constructing strong metal-support interactions can stabilize the individual metal atoms in SACs,but present obstacles to provide a flexible manipulation platform for elaborately tailoring the coordination structures to achieve performance optimization towards a specifically targeted reaction.Here,for the proof-of-concept study,we report a novel design of SAC with iridium(Ir)single atoms supported on conjugated polymer,in which the adsorption energies of reaction intermediates on Ir atoms and the reaction kinetics towards acidic water oxidation can be readily optimized through modulating the formed cation-πinteractions that can be tailored by adjusting the molecular structures of conjugated polymers.This strategy establishes a general route to develop targeted SACs for various catalytic reactions.

α/β、全α和全β蛋白中的Cation-π相互作用

蛋白质的三维结构是由各种弱的相互作用所维持的。氢键、盐桥以及疏水效应在蛋白质折叠和结构的稳定性当中都起重要作用[1]。在组成蛋白质的氨基酸当中。

Research progress in cation-π interactions

Cation-π interaction is a potent intermolecular interaction between a cation and an aromatic system,which has been viewed as a new kind of binding force,as being compared with the classical interactions(e.g. hydrogen bonding,electrostatic and hydrophobic interactions). Cation-π interactions have been observed in a wide range of biological contexts. In this paper,we present an overview of the typical cation-π interactions in biological systems,the experimental and theoretical investigations on cation-π interactions,as well as the research results on cation-π interactions in our group.

The open-close mechanism of M2 channel protein in influenza A virus:A computational study on the hydrogen bonds and cation-π interactions among His37 and Trp41

The M2 protein from influenza A virus is a tetrameric ion channel. It was reported that the permeation of the ion channel is correlated with the hydrogen bond network among His37 residues and the cation-π interactions between His37 and Trp41. In the present study,the hydrogen bonding network of 4-methyl-imidazoles was built to mimic the hydrogen bonds between His37 residues,and the cation-π interactions between 4-methyl-imidazolium and indole systems were selected to represent the interac-tions between His37 and Trp41. Then,quantum chemistry calculations at the MP2/6-311G level were carried out to explore the properties of the hydrogen bonds and the cation-π interactions. The calcula-tion results indicate that the binding strength of the N-H···N hydrogen bond between imidazole rings is up to -6.22 kcal·mol-1,and the binding strength of the strongest cation-π interaction is up to -18.8 kcal·mol-1(T-shaped interaction) or -12.3 kcal·mol-1(parallel stacking interaction). Thus,the calcu-lated binding energies indicate that it is possible to control the permeation of the M2 ion channel through the hydrogen bond network and the cation-π interactions by altering the pH values.

Nanoconfining Cation-π Interactions as a Modular Strategy to Construct Injectable Self-Healing Hydrogel

Cation-πinteraction is considered one of the strongest noncovalent interactions in aqueous solutions,which endows natural biomolecules(e.g.,proteins)with robust wet adhesion and cohesion in humid/underwater environments.However,it remains a challenge to construct synthetic functional materials(e.g.,self-healing hydrogels)by adopting the cation-πinteractions rationally.Herein,we present a facile and novel strategy to fabricate injectable self-healing synthetic hydrogel from self-assembly of a thermoresponsive ABA triblock copolymer via cation-πinteractions.

Hg2＋-Selective Fluorescent Chemosensor Based on Cation-π Interaction

Two sulphur-containing 4-aminonaphthalimide derivatives were investigated as Hg2＋ fluorescent chemosensors. In CH3CN, both sensors present a remarkable fluorescence enhancement to Cu2＋ and Fe3＋, but a selective fluorescence quenching to Hg2＋ among the other metal ions. A cation-π interaction between Hg〉 and the naphthalimide moiety was proposed and confirmed By the density tunetional theory（DFT）.

Improving dispersion and delamination of graphite in biodegradable starch materials via constructing cation-π interaction: Towards microwave shielding enhancement

Herein, a low-cost, biodegradable, and high-performance microwave shielding graphite/starch material was fabricated via constructing a cation-π interaction between ammonium ions and graphite. The graphite flakes and starch were firstly mixed with distilled water containing ammonium hydroxide to form graphite/starch slurry under an ultrasonic assistant. The cation-π interaction could improve delamination degree and dispersion of graphite in starch matrix. The slurry was first used as a coating material on the surface of wood and paper to develop shielding packages. The effect of coating thickness and coating layers on EM shielding property of the materials was investigated. Second, the composites with a high orientation of graphite were fabricated by compression at high pressures. The electrical conductivity and EM shielding effectiveness(SET) of the materials were greatly enhanced by construction of cation-πinteraction and orientation of graphite. Specifically, the EM SETvalues increased from 56.9 to 66.8 d B for the composites with 50 wt.% graphite and 2.0 mm in thickness by constructing cation-π interaction. The EM SETvalues raised from 17.4 to 66.8 d B via the graphite orientation in the materials with the same components and thickness. The shielding mechanism of the compressed composites with orientation dispersion of graphite was also discussed in comparison to the coating layer with random dispersion of graphite.

Cation-π and electrostatic interactions co-driven assembly of two-dimensional heteropore supramolecular polymers with rapid iodine capture capability

Constructing two-dimensional(2D)supramolecular polymers with complicated hierarchical porosity significantly contributes to developing effective strategies to control delicate self-assembly architectures,thus facilitating the fabrication of advanced 2D organic functional materials.Here,we report utilizing cooperative cation-πand electrostatic interactions to construct a series of robust 2D heteropore supramolecular polymers(2D HPSPs)with hierarchical pore structures,in which hexagonal and rectangular pores are alternately and periodically arranged,and the pore sizes can be finely tuned.Remarkably,the as-prepared 2D HPSPs exhibit excellent iodine(I_(2))capture rate(a maximum K80%value is 2.25 g h^(-1)),and present a novel mechanism involving transport-adsorption spatiotemporal separation for rapid I_(2)capture.In this mechanism,the transport of free I_(2)is first conducted in large hexagonal pores,and then I_(2)can be preferentially adsorbed in small rectangular pores,thereby preventing the transfer channels from blocking and greatly improving the adsorption kinetics.

Acidity-dependent self-rolling of graphene oxide nanoscrolls via metal cation-πinteraction

Graphene nanoscrolls with one-dimensional topological structure obtained by Archimedean-type spirals of graphene,inherit the intrinsic properties of the pristine graphene.They have some unique advantages,including open edges/ends,adjustable internal volume,and diameter.Notably,the accommodation of functionalized components in their open interlayer is potentially a fantastic strategy to promote the epoch-making progress in nanotechnology areas,including energy storage,environmental remediation,biotechnology,and smart devices.However,it could destroy the driving forces for the self-rolling of graphene nanosheets and thus it is still a challenge to prepare functionalized graphene nanoscrolls.Here,based on density functional theory prediction,we reported a feasible method to fabricate graphene oxide nanoscrolls with carbon nanotubes as the template.The method was driven by cation-πinteractions,which were caused by metal cations that also acted as the adsorption center.Most importantly,the distinct mechanism and an acidity-dependent rule for the formation of graphene nanoscrolls were identified.Benefiting from the introduced metal cations and the macro three-dimensional hierarchical structure,the produced nanoscroll aerogel exhibited significantly improved adsorption performance toward different organic solvents with the adsorption capacities from 129.9 to 265.7 g g^(−1).This work demonstrates a simple and efficient strategy to fabricate functionalized component-accommodated graphene nanoscroll,which could find important applications in various fields.

Study on the Cation-π Interactions between Ammonium Ion and Aromatic π Systems

The nature and strength of the cation-π interactions between NH4^＋ and toluene, p-cresol, or Me-indole were studied in terms of the topological properties of molecular charge density and binding energy decomposition. The results display that the diversity in the distribution pattern of bond and cage critical points reflects the profound influence of the number and nature of substituent on the electron density of the aromatic rings. On the other hand, the energy decomposition shows that dispersion and repulsive exchange forces play an important role in the organic cation （NH4^＋）-π interaction, although the electrostatic and induction forces dominate the interaction. In addition, it is intriguing that there is an excellent correlation between the electrostatic energy and ellipticity at the bond critical point of the aromatic π systems, which would be helpful to further understand the electrostatic interaction in the cation-π complexes.

Cation-π Interaction between the Aromatic Organic Counterion and DTAB Micelle in Mixed Solvents

The cation-p interaction between the aromatic organic counterion potassium hydrogen phthalate (KHP) and DTAB micelle in aqueous mixture of EG was investigated, using the techniques of conductivity measurements, UV absorption spectrum and NMR spectrum. The conductivity and UV spectrum studies were with respect to the effect of KHP on DTAB and that of DTAB micelle on KHP, respectively. According to the chemical shift changes of the aromatic ring and the surfactant methylene protons, it can be assumed that KHP penetrated into DTAB micelle with its carboxylic group protruding out of the micellar surface. And the strength of the interaction became weaker with the content of EG in the mixed solvent increasing.

Theoretical studies on cation-π interactions (I)——Density-functional theory investigation on the configurations and interaction for ammonium cation-benzene complex

Density\|functional theory (DFT) approach of B3LYP/6\|31G\+* has been employed to calculate the six possible configurations of ammonium cation\|benzene complex (NH\++\-4\|C\-6H\-6). The calculation result released that the asymmetrical configuration of this complex with two hydrogen atoms pointing to the benzene ring was the most stable structure. Structural characteristics, molecular interaction fashion and thermodynamic parameters indicated that NH\++\-4 was bound to benzene through hydrogen bonding interaction.

阳离子-π交联吲哚基高强韧聚乙烯醇薄膜的制备与表征

针对传统聚乙烯醇材料存在的力学性能不足问题,以阳离子-π为驱动力构筑了分子链间动态交联网络。以3-异氰酸酯基-2-苯基吲哚为吲哚基载体制备了吲哚基聚乙烯醇线性聚合物(PVAI),通过添加适量的MgCl_(2)制备阳离子-π交联的吲哚基聚乙烯醇薄膜(PVAI-Mg),利用热重分析仪、差示扫描量热仪、电子万能试验机、红外光谱仪等对薄膜的结构和性能进行了表征。结果表明:当Mg^(2+)掺杂摩尔分数为吲哚基元的7.5%时,交联薄膜拉伸强度达50.97 MPa(聚乙烯醇薄膜为19.47 MPa),断裂伸长率为402.3%(聚乙烯醇薄膜为368.8%),表明Mg^(2+)与吲哚间的阳离子-π相互作用改善了薄膜的力学性能。

玉米秸秆生物炭对Cd(Ⅱ)的吸附机理研究

以玉米秸秆为原料,在350℃和700℃热解温度下分别制备了两种生物炭(BC350和BC700),并对其理化性质进行了表征。在700℃下制备的生物炭芳构化程度更高,疏水性更强,比表面积更大,孔结构发育更加完全。研究Cd(Ⅱ)在两种生物炭上的吸附发现,Two-site Langmuir吸附等温模型比One-site Langmuir吸附等温模型能更好描述Cd(Ⅱ)在生物炭表面的吸附。BC700对Cd(Ⅱ)的吸附容量大于BC350,解吸率远小于BC350,吸附效果更好;离子交换和阳离子-π作用两种吸附机理同时存在并共同作用,前者分别占BC350和BC700总吸附容量的13.7%和1.1%,后者分别占86.3%和98.9%,阳离子-π作用是最主要的吸附机理。红外光谱FTIR分析表明,生物炭表面的含氧官能团和π共轭芳香结构分别提供不同机理的吸附位点。由于具有更多的离子交换位点,BC350对Cd(Ⅱ)吸附受pH影响较BC700更大。

L-色氨酸的应用

介绍了L-色氨酸(L-Trp,w)因其特有的吲哚环结构能够作为π电子供体参与形成的cation-π复合体以及作为外源引入和内源性荧光生色团应用于蛋白质、药理研究、环境监测、食品监测等方面的应用。

阳离子-π体系相互作用的理论研究——Ⅱ.铵离子-二苯复合物体系的密度泛函研究

运用密度泛函B3LYP/6-31G~*方法对铵离子-二苯复合物体系的可能构型进行了结构优化,得到了复合物的能量最低构型为:铵离子位于两个苯环平面之间分别以两个氢原子和苯环作用,频率计算结果表明该构型为稳定结构.复合物的键长、原子净电荷、分子轨道系数、前沿轨道能量、Mullicken键级等都表明,铵氢原子和与之接近的苯环碳原子之间通过s-π相互作用而实现铵与两个苯环的结合,结合时电子从苯环向铵转移,形成电荷转移复合物.它们之间的结合方式和铵离子-苯复合物及典型氢键的结合方式相似,计算得到的热力学参数证明了这一点.复合物的红外特征振动频率位于230cm^(-1)附近,振动方式为铵平行于苯环平面来回振动.

芳香反离子与离子表面活性剂胶团的相互作用

用紫外吸收光谱的方法研究了多种芳香反离子与离子表面活性剂胶团之间的相互作用.发现阳离子表面活性剂和阴离子表面活性剂胶团对芳香反离子的吸收光谱有着显著不同的影响,芳香反离子结构的细微变化可导致光谱特性显著不同.这被解释为阳离子表面活性剂胶团与芳香环之间的阳离子-π相互作用.阳离子-π相互作用需要阳离子表面活性剂分子与芳香反离子具有合适的相对位置与距离.通过测定各混合体系的吸附量证明,不同的芳香反离子在胶团表面有不同的排列方式.NMR的实验结果支持了上述解释.