A New Cadmium(Ⅱ) Coordination Polymer Extended through Hydrogen Bonds and π-π Stacking Interactions: Synthesis and Photoluminescence Property

A new coordination polymer, {[Cd(OPY)(tdc)(HO)]·H2 O}n(OPY = 4,4?-(oxybis(4,1-phenylene))dipyridine, H2 tdc = thiophene-2,5-dicarboxylic acid), has been synthesized hydrothermally based on a V-shaped ligand OPY. The structure was fully characterized by elemental analysis, FT-IR spectroscopy, and X-ray single-crystal diffraction analysis. In1, two OPY ligands and one water molecule acted as terminal ligands coordinating to Cdcation to form [Cd(OPY)HO]units, which are then linked by tdc2-ligands to generate a one-dimensional chain. Every two adjacent chains linked by extensive O–H···O hydrogen bonds constitute one-dimensional double-chains, and such chains are extended into two-dimensional layers via O–H···N hydrogen bonds. These layers are further connected to form a three-dimensional supramolecular architecture via π-π stacking interactions. In addition, the thermal stability and solid state fluorescence property of 1 were also investigated.

Theoretical Investigations on the π-π Stacking Interactions in Phenol-Water Complexes

Non covalent interactions are quite common in all kinds of π-systems, such as π-π interactions, long range/short range van der waal force of interactions, ion-π interactions etc. Ab initio calculations are well established and account well for the experimental long range interaction energies for small clusters of aromatic molecules and most of the calculations were carried out using the MPn methods. If a reasonably large basis set is used to calculate the stacking interaction energies for a cluster (dimer, trimer etc.) of aromatic molecules then the electron-electron correlation energy may be properly calculated. Moreover, ab initio calculations for aromatic π-systems show that the calculated stacking interaction energies highly depend on the basis set used and the electron correlation energy. In this investigation, the electron correlation of the stacked hydrated phenol systems has been accounted at MP2 level of calculations. We have calculated the π-π stacking interaction energies of the hydrated phenolic systems with different conformations.

Enhanced photochemical oxidation ability of carbon nitride by π-πstacking interactions with graphene

A one-pot method for the preparation of g-C3N4/reduced graphene oxide（rGO） composite photocatalysts with controllable band structures is presented.The photocatalysts are characterized by Fouirer transform infrared spectroscopy,X-ray diffraction,scanning electron microscope,transmission electron microscope,and Mott-Schottky analysis.The valance band（VB） of g-C3N4 exhibits a noticeable positive shift upon hybridizing with rGO,and thus results in a strong photo-oxidation ability.The g-C3N4/rGO composites show a higher photodegradation activity for 2,4-dichlorophenol（2,4-DCP） and rhodamine B（RhB） under visible light irradiation（λ≥420 ran）.The g-C3N4/rGO-1sample exhibits the highest photocatalytic activity,which is 1.49 and 1.52 times higher than that of bulk g-C3N4 for 2,4-DCP and 1.52 times degradation,respectively.The enhanced photocatalytic activity for g-C3N4 originates from the improved visible light usage,enhanced electronic conductivity and photo-oxidation ability by the formed strong π-π stacking interactions with rGO.

基于mRMR-BO优化Stacking集成模型的NO_(x)浓度动态软测量

针对火电厂选择性催化还原(selective catalytic reduction,SCR)烟气脱硝系统中,由于影响入口NO_(x)质量浓度因素过多及系统大迟延大惯性,导致入口NO_(x)质量浓度难以准确及时测量的问题,提出了利用最大相关-最小冗余算法(max-relevance and min-redundancy,mRMR)结合贝叶斯优化算法(Bayesian optimization,BO)优化Stacking集成模型的SCR烟气脱硝系统入口NO_(x)质量浓度动态软测量模型。针对动态NO_(x)生成过程中静态单一模型预测精度降低及辅助变量与入口NO_(x)质量浓度时间异步的问题,利用mRMR-BO结合模型进行辅助变量筛选,Copula熵(copula entropy,CE)确定辅助变量迟延,BO结合模型确定辅助变量阶次,将TCN及LASSO利用Stacking法集成,使用含有迟延时间及阶次信息的辅助变量构建动态Stacking集成软测量模型。仿真结果显示:集成模型较TCN及LASSO单一网络的均方根误差、平均绝对误差、平均绝对百分比误差最小;动态集成模型对比静态集成模型,预测精度更高,能够实现对入口NO_(x)质量浓度的准确软测量。

A Silver Complex of 6,7-Dicyanodipyridoquinoxaline:π-Stacking Interactions and Luminescence

The reaction of 6,7-dicyanodipyridoquinoxaline （DICNQ） with AgNO3 in a 1：1 molar ratio by solution method gave a new complex [Ag（DICNQ）2]NO3 1. Single-crystal X-ray diffraction analysis reveals that the complex crystallizes in the space group Ibca of orthorhombic system with eight formula units in a cell. Crystal data for 1： a = 15.7055（17）, b = 18.411（2）, c = 20.680（2）A, V = 5979.7（11）A3, Z = 8, C32Hl2AgN13O3, Mr = 734.42, Dc = 1.632 g/cm3, μ= 0.734 mm-1, F（000） = 2928, S = 1.023 and T= 293（2） K. The final R = 0.0659 and wR = 0.1927 for 2118 observed reflections with I 〉 2σ（I）, and R = 0.0801 and wR = 0.2196 for all data. The complex builds up a packing structure by π-π stacking interactions and shows a luminescent feature.

Solvents incubatedπ-πstacking in hole transport layer for perovskite-silicon 2-terminal tandem solar cells with 27.21%efficiency

Room temperature sputtered inorganic nickel oxide(NiO_(x))is one of the most promising hole transport layers(HTL)for perovskite-sillion 2-terminal tandem solar cells with the aid of ultrathin and compact organic layers to passivate the surface defects.In this study,the aromatic solvent with different substituent groups was used to regulate the conformation of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)am ine](PTAA)layer.As a result,the single-junction perovskite solar cell(PSC)gained a power conversion efficiency(PCE)of 20.63%,contributing to a 27.21%efficiency for monolithic perovskite/silicon(double-side polished)2-terminal tandem solar cell,by applying the alkyl aromatic solvent to enhance theπ-πstacking of PTAA molecular chains.The tandem solar cell can maintain 95%initial efficiency after aging over 1000 h.This study provides a universal approach for improving the photovoltaic performance of NiO_(x)/polymer-based perovskite/silicon tandem solar cells and other single junction inverted PSCs.

Thermal Stability Improved by π–π Stacking Interactions: Synthesis, Crystal Structure and Thermal Decomposition of Sodium Nitroformate

An energetic salt, sodium nitroformate （NaNF）, was synthesized and characterized by elemental analysis, IR and UV spectra, and its crystal structure was first determined by single crystal X-ray diffraction. The structure exhibits two types of π-π stacking interactions between the nitroformate anions, i e, the parallel-displaced and T-shaped confgurafions. Furthermore, the thermal decomposition mechanism was investigated by DSC, TG-DTG and FTIR techniques. The kinetic parameters of the thermal decomposition were also calculated by using Kissinger＇s and Ozawa-Doyle＇s methods. The results show that NaNF has a good thermal stability, which is attributed to the π-π stacking interactions.

THE INTRAMOLECULAR AROMATIC-RING STACKING INTERACTION OF MIXED LIGAND PALLADIUM(Ⅱ)COMPLEXES Ⅲ.STUDIES ON THE Pd^(2+)-A-UTP^(4-)SYSTEMS BY HNMR

The intramolecular aromatic-ring stacking interaction of mixed- ligand complex Pd(A)(UTP)^(2-)in the system pd^(2+)-A-UTP^(4-)has been determined by ~1HNMR,where A=1,10-phenanthroline(phen),2,2'-bipyridyl(bpy)and DL- tryptophan(trp^-);UTP^(4-)=uridine 5-triphosphate.The result indicates that it is the partial stacking between the uracil ring of UTP^(4-)and the heterocyclic ring of A that makes H(5),H(6)and H(1')in the UTP^(4-)shift upfield signifi- cantly.Accordingly,the order of aromatic-ring interaction in the mixed- ligand complex has been obtained as follows:Pd(phen)(UTP)^(2-)(?)Pd(bpy)(UTP)^(2-) Pd(trp)(UTP)^(3-).

Pi Stacking Interactions in Two TPT Derivatives and Their Photoluminescence Characters

π-π Stacking in the 2,4,6-tris（4-pyridyl）-1,3,5-triazine aromatic nitrogen-containing ligand and its metal-ligand complex Zn（TPT）2（H2O）4（OH）2 1 has been investigated by single-crystal X-ray diffraction analyses. The stacking mode of the ligand changes from the offset conformation to a perfect face-to-face alignment with the coordination to the zinc centers. The structure features are correlated with their solid-state luminescence properties. With excitation at 360 nm, free TPT ligand gives a strong fluorescent emission at 455 nm and the ligand-centered emission of the metal-ligand complex occurs at the same wavelength with lower emission intensity. The distance between the aromatic rings responds to the difference of luminescence characters.

Self-aggregating behavior of poly(4-vinyl pyridine)and the potential in mitigating sand production based onπ-πstacking interaction

Unconsolidated sandstone reservoirs are most susceptible to sand production that leads to a dramatic oil production decline.In this study,the poly(4-vinyl pyridine)(P_(4)VP)incorporated with self-aggregating behavior was proposed for sand migration control.The P_(4)VP could aggregate sand grains spontaneously throughπ-πstacking interactions to withstand the drag forces sufficiently.The influential factors on the self-aggregating behavior of the P_(4)VP were evaluated by adhesion force test.The adsorption as well as desorption behavior of P_(4)VP on sand grains was characterized by scanning electron microscopy and adhesion force test at different pH conditions.The result indicated that the pH altered the forms of surface silanol groups on sand grains,which in turn affected the adsorption process of P_(4)VP.The spontaneous dimerization of P_(4)VP molecules resulting from theπ-πstacking interaction was demonstrated by reduced density gradient analysis,which contributed to the self-aggregating behavior and the thermally reversible characteristic of the P_(4)VP.Dynamic sand stabilization test revealed that the P_(4)VP showed wide pH and temperature ranges of application.The production of sands can be mitigated effectively at 20-130℃ within the pH range of 4-8.

STUDY ON THE STABILITY AND STACKING INTERACTION EFFECT OF THE TERNARY M(Ⅱ)(ATP)AND PYRIDINE-LIKE LIGANDS

The stabilities of the complexes of three pyridine-like ligands with M(II)(ATP)^(2-) and M(II)(M=Ni,Co)were studied by spectrophotometry and by comparing the stability constants of the ternary complexes with these of the binary complexes.A stacking interaction between the pyridine ring and the purine ring of ATP is indicated.The general existence of the stacking interaction encourages us to interpret the antitumor mechanism of a new class of antitumor drugs.

Quantum Mechanical Study on the π-π Stacking Interaction and Change in Conformation of Phenolic Systems with Different Intermolecular Rotations

Aromatic systems like phenol, diphenol, cyano benzene, chloro benzene, aniline etc shows effective π-π stacking interactions, long range van der Waals forces;ion-π interactions etc. and these forces of interactions play an crucial role in the stability of stacked π-dimeric system. On the other hand, substituents and conformational change in the stacked dimmers of aromatic system may also change the stability of different stacked dimers. In this current study, stacked phenolic dimmers (both phenol and diphenol) have been taken for investigation of the stacking π-π interaction. But, the stacking interactions are also greatly affected by the conformational change with internal rotation (i.e. dihedral angle, φ) between the stacked dimers. It is generally accepted that larger basis sets are required for the highly accurate calculation of interaction energies for any stacked aromatic models. But, it has recently been reported that M062X/6-311++G(d,p) basis set is effectively better than that of B3LYP/6-311++G(d,p) for determining the interaction energies for any kind of long range interaction in aromatic systems. Therefore, all the calculations were carried out by using M062X/6-311++G(d,p) basis set. However, in most of the cases the calculated π-π stacking interaction energies show almost same result for both DFT and ab initio methods.

Unusual F_(3)stacking fault in magnesium

An unusual F_(3)basal stacking fault resulting from twin-dislocation interaction in magnesium is observed in molecular dynamics simulation.The F_(3)fault is produced in the twin lattice from the interaction between a migrating(1012)twin boundary and a partial dislocation of either a prismatic<c>edge,or a prismatic<c+a>mixed dislocation in the matrix.The condition is that the partial dislocation needs to have a negative sign and lie on a plane intersecting a compression site of the twin boundary.The F_(3)fault can also be generated when a positive basal<a>mixed dislocation in the twin lattice,with slip plane intersecting a compression site of the twin boundary,interacts with a basal-prismatic twinning disconnection.The F_(3)fault comprises two I_(1) faults that have the same character but are separated by two basal layers.It has one end connected to the twin boundary,and the other end bounded by a lattice defect with a Burgers vector identical to that of a 30°Shockley partial dislocation.The formation frequency of the F_(3)fault is higher at a lower shear stress(below∼400 MPa)and/or a lower temperature(100 K and 200 K).The F_(3)fault can decompose into a glissile 30°Shockley and a T_(2) fault at a temperature above∼400 K.The relationships between the F_(3)fault and other types of basal stacking faults such as I_(2),T_(2) or paired I_(1) faults that are separated by multiple basal layers are discussed.

Studies on Intramolecular Stacking Interaction of Ternary Complexes M（Ⅱ）（ATP）￣（2－） with Heteroaromatic N－Base Ligands

o understand the driving forces leading to mixed-ligand complexes in biologi-cal systenis.ternary complexes of M (ATP(L￣(2-) type, where M = Cu￣(2+), Ni￣(2+) orCo￣(2+) , and L= pyridine(Py) , 4-picoline, 3, 5-lutidine, isoquinoline (lq) or benzimi-dazole(Bi) in aqueous solution were studied by spectropliotometry, some of them(M=Cu￣(2+), L = isoquinoline or benzimidazole) were also separately studied hy po-tentiometric pH titration. The results show that an intramolecular stacking interac-tion exists between the heteroaromatic ring of the ligands and the purine moiety ofATP.

π-π Stacking, Hydrogen Bonding and Magnetic Coupling Mechanism on a Mono-nuclear Cu^Ⅱ Complex

A new mono-nuclear CuII complex [Cu（DPP）（DP）Br]（ClO4）H2O （DPP = 2-（3,5- dimethyl-1H-pyrazol-1-yl）-1,10-phenanthroline, DP = 3,5-dimethyl-1H-pyrazole） has been syn- thesized with 2-（3,5-dimethyl-1H-pyrazol-1-yl）-1,10-phenanthroline and 3,5-dimethyl-1H-pyrazole as ligands, and its crystal structure was determined by X-ray crystallography. The crystal is of monoclinic system, space group P21/c with a = 13.765（2）, b = 17.044（3）, c = 10.9044（16）, β= 97.112（2）°, V = 2538.5（6）3, Z = 4, C22H24BrClCuN6O5, Mr = 631.37, Dc = 1.652 g/cm3, F（000） = 1276 and μ= 2.585 mm-1. In the crystal, DPP functions as a tridentate ligand and CuII ions assume a distorted square pyramidal geometry with Br atom lying on the apex, and at the same time, there is π-π stacking between adjacent complexes, which deals with two 1,10-phenanthroline plane rings. In addition to the π-π stacking, there are C-H···Br non-classic hydrogen bonds between adjacent complexes. The theoretical calculations reveal that the π-π stacking and C-H···Br non-classic hydrogen bond result in a weak anti-ferromagnetic interaction with 2J = -5.34 cm-1 and a weak ferromagnetic 2J = 5.92 cm-1, respectively. The magnetic coupling sign from the π-π stacking could be explained with McConnell I spin-polarization mechanism.

Dinuclear Silver(Ⅰ) Complex Based on 1-Picolyl-3-propylbenzimidazolium Salt: Crystal Structure and Weak Interactions

1-Picolyl-3-propylbenzimidazolium bromide （LBr） was prepared from benzimida- zole by alkylation with 2-chloromethyl-pyridine in the presence of NaH, followed by quaternization with 1-bromopropane. Ligand LBr was treated with AgBr in CH2Cl2 to afford a dinuclear silver（I） complex L2Ag2Br4 （1）. In complex 1, a 2-D supramolecular layer is formed through two types of π-π stacking interactions. Fluorescent emission spectra of ligand LBr and complex 1 are described.

Influence of non-covalent interactions on properties of lanthanide systems with aromatic ligands

Two series of lanthanide compounds, namely, chlorides containing different numbers of both 1,10-phenanthroline （Phen） molecules and chloride anions in the first coordination sphere, and Schiff Bases （SBs） derived from Pyridoxal （PL） and amino acids, were characterized by single crystal X-ray diffraction and luminescence techniques. The combined use of these techniques for the analysis of long-distance europium non-covalent interactions was performed for the first time. As a result, the correlation between supramolecular organization and the features of the Eum electronic transitions was found for the compounds of the first series. Strong non-covalent interactions between pyridoxal tings of SBs （the second series of compotmd） led to the formation of 1：2 species and four-dentate coordination function of these SBs in aqueous solution.

Unveiling chain–chain interactions in CO2-based crystalline stereocomplexed polycarbonates by solid-state NMR spectroscopy and DFT calculations

CO2-based stereocomplexed polycarbonates derived from the intermolecularly interlocked interaction between the enantiopure polymers with the opposite configuration exhibit high crystallinity, excellent thermal and mechanical stabilities. Deep insights into the mechanism of stereocomplexation are of particular importance to the design and manufacture of new promising and sustainable polycarbonates with enhanced physicochemical properties. Our solid-state NMR experiments linking with DFT computations clearly reveal the specific chain-chain interactions in a typical stereocomplexed poly（4,4-dimethyl-3,5,8-trioxabicyclo[5.1.0] octane carbonate）（PCXC）.13C CP/MAS NMR,1H DUMBO MAS NMR and 13C/1H relaxation-time measurements indicate that the formation of stereocomplex reduces the local mobilities of carbonyl, methine and methylene groups in each chain of PCXC significantly. Through a combination of two-dimensional 1H-13C HETCOR NMR and DFT calculation analysis, the cis-/trans-conformations and packing models of PCXC chains in the amorphous, enantionpure isotactic and stereocomplexed polycarbonates are identified. The splitting of 13C and 1H NMR chemical shifts of methine groups in the backbone carbon region demonstrates the ordered interlock interactions between the R-and S-chain in the stereocomplexed PCXC.

Hybrid HMX multi-level assembled under the constraint of 2D materials with efficiently reduced sensitivity and optimized thermal stability

The interfacial interaction between HMX molecules and coating materials is the key to the safety performance of explosives and has received extensive attention.However,screening suitable coating agents to enhance the interfacial effect to obtain high-energy and low-sensitivity explosives has long been a major challenge.In this work,HMX-PEI/rGO/g-C_(3)N_(4)(HPrGC)composites were innovatively prepared by a multi-level coating strategy of two-dimensional graphite rGO and g-C_(3)N_(4).The g-C_(3)N_(4) used for desensitization has a richπ-conjugated system and shows outstanding ability in reducing friction sensitivity.The hierarchical structure of HPrGC formed by electrostatic self-assembly andπ-πstacking can effectively dissipate energy accumulation under heat and mechanical stimulation through structural evolution,thus exhibiting a prominent synergistic desensitization effect on HMX.The results show that rGO/gC_(3)N_(4) coating has no effect on the crystal structure and chemical structure of HMX.More importantly,the perfect combination of g-C_(3)N_(4) and rGO endows HPrGC with enhanced thermal stability and ideal mechanical sensitivity(IS:21 J,FS:216 N).Obviously,the new fabrication of HPrGC enriches the variety of desensitizer materials and helps to deepen the understanding of the interaction between explosives and coatings.