Atomic tracking of thermally-driven structural evolution in 2D crystals:Case of NbSe_(2)

Advanced atomic tracking techniques play a critical role in characterizing structural evolution,elucidating fundamental mechanisms of exotic phenomena and tailoring delicate properties.Thermally driven structural modulation in 2D crystals,such as the charge density wave(CDW),often leads to intriguing quantum properties,making them a valuable platform for exploring fundamental physics and potential device applications.However,despite their significance,experimental studies addressing atomic tracking of thermally-driven structural evolution in 2D crystals have been limited.Herein,we utilize high-accuracy variable-temperature atomic tracking measurements with scanning tunneling microscopy(STM)to directly observe a series of structural transitions in a model 2D crystal,namely NbSe_(2).With the atomic tracking technique,we confirm the existence of the universal thermally-driven CDW transition hysteresis between the heating and cooling cycles.This transition hysteresis,characterized by a constant temperature offset,represents a new phenomenon of structural evolution.Our findings provide a feasible method to track CDW transitions at the atomic scale in 2D crystals,significantly contributing to a better understanding and the potential modulation of these materials'functions in nanodevices.

A 2D Layered Thiostannate: Synthesis and Crystal Structure of [tmdpH_2]Sn_3S_7

A new thiostannate,[tmdpH2]Sn3S7 1（tmdp = 4,4＇-trimethylenedipiperidine）,has been synthesized under solvothermal conditions and characterized by elemental analysis,IR spectroscopy,and single-crystal X-ray diffraction analysis.In 1,the Sn3S4 secondary incomplete cubane-like building units are bridged by μ2-S atoms to form Sn12S12 rings which are then joined parallelly to the [001] plane,giving the final 2D（Sn3S7^2-）n layer of（6,3） network.The layers are stacked along the c axis so that 24-membered ring channels are generated,in which the organic cations are accommodated.The compound crystallizes in monoclinic,space group C2/c,with a=23.052（3）,b=13.4039（12）,c=18.412（2）A,β=120.112（4）°,V=4921.3（9）A^3,C13H28N2S7Sn3,Mr=792.86,Z=8,Dc=2.140 g/cm^3,F（000）=3056,μ=3.619 mm^-1,the final R=0.0488 and wR=0.1125 for 4607 observed reflections with I〉2σ（I）.

Synthesis and Crystal Structure of a Distorted 2D (6,3) Layer Complex, [Cd(H_2mbdpz)(N_3)_2]_n (H_2mbdpz = 4,4'-Methylenebis(3,5-dimethylpyrazole)) Containing both End-on and End-to-end Azide Bridges

The complex [Cd（H2mbdpz）（N3）2]n 1 （H2mbdpz = 4,4′-methylenebis（3,5-dimethylpyrazole）） has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis. It crystallizes in the monoclinic system, space groups C2/c with a = 22.154（5）, b = 7.4835（15）, c = 21.044（8）A^°,β= 115.51（3）°, V= 3148.7（17）A^°3, Z= 8, C11H16CdN10, Mr = 400.75, Dc = 1.691 g/cm^3,μ = 1.401 mm^-1, F（000） = 1599, T= 293（2） K, the final R = 0.0228 and wR = 0.0581 for 3604 observed reflections with I 〉 2σ（I）. The structural determination revealed that the coordination environment of Cd（Ⅱ） atom is a distorted octahedron consisting of two nitrogen donors of two H2mbdpz ligands and four nitrogen donors from four azide ligands. The azide moieties act as bridges in two modes： end-on （μ1,1-） and end-to-end （μ1,3-）, and H2mbdpz also serves as a bridge with a bis-monodentate coordination. Both bridging ligands link the Cd（Ⅱ） atoms to form a distorted two-dimensional （6,3） layer.

1,3-双(偶氮介晶基)-1,1,3,3-四甲基二硅氧烷的 合成、2D NMR结构分析和液晶性能

合成了2个(CH3(C6H4)N2(C6H3A)COO(C6H4)OCH2-Si(CH3)2)2O化合物,其中A = H为1,A = CH3为2。经IR、1H NMR和元素分析表征,并用2D NMR1H-1H COSY记录了2个化合物中不同取代基苯环上所有质子的化学位移和相关-自旋偶合常数,对谱线的归属作了指认。通过偏光显微镜和DSC分析,1具有液晶性能,而2没有液晶性能。同时,用AM1方法计算了它们的电子结构,讨论了它们的结构与性能之间的关系。

具有2D氢键网络结构的锰化合物[Mn(BBP-H)_2]的水热合成(英文)

利用水热合成方法,得到了一个新型的锰配合物[Mn(BBP-H)2](BBP为2,6-双(2-苯并咪唑甲基)吡啶),并通过X-射线衍射得到其晶体结构,空间群为P-4n2,晶胞参数a=1.01470(17)nm,b=1.01470(17)nm,c=1.5885(5)nm,V=1.6355(7)nm3,Z=2.每个锰离子与两个带电荷的三齿配体BBP配位,形成畸变的八面体构型,相邻的分子之间通过氢键形成2D平面结构.

(H_2dap)_6H[V_(12)B_(16)O_(54)(OH)_4]·12H_2O(dap=1,2-diaminopropane)的水热合成、结构及谱学研究

采用水热合成法合成了一种结构新颖的多硼钒氧簇化合物(H2dap)6H[V12B16O54(OH)4]·12H2O(dap=1,2-diaminopropane),对化合物1进行了单晶X射线衍射,结果表明化合物1属于单斜晶系,C2/c空间群,晶胞参数a=19.027(4),b=16.142(3),c=26.679(5),α=90°,β=101.06(3)°,γ=90°,V=8 042(3)nm3,Z=4,Dc=1.962g·cm-3,μ=1.456mm-1,F(000)=4 776,7 635个可观察独立衍射点射点[I>2σ(I)],最后结构精修到偏离因子R1=0.0626,wR2=0.192 7,S=1.003。该化合物的结构主要由V12B16簇单元和作为抗衡离子的1,2-丙二胺组成,且簇单元之间通过强氢键N—H…O和弱氢键C—H…O的作用连接成了二维的层状结构,层与层之间也是通过氢键的作用连接成了三维的超分子结构。此外,对化合物1进行了红外光谱、磁微扰下的二维红外相关光谱、热微扰下的二维红外相关光谱以及紫外-可见固体漫反射光谱分析的表征,探讨了化合物1的结构与谱学性质的关系。红外光谱表明νas(V—Oμ)反对称伸缩振动吸收峰和νs(V—Oμ)对称伸缩振动吸收峰分别出现在775和683cm-1,而BO3中的ν(B—O)键的振动吸收峰以及BO4四面体中的δ(B—O)的振动吸收峰分别出现在1 350和1 050cm-1,磁微扰的二维红外相关光谱表明B—O和V—O—V的伸缩振动对于磁场的变化具有敏感的响应峰,热微扰的二维红外相关光谱表明B—OH,B—O和V—O—V的伸缩振动时热微扰具有敏感的响应峰。

Hydrothermal Synthesis, Crystal Structure and Thermal Analyses of Pyrazine-2,3-dicarboxylic Acid Bridged Co(II) Coordination Polymer of _∞~2[Co(phen)(μ-L)_(3/3)]·H_2O (H_2L = Pyrazine-2,3-dicarboxylic Acid)

A novel pyrazine-2,3-dicarboxylic acid bridged Co(II) phen complex 2 ∞ [Co- (phen)(μ-L)3/3]?H2O (H2L = pyrazine-2,3-dicarboxylic acid) has been hydrothermally synthesized, and X-ray single-crystal diffraction analysis shows that it crystallizes in the monoclinic system, space group P21/n with a = 11.480(2), b = 11.885(2), c = 12.939(3) ?, β = 110.55(3)°, V = 1653.1(6) ?3, Mr = 423.25, Dc = 0.425 g/cm3, Z = 4, R = 0.0361 and wR = 0.1011. The title complex consists of 2D 2 ∞ [Co(phen)(μ-L)3/3] layers and crystal water molecules. Each Co atom is octahedrally coordinated by three N atoms and three O atoms to form 2D 2 ∞ [Co(phen)(μ-L)3/3] polymeric layers. Furthermore, such 2D layers are stacked into 3D supramolecular frameworks via Van der Waals’ intermolecular forces, strong and weak hydrogen-bond interactions. The coordination phen and crystal water molecules are resided into cavities of the frameworks.

Hetero-bimetallic Complex of a 2D Coordination Network Constructed by Sodium Ion and p-Sulfonatothiacalix[4]arene

A 2D coordination polymer built by sodium ion and water-soluble p-sulfonatothiacalix[4]arene of trivalent yttrium complex [Na（H2O）2Y（H2O）6（DMF） （p-sulfonatothiaca lix[4]arene）]-9H2O is reported. The complex belongs to the monoclinic system, space group P2 1/c, with a = 16.703（3）, b = 17.819（4）, c = 17.357（4）A, β = 106.23（3）°, Z = 4, V = 4960.0（17）A^3, Mr = 1304.08, Dc = 1.746 g/cm^3,μ= 1.624 mm^-1, F（000） = 2688, the final R = 0.0398 and wR = 0.1132 for 7534 observed reflections with I 〉 2σ（I）. One yttrium（Ⅲ） ion is coordinated by the thiacalixarene ligand via the sulfonato group, and also ligated by an oxygen atom of a DMF molecule occupying the cavity of thiacalixarene and six aqua ligands.

Syntheses,Crystal Structures and Intermolecular Interactions of Cu(Ⅱ) Complexes with Methyl- benzoic Acid(MBA) and 1,10-Phenanthroline

Two cupric complexes containing methylbenzoic acid have been prepared and crystallized by solvent evaporation method in DMF. The single-crystal X-ray crystallographic analysis reveals that they are dicaryon complexes. Complex I with formula of [Cu2（m- MBA）4DMF2] crystallizes in monoclinic with space group of P21/c and complex 2 with formula of [Cuz（o-MBA）ffo-phen）2]·NO3·H2O crystallizes in triclinic with space group of P I. The weak interactions including C-H...O hydrogen bonds, C-H…π interactions and π-π stacking in the structures of two complexes are observed from the X-ray crystallographic data. In addition, there are still classical hydrogen bonds in 2. The different strength of intermolecular interaction in the structure is reflected on their different thermal stability measured by thermal gravimetric analysis and 2D-1R correlation spectroscopy of two complexes. The study of weak interactions is meaningful to provide supporting data for supramolecular chemistry theory and potential applications in molecular biology.

A Novel 2D Architecture from Bismuth and Flexible Ligand N,N'-Diacetic Acid Imidazolium Chloride

A new compound {[Bi（trans-DAM）（cis-DAM）（H2O）]NO3·H2O}n 1 derived from bismuth and the flexible ligand N,N＇-diacetic acid imidazolium chloride （H2DAMCl） was obtained by hydrothermal synthesis and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic P21/c space group with a = 9.2298（18）, b = 13.339（3）, c = 17.090（3） , β = 105.38（2）°, V = 2028.7（7）A^3, Z = 4, C14H18N5O13Bi, Mr = 673.31, Dc = 2.204 g/cm^3, F（000） = 1296, μ = 8.772 mm-1, the final R = 0.0472 and wR = 0.1441 for 4129 observed reflections （I 〉 2σ（I））. In 1, the carboxylic groups from DAM- ligands adopt a cheating mode to link bismuth ions to form a 2D sheet network. These sheets are further connected by hydrogen bonding interactions to give an interesting 3D supramolecular framework. 2D correlation analysis of IR of 1 with thermal and magnetic perturbation was introduced to ascertain the characteristic adsorption of the groups overlapped in the 1D IR spectrum. Additionally, compound 1 exhibits fluorescent emission at room temperature.

新型二维晶体MXene的研究进展

MXene是一种新型的二维过渡金属碳化物或碳氮化物,化学式为Mn+1Xn,M代表过渡金属,X代表碳或者氮,n=1、2、3。目前制备的MXene表面均附有官能团,因此也常用Mn+1XnTx来表示其化学式。研究发现,MXene具有良好的导电性、透光性、磁性、低温热电性和能量存储等诸多新颖的性能。本文通过总结MXene结构和性能等方面最新的实验和理论研究成果,分析了该体系目前存在的问题,预测了其可能的应用领域和未来的发展方向。

光子晶体制备及其应用研究进展

综述了光子晶体的特性以及制备方法,分别介绍了光子晶体在光子晶体光纤、光子晶体滤波器、低阈值激光器、光子晶体结构色等领域的应用研究现状,展示了光子晶体器件的巨大发展潜力,并指出了光子晶体今后的研究方向。同时笔者认为将3D打印技术与光子晶体器件的制备相结合,对早日实现光子晶体器件的实际应用意义重大。

结构和缺陷对二维光子晶体传输性质的影响

用转移矩阵方法计算了二维光子晶体的传输性质 ,讨论了不同极化光的透射行为 ,比较了正方点阵、有心正方点阵、含缺陷有心正方点阵光子能带对透射特性的影响 ,获得了第一禁带特性与光子晶体结构的一些基本关系 .

ADP晶体{100}面族二维成核生长微观形貌的AFM研究

ADP晶体{100}面族微观形貌的非实时AFM（atomic force microscopy，AFM）成像表明，过饱和度σ=0．053时，晶面上出现二维成核生长；随σ增加至0．11，二维岛数量急剧增加，尺寸减小，分布渐趋均匀，二维成核生长逐渐增强，界面呈现出由光滑向粗糙转变的特征；各二维岛形状趋近于长条形，表现出各向异性，长轴平行于[001]晶向；二维岛上有单分子高度的台阶和台阶聚并后高度为2～3nm的大台阶；二维岛间融合时取向相同；σ=0．053时，融合后所形成的较大二维岛的生长呈现出周边快中心慢的情况，将可能导致产生晶体缺陷。

二维X射线衍射及其应用研究进展

介绍了三维、一维和二维X射线衍射的有关概念,给出二维X射线衍射的定义:在X射线衍射实验中使用二维探测器,并对由二维探测器记录的二维象、二维衍射花样的数据进行处理分析和解释的X射线衍射方法称为二维X射线衍射术。之后,分四部分综述二维X射线衍射(2D-XRD)和散射及其应用的进展。1)单晶样品的二维衍射包括经典的劳厄法定向和用二维探测器(带衰减底片组件、CCD和IP等)的劳厄法测定晶体结构的单晶样品现代二维衍射术;2)随后,评述多晶样品二维衍射的衍射几何、实验装置,以及在物相鉴定、应力测定和织构测定方面应用的方法和基本公式;3)二维小角散射(2D-SAXS)也作了简介。4)把一维和二维衍射术作了较全面的比较和综合评论。

[Co(pema)(amp)Cl]^(2+)体系一面式异构体的结构解析及其优势构型

仅合成得到 [Co(pema) (amp)Cl] 2 + 体系配合物的一个面式异构体 (pema =N ( 2 吡啶甲基 )乙二胺 ,amp =2 甲氨基吡啶 ) .利用二维核磁共振技术与单晶X ray衍射法平行解析了该异构体的结构 .结果显示结构中存在C—H…π相互作用 .用RHF/LANL2DZ对该体系可能的异构体进行结构、能量优化 ,可能形成C—H…π相互作用的异构体具有较好的稳定性 .C—H…π相互作用对含吡啶环的 [CoN5Cl] 2 + 系配合物的异构体的选择性形成及其稳定性具有重要作用 .

液晶-金属光子晶体波导的光学特性

运用时域有限差分方法分析了二维液晶-金属光子晶体波导的光学特性。二维正方晶格金属光子晶体波导位于两个电极之间,其背景介质为液晶。通过在电极上施加不同电压,电场诱导液晶取向以改变液晶的折射指数从而改变光子晶体的带隙结构。数值计算结果表明:通过外界电场控制所填充的向列相液晶的方向可以对这种金属光子晶体波导的光学特性进行调节,该波导可用于制作光子晶体光开关等光学器件。

点缺陷二维光子晶体波导的出射光集束

光子晶体器件在高密度集成光通信中有广泛的应用,为解决光子晶体波导出射光场的空间控制,采用时域有限差分法分析光子晶体波导结构的缺陷传播特性,提出基于点缺陷优化波导结构,通过在波导出射口两侧加上点缺陷,出射光方向性有显著提高,实现三点光源干涉系统的光集束。模拟结果表明缺陷态越靠近能带结构中央,共振腔的耦合效率越高;相反,缺陷态越靠近能带结构边缘位置,则共振腔耦合效率越低,因此,选取禁带区域四分之一处对应的点缺陷,可以有效实现波导出射的光集束。

[Co(N-(2-Aminoethyl)-1,3-propanediamine)(1,2-diamino-2-methylpropane)Cl][ZnCl_(4)]配合物部分异构体的结构解析

利用过氧化物合成分解法制备得到一新的 [Co(N-(2-Aminoethyl)-1,3 propanediamine)(1,2-diamino-2-methylpropane)Cl]^(2＋)体系配合物，并用柱层析分离得到部分几何异构体。用单晶 X-射线衍射分析方法解析了其中一反式（三元胺仲氮上的氢相对于 Cl）经式异构体的晶体结构，用二维核磁共振技术的同核质子相关 gCOSY及 NOESY谱解析了其中一顺式（三元胺仲氮上的氢相对于 Cl）经式异构体在溶液中的结构。

阿糖胞苷HepDirect前药MB07133的波谱特征与晶体结构

用1H和13C NMR和多种2D NMR谱表征了阿糖胞苷的磷酸盐或磷酸酯肝靶向前体药物(Hep Direct前药)——MB07133的结构,对其NMR谱进行了归属;用X-射线单晶衍射测定了单晶的晶体结构.讨论了该化合物的波谱数据和晶体结构数据,验证了其结构的正确性并探讨了其化学结构对药物特性的影响.