磁几何阻挫材料羟基氯化钴的中红外光谱特征

使用3种光谱仪测量了磁几何阻挫材料羟基氯化钴Co₂(OH)₃Cl的中红外(4000—400 cm^-1)吸收光谱,筛选出确信为Co₂(OH)₃Cl的本征吸收峰数据,结合已知的晶体结构参数,指认了官能团和指纹区相应谱峰的来源.在指认中着重探讨了羟基伸缩振动基频模vOH的具体实验数据,根据固体中氢键的特点,以Co₃—O平均距离为基准,推算了本样品关键词：红外光谱几何阻挫羟基氯化钴三聚氢键     

On difference of properties between organic fluorine hydrogen bond C–H···F–C and conventional hydrogen bond

The existence of C–H···F–C hydrogen bonds in the complexes of trifluoromethane and cyclic molecule (oxirane, cyclobutanone, dioxane, and pyridine) has been experimentally proven by Caminati and co-workers. This study presents a theoretical investigation on these C–H···F–C hydrogen bonds at B97D/6-311++G^** and MP2/6-311++G^** levels, in terms of C–H vibrational frequency shifts, atoms in molecules characteristics, and the bonding feature of C–H···F–C hydrogen bonds. It is found that in three important aspects, there are significant differences in properties between C–H···F–C and conventional hydrogen bonds. The C–H···F–C hydrogen bonds show a blueshift in the C–H vibrational frequencies, instead of the X–H normal redshift in X–H···Y conventional hydrogen bonds. The natural bond orbital (NBO) analyses show that σ and p types of lone pair orbitals of the F atom to an antibonding σ^*_H–C orbital form a dual C–H···F–C hydrogen bond. Such a dual hydrogen bonding leads to the proton acceptor directionality of the C–H···F–C hydrogen bond softer. Our studies also show that the Laplacian of the electron density (▽²ρ_BCP) is not always a good criterion for hydrogen bonds. Therefore, we should not recommend the use of the Laplacian of the electron density as a criterion for C–H···F–C hydrogen bonds.     

Cooperative effects of hydrogen,halogen and beryllium bonds on model halogen-bonded FCl … YZ (YZ = BF,CO, N2) complexes in FX′ … FCl … YZ trimers (FX′ = FH,FCl, F2Be)

A computational study of model halogen-bonded FCl?…?YZ dimers and FX′?…?FCl?…?YZ (FX′ = FH, FCl, F₂Be; YZ = BF, CO, N₂) trimers was undertaken at the MP2/6-311++G (2d, 2p) level of theory. Three different trimer arrangements are possible and the cooperative effect of hydrogen-, halogen- and beryllium-bonding in each of these trimers was assessed relative to the FCl?…?YZ dimer. It was found that the beryllium bond has the largest cooperative effect, while the halogen bond has the smallest, with the hydrogen bond being intermediate between the other two interactions. Interesting trends in selected properties were identified and discussed.     

量子自旋液体的实验研究进展

量子自旋液体是指由于其中存在的强量子涨落导致自旋即使在零温极限下也不形成磁有序的一种新的自旋量子态。区别于传统的磁有序材料,它的基态没有确定的序参量来表示,并且不伴随任何自发的对称性破缺,超越了朗道相变理论所能描述的物相范畴,代表了一种新奇的量子物态,具有非常高的理论研究价值。这一全新的物态被认为与非常规超导机制之间有着十分紧密的关系。同时在未来的量子计算方面有着非常诱人的应用前景,因此一直以来备受关注。虽然量子自旋液体理论经过近半个世纪的积淀有了长足的发展,但是由于候选材料稀少,实验测量条件苛刻等多种因素制约,导致实验方面的进展相对缓慢。近年来各项实验技术的进步和成熟为量子自旋液体候选材料的测量表征提供了有利条件,加快了实验工作的推进速度。本文将从实验的角度介绍 (1) 几何阻挫量子自旋液体候选材料,包括三角晶格化合物 YbMgGaO量子自旋液体是指由于其中存在的强量子涨落导致自旋即使在零温极限下也不形成磁有序的一种新的自旋量子态。区别于传统的磁有序材料,它的基态没有确定的序参量来表示,并且不伴随任何自发的对称性破缺,超越了朗道相变理论所能描述的物相范畴,代表了一种新奇的量子物态,具有非常高的理论研究价值。这一全新的物态被认为与非常规超导机制之间有着十分紧密的关系。同时在未来的量子计算方面有着非常诱人的应用前景,因此一直以来备受关注。虽然量子自旋液体理论经过近半个世纪的积淀有了长足的发展,但是由于候选材料稀少,实验测量条件苛刻等多种因素制约,导致实验方面的进展相对缓慢。近年来各项实验技术的进步和成熟为量子自旋液体候选材料的测量表征提供了有利条件,加快了实验工作的推进速度。本文将从实验的角度介绍(1)几何阻挫量子自旋液体候选材料,包括三角晶格化合物YbMgGaO_4和YbZnGaO_4、κ-(BEDT-TTF)_2Cu_2(CN)_3、EtMe_3Sb[Pd(dmit)_2]_2和kagome格子化合物ZnCu_3(OH)_6Cl_2;(2)Kitaev量子自旋液体候选材料铱氧化物(Na_2IrO_3与α-,β-,γ-Li_2IrO_3)和α-RuCl_3。文章将着重介绍近年来在量子自旋液体实验方面的进展,之后做一个简单的总结,最后对量子自旋液体的未来发展做一个展望。     

铵水间质子交换的再研究:不受扩散约束的化学交换

对铵盐水溶液中铵离子与水分子间的质子交换进行了再研究. 以核磁共振(NMR) 波谱学方法测定了不同pH值, 不同温度和含不同共存盐浓度的氯化铵水溶液中质子交换速率, 组分自扩散系数及NMR自旋晶格弛豫时间. 结果显示铵水间的质子交换并不受交换主体分子或离子自扩散的约束. 交换机理包括化学键和氢键的交换. 在溶液中, 水分子以氢键为桥 梁连接铵和其因水解而产生的碱性部分--氨. 在氢交换的过程中, 氨从水分子接受一个氢 成为铵, 同时另外一端的铵提供一个氢给水分子而变成氨, 或者一个氢从水分子转移到氨而同 时另外一个氢从铵转移到水. 在铵水质子交换的过程中没有净的电荷转移. 在低pH条件下, 由水解产生的氨的浓度降低, 亦即铵-水-氨复合物减少, 结果氢交换的可能性降低. 这解释了生物氢交换体系中的一种常见的在低pH值条件下氢交换变慢的现象.     

A Carbon-13 NMR Assignment Study of Certain 6-Substituted Dibenz [c,e] Azepine 5, 7-Dione

The natural abundance carbon-13 nuclear magnetic resonance spectra of diphenic acid and some 6-substituted dibenz [c,e] azepine, 5, 7-dione - which can be considered also as N-substituted diphenimide - were recorded using Fourier transform technique. The chemical shifts of various carbon resonance have been assigned on the basis of chemical shift theory, the signal multiplicity observed in the single frequency off-resonance decoupled (SFORD) spectra and comparison with the chemical shifts of the model compounds.     

Why the ΔνCH blue shift is larger in chloral than in dichloroacetyl chloride dimers?

Raman spectra of the Cl₃CCHO/CCl₄ and Cl₃CCHO/C₆D₁₂ binary systems were recorded as a function of the mole fraction. Features originating from self‐aggregates of chloral (trichloroethanal, trichloroacetaldehyde—TCAA) molecules were detected in different spectral regions. The most pronounced changes were observed in the vicinity of the ν(CO) and ν(C H) stretching vibration bands. Using two‐dimensional correlation spectroscopy (2D‐COS), evolving‐factor analysis (EFA) and multivariate curve resolution (MCR), dimer bands were identified, and their positions were determined. The ν(C H) stretching vibration band in dimers was blue‐shifted by nearly 18 cm⁻¹, whereas the ν(CO) dimer band was red‐shifted by more than 5 cm⁻¹. For these bands, the observed shifts were accompanied by an almost twofold change in the bandwidth, from approximately 19 and 6 cm⁻¹ for dilute solutions (x = 0.05) to 36.6 and 11.5 cm⁻¹, respectively, in pure TCAA. The formation of dimers was confirmed by multivariate analysis of the Raman spectra of chloral recorded as a function of temperature. Analogous analysis of dichloroacetyl chloride (DCAC) spectra gave an 8.9 cm⁻¹ blue shift for the ν(C H) vibration band and − 5.5/− 10.1 cm⁻¹ shifts for the ν(CO) stretching vibrations of the two conformers present. To facilitate the interpretation of experimental findings, the optimized geometries and vibrational wavenumbers of the Cl₃CCHO/HCl₂CCClO molecules and (Cl₃CCHO)₂/(HCl₂CCClO)₂ dimers were calculated at the B3LYP/6‐311 + + G(3df,3pd) level. Copyright © 2010 John Wiley & Sons, Ltd.     

冰水-溶液-炸药分子中耦合氢键的受激协同弛豫

与传统定义的氢键(X×××H)相比, 耦合氢键(X:H-Y)集成分子间的X:H非键和分子内的H-Y成键作用(X = N, O; Y = X, C;而且H也可以被电负性较低的金属如Cu取代). 耦合氢键具有两个显著的特征: 一是它的分段长度、能量、和振动频率的协同性, 二是其分段德拜比热的差异, 其关键在于它的两端负电载体间的排斥耦合和极化作用. 耦合氢键分段的德拜比热对温度的积分对应它们各自的结合能而德拜温度对应于振动频率. 因此,我们可以通过施加外场（温度,压强、配位,电场,等）调制耦合氢键的极化和协同弛豫以改变氢键网络结构和氢键体系的物理性能. 但是,耦合氢键的协同弛豫只有在Y—X排斥足够强和H-Y电负性差足够大的条件下发生. 耦合氢键的建立使我们不仅能够定量破解关于水的结构和冰水的诸多反常物性,而且加深了对酸碱盐和有机溶液的氢键网络和属性以及氮基炸药的结构稳定性和储能机理等的系统认知. 氢键耦合振子对的极化和协同弛豫为分子电子学提供了一个新的自由度以完整表述分子、电子、键合在时、空、能量域的受激行为. 所以, 由单分子基元动力学向耦合氢键和电子弛豫动力学的思维拓展,无论是对原子分子电子学的基础研究还是对实际工程应用都具有深远的意义.     

Theoretical investigations of the hydrogen bond in a tetraamido/diamino quaternized macrocycle

ABSTRACT

We present theoretical investigations on the nature and persistence of the strong central hydrogen bond of a tetraamido/diamino quaternized macrocycle. Our theoretical study of the NMR properties of the central hydrogen bond proved difficult to reconcile with the available experimental results, suggesting the possibility of the non-persistence of the central hydrogen bond of the macrocycle in solution. We demonstrate alternative scenarios, in which a tautomerization of the macrocycle in solution gives rise to the experimentally observed NMR shifts.     

Infrared Study of Solid Cyclopentanol

Abstract

Infrared absorption spectra of cyclopentanol-OH and -OD have been measured in the 16 - 3700 cm^?1 frequency range for crystal IV, III, II, I and liquid phases. The role of both the hydrogen bond and the conformation of a molecule in polymorphism is discussed.     

反尖晶石LiNiVO4中几何失措的抑制与磁有序

对反尖晶石结构的LiNiVO₄的磁学性质的研究表明：高温顺磁区研究表明材料存在自旋-轨道耦合作用;在低温区,由于其Li⁺/Ni²⁺无序占据八面体间隙位置,从而导致该材料几何失措效应的抑制;相应地体系呈现短程反铁磁有序态, Neel温度为35K.关键词：4')\" href=\"#\">LiNiVO₄自旋-轨道耦合短程反铁磁有序几何失措     

Infrared Study of Solid Cycloheptanol

Abstract

Infrared absorption spectra of cycloheptanol-OH have been measured in the 50–3700 cm^?1 frequency range for crystal II', II, I and liquid phases. Order-disorder behaviour concerning orientational, conformational and hydrogen-bond properties is discussed.