Infrared Spectra,Structures and Bonding of Binuclear Transition Metal Carbonyl Cluster Ions

Binuclear transition metal carbonyl clusters serve as the simplest models in understanding metal-metal and ligand bonding that are important organometallic chemistry catalysis. Binuclear first row transition metal carbonyl ions are produced via a pulsed laser vaporization/supersonic expansion cluster ion source in the gas phase. These ions are studied by mass-selected infrared photodissociation spectroscopy in the carbonyl stretching frequency region. Density functional theory calculations have been performed on the geometric structures and vibrational spectra of the carbonyl ions. Their geometric and electronic structures are determined by comparison of the experimental IR spectra with the simulated spectra. The structure and the metal-metal and metal-CO bonding of both saturated and unsaturated homonuclear as well as heteronuclear carbonyl cluster cations and anions are discussed.     

Octacarbonyl Anion Complexes of Group Three Transition Metals [TM(CO)8]− (TM=Sc,Y, La) and the 18‐Electron Rule

We report the gas‐phase synthesis of stable 20‐electron carbonyl anion complexes of group 3 transition metals, TM(CO)₈^? (TM=Sc, Y, La), which are studied by mass‐selected infrared (IR) photodissociation spectroscopy. The experimentally observed species, which are the first octacarbonyl anionic complexes of a TM, are identified by comparison of the measured and calculated IR spectra. Quantum chemical calculations show that the molecules have a cubic (O_h) equilibrium geometry and a singlet (¹A_1g) electronic ground state. The 20‐electron systems TM(CO)₈^? are energetically stable toward loss of one CO ligand, yielding the 18‐electron complexes TM(CO)₇^? in the ¹A₁ electronic ground state; these exhibit a capped octahedral structure with C_3v symmetry. Analysis of the electronic structure of TM(CO)₈^? reveals that there is one occupied valence molecular orbital with a_2u symmetry, which is formed only by ligand orbitals without a contribution from the metal atomic orbitals. The adducts of TM(CO)₈^? fulfill the 18‐electron rule when only those valence electrons that occupy metal–ligand bonding orbitals are considered.     

Chemical Bonding in Silicon Carbonyl Complexes

Although silylene-carbonyl complexes are known for decades, only recently isolable examples have been accomplished. In this work, the bonding situation is re-evaluated to explain the origins of their remarkable stability within the Kohn-Sham molecular orbital theory framework. It is shown that the chemical bond can be understood as CO interaction with the silylene via a donor-acceptor interaction: a σ-donation from the σ_CO into the empty p-orbital of silicon, and a π-back donation from the sp² lone pair of silicon into the π*_CO antibonding orbitals. Notably, it was established that the driving force behind the surprisingly stable Si−CO compounds, however, is another π-back donation from a perpendicular bonding R−Si σ-orbital into the π*_CO antibonding orbitals. Consequently, the pyramidalization of the central silicon atom cannot be associated with the strength of the π-back donation, in sharp contrast to the established chemical bonding model. Considering this additional bonding interaction not only shed light on the bonding situation, but is also an indispensable key for broadening the scope of silylene-carbonyl chemistry.     

氮化硼薄膜内应力的红外光谱研究

用射频(RF)磁控溅射制备了立方氮化硼(c-BN)薄膜。FTIR光谱和电子衍射实验表明:该薄膜是纯的,其结晶度很高。FTIR光谱研究指出,基板负偏压是c-BN相形成的重要因素,但也由此产生了c-BN薄膜的应力,且负偏压越高,产生的应力越大。比较透射谱和反射谱的结果,c-BN薄膜表面层的应力小于内部的。按照c-BN形成的压力模型,表面应力小到一定程度可能影响c-BN的继续生长。一个特制的分层结构BN薄膜保留了由于应力造成的c-BN的裂纹,这个裂纹分布在一些同心圆上,中心是缺陷或杂质,同心圆之间有明显的分界线,把c-BN表层分割成许多应力区。     

Polarization Dependent Time-Resolved Infrared Spectroscopy and Its Applications

Polarization dependent time-resolved infrared (TRIR) spectroscopy has proven to be a useful technique to study the structural dynamics in a photochemical process. The angular information of transient species is obtainable in this measurement, which makes it a valuable technique for the investigation of electron distribution, molecular structure, and conformational dynamics. In this review, we briefly introduce the principles and applications of polarization dependent TRIR spectroscopy. We mainly focused on the following topics: (i) an overview of TRIR spectroscopy, (ii) principles of TRIR spectroscopy and its advantages compared to the other ultrafast techniques, (iii) examples that use polarization dependent TRIR spectroscopy to probe a variety of chemical and dynamical phenomena including protein conformational dynamics, excited state electron localization, and photoisomerization, (iv) the limitations and prospects of TRIR spectroscopy.     

Infrared Spectroscopy of Dioxouranium(V) Complexes with Solvent Molecules: Effect of Reduction

UO₂⁺–solvent complexes having the general formula [UO₂(ROH)]⁺ (R=H, CH₃, C₂H₅, and n‐C₃H₇) are formed using electrospray ionization and stored in a Fourier transform ion cyclotron resonance mass spectrometer, where they are isolated by mass‐to‐charge ratio, and then photofragmented using a free‐electron laser scanning through the 10 μm region of the infrared spectrum. Asymmetric O=U=O stretching frequencies (ν₃) are measured over a very small range [from ～953 cm^?1 for H₂O to ～944 cm^?1 for n‐propanol (n‐PrOH)] for all four complexes, indicating that the nature of the alkyl group does not greatly affect the metal centre. The ν₃ values generally decrease with increasing nucleophilicity of the solvent, except for the methanol (MeOH)‐containing complex, which has a measured ν₃ value equal to that of the n‐PrOH‐containing complex. The ν₃ frequency values for these U(V) complexes are about 20 cm^?1 lower than those measured for isoelectronic U(VI) ion‐pair species containing analogous alkoxides. ν₃ values for the U(V) complexes are comparable to those for the anionic [UO₂(NO₃)₃]^? complex, and 40–70 cm^?1 lower than previously reported values for ligated uranyl(VI) dication complexes. The lower frequency is attributed to weakening of the O?U?O bonds by repulsion related to reduction of the U metal centre, which increases electron density in the antibonding π* orbitals of the uranyl moiety. Computational modelling of the ν₃ frequencies using the B3LYP and PBE functionals is in good agreement with the IRMPD measurements, in that the calculated values fall in a very small range and are within a few cm^?1 of measurements. The values generated using the LDA functional are slightly higher and substantially overestimate the trends. Subtleties in the trend in ν₃ frequencies for the H₂O–MeOH–EtOH–n‐PrOH series are not reproduced by the calculations, specifically for the MeOH complex, which has a lower than expected value.     

炸药爆轰合成纳米石墨的红外光谱研究

石墨是碳材料中最常见的结晶状态,它具有耐高温、抗腐蚀、自润滑、无毒及价格低廉等特点,广泛应用于润滑剂和添加剂等方面^[1].由于高纯纳米石墨粉在某些高新技术领域中有较好的应用前景,近些年来得到开发和应用,如制成复合导电材料、吸波材料及储氢材料等^[2].以前有学者用纳米金刚石粉加热相转变^[3]和高能球磨^[4,5]的方法制备了纳米石墨,在制备碳纳米管时也有石墨的纳米粒子生成^[6].但用这几种方法制备纳米石墨,既费时又消耗较大能量,成本非常高.     

Thermodynamics and Spectroscopy of Halogen- and Hydrogen-Bonded Complexes of Haloforms with Aromatic and Aliphatic Amines

Similarities and differences of halogen and hydrogen bonding were explored via UV–Vis and ¹H NMR measurements, X-ray crystallography and computational analysis of the associations of CHX₃ (X=I, Br, Cl) with aromatic (tetramethyl-p-phenylenediamine) and aliphatic (4-diazabicyclo[2,2,2]octane) amines. When the polarization of haloforms was taken into account, the strengths of these complexes followed the same correlation with the electrostatic potentials on the surfaces of the interacting atoms. However, their spectral properties were quite distinct. While the halogen-bonded complexes showed new intense absorption bands in the UV–Vis spectra, the absorptions of their hydrogen-bonded analogues were close to the superposition of the absorption of reactants. Additionally, halogen bonding led to a shift in the NMR signal of haloform protons to lower ppm values compared with the individual haloforms, whereas hydrogen bonding of CHX₃ with aliphatic amines resulted in a shift in the opposite direction. The effects of hydrogen bonding with aromatic amines on the NMR spectra of haloforms were ambivalent. Titration of all CHX₃ with these nucleophiles produced consistent shifts in their protons’ signals to lower ppm values, whereas calculations of these pairs produced multiple hydrogen-bonded minima with similar structures and energies, but opposite directions of the NMR signals’ shifts. Experimental and computational data were used for the evaluation of formation constants of some halogen- and hydrogen-bonded complexes between haloforms and amines co-existing in solutions.     

Mononuclear Carbonyl Anion Complexes of Groups Ⅳ and Ⅴ Metals

The anionic carbonyl complexes of groups IV and V metals TM(CO)\begin{document}$ _{6,7} $\end{document} (TM=Ti, Zr, Hf, V, Nb, Ta) are prepared in the gas phase using a laser vaporation-supersonic expansion ion source. The infrared spectra of TM(CO)\begin{document}$ _{6,7} $\end{document}\begin{document}$ ^- $\end{document} anion complexes in the carbonyl stretching frequency region are measured by mass-selected infrared photodissociation spectroscopy. The six-coordinated TM(CO)\begin{document}$ _6 $\end{document}\begin{document}$ ^- $\end{document} anions are determined to be the coordination saturate complexes for both the group IV and group V metals. The TM(CO)\begin{document}$ _6 $\end{document}\begin{document}$ ^- $\end{document} complexes of group IV metals (TM=Ti, Zr, Hf) are 17-electron complexes having a \begin{document}$ ^2 $\end{document}A\begin{document}$ _{\rm{1g}} $\end{document} ground state with \begin{document}$ D_{\rm{3d}} $\end{document} symmetry, while the TM(CO)\begin{document}$ _6 $\end{document}\begin{document}$ ^- $\end{document} complexes of group V metals (TM=V, Nb, Ta) are 18-electron species with a closed-shell singlet ground state possessing \begin{document}$ O_{\rm{h}} $\end{document} symmetry. The energy decomposition analyses indicate that the metal-CO covalent bonding is dominated by TM\begin{document}$ ^- $\end{document}(d)\begin{document}$ \rightarrow $\end{document}(CO)\begin{document}$ _6 $\end{document} \begin{document}$ \pi $\end{document}-backdonation and TM\begin{document}$ ^- $\end{document}(d)\begin{document}$ \leftarrow $\end{document}(CO)\begin{document}$ _6 $\end{document} \begin{document}$ \sigma $\end{document}-donation interactions.     

高聚物的动态红外光谱研究

动态红外光谱法是研究高聚物在外加力场作用下变形或松弛现象的极为有用的手段。本文介绍了动态红外光谱法的实验技术以及若干近期的研究结果。     

A Systematic Investigation of Coinage Metal Carbonyl Complexes Stabilized by Fluorinated Alkoxy Aluminates

The reaction of Cu^I, Ag^I, and Au^I salts with carbon monoxide in the presence of weakly coordinating anions led to known and structurally unknown non‐classical coinage metal carbonyl complexes [M(CO)_n][A] (A=fluorinated alkoxy aluminates). The coinage metal carbonyl complexes [Cu(CO)_n(CH₂Cl₂)_m]⁺[A]^? (n=1, 3; m=4?n), [Au₂(CO)₂Cl]⁺[A]^?, [(OC)_nM(A)] (M=Cu: n=2; Ag: n=1, 2) as well as [(OC)₃Cu???ClAl(OR^F)₃] and [(OC)Au???ClAl(OR^F)₃] were analyzed with X‐ray diffraction and partially IR and Raman spectroscopy. In addition to these structures, crystallographic and spectroscopic evidence for the existence of the tetracarbonyl complex [Cu(CO)₄]⁺[Al(OR^F)₄]^? (R^F=C(CF₃)₃) is presented; its formation was analyzed with the help of theoretical investigations and Born–Fajans–Haber cycles. We discuss the limits of structure determinations by routine X‐ray diffraction methods with respect to the C? O bond lengths and apply the experimental CO stretching frequencies for the prediction of bond lengths within the carbonyl ligand based on a correlation with calculated data. Moreover, we provide a simple explanation for the reported, partly confusing and scattered CO stretching frequencies of [Cu^I(CO)_n] units.     

Structural and Infrared Spectroscopic Study on Solvation of Acetylene by Protonated Water Molecules

The effect of solvation on the conformation of acetylene has been studied by adding one water molecule at a time. Quantum chemical calculations of the H⁺(C₂H₂)(H₂O)_n (n=1-5) clusters indicate that the H₂O molecules prefer to form the OH…π interaction rather than the CH…O interaction. This solvation motif is different from that of neutral (C₂H₂)(H₂O)_n (n=1-4) clusters, in which the H₂O molecules prefer to form the CH…O and OH…C H-bonds. For the H⁺(C₂H₂)(H₂O)_n cationic clusters, the first solvation shell consists of one ring structure with two OH…π H-bonds and three water molecules, which is completed at n=4. Simulated infrared spectra reveal that vibrational frequencies of OH…π H-bonded O-H stretching afford a sensitive probe for exploring the solvation of acetylene by protonated water molecules. Infrared spectra of the H⁺(C₂H₂)(H₂O)_n(n=1-5) clusters could be readily measured by the infrared photodissociation technique and thus provide useful information for the understanding of solvation processes.     

基于支持向量机的羰基化合物红外光谱研究

设计了一个4层分等级分类系统，通过支持向量机技术对羰基化合物的红外光谱成功地进行了信息分类和提取，并与人工神经网络进行比较，结果表明：支持向量机对羰基类化合物红外光谱分类效果优于人工神经网络；另外详细探讨了表征酰胺类化合物的特征光谱峰片段对识圳伯仲叔酰胺的影响，证明了酰胺的N-H伸缩振动峰对识别伯仲叔酰胺贡献最大，为构建红外光谱智能解析系统提供了定量依据。     

红外反射光谱法在金属表面光洁度表征中的应用

本研究利用傅里叶变换红外反射光谱技术,通过对比不同光洁度的金属表面红外反射光谱图,建立了利用傅里叶变换红外反射光谱表征金属表面光洁度的方法,本文从红外反射光谱图4000cm-1～600cm-1、3400cm-1～2600cm-1波段的斜率及4000cm-1、3000cm-1、2000cm-1波数处的反射率两方面进行考察,结果表明,斜率和某一波数处的反射率均能用来表征金属表面的光洁度,且具有较高的准确性。     

二茂铁填充的双壁碳纳米管的合成与红外光谱表征

通过气相法将二茂铁填充到双壁碳纳米管的纳米空腔内部, 制备了一种新型纳米杂化材料——二茂铁-双壁碳纳米管. 对这种纳米材料进行了高分辨透射电子显微镜结构分析与傅立叶变换红外光谱表征. 红外光谱研究结果表明, 碳纳米管管壁与内部二茂铁之间存在强的电子相互作用,并伴有电子转移.     

Matrix isolation study of the photochemical reaction of cyclohexane and cyclohexene with CrCl2O2

The matrix isolation technique, combined with infrared spectroscopy, has been used to characterize the products of the photochemical reactions of cyclohexane and cyclohexene with CrCl₂O₂. While initial twin jet deposition of the reagents led to no visible changes in the recorded spectra, strong product bands were noted following irradiation with light of λ > 300 nm. The irradiation was shown to lead to oxygen atom transfer, forming complexes between cyclic alcohol derivatives and CrCl₂O, although complexes between ring expansion products and CrCl₂O could not be ruled out. This latter result could arise from C-C bond activation and oxygen atom insertion into a C-C bond. For the cyclohexene system, the cyclohexanone-CrCl₂O complex was also observed. The identification of the complexes was further supported by isotopic labeling (²H) and by density functional calculations at the B3LYP/6-311G++(d,2p) level.     

四（对—羟基）苯基卟啉配合物的傅里叶变换红外光声光谱

四（对-羟基）苯基卟啉（H2THPP）不仅能作为分析试剂，而且有一定的抗癌活性，还可作为合成卟啉类液晶材料的中间体．这种配体及其配合物由于颜色深、透光性能差和散射较强，用普通红外光谱法开展其振动光谱研究存在一定的困难．我们在用红外光声光谱（FTIR－PAS）技术[1]成功地研究了部分过渡金属、稀土金属叶琳配合物的基础上[2，3]，测试并研究了H2THPP及其Cr（III）、Mn（III）、Fe（III）、Co（II）、Ni（II）、Cu（II）、Zn（II）配合物在3700～200cm－1范围内的FTIR－PAS．对主要谱带进行了经验归属，讨论了配…     

红外光谱法对六氟磷酸锂的快速定量分析

本文建立了一种用傅里叶红外光谱(FT-IR)法快速定量分析LiPF6的方法。采用红外光谱(IR)法和X射线衍射(XRD)法对LiPF6样品进行了定性分析。选取LiPF6红外光谱847cm-1处的特征吸收峰为分析对象,利用吸光度峰面积积分法进行定量分析,由标准曲线可知,LiPF6的含量与其红外光谱特征峰的吸收强度有很好的线性关系,相关系数达0.9998,线性范围在0.04～25mg.mL-1,检出限可达0.02mg.mL-1。LiPF6样品定量测定的相对标准偏差(RSD)约为0.18%,回收率为96%～98%。