Quantum-mechanical calculation of the frequencies of the normal vibrations and intensities of the IR and Raman bands of pyridine N-oxide

The frequencies of the normal vibrations and the intensities of the bands in the IR and Raman spectra of pyridine N-oxide and three of its isotopomers are calculated with the density functional theory by using the Becke exchange and Lee-Yang-Parr correlation functionals with the 6?311+G(d, p) basis set. The scaling of the force constants in independent natural coordinates is performed. The force field of pyridine N-oxide in independent symmetry coordinates is obtained. A new assignment of the frequencies of some vibrations in the isotopomers is proposed. On the basis of the calculated frequencies and intensities, the vibrational IR and Raman spectra of pyridine N-oxide are modeled.     

Spectroscopic studies of the lanthanide(III) ions with pyridine carboxylic acid N-oxide ligands and in mixed ligand complexes

A series of Ln(III) complexes with pyridine carboxylic acid-N-oxides (L) Ln-L, and mixed ligand complexes of Ln-L plus bipyridine (bipy) or 1,10-phenanthroline (O-phen) (X) Ln-L-X have been studied. These complexes were characterized in solution using Nd(III) absorption in the spectral range of the ⁴I_9/2 → ⁴G_5/2 transition corresponding to the hypersensitive band, and in the solid state with the use of IR and Eu(III) luminescence spectroscopy. In solutions a series of Nd(III) complexes and mixed ligand complexes has been examined and the formation of binary LnL and LnL₂ complexes and mixed ligand LnL₂X complexes evidenced. Solid complexes of Eu(III) with nicotinic acid N-oxide and ternary with nicotinic acid N-oxide plus phen were studied with the use of Eu(III) luminescence lifetime measurements and IR spectroscopy, proving the formation of binary [Eu(nicN-oxide)₃(H₂O)₂].2H₂O and ternary [Eu(nicN-oxide)₃phen].H₂O complexes.     

C-13 NMR Spectra of N-Aminopyridinium Perchlorates

C-13 NMR spectra of fifteen N-aminopyridinium perchlorates show the effect of amination of the ring nitrogen atom to be similar to that observed in the pyridine N-oxide spectra, particularly for the 2(6) and 3(5) positions. Benzene and pyridine increments predict well the carbon chemical shifts for the title compounds unless both positions 2 and 6 are occupied. The chemical shifts of some carbon atoms in the compounds studied are linearly dependent on those in the respective benzene derivatives as well as on the Hammett σ constants.     

Intra‐ and intermolecular N?H···O hydrogen bonds in pyrrolyl derivatives of indane‐1,3‐dione – experimental and theoretical study

2‐(Pyrrol‐2‐ylmethylene)‐1,3‐indandione ( 4 ) and 2‐(pyrrol‐2‐ylmethylene)‐3‐dicyanomethylidene‐1‐indanone ( 5 ) were synthesized. Multinuclear and 2D‐NMR, IR, UV spectroscopic investigations as well as quantum chemical calculations showed the presence of strong hydrogen bonding in these molecules. For both molecules, the presence of two conformers, with and without H‐bond, was experimentally detected in the basic solvents (DMSO, acetone, pyridine) and the solvate complexes were theoretically calculated. Specific behavior of the intramolecular H‐bonded complexes different from that of the intermolecular H‐complexes is discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Simulation of the Electron Paramagnetic Resonance Spectrum of the Triplet Ground State Dimer Di-μ-(Pyridine N-Oxide)Bis[Bisnitrato(Pyridine N-Oxide)Copper(II)]

The EPR spectrum of the triplet ground state dimer di-μ-(pyridine N-oxide)bis[bisnitrato(pyridine N-oxide)copper(II)] has been reported recently¹. Of the very few triplet ground state copper(II) dimers with resolved metal hyperfine structure^2,3, the EPR spectrum of this complex is most complete. Previously, the analysis of the spectra of triplet ground state copper(II) complexes, in order to extract magnetic parameters, has been made using the equations reported by Wasserman et al.⁴ The best magnetic parameters should be obtained from a simulation of the experimental spectrum. We wish to report here the computer simulation of the EPR spectrum of a powdered sample of [Cu(II) (PYO)₂ (NO₃)₂]₂.     

The oxidation of fullerene[C60] with various amine N-oxides under ultrasonic irradiation

The reaction of C60 with various amine N-oxides such as 3-picoline N-oxide (Aldrich 98.0%), pyridine N-oxide hydrate (Aldrich 95.0%), quinoline N-oxide (Aldrich 97.0%), isoquinoline N-oxide (Aldrich 98.0%) under ultrasonic irradiation in air at 25-43 degrees C causes the oxidation of fullerene[C60(O)n] (n=1-2 or n=1). The MALDI-TOF MS, UV-vis spectra, and HPLC profile confirmed that the products of fullerene oxidation are [C60(O)n] (n=1-2 or n=1).     

Study of chemical bonding in the interhalogen complexes based on density functional theory

The density functional theory analysis was used for a number XYL complexes (XY is a dihalogen molecule and L is a Lewis base), formed between molecules I₂, ICl, IBr and pyridine. The calculated geometrical parameters, IR spectra and nuclear quadrupole interaction constants of iodine are consistent with the data of microwave spectroscopy and nuclear quadrupole resonance. The good correlation between the experimental and calculated binding energies of the inner electrons of iodine, chlorine and nitrogen atoms were found with the calculation using both Gaussian and Slater functions. The comparison of experimental and calculated changes in the electron density on the atoms upon complex formation suggested the choice of scheme for calculating the effective charge on the atoms, which allow us to interpret the experimental spectra. It is shown that the use of both calculated schemes allows us to predict the enthalpy of complex formation in close agreement with the experimental values. The energy analysis shows that in the complexes the electrostatic binding energy dominates that of covalent binding.     

Infrared and 1H nuclear magnetic resonance studies of solvent effect on hydrogen bond in some pyridine n-oxide trifluoroacetates

The IR and ¹H NNR spectra are reported for the trifluoroacetates of five substituted pyridine N-oxides in five dry aprotic solvents of different polarity and studied with respect to the influence of the reaction field. Both the centre of gravity ($\text{V}$_H) of continuous absorption and the chemical shift (δ) show weak dependence upon solvent polarity. In the range of ε from 2.27 to 10.36 the continuous absorption is very similar. In acetonitrile (ε = 37.5) $\text{V}$_H is shifted. The magnitude and sign of the $\text{V}$_H shift depend on the proton acceptor properties of N-oxides and can be correlated with the position of the proton in the complex. The influence of the reaction field on OHO bonds is compared with the influence on OH?N?O^??HN⁺ bonds, and the differences in behavior of these complexes are related to their energy surface. The weak dependence of $\text{V}$_H and δ upon the reaction field in pyridine N-oxide trifluoroacetates is consistent with the single minimum energy surface postulated in the literature for the strong OHO bonds.     

Raman,FT‐IR,and DFT studies of 3,5‐pyrazoledicarboxylic acid and its Ce(III) and Nd(III) complexes

3,5‐Pyrazoledicarboxylic acid was used as a ligand for the synthesis of its Ce(III) and Nd(III) complexes. The complexes of Ce(III) and Nd(III) with 3,5‐pyrazoledicarboxylic acid were synthesized and their compositions were determined by elemental analysis. Vibrational study in the solid state of 3,5‐pyrazoledicarboxylic acid and its new Ce(III) and Nd(III) complexes was performed by IR and Raman spectroscopy. The changes observed between the IR and Raman spectra of the ligand and of the complexes allowed us to establish the coordination mode of the metal in both complexes. The comparative vibrational analysis of the free ligand and its lanthanide(III) complexes gave evidence that 3,5‐pyrazoledicarboxylic acid binds Ln(III) through the deprotonated carboxylic oxygens. The density functional theory (DFT) calculated geometries, harmonic vibrational modes and Raman scattering activities of the ligand were in good agreement with the experimental data, and a complete vibrational assignment is being proposed. The experimental IR and Raman bands of the ligand were assigned to normal modes on the basis of DFT calculations. The effect of the intramolecular hydrogen bonds in the ligand on vibrational mode positions is also discussed. The characteristic IR and Raman bands of 3,5‐pyrazoledicarboxylic acid and its lanthanide complexes were specified and discussed. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis and characterization of blue phosphorescent cyclometalated Ir(III) complexes containing 2-(imidazol-2-yl)pyridine as ancillary ligand

Four new blue phosphorescent iridium complexes containing 2-(fluoro substituted phenyl)pyridine as the cyclometalated ligands and 2-(imidazol-2-yl)pyridine as an ancillary ligand have been synthesized and characterized. The complexes have the general structure (C^N)₂Ir(pym), where C^N are cyclometalating ligands (e.g., 2-(2,4-difluorophenyl)pyridine (24f₂ppyH), 2-(3,4-difluorophenyl)pyridine (34f₂ppyH), 2-(3,5-difluorophenyl)pyridine (35f₂ppyH), and 2-(3,4,5-trifluorophenyl)pyridine (345f₃ppyH)), pym is 2-(imidazol-2-yl)pyridine (pymH). The absorption, emission, and cyclic voltammetry of the complexes were systematically investigated. The (46f₂ppy)₂Ir(pym) has been characterized using X-ray crystallography and the electronic ground state calculated using B3LYP density functional theory. The highest occupied molecular orbital (HOMO) consists of a mixture of pym ligand (83.7%) and Ir orbitals (12.1%), while the lowest occupied molecular orbital (LUMO) is mostly on f₂ppy ligands (93.4%). By replacing the ancillary ligand pic with pym can finely tune emission of the iridium complexes, showing blue luminescence at a wavelength of 467-491 nm at room temperature in CH₂Cl₂.     

VO(Ⅱ)-蛋氨酸-邻菲咯啉配合物的结构与波谱

测定了VOSO4与蛋氨酸(Met)及VOSO4与蛋氨酸、邻菲咯啉(Phen)在不同酸度(pH=1~14)的乙二醇/水(1:1)溶液中的低温EPR波谱,发现在不同pH下生成不同组成、结构的配合物,利用Johnson加合规则并结合IR,推测了不同pH下生成配合物的可能结构.根据EPR波谱参数计算了配合物的键参数,得出随溶液pH值增大,氨基酸取代的水分子数增多,生成配合物的δ2值下降,即共价键成份增加.利用电子光谱数据计算了配合物的晶体场参数,讨论了成配规律,得出Phen与VO (Ⅱ)配位能力比Met强得多.     

The effect of an anti-hydrogen bond on Fermi resonance:A Raman spectroscopic study of the Fermi doublet ν1-ν12 of liquid pyridine

The effects of an anti-hydrogen bond on the ν1-ν12 Fermi resonance(FR) of pyridine are experimentally investigated by using Raman scattering spectroscopy.Three systems,pyridine/water,pyridine/formamide,and pyridine/carbon tetrachloride,provide varying degrees of strength for the diluent-pyridine anti-hydrogen bond complex.Water forms a stronger anti-hydrogen bond with pyridine than with formamide,and in the case of adding non-polar solvent carbon tetrachloride,which is neither a hydrogen bond donor nor an acceptor and incapable of forming a hydrogen bond with pyridine,the intermolecular distance of pyridine will increase and the interaction of pyridine molecules will reduce.The dilution studies are performed on the three systems.Comparing with the values of the Fermi coupling coefficient W of the ring breathing mode ν1 and triangle mode ν12 of pyridine at different volume concentrations,which are calculated according to the Bertran equations,in three systems,we find that the solution with the strongest anti-hydrogen bond,water,shows the fastest change in the ν1-ν12 Fermi coupling coefficient W with the volume concentration varying,followed by the formamide and carbon tetrachloride solutions.These results suggest that the stronger anti-hydrogen bond-forming effect will cause a greater reduction in the strength of the ν1-ν12 FR of pyridine.According to the mechanism of the formation of an anti-hydrogen bond in the complexes and the FR theory,a qualitative explanation for the anti-hydrogen bond effect in reducing the strength of the ν1-ν12 FR of pyridine is given.     

氯铝酸离子液体酸性的红外光谱探针和量子化学研究

文章采用吡啶探针红外光谱、吡啶递增吸附实验研究和量子化学理论计算相结合的方法深入研究了氯铝酸离子液体的酸性及氯铝酸离子液体Lewis酸位Al₂Cl-₇与吡啶吸附之间的相互作用机理。通过实验和理论计算研究发现,Al₂Cl-₇,AlCl-₄阴离子具有吸电性,能够吸引吡啶环上的孤对电子产生吸附作用,具有Lewis酸性,它们分别呈现吡啶探针红外光谱Lewis酸特征峰;通过红外光谱特征峰峰位、键长及电荷分布分析表明Al₂Cl-₇的酸性强于AlCl-₄;氯铝酸离子液体Lewis酸位Al₂Cl-₇与吡啶吸附的机理为：当吡啶含量小时,仅存在Py-Al₂Cl-₇吸附;当吡啶量增加到一定程度时,Py-Al₂Cl-₇配位络合物中的AlCl-₄容易与吡啶发生吸附解离为Py-AlCl-₄配位络合物和Py-AlCl₃配位络合物,导致离子液体吡啶递增吸附红外特征峰发生变化。     

铕(Ⅲ)-4-乙烯基吡啶共聚物稀土高分子配合物的合成及其光物理行为的研究

以4-乙烯基吡啶（4VP）与甲基丙烯酸甲酯（MMA）的共聚物为配体，并以邻菲洛啉（Phen)及2，2′-联吡啶（Bipy)小分子配体协同反应，与Eu(Ⅲ）配位，合成了稀土高分子配合物；通过FTIR表征了配合物的结构；通过紫外光谱与荧光光谱的测定，较充分地研究了稀土高分子配合物光致发光的光物理过程，实验结果表明，4-乙烯基吡啶共聚物通过吡啶环上的氮原子与稀土离子可直接配位；小分子配体的协同配位，可使稀土离子配位数趋于满足，且由于小分子配体能有效地加强能量吸收及分子内的能量传递，大大增强了配合物的荧光强度。     

The detection by SERS of resonantly excited desorption of pyridine from silver island films by IR laser absorption

We have shown that when a very thin film of pyridine about two or three monolayers thick on a silver island film is exposed to a pulsed CO₂ laser line whose frequency corresponds to that of a pyridine vibrational mode the physisorbed molecules within the pyridine film can be desorbed even at liquid He temperatures. It is interesting that this observation was first made using surface enhanced Raman scattering. Experimental results are presented from which it is concluded that the phenomenon can be described as resonantly excited desorption. The absorbed IR energy seems to be localized within the pyridine film and the silver film and thermallized to some degree causing some of the physisorbed molecules to desorb. Analysis of the SERS spectra before and after the resonantly excited desorption has enabled us to separate out the SERS spectra due to the physisorbed pyridine and the chemisorbed pyridine.     

The EPR Spectrum of Di-μ-(pyridine N-oxide) bis [bisnitrato(pyridine N-oxide)copper(II)] in the Corresponding Zinc(II) Crystal

It has been shown^1–3 that the exchange interactions in the dimeric⁴ complex di-μ-(pyridine N-oxide) bis [bisnitrato(pyridine N-oxide) copper(II)], [Cu(pyO)₂]₂ lead to a triplet ground state for the copper(II) pairs. The triplet state epr spectrum has been observed^1,3,5,6 for a powdered sample of the complex coprecipitated with the corresponding zinc(II) complex, and the computer simulation of this spectrum has been carried out by two different groups^3,5,6. As is often the case when dealing with spectra of powdered samples, there exist ambiguities with the spectrum of [Cu(pyO)₂-(NO₃)₂]₂ since all of the resonances were not observed, and consequently, the interpretation and values of the parameters remain in question. It was felt that examination of the epr spectra of single crystal samples should permit a rigorous analysis of this problem.     

2-吡啶甲醇红外光谱的密度泛函理论研究

利用密度泛函理论(density functional theory,DFT) 在B3LYP/6-311G(d,p)水平上对2-吡啶甲醇分子进行了结构优化和频率计算,得到了该分子的稳定构型和全部振动模式。通过与吡啶分子的结构参数以及相关文献数据的对比,发现理论值与实验值相吻合。理论计算和实验测得的红外光谱数据的比较分析表明,理论计算与实验测量结果符合得较好, 并对2-吡啶甲醇分子的振动模式进行了归属。     

Spectroscopic investigations and computational study of sulfur trioxide–pyridine complex

The Fourier transform infrared (FT‐IR) and FT‐Raman spectra of sulfur trioxide‐pyridine complex were recorded and analyzed. The potential‐dependent surface‐enhanced Raman scattering (SERS) was recorded from an electrochemically roughened silver electrode. The vibrational wave numbers of the compound were computed using the Hartree–Fock/6‐31G* basis and compared with the experimental values. The presence of strong pyridine ring vibrations in the SERS spectrum reveals the interaction between the pyridine ring and the silver surface. The molecule is adsorbed on the silver surface with the pyridine ring in a tilted orientation. The direction of charge‐transfer contribution to the SERS is discussed from the frontier orbital theory. The value of the calculated first hyperpolarizability is comparable to those reported for similar structures, which makes this molecule an attractive object for future studies of nonlinear optics. The optimized geometrical parameters of the title compound are in agreement with similar reported structures. Copyright © 2011 John Wiley & Sons, Ltd.     

VO (Ⅱ)-天冬氨酸-π受体三元混配络合物的结构及其ESR波谱研究

测定了VOSO₄与天冬氨酸(asp)和邻菲罗啉(phen)及联吡啶(bipy)三元体系在不同酸度(pH=1-14)的乙二醇-水(1:1)溶液中低温ESR波谱,发现不同pH下生成不同组成和结构的络合物,利用Johnson加合规则并配合IR推测了它们的可能结构,利用电子光谱数据,计算了络合物晶体场参数。     

铼配合物光异构化的拉曼和红外光谱研究

光敏分子和它们在光作用下发生的异构化一直是分子光化学研究领域中感光趣的课题。含有光敏基团的铼配合物的一个新颖特性是其具有电致发光性质。为弄清结构与功能性质的联系 ,本文研究了 Re(CO) 3 (2 ,2 '-联吡啶 ) [4- (4'-硝基苯己烯基吡啶 ) ]高氯酸盐的 FT-Raman和 FT- IR光谱 ,指认了光照前和光照后的拉曼位移。讨论了这些变化与金属到配体电荷转移的联系