Probing mixed valence in a new tppz-bridged diruthenium(III,II) complex {(mu-tppz)[Ru(bik)Cl]2}3+ (tppz=2,3,5,6-tetrakis(2-pyridyl)pyrazine, bik=2,2'-bis(1-methylimidazolyl)ketone): EPR silence, intervalence absorption, and nu(CO) line broadening

The complex dication of the diruthenium(II) compound {(mu-tppz)[Ru(bik)Cl]2}(ClO4)2 can be oxidized and reduced in two one-electron steps each. In CH3CN/0.1 M Bu4NPF6, the odd-electron intermediates{(mu-tppz)[Ru(bik)Cl]2}n+, n=1 and 3, have comproportionation constants of 7x10(8) and 1x10(5), respectively. Both exhibit near-infrared absorptions, in the case of n=3 the 1640 nm band (epsilon=1200 M-1 cm-1, Deltanu1/2=1560 cm-1) is attributed to an intervalence charge-transfer transition. While the mixed-valent intermediate (n=3) is EPR silent even at 4 K, the n=1 form shows g(parallel) 2.005 and g( perpendicular) 1.994 at that temperature, signifying a diruthenium(II) complex of the tppz*- radical anion. The variation of energy and intensity of nuCO and of the ring vibration band around 1590 cm-1 has been monitored not only for {(mu-tppz)[Ru(bik)Cl]2}n+, n=0-4, but also for the mononuclear {(tppz)Ru(bik)Cl}n+, n=0-2. In the dinuclear complex the carbonyl stretching bands of the spectator ligand bik are shifted by about 15 cm-1 on each one-electron-transfer step, increasing with the positive charge. The mixed-valent {(mu-tppz)[Ru(bik)Cl]2}3+ shows a perceptibly broader nuCO band, suggesting incomplete valence averaging (partial localization).     

不同电解质体系水的拉曼谱的研究

通过一系列电解质体系水的拉曼光谱测量，得到了阴、阳离子种类和浓度引起的水伸缩振动和弯曲振动谱带丰富的变化信息，ＣｌＯ４＾－能有效地破坏水分子间的氢键，随着ＣｌＯ４浓度的增加，水分子间的氢键并非逐步被打断，而是氢键被破坏的水分子越来越多，从而使水分子有序度增大，这种氢键破坏方式符合水的混合模型（ＭｉｘｔｕｒｅＭｏｄｅｌ）ＳＯ＾２－４浓度的增对水的Ｒａｍａｎ光谱影响较小，是由于ＳＯ＾２－４与水分了间的     

稀土元素与L-酪氨酸和甘氨酸三元固态配合物的合成及表征

目前稀土与氨基酸三元固态配合物的研究着重于少数稀土-氨基酸-非氨基酸类型.本文报道了10种稀土与L-酪氨酸(Tyr,HO——CH_2(NH_2)CHCOOH)和甘氨酸(Gly,NH_2CH_2COOH)三元固态配合物的合成及FTIR光谱、质谱表征.     

Vibrational circular dichroism analysis reveals a conformational change of the baccatin III ring of paclitaxel: visualization of conformations using a new code for structure-activity relationships

The comparison between measured and conformer-weighted calculated VCD spectra of the baccatin III ring of paclitaxel and visualization of the conformations using the new code for structure-activity relationships are reported for the first time. The VCD spectrum of paclitaxel closely resembles that of the baccatin III ring. The large characteristic nuCO VCD bands with bisignate signs (1732 cm-1, Deltaepsilon = -1.6 x 10(-1); 1715 cm(-1), Deltaepsilon = 2.4 x 10(-1)) strongly reflect the structural property of the family of conformations bacc-ABC32F defined using the new code. The comparison with the conformation of the baccatin III core in the electron micrograph of the crystal structure of tubulin-paclitaxel (1JFF) suggests a conformational change of paclitaxel corresponding to a switch through the binding with beta-tublin and the intermolecular interactions involving the hydroxyl group (D) and carbonyl of acetoxy group (E). The representation of conformational codes allows complicated conformations to be very easily compared and facilitates future computational analyses such as those for the large-molecule calculations as well as genome analysis.     

吲哚啉螺苯并吡喃化合物红外光谱的研究

<正> 吲(?)啉螺苯并吡喃是人们研究的比较多的一类光致变色化合物。我们是在N-(β-羟乙基)-3′,3′-二甲基-6-R-8-R′吲哚啉[2,2′-(2H-1)]苯并吡喃及其衍生物合成的基础上研究其红外光谱。这些化合物的羟基伸缩振动谱带在3420—3220cm~(-1),强度大而谱带宽(见图1-a);羟基变形振动在1060—1020cm(~1)之间。若分子中的6-或8-位存在硝基,羟基伸缩振动谱带变窄,强度降低,并且有双带出现的现象(见图l-b).C(?)—O—     

Calpha-H bond-stretching frequency in alcohols as a probe of hydrogen-bonding strength: a combined vibrational spectroscopic and theoretical study of n-[1-D]propanol

The sensitivity of the nu(C)()alpha(-)(H/D) vibrational stretching frequency to hydrogen bonding in alcohols is examined by infrared and Raman spectroscopy, supported by DFT(B3LYP)/6-311++G(d,p) calculations. The model compound studied is (R,S)-n-[1-D]propanol. It is shown that the nu(C)()alpha(-)(H/D) mode can be successfully correlated with the hydrogen-bond strength in a given solvent, provided the O-H group involved in the hydrogen bond is not acting simultaneously as a hydrogen-bond donor and acceptor. In addition, a detailed analysis of the spectroscopic features observed in both the nu(O)(-)(H) and nu(C)()alpha(-)(H/D) spectral regions of the spectra of n-propanol and (R,S)-n-[1-D]propanol, in a series of different experimental conditions, which include the matrix-isolated compound (in argon matrix), pure liquid and low-temperature glassy states, and solution in different solvents, is undertaken. This permits the contribution of the different conformers of the studied compounds to be assigned to the bands observed in the nu(O)(-)(H) and nu(C)(-)(H) spectral regions.     

IR and NMR spectral studies of 4-bromo-1-naphthyl chalcones-assessment of substituent effects

Infrared nuCO (cm(-1)) of s-cis and s-trans frequencies and nuclear magnetic resonance chemical shifts delta(1)H (ppm) of H-alpha and H-beta, delta(13)C (ppm) of C-alpha and C-beta data were assigned from their respective spectra of a series of various substituted styryl 4-bromo-1-naphthyl chalcones. These values are correlated with various Hammett substituent constants. From the results of statistical analysis, the effect of substituents can be explained.     

High-resolution infrared spectroscopy in the 1,200-1,300 cm(-1) region and accurate theoretical estimates for the structure and ring-puckering barrier of perfluorocyclobutane

We present experimental infrared spectra and theoretical electronic structure results for the geometry, anharmonic vibrational frequencies, and accurate estimates of the magnitude and the origin of the ring-puckering barrier in C4F8. High-resolution (0.0015 cm-1) spectra of the nu12 and nu13 parallel bands of perfluorocyclobutane (c-C4F8) were recorded for the first time by expanding a 10% c-C4F8 in helium mixture in a supersonic jet. Both bands are observed to be rotationally resolved in a jet with a rotational temperature of 15 K. The nu12 mode has b2 symmetry under D2d that correlates to a2u symmetry under D4h and consequently has +/- <-- +/- ring-puckering selection rules. A rigid rotor fit of the nu12 band yields the origin at 1292.56031(2) cm-1 with B' = 0.0354137(3) cm-1 and B' ' = 0.0354363(3) cm-1. The nu13 mode is of b2 symmetry under D2d that correlates to b2g under D4h, and in this case, the ring-puckering selection rules are +/- <-- -/+ . Rotational transitions from the ground and first excited torsional states will be separated by the torsional splitting in the ground and excited vibrational states, and indeed, we observe a splitting of each transition into strong and weak intensity components with a separation of approximately 0.0018 cm-1. The strong and weak sets of transitions were fit separately again using a rigid rotor model to give nu13(strong) = 1240.34858(4) cm-1, B' = 0.0354192(7) cm-1, and B' ' = 0.0354355(7) cm-1 and nu13(weak) = 1240.34674(5) cm-1, B' = 0.0354188(9) cm-1, and B' ' = 0.0354360(7) cm-1. High-level electronic structure calculations at the MP2 and CCSD(T) levels of theory with the family of correlation consistent basis sets of quadruple-zeta quality, developed by Dunning and co-workers, yield best estimates for the vibrationally averaged structural parameters r(C-C) = 1.568 A, r(C-F)alpha = 1.340 A, r(C-F)beta = 1.329 A, alpha(F-C-F) = 110.3 degrees , thetaz(C-C-C) = 89.1 degrees , and delta(C-C-C-C) = 14.6 degrees and rotational constants of A = B = 0.03543 cm-1 and C = 0.02898 cm-1, the latter within 0.00002 cm-1 from the experimentally determined values. Anharmonic vibrational frequencies computed using higher energy derivatives at the MP2 level of theory are all within <27 cm-1 (in most cases <5 cm-1) from the experimentally measured fundamentals. Our best estimate for the ring-puckering barrier at the CCSD(T)/CBS (complete basis set) limit is 132 cm-1. Analysis of the C4F8 electron density suggests that the puckering barrier arises principally from the sigmaCC-->sigmaCF hyperconjugative interactions that are more strongly stabilizing in the puckered than in the planar form. These interactions are, however, somewhat weaker in C4F8 than in C4H8, a fact that is consistent with the smaller barrier in the former (132 cm-1) with respect to the latter (498 cm-1).     

Raman spectrum of [Ru(CNBu t)(CO)(eta2-C6H4-2-CHO)(PPh3)2][BF4].2CDCl3 shows that the crystallographically determined bifurcated hydrogen-bonding interaction Cl3CD...F2BF2- is an example of a blue-shifting hydrogen bond

Raman data suggest that a crystallographically determined Cl3CD...F2BF2- interaction in the solid-state structure of [Ru(CNBut)(CO)(eta2-C6H4-2-CHO)(PPh3)2][BF4].2CDCl3 is an example of a blue-shifting bifurcated hydrogen bond. The nu(C-D) band blue-shifts 5 cm-1 to 2269 cm-1 compared to 2264 cm-1 for CDCl3 in the gas phase and 20 cm-1 from frozen CDCl3 at 2249 cm-1. A conventional interpretation of these band shifts would suggest that the CCl2 fragment of DCCl3 is a stronger hydrogen-bond acceptor than the BF2 fragment of a BF4- group.     

The role of hydrogen bonding on the h-atom-donating abilities of catechols and naphthalene diols and on a previously overlooked aspect of their infrared spectra

Catechols and 1,8-naphthalene diols contain one "free" hydroxyl and one intramolecularly H-bonded hydroxyl group. The "free" hydroxyls are strong hydrogen-bond donors (HBDs) with alpha2H values (Abraham et al. J. Chem. Soc., Perkin Trans. 2 1989, 699) ranging from 0.685 to 0.775, indicating that these compounds have similar HBD properties to those of strongly acidic phenols such as 4-chlorophenol (alpha2H = 0.670) and 3, 5-dichlorophenol (alpha2H = 0.774). Kinetic effects on H-atom abstractions from the diols in HB acceptor (HBA) solvents can be quantitatively accounted for over at least 50% of the available range of solvent HBA activities (as measured by their beta2H values; see Abraham et al. J. Chem. Soc. Perkin Trans. 2 1990, 521) on the basis of a single reactive OH group, the "free" OH. This free OH group is an outstanding H-atom donor in poor HBA solvents; e.g., in hexane rate constants for reaction with the DPPH* radical are 2.1 x 104 M-1 s-1 for 3,5-di-tert-butyl catechol and 2 x 106 M-1 s-1 for 4-methoxy-1,8-naphthalene diol, but only 7.4 x 103 M-1 s-1 for alpha-tocopherol (vitamin E). The diols are much more reactive than simple phenols because the O-H bond dissociation enthalpy of the "free" OH group is weakened by 5-9 kcal/mol by the intramolecular H-bond. The IR spectra of all the diols in CCl4 show two fairly sharp O-H stretching bands of roughly equal intensity separated by 42-138 cm-1. Addition of a low concentration of DMSO, a strong HBA, causes the band due to the intramolecularly H-bonded OH group to decrease in intensity to roughly half the extent that the "free" OH band loses intensity. The latter forms an intermolecular H-bond with the DMSO, the former does not. What has been overlooked in earlier work is that as the DMSO concentration is increased the band due to the intramolecularly H-bonded OH group first broadens and then evolves into a new, lower frequency (by 19-92 cm-1) band. The magnitude of the shift in the frequency of the intramolecular OH band caused by H-bonding of HBAs to the "free" OH group, Deltanu, increases linearly as the HBA activity of the additive increases, e.g., for 3,5-di-tert-butylcatechol, Deltanu/cm-1 = 33.8 beta2H (R 2 = 0.986). This may provide a new and simple method for determining beta2H values.     

A Versatile Route to Porous Solids: Organic–Inorganic Hybrid Materials Assembled through Hydrogen Bonds

Square-planar and octahedral complexes of Ni^II and Pt^II link through head-to-head hydrogen bonds to form porous frameworks with large cavities that are suitable for inclusion of guest molecules. A series of four different complexes with pyridine-based ligands (in the center of the picture) are described, which contain either counterions or small molecules in channels. A=hydrogen-bond acceptor, D=hydrogen-bond donor, M=metal ion.     

Structures of transient species in the photochromic reaction of 1′,3′,3′-trimethylspiro[2H-1-benzopyran-2,2′-indoline]: Time-resolved resonance Raman study of isotopically substituted analogues

Time-resolved resonance Raman spectra of seven kinds of isotopically substituted analogues of 1′,3′,3′-trimethylspiro[2H-1-benzopyran-2,2′-indoline] in the photomerocyanine form have disclosed that only the vibrations of the cleaved benzopyran part are resonance enhanced significantly in cyclohexane and in acetonitrile solutions with 460-390 nm probe light. Dramatic changes in the resonance Raman spectra of the photomerocyanine on going from non-hydrogen-bond donor solvents to hydrogen-bond donor solvents can be interpreted as being due to changes in the relative contribution of ortho-quinoidal and zwitterionic forms in the resonance hybrid structure of the photomerocyanine: in cyclohexane and in acetonitrile the contribution of the ortho-quinoidal form is substantial, while in methanol the zwitterionic form is stabilized by hydrogen bonding with the solvent and the photomerocyanine takes an almost zwitterionic structure.     

Donor-acceptor phthalocyanine nanoaggregates

A novel donor-acceptor bisphthalocyanine (bis-Pc, 1) in which two different Pc units (Zn(II)-Pc and Ni(II)-Pc) are linked via vinylene spacers to the pseudopara positions of a central [2.2]paracyclophane moiety is described. The synthesis of 1 is achieved by two successive Heck reactions of pseudopara-divinyl[2.2]paracyclophane 9 with, sequentially, a zinc(II)- and a nickel(II)-iodophthalocyanine (4 and 5, respectively). The self-assembly ability of 1, which is the result of the complementary donor-acceptor character of its phthalocyanine units, has been assessed by a variety of techniques. It is revealed that 1 forms one-dimensional aggregates of nanometer-sized dimension, whereas equimolar mixtures of the donor and acceptor Pc subunits 2 and 3, although strongly interacting, do not give large arrays. The aggregates of 1 represent a novel type of supramolecular polymers based mainly upon donor-acceptor interactions.     

Benzotriazole complexes with amines and phenol: cooperativity mediated by induction effects in the crystal state

[structure: see text] Benzotriazole forms complexes of different stoichiometries with amines and phenols. Four of them have been characterized by single-crystal X-ray diffraction. The trends of donor-acceptor hydrogen-bond distances between corresponding molecular entities in the different complexes are related to induction-mediated cooperativity effects.     

Vibrational studies on the selective solvation of Na+ and ClO3- ions in dimethylformamide-formamide mixture

Raman and infrared spectra of sodium chlorate in binary mixture of N,N-dimethylformamide (DMF) and formamide (FA) were obtained. The addition of FA to the NaClO3-DMF system allow us to observe a new band at 1709 cm-1. This has been possible since the large dissociation of Na+ and ClO3- ions produced by the addition of FA helps to observe the coordination effect of DMF on the Na+ ions, in full agreement with the Gutmann donor number of this later. Quantitative measurements performed in the CO stretching region in the binary mixture give a solvation number value for the sodium cation equal at 3 in full agreement with others authors. In the NH stretching region of FA, the arising of the 3580 cm-1 band is assigned to FA-ClO3- interactions via hydrogen bonding. In addition, our results show that the solvation number of the sodium cation remain constant in all concentration range studied. Such fact suggests that mixture of solvents with considerable differences in the donor-acceptor characters can be used to prepare electrolyte solutions where the ion pairs formation seems uncertain.     

Application of a novel linear/exponential hybrid force field scaling scheme to the longitudinal Raman active mode of polyyne

The properties of an infinite carbon chain (polyyne), an allotropic form of elemental carbon, are of importance in materials science as well as astronomy. The Raman active longitudinal optical (LO) frequencies are calculated with first-principles methods for oligoynes and polyyne and compared with experiments. Since traditional force constant scaling schemes fail in this case, we introduced a linear/exponential scaling scheme based on the exponential behavior of the carbon-carbon bond stretching force constant couplings in quasi-one-dimensional conjugated chains. The LO Raman active frequency is predicted at 1870-1877 cm-1. Our results provides further evidence for the assignment of the characteristic Raman peaks near 1850 cm-1 of the recently discovered long linear carbon chains encapsulated inside multiwalled or double-walled carbon nanotubes.     

Conformational stability from variable temperature FT-IR spectra of krypton solutions, r0 structural parameters, vibrational assignment, and ab initio calculations of 4-fluoro-1-butene

Variable temperature (-115 to -155 degrees C) studies of the infrared spectra (3200-400 cm-1) of 4-fluoro-1-butene, CH2=CHCH2CH2F, dissolved in liquid krypton have been carried out. The infrared spectra of the gas and solid as well as the Raman spectra of the gas, liquid, and solid have also been recorded from 3200 to 100 cm-1. From these data, an enthalpy difference of 72 +/- 5 cm-1 (0.86 +/- 0.06 kJ x mol-1) has been determined between the most stable skew-gauche II conformer (the first designation refers to the position of the CH2F group relative to the double bond, and the second designation refers to the relative positions of the fluorine atom to the C-C(=C) bond) and the second most stable skew-trans form. The third most stable conformer is the skew-gauche I with an enthalpy difference of 100 +/- 7 cm-1 (1.20 +/- 0.08 kJ x mol-1) to the most stable form. Larger enthalpy values of 251 +/- 12 cm-1 (3.00 +/- 0.14 kJ x mol-1) and 268 +/- 17 cm-1 (3.21 +/- 0.20 kJ x mol-1) were obtained for the cis-trans and cis-gauche conformers, respectively. From these data and the relative statistical weights of one for the cis-trans conformer and two for all other forms, the following conformer percentages are calculated at 298 K: 36.4 +/- 0.9% skew-gauche II, 25.7 +/- 0.1% skew-trans, 22.5 +/- 0.2% skew-gauche I, 10.0 +/- 0.6% cis-gauche, and 5.4 +/- 0.2% cis-trans. The potential surface describing the conformational interchange has been analyzed and the corresponding two-dimensional Fourier coefficients were obtained. Nearly complete vibrational assignments for the three most stable conformers are proposed and some fundamentals for the cis-trans and the cis-gauche conformers have been identified. The structural parameters, dipole moments, conformational stability, vibrational frequencies, infrared, and Raman intensities have been predicted from ab initio calculations and compared to the experimental values when applicable. The adjusted r0 structural parameters have been determined by combining the ab initio predicted parameters with previously reported rotational constants from the microwave data. These experimental and theoretical results are compared to the corresponding quantities of some similar molecules.     

利用真空紫外脉冲场电离-光电子方法研究三氯乙烯阳离子振动光谱

The vacuum ultraviolet（VUV）pulsed field ionization-photoelectron（ PFI-PE）spectrum for trichloroethene（ClCH=CCl2）has been measured in the energy range of 76400-79650 cm-1 . The vibrational bands resolved in the VUV-PFI-PE spectrum are assigned based on ab initio vibrational frequencies and calculated Franck-Condon factors for the ionization transitions,yielding eleven vibrational frequencies for ClCH=CCl2+:v1+=148 cm-1,v2+= 80 cm-1,v3+=286 cm-1,v4+=402 cm-1,v5+= 472 cm-1,v6+=660 cm-1,v7+=875 cm-1,v8+=990 cm-1,v9+=1038 cm-1,v10+=1267 cm-1,and v11+=1408 cm-1. These measurements along with the frequency v12+=3073 cm-1 determined in the recent VUV-infrared photo-induced ionization study have provided the complete set of twelve experimental vibrational frequencies for ClCH = CCl2+ in its ground electronic state. On the basis of the spectral simulation of the origin VUV-PFI-PE vibrational band,we have determined the IE（ClCH=CCl2）to be（76441.7±2.0）cm-1（（9.4776±0.0002）eV）.     

Weak donor-acceptor complexes of o-quinone diazides with phenol-formaldehyde oligomers

Summary It has been shown by low-temperature photolysis and ESR that mixtures of o-naphthoquinone diazides with phenol-formaldehyde oligomers in solutions and dry films form weak donor-acceptor complexes in which the intramolecular photoreduction of the o-naphthoquinone diazide can take place.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1255–1259, June, 1981.