13C n.m.r. studies of some phenanthrene and fluorene derivatives

The ¹H and ¹³C spectra of fluorene, fluorenone, phenanthrene and their 4-methyl and 4,5-dimethyl derivatives have been examined. To complete the analyses for fluorenone and 4-methylfluorenone, ¹H spectra were recorded at 270 MHz. The results from the ¹H spectra permitted unequivocal assignments for the protonated aryl carbons by selective proton decoupling. A consistent set of assignments for the quaternary carbons was obtained through consideration of the dominant relaxation processes operative at these centres. This series of compounds was examined to investigate the shielding effects produced by the close approach of methyl groups separated by five bonds for comparison with the contrasting trends found for methyl carbons separated by three and four bonds. The results indicate that the relative orientation of the methyl groups is an extremely critical factor governing their shieldings and those of neighboring centres.     

Dynamic NMR: A new procedure for the estimation of mixing times in the 2D EXSY experiments. A four-site exchange system studied by 1D and 2D EXSY spectroscopy

A procedure for the estimation of the mixing time between the last two 90° pulses in the classic three-pulse sequence NOESY/EXSY is proposed and tested and some considerations for the treatment of the two-dimensional (2D) ¹H NMR exchange spectra are given. The rate constants are thus obtained with reasonable precision. This procedure was followed to obtain the 2D spectra of the model compound α-[bis(dimethylamino)methylene]-4-nitrophenylacetonitrile, which represents a four-site exchange system. The barriers to restricted rotations found in this compound were also determined from one-dimensional (1D) ¹H NMR spectra, which were processed with the iterative complete lineshape analysis (CLSA) method. The double-fit approach was incorporated in the CLSA method. It is shown that the results from the 2D dynamic NMR spectral studies corroborate those obtained by the CLSA double-fit method.     

Vibrational spectra of 2-biphenylmethanol. Spectrum simulation and molecular structure

The vibrational spectra of a solid crystalline sample of 2-biphenylmethanol have been measured at room temperature. The IR absorption spectra were recorded in the range 400 cm^–1–3600 cm^–1; Raman spectra were measured in the range 10 cm^–1–1640 cm^–1. The direct mechanical and optoelectronic problems were solved using the fragment method realized as Lev-100 software; the intensity distribution in the IR spectrum of 2-biphenylmethanol was obtained by the same method. The experimental Raman and IR absorption spectra were interpreted by analyzing the calculated data on the frequencies and forms of normal vibrations and their intensities in the IR spectra. IR absorption spectra were simulated for several models of 2-biphenylmethanol conformers that differ in the mutual orientation of fragments. Based on the results of simulation and comparison of the calculated and experimental spectra of conformers we suggested a model for the conformer realized in the solid phase under normal conditions.Original Russian Text Copyright © 2004 by L. M. Babkov, J. Baran, N. A. Davydova, J. I. Kukielskii, and S. V. TrukhachevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 624–631, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Inclusion of relativistic effects into ZDO methods. II. Solavation of metal complexes

The quasirelativistic CNDO /1 method has been in investigating the geometry, electronic structure, and redox stability of metal complexes. The systems of [Co(NH₃)₆]^q and [MCl₄]^q, M being Ni, Pd, and Pt, have been studied. A modified Germer model of solvation has been implemented into the method. This yields reliable results on the redox stability of complexes in aqueous solutions. The calculated excitation energies resemble the electronic spectra of [MCl₄]^2? complexes.     

Oligosaccharide Analogues of Polysaccharides. Part 26

The anthraquinone derivatives T‐x‐x ( x = 2, 4, and 8), possessing two cellobiosyl, cellotetraosyl, and cellooctaosyl chains, respectively, C‐glycosidically bonded at C(1) and C(8) were synthesised as potential mimics of cellulose I. The anthraquinone template enforces a parallel orientation of the cellodextrin chains at a distance corresponding to the one between the crystallographically independent chains of cellulose I, and the ethynyl and buta‐1,3‐diynyl linker units ensure an appropriate phase shift between them. The H‐bonding of the T‐x‐x mimics was analysed and compared to the one of the mono‐chained analogues T‐x and of the known cellulose II mimics N‐x‐x and N‐x where one or two cellodextrin chains are O‐glycosidically bonded to naphthalene‐1,8‐diethanol, or to naphthalene‐1‐ethanol. The OH signals of T‐x and T‐x‐x in solution in (D₆)DMSO were assigned on the basis of DQFCOSY, HSQC, and TOCSY (only of T‐4, T‐4‐4 , and T‐8‐8 ) spectra and on a comparison with the spectra of N‐x and N‐x‐x. Hydrogen bonding was analysed on the basis of the chemical shift of OH groups and its temperature dependence, coupling constants, SIMPLE ¹H‐NMR experiments, and ROESY spectra. T‐4‐4 and T‐8‐8 in (D₆)DMSO appear to adopt a V‐shape arrangement of the cellosyl chains, avoiding inter‐chain H‐bond interactions. The well‐resolved solid‐state CP/MAS ¹³C‐NMR spectra of the mono‐chained T‐x ( x = 1, 2, 4, and 8) show that only T‐8 is a close mimic of cellulose II. While the solid‐state CP/MAS ¹³C‐NMR spectrum of the C₁‐symmetric diglucoside T‐1‐1 is well‐resolved, the spectra of T‐2‐2 and T‐4‐4 show broad signals, and that of T‐8‐8 is rather well resolved. The spectrum of T‐8‐8 resembles that of cellulose I_β. A comparison of the X‐ray powder‐diffraction spectra of T‐8‐8 and T‐8 with those of celluloses confirms that T‐8‐8 is a H‐bond mimic of cellulose I and T‐8 one of cellulose II. Surprisingly, there is little difference between the CP/MAS ¹³C‐NMR spectra of the acetyl protected mono‐chained C‐glycosylated anthraquinone derivatives A‐x and the double‐chained A‐x‐x ( x = 2, 4, and 8). The spectra of A‐4 and A‐4‐4 resemble strongly the one of cellulose triacetate I ( CTA I ). The (less well‐resolved) spectra of the cellooctaosides A‐8 and A‐8‐8 , however, resemble the one of CTA II . The similarity between the solid‐state CP/MAS ¹³C‐NMR spectra of A‐4 and A‐4‐4 to the one of CTA I , and of A‐8 and A‐8‐8 to the one of CTA II is opposite to the observations in the acetylated cellodextrin series. The mono‐chained A‐x cellulose triacetate mimics 21 ( A‐2 ), 32 ( A‐4 ), and 55 ( A‐8 ) were synthesised by Sonogashira coupling of the cellooligosyl‐ethynes 15, 28 , and 50 , followed by selective deacetylation. Complete deacetylation provided the corresponding T‐x mimics. The double‐chained A‐x‐x mimics 24 ( A‐2‐2 ), 35 ( A‐4‐4 ), and 58 ( A‐8‐8 ) were prepared from A‐x by triflation and Sonogashira coupling with the cellosyl‐buta‐1,3‐diynes 19, 31 , and 53 . Their deacetylation provided the corresponding T‐x‐x mimics 25, 36 , and 59 . The cellooligosyl‐ethynes and cellooligosyl‐buta‐1,3‐diynes required for the Sonogashira coupling were prepared by stepwise glycosylation of the partially O‐benzylated β‐cellobiosyl‐ethyne and β‐cellobiosyl‐buta‐1,3‐diyne 13 and 17 , respectively, with the cellobiosyl donor 2 and the cellohexaosyl donor 47 .     

Facile Synthesis of 4-Oxo-4H-quinolizine-2-carboxamide Derivatives

A facile synthetic method for the construction of 2-substituted-4-oxo-4H-quinolizine-based core structure has been successfully developed. The synthesis made use of a one-pot Stobbe condensation followed by cyclization starting from the commercially available 2-pyridinecarbaldehyde. The structure of the formed 4-oxo-4H-quinolizine-2-carboxylate was fully confirmed by mass spectra, ¹H NMR and ¹³C NMR, correlation spectrography, heteronuclear multiple bond correlation, and heteronuclear single quantum coherence (HSQC) spectra. The ethyl carboxylate moiety was then further functionalized via direct aminolysis by a range of amines to afford the corresponding 4-oxo-4H-quinolizine-2-carboxamides 4a–i in moderate to good yields.     

The13C NMR spectra of some polychlorinated dibenzo-p-dioxins. A calculation of13C chemical shifts

The¹³C NMR spectra of a number of polychiorinated dibenzo-p-dioxins (PCDD) were measured. These and previously known spectra were used for the development of a method for calculation of¹³C NMR spectra of chloroaromatics in the framework of a two-particle increment scheme for carbon chemical shifts. The scheme one allows to calculate¹³C chemical shifts for all 75 PCDD.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 760–761, April, 1994.     

A convenient synthesis and structural analysis of novel 4,5,6,7-tetrahydro-1H-indazoles

A new series of t-4-aryl-3,c-6-dihydroxy-6-methyl-4,5,6,7-tetrahydro-1H-indazole-r-5-carboxylic acid isopropyl esters has been synthesized by adopting a conventional method from cyclic β-keto esters. ¹H, ¹³C NMR, and IR spectra for all the compounds were investigated. HMBC, HSQC, COSY, and NOESY spectra of the representative compounds were studied. The stereochemistry of a six-membered ring of the fused indazoles resembled that of keto esters. From the HMBC correlations the indazole structure was confirmed as 1H-indazole.     

Schwingungsspektren,kraftkonstanten und Elektrotransparenzen isoelektronischer tetramethylverbindungen der III., IV. und V. Hauptgruppe

The vibrational spectra of the following compounds were measured: X⁺AlMe⁻₄; X⁺GaMe⁻₄ and X⁺InMe⁻₄ (with X = Na, K, Me₄P⁺, Me₄As⁺ or Me₄Sb⁺). For the purpose of comparison the spectra of compounds of group IV and V elements were taken from the literature or measured a second time. With a new procedure for determination of force-constants a set of comparable force-constants for the tetramethyl compounds of the elements Al, Si, P/Ga, Ge, As/In, Sn, Sb was obtained.     

Coherent amplification in fluorescent dye solutions. II. The inverse pre-resonance Raman spectrum of rhodamine 6G

Inverse pre-resonance Raman spectra of rhodamine 6G in solution in methanol have been recorded over the concentration range 10^?1 to 10^?4 mol ?^?1. The solute and solvent transitions are found to display perfectly normal lorentzian profiles over the whole of this concentration range. Intensities and depolarization ratios of the pre-resonance Raman features are recorded. It is shown that the spectra arise from monomeric rhodamine 6G molecules in the singlet electronic ground state and the relative merits of the CARS and inverse Raman methods for recording resonance Raman spectra are discussed.     

Vibrational spectral studies of solutions at elevated temperatures and pressures. X. Raman spectral study of aqueous cadmium bromide solutions at 25 and 200°C

The Raman spectra of cadmium bromide solutions with bromide to cadmium mole ratios varying from 1.0 to 9.74 were studied at 200°C. Factor analysis revealed that three complexes contributed to the spectra. From a comparison with previous results at 25°C these species were identified as CdBr₂, CdBr ₃ ^– , and CdBr ₄ ^2– cadmium existed as the tetrabromo complex, CdBr ₄ ^2– , at mole ratios greater than 5.99. A formation constant of 7±2 was determined for CdBr ₄ ^2– at 200°C. No evidence of Cd(H₂O) ₆ ²⁺ or CdBr⁺ was found, although electroneutrality dictates that one or both of these species must exist at low mole ratios.     

Parametric method for calculating the vibronic spectra of complex molecules. Diphenylpolyenes

The absorption and fluorescence spectra of diphenylpolyenes (diphenylbutadiene, diphenylhexatriene, diphenyloctatetraene, and 1,6-di(4′-methylphenyl)-1,3,5-hexatriene) are calculated by a recently proposed parametric method using the fragmentation approach for designing molecular models. The parameters of the^H>C=molecular fragment (derivatives of the Coulomb and resonance integrals with respect to internal coordinates in the HAO basis set) obtained in calculation for polyenes were transferred to the molecular models of diphenylpolyenes without changes (∂H_e/∂q⁽⁰⁾=0.055 and ∂²H_e/∂q _k ⁽⁰⁾ ∂q _l ⁽⁰⁾ =0.1 au). The theoretical spectra are sufficiently adequate to quantitatively and qualitatively reproduce the main features of the vibrational structure of the experimental absorption and fluorescence spectra, and the parameters of the models of the potential surfaces of the excited states of diphenylpolyenes are consistent with the previous estimations. It is shown that this method allows predictive calculations of the vibronic spectra of complex molecules and the developed parametrization posesses all needed properties: locality, transferability, invariance to minor changes in electron density, ranking according to magnitude, small number of parameters for molecular fragments, etc. K. A. Timiryazev Moscow Agricultural Academy. Translated fromZhurnal Struktumoi Khimii, Vol. 37, No. 6, pp. 1040–1049, November–December, 1996. Translated by I. Izvekova     

Vibrational spectra and infrared dichroism of tetraphenyl-silane,Ph4Si. II.

Vibrational spectra of Ph₄Si have been studied from 600 to 20 cm^?1 in solution, in the melt and in the crystalline state. The assignments proposed for the substituent sensitive benzene ring vibrations, for the skeletal bending modes and ring librations have been supported by polarized IR and Raman measurements. The crystal spectra are interpreted on the basis of the S₄ site symmetry of the molecules in the crystal. Two skeletal bending and four ring librational modes are supposed to appear below 120 cm^?1, in the range of the lattice vibrations.     

Vibrational states of chlorophyll and related compound molecules. Metal complexes of octaethylchlorin

Fine-structure fluorescence spectra and i.r. spectra of the model compound chlorophyll-Zn-octaethylchlorin (Zn OEC), and its three deuterated derivatives at meso-positions and Zn OEC-¹⁵N₄ have been obtained. Polarization measurements for individual zero-phonon lines show that in the vibronic spectra of the above compounds the totally symmetric vibrations are mainly active. A joint analysis of the experimental data and calculation results of normal vibrations has served as a basis for the interpretation of the spectra obtained as well as resonance Raman spectra. It is pointed out that the vibrations of ethyl substituents largely form a vibrational structure of the vibronic Zn OEC spectrum. An assignment of some lines in a fine-structure spectrum of chlorophyll a is discussed.     

Multiple beta spectrum analysis based on spectrum fitting

A method of separating beta spectra into each radionuclide spectrum was proposed in this study. Based on mathematical curve fits, the spectrum of each radionuclide was defined by using the maximum energy information and process to separate specific spectra from the whole spectrum. Information on ³²P, ⁹⁰Y, and ¹⁰⁶Rh radionuclides from the International Commission on Radiation Units and Measurements was used for applying the proposed method. A relative error of less than 2% was achieved with the application of the method.     

Rhenium. Part XIX. A new isothiocyanato complex of quadrivalent rhenium

Summary Reaction between K₂[ReI₆] and KSCN in boiling MeOH or in the melt gave [Re(NCS)₆]^2– and a weakly paramagnetic species, isolated as its Cs salt. Tl, Me₄N and other salts of this species have been isolated from the reaction medium of from the Cs salt by metathesis. On the basis of magnetic susceptibility and i.r. spectra the new complex has been formulated as [Re₂(NCS)₁₂]^4– containing metalmetal bond and no bridging thiocyanate. The Me₄N salt has also been isolated by bioling aqueous solutions of HReO₄ and HSCN and then adding Me₄NCL. A pyridinium salt, formulated as (pyH)₄[Re₂(NCS)₁₂], has been obtained by boiling [ReO₂py₄]NCS with aqueous HSCN. The two complex species [Re(NCS)₆]^2– and [Re₂(NCS)₁₂]^4– show distinctly different magnetic moment and electronic spectra.     

Photoionization of excited molecular states. H2 C 1Πu

We present photoelectron spectra for H₂ in the excited C ¹Π_u, υ = 0–4.J = 1 levels prepared by multiphoton excitation. In accordance with the Franck-Condon principle, the H₂⁺ vibrational state distribution is dominated by Δυ = 0 transitions from the C ¹Π_u state, illustrating a useful method for preparing vibrationally state-selected molecular ions. Equally important observed systematic departures from Franck-Condon factors, which provide detailed information on excited-state photoionization dynamics of molecules.     

Porphyrins. 24. Identification of isomeric monoesters of natural porphyrins by PMR spectroscopy

The monomethyl esters of mono(dimethylamides) and the bisdimethylamides of mesoporphyrin-IX, mesoporphyrin-III, and mesoporphyrin-XIII have been obtained, together with their zinc complexes. A relationship has been found between the chemical shifts of the signals for CONMe₂ in the PMR spectra and the positions of the substituents in the porphyrin ring, enabling a correct assignment to be made for the first time of these signals to the groups in positions 13² and 17² of the porphyrin ring, to establish the structures of the isomeric monomethyl esters of mesoporphyrin-IX, and to develop a method of identifying monoesters of natural porphyrins by converting them into the monoesters of the mono(dimethylamides) of mesoporphyrin-IX, followed by examination of their PMR spectra.For Communication 23, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 780–786, June 1988.     

Azabrendanes. II. Chemo-, regio- and stereoselective transformation of 3-oxatricyclo[3.2.1.02,4]octane-endo-6-carbonitrile in reaction with lithium aluminum hydride

The reduction of 3-oxatricyclo[3.2.1.0^2,4]octane-endo-6-carbonitrile by lithium aluminum hydride is completed by the formation of exo-2-hydroxy-4-azatricyclo[4.2.1.0^3,7]nonane with the structure confirmed (1) by the analysis of ¹H, ¹³C, ¹⁴N, and ¹⁷O NMR spectra and the two-dimensional spectra (COSY-experiment); (2) by comparison with ¹H and ¹³C NMR spectra of the corresponding oxygen analog of heterobrendane; (3) by the calculation of the vicinal constants for the spin-spin interaction in the molecules of both analogs by the MMX program; and (4) by transformation into N-(p-bromophenylsulfonyl)-exo-2-hydroxy-4-azatricyclo[4.2.1.0^3,7]nonane prepared by an alternative synthesis, viz., epoxidation of N-(p-bromophenylsulfonyl)bicyclo-[2.2.1]hept-2-en-endo-5-methylamine. The reduction of 3-oxatricyclo [3.2.1.0^2,4]octane-exo-6-carbonitrile affords the epoxide, 3-oxatricyclo[3.2.1.0^2,4]octane-exo-6-methylamine. Different behaviors of stereoisomers are discussed; analysis of the coefficients of the atomic orbitals in the MO LCAO equation (AM1 method) has been made, and the strengths of the C(SINGLE BOND)O bonds in the epoxy ring has been analyzed. © 1997 John Wiley & Sons, Inc.