Accurate potentials for the X1Σ+g states of H2 and D2 molecules

Starting from the spectroscopic constants, the electronic potential for the ground state of H₂ and D₂ molecules has been calculated. Numerical integration of the radial wave equation gives accurate self-consistent eigenvalues (mean deviation of about 0.05 cm⁻¹). A comparison between different potentials is reported. New revised spectroscopic constants are calculated.     

Theoretical study of spectroscopic constants and molecular properties of rare‐gas diatomic cations

Ab initio and density functional methods are applied to study the spectroscopic constants and molecular properties of the diatomic cations He, Ne, Ar, HeNe⁺, and HeAr⁺. Among these cations, HeAr⁺ is found to be weakly bound and its spectroscopic constants are calculated using the Lennard‐Jones potential. The other molecules that are strongly bound obey Morse potential, and their spectroscopic constants are calculated accordingly. The calculated spectroscopic constants agree very well with the theoretical and experimental values wherever available. Most of the spectroscopic constants and molecular properties are reported for the first time. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Coupled cluster study of structural properties of RgI and RgI<Superscript>−</Superscript> (Rg = He,Ne, Ar) weakly bound molecules

Structural properties, spectroscopic constants and the interaction between rare-gas atom and open and closed-shell iodine atom of weakly bound van der Waals molecules have been studied in details using CCSD(T) method. The Lennard-Jones potential is used to study the interaction and spectroscopic constants of the neutral and anionic systems. The spectroscopic constants and the interacting force between the two atoms of RgI and RgI⁻ (Rg = He, Ne and Ar) have been calculated using our method developed recently for the weakly bound molecule in Lennard-Jones potential. The results have been compared with the theoretical and experimental data wherever available. Most of the spectroscopic constants are first reported.     

Derivatives of pyrazinecarboxylic acid: 1H, 13C and 15N NMR spectroscopic investigations

NMR spectroscopic studies are undertaken with derivatives of 2‐pyrazinecarboxylic acid. Complete and unambiguous assignment of chemical shifts (¹H, ¹³C, ¹⁵N) and coupling constants (¹H,¹H; ¹³C,¹H; ¹⁵N,¹H) is achieved by combined application of various 1D and 2D NMR spectroscopic techniques. Unequivocal mapping of ¹³C,¹H spin coupling constants is accomplished by 2D (δ,J) long‐range INEPT spectra with selective excitation. Phenomena such as the tautomerism of 3‐hydroxy‐2‐pyrazinecarboxylic acid are discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Spectroscopic properties of molecular anions of astrophysical and laboratory interest

Spectroscopic constants and molecular properties of the selected six diatomic anions of astrophysical and laboratory interest namely, FO⁻, CCl⁻, NS⁻, ClO⁻, ClF⁻ and AlS⁻ in their ground state have been studied in detail using hybrid HF/DF B3LYP method. The effect of basis set on spectroscopic properties has been studied with systematic improvement of basis set from aug-cc-pVDZ to aug-cc-pV5Z. The values of the spectroscopic constants and molecular properties obtained with these basis sets have been extrapolated to the complete basis set (CBS) limit. The spectroscopic properties calculated with the aug-cc-pV5Z basis set are very close to those at the CBS limit and these values agree very well with the theoretical and experimental results wherever available. Many of the spectroscopic constants and molecular properties of these anions are new and in particular those for ClF⁻ and AlS⁻ are first reported.     

Accurate spectroscopic constants of the lowest three electronic states in halonitrenes with multireference configuration interaction

Internally contracted multireference configuration interaction (icMRCI) calculations of the ground state (X³Σ⁻), the first excited state (a¹Δ) as well as the second excited state (b¹Σ⁺) have been performed for a series of halogenated nitrenes NXs (X = Cl, Br, and I). Accurate spectroscopic constants of these lowest three electronic states of each NX were obtained in this work using MRCI methods with aug‐cc‐pVXZ (X = T, Q, 5) basis sets and complete basis set (CBS) limit. In addition, various corrections, including the Davidson correction, scalar relativistic effect, core‐valence correlation, and spin‐orbit coupling effect, have been studied in calculating spectroscopic constants, especially for heavy‐atom nitrenes. Comparisons have been made with previous computational and experimental results where available. The icMRCI + Q calculations presented in this work provide a comprehensive series of results at a consistent high level of theory for all of the halogenated nitrenes.     

Spectroscopic constants and molecular properties of CN−, SiH−, PO−, SO−, SF−, and SiS−: Density functional study

Spectroscopic constants and molecular properties of selected diatomic anions namely CN^?, SiH^?, PO^?, SO^?, SF^?, and SiS^? in their ground states have been studied in detail using the hybrid HF/DF B3LYP method. The consistency of the calculated values has been verified with four different basis sets, with improved quality. The spectroscopic constants and molecular properties calculated with the aug‐cc‐pVTZ basis set agree very well with the experimental and theoretical values wherever available. Most of the spectroscopic constants and molecular properties of the selected diatomic anions, particularly the spectroscopic constants and molecular properties of SO^? and SiS^? are reported for the first time. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Investigation of the solid-state conductivity and the potentiometric stability constant relationships of new amino acid-Schiff bases and their complexes

Cu^II, Ni^II and Co^II complexes of new tridentate amino acid-Schiff bases derived from furfural and DL-alanine, DL-valine and DL-phenylalanine were prepared and characterized by analytical, spectroscopic, (i.r., u.v.–vis., ¹H-n.m.r and ¹³C-n.m.r) techniques, molar conductivity, magnetic and thermal measurements. Protonation constants of the Schiff bases and stability constants of the complexes have been determined potentiometrically in water. Solid-state conductivities of the synthesized substances were measured using the four-probe technique on a compressed pellet at room temperature.     

The determination of electronic ground and singlet state wavefunctions of BH

An extensive series of CI calculations have been carried out for the BH molecule using averaged natural orbitals. It is shown that energy profiles yielding accurate spectroscopic constants are obtainable for several states simultaneously. Energy values and spectroscopic data for the five lowest singlet states X ¹Σ⁺, A ¹Π, C ¹Δ, B ¹Σ⁺, and C ¹σ⁺have been calculated.     

Heterocyclic analogs of xanthiones: 5,6‐fused 3‐methyl‐1‐phenylpyrano[2,3‐c]pyrazol‐4(1H) thiones—synthesis and NMR (1H, 13C, 15N) data

Various [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐thiones were synthesized in high yields by treatment of the corresponding [5,6]pyrano[2,3‐c]pyrazol‐4(1H)‐ones with Lawesson's reagent. Detailed NMR spectroscopic studies were undertaken of the title compounds. Complete and unambiguous assignment of chemical shifts (¹H, ¹³C, ¹⁵N) and coupling constants (¹H,¹H; ¹³C,¹H) was achieved by the combined application of various one‐ and two‐dimensional (1D and 2D) NMR spectroscopic techniques. Unequivocal mapping of most ¹³C,¹H spin coupling constants is accomplished by 2D (δ, J) long‐range INEPT spectra with selective excitation. Copyright © 2010 John Wiley & Sons, Ltd.     

A comparison between the potential energy curves for the X1Σg+ state of H2 and D2

The electronic potential for the ground state of H₂ and D₂, molecules has been calculated from spectroscopic molecular constants. Numerical integration of the radial wave equation gives accurate self-consistent values (an eigenvalue mean deviation of about 1 cm⁻¹). A comparison between different potentials is reported.     

Isolation and structure of koshikalide,a 14-membered macrolide from the marine cyanobacterium Lyngbya sp.

A 14-membered macrolide, koshikalide (1), was isolated from the marine cyanobacterium Lyngbya sp., and its planar structure was elucidated by spectroscopic analysis. The relative stereochemistry of C-11 and C-13 was elucidated by NOESY experiments and by an analysis of ¹H–¹H coupling constants. Koshikalide (1) exhibited weak cytotoxicity against HeLa S₃ cells.     

Evidence for the formation of a triple radiative exciplex between excited aqua-uranyl(VI) and thallous ion

Results from steady-state and transient photokinetic and spectroscopic measurements, show the formation in aqueous solution of a triple radiative exciplex between excited UO²⁺₂ and TI⁺. Rate constants of exciplex formation and deactivation are evaluated The nature of bonding and the emittive properties of this species, of probable ¹(Tl·OUO-Tl)⁴⁺ structure, are discussed.     

A study of the collisional quenching of O(21D2) by the noble gases employing time-resolved attenuation of atomic resonance radiation in the vacuum ultraviolet

Electronically excited oxygen atoms O(2¹D₂) have been generated by the pulsed irradiation of ozone in the Hartley-band continuum and monitored photoelectrically in absorption by time-resolved attenuation of atomic resonance radiation at λ = 115.2 nm [O(3¹D₂°) → O(2¹D₂)]. Collisional quenching of the excited atom has been investigated for all the noble gases, and the first absolute values for the second-order deactivation rate constants are reported. The resulting rate data are discussed in terms of a curve-crossing mechanism based on existing spectroscopic data for the noble gas oxides. The absolute rate constants are compared with previous relative rate data for the deactivation of O(2¹D₂) by the noble gases.     

Evaluation of the CuCl+ stability constant and molar absorptivity in aqueous media

Upper and lower bound estimates of the CuCl⁺ stability constants produced by various investigations have been quantitatively examined. Our analyses, including our own ultraviolet spectroscopic investigations, indicate that the CuCl⁺ stability constant in 1 molar HClO₄ is β₁=0.70±0.23. The CuCl⁺ molar absorptivity at a wavelength of 250 nm was determined as 1860 cm²-mol^?1. Our analyses suggest the bound β ₁ ^′≤0.37 for the formation constant of MgCl⁺ at one molar ionic strength.     

Synthesis and Complexation Studies of a Convex Bis-porphyrin Tweezer—A Molecular Capsule Precursor

The synthesis and spectroscopic studies of a convex bis-porphyrin based molecular tweezer are reported. The complexation of small bidentate ligands by metallated derivatives of the bis-porphyrin host were monitored through UV–visible and ¹H NMR spectroscopy and yielded large association constants.     

The rα-structure and the 1H and 199Hg shielding anisotropies of dimethylmercury as determined in nematic and smectic liquid crystal solvents

The complete r_α-structure of dimethylmercury in the nematic ZLI 1167 liquid crystal was determined. This study confirms the earlier results, indicating that the structure is practically independent of the liquid crystal solvent, although some minor deviations exist. The Hg? C distance was found to be 207.97±0.05 pm, when the vibration corrections in the dipole-dipole coupling constants were taken into account. This is rather similar to the distances obtained with other spectroscopic methods. The anisotropies of the ¹H and ¹⁹⁹Hg chemical shifts were obtained by using a smectic liquid crystal and recording the corresponding spectra, the optical axis being parallel with or perpendicular to the external field direction. The experimental ratio-2.007±0.017 of the D∥ (HgH) and D? (HgH) coupling constants proves that the indirect contributions in these coupling constants are negligible. Shielding anisotropies of 3.70±0.3 ppm and 7325±55 ppm for ¹H and ¹⁹⁹Hg, respectively, were obtained.     

Bionectriol A, a polyketide glycoside from the fungus Bionectria sp. associated with the fungus-growing ant, Apterostigma dentigerum

A new polyketide glycoside, bionectriol A (1), was produced by a fungal culture of Bionectria sp., which was isolated from a fungus garden of the fungus-growing ant Apterostigma dentigerum, in Costa Rica. The structure of bionectriol A was determined mainly through NMR and mass spectroscopic data, as well as UV and IR spectra. The relative configurations of the main chain, the pyranohexose, and the pentitol moiety were elucidated by ¹H–¹H coupling constants and ROESY NMR spectral analysis.     

Theoretical electronic structure of the lowest-lying states of the YI molecule

CAS-SCF/MRCI calculations have been performed for 15 molecular states in the representation ^2S+1Λ^(+/−) (neglecting spin–orbit effects) for the molecule YI. The corresponding 33 molecular states in the representation Ω^(+/−) (including spin–orbit effects) have been calculated using a semi-empirical spin–orbit pseudopotential built up for yttrium. Calculated potential energy curves and spectroscopic constants are reported, to the best of our knowledge they are the first ones from ab initio methods for this molecule. Present results are compared to experimental accurate data available for the ground X¹Σ⁺ and 3 excited states (1)¹Π, (2)¹Σ⁺ and (2)¹Π.     

High-resolution infrared analysis of the ν17 band of pyridine

A method for analyzing asymmetric top rovibrational bands displaying both blended and resolved features is described. The two-phase computational procedure uses a modified version of the asymmetric rotor-band contour program FASTPLOT to generate a preliminary set of upperstate spectroscopic constants. The parameters are subsequently refined by employing the assigned line-fitting formalism of the ASYROT program using both resolved and blended features. The technique is detailed in a comprehensive analysis of the ν₁₇ band of pyridine. Inclusion of quartic centrifugal distortion constants was found to satisfactorily model a high-resolution (0.004 cm^?1) spectrum of this band, yielding a standard deviation of 0.00137 cm^?1. The variation in the rotational parameters with vibrational quantum number is examined in terms of possible weak rovibrational perturbations to the ν₁₇ state. An ab initio calculation of the ν₁₇/ν₂₇ Coriolis coupling constant indicates the observed results are consistent with the interaction of these two vibrational states.