Ab initio spectrograms of the molecular vibrational spectrum

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Use of ab initio computational results and experimental frequencies to construct the internal rotational potential function for acrolein

Ab initio optimizations of the complete acrolein molecular geometry accomplished using analytical gradient methods at the 6-31G* SCF level at ten points during rotation from the planar trans- to the planar cis-form (rotation about the single CC bond) are used to calculate the values of the Pitzer function F(φ), the coefficients of its Fourier expansion, and the coefficients in the potential energy expansion. The theoretical potential expansion coefficients are then adjusted using the experimental torsional frequencies and their overtones for the trans- and cis-forms of CH2CHCHO and CH2CHCDO. For the cis-conformer two different sets of experimental frequencies are employed. The dependence of the slope of the acrolein potential energy curve on the experimental frequency set used for the cis-rotamer is discussed. © 1990.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Ab initio vibrational analysis of 3,3-dimethyl-1-butene

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Effect of molecular geometry relaxation on the potential energy function of internal rotation

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Geometric parameter variations in methyl substituted cyclopropenes

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Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, trimethylgermyl, trimethylstannyl and trimethylplumbyl derivatives of 3,3-dimethylcyclopropene. XI. Secondary periodicity

Regularities of changes in the structural parameters and vibrational wavenumbers for certain moieties of the title compounds are presented. The optimized geometrical parameters and the force fields of the di- and monosubstituted 3,3-dimethylcyclopropenes were determined at the HF/3-21G* and HF/DDAll pseudopotential levels, respectively. These theoretical levels were chosen because of peculiarities of Gaussian 03 suite of programs for the Sn and Pb atoms. The theoretical vibrational wavenumbers were calculated using the corresponding scaled force fields. The regularities obtained in the form of zigzag lines for the properties as a function of the period number of X in the Mendeleyev Periodic Table are analogous to regularities that are characteristic of properties of the atoms of the 14 (IVA) group. This is known as the secondary periodicity phenomenon. © 2009 Elsevier B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, trimethylgermyl, trimethylstannyl, and trimethylplumbyl derivatives of 3,3-dimethylcyclopropene. IX. 3,3-Dimethyl-1-(trimethylplumbyl)cyclopropene

The geometrical parameters and quantum mechanical force fields (QMFF's) of 3,3-dimethyl-1-(trimethylplumbyl)cyclopropene (I), 3,3-dimethyl-1-(t-butyl)cyclopropene (II), 3,3-dimethyl-1-(trimethylsilyl)cyclopropene (III), 3,3-dimethyl-1-(trimethylgermyl)cyclopropene (IV), and 3,3-dimethyl-1-(trimethylstannyl)cyclopropene (V) were calculated at the pseudopotential (HF/SDDAll) level. Analysis of the optimised geometrical parameters was performed. The set of scale factors for correction of the pseudopotential QMFF of III was determined using its earlier well-characterised vibrational spectrum. Transferral of the set of scale factors obtained for III to the QMFF's of I, II, IV and V was followed by calculation of the fundamental vibrational frequencies. Analysis of the results for these molecules revealed some peculiarities in the vibrational frequencies obtained at the pseudopotential level. © 2006 Elsevier B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Effective potential function of internal rotation in the nonrigid approximation

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Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, trimethylgermyl, trimethylstannyl, and trimethylplumbyl derivatives of 3,3-dimethylcyclopropene. X. Some regularities

The changes in the vibrational frequencies of 1-tert-butyl and 1,2-di-tert-butyl derivatives of 3,3-dimethylcyclopropene brought about by substitution of the central carbon atom (X) of the tert-butyl moieties by Si, Ge, Sn, or Pb atoms are examined. The most important decrease in the vibrational frequencies implicating the X(CH3)3 moieties is noted for substitution of X = C by Si. The substitutions of Si by Ge or Ge by Sn or Sn by Pb are not accompanied by the pronounced frequency shifts observed for the C → Si transition. An explanation is given for trends in these vibrational frequencies for the transitions X = C → Si → Ge → Sn → Pb. It is concluded that there are lower limiting values of the vibrational frequencies of a molecular moiety which are approached when the mass of its isovalent atom is increased. This leads to the formation of cluster regions in the vibrational spectra for the frequencies of the SnC3 and PbC3 moieties. © 2007 Elsevier B.V. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Structural and vibrational analyses of t,C,t,T,t,T,t-deca-1,3,5,7,9- pentaene

An analysis of the results of the fluorescence spectrum investigation of all-trans-deca-1,3,5,7,9-pentaene and t,C,t,T,t,T,t-deca-1,3,5,7,9-pentaene in an n-decane matrix [B.E. Kohler, V. Terpougov, J. Chem. Phys. 108 (1998) 9586-9593] has been performed using scaled quantum mechanical force field (SQM-FF) methodology at the HF/6-31G level. The measured vibronic wavenumbers were assigned taking into account the results of quantum-chemical predictions of the vibrational spectra for all-trans-deca-1,3,5,7,9-pentaene and t,C,t,T,t,T,t-deca-1,3,5,7,9-pentaene. Results from additional calculations at the MP2(FC)/aug-cc-pVDZ and B3LYP/6-311++G(d,p) levels are also reported. © 2012 Elsevier B.V.SCOPUS: ar.jinfo:eu-repo/semantics/publishe