Geometry of molecules. 3. Iterative maximum overlap calculations of bond lengths in some conjugated polyenes and their alkylated derivatives

Maksić, Zvonimir B.; Rubčić, Antun

doi:10.1021/ja00455a004

Cited by 65 publications

(8 citation statements)

References 15 publications

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“…We prefer to model it by the C-C bond in cyclooctatetraene, which possesses sp 2.2 -sp 2.2 hybridization as estimated by the IMO (iterative maximum overlap) approximation. 41 The calculated C-C bond distance by the IMO procedure is 1.46 Å, in excellent agreement with the electron diffraction measurements. 41 It is interesting to mention that virtually the same value (1.459 Å) was obtained for the d(C sp2 -C sp2 ) bond distance in the twisted D 2d triplet state of ethylene by using the MP3/6-31G** method.…”

Section: Resultssupporting

confidence: 79%

“…41 The calculated C-C bond distance by the IMO procedure is 1.46 Å, in excellent agreement with the electron diffraction measurements. 41 It is interesting to mention that virtually the same value (1.459 Å) was obtained for the d(C sp2 -C sp2 ) bond distance in the twisted D 2d triplet state of ethylene by using the MP3/6-31G** method. 42 Employing the CdC bond length in ethylene of 1.34 Å, one can easily construct the cyclohexatriene model system which describes perfectly frozen Kekule structure of benzene.…”

Section: Resultssupporting

confidence: 79%

“…The problem is, however, definition of the interatomic distance corresponding to the idealized single C−C sp 2 −sp 2 bond. We prefer to model it by the C−C bond in cyclooctatetraene, which possesses sp 2.2 −sp 2.2 hybridization as estimated by the IMO (iterative maximum overlap) approximation . The calculated C−C bond distance by the IMO procedure is 1.46 Å, in excellent agreement with the electron diffraction measurements .…”

Section: Resultsmentioning

confidence: 53%

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Additivity of the Proton Affinity in Aromatics: Fluorinated Naphthalenes^⊥

1997

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Absolute proton affinities (PAs) of fluorinated naphthalenes and their additivity are considered theoretically by utilizing the MP2(fc)/6-31G**//HF/6-31G*+ZPE(HF/6-31G*) model. The hierarchy of the PAs in the parent naphthalene compound (PA)1 > (PA)2 > (PA)8a, where subscripts denote sites of the protonation, is interpreted in terms of the aromaticity defect. Since the fluorine substitution influences PA values in remote parts of the molecular systems, it is concluded that the long range interactions in fluorine derivatives are transmitted via the mobile π-electrons thus giving rise to significant resonance effects. It is also shown that the additivity formula based on the independent substituent approach works very well in polysubstituted naphthalenes as evidenced by a very small average absolute deviation, with one notable exceptionprotonation at the ipso-position. In this case the out-of-plane bending of the C−F bond leads to considerable puckering of the aromatic ring which is not present in the parent naphthalene. Consequently, the influence of a substituent on the PA at the same carbon center cannot be considered a small perturbation which results in deviations from the strict additivity. Finally, it should be pointed out that low PA values for ipso-protonation are compatible with the (per)fluoro effect. The origin of the additivity is briefly considered. It appears that it is a consequence of cancellation of the many-body effects in the initial (base) and final (conjugated acid) states. The same formula of additivity (mutatis mutandis) should be applicable in other polysubstituted aromatics.

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Section: Resultssupporting

confidence: 79%

Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 53%

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Additivity of the Proton Affinity in Aromatics: Fluorinated Naphthalenes^⊥

1997

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“…This observation is in agreement with earlier studies on conjugated polyenes. 81,82 This also explains the relatively short C-N and C-O distances in benzene derivatives.…”

Section: Methodsmentioning

confidence: 87%

Substituent effects in mono- and disubstituted 1,3,5,7-cyclooctatetraene derivatives in natural and planar conformations

Palusiak

Krygowski

2009

New J. Chem.

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Substituent effect in cyclooctatetraene (COT) has been investigated by means of quantum-chemical (DFT-B3LYP) calculations. Two substituents, nitroso (p-electron-withdrawing) and hydroxy (p-electron-donating), have been examined and compared with monosubstituted and unsubstituted systems. Additionally, both the natural (tub-shaped) and the planar geometries of the COT have been taken into account. The behavior of COT ring, being the antiaromatic 4n p-electron system, has been compared with that of the benzene ring, being the aromatic 4n + 2 system. The 1,4-substitution differs significantly from the 1,3-and 1,5-substitution, which corresponds to an analogous situation found for benzene derivatives (para vs. meta substitution). Substituents influence COT more effectively in its planar geometry as compared with the tub-shaped geometry. This is due to the better overlapping of the p z orbitals of the carbon atoms within the ring in its planar conformation. As far as the p-electron communication between the substituents is concerned, the behavior of both 4n and 4n + 2 systems is in some way similar. Both systems tend to keep their p-electronic structures. Nevertheless, benzene ring, i.e. 4n + 2 system seems to be a clearly worse medium for transmission of the substituents communication than its 4n counterpart.

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“…Later, this method has been applied and further developed by many others [8-601. Among the maximum overlap methods, the iterative maximum overlap approximation (IMOA) method [26] proposed by MaksiC et al could be applied not only to construct systematically the best HAOS but also to determine molecular geometries through introducing the linear relationship between the bond length and bond overlap integral. The improved IMOA ZHAN method [50] and the method [49] for calculation of molecular maximum bond energy structure based on the new bond energy formula could be employed to directly optimize molecular geometries and calculate force constants.…”

Section: Introductionmentioning

confidence: 99%

Maximum overlap symmetry molecular orbital model

Zhan

1992

Int J of Quantum Chemistry

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This paper provides a brief and systematic presentation of the basic principle and method of the maximum overlap symmetry molecular orbital (MOSMO) model and its application to simplification of molecular orbital calculation and to calculation of molecular structures and properties, together with some new results about the MOSMO calculation and new insights concerning the further extension of the principle and method. It has been shown that the theoretical method of the MOSMO model is very simple, reliable, and useful and can be employed to study the structure-property relation in even very large molecular systems. The numerical results obtained from the MOSMO calculation on various semiempirical molecular orbital approximation levels show that when the same parametrization, such as one of those employed in EHMO, C N D O /~, and HMO methods, is adopted, the MOSMOS are very close to the canonical molecular orbitals obtained from the customary LCAO method and the MOSMO calculation requires less computing time than does the LCAO method. The MOSMO calculation can be used for rapidly obtaining reasonably good molecular geometries, vibrational frequencies, and other properties of molecules by employing a simple improved semiempirical parametrization. Equilibrium geometries, vibrational frequencies, and other results are in good agreement with the experimental data and the results obtained from ab initio molecular orbital calculation. The basic calculational procedure of the MOSMO model can be extended further and has been employed to give some new results, to propose some new theoretical schemes and principles, and to introduce some new interesting theoretical problems that deserve to be studied further.

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Geometry of molecules. 3. Iterative maximum overlap calculations of bond lengths in some conjugated polyenes and their alkylated derivatives

Cited by 65 publications

References 15 publications

Additivity of the Proton Affinity in Aromatics: Fluorinated Naphthalenes^⊥

Additivity of the Proton Affinity in Aromatics: Fluorinated Naphthalenes^⊥

Substituent effects in mono- and disubstituted 1,3,5,7-cyclooctatetraene derivatives in natural and planar conformations

Maximum overlap symmetry molecular orbital model

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Geometry of molecules. 3. Iterative maximum overlap calculations of bond lengths in some conjugated polyenes and their alkylated derivatives

Cited by 65 publications

References 15 publications

Additivity of the Proton Affinity in Aromatics: Fluorinated Naphthalenes⊥

Additivity of the Proton Affinity in Aromatics: Fluorinated Naphthalenes⊥

Substituent effects in mono- and disubstituted 1,3,5,7-cyclooctatetraene derivatives in natural and planar conformations

Maximum overlap symmetry molecular orbital model

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Product

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Additivity of the Proton Affinity in Aromatics: Fluorinated Naphthalenes^⊥

Additivity of the Proton Affinity in Aromatics: Fluorinated Naphthalenes^⊥