The heats of combustion and strain energies of some cyclophanes

Shieh, Chyi-Feng; McNally, Donal; Boyd, Richard H.

doi:10.1016/s0040-4020(01)82898-2

Cited by 73 publications

(33 citation statements)

References 14 publications

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“…The implications of this are the subject of further study. The bonditorsion functional form used by MM3 is given by (17) and differs from eq. (14).…”

Section: Bond/'i'oksion and Angle/iohsion Couplingmentioning

confidence: 99%

Derivation of class II force fields. I. Methodology and quantum force field for the alkyl functional group and alkane molecules

Maple¹,

Hwang²,

Stockfisch³

et al. 1994

J Comput Chem

790

547

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A new method for deriving force fields for molecular simulations has been developed. It is based on the derivation and parameterization of analytic representations of the ab initio potential energy surfaces. The general method is presented here and used to derive a quantum mechanical force field (QMFF) for alkanes. It is based on sampling the energy surfaces of 16 representative alkane species. For hydrocarbons, this force field contains 66 force constants and reference values. These were fit to 128,376 quantum mechanical energies and energy derivatives describing the energy surface. The detailed form of the analytic force field expression and the values of all resulting parameters are given. A series of computations is then performed to test the ability of this force field to reproduce the features of the ab initio energy surface in terms of energies as well as the first and second derivatives of the energies with respect to molecular deformations. The fit is shown to be good, with rms energy deviations of less than 7% for all molecules. Also, although only two atom types are employed, the force field accounts for the properties of both highly strained species, such as cyclopropane and methylcyclopropanes, as well as unstrained systems. The information contained in the quantum energy surface indicates that it is significantly anharmonic and that important intramolecular coupling interactions exist between internals. The representation of the nature of these interactions, not present in diagonal, quadratic force fields (Class I force fields), is shown to be important in accounting accurately for molecular energy surfaces. The Class I1 force field derived from the quantum energy surface is characterized by accounting for these important intramolecular forces. The importance of each 'Author to whom all correspondence should be addressed. tl'resent address: Dept. of Chemistry, Ben Gurion Univ. of the Negev, Beersheva 84105, Israel. Journal of Computational DERIVATION OF CLASS II FORCE FIELDSof the interaction terms of the potential energy function has also been assessed. Bond anharmonicity, angle anharmonicity, and bond/angle, bond/ torsion, and angle/angle/ torsion cross-term interactions result in the most significant overall improvement in distorted structure energies and energy derivatives. The implications of each energy term for the development of advanced force fields is discussed. Finally, it is shown that the techniques introduced here for exploring the quantum energy surface can be used to determine the extent of transferability and range of validity of the force field. The latter is of crucial importance in meeting the objective of deriving a force field for use in molecular mechanics and dynamics calculations of a wide range of molecules often containing functional groups in novel environments.

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“…The implications of this are the subject of further study. The bonditorsion functional form used by MM3 is given by (17) and differs from eq. (14).…”

Section: Bond/'i'oksion and Angle/iohsion Couplingmentioning

confidence: 99%

Derivation of class II force fields. I. Methodology and quantum force field for the alkyl functional group and alkane molecules

Maple¹,

Hwang²,

Stockfisch³

et al. 1994

J Comput Chem

790

547

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“…(2) Boyd (1966). (3) Chyi-feng Shieh, McNally & Boyd (1969). * AH~ values obtained from the relation AH ° =AH,Z98+ 2RT (Rae & Mason, 1968).…”

Section: Resultsmentioning

confidence: 99%

Interatomic potential functions for hydrocarbons from crystal data: transferability of the empirical parameters

Mirsky¹

1976

Acta Cryst Sect A

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The transferability of (6-exp) interatomic n0n-bonded potential functions for hydrocarbons previously derived from low-temperature structures extrapolated to 0 K, sublimation heats and elasticity data of model molecular crystals, was tested by calculation of properties of other crystals not involved in the earlier optimization process. Equilibrium structures and sublimation heats were calculated, in agreement with experiment, for methane CH4, adamantane (CH2)6(CH)4, 2,2-paracyclophane (CH2)4(C6H4)2 and 3,3-paracyclophane (CH2)6(C6H4)2 crystals. The solid-solid phase-transition characteristics of adamantane were described consistently with the same potential force field. For the cubic phase of adamantane the orientationally disordered molecular arrangement, suggested by X-ray experiment, was predicted theoretically. The calculation of the structures and heats of sublimation of the same crystals were repeated with a set of potential functions derived recently [Williams, Acta Cryst. (1974). A30, 71-77] on the basis of experimental data not extrapolated to 0 K. The difference between the two approaches is discussed and illustrated by comparing the calculated results.

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“…In Table 5 we report mean values of geometrical features, calculated from equivalent observed data; in the last column of Table 5 we report, for comparison, data calculated on a model molecule of (I) using the molecular-mechanics method. The strain-energy parameters are those of Shieh, McNally & Boyd (1969) with the addition of new ones in connection with the carboxylic group. There are some significant differences between the average geometrical data of the -COOH and -COOCH a groups which are in good agreement with predicted values obtained from a regression analysis carried out on a large number of experimental crystallographic data (Borthwick, 1980).…”

Section: Discussionmentioning

confidence: 99%

The structures of 1,2,3,4,5,6-cis-cyclohexanehexacarboxylic acid and its hexamethyl ester

Brückner¹,

Giunchi²,

Silvestro³

et al. 1981

Acta Crystallogr Sect B

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586HEXAPHENYL GROUP IVa ETHERS site is available for intermolecular excimer formation without appreciable strain during formation and the spectra are similar to that found in bulk polystyrene (Frank & Harrah, 1974).Solution spectra of these compounds exhibit both monomer and intramolecular excimer fluorescence. The ratio of these two emissions is temperature dependent, indicating that all compounds show a conformational barrier to excimer formation. Barrier-height determinations are now under way.The authors gratefully acknowledge the assistance of Bruce P. Engler, who prepared these materials, and David T. Sanders, who assisted in the X-ray laboratory. The authors also thank Professor G. A. Jeffery for useful discussions concerning the possible differences in molecular conformations represented by these structures as well as for kindly providing a preprint of their work. data calculated for a model molecule by use of the molecular-mechanics method.

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The heats of combustion and strain energies of some cyclophanes

Cited by 73 publications

References 14 publications

Derivation of class II force fields. I. Methodology and quantum force field for the alkyl functional group and alkane molecules

Derivation of class II force fields. I. Methodology and quantum force field for the alkyl functional group and alkane molecules

Interatomic potential functions for hydrocarbons from crystal data: transferability of the empirical parameters

The structures of 1,2,3,4,5,6-cis-cyclohexanehexacarboxylic acid and its hexamethyl ester

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