Charge distributions and chemical effects. XLII. Atomic charges and their role in energy calculations

Fliszár, Sándor

doi:10.1002/qua.560290303

Cited by 6 publications

(2 citation statements)

References 24 publications

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“…The atom numbering is that of Fig. 2. grounds, we tentatively scale our STO-3G results as follows and subsequently show that this approximation suffices to bring the present results in line with the vast body of evidence gathered so far concerning the role of electronic charges in determining molecular energies (37,(40)(41)(42).…”

Section: Computational Proceduressupporting

confidence: 78%

“…The required level of sophistication, using correlated wave functions constructed from extended and carefully optimized basis sets (41,42), is out of computational reach for the molecules at hand for which we only know Mulliken populations obtained from the STO-3G basis set with standard orbital exponents. On the other hand, past experience (37,(40)(41)(42) indicates that the Aqils obtained in this manner correlate with their corrected counterparts satisfying charge-energy relationships with great accuracy. On these 2~n a Mulliken-type charge analysis not involving the classical equipartitioning of overlap populations between dissimilar atoms, the net charge of each individual atom must be corrected depending on what is bonded to it (37).…”

Section: Computational Proceduresmentioning

confidence: 99%

See 1 more Smart Citation

Structural and electronic origin of the conformational behavior of biphenyl-like α-diimine ligands. A theoretical study

Barone¹,

Minichino²,

Fliszár³

et al. 1988

Can. J. Chem.

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VINCENZO BARONE, CAMILLA MINICHINO, SANDOR FLISZAR, and NINO RUSSO. Can. J. Chem. 66, 1313 (1988). The conformational behavior of aromatic a-diimines has been analyzed by means of ab initio computations making use of the standard STO-3G minimal basis set. The absolute minimum of the potential energy curve always corresponds to the planar trans conformation and a secondary minimum is also found for a nonplanar cisoid conformation. An alternate analysis, rooted in bond energy calculations explicitly involving the charges of the bond-forming atoms, indicates that bonded rather than nonbonded interactions are responsible for the observed conformational preferences.VINCENZO BARONE, CAMILLA MINICHINO, SANDOR FLISZAR, et NINO RUSSO. Can. J. Chem. 66, 13 13 (1988). Une Ctude conformationelle ab initio, conduite en base minimale STO-3G, est prksentke pour une sCrie d' a-diimines aromatiques. La conformation planaire trans correspond dans tous les cas au minimum absolu de la courbe de potentiel, un minimum secondaire &ant observe pour la forme cisoi'de non planaire. Une analyse complkmentaire, baske sur des calculs d'Cnergies de liens en termes de charges Clectroniques, montre que ce sont les interactions liCes (par opposition a celles entre atomes non liCs) qui sont responsables pour les prkfkrences conformationelles observkes. IntroductionTransition metal complexes of aromatic a-diimine ligands such as 2,2'-bipyridine (bpy) have found extensive applications in preparative and analytical chemistry for almost a century (1-3) and are currently receiving further attention in view of solar energy conversion and storage (4, 5) and of modelling intermediates in transition metal catalyzed reactions (6, 7). In this connection, since the replacement of CH groups by N atoms leads to more electron-deficient compounds, attention has turned to coupled diazines, such as 4,4'-bipyrimidine (bpm), 2,2'-bipyrazine (bpz), or 3,3'-bipyridazine (bpd). Although the complexing ability of these ligands is essentially related to their ionization potentials and electron affinities (8, 9), for such flexible molecules the conformation assumed upon complexation often does not correspond to the equilibrium conformation of the free ligand. This consideration stimulated, several experimental investigations about the conformational behavior of-heteroaromatic systems consisting of two rings linked together by essentially single bonds (10-13). Only the neighborhood of potential energy minima can be well characterized by these techniques, the rest of the potential energy curve remaining ill defined. Theoretical computations do not suffer from this problem and the only limitation to their systematic use is the definition of the best compromise between reliability of the results and computational costs. There is now a general consensus on the use of non empirical computations employing minimal or split valence basis sets (13-18) in the rigid rotor approximation (14-16).

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Section: Computational Proceduressupporting

confidence: 78%

Section: Computational Proceduresmentioning

confidence: 99%

Structural and electronic origin of the conformational behavior of biphenyl-like α-diimine ligands. A theoretical study

Barone¹,

Minichino²,

Fliszár³

et al. 1988

Can. J. Chem.

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On the core electron binding energy of carbon and the effective charge of the carbon atom

Sundberg

Larsson

Folkesson

1988

Journal of Electron Spectroscopy and Related Phenomena

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On the CH bond dipole moment in alkanes

Lazzeretti

Zanasi

Raynes

1987

The Journal of Chemical Physics

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The Thomas–Reiche–Kuhn sum rule, within the acceleration gauge for the transition dipole moment, is used to partition the total number of electrons in a molecule and to define atomic populations, which can be related to corresponding experimental estimates of atomic polar tensors from IR intensities. As a bond dipole moment can only be defined for diagonal atomic polar tensors, it is shown that the assumption of a C–H bond moment, transferable from molecule to molecule in the alkane series, is physically unreliable. From experimental IR intensities of methane we infer that, for the equilibrium geometry, μC–H =0.339 D, directed C−H+. Accordingly, it is argued that the theoretical bond dipole moments, estimated for the C–H bond in methane via localization procedures of SCF wave functions, are questionable, as they predict the opposite polarity. Finally, a resolution of the electric dipole moment into atomic contributions is suggested.

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Charge distributions and chemical effects. XLII. Atomic charges and their role in energy calculations

Cited by 6 publications

References 24 publications

Structural and electronic origin of the conformational behavior of biphenyl-like α-diimine ligands. A theoretical study

Structural and electronic origin of the conformational behavior of biphenyl-like α-diimine ligands. A theoretical study

On the core electron binding energy of carbon and the effective charge of the carbon atom

On the CH bond dipole moment in alkanes

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