Journal ArticleDOI
p-Benzyne derivatives that have exceptionally small singlet-triplet gaps and even a triplet ground state.
TLDR
It is believed that rehybridization of the ring carbons destabilizes the A radical orbital and can lead to large singlet-triplet splittings.Abstract:
In an effort to find a p-benzyne (1,4-didehydrobenzene) derivative with a triplet ground state, we have investigated tetrasubstitution by −F, −NH2, −CH3, and −NO2 groups. These were predicted to reduce the singlet−triplet gap, but none led to a triplet ground state because of unexpected destabilization of one of the radical orbitals. This effect is likely the result of rehybridization of the substituted C atom, which has been observed for substituted benzene and perturbs the side σ and σ* orbital energies of the phenyl ring. The role of substituent rotation on the energy difference between the two nominally singly occupied orbitals (S and A) was then investigated. The energy of the A radical orbital was found to be much more sensitive to perturbations within the σ C−C framework than the S MO. Consequently, we believe that rehybridization of the ring carbons destabilizes the A radical orbital and can lead to large singlet−triplet splittings. To test this hypothesis, calculations on a p-benzyne with 2,6 sub...read more
Citations
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Orbital hybridization: a key electronic factor in control of structure and reactivity
TL;DR: A review of the fundamental factors responsible for hybridization trends in organic and main group compounds can be found in this article, where the authors discuss the importance of hybridization effects in structural and reactivity puzzles.
Journal ArticleDOI
Hybridization trends for main group elements and expanding the Bent's rule beyond carbon: more than electronegativity.
TL;DR: The ability to change hybridization without changes in polarization provides an alternative way to control structure and reactivity, as illustrated by the strong correlation of strain in monosubstituted cyclopropanes with hybridization in the bond to the substituent.
Journal ArticleDOI
Rehybridization as a general mechanism for maximizing chemical and supramolecular bonding and a driving force for chemical reactions
TL;DR: Computations clearly illustrate the generality of rehybridization in a variety of chemical phenomena, which involve structural reorganization in hydrogen‐bonded complexes, nonhyperconjugative stereoelectronic effects in saturated heterocycles, Mills‐Nixon effect, and contrasting substituent effects in cycloaromatization reactions.
Journal ArticleDOI
An extended multireference study of the electronic states of para-benzyne.
TL;DR: Of the 32 states characterized, 15 were multiconfigurational, including the ground (1)A(g) state, providing further evidence for the necessity of a multireference approach for p-benzyne.
Journal ArticleDOI
The effect of substituents on electronic states' ordering in meta-xylylene diradicals: qualitative insights from quantitative studies.
Tao Wang,Anna I. Krylov +1 more
TL;DR: The changes in the exocyclic C-C bond length in substituted meta-xylylenes, derived from equilibrium structures calculated by using analytic gradients for the EOM-SF-CCSD method, support the original resonance theory explanation, but similar resonance-theory-based reasoning fails to explain the quantitative difference between positively and negatively charged systems.
References
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Application of the pople-santry-segal CNDO method to the cyclopropylcarbinyl and cyclobutyl cation and to bicyclobutane
TL;DR: In this article, the CNDO method has been applied to the cyclopropylcarbinyl and cyclobutyl cations, and has given results which are in very good accord with experimental data.
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Atomic Screening Constants from SCF Functions. II. Atoms with 37 to 86 Electrons
TL;DR: In this article, minimal basis set atomic functions for ground state atoms from Rb(Z=37) to Rn(Z =86) are presented, in order to obtain systematic data for the screening constants and atomic radii following the work initiated by Slater.
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