A Direct Energetic Measure of
Aromaticity Based on a
Cleavage of the Rings in
Cyclic Compounds
Speaker: Ke An
Advisor: Jun Zhu
2013/11/08
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Main Content
Introduction
Motivation
Results and Discussion
Conclusion
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Introduction
1. Criteria of Aromaticity
 Structural Criteria
 Planarity
 Equal bond length tendency
Krygowski et al, Chem. Rev. 2001, 101, 1385.
 Diamagnetic susceptibility
exaltation (Λ)
 Magnetic Criteria
Pascal, P. Ann. Chim. Phys. 1910, 19, 5
Pink, Trans. Faraday Soc. 1948, 4, 407
Schleyer, Pure Appl. Chem. 1996, 68, 209
 H+ NMR Chemical Shift
Paquette et al, J. Am. Chem. Soc. 1990, 112, 8776
Sekiguchi et al, J. Am. Chem. Soc. 1991, 113, 7081
 NICS (Nucleas-Independent
Chemical Shifts)
Schleyer et al, J. Am. Chem. Soc. 1996, 118, 6317
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Introduction
1. Criteria of Aromaticity
 Reactive Criteria
Electrophilic aromatic substitution
 HOMA= 1-257.7/n∑(dopt-di)2
Krygowski et al, Tetra. Lett. 1972, 13, 3839.
 RE (resonance energy)
 Energetic Criteria
Schaad et al, Chem. Rev. 2001, 101, 1465.
 ASE (aromatic stabilization energy)
Cryanski et al, Tetrahedron 2003, 59, 1657.
 ISE (isomerization stabilization
energy)
Schleyer et al, Org. Lett. 2002, 4, 2873.
Wannere et al, Org. Lett. 2003, 5, 2983.
J. Zhu et al, Org. Lett. 2013, 15, 2442.
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Introduction
2. Isomerization Stabilization Energy
Schleyer et al, Org. Lett. 2002, 4, 2873.
Wannere et al, Org. Lett. 2003, 5, 2983.
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Introduction
3. Baird’s Rule
Rules for ground state aromaticity are reversed in the
lowest  triplet state.
4n rings: “aromatic character”
4n+2 systems: “antiaromaticity”.
Baird, N.C. J. Am. Chem. Soc. 1972, 94, 4941
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Motivation
To develop an energetic method to evaluate the triplet
aromaticity.
nonaromatic
aromatic
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Results and Discussion
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Results and Discussion
Structures and energies of anti- and syn-butadiene conformations in their S0 and T1 states.
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Results and Discussion
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Results and Discussion
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Results and Discussion
Plot of ISE vs NICS(T1;1)zz for a series of planar monocyclic species with 4n and 4n+2
 electrons in the T1 state.
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Conclusion
 The ISE method can be extended to confirm the aromaticity of the T1
state of 4n -cyclic species.
 Most annulenes with 4n+2  -electrons in the T1 state have a strong
tendency to reduce their antiaromaticity by nonplanar deformations.
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Thanks For Your Attention !
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