Supplementary material (ESI) for Perkin Transactions 2

This journal is The Royal Society of Chemistry 2002

Supplemental Information

Möbius Aromatic Forms of 8-p Electron Heteropines

William L. Karney,a * Christian J. Kastrup,b Steven P. Oldfieldb and Henry S. Rzepab *

aDepartment of Chemistry, University of San Francisco, California, 2130 Fulton St., San Francisco, California, USA, 94117-1080, USA. bDepartment of Chemistry, Imperial College of Science Technology and Medicine, London, SW7 2AY
Summary: Ab initio calculations at the B3LYP//6-31G(d) level predict that Möbius-like conformations of O, NF, S and PF-substituted 7-membered ring 8-p electron perfluoro-annulenes with an axis of symmetry exist, but they are of higher energy than isomers with a plane of symmetry. Chiral inversion of the Möbius perfluoroazepine system via a planar structure is shown to be an orbital symmetry forbidden process for a closed shell singlet state, resulting from the nodal characteristics of the highest occupied Möbius molecular orbital. The orbital origins of an unusual electron-correlation dependent lengthening predicted for the N-F bond in the Möbius conformation of the azepine but largely absent in the analogous phosphorus system are discussed. Structural variations based on incorporating a biphenyl motif are explored, but in no case was the Möbius form lower in energy than the achiral non-aromatic geometries retaining a plane of symmetry.
Graphical Abstract

How to make use of this Supplemental Information

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Table 1. Energies, kcal mol-1, relative to 2 or 4 (B3LYP/6-31G(d) in Hartree) and computed NICS Values (ppm).
System Point Group C=C
Dihedral angle
Relative Energy (2 or 4
in parentheses)
1a Cs cis,cis,cis 0 0 2.6 (-902.7656) -5.7
1a C2 cis,trans,cis 0 94.8 36.3 -10.5
1a C2v cis,cis,cis 1a 0.0 14.5 +9.4
1b Cs cis,cis,cis 0 0 4.7 (-1225.7418) -8.0
1b C2 cis,trans,cis 0 107.7 36.7 -10.9
1b C2v cis,cis,cis 1b 0.0 21.3 +7.3
1c Cs cis,cis,cis 0 0 -21.3 {-24.7}g (-982.0395) -9.5
1c C2 cis,cis,cis (7c) 0 32.4 4.9 {-1.1}g -6.6
1c C1 cis,trans,cis 0 98.1 23.9 -10.7
1c C2v cis,cis,cis (5c) 2c 0.0 14.1 17.5
1c C2v cis,cis,cis (8c) 2d 0.0 27.8 {4.2}g -
1d Cs cis,cis,cis 0 0 -11.4 {-9.8}g (-1268.7453) -7.9
1d C2 cis,cis,cis (7d) 0 43.9 46.0 {47.7}g -10.9
1d C1 cis,trans,cis 0 111.0 23.0 -6.5
1d C2v cis,cis,cis (6d) 3e 0.0 81.9 53.4
1d C2v cis,cis,cis (8d) 3f 0.0 67.0 {63.1}g -8.5
3a C2 cis,cis,cis 0 39.4 40.5 (-614.7114) 26.5, -1.1h
3b C2 cis,cis,cis 0 42.7 25.5 (-799.1745) 16.5, -3.1h
3c C2 cis,cis,cis 0 53.8 46.2 (-937.7039) 14.9, -4.0h
3d C2 cis,cis,cis 0 41.2 19.3 (-594.8438) 20.8,-1.0h
3e C2 cis,cis,cis 0 58.4 52.6 (-881.4595) 8.2, -6.2h
3f C2 cis,cis,cis 0 60.2 34.6 (-1065.9222) 4.0, -7.7h
aNegative root of Hessian; 118.8i cm-1 corresponding to Cs distortion. b89.4i cm-1 corresponding to Cs distortion. c472.0i, 115.8i cm-1 corresponding to Cs distortions. d59i corresponding to in-plane N-F bending) and 54i cm-1 corresponding to C2 distortion. e382.7i and 119.3i cm-1 corresponding to C2 distortions and 270.9i corresponding to Cs distortion. f 495.3i cm-1 (b1) corresponding to Cs distortion, 205.4i cm-1 (b2) corresponding in-plane P-F bending and 62.8i cm-1 (a2) corresponding to C2 distortion. g SCRF(DPCM) Solvation model.h Value for 6-ring.


Figure 1. B3LYP/6-31G* bond lengths (Å) for stationary points for perfluoro-oxepine and perfluoro-thiepine.

Figure 2. B3LYP/6-31G* bond lengths (Å) for isomers of perfluoro-azepine.

Figure 3. B3LYP/6-31G* Orbital Correlations for 5c, 7c and 8c.
5c Symmetry 7c 8c Symmetry
a2 a b1
b1 a a2
a1 b a1
a1 a a2
a2 b b1
b1 a b1
a2 a a1
b1 b a2
b1 b a1
b1 b b1
a1 a b1

Figure 4. B3LYP/6-31G* bond lengths (Angstroms) for for stationary points for 1d.

Figure 5. B3LYP/6-31G* Orbital Correlations for 6d, 7d and 8d
5d Symmetry 6d 7d Symmetry
a2 b a2
b1 a b1
b1 b b1
a2 a a1
a2 a b1
b1 b a2
b1 b b1
b1 b b1

Figure 6. A relaxed B3LYP/6-31G potential scan in C2 symmetry connecting 7d and 8d. The dihedral angle is defined as C4-Du-P-C2, where Du is the mid-point of C4-C5.
Variation of bond lengths with twist
Figure 7. B3LYP/6-31G* Highest occupied Molecular Orbital for 3d.