Two sources of the decrease of aromaticity: Bond length alternation and bond elongation. Part II. An analysis based on geometry of the singlet and triplet states of 4n pi annulenes: C4H4, C5H5+, C6H62+, C7H7-, C8H8, C9H9+

Authors
Krygowski, TM Cyranski, MK
Citation
Tm. Krygowski et Mk. Cyranski, Two sources of the decrease of aromaticity: Bond length alternation and bond elongation. Part II. An analysis based on geometry of the singlet and triplet states of 4n pi annulenes: C4H4, C5H5+, C6H62+, C7H7-, C8H8, C9H9+, TETRAHEDRON, 55(36), 1999, pp. 11143-11148
Citations number
26
Categorie Soggetti
Chemistry & Analysis","Organic Chemistry/Polymer Science
Journal title
TETRAHEDRON
ISSN journal
00404020 → ACNP
Volume
55
Issue
36
Year of publication
1999
Pages
11143 - 11148
Database
ISI
SICI code
0040-4020(19990903)55:36<11143:TSOTDO>2.0.ZU;2-U
Abstract
Triplet states of 4n pi-electron annulenes exhibit partly aromatic characte r with an increase of aromaticity as the size of the ring increases. Small effects of dearomatisation are due to bond elongation. Singlet states are a ntiaromatic. their dearomatisation is mostly due to the bond length alterna tion. Correlation analysis applied to basic indices of aromaticity (delta(H -1). NICS, HOMA and chi) practically shows the lack of any correlation in s ub-groups consisting of triplets or singlets. (C) 1999 Elsevier Science Ltd . All rights reserved.