Bicycloaromaticity in chemistry is an extension of the concept of homoaromaticity with two aromatic ring currents situated in a non-planar molecule and sharing the same electrons. The concept originates with Melvin Goldstein who first reported about it in 1967. It is of some importance in academic research. Using MO theory the bicyclo[3.2.2]nonatrienyl cation was predicted to be destabilised and the corresponding anion predicted to be stabilised by bicycloaromaticity.
Bicycloaromaticity has been studied by others in relation to the bicyclo[3.2.2]nonatrienyl cation  and in relation to specific carbanions. In 2017 experimental evidence was reported for bicycloaromaticity (dual aromaticity) to exist in a bicyclic porphyrinoid. This system has been described as aromatic with two ring systems of 26 (n=6) and 34 (n=8) electrons. By oxidation, another system was described as a triplet-state biradical, again considered aromatic by application of Baird's rule.
- Bicyclic Baird-type aromaticity Won-Young Cha,Taeyeon Kim, Arindam Ghosh,Zhan Zhang,Xian-Sheng Ke, Rashid Ali,Vincent M. Lynch,Jieun Jung, Woojae Kim,Sangsu Lee,Shunichi Fukuzumi,Jung Su Park, Jonathan L. Sessler, Tavarekere K. Chandrashekar & Dongho Kim Nature Chemistry (2017) doi:10.1038/nchem.2834
- Bicycloaromaticity. 4m + 2, 4n rule Melvin J. Goldstein Journal of the American Chemical Society 1967 89 (24), 6357-6359 doi:10.1021/ja01000a069
- Rearrangements of bicyclo[3.2.2]nonatrienes Melvin J. Goldstein and B. G. Odell Journal of the American Chemical Society 1967 89 (24), 6356-6357 doi:10.1021/ja01000a068
- Degenerate Carbocation Rearrangements P.Ahlberg. G.Jonäll , C.Engdahl Advances in Physical Organic Chemistry Volume 19, Pages iii-v, 1-456 (1983) Edited by V. Gold and D. Bethell doi:10.1016/S0065-3160(08)60224-5
- Bicycloaromaticity. Stability and rearrangement of the bicyclo[3.2.2]nonatrienyl cation John B. Grutzner and Saul Winstein Journal of the American Chemical Society 1970 92 (10), 3186-3187 doi: 10.1021/ja00713a045
- Bicycloaromaticity. Stability and rearrangements of the bicyclo[3.2.2]nonatrienyl anion and cation John B. Grutzner and S. Winstein Journal of the American Chemical Society 1972 94 (7), 2200-2208 doi:10.1021/ja00762a008
- Homoaromaticity and bicycloaromaticity in carbanions John B. Grutzner and William L. Jorgensen Journal of the American Chemical Society 1981 103 (6), 1372-1375 doi:10.1021/ja00396a013
- Unusual bicyclic molecule extends frontier of aromaticity Katrina Krämer Chemistry World 2017 link