Zigzag cyclopolyacenes: a theoretical study

The zigzag type cyclopolyacenes possessing R-benzenoid rings (R = 4-16) hav e been investigated within the limitations of AM1 type semiempirical treatm ent. It has been found that all the structures considered presently are sta ble, but highly endothermic. The structure having R = 8 is notable among th e others, because it is the least endothermic one and possesses the narrowe st interfrontier energy gap. ZINDO/S type calculations, based on AM1-geomet ry-optimized structures imply that the zigzag cyclopolyacenes should be mai nly UV-active. Only a few of them (R = Jr,8) should exhibit weak absorption s in VIS-region. (C) 1999 Elsevier Science B.V. All rights reserved.