A quantum chemistry study of diethynyl benzene macrocycles: Structural and electronic properties

The geometric and electronic structures of a series of diethynyl benzene macrocycles (DBMs) in neutral, cationic, and anionic states have been studied theoretically by density functional theory at the B3LYP level. The results show that the model molecules may have planar conformation in both neutral and ionic states. However, bigger macrocycles, for example, 7DBM and 8DBM, the charge states result in more energy minima. The most energetically favored conformation also shows charge state dependence. In addition, electronic structure analysis demonstrates an odd-even difference behavior of LUMO-HOMO gap for the planar DBMs in both neutral and ionic states. (C) 2008 Elsevier B.V. All rights reserved.