Theoretical Studies of Structures and Conformational Analysis of Anthracene-2,7-diyl Cyclic Oligomers

Abstract

Abstract The structures and conformation of anthracene-2,7-diyl cyclic oligomers were investigated by DFT calculations. The energy minimum and transition state structures of the oligomers ranging from pentamer to nonamer were optimized at the M05-2X/6-31G(d) level. The mechanisms of conformational interconversion were analyzed on the basis of the calculated structures and the thermodynamic energies. The number of structures and the conformational flexibility rapidly increased with increasing ring size. In the stable structures, the dihedral angles between the anthracene units were ca. ±40° or ±140°, and the obtuse angles appeared only in large oligomers. We estimated the cavity size of the cyclic oligomers from the calculated structures and their strain energies by thermochemical calculations of the homodesmotic reactions.