Thermochromism of overcrowded bistricyclic aromatic enes (BAEs). A theoretical studyElectronic supplementary information available: semiempirical and ab initio total energies of BAEs, calculated and experimental relative energies of BAEs, selected B3LYP/6-31G* geometric parameters and frontier orbital energies. See http://www.rsc.org/suppdata/cc/b1/b101797g/

Abstract

A criterion for thermochromism has been derived from ab initio DFT B3LYP/6-31G* calculations of the anti-folded, syn-folded and twisted conformations of thermochromic and non-thermochromic overcrowded bistricyclic aromatic enes (BAEs) 1–8: the thermochromic species is the twisted conformation, a necessary condition being a small energy difference, <30 kJ mol⁻¹, between the global minimum anti-folded and the thermochromic conformations.