Bond orders in trans-stilbene in excited singlet and triplet states

The Fulvalenes

“…[173] Comparisons of singlet biradical and zwitterionic states in the planar and 90°twisted forms allows for predictions on the relative stabilities of the two states from the degree of polarisation in the planar structure. [125] The excitation of calicene is associated with considerable molecular charge transfer [174] and the electro-optical absorption spectrum of tetrachlorodiphenyl 74 (see Scheme 14) has been examined. [175] There is now little doubt that the molecules display partial aromatic behaviour in the ground state and antiaromatic character in the excited singlet states [123] with clear similarities to the sesquifulvalenes.…”