Charge Transfer Transition for Symmetry-forbidden Charge Transfer Interaction. Theory and Experimental Verification

The group theoretical analysis of the electronic structure of l,4-dihydro-l,4-bis (dicyanoinethylene)triptycene leads to an interesting but rarely documented notion, "charge transfer transition for symmetry forbidden charge transfer interaction" , which was supported by the substituent effects on the charge transfer band shifts. The substituent effects on the charge transfer band shifts were also observed in a series of 9,lO-dihydro-9, l0-o-benzenoanthracene-l,4-diones. These results provide decisive evidence for the fact that the orbitals involved in the ground state charge transfer interaction need not be the same as those involved in the charge transfer transition. In general, charge transfer phenomena between donor and acceptor components fixed in the rigid frameworks of C2v and C5 point groups are also discussed by means of the symmetry properties of the interacting orbitals.