Enhancement of band gap and birefringence induced via π-conjugated chromophore with “tail effect”

The enhancement of band gap and birefringence of template compounds can be attributed to this “tail effect” caused by the extended electronic distribution from [CO 3 ] 2− /[BO 3 ] 3− /[C 3 N 3 O 3 ] 3− to [HCO 3 ] − /[HBO 3 ] 2− /[HC 3 N 3 O 3 ] 2− .