Synthesis and structure-property relationships of donor/acceptor-functionalized bis(dehydrobenzo[18]annuleno)benzenes

Seven new bis(dehydrobenzo[18] annuleno)benzenes (bis[18]DBAs) 1-7 functionalized with electron-donating dibutylamino groups and/or accepting nitro groups at various positions along the peripheries of the chromophores have been prepared. The effects of varying the donor/acceptor charge transfer pathways, chromophore lengths and molecular symmetries upon the optical band gaps are studied using UV-visible spectroscopy, and structure-property correlations are identified. It is found that bis[ 18] DBAs possessing donor-p-donor and acceptor-p-acceptor pathways exhibit the smallest band gaps, especially when an acceptor-p-acceptor pathway is situated along the longest chromophore length in the molecule. The all-donor species 1 is also found to exhibit efficient fluorescence with dramatic solvatochromism. The results may have value to the rational design of future NLO/TPA device components.