Computational studies of [1]benzothieno[2,3-c]naphtho[1,2-f]quinoline.

Early NMR studies of several heterohelicenes containing an annular nitrogen atom and a thiophene ring in their structure suggested the possibility of the lengthening of the carbon-carbon bonds in the interior of the helical turn of the molecule based on the progressive more shielded nature of C resonances toward the center of the helical turn. Computational chemistry capabilities when those NMR studies were performed were primitive in comparison to what is now possible. We now report the optimized geometry and a comparison of the calculated versus observed H and C NMR chemical shift assignments for [1]benzothieno[2,3-c]naphtho[1,2-f]quinoline that confirms these suspicions.