A theoretical and experimental study of the racemization process of hexaaza[5]helicenes

A dynamic 1H NMR study, together with DFT calcns., of bis-([1,2,3]triazolo)[1,5-a:5',1'-k][1,10]phenanthroline 2 has allowed to identify the ring and open forms of a new example of ring/chain tautomerism, as well as their interconversion barriers (ring/ring and ring/open). The barrier of the exchange process between the chain forms and the ring form was found higher than the 'racemization' process in the closed form, so the ring opening does not contribute to the 'racemization'. The di-1,10-Me and di-1,10-iodo derivs. have been prepd. and their properties calcd