A new organic nanoporous architecture: Dumb-bell-shaped molecules with guests in parallel channels

A new type of dumb-bell-shaped host molecule (6-8) has been synthesised, of which 1,8-bis((1)-adamantyl)-1,3,5,7-octatetrayne (8 = BAOT) forms an open porous architecture when cocrystallised with a number of typical solvent m olecules. Adamantyl substituents attached to a tetraalkyne spacer build up the walls of parallel channels wherein guest molecules are aligned. Surpris ingly, the tetraalkyne unit is significantly bent. Desolvation experiments provide evidence for a reversible inclusion of guests. In the case of the i nclusion of 2-butanone, a partial substitution by symmetrical and asymmetri cal long-chain chromophores during crystallisation was possible. Stained cr ystals showed optical frequency doubling. The crystal structure analysis re vealed a centric space group, although considerable translational and orien tational disorder was present. Application of scanning pyroelectric microsc opy revealed that the growth of inclusion compounds with 2-butanone produce d polar ordering of guest molecules, which were aligned in two macro-domain s of opposing polarity, The resulting orientation of the carbonyl dipoles i s in agreement with the theoretical prediction of a Markov model of spontan eous polarity Formation based on molecular recognition processes on growing crystal faces. The present case represents a new example of a property-dri ven supramolecular synthesis.