A New Organic Nanoporous Architecture: Dumb-Bell-Shaped Molecules with Guests in Parallel Channels

Abstract

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 molecules. Adamantyl substituents attached to a tetraalkyne spacer build up the walls of parallel channels wherein guest molecules are aligned. Surprisingly, the tetraalkyne unit is significantly bent. Desolvation experiments provide evidence for a reversible inclusion of guests. In the case of the inclusion of 2-butanone, a partial substitution by symmetrical and asymmetrical long-chain chromophores during crystallisation was possible. Stained crystals showed optical frequency doubling. The crystal structure analysis revealed a centric space group, although considerable translational and orientational disorder was present. Application of scanning pyroelectric microscopy revealed that the growth of inclusion compounds with 2-butanone produced polar ordering of guest molecules, which were aligned in two macro-domains of opposing polarity. The resulting orientation of the carbonyl dipoles is in agreement with the theoretical prediction of a Markov model of spontaneous polarity formation based on molecular recognition processes on growing crystal faces. The present case represents a new example of a property-driven supramolecular synthesis.

Inclusion Compounds of Diol Hosts Featuring Two 9-Hydroxy-9-fluorenyl or Analogous Groups Attached to Linear Spacer Units

“…Furthermore, the two fluorenyl groups in host 8 are connected through a linear triphenylene unit, in which each ring may rotate freely around the single bonds linking them together. Hence, the phenyl planes of the spacer unit in 8 form the dihedral angles 33.54 (6) (7), 146.69 (7), and 0.0°[ Figure 3 (b)], in this latter case satisfying the inversion symmetry of the molecule. The symmetry requirement also forces the two phenyl rings of the central diphenylene moiety of host 10 [in 10·THF (1:4), Figure 4] to be coplanar.…”

“…These include future technologies [4,5] such as the potential to accommodate guest molecules with desirable optical properties, [6,7] the separation of small molecules on the basis of size exclusion or chemical affinity, [8,9] the provision of tailored reaction environments for included molecules [10,11] to be used in chemical sensor development, [12Ϫ14] chiral separation, [15Ϫ17] and the construction of new solid materials. [18Ϫ20] This interest has stimulated the discovery of new strategies for crystalline inclusion formation and motivated the design of novel host types.…”

Supramolecular behaviour of bulky arylboranes in the crystalline state

“…In case of diborane 3 and particularly in 4, this gives rise to a molecular structure being suggestive of the so-called wheel-and-axle (26,27) or dumb-bellshaped compounds (28,29). The latter compounds are typical of their distinct behaviour to be effective clathrate hosts (15,30).…”

Polyynes

“…A series of end-capped oligoynes, in which the carbon chains are kept at a distance by bulky and spherical dendrimer endgroups with a chain length of up to 20 carbon atoms, has been synthesized by Hirsch and coworkers [39]. Apart from dendrimer end-capped oligoynes, which mainly help to stabilize the system, many different functional end-groups have been incorporated into the two ends of sp carbon chains by chemists in order to study the electronic properties and explore possible applications of this class of compounds (Scheme 10.2) [10,[40][41][42][43]. The electronic structures of organic polyynyl chains with various end-groups have been studied by Bohlmann [35,36], Walton [44,45], Hirsch [12,13,39], and Tykwinski [46,47].…”