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

Abstract

A new type of dumb-bellshaped host molecule (6 ± 8) has been synthesised, of which 1,8-bis((1)-adamantyl)-1, 3,5, 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.

Adamantyl‐endcapped polyynes

“…Removal of the acetone protecting group was effected by treatment with KOH at high temperature, yielding adamantyl diyne 12 . Although dimerization of monoyne 4 under Hay conditions proved difficult, the dimerization of diyne 12 proceeded efficiently, giving tetrayne 1c as a crystalline white solid in quantitative yield …”

“…The stability of tert ‐butyl‐endcapped polyynes suggested that a variation of this structure might be a viable target, that is, the adamantyl group ( 1a , 1b , 1c , 1d , 1e , 1f , 1g , 1h , 1i , 1j ). Although 1c has been studied quite substantially as a substrate for solid‐state host guest systems, little is known about the electronic and structural aspects of other members of this series. We report herein on the synthesis of 1a , 1b , 1c , 1d , 1e , 1f , 1g , 1h , 1i , 1j and their physical and spectroscopic characterization.…”

End-Cap Stabilized Oligoynes: Model Compounds for the Linear sp Carbon Allotrope Carbyne

“…[5d,e, 8±10, 12±14, 22c] As polymerization of polyacetylenic compounds can be considered as a function of the distance between such molecules, [11] we consequently decided to build up dumb-bell-shaped systems ( Figure 2) where the carbon chains are kept at a distance by bulky, spherical end groups. [28,29] For this purpose, dendrimers [30] seemed to be the most suitable choice. Ideally, they are perfect monodisperse macromolecules with a regular and highly branched three-dimensional architecture, such as Fre ¬ chet×s aromatic polyether dendrimers which are easily accessilbe through convergent procedures.…”

“…In the last step, 29 and 28 were obtained without any losses by the cleavage of the silylic OH protecting groups. As we were unsure about the kinetic stability of the 3,5-dihydroxyphenylacetylene (28) under the following basic reaction conditions (Scheme 4), we worked towards for the TIPS protected derivative 29, in parallel.…”

Functional Porous Structures Based on the Pyrolysis of Cured Templates of Block Copolymer and Phenolic Resin

“…Typically, nanoporous materials are crystalline framework solids, such as zeolites, discotic molecular assemblies, [31][32][33] or "robust" molecular crystals formed using supramolecular [38] design principles. [2,[11][12][13][14][15][16][17][18][19][20] These materials can have large void volumes and high internal surface areas, but the supramolecular materials often tend to collapse upon emptying the pores. Several approaches have also been presented to prepare mesoporous and macroporous materials, such as "track-etching", [4][5][6] using honeycomb structures, [27][28][29] and emptying nanostructured templates (e.g., sol-gel processing of surfactants or block copolymers, [7][8][9][10] selective degradation of material with UV exposure, [24][25][26] pyrolysis, [21][22][23]34] and selective removal of lowmolecular-weight amphiphiles (combs) from hierarchically self-assembled polymeric comb-coil supramolecules [35,36] ).…”