1407974-59-7Relevant academic research and scientific papers
Hydrogen bonding directed supramolecular polymerisation of oligo(phenylene-ethynylene)s: Cooperative mechanism, core symmetry effect and chiral amplification
Wang, Feng,Gillissen, Martijn A. J.,Stals, Patrick J. M.,Palmans, Anja R. A.,Meijer, E. W.
, p. 11761 - 11770,10 (2012)
The design of supramolecular motifs with tuneable stability and adjustable supramolecular polymerisation mechanisms is of crucial importance to precisely control the properties of supramolecular assemblies. This report focuses on constructing π-conjugated oligo(phenylene ethynylene) (OPE)-based one-dimensional helical supramolecular polymers that show a cooperative growth mechanism. Thus, a novel set of discotic molecules comprising a rigid OPE core, three amide groups, and peripheral solubilising wedge groups featuring C 3 and C2 core symmetry was designed and synthesised. All of the discotic molecules are crystalline compounds and lack a columnar mesophase in the solid state. In dilute methylcyclohexane solution, one-dimensional supramolecular polymers are formed stabilised by threefold intermolecular hydrogen bonding and π-π interactions, as evidenced by 1H NMR measurements. Small-angle X-ray and light scattering measurements reveal significant size differences between the columnar aggregates of C3- and C2-symmetrical discotics, that is, the core symmetry strongly influences the nature of the supramolecular polymerisation process. Temperature-dependent CD measurements show a highly cooperative polymerisation process for the C3-symmetrical discotics. In contrast, the self-assembly of C2-symmetrical discotics shows a smaller enthalpy release upon aggregation and decreased cooperativity. In all cases, the peripheral stereogenic centres induce a preferred handedness in the columnar helical aggregates. Moreover, one stereogenic centre suffices to fully bias the helicity in the C2-symmetrical discotics. Finally, chiral amplification studies with the C3-symmetrical discotics were performed by mixing chiral and achiral discotics (sergeants-and-soldiers experiment) and discotics of opposite chirality (majority-rules experiment). The results demonstrate a very strong sergeants-and-soldiers effect and a rather weak majority-rules effect. Copyright
