The tert-butyl amide macrocycle containing ethylene glycol moiety (cMDG) was constructed starting from 5-tert-butylisophthalic acid 1 which was activated to acid chloride derivative 2 using thionyl chloride in toluene. Further, the synthesis of the second macrocycle based on pyridine framework (cMP) was achieved in similar way before coupled to the diamine derivative 4. Following that, the compound’s electronic structure was calculated using simple molecular mechanics calculation to represent the preferable conformation of these macrocycles. In order to evaluate the influence of the benzene ring in the framework of both macrocycles to complex the guests, the following binding experiments were carried out with the synthesized maleimide 5 and CF3 maleimide 6. An equimolar mixture of macrocycle cMDG and maleimide 5 or 6 in CdCl3 was prepared and analysed by1H and19F NMR spectroscopy, respectively. The similar binding experiments were then carried out with macrocycle cMP. The association constant, Ka for the complexation of pseudorotaxane [cMDG·5] and [cMP·5] were estimated to be 190 ± 20 M-1 and 160 ± 20 M-1, respectively. On contrary, the association constant for the complexation of pseudorotaxane [cMDG·6] and [cMP·6] complexes were enhanced with a Ka value of 1000 ± 100 M-1 and 460 ± 50 M-1 at 25 °C in CdCl3. In addition, the1H and19F NMR spectra of these macrocycles and maleimides showed complexes are in slow exchange on the1H NMR chemical shift timescale. This can be attributed to significant binding events of pseudorotaxane complexes, compare to the free species observed in isolation. In the case of slow exchange, the Ka was determined using the single-point method.
|Translated title of the contribution||Synthesis and binding properties of tert-butyl amide macrocycles for pseudorotaxanes formation|
|Number of pages||13|
|Journal||Malaysian Journal of Analytical Sciences|
|State||Published - Aug 2019|
- Ethylene glycol
ASJC Scopus subject areas
- Analytical Chemistry