Synthetic ionophores 16. Synthesis and association behaviour of bis-pyridine tetramide macrocycles: Role of increased preorganisation on Ag + selectivity

• Published in: Tetrahedron 1997-08, Vol.53 (31), p.10841-10850
• Main Authors: Kumar, Subodh, Hundal, Maninder Singh, Hundal, Geeta, Kaur, Navneet, Singh, Harjit
• Format: Article
• Language: English
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/S0040-4020(97)00691-1

Pyridine based tetramide macrocycles ( 6–9) have been synthesized by nucleophilic displacement in pyridine-2,6-dicarbonyl dichloride with appropriate diamines. The 18-membered macrocycles 6 and 7 have well organized structures and 20-membered macrocycles 8 and 9 exist as mixtures of configurational isomers. The comparison of X-ray single crystal and energy minimized structures of previously reported diamide diester macrocycle( 1) with those of macrocycles 6, 7 and 1.AgNO 3 show that the macrocyles 6 and 7 possess type of preorganised structure attained by macrocycle 1 on complexation. This enhanced preorganisation in macrocycles 6 and 7 increases the Ag + extraction efficiency by >30% to 74 – 81% and Ag +Pb 2+ selectivity by >300% to 245 – 283 times than in 1. Pyridine based tetramide macrocycles ( 6–9) have been synthesized. The X-ray single crystal and energy minimization studies show that the enhanced preorganisation in macrocycles 6 and 7 increases the Ag + extraction efficiency by >30% to 74–81% and Ag +/Pb 2+ selectivity by >300% to 245 – 283 times than in diester macrocycle 1.