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Efficient Synthesis of Calix[4]phyrins Catalyzed by Amberlyst™-15 and Its Noncovalent Interactions with Neutral Molecules

[ Vol. 21 , Issue. 26 ]

Author(s):

Anchal Singhal* and Shive M.S. Chauhan*   Pages 2690 - 2696 ( 7 )

Abstract:


Background: Calix[4]phyrins are fascinating hybrid molecules that contain a mixture of sp2- and sp3- hybridized meso-carbon bridges and bear analogy to both porphyrins and calix[4]pyrroles and hence find use in various applications. Various methods have been reported in the literature for the synthesis of calix [4] phyrins but with disadvantages of using corrosive acids and getting mixture of products, the separation of which is tedious. Hence, mild synthetic route for synthesis of calix[4]phyrins is highly desirable.

Objective: Mild and efficient synthesis of calix[4]phyrins and their binding studies with neutral molecules are presented in this manuscript.

Methods: Various functional calix[4]phyrins were synthesized by the condensation reaction of acetone with various functional dipyrromethanes catalyzed by reusable heterogeneous Amberlyst™-15 at ambient temperature followed by oxidation with DDQ. Different solvents were used as reaction medium to optimize the yield of calix[4]phyrins. Non-covalent interactions of 5,15-di-(p-methoxyphenyl)-10,10,20,20-tetramethylcalix[4] phyrin with p-nitrophenol and p-nitrotoluene were studied using UV-Vis spectrophotometer.

Results: Amberlyst™-15 acts as an efficient catalyst for the synthesis of calix[4]phyrins in moderate to good yields. Dichloromethane was found to be best suitable solvent for the synthesis of calix[4]phyrins. In the UVVis studies of 5,15-di-(p-methoxyphenyl)-10,10,20,20-tetramethylcalix[4]phyrin with p-nitrophenol as well as with p-nitrotoluene, two clear isobestic points were observed in each spectra showing that two molecules are interacting with each other.

Conclusion: An efficient method is developed to synthesize a parallel library of calix[4]phyrins. Non-covalent interactions between 5,15-di-(p-methoxyphenyl)-10,10,20,20-tetramethylcalix[4]phyrin as neutral donor and aromatic nitro compounds as neutral acceptors are established by UV-Vis studies.

Keywords:

Acetone, dipyrromethane, amberlyst™-15, calix[4]phyrin, calix[6]phyrin non-covalent interactions, absorption studies.

Affiliation:

Department of Chemistry, University of Delhi, Delhi 110 007, Department of Chemistry, University of Delhi, Delhi 110 007

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