Synthesis and study of new biomimetic calix[6]tren based complexes

More than 30% of enzymes present a metal ion in their active site that is key forcatalysis. Interesting sub-families present a mononuclear active site where a single metal ion(Zn2+ or Cun+) is coordinated to a polyhistidine core. The elaboration of model compounds isimportant for understanding the fundamental mechanisms involved in their bio-catalyticcycles.1 We have developed calix[6]arene based ligands presenting an aza cap covalentlylinked to the calixarene moiety, which offers a metal coordination site and a well-definedhydrophobic cavity. This assembly allows and controls exogenous ligand binding to a metalcenter. One of these ligands, calix[6]tren (1), shows versatile host-guest properties oncecomplexed to Cun+ but is also a remarkable receptor for ammonium ions and polar neutralmolecules,2 as well as a trigger for host/guest interconverion3 and for dioxygen activation.4The development of efficient synthetic methodologies for the selective functionalization ofcalix[6]tren is now required in order to tune its properties by the modification of thecoordination sphere of the metal and by obtaining surface graftable analogues that can bestudied in water.For these purposes, different calixarenes were synthesized:- A “two-story” calix[6]amidotren (2) to expand the available space underneath thecap to allow simultaneous coordination of several guests and to study its catalytic properties;- A calix[6]tren-trisPhOH (3) amending the first and second coordination sphere of themetal in order to study its effects on coordination and reactivity;- A calix[6]tren decorated with an arm on the cap bearing an azide function (4) inorder to be immobilized on the surface and study its properties in water: these functionalizedsurfaces will present unique electrocatalytic and redox detection properties in aqueousmedium.Synthesis, complexation, characterization and electrochemical behavior of thedifferent compounds in solution and immobilized on surface will be presented and discussed.0