1,2-HOIQO - a highly versatile 1,2-HOPO analogue

A cyclic, bidentate hydroxamic acid binding unit based on an isoquinoline scaffold has been utilized for the synthesis of a hexadentate tripodal ligand based on the TREN backbone. This prototype for a new class of multidentate chelators forms mononuclear iron(III) complexes and one-dimensional coordination polymers with lanthanide(III) cations. The latter has been determined by single-crystal X-ray analysis of the cerium species. The solid-state structure in the monoclinic space group P2(1)/c (C36H34CeN7O11, a = 12.341(2) angstrom, b = 26.649(4) angstrom, c = 10.621(2) angstrom, alpha = gamma = 90 degrees, beta = 96.753(3)degrees, V = 3468.6(9) angstrom(3), Z = 4) exhibits a trigonal-dodecahedral environment around the cerium cation. The proof of concept for the versatility of the new scaffold has been shown by the modification of the crucial precursor 3-carboxyisocoumarin through electrophilic aromatic substitutions to yield the corresponding chlorosulfonated and nitrated analogues.