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 P21/c (C36H34CeN7O11, a = 12.341(2) Å, b = 26.649(4) Å, c = 10.621(2) Å, α
= γ = 90°, β = 96.753(3)°, V = 3468.6(9) Å3, 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.