Efficient scrambling-free synthesis of heteroleptic terbium triple-decker (porphyrinato)(crown-phthalocyaninates)

Abstract

New heteroleptic triple-decker terbium complexes of general structure [Br₄TPP]Tb[(15C5)₄Pc]Tb[Br₄TPP] (Tb-TD) and [Br₄TPP]Tb[(15C5)₄Pc]Tb[(15C5)₄Pc] (Tb-TD*) (Br₄TPP = tetrakis-meso-(4-bromophenyl)-porphyrin, (15C5)₄Pc = tetra-(15-crown-5)-phthalocyanine) are synthesized with 48% and 57% yields, respectively. The triple-decker complexes were prepared by interaction of generated in situ terbium monoporphyrinate [Br₄TPP]Tb(acac) and corresponding double-decker precursors. The heteroleptic double-decker precursor [Br₄TPP]Tb[(15C5)₄Pc] was prepared for the first time in a two step one-pot synthesis. No ligand scrambling was observed in the synthesis of Tb-TD, while 4% scrambling was determined in the case of Tb-TD*. High yields of target triple-decker complexes were achieved despite the presence of electron-donating crown-ether fragments with low thermal stability at the phthalocyanine deck. Analysis of lanthanide-induced paramagnetic shifts of protons of Tb-TD together with data of previously reported La, Pr, Nd and Eu analogues allowed precise separation of contributions of contact and dipolar lanthanide terms as well as verification of isostructurality of complexes within the series.