Sandwich quadruple-decker binuclear lanthanide(III) complexes based on clamshell-type phthalocyanine ligand: synthesis and physicochemical studies

Abstract

A series of heteroleptic quadruple-decker bis[lanthanide(III)] complexes based on a flexible spacer-linked phthalocyanine ligand of clamshell-type, denoted sandwich-clamshell complexes, have been prepared. Complexation of 1,1’-[benzene-1,2-diylbis(methanediyloxy)]-bis[9(10),16(17),23(24)-tri-tert-butylphthalocyanine] (clam,tBuPc2H4, 1) with [2(3),9(10),16(17),23(24)-tetra-tert-butylphthalocyaninato] lanthanide(III) acetates [tBuPcLnOAc, 2a–d; Ln = Eu (a), Gd (b), Tb (c), Lu(d)] afforded quadruple-deckers clam, tBuPc4Ln2 (3a–d) with good to excellent yields. The complexes reveal intrinsic UV–Vis–NIR absorption by analogy to classical double-decker phthalocyaninates, while demonstrating high thermal stability up to 350 °C. At the same time, a combination of 1H NMR, electrochemistry and SQUID magnetometry supported by DFT theoretical calculations indicates that bis(phthalocyanine) subunits in 3 are in close contact mainly governed by the spacer group and, in some extent, by the presence of bulky tert-butyl peripheral substituents in the four phthalocyanine decks.