Chirality transfer between hexaazamacrocycles in heterodinuclear rare earth complexes.

Abstract

Both the chiral hexaazamacrocyle L1 based on trans-1,2-diaminocyclohexane and the achiral hexaazamacrocyle L2 based on ethylenediamine form lanthanide(iii) dinuclear μ-hydroxo bridged complexes which have been characterized by NMR and CD spectroscopy. The homodinuclear complexes of the type [Ln2(L1)2(μ-OH)2](NO3)4 (Ln = NdIII, EuIII, TbIII and YbIII) have been synthesized in the enantiopure form and the X-ray crystal structures of NdIII, EuIII and YbIII derivatives have been determined. The heterodinuclear cationic complexes [Ln(L1)Ln'(L2)(μ-OH)2X2]n+ have been generated and characterized in solution by using the mononuclear complexes of L1 and L2 as substrates. While the formation of [LnLn'(L1)2(μ-OH)2X2]n+ dinuclear complexes is accompanied by chiral narcissistic self-sorting, the formation of [Ln(L1)Ln'(L2)(μ-OH)2X2]n+ dinuclear complexes is accompanied by the sizable sociable self-sorting of macrocyclic units. The homodinuclear complexes [Y2(L1)2(μ-OH)2X2]n+ and [Ln2(L2)2(μ-OH)2X2]n+ (Ln = DyIII, PrIII and NdIII) are CD silent in the visible region due to the lack of f-f transitions and the presence of an achiral ligand, respectively. In contrast, the heterodinuclear [Y(L1S)Ln(L2)(μ-OH)2X2]n+ complexes give rise to CD signals arising from the f-f transitions because of the chirality transfer from the L1 macrocyclic unit to the L2 macrocyclic unit.