Heteroleptic phthalocyaninato-[tetra(15-crown-5)phthalocyaninato] lanthanides(III) double-deckers: Synthesis and cation-induced supramolecular dimerisation

A series of heteroleptic bisphthalocyaninates [(15C5)4Pc]M(Pc) ((15C5)4Pc = 2,3,9,10,16,17,24,25-tetrakis(15-crown-5)phthalocyaninate; Pc = unsubstituted phthalocyaninate; M = La, Sm, Dy, Tm) was synthesized. The raise-by-one-story method was applied in the cases of Sm, Dy and Tm complexes, whereas for the La complex we have developed a new synthetic approach. The complex [(15C5)4Pc]La(Pc) is the first representative of heteroleptic lanthanum diphthalocyaninates. Homoleptic counterparts M[(15C5)4Pc]2 and M(Pc)2, M = La, Sm, Dy, Tm have also been prepared for comparative studies. The UV–Vis spectral properties of all synthesized heteroleptic compounds were investigated and compared to those of the homoleptic unsubstituted and crown-substituted diphthalocyaninates. Cation-induced dimerisation of heteroleptic complexes was studied. The observed spectral effects were explained in terms of excitonic coupling between chromophoric molecules. The unsymmetrical distribution of electronic density over macrocyclic ligands is established.