Studies of "pinwheel-like" bis[1,8,15,22-tetrakis(3-pentyloxy)-phthalocyaninato] rare earth(III) double-decker complexes

Abstract

Homoleptic bis(phthalocyaninato) rare-earth double-deckers complexes [M-III{Pc(alpha-OC5H11)(4)}(2)] (M=Eu, Y, Lu; Pc(alpha-OC5H11)(4)=1,8,15,22-tetrakis(3-pentyloxy)phthalocyaninate) have been prepared by treating the metal-free phthalocyanine H2Pc(alpha-OC5H11)(4) with the corresponding M(acac)(3)(.)nH(2)O (acac = acetylacetonate) in refluxing n-octanol. Due to the C-4h symmetry of the Pc(alpha-OC5H11)(4) ligand and the double-decker structure, all the reactions give a mixture of two stereoisomers with C-4h and D-4 symmetry. The former isomer, which is a major product, can be partially separated by recrystallization due to its higher crystallinity. The molecular structure of the major isomer of the Y analogue has been determined by single-crystal Xray diffraction analysis. The metal center is eight-coordinate bound to the isoindole nitrogen atoms of the two phthalocyaninato ligands, forming a distorted square antiprism. Such an arrangement leads to an interesting "pinwheel" structure when viewed along the C-4 axis, which assumes a very unusual S-8 symmetry The major isomers of all these double-deckers have also been characterized with a wide range of spectroscopic methods. A systematic investigation of their electronic absorption and electrochemical data reveals that the pi-pi interaction between the two Pc(alpha-OC5H11)(4) rings is weaker than that for the corresponding unsubstituted or beta-substituted bis(phthalo-cyaninato) analogues.