Optically active mixed phthalocyaninato-porphyrinato rare-earth double-decker complexes: Synthesis, spectroscopy, and solvent-dependent molecular conformations

Reaction between the optically active metal-free phthalocyanine with a pi system with noncentrosymmetrical C-2v symmetry ((S)- and (R)H-2{Pc(OBNP)(2)}; OBNP=binaphthylphthalocyanine) and half-sandwich complexes [M-III(acac)(TClPP)] (M=Y, Eu; TClPP = meso-tetrakis(4-chlorophenyl)porphyrinate; acac=acetylacetonate), which were generated in situ from [M(acac)(3)]center dot nH(2)O and H-2(TClPP) in n-octanol at reflux, provided the first optically active protonated mixed phthalocyaninato-porphyrinato rare-earth double-decker complexes [(MH)-H-III{Pc(OBNP)(2)}(TClPP)] (M = Y, Eu) in good yield. In addition to electronic absorption spectroscopy and magnetic circular dichroism results, circular dichroism shows different spectroscopic features of these mixed-ring rare-earth double-decker compounds in different solvents, such as DMF and CHCl3, which was well-reproduced on the basis of time-dependent density functional theory calculation results for the yttrium species (S)-[Y-III{Pc(OBNP)(2)}(Por)](-) (Por=porphyrinate, which is obtained by removing the four chlorophenyl groups from the TCIPP ligand) in terms of the change in the rotation angle between the two macrocyclic ligands in the double-decker molecules. These results revealed the solvent-dependent nature of the molecular conformation of mixed-ring rare-earth double-decker complexes, which suggests a new way of tuning the optical and the electrochemical properties of sandwich-type bis(tetrapyrrole)metal double-decker complexes in solution by changing the solvent.