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 π 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]·nH₂O and H ₂(TClPP) in n-octanol at reflux, provided the first optically active protonated mixed phthalocyaninato-porphyrinato rareearth double-decker complexes [M^IIIH{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 TClPP 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 rareearth 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.