Mixed (phthalocyaninato)(porphyrinato) rare earth double-decker complexes with C₄ chirality: Synthesis, resolution, and absolute configuration assignment

Mixed (phthalocyaninato)(porphyrinato) rare earth double-decker complexes [HM^III{Pc(α-3-OC₅H₁₁)₄}{TOAPP} ] [Pc(α-3-OC₅H₁₁)₄ = 1,8,15,22- tetrakis(3-pentyloxy)-phthalocyaninate; TOAPP = meso-tetrakis(4-octylamino- phenyl)porphyrinate; M = Y (1), Ho (2)] were prepared as a racemic mixture by treating metal-free phthalocyanine H₂Pc(α-3-OC ₅H₁)₄ with half-sandwich complexes [M ^III(acac)(TOAPP)], generated in situ from M(acac)₃- nH₂O and H₂TAPP [TAPP = meso-tetrakis(4-amino-phenyl) porphyrinate], in refluxing 1-octanol. The obtained double-deckers were characterized by elemental analysis and various spectroscopic methods. The molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction analysis. The compounds crystallize in the triclinic system with a pair of enantiomeric double-deckers per unit cell. Resolution of 1 and 2 was achieved using a chiral HPLC technique combined with the formation of their diastereomeric mixture using L-Boc-Phe-OH as the chiral resolving agent, yielding for the first time the pure diastereoisomers of chiral mixed (phthalocyaninato)(porphyrinato) rare earth double-decker complexes with C ₄ symmetry. The absolute configuration of these chiral complexes was assigned by comparing the experimental circular dichroism spectrum with a simulated one on the basis of time-dependent density functional theory calculations.