Synthesis, spectroscopic properties, and electrochemistry of heteroleptic rare earth double-decker complexes with phthalocyaninato and meso-tetrakis (4-chlorophenyl)porphyrinato ligands

A series of fourteen heteroleptic (phthalocyaninato)(porphyrinato) rare earth(m) double-decker complexes, [M^III(Pc)(TClPP)] [M = Y, La-Lu except Ce and Pm; Pc = phthalocyaninate; TClPP = meso-tetrakis (4-chlorophenyl)porphyrinate] has been prepared by base-promoted cyclization of phthalonitrile on the corresponding [M^III(TClPP)(acac)] (acac = acetylacetonate) as the template in refluxing n-octanol. The yields are highest for the mid-lanthanides, which have the optimum size to balance the stabilization due to π-π interactions and the destabilization due to axial compression of the two π systems. The whole series of double-decker complexes has been characterized by elemental analysis and a wide range of spectroscopic methods. The molecular structure of [Gd^III(Pc)(TClPP)] has also been determined. All the electronic absorption bands are dependent on the size of the metal center, suggesting that all the transitions involve molecular orbitals with contributions from both Pc and TClPP ligands. This has been supported by a systematic investigation of the electrochemical properties of the whole series of complexes. All these studies indicate that there are substantial π-π interactions and the hole is mainly localized at the Pc ligand.