Constructing bis(porphyrinato) rare earth double-decker complexes involving N-confused porphyrin

Abstract

Reaction of metal-free N-confused 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin (H₂NTClPP) with metal-free 5,10,15,20-tetrakis[(4-tert-butyl)phenyl]porphyrin (H₂TBPP) in the presence of M^III(acac)₃·nH₂O (acac = acetylacetonate) in refluxing 1,2,4-trichlorobenzene (TCB) led to the isolation of heteroleptic bis(porphyrinato) rare earth compounds M^III(HNTClPP)(TBPP) (M = La, Pr) (1, 2) in 6.7–10% yield. These represent the first examples of sandwich-type porphyrin rare earth double-decker complexes that involve N-confused porphyrin ligand. Different from their homoleptic bis(porphyrinato) rare earth double-decker counterparts HM^III(TBPP)₂ (M = La, Pr) (3, 4), the acidic proton in the heteroleptic analogues was revealed to localize at the inverted pyrrole nitrogen atom of the N-confused porphyrin ligand on the basis of NMR spectroscopic studies. Nevertheless, their heteroleptic bis(porphyrinato) sandwich molecular nature was confirmed on the basis of single crystal X-ray diffraction analysis over the praseodymium double-decker complex.