Constructing Sandwich-Type Rare Earth Double-Decker Complexes with N‑Confused Porphyrinato and Phthalocyaninato Ligands

Reaction of the half-sandwich complexes MIII(Pc)­(acac) (M = La, Eu, Y, Lu; Pc = phthalocyaninate; acac = acetylacetonate) with the metal-free
N-confused 5,10,15,20-tetrakis­[(4-tert-butyl)­phenyl]­porphyrin
(H2NTBPP) or its N2-position methylated analogue H­(CH3)­NTBPP in refluxing 1,2,4-trichlorobenzene (TCB) led to the
isolation of MIII(Pc)­(HNTBPP) (M = La,
Eu, Y, Lu) or YIII(Pc)­[(CH3)­NTBPP] in 8–15% yield. These represent the first examples
of sandwich-type rare earth complexes with N-confused porphyrinato
ligands. The complexes were characterized with various spectroscopic
methods and elemental analysis. The molecular structures of four of
these double-decker complexes were also determined by single-crystal
X-ray diffraction analysis. In each of these complexes, the metal
center is octa-coordinated by four isoindole nitrogen atoms of the Pc ligand, three pyrrole nitrogen atoms, and the inverted
pyrrole carbon atom of the HNTBPP or (CH3)­NTBPP ligand,
forming a distorted coordination square antiprism. For EuIII(Pc)­(HNTBPP), the two macrocyclic rings are further
bound to a CH3OH molecule through two hydrogen bonds formed
between the hydroxyl group of CH3OH and an aza nitrogen
atom of the Pc ring or the inverted pyrrole nitrogen
atom of the HNTBPP ring, respectively. The location of the acidic
proton at the inverted pyrrole nitrogen atom (N2) of the protonated
double-deckers was revealed by 1H NMR spectroscopy.