Structural studies of the whole series of lanthanide double-decker compounds with mixed 2,3-naphthalocyaninato and octaethylporphyrinato ligands

The molecular structures of a series of nine mixed (2,3-naphthalocyaninato)(octaethylporphyrinato) double-decker complexes of lanthanide(III), M(Nc)(OEP) (M = La, Pr, Nd, Tb, Dy, Ho, Er, Tm, Yb), have been determined by single-crystal X-ray diffraction analysis. All these compounds together with the Sm, Eu, Gd, Y, Lu and Ce analogues, whose structures have been solved previously, crystallize in the same orthorhombic system, Pnma, Z = 4. The molecular structures of all these compounds are isostructural, exhibiting a slightly distorted square antiprismatic geometry with two domed ligands. The metal centre of M( Nc)( OEP) is coordinated by eight nitrogen atoms from the isoindole and pyrrole of the Nc and OEP rings, respectively. The ring-to-ring separation between the two domed ligands, as defined by the two N-4 mean planes, decreases monotonically from 3.056 to 2.652 Angstrom along the series of La to Lu as a result of lanthanide contraction. This interplanar distance as well as the average M-N(Nc) and M-N( OEP) bond lengths of M(Nc)(OEP) (except M = Ce) show a linear relationship with the ionic radius of the metal centre. The skew/twist angle between the two macrocyclic rings remains almost unchanged, ca. 45degrees, for the whole series of lanthanide complexes, regardless of the size of the metal centre.