Tuning the Valence of the Cerium Center in (Na)phthalocyaninato and Porphyrinato Cerium Double-Deckers by Changing the Nature of the Tetrapyrrole Ligands

A series of 7 cerium double-decker complexes with various tetrapyrrole ligands including
porphyrinates, phthalocyaninates, and 2,3-naphthalocyaninates have been prepared by previously described
methodologies and characterized with elemental analysis and a range of spectroscopic methods. The
molecular structures of two heteroleptic [(na)phthalocyaninato](porphyrinato) complexes have also been
determined by X-ray diffraction analysis which exhibit a slightly distorted square antiprismatic geometry
with two domed ligands. Having a range of tetrapyrrole ligands with very different electronic properties,
these compounds have been systematically investigated for the effects of ligands on the valence of the
cerium center. On the basis of the spectroscopic (UV−vis, near-IR, IR, and Raman), electrochemical, and
structural data of these compounds and compared with those of the other rare earth(III) counterparts reported
earlier, it has been found that the cerium center adopts an intermediate valence in these complexes. It
assumes a virtually trivalent state in cerium bis(tetra-tert-butylnaphthalocyaninate) as a result of the two
electron rich naphthalocyaninato ligands, which facilitate the delocalization of electron from the ligands to
the metal center. For the rest of the cerium double-deckers, the cerium center is predominantly tetravalent.
The valences (3.59−3.68) have been quantified according to their LIII-edge X-ray absorption near-edge
structure (XANES) profiles.