Synthesis, crystal structure, and photophysieal properties of novel (Monophthalocyaninato)lanthanide complexes stabilized by an organometallic tripodal ligand

An unprecedented series of (monophthalocyaninato)lanthanide(III) complexes {[PcYb(L_OMe)] (3) and [(tBu)₄PcLn(L_OMe)] [Ln = Yb (4), Er (5)]} {Pc = phthalocyaninate, L_OMe = [(cyclopentadienyl) tris(dimethylphosphito)cobaltate(III)]} were prepared by the reaction of Ln[N(SiMe₃)₂]₃ [LiCl(THF)₃] _x (Ln = Yb or Er) with the corresponding phthalocyanine [H ₂Pc and H₂(tBu)₄Pc] followed by Na(L _OMe). X-ray structural analysis of 3 reveals that the Yb ³⁺ion is seven-coordinate, surrounded by four nitrogen atoms from the phthalocyaninate dianion and three oxygen atoms from the anionic tripodal LL_OMe ligand. The photophysical properties of these new mixed-metal (monophthalocyaninato)lanthanide complexes are investigated. An efficient intramolecular energy transfer from ligand-centered states to the metal ion manifold or metal-centered states takes place for the Er³⁺ complex, but there is a significant back-energy transfer for the Yb³⁺ complex. Singlet oxygen (¹O₂) phosphorescence was detected instead of the Yb³⁺ emission in the photoluminescence spectra of 3 and 4 in the NIR region, but only the Er³⁺ ion emission was observed for 5.