Synthesis, structure and spectroscopic properties of lanthanide complexes of N-confused porphyrins

A series of meso-substituted N-confused porphyrins (NCP) is synthesized using the modified Rothemund-Lindsey procedure. Lanthanide N-confused porphyrinate complexes of the general formula [(NCP)Ln(L(OMe))] [Ln(3+) = Yb(3+) and Er(3+); L(OMe-) = (eta(5)-C(5)H(5))Co(P(=O)(OMe)(2)}(3)-] are obtained in moderate yields upon interaction of N-confused porphyrin free bases (H(2)NCP) with Ln[N(SiMe(2))(3)]center dot x[LiCl(THF)(3)], followed by the addition of the tripodal anion L(OMe)- as an effective encapsulating agent for the lanthanide ions. The structural and spectroscopic data for these complexes provide evidence for an eta(2)-agostic interaction between the Ln(3+) ion and the inner C-H bond of the NCP ligand. Methylation of [(NCTCPP)Yb(L(OMe))] (H(2)NCTCPP = 2-azo-5,10,15,20-tetracyanophenyl-21-carbaporphyrin) with methyl iodide yields the novel stable lanthanide complex of the N-methylated derivative of N-confused porphyrins, whose X-ray structure also exhibits an eta(2)-agostic interaction between the metal center and the inner C-H bond of the NCTCPP ligand. The photophysical properties of the N-confused porphyrins and their lanthanide complexes are investigated. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).