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   –= (η 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 ] · 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 η 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 η 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)