Novel Cofacial Porphyrin-Based Homo- and Heterotrimetallic Complexes of Transition Metals.

Abstract

We present a straightforward and generally applicable synthesis route for cofacially linked homo‐ and heterotrimetallic trisporphyin complexes. The protocol encompasses synthesising the first aryl‐based, trans‐o‐phenylene trisporphyrin starting from pyrrole and benzaldehyde with an overall yield of 3.6 %. It also allows investigating the respective cis‐isomer as the first conformationally restricted planar‐chiral trisporphyrin. The free‐base ligand was used in subsequent metalation reactions to afford the corresponding homotrimetallic Mn(III)‐, Fe(III)‐, Ni(II)‐, Cu(II)‐, Zn(II)‐ and Pd(II) complexes – additionally, a small adaptation of the protocol resulted in the defined Ni(II)Fe(III)Ni(II) complex in a total yield of 2.3 %. By monitoring Ni(II) insertion into the empty trimeric ligands, we affirmed that the outer porphyrin rings are filled before the internal ring. The molecular species were characterised by 1H NMR, UV‐Vis, photoluminescence, IR, MS, CID, and high‐resolution IMS measurements.