β,β′-bipyrrole fusion-driven cis-bimetallic complexation in isomeric porphyrin

Abstract

An unprecedented cis-bimetallic complex of dinaphthoporphycene (DNP), namely [Pd2(μ-DNP)(μ-OAc)2], is reported. The most striking feature of this complex is that two palladiums coordinate to the macrocycle on the same side and are closely held together (Pd-Pd: 2.67 Å) by two bridging acetate ligands exhibiting significant metal-metal bonding interaction (bond order 0.18 evaluated by NBO analysis). Interestingly, replacing acetate with acetylacetonate (acac) could stabilize an unusual mono-palladium complex of DNP, where Pd coordinates unsymmetrically to two ring Ns above the macrocyclic plane, as well as coordinating with two Os of the acac ligand. Remarkably, the rigid DNP core displays enhanced complexation induced aromaticity (as per NICS and HOMA analysis), despite undergoing severe core deformation during complexation with metal ion(s) as noticed from their solid-state structures. A cis-dipalladium complex of dinaphthoporphycene (DNP) is reported, coordinating two metals on the same side of the macrocycle. Replacement of the bridging ligand leads to an unsymmetrical mono Pd sitting atop complex, where DNP acts as a bidentate ligand.