Fluorescent and electroactive cyclic assemblies from perylene tetracarboxylic acid bisimide ligands and metal phosphane triflates

Tetraaryloxy-substituted perylene tetracarboxylic acid bisimides with one o r two 4-pyridyl receptor substituents at the imide functionality were synth esized and employed in transition metal directed self-assembly with Pd-II a nd Pt-II phosphane triflates. Upon mixing of the components, quantitative f ormation of functional molecular square-type complexes containing four dye molecules and model complexes of a 2:1 (perylene bisimide ligand:transition metal ion) stoichiometry was observed. The isolated metallosupramolecular squares were characterized by H-1 and P-31 {H-1} NMR spectroscopy as well a s conventional electrospray ionization (ESI) and ESI-FTICR mass spectrometr y. which gave evidence for the structure and the high stability of these gi ant cyclic dye assemblies (molecular weight (3a)=8172, Pt-Pt corner diagona l ca. 3.4 nm). Studies of the optical absorption and fluorescence propertie s and the electrochemistry and spectroelectrochemistry of both the perylene bisimide ligands and the perylene bisimide metal complexes show that Pt-II coordination does not interfere with the optical and electrochemical prope rties of the perylene bisimide ligands: this gives squares with high fluore scence quantum yields (Phi (P) (3a) = 0.88) and three fully reversible redo x couples. The latter could be unambiguously related to quantitative format ion of perylene bisimide radical cations (E-1/2 = + 0.93 V vs. Fc/Fc(+)). r adical anions (E-1/2 =-1.01 V vs. Fc/Fc(+)). and dianions (E-1/2 = - 1.14 V vs. Fc/Fc(+)): these redox reactions change the charge state of the cyclic assembly from + 12 to zero. In contrast. Pd-II coordination influenced the electrochemical properties of the assembly because of an irreversible pall adium reduction at E-1/2 = - 1.15 V versus Fc/Fc(+). Finally. dynamic ligan d exchange processes between different metallosupramolecular assemblies wer e investigated by multinuclear NMR and electrospray mass spectrometry. Thes e studies confirmed the reversible nature of the pyridine-Pt-II/Pd-II coord ination process.