F. Wurthner et al., Fluorescent and electroactive cyclic assemblies from perylene tetracarboxylic acid bisimide ligands and metal phosphane triflates, CHEM-EUR J, 7(4), 2001, pp. 894-902
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.