Molecular Quadripod as a Noncovalent Interfacial Coupling Reagent for Forming Immobilized Coordination Assemblies

A pyrene-cored molecular quadripod
1,3,6,8-tetra­(di­(p-pyrid-4-ylphenyl)­amino)­pyrene
(TAPyr) is presented as a noncovalent
interfacial coupling reagent for the immobilization of coordination
assemblies. This bench-stable molecule is readily available and has
a quadripod shape with four pyridine legs and four pyridine handles
on the top exterior. By a simple and short dipping procedure under
ambient conditions, TAPyr is firmly immobilized on electrode surfaces
in an upright fashion as probed by electrochemical, absorption spectral,
atomic force microscopy, and scanning tunneling microscopy analysis.
Using Pd­(PhCN)2Cl2 as a metallolinker, 4-ferrocenylpyridine,
a pyridine-terminated monoruthenium complex 1, and a
diruthenium complex 2 with two pyridine ends have been
grafted onto the ITO/TAPyr surface. The obtained thin films exhibit
good electrochemical stability that is comparable or superior to those
prepared by the state-of-the-art Si–O–Sn covalent functionalization.
Appealing electrochromism is demonstrated with the thin films of ruthenium
complexes on ITO.