Controlled Fabrication and Optoelectrical Properties
of Metallosupramolecular Films Based on Ruthenium(II) Phthalocyanines
and 4,4′-Bipyridine Covalently Anchored on Inorganic Substrates
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Abstract
Fully conjugated metallosupramolecular
self-assembled multilayer films were controllably fabricated based
on bibenzonitril-phthalocyaninato ruthenium(II) (BBPR) and 4,4′-bipyridine
(BP) via axially coordination interaction between ruthenium ions and
the pyridine groups on the modified substrates. The substrates were
first functionalized by 4-(pyridine-4-ylethynyl)benzenic diazonium
salt (PBD) through photodecomposition of diazonium group under UV
irradiation. As a result, the pyridine-containing functional groups
were vertically and covalently anchored onto the surface of substrate
and got a stable monolayer. Soluble ruthenium phthalocyanine, axially
coordinated by labile benzonitrile groups, was used to fabricate the
layer-by-layer self-assembled films with BP through ligand-exchanging
reaction between benzonitrile and pyridine in each self-assembled
cycle. The UV–vis analysis results demonstrated the successful
fabrication of bi(4,4′-bipyridine)phthalocyaninato ruthenium(II)
(BPPR) metallosupramolecular ultrathin films with definite structures
on PBD-modified substrate. Under illumination, the BPPR self-assembled
multilayer films displayed a quick response to light. The maximum
current density reached 120 nA/cm<sup>2</sup> at six bilayers. The <i>E</i><sub>g</sub>, HOMO, and LUMO of the six-bilayer were quantitatively
measured to be 1.68, −5.29, and −3.61 eV, respectively.
This strategy supplies a facile method to get full-conjugated metallosupramolecules
and a platform for developing higher performance solar cell from the
point of adjusting dye aggregate state structure
