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Dr. WONG, Raymond W.Y.
Research Program
Luminescent Organic and Organometallic Polymers
The growing interest in conjugated polymers stems from the fact that this new
class of materials finds applications in polymer light-emitting diodes (PLED).
An identified problem in such devices is the ratio of 3:1 for the generation
of non-emissive triplet to emissive singlet excitons. To address this issue,
conjugated polymers containing transition metal atoms such as platinum have
been widely studied by us as model systems to explain aspects of the photophysics
of excited states in such polymers and obtain a clear picture of the spatial
extent of the singlet and triplet manifolds [1- 6]. The strong spin-orbit coupling
associated with these heavy metals renders the spin-forbidden triplet emission
(phosphoresecence) partially allowed. This project involves the design and synthesis
of soluble luminescent rigid-rod metal-containing poly-yne polymers and their
photophysical, redox and photoconducting properties will be studied. We envisioned
that utilization of luminescent organometallic materials of this kind can harvest
energy from triplet excitons and there is a great potential of using these materials
in photocells and as electrophosphoresecent emitters in high-efficiency PLED.
The structural factors that determine the photophysical and optoelectronic properties
of these materials are being investigated. Efforts are also initiated in our
laboratory to synthesize and characterize some structurally similar conjugated
organic polymers. In this way, a more general understanding of the influence
and importance of the metal centre in these organometallic systems, through
comparison with the organic counterparts, can be obtained.
Luminescent Transition Metal Acetylide Compounds
There is a continuing interest in the design of transition metal alkynyl complexes
owing to the potential applications of these molecules in many areas of materials
science and crystal engineering. The rich photochemistry associated with this
class of luminescent complexes has also aroused much attention in the development
of optoelectronic devices. The project focuses on the molecular design and synthesis
of soluble luminescent metal acetylides of late transition metals such as Pt(II),
Au(I), Hg(II), Ru(II), Os(II) and of polynuclear metal cluster cores [7 - 9].
The photophysical and electrochemical behavior will be investigated together
with their solid-state structures. Attempts are also made to extend the systems
to oligomeric and polymeric structural motifs.
Carbon-rich Organometallic Materials
There is a flurry of interest in the research community in the development
of carbon-rich bi- or multi-metallic assemblies containing p-conjugated
chains. It has been demonstrated that molecular wires comprising mixed-valence
bimetallic fragments or remote redox-active organometallic building blocks linked
by all-carbon chains could be used in molecular electronics, optoelectronic
devices and chemical sensing applicances. In our research efforts, particular
emphasis is placed upon the chemistry of oligoacetylenic ferrocenyl complexes.
We are currently studying homometallic and heterometallic alkynyl complexes
end-capped with ferrocenyl entities which contain conjugated organic bridges
(e.g. oligothiophene, fluorenes, etc.) [10, 11]. The electronic communication
within the system will be studied by electrochemical methods. Electronic and
redox properties will be examined as a function of the chain length and nature
of the spacer group and the data are compared with the results obtained from
theoretical studies. So far, we are able to structurally characterize some novel
molecules with a metal-metal through-space distance of several nanometers which
may find potential nanotechnological applications.
Transition Metal Cluster Chemistry
We are developing rational synthetic routes to new transition metal carbonyl
clusters of various nuclearities and analyzing their potential as catalyst precursors.
Reactions of these clusters with oligo- and poly-ynes as well as other unsaturated
organic ligands are under active investigation in the pursuit of new methodologies
for metal-mediated organic synthesis [12, 13]. Considerable effort is also devoted
to the reactivity studies of phosphine ligands with additional donor sites towards
metal clusters [14]. The interesting structural features of new molecules will
be studied by X-ray crystallography. The relationship between their structures
and chemical properties will be established.
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