Published on Web 05/12/2004
Luminescent Organoboron Quinolate Polymers
Yang Qin, Cynthia Pagba, Piotr Piotrowiak, and Frieder Ja¨kle*
Contribution from the Department of Chemistry, Rutgers UniVersity-Newark, 73 Warren Street,
Newark, New Jersey 07102
Received October 20, 2003; E-mail: fjaekle@andromeda.rutgers.edu
Abstract: The synthesis of well-defined luminescent organoboron polymers via a novel three-step procedure
starting from silylated polystyrene is reported. Highly selective borylation of poly(4-trimethylsilylstyrene)
(PS-Si), followed by replacement of the bromine substituents in poly(4-dibromoborylstyrene) (PS-BBr) with
substituted thienyl groups (R ) H, 3-hexyl, 5-hexyl), and final introduction of the 8-hydroxyquinolato moiety
yields a series of new organoboron quinolate polymers in 67-83% isolated yield. The hexyl-substituted
polymers are highly soluble and solution-processable yielding thin films that efficiently emit light at 513-
514 nm upon excitation at 395 nm.
Chart 1
Introduction
Organoboron quinolates are an important class of compounds
that have found widespread applications in the identification
of chiral boron catalysts,1 in trace metal analysis via fluorescent
response,2 and as fungicides, bacteriocides, and antibiotics.3
However, it is their luminescence that has recently attracted a
great deal of interest. Aluminum quinolates (AlQ3, Chart 1) and
related derivatives were first reported by Tang and VanSlyke
in 1987 to possess electroluminescent properties and are
currently widely used as materials for emission and electron-
conduction layers in organic light-emitting devices (OLEDs).4
The recent discovery by Wang and co-workers5 that certain
organoboron quinolates such as Ph2BQ show efficient lumi-
nescence while at the same time providing good stability
revitalized research into boron quinolates and related species.6-8
Boron and aluminum quinolates are currently applied in
device fabrication via vacuum deposition techniques. Solution
processing methods including ink-jet printing techniques, on the
other hand, receive more and more attention as a potential low-
cost alternative.9 Incorporation of the inorganic component into
polymer structures may therefore provide new possibilities.
However, only recently have the first reports on the synthesis
of AlQ3- and RAlQ2-substituted polymers appeared in the
literature,10 and boron quinolate polymers have to our knowledge
not been described previously.
Several methods for the synthesis of organoboron quinolates
are available. Most commonly used are the exchange of an
alkoxy substituent OR′ in diorganoalkoxyboranes R2BOR′ and
the ester formation from organoborinic acids R2BOH.11 Alter-
natively, alcoholysis of a triorganoborane R3B may be per-
formed, upon which one of the organic substituents R is cleaved
selectively by the 8-hydroxyquinoline (HQ) to yield the desired
product R2BQ.3a,5b This approach is particularly useful when
diorganoalkoxyboranes or organoborinic acids are not readily
available, and we thus decided to apply it to the synthesis of
organoboron quinolate polymers from organoboron polymers.
We report here on the facile synthesis of the first organoboron
quinolate polymers via a novel modular approach that will allow
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Wu, Q.; Esteghamation, M.; Hu, N.-X.; Popovic, Z.; Enright, G.; Tao, Y.;
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ligands, see: Wang, S. Coord. Chem. ReV. 2001, 215, 79.
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Calvert, P. Chem. Mater. 2001, 13, 3299.
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T.; Dodelet, J.-P. J. Polym. Sci., Part A: Polym. Chem. 2000, 38, 2887.
(b) Enomoto, K.; Wadokoro, J. JP Patent 2000239318, 2000. (c) Meyers,
A.; Weck, M. Macromolecules 2003, 36, 1766.
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10.1021/ja039133l CCC: $27.50 © 2004 American Chemical Society
J. AM. CHEM. SOC. 2004, 126, 7015-7018
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