Polyimides based on rhenium(I) diimine complexes - Polyimides and Other High Temperature Polymers - page 89

Polyimides based on rhenium(I) diimine complexes

LILLIAN SZE MAN LAM, 1 WAI KIN CHAN ∗ ,1 and A.B. DJURIŠIĆ 2
1 Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
2 Department of Electrical and Electronic Engineering and Department of Physics,
The University of Hong Kong, Pokfulam Road, Hong Kong, China

Abstract—Polyimides with significantly enhanced photoconductivity were synthesized by the po-
lymerization of a rhenium tricarbonyl complex with various aromatic dianhydrides. The rhenium
complex acted as the photosensitizer in the visible region. Electronic absorption spectra of the
polymers showed a very strong intramolecular charge transfer transition and a large photocurrent re-
sponse was observed. The photocharge generation process was studied by simulating the experimen-
tal quantum yield with the Onsager's theory, which indicated that the primary yield and the ther-
malization distance were of the order of 10 -4 and 1.7 nm, respectively.

Keywords : Polyimide; rhenium diimine complex; photoconducting polymers; photosensitivity.

1. INTRODUCTION

Our research effort has been continuously focused on the synthesis of metal-
containing polymers and their applications as opto-electronic materials. By incor-
porating different metal complexes into the polymer main chain, we were able to
make use of the interesting photosensitivity/emissive properties of the metal com-
plex moieties. The metal complexes can be attached to the polymer main chain or
as the pendant group [1-6]. In our previous papers, we reported on the syntheses
of different polyimides with bis(terpyridyl) ruthenium [7], diazacrown ether [8]
(Figure 1), or rhenium diimine complexes [9]. Some preliminarly results on their
photoconductivity and light emitting properties were also presented. In this paper,
we report a detailed study of the photocharge generation process in a polyimide
functionalized with chlorotricarbonyl 1,4-diaza-1,3-butadiene (DAB) rhenium(I)
complex. Complexes of the type fac-[Re(X)(CO) 3 ( -diimine)] (X = Cl, Br, CH 3 )

possess low lying excited states with metal-to-ligand charge transfer (MLCT)
character [10-12]. They are very promising photooxidants, photosensitizers and
photo- and electro-catalysts [13-16]. The fabrication of light emitting devices
based on these complexes was also reported [17, 18]. Compared to other aromatic

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