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This paper reports detailed synthesis and characterization of a hybridized polymer system which combines the ionic transition metal complexes and a conjugated polymer backbone bearing NLO chromophores to manifest a large photorefractive (PR) effect. In this system, the conjugated polymer backbone was chosen to play the dual role of a transporting channel for the charge carriers and a macroligand to chelate with the transition metal complex. Ru(II)-tri(bispyridyl) complexes were chosen as the photocharge generator by utilizing their metal-to-ligand charge transfer properties. The Heck coupling reaction was applied to synthesize these multifunctional polymers. A large net optical gain (>200 cm -1 ) at a zero electric field was observed on poled samples. The synthetic approach is versatile and was extended to the synthesis of PR polymers containing Os complexes. The resulting polymer showed photorefractivity at a wavelength in the near IR region (780 nm). This approach also offers the opportunity to fine-tune the electronic properties of polymers through modification of the polymer structures. Model reactions were studied to elucidate the structural defects caused by the side reactions in the Heck reaction. The effects of these defects on the PR performance of these polymers were evaluated. It was demonstrated that eliminating these defects could enhance the photorefractive response time. X

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-conjugated polymers for use in organic light-emitting diodes, Nature 405 (2000), 661-665. 5 DETERMINATION OF CONDUCTOR LOSS OF MULTILAYER-COUPLED MICROSTRIP LINES FOR CAD APPLICATION

The optical and photophysical properties of phenylacetylene dendritic macromolecules based on unsymmetrical branching are investigated using steady-state and time-dependent spectroscopy. Monodendrons, up to the fourth generation, are characterized with and without a fluorescent perylene trap at the core. The higher generation monodendrons without the perylene trap exhibit high molar extinction coefficients (>10(5) M(-1) cm(-1)) and high fluorescence quantum yields (65-81%). When a perylene trap is placed at the core, then the monodendrons typically exhibit high energy transfer quantum yields (approximately 90%), as well as subpicosecond time scale excited-state dynamics, as evidenced by ultrafast pump-probe measurements. The photophysical properties of the unsymmetrical monodendrons are compared to those of phenylacetylene monodendrons with symmetrical branching, which have been described recently. The high fluorescence quantum yields and large energy transfer quantum efficiencies exhibited by the unsymmetrical monodendrons suggest they have potential for applications in molecular-based photonics devices.

Hexamolybdate clusters have been covalently attached, for the first time, to the side chains of conjugated polymers. Two sets of such hybrid conjugated polymers have been prepared, one (Ia and Ib) with the clusters linked to the conjugated backbone through a rigid conjugated bridge, the other (IIa and IIb) through flexible alkyl chains. Within each set, polymers with different cluster loading ratios have been prepared. The covalent attachment of POM clusters has been confirmed by 1H NMR, FTIR, and cyclic voltammetry measurements. These hybrid polymers are thermally stable up to 220 °C. Set I polymers (Ia and Ib) exhibit maximum absorption wavelengths (λmax) around 410 nm, while set II polymers (IIa and IIb) show higher λmax values, around 440 nm. Fluorescence studies show that side-chain POM pendants linked through conjugated bridges exhibit a much higher fluorescence quenching effect than those with flexible alkyl bridges, indicating that the through-bond photoinduced electron transfer may be the dominant mechanism for fluorescence quenching. With efficient fluorescence quenching that results in free charge carriers residing in different structural units (positively charged holes in the PPE backbone and negatively charged electrons in the POM clusters), these hybrid polymers may have great potential for applications in photovoltaic (PV) cells.

Hybrid materials based on covalently linked inorganic polyoxometalates (POMs) and organic species containing a delocalized pi system have drawn increasing attention. These hybrids, traditionally prepared by cluster assembly approaches that lack predictability and controllability, can now be synthesized through common organic reactions by using organically functionalized POM clusters as building blocks. This minireview highlights some of the most recent advances on a particular type of hybrids where the organic and inorganic components are connected by an imido linkage.

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