Oligomers conjugated

01igo(phenylene ethynylene)s (OPEs) are a family of molecules that have been suggested to function as molecular intercormects. They have been widely used for the construction of molecular electronic devices [21, 23] and experiments on their charge transport properties have already been conducted in this laboratory [18]. They are known 

To our knowledge, the only investigation into metal/SAM interactions for OPEs was carried out by Haynie et al. [6]. They studied the interactions between PPB-SH assembled on Au(l 11) and a series of vapor-deposited metals Au, Ti, Fe, Cr, Cu, Ag and Al, via TOF-SIMS. No evidence of any chemical interactions or penetration was found in the case of Au, Fe, Cr, Ag and Al. Tliis was attributed to the high packing density of these monolayers and the consequent steric hindrance toward penetration. In the case of Ti, the vapor-deposition destroyed the molecular array this is important, since, in many molecular electronics experiments, Ti is often us as a bonding metal for the formation of molecule-metal connections [2, 23]. In the case of Cu, they found several peaks in the mass spectrum, indicating a potential reaction between the metal and the benzene rings. 

In this laboratory, the study of the interactions between copper and HS-PPB-SH has recently been undert en, and the preliminary results obtained so far will be illustrated in brief. Ihe results will be reported in full, together with the experimental details, in a manuscript currently in preparation [35]. The same series of experiments carried out for alkanethiol SAMs have been attempted in the case of HS-PPB-SH. However, due to the aforementioned differences between alkanethiols and conjugated oligomers, the results obtained already depart from those obtained for C SH and C SH. The monolayer of HS-PPB-SH has b n characterized, via PAIRS, as deposited and after deposition of copper 

Although these are preliminary results that need further experimental work, they are a good indication that a very different behavior should be expected when metal evaporation is carried out on a conjugated oligomer as opposed to alkanethiol SAMs. The formation of a macroscopic metallic lead on the organic surface might lead to the solvation of part of the metal within the layer and/or the introduction of conformational disorder in the layer. 

The authors thank the Petroleum Research Fund (ACS-PRF No. 36477-AC5) for support of this research. This material is based upon work supported under a National Science Foundation Graduate Research Fellowship. The authors thank also Dr. Timir Datta for the use of his evaporation chamber and Art Illingworth and Allen Frye for the fabrication of an evaporation chamber for this laboratory. 

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This article, while not being intended to provide a full account of poly(arylene)s, emphasises the synthetic aspects. The synthesis of conjugated oligomers and polymers is, however, always part of an interdisciplinaiy approach with their active physical function being a key concern. In that sense the research being reviewed above concentrates on physical properties rather than playing with exotic chemical structures. 

In order to summarize this section it must be noted that the possibility to evaporate conjugated oligomers in such a way that their chain axes point predominantly in one direction allows us to determine the anisotropic electronic properties of conjugated molecules. From these studies it becomes evident that in order to obtain polarized absorption or emission of light as required in polarization Filters or LCD-backlights, the application of conjugated molecules is one of the most attractive areas of application for these materials. 

Finally, we would like to point that one of the easiest ways to influence the electronic properties of conjugated oligomers and polymers is to vary the chain... 

Overall, an unambiguous description of the current flow to a certain injection and transport model can not be obtained, as demonstrated by the example of LEDs based on Alq3. Similar to the organic molecule Alq3 and also the conjugated oligomer hexaphcnyl, it has been observed that many models presented above seem to describe the 1/V characteristics correctly [I02. ... 

Another way of obtaining information on the time-averaged mobility of charge carriers on their way across a sample of arbitrary thickness is, to simultaneously measure the current and the stationary charge earners density via transient absorption and to infer the mobility from j-rnpF. Such experiments have been performed on blends of conjugated oligomers derived from /m-siilbene amine and a... 

Chapter 5, written by M. Hissler, P. W. Dyer, and R. Reau, concerns an area of important expansion, i.e., the synthesis and properties of rr-conjugated oligomers and polymers containing phosphorus moieties. The possibility of using... 

Spano, F. C. 2006. Excitons in conjugated oligomer aggregates, films and crystals. Annu. Rev. Phys. Chem. 57 217-243. 

R. E. Martin, F. Diederich, Linear Monodisperse ji-Conjugated Oligomers Model Compounds for Polymers and More , Angew. Chem. Int. Ed. Engl. 1999, 38, 1350-1377. 

Figure 4. (Phenylene ethynylene)-based conjugated oligomers prepared in solution using a bi-direction growth approach with in situ deprotection and coupling.

R. Wu, J. S. Schumm D. L Pearson, J. M. Tour, Convergent Synthetic Routes to Orthogonally Fused Conjugated Oligomers Directed Toward Molecular Scale Electronic Device Applications, I. Org. Chem. 1996, 61, 6906-6921. 

J.-F. Morin, N. Drolet, Y. Tao, and M. Leclerc, Syntheses and characterization of electroactive and photoactive 2,7-carbazolenevinylene-based conjugated oligomers and polymers, Chem. Mater., 16 4619-4626, 2004. 

YV Romanovskii, A Gerhard, B Schweitzer, U Scherf, RI Personov, and H Bassler, Phosphorescence of TT-conjugated oligomers and polymers, Phys. Rev. Lett., 84 1027-1030, 2000. 

Y Geng, ACA Chen, JJ Ou, SH Chen, K Klubek, KM Vaeth, and CW Tang, Monodisperse glassy-nematic conjugated oligomers with chemically tunable polarized light emission, Chem. Mater., 15 4352-4360, 2003. 

Bredas J-L, Comil J, Beljonne D, Santos DAD, Shuai Z (1999) Excited-state electronic structure of conjugated oligomers and polymers a quantum-chemical approach to optical phenomena. Acc Chem Res 32 267-276... 

Bredas J-L, Beljonne D, Coropceanu V, Comil J (2004) Charge-transfer and energy-transfer processes in 7i-conjugated oligomers and polymers a molecular picture. Chem Rev 104 4971-5003... 

Liu B, Gaylord BS, Wang S, Bazan GC (2003) Effect of chromophore-charge distance on the energy transfer properties of water-soluble conjugated oligomers. J Am Chem Soc 125 6705-6714... 

Schumm JS, Pearson DL, Tour JM (1994) Angew Chem 33 1360-1363 Iterative divergent/convergent approach to linear conjugated oligomers by successive doubling of the molecular length... 

Martin RE, Diederich F Angew Chem Int Ed (1999) 38 1350-1377 Linear monodisperse n-conjugated oligomers model compounds for polymers and more... 

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