Fluorescence carbazolyl

Amplified photochemical quenching of carbazolyl fluorescence was observed in mixed LB films containing pure CUA and long-chain fatty adds [49,51], A pure CUA was synthesized from 2-nitrobiphenyl and 11-bromoundecanoic add methyl ester as reported previously [49,50]. Two monolayers of mixtures of CUA (fc= 0.02 - 0.50) and PA were deposited on five monolayers of cadmium arachidate at 15°C and 20 mN m 1 at pH 6.3. 

Local motions of a, a)-bis( 1-pyrene) alkanes and pyrene -labelled poly(methyl methacrylate) in solution have been measured by pico-second excimer fluorescence spectroscopy In this study the formation of the polymers during polymerisation could be accurately maintained by measuring excimer fluorescence lifetime. The photophysical properties of poly (N-vinylcarbazole) have been interpreted on the basis of a study in diastereoisomers of 2,4-di(N-carbazolyl)t In this work it is concluded that 95% of the excitation energy occurs with chromophores associated with specific excimer sites. Excimer formation in various polyvinyl carbazole... 

Depth-distribution of fluorescent dopants in cast polymer film (4) Fluorescence spectra of poly(N-vinylcarbazole) (PVCz) film doped with perylene are shown in Fig. 6. They consist of two broad structureless excimer bands of the polymer with a shoulder at 375 nm and a peak at 420 nra, and perylene band with a vibrational structure above 450 nm. It is worth noting that the perylene fluorescence intensity under the TIR condition is relatively weaker than that under the normal one. Since the boundary surface is selectively excited under the former condition, the structure near the surface should be different from the bulk. It is well known that the excitation energy migrates over carbazolyl chromophores and is trapped in the doped perylene efficiently. Therefore, the present result means that energy migration efficiency in the host polymer and/or the dopant concentration are a function of the depth from the interface. 

J. Sanetra, D. Bogdal, M. Warzala, and A. Boron. Photo- and electroluminescent properties of polymethacrylates with carbazolyl and fluorescent pendant groups. Chem. Mater, 14(l) 89-95, January 2002. 

Ch. Monte, A. Roggon, A. Subaric-Leitis, W. Rettig, and P. Zimmermann, Resonance Effects of Diabatic Surface Crossing within the Torsional Spectrum of 9-(N-Carbazolyl) Anthracene Observed by Supersonic Jet Fluorescence Spectroscopy , J. Chem. Phys. 98, 2580 (1993). 

At low temperatures nearly no excimer fluorescence is observed, indicating that the TG conformation is the more stable. In analogy with the excimer emission observed in 1,3-di(N-carbazolyl)propane, the 420 nm excimer band in meso A6 is assigned to the full overlap excimer (TT). 

Measurements of the circularly polarized fluorescence (CPF) of this compound (PPA) as a function of temperature indicate the existence of two kinds of excimers one with a negative CPF dissymmetry with an emission maximum around 460 nm and predominant at higher temperatures, the other with a positive CPF dissymmetry emitting at wavelengths longer than 500 nm and mainly formed at lower temperatures (Egusa et al., 1985). In the emission spectrum of poly-N -(9-carbazolyl)-carbonyl-L-lysine, even four distinct species are observed besides the emission of locally excited carbazole. 

In order to determine the influence of the physical properties and the size of the fluorescent molecule on the observed mobility, we look at the emission behaviour of another probe dispersed in some of the polymers used in the diphant probe studies.lt would be of interest to investigate the intramolecular excimer formation in bis(9-anthryl) oxide, less bulky than diphant. Unfortunately this compound is not photostable and gives rise to photocyclomers. The present work has, therefore, been performed with the 2,4-di(N-carbazolyl) pentane (meso-DNCzPe)(see formula) in which the aromatic group are of similar size to the bis-anthryl derivative. 

Fig. 9. Fluorescence emission spectra of diastereomeric 2,4-di(9-carbazolyl)pentane (21) ...

Poly(2-(iV-carbazolyl)ethyl methacrylate (10a) has been synthesized from the corresponding methacrylate monomer by free-radical polymerization with AIBN as initiator [164]. The polymer has no excimer-forming sites and even its films show a clear monomer fluorescence [165]. A high efficiency of energy migration is characteristic of this polymer. Despite its lower chromophore concentration, the polymer exhibits a charge carrier mobility comparable to that of PVK. 

These polymers are prepared by polycondensation reactions. Polyurethanes containing DCZB moieties in the main chain (26a) were prepared by treating trans-l,2-bis(3-hydroxymethyl-9-carbazolyl)cyclobutane with the corresponding diisocyanate in the presence of dibutyltin dilaurate [204]. The relative molecular mass of the polymer synthesized using hexamethylene diisocyanate as a linking agent was 2700, and that of the polymer prepared with toluylene diisocyanate was 16000. Polymers (26a) exhibit almost exclusively monomer fluorescence in dilute solution, i.e. they practically have no intramolecular excimer-forming sites. Their complexes with TNF show better photoconductivity than PVK-TNF. 

---