Fluorene derivatives

One of the first examples was the above mentioned work from Yoshino et al. [7] concerning the synthesis of poly(9,9-dialkylfluorene)s via oxidative coupling of fluorene derivatives. Poly(9,9-dialkylfluorene) derivatives have been also synthesized via Ni- and Pd-catalyzed aryl-aryl homo- and cross-coupling reactions of sui-... 

In the Spiro systems 30, the aromatic orbitals unsymmetrize the carbonyl orbital. Simultaneously, the carbonyl group can perturb the orthogonal aromatic ring. Nitration of the fluorene derivatives (30) bearing a spiro substituent was studied (Fig. 17) [96, 97]. 

One of the first examples was that reported by Yoshino et al. [12] concerning the synthesis of polyfluorenes via oxidative coupling of fluorene derivatives as decribed above. 

M. Ranger, D. Rondeau, and M. Leclerc, New well-defined poly(2,7-fluorene) derivatives photoluminescence and base doping, Macromolecules, 30 7686-7691, 1997. 

J.-I. Lee, G. Klaemer, and R.D. Miller, Oxidative stability and its effect on the photoluminescence of poly(fluorene) derivatives end group effects, Chem. Mater., 11 1083-1088, 1999. 

A. Charas, J. Morgado, J.M.G. Martinho, L. Alcacer, and F. Cacialli, Electrochemical and luminescent properties of poly(fluorene) derivatives for optoelectronic applications, Chem. Commune. 1216-1217, 2001. 

McCoy, E. C., E. J. Rosenkranz, H. S. Rosenkranz, and R. Mermel-stein, Nitrated Fluorene Derivatives Are Potent Frameshift Mutagens, Mutat. Res., 90, 11-20(1981). 

Exciton coupling between the two styryl chromophores in each of the conformers (A)-(C) leads to a negative Cotton effect at around 270 nm, as shown by theoretical analysis using the 71-electron SCF Cl dipole velocity MO method. Therefore, the tram-2,.1-disubstituted spirocyclo-propane-1,9 -fluorene derivative 6, from which the distyryl derivative was obtained, must have accordingly the 2S3S absolute configuration122. 

The materials studied for 2PA properties involve a number of types of conjugated structures with donor and acceptor groups from stryl to cyanine dyes. Our group is particularly interested in conjugated fluorene derivatives. Fluorene derivatives have been used in conducting polymers, more recently in... 

Fig. 2 The structures of fluorene derivatives designed and synthesized for studying molecular structure-2PA property relationships...

The time-resolved emission spectra (TRES) and fluorescence lifetimes, ti, of the fluorene derivatives were measured in liquid solutions at room temperature with a PTI QuantaMaster spectrofluorimeter with 0.1 ns temporal resolution [20]. At this resolution, all investigated fluorenes exhibited TRES which were coincident with the corresponding steady-state fluorescence spectra. As an example, TRES for compounds 3 and 11 in hexane, THE, and ACN are presented in Eig. 8 for different nanosecond delays 0 ns (curves 2,4,6) and 5 ns, which modeled the steady-state condition (curves 3,5,7). No differences in the fluorescence spectra for these two delays were observed, indicating that all relaxation processes in the first excited state Si are sufficiently fast for fluorene molecifles and did not exceed the time resolution of the PTI system ( 0.1 ns). 

Excited-State Absorption and Anisotropy Properties of Fluorene Derivatives... 

Comprehensive experimental investigations of 2PA processes in fluorene derivatives were performed by Hales et al. [53,56-59] with open aperture Z-scan [26], two-photon induced fluorescence [60] and femtosecond white-light continuum pump-probe methods [61]. For degenerate two-photon excitation, the experimental 2PA spectra of symmetrical and asymmetrical fiuorenes are presented in Figs. 15 and 16. These spectra were obtained with the combination of open aperture Z-scan and two-photon fluorescence methods [57]. For centrosymmetric molecules, two-photon transitions from... 

---