Fluorene, dipole moment

The electronic structure of fluorenes and the development of their linear and nonlinear optical structure-property relationships have been the subject of intense investigation [20-22,25,30,31]. Important parameters that determine optical properties of the molecules are the magnitude and alignment of the electronic transition dipole moments [30,31]. These parameters can be obtained from ESA and absorption anisotropy spectra [32,33] using the same pump-probe laser techniques described above (see Fig. 9). A comprehensive theoretical analysis of a two beam (piunp and probe) laser experiment was performed [34], where a general case of induced saturated absorption anisotropy was considered. From this work, measurement of the absorption anisotropy of molecules in an isotropic ensemble facilitates the determination of the angle between the So Si (pump) and Si S (probe) transitions. The excited state absorption anisotropy, rabs> is expressed as [13] ... 

Syrkin and Shott-Lvova attribute the high dipole moments of fluorene and triphenylmethane in dioxane (compared to benzene) to H bonding of the G—bond to the dioxane oxygen (1985). 

Liquid crystalline fluorene oligomers can emit polarized fight with proper alignment of their molecular axes and, hence, of their transition dipole moments. For example, linearly polarized emission results from uniaxial alignment of fluorene oligomers. One common way to characterize linearly polarized emission is to measure its emission dichroism, viz. the emission... 

Ferroelectric liquid crystals having a heterocyclic pyrimidine, pyrazine, or pyridazine ring have been developed. Phenylpyrimidine systems show a characteristic low rotational viscosity, and fused aromatics, such as fluorene, fluorenone, or naphthalene, have been discussed from the viewpoint of dipole moment, spontaneous polarization, and orientability. 

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