Ferrocene-based chromophores

Figure 3 Structures of some ferrocene-based chromophores with high powder SHG efficiencies.

Fig. 11.6 Structures and NLO properties of two ferrocene-based dipolar chromophores [51, 52].

In addition to solution measurements, several bulk measurements have been made on ferrocene chromophores incorporated into poled polymer films." These measurements have shown that there are no special problems associated with poling ferrocene chromophores. The best bulk performance achieved for a ferrocene-based polymer material was an EO coefficient, of 25pmV (1,300 nm) for a film of 18 incorporated at 20 wt.% into amorphous polycarbonate " this is not, however, competitive with the performance of state-of-the-art all-organic poled polymer systems. In some cases, the chromophores have been covalently linked to the polymer chain. Bulk SHG measurements have also been made on self-assembled Langmuir-Blodgett films incorporating ionic ferrocene-based chro-... 

Contrary to previous results that involved related materials with a single orientation of the ferrocene-based NLO chromophores in the main chain,co-polymer 123 displays SHG activity after corona poling at 150 °C with reasonable stability for the SHG signal. This suggests that the chain packing in the solid state that cancels dipole additive effects in the former materials does not operate for the latter polymers which leads to a positive response to poling. 

Veggel and coworkers [137, 138] first reported the use of ruthenium(II) tris(2,2 -bipyridine) complexes ([Ru(bpy)3] +) and ferrocene as light-harvesting chromophores for sensitization of NIR luminescence from Nd(III) and Yb(III) ions. The Ru-Ln complexes (Ln = Nd 104, Yb 105) resulted from incorporating [Ru(bpy)3] + with m-terphenyl-based lanthanide complexes. Upon excitation of the Ru(bpy)s chromophore absorption with visible light up to 500 nm, both Ru-Nd and Ru-Yb complexes exhibited typical NIR luminescence because of effective Ru Ln energy transfer with the rates of 1.1 x 10 s for Ru-Nd complex and <1.0 X 10 s for Ru—Yb species. 

The common reporter groups cobaltocenium and ferrocene have not frequently been used in optical anion sensing, since these chromophores are generally insensitive to anion binding. However, metaUocene-based receptors... 

Jayaprakash et al. [198] reported the series of push-pull bimetallic polyene complexes [(CO)5M=C(OCH3)(-CH=CH-) (t C5H4)Fe(r C5H5)] (M = W, Cr n = 1-4) with ferrocene as donor and a carbene complex of Cr or W as acceptor. The jSi o6(HRS) values increase with increasing the conjugation of the n linker for the same n linker, the chromophore based on W exhibits higher second-order NLO responses than that based on Cr, as expected for a more efficient n backdonation from the W atom. The quadratic hyperpolarizability of these bimetallic push-pull... 

The use of strongly absorbing d-block chromophores as sensitizers for the NIR emissions from lanthanide ions has attracted increasing attention since the first report by van Veggel and coworkers on the Nd + and Yb + luminescence sensitized by Ru(bpy)j+ and ferrocene in 2000. Subsequently, many d-block chromophores, based on related transition metals, such as R +, Ru +, Re+, Os +, Pd, Zn +, Cr +, and Co +, have been extensively studied in sensitizing the NIR emissions of lanthanide ions (i.e., Nd +,... 

---