Luminophore synthesis

Bernhard and coworkers [58] have addressed the discovery of ionic iridium(III) and ruthenium(II) complexes by combinatorial luminophore synthesis and screening (Scheme 5.9). Starting from iridium trichloride, cyclometalation with (hetero)arylpyridyl ligands 45 (Fig. 5.17) gives rise to the formation of binuclear iridium complexes 46. Upon complexation with bidentate N,N- or P,P-ligands 47 (Fig. 5.17), the cationic complex 48 is formed, which upon anion metathesis with hexafluorophosphate is transformed into the target complex 49. In this sequence, the step from 46 to 48 was performed in a traditional and a parallel manner, the latter leading to a library of 100 iridium and 10 ruthenium complexes. 

On the other hand, pyrazoline and pyrazole derivatives are successfully used for material science tasks. For example, triarylpyrazolines are used in the synthesis of green electroluminescent polymers for light-emitting diodes [18], Some aromatic substituted 2-pyrazolines are effective organic luminophores [19,20], fluorophores [21] and scintillating materials [20, 22]. 

The term upconversion describes an effect [1] related to the emission of anti-Stokes fluorescence in the visible spectral range following excitation of certain (doped) luminophores in the near infrared (NIR). It mainly occurs with rare-earth doped solids, but also with doped transition-metal systems and combinations of both [2, 3], and relies on the sequential absorption of two or more NIR photons by the dopants. Following its discovery [1] it has been extensively studied for bulk materials both theoretically and in context with uses in solid-state lasers, infrared quantum counters, lighting or displays, and physical sensors, for example [4, 5]. Substantial efforts also have been made to prepare nanoscale materials that show more efficient upconversion emission. Meanwhile, numerous protocols are available for making nanoparticles, nanorods, nanoplates, and nanotubes. These include thermal decomposition, co-precipitation, solvothermal synthesis, combustion, and sol-gel processes [6], synthesis in liquid-solid-solutions [7, 8], and ionothermal synthesis [9]. Nanocrystal materials include oxides of zirconium and titanium, the fluorides, oxides, phosphates, oxysulfates, and oxyfluoiides of the trivalent lanthanides (Ln ), and similar compounds that may additionally contain alkaline earth ions. Wang and Liu [6] have recently reviewed the theory of upconversion and the common materials and methods used. 

The recent applications of Weidenhagen reaction conditions have allowed the synthesis of 4(5)-(2 -hetaryl)imidaz-oles 38 that can be transformed into potential luminophores [67], The polycyclic compounds 38 were obtained from the corresponding 2-furomethyl and 2-thenoylmethyl acetates (34 and 35, respectively) by condensation with formaldehyde 36 [67a] and benzaldehyde 37 [67b] in the presence of ammonia and copper acetate (Scheme 12.10). 

Farah AA, Pietro WJ (1999) Synthesis and characterization of partially crosslinked poly (N-vinylcarbazole-vinyl alcohol) copolymers with polypyridyl Ru(II) luminophores. Potential materials for electroluminescence. Polym Bull 43 135-142... 

Bottini, M. Magrini, A. Di Venere, A. Bellucci, S. Dawson, M. L Rosato, N. Bergamaschi, A. Mustelin, T. Synthesis and characterization of supramolecular nanostructures of carbon nanotubes and ruthenium-complex luminophores. J. Nanosci. Nanotechnol. 2006, 6,1381-1386. 

Introduction of luminophores in NPs is often performed during NP synthesis as sketched in Scheme 4.6. In this example, the [Eu(PTTA)] complex is covalently linked to APTS first, introduced into the water in oil emulsion and after adequate treatment, NPs with about 40-nm size are obtained. Further surface treatment includes derivatisation by SA with a procedure similar to the one adopted by the authors for molecular probes and mentioned above (Section 4.3.1). Such NPs, co-doped with the Eu and Tb complexes to achieve multimodal capability, are uptaken by mouse LAFl pituitary gland tumour cells and serve as stains to... 

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