Pyridyl blues

Color formers such as 16 and 17 and their mixtures are commonly known as Pyridyl Blues and are excellent products in combination with organic developers, yielding intense blue images with very high fastness properties. However, it has been observed71 that, for some applications, the 7-azaisomer is too reactive and hence it was desirable to modify the... 

Not only the absorption behaviour, but also all the physical properties of derivatives (32) are related to the nature of the 2,5-substitution pattern. For example, a blue-green emission is observed for di(2-pyridyl)phosphole (32b) whereas the emission of di(2-thienyl)phosphole (32a) is red-shifted (AAj,nj= 35 nm) [36]. Likewise, cyclic voltammetry (CV) revealed that derivative (32a), featuring electron-rich thienyl substituents, is more easily oxidised than compound (32b), which possesses electron-deficient pyridyl substituents [36]. 

Blue luminescence of zinc complexes of pyridyl-containing complexes is an area of current interest.277 Design of blue luminescent materials is of relevance to display applications, as blue-light-emitting diodes, and to this end Che examined solution luminescence of zinc pyridylamine complexes.73,278 Che and co-workers studied the complex Zn40(7-azaindoyl)6 which has a blue emission at 433 nm in the solid state.279,280 In an attempt to improve on stability Wang et al. examined compounds with neutral 7-azaindole and an A-functionalized pyridyl derivative.281 In contrast with other metal complexes of the neutral 7-azaindole (32), Zn(7-azaindole)2(OAc)2 is a blue luminescent compound and a A-(2-pyridyl) 2-azaindole (33) and its complexes were also... 

Poly(2,5-pyridyl) commonly know as poly(pyridine) has been the subject of considerable research effort as it luminesces in the blue region of the spectrum and may have uses in light emitting diodes (LEDs). Vaschetto and co-workers [103] reported a series of calculations on the molecule and its oligomers. The calculations included both the B3LYP and B3P88 density functions, Hartree-Fock calculations and a periodic solid-state DFT calculation using linear muffin tintype orbitals (LMTO). 

Pyrrolo[2,3-. ]pyridine zinc(ll) and A -(2-pyridyl)pyrrolo[2,3- ]pyridine zinc(ll) compounds have been prepared and characterized by X-ray crystallography <2000IC5248>. The pyrrolo[2,3- ]pyridine zinc compound, formed from pyrrolo[2,3-. ]pyridine and zinc acetate, is a stable compound that can produce a blue light in electroluminescent devices. 

Analysis of antioxidant activity by performing a FRAP assay was proposed by Benzie and Strain [23]. It involves colorimetric determination of the reaction mixture in which the oxidants contained in the sample reduce Fe ions to Fe. At low pH, Fe(in)-TPTZ (ferric-tripyridltria-zine) complex is reduced to the ferrous (Fe ) form and intense blue colour at 593 nm can be observed. The FRAP reagent is prepared by mixing 2.5 ml of TPTZ (2,4,6-tris (l-pyridyl)-5-triazine) solution (10 mM in 40mM HCl), 25 ml acetate buffer, pH 3.6, and 2.5 ml FeCl3 H20 (20 mM). The colour of Fe(II)(TPTZ)2 which appears in the solution is measured colorimetri-cally after incubation at 37°C. The measurement results are compared to those of a blank sample, which contains deionised water instead of the analysed sample. The duration of the assay differs from one study to another 4 min [23, 24], 10 min [25] to 15 min [26]. The analysis results are converted and expressed with reference to a standard substance, which can be ascorbic acid [26], FeS04 [23, 25], Trolox [27,18]. 

Two interesting Pt(II) polyynes that possess mixed heterocyclic groups consisting of both thienyl and pyridyl rings 42 and 43 were also reported.43 The Eg values for 42 and 43 are 2.67 and 2.55 eV, respectively, which can be compared to the gaps of 2.55 and 2.40 eV for 29 and 30, and the corresponding blue shifts of 0.12 and 0.15 eV are consistent with a reduction in the D-A interaction between the metal and ligand. 

Phospholes 3a,b are also fluorophores and their Aem values depend on the nature of the 2,5-substituents. A blue emission is observed for l-phenyl-2,5-di(2-pyridyl)phosphole 3b = 463 nm) whereas the emission of 1-phenyl-2,5-di(2-... 

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