Black chromophores

The lower energy luminescence of Os(II) complexes relative to the corresponding Ru(II) complexes has led to a number of studies seeking complexes that absorb throughout the visible (black chromophores) and have emissive excited states in the near-infrared. Kol and Barigelletti reported the photophysical properties of Os(II) complexes of eilatin (eil, Scheme 1) and isoeilatin (ieil) bis-phenanthroline derivatives. The eil com-... 

Several basic chromophore stmctures have been proposed for this purpose. Anthraquinone dyes appear to be predominant since they have a wider color range, excellent photostabiHty, good solubiHty in Hquid crystal media, and very high order parameters. Typical basic stmctures of the three primary colors are illustrated in Figure 11. Some examples are given in Table 10. The appropriate combination of three primary colors gives a black display. 

Fig. 3 Transition energy for S0 — Sj (red) and S0 — CT(black) for a tryptophan during a 2 ns QM-MM trajectory of the human eye lens protein yD-crystallin showing typical fluctuations due to rapid changes in local electrostatic potentials at the atoms of the chromophore. This Trp has a low quantum yield because the CT state is near the Sj state much of the time. Heterogeneity in lifetime and wavelength are evident in both states because regions of 100 ps are seen having distinctly different average energies...

Practically all the commercially important reactive dyes based on activated double bonds employ the vinyl sulfone reactive group (2.35), usually as the sulfatoethylsul-fone derivative (2.34), which converts into (2.35) in the dyebath under the influence of alkali at pH 11 to 12.5. They are usually applied onto the fibre by exhaustion from the dyebath at around 40-60 °C or by cold padding at 30 °C. The vinylsulfone group is most commonly attached to the dye chromophore via an aromatic ring, e.g. Cl Reactive Black 5 (2.2), but in a few cases a bridging aliphatic group is employed. ... 

Fig. 2. Evolution of twist angle around the P-bond (grey) and I-bond (black) after photoexcitation of the neutral form of GFP chromophore in the gas phase (left panel) and solvated by 150 water molecules (right panel). Solid lines are population-weighted averages over die trajectory basis functions. Dashed lines represent the twist angles for the individual trajectory basis functions. The sense of rotation for the two torsions is defined such that HT motion corresponds to both angles moving towards more negative values.

Figure 23-26 (A), (B) Arrangement of bacteriochlorophyll chromophores in the cyclic LH2 array of Rhodopseudomonas acidophila. The B850 subunits are gray while the B800 subunits are black. (C) Fluorescence-excitation spectra. Top trace, for an ensemble of LH2 complexes, other traces, for several individual LH2 complexes at 1.2K. Fine structure is evident for the B800 but not for the B850 chromophores. From van Oijen et al.299 with permission.

Condensation reactions of lignin have been mentioned 22) in connection with sulfite pulping as being responsible for color formation. However, most of the likely condensation reactions occurring during a kraft cook do not lead directly to chromophore formation. One potential condensation reaction which would give a chromophore is the formation of a chalcone (XIX) from vanillin and acetoguaiacone, both of which have been isolated by Enkvist 12) from black liquor. 

In the application of oxidation dyes, aromatic amines form insoluble polyazine derivatives in the fiber (azine dyes [81]). Synthesis proceeds in several steps in a hydrochloric acid medium by oxidation (e.g., with dichromate). For the chief representative of this group, aniline black, the chromophore consists of dibenzo-pyran rings. Oxidation dyes are rapidly decreasing in importance because aniline and other aromatic amines as well as the bichromate used for oxidation are toxic. The colors produced by aniline black are characterized by a full bluish black shade and excellent fastness. Since they are easily reserved, they are still used occasionally for printing grounds. For individual processes, see [82],... 

Fig. 7 EET in the CC P4 including solvent induced modulations. Shown are the chromophore excited state populations, blue curve rn = 1, red curve m = 2, black curve m = 3, green curve rn = 4. Upper panel averaged populations (across a time slice of 10 ps), lower panel non-averaged populations in a 5 ps time window.

Fig.12. Computation by Monte Carlo methods of the first four order parameters of an ensemble of 1000 chromophores (of dipole moment 13 Debye) existing in a medium of uniform dielectric constant. At the beginning of the calculation, the chromophores are randomly ordered thus, ==O. During the first 400 Monte Carlo steps, an electric poling field (600 V/micron) is on but the chromophore number density (=10 7 molecules/cc) is so small that intermolecular electrostatic interactions are unimportant. The order parameters quickly evolve to well-known equilibrium values obtained analytically from statistical mechanics (black dots in figure also see text). During steps 400-800 the chromophore number density is increased to 5xl020 and intermolecular electrostatic interactions act to decrease order parameters consistent with the results of equilibrium statistical mechanical calculations discussed in the text. Although Monte Carlo and equilibrium statistical mechanical approaches described in the text are based on different approximations and mathematical methods, they lead to the same result (i.e., are in quantitative agreement)...

Fig. 12 Time-dependent wavenumber of the excited-state A (l) v(CO) IR band of [Re(im) (CO)3(phen)]+ in D20 black) and azurins with Re(CO)3(phen) chromophore attached to His83 red) and Hisl09 blue). Measured in D20 (pD = 7) after 400 nm, 150 fs laser pulse excitation. Exact IR band positions were determined by Lorentzian fitting. Reproduced with permission from [75]...

Fig. 15 Structures of pyridine, picolinate, and three structural isomers of dipicolinate, overlaid with an electron density map of the highest occupied molecular orbital (HOMO) for each hgand. These chromophores were explored to better understand the binding properties of DPA. Electron density maps generated using Titan higher electron density is in black, lower in white.

Figure 3.20 Crystal structure of [ Eu(tpaen) K(H20)3] with K+ and water molecules removed for clarity [Eu, black (large ball) O, grey N, black (small balls) C, white H, omitted], (Redrawn from the CIF file of N. Chatterton et al., An efficient design for the rigid assembly of four bidentate chromophores in water-stable highly luminescent lanthanide complexes, Angewandte Chemie International Edition, 44 (46), 7595-7598, 2005 [80].)...

Custom modifications have previously been developed whereby a non-fluorescent chromophore can be attached to the DNA sequence to provide a strong SE(R)RS signature which is indicative of the DNA sequence present. This has been done previously using DABCYL, phthalocyanines and black hole quenchers (BHQs) as well as specifically designed simple azo dyes which contain moieties to aid in their binding ability to metal surfaces such as the benzotriazole motif which has been shown to be very effective at complexing onto silver nanoparticles [12, 13, 40, 41]. 

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