Chromophoric ligand

Metal Introduced Into the Dyestuff Molecule in Manufacture. These dyes fall into two categories according to the ratio of metal cation to dye molecule anion 1 1 metal dye complexes comprise one metal cation and one chromophoric ligand and 1 2 metal dye complexes comprise one metal cation and two chromophoric ligands. 

Binding Experiments. Some of these chromophoric glycosides proved also to be valuable in cases where no hydrolysis by the cellulases occurred. This was shown in the case where the 4-methylumbelliferyl glucoside and cellobioside were not hydrolyzed by the CBH II from Trichoderma (see above) but could be used as reporter ligands in a series of binding experiments. Typically the fluorescence of the cellobioside was quenched in the presence of CBH II and was restored by the addition of excess amounts of non-chromophoric ligands, i.e., cellobiose (Fig. 3). Thus association constants... 

The binding of chromophoric 1-thioglycosides from lactose or cellobiose to CBH I (Tr. r.) was followed by difference spectrophotometry of the ligand, or by the diafiltration technique (Fig. 4). Alternatively, perturbation of the protein spectrum could be used in the case of non-chromophoric ligands (Fig. 5). 

Absorption by the chromophore ligand is commonly (6) followed by inter-system crossing (ISC) to the triplet state of the ligand. This state can decay either by emission (ligand phosphorescence) or by... 

Fig. 35. Ancillary chromophoric ligands for the formation of ternary complexes.

Following the initial reports of the anteima effect in lanthanide cryptates, many other lanthanide complexes containing additional chromophoric ligands have been investigated and found to be useful as luminescent labels for biological substrates, and in general as sensors based on luminescent properties [21]. 

Non-chromophoric ligand variations have been carried out in the series of osmium complexes [Os(phen)L ](L-pyridine, MeCN, phosphine, arsine) and emission energies, excited-state redox potentials, and radiative and non-radiative rate const2uits found to vary systematically with the potential of the ground-state Os(III/II) couple.Phosphorescence from [Os(TTP)(CO)MeOH] au d [Os(TTP)(CO)pytIdlne] is quenched by electron donors auid acceptors by a reversible electron transfer mechauiism. 

Whereas the binding of CBMs to insoluble carbohydrates can be monitored by the UV absorption of the protein, relatively large amounts are required, and in some of the early studies on CBDs they were made radioactive with to increase sensitivity. The general technical problem of monitoring the binding of soluble, non-chromophoric ligands to soluble CBMs, has, however, been solved only in the last decade, with the advent of isothermal titration microcalorimetry... 

Much work has been done to establish the factors that are important in creating complexes with highly efficient, long-lived luminescence. As with all ligand systems, this includes the efficiency of population of the ligand triplet state and energy transfer to the lanthanide center, i.e., an appropriate choice of chromophore. Ligand mono-... 

Tetrathiahelicene nitrile derivatives can act as chromophore ligands in the formation of organometallic complexes. Complexes of general formula [MCp(P-P)(NC TH-[7]-Y Z)][PF6] (M = Ru, Fe, Y = H, NO2, Z = FI, CN) (81—86) (Figure 7(a)) are easily synthesized and fijlly characterized. Spectroscopic characterization of these complexes shows good conjugation between the metal center and the acceptor group on the helical chromophore. 

Electronic structure and spatial orientation of LUMO of cis and trans isomers of Cr(lI0-N2O4 chromophore. (Ligand field parameters from AOM analysis of Hoggard and Schmidtke, BBPC 76, 1013 (1972)). 

In the case of lanthanide coordination complexes, two kinds of chromophoric ligands are generally designed as follows ... 

The spectator however influences the energy gap by stabilization of the (dTC ) core by electronic donation. As LL becomes a better donor, the MLCT transition energy is decreased, as illustrated in figure 1. Using the above principle, extensive tuning in the energy of the Ru-dcbpy CT excited state has been obtained in complexes of the type [Ru(dcbpy)2X2] and [Ru(dcbpy)2(Y-bpy)] where X is a non-chromophoric ligand (e.g Cl, CN,..) and Y-bpy is a 4,4 -disubstituted-2,2 -bipyridine [22]. 

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