Complexes fluorescence properties

Studies of fluorescence properties of the dye pair (i.e., boron difluoride complexes dye 9a-d and the nonsubstituted one lOa-d) in the BSA/SDS mixture revealed that coumarins 9b and 10c showed two excitation and emission bands, while other heterocycles showed single bands in the corresponding spectra. For all studied compounds, excitation and emission maxima occurred in the range 405-603 nm and 467-680 nm, respectively. 

Some useful general rules which seem to account for the fluorescent properties of metal coordination complexes of 8-hydroxyquinoline have been proposed 191,192 These are ... 

Figure 5. Fluorescence properties of covalent complexes derived from the covalent binding of (+)-anti-BaPDE to DNA.

Emission-Excitation Matrix (EEM) fluorescence spectroscopy as a nondestructive and sensitive analytical technique was successfully applied in this study to characterize DOM in landfill leachte. The DOM is composed of complex mixture of organic compounds with different fluorescence properties. In particular, the EEM profiles of DOM show two well-defined peaks at Ex/Em=320-350 /400-420 nm, Ex/Em=320-350 /420-450 nm reasonably due to the presence of two different groups of fluorophores. An additional and less intense band at Ex/Em=280-290 /320-350 nm can be assigned to aromatic amino acids and phenol-like compounds. 

Soroka K, Vithanage RS, Phillips DA et al (1987) Fluorescence properties of metal complexes of 8-hydroxyquinoline-5-sulfonic acid and chromatographic applications. Anal Chem 59 629-636... 

The fluorescence properties of aromatic carbonyl compounds are complex and often difficult to predict. 

O. S. Wolfbeis and H. Offenbacher, The effects of alkali cation complexation on the fluorescence properties of crown-ethers, Monat. Chem. 775,647-654(1984). 

It turned out that aflatoxin was actually a mixture of four different but closely related chemicals. All possessed the same molecular backbone of carbon, hydrogen, and oxygen atoms (which backbone was quite complex and not known to be present in any other natural or synthetic chemicals), but differed from one another in some minor details. Two of the aflatoxins emitted a blue fluorescence when they were irradiated with ultraviolet light, and so were named aflatoxin Bi and B2 the names aflatoxin Gi and G2 were assigned to the green-fluorescing compounds. The intense fluorescent properties of the aflatoxins would later prove an invaluable aid to chemists interested in measuring the amount of these substances present in various foods, because the intensity of the fluorescence was related to the amount of chemical present. 

Table I. Fluorescence Properties of Some Metal Complexes of TPP in Acetonitrile at 296 K...

Relatively recently, AIS Sommer GmbH of Germany delivered a laser-induced fluorescence (LIP) analyzer for quality control in minerals and mineral processing (Broicher 2000). The LIP analyzer includes two light detector systems with three photomultipliers each, which evaluate three spectral bands in two time windows each. It was done in the Kiruna phosphorous iron ore mine, Sweden. The limitation of LIP analysis is that its accuracy depends on the complexity of the composition of the ore and the concentration and fluorescence properties of the critical minerals in relation to all the other minerals present. The phosphorous iron ore in Kiruna is ideal for LIP analyzes, because its iron minerals are practically non-luminescent, while magmatic apatite is strongly fluorescent with intensive emissions of Ce and Eu ". ... 

A series of 3-alkyl- and 3-aryl-7/7-furo[3,2- ]-l-benzopyran-7-ones 78 (linear furocoumarins) was synthesized and evaluated for their photochemical and nonphotochemical crosslink formation with DNA as well as for their spectro-photometric and fluorescent properties, lipophilicity, and ability to photobleach A, A -dimethyl-/)-nitrosoaniline (RNO) after irradiation with UVA light <2002AP187>. The synthesis of the linear furocoumarins (Scheme 10) was a modification of a previously published method in which 7-hydroxy-2//-l-benzopyran-2-ones 76 were converted into / -ketoethers 77 by alkylation with haloketones under phase-transfer catalysis conditions. Base-catalyzed intramolecular condensation and subsequent acidification gave the corresponding 78. A molecular complex between each one of these fluorescent furocoumarins and DNA was observed, but only compounds with a 3-Me or 3-Ph group showed UVA irradiation-induced crosslink formation. 

The fluorescence properties of EuD3 and its complexes with Lewis bases was examined in detail by Ohlmann and Charles 147). They found that stable complexes may be formed between it and a variety of Lewis bases. In Table VIII are listed the compositions, fluorescent lifetimes, and relative... 

The same group extended their work recently to the synthesis of a peptide-based device detecting Zn2+ in aqueous solutions. [441 The principle is to add a dansyl fluorophore on a Lys side chain of a synthetic Zn finger peptide. Upon complexation of Zn2+, an important conformational change occurs that brings the fluorophore into a different environment and leads to a change in the fluorescence properties. 

Salicyladehyde complexes. — In addition to the salicylate complexes Weissman 630 also prepared a salicyladehyde (CaH OHJCHO) complex of Eu3+ and studied the fluorescence properties of this complex. Weissman s preparation was represented as a fm-salicyladehyde complex but no chemical analysis was given in support of this composition. Recently Charles [415] has prepared the salicylaldehyde complexes of La, Ce, Pr, Nd, Sm and Eu in excellent yields by the interaction of Na-... 

Another technique that uses the fluorescence properties of trivalent lanthanides is that of the detection of fluorescence emission decay induced by pulsed dye laser excitation. Horrocks and Sudnick (17) have applied this technique to the study of water molecules bound to metal ions in small complexes and proteins. In one study they found that the exponential decay of Tb3+ fluorescence is altered when H20 is replaced by D20 and that this change can be used to determine the number of coordinated water molecules on the metal ion. With thermolysin, bound Tb3+ had 1-2 water molecules in the first coordination shell. This number is consistent with the x-ray structure. 

Titration with chelators of a metalloenzyme preparation from which extraneous metals and chelators have been removed produces a characteristic enhancement of the intrinsic protein fluorescence (excitation at 280 nm, emission at 350 nm) (13). This fluorescence enhancement by nonfluorescent chelators is instantaneous, reversible by excess added divalent metal ions, and can occur without loss of activity. Different chelators give different characteristic amounts of fluorescence enhancement at saturation, demonstrating the specific effect of the chelator on the fluorescence of the apparent metalloenzyme-chelator complex. In contrast, if the effect of chelators were simply to complex with Mg2 after its dissociation from the metalloenzyme, the resulting apoenzyme should have identical fluorescence properties regardless of which chelator was utilized. 

The fluorescence properties of two fulvic acids, one derived from the soil and the other from river water, were studied. The maximum emission intensity occurred at 445-450 nm upon excitation at 350 nm, and the intensity varied with pH, reaching a maximum at pH 5.0 and decreasing rapidly as the pH dropped below 4. Neither oxygen nor electrolyte concentration affected the fluorescence of the fulvic acid derived from the soil. Complexes of fulvic acid with copper, lead, cobalt, nickel and manganese were examined and it was found that bound copper II ions quench fulvic acid fluorescence. Ion-selective electrode potentiometry was used to demonstrate the close relationship between fluorescence quenching and fulvic acid complexation of cupric ions. It is suggested that fluorescence and ion-selective electrode analysis may not be measuring the same complexation phenomenon in the cases of nickel and cobalt complexes with fulvic acid. 

---