Spectral and Photophysical Properties of Aromatic Thiones in Micellar Systems: Xanthione as Convenient Absorption and Emission Probes

Maciejewski, Andrzej; Jakubowska, Anna; Dutkiewicz, Edward; Augustyniak, Włodzimierz

doi:10.1006/jcis.1996.0067

Cited by 10 publications

(2 citation statements)

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“…Previous studies have alleviated the problem of self-quenching to some extent with the use of micelles in water and with cyclodextrin, calixarene, and cellulose as hosts in the solid state. [28][29][30][31][32][33][34][35] We demonstrate in this report that a cavitand known by the trivial name octa acid (OA), which has not been explored previously in the context of room temperature phosphorescence, performs a far better job than any of the organic hosts explored thus far. We also compare the performance of OA as a container to enhance phosphorescence from thioketones at room temperature with the more common water-soluble organic hosts cucurbiturils and cyclodextrins.…”

Section: Introductionmentioning

confidence: 99%

Closed Nanocontainer Enables Thioketones to Phosphoresce at Room Temperature in Aqueous Solution

et al. 2010

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Thiocarbonyl compounds possess unusual photophysical properties: they fluoresce from S 2 , phosphoresce from T 1 only at extremely low concentrations in solution at room temperature, have unit quantum yield of intersystem crossing from S 1 to T 1 , undergo self-quenching at diffusion-controlled rates, and are quenched by ground-state oxygen leading to self-destruction. In this article, we are concerned with finding a new method to observe phosphorescence from thioketones at room temperature in aqueous solution at high concentrations. To achieve this goal, one needs to find ways to eliminate diffusion-limited self-quenching and oxygen quenching. We present here a general strategy that has allowed us to record phopshorescence from a number of thioketones in aqueous solution at room temperature. The method involves encapsulation of thioketone molecules within a "closed nanocontainer" made up of two cavitand molecules known by its trivial name as octa acid. In these supramolecular complexes, despite two thiocarbonyl compounds being present in close proximity, no self-quenching occurs within the confined space due to curtailment of their rotational freedom. Although phosphorescence could also be observed when these thioketones are included in open containers, such as cucurbiturils and cyclodextrines, the closed container made up of octa acid is found to be the best medium to observe phosphorescence from thioketones whose excited state chemistry is essentially controlled by self-quenching.

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Section: Introductionmentioning

confidence: 99%

Closed Nanocontainer Enables Thioketones to Phosphoresce at Room Temperature in Aqueous Solution

et al. 2010

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“…The formation of inclusion complexes between various guest molecules and cyclodextrins (CDs) is the most remarkable property of the latter. Apart from formation of two-component complexes by guest and CD molecules, the formation of ternary complexes in which coinclusion of a third component occurs have also been reported. − Recently, the formation of both binary and ternary β-cyclodextrin (β-CD) complexes of 4 H -1-benzopyran-4-thione (benzopyranthione, BPT), whose structure is shown in Figure , has been reported. , BPT has proved to be a very convenient probe for studies of the microenvironment of the CD cavity because its spectral and photophysical properties strongly depend on its milieu. − , The linearity of the Benesi−Hildebrand plot of 1/( A 0 − A ) versus 1/[β-CD] T , where A 0 and A are the absorbances for the total β-CD concentration equal to 0 and [β-CD] T , respectively, indicates that the stoichiometry of the binary complex is 1:1. ,, A similar plot based on the changes in phosphorescence intensity upon addition of β-CD confirms this stoichiometry 1 Structural formula of 4 H -1-benzopyran-4-thione (BPT). …”

Section: Introductionmentioning

confidence: 99%

Ternary Complexes of 4H-1-Benzopyran-4-thione with β-Cyclodextrin and Alcohols. Dramatic Effect of Complex Formation on Fluorescence and Phosphorescence Intensity

1998

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The effect of coinclusion of alcohol (ROH) on the stoichiometry, stability, spectral, as well as photophysical properties of β-cyclodextrin (β-CD) complexes of 4H-1-benzopyran-4-thione (BPT) was studied. Although the binary complex was of 1:1 stoichiometry, the formation of ternary complexes of 1:2:2 BPT:ROH:β-CD stoichiometry was observed. The formation of the ternary complexes is revealed by a dramatic enhancement of fluorescence from the second excited singlet state and phosphorescence occurring from the two lowest thermally equilibrated triplet states. The increase in intensities of these emissions is discussed in terms of shielding the emissive molecule from bulk water molecules and expulsion (perhaps still partial) of water molecules coincluded with the BPT molecule in the binary complex. Even the coinclusion with a molecule that acts in solution as a very efficient quencher of BPT phosphorescence led to a very strong phosphorescence enhancement, which indicates that there is a spatial separation of reactive centers of the two coincluded molecules. The possible reasons for the changes in the shape in the phosphorescence spectrum and the appearance of vibrational structure in the S2 band in the absorption spectrum are also discussed. The stability constants of the ternary complexes determined from absorption, fluorescence, and phosphorescence measurements depended strongly on the molecular size and structure of a coincluded alcohol.

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Fluorescence in Organized Assemblies

Hinze¹

2000

Encyclopedia of Analytical Chemistry

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This article provides an overview of the general properties of organized assembly (ordered media) systems such as aqueous surfactant and bile salt micelles, lipid and surfactant vesicles (liposomes) and cyclodextrins (CDs) and summarizes their utilization to enhance the performance of analytical fluorescence measurements. In many instances, organic molecules and metal complex species, when included within a CD cavity or solubilized and bound to surfactant aggregates, exhibit enhanced fluorescence. This gives rise to improved detectability of such analytes. The altered microenvironment within the organized medium is capable of impeding the interfering action of other species (inorganic or organic) present in the sample matrix. This often can improve the selectivity of the analytical method. These benefits of improved sensitivity and selectivity arise from the compartmentalization, isolation and shielding of the excited singlet state of the guest analyte from quenching and nonradiative decay processes as well as prevent side reactions that otherwise can occur in bulk solution (or sample matrix). In addition, organic solvents or time‐consuming extraction steps can be avoided owing to the increased solubility of the nonpolar organic or inorganic reagents and/or analyte molecules in water in the presence of the organized medium; allowing for the use of an aqueous medium to perform the procedure. The possibility of conducting reactions and forming fluorescent organic or metal chelates in micellar (or other organized) media that are not observed in a bulk homogeneous solvent system serves to expand the scope of chemistries that one can consider using to design/develop new, unique and improved fluorescent assays. Numerous representative examples of fluorescent methods for determination of both organic and inorganic analytes are provided which serve to illustrate the advantages and benefits accrued from the use of the micelles, vesicles, liposomes or CDs in such procedures. Some experimental considerations and cautions to keep in mind when utilizing organized media are also delineated. An extensive reference section is provided so that the interested reader can easily refer to such for more detailed information on these systems and topics.

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Spectral and Photophysical Properties of Aromatic Thiones in Micellar Systems: Xanthione as Convenient Absorption and Emission Probes

Cited by 10 publications

References 31 publications

Closed Nanocontainer Enables Thioketones to Phosphoresce at Room Temperature in Aqueous Solution

Closed Nanocontainer Enables Thioketones to Phosphoresce at Room Temperature in Aqueous Solution

Ternary Complexes of 4H-1-Benzopyran-4-thione with β-Cyclodextrin and Alcohols. Dramatic Effect of Complex Formation on Fluorescence and Phosphorescence Intensity

Fluorescence in Organized Assemblies

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