Surface photochemistry: Diffuse reflectance studies of thioketones included into p-tert-butylcalix[6 and 8]arenes

Ferreira, L.F. Vieira; Machado, I. Ferreira; Oliveira, Anabela S.; Silva, José Paulo da; Krawczyk, Alina; Sikorski, Marek

doi:10.1016/j.molstruc.2006.04.049

Cited by 3 publications

(9 citation statements)

References 25 publications

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“…Also a new mechanism of deactivation, namely triplet-triplet annihilation from the S 2 state occurs upon inclusion within the nanocavities of these two calixarenes. For XT inclusion into calix[8]arene and for BPT inclusion complexes within both calixarenes similar luminescence behavior was observed [13].…”

Section: Inclusion Complexes Of P-tert-butylcalixarenes/thioketonessupporting

confidence: 61%

“…The inclusion of the two thioketones, xanthione (XT) and 4H-1-benzopyran-4-thione (BPT, Scheme 6) into p -tertbutylcalix[6]arene and p-tert-butylcalix[8]arene revealed, in air equilibrated conditions, for the inclusion complexes of both probes within calix[6]arene and calx[8]arene, the existence of fluorescence and delayed fluorescence emission (S 2 S 0 emissions in the nanosecond and microsecond time ranges respectively) and also of phosphorescence emission [13].…”

Section: Inclusion Complexes Of P-tert-butylcalixarenes/thioketonesmentioning

confidence: 99%

“…The use of chromatographic methods (GC-MS) allowed to identify the formation of the correspondent ketones -xanthone and chromone -and also hydroxy-thioketones following laser irradiation at 355 or 337 nm [13].…”

Section: Inclusion Complexes Of P-tert-butylcalixarenes/thioketonesmentioning

confidence: 99%

“…Other organic molecular probes were also used for inclusion complex formation studies with calixarenes [13][14].…”

Section: Introductionmentioning

confidence: 99%

“…The excitation wavelength was 337 nm in all cases. Reprinted from reference[13] with permission of Elsevier. Panel (a) Fluorescence emission of XT included in CLX[6]; curves were recorded every 1 ns after the laser pulse (t 0 = 1 ns; gate width = 100 ns).…”

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confidence: 99%

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Surface Photochemistry: Organic Molecules within Nanocavities of Calixarenes

Ferreira¹,

Machado²

2007

CDDT

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In order to gain more information regarding photochemical processes in heterogeneous environments (opaque or powdered samples) laser induced time resolved luminescence and diffuse reflectance transient absorption spectroscopies were used for the study of benzophenone (and other neutral organic molecules) as guests and p-tert-butylcalix[n]arenes with n = 4, 6 and 8 (H(n)CLX[n]) and partially or totally O-propylated p-tert-butylcalix[4]arenes (H(n)Pr(m)CLX[4], n = 2, 1 and 0; m = 2, 3 and 4, respectively) were used as hosts. One of the main conclusions was that the solid support can deeply affect or even control the photochemistry of an adsorbed probe. A simple new methodology for lifetime distribution analysis of the decay of the probes included into calixarenes and other nanocavities was applied with success for decay data obtained with the use of intensified charge couple devices, i.e. intensified charge couple devices, ICCDs. Diffuse reflectance laser flash photolysis and gas chromatography - mass spectrometry techniques also provided complementary information, the former about transient species and the latter regarding the final products formed after light absorption.

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Section: Inclusion Complexes Of P-tert-butylcalixarenes/thioketonessupporting

confidence: 61%

Section: Inclusion Complexes Of P-tert-butylcalixarenes/thioketonesmentioning

confidence: 99%

Section: Inclusion Complexes Of P-tert-butylcalixarenes/thioketonesmentioning

confidence: 99%

“…Other organic molecular probes were also used for inclusion complex formation studies with calixarenes [13][14].…”

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Surface Photochemistry: Organic Molecules within Nanocavities of Calixarenes

Ferreira¹,

Machado²

2007

CDDT

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Spectral Dynamics of Nitro Derivatives of Xanthione in Solutions

et al. 2019

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Nitro derivatives of xanthione, 2,7-dinitro-9Hxanthene-9-thione and 2,4,7-trinitro-9H-xanthene-9-thione, have been first synthesized and their stationary and transient spectra have been measured. The stationary spectra show that the attachment of the nitro groups to the xanthione scaffold leads to strong quenching of S 2 → S 0 fluorescence and the decrease of the oscillator strength of the S 2 ← S 0 electronic transition. Analysis of the transient absorption spectra uncovers the ultrafast stimulated emission quenching from the second excited state, S 2 , in the both derivatives. A kinetic scheme has been suggested to rationalize the complex spectral dynamics of the transient absorption signal. The kinetic scheme is deduced from the analysis of the transient spectra and supported by the quantum-chemical calculations, which predict the existence of a dark state and S 2 state splitting into two close levels. The ultrafast transitions between S 2 state sublevels and the transition into the dark state play a crucial role in spectral dynamics. These new features discovered in the nitro derivatives of xanthione distinguish essentially their spectral dynamics from that observed in xanthione.

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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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Surface photochemistry: Diffuse reflectance studies of thioketones included into p-tert-butylcalix[6 and 8]arenes

Cited by 3 publications

References 25 publications

Surface Photochemistry: Organic Molecules within Nanocavities of Calixarenes

Surface Photochemistry: Organic Molecules within Nanocavities of Calixarenes

Spectral Dynamics of Nitro Derivatives of Xanthione in Solutions

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

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