Photophysical and electron transfer studies of a stable carbocation

Photophysical and electron transfer properties of the stable trioxatriangulenium carbocation (1) are reported. Photophysical studies include absorption, fluorescence and phosphorescence spectra, singlet and triplet state quantum yields and lifetimes. Both the singlet and triplet excited states of 1 can accept an electron from donor molecules leading to the formation of the donor radical cation and the radical of 1. In aqueous solution, 1 can photo-oxidize DNA nucleosides such as guanosine and adenosine indicating that 1 may have potential use as a DNA cleaving agent

Photoinduced electron transfer in azatriangulenium salts

Fluorescence quenching and laser flash photolysis studies of stable azatriangulenium ions 2⊕-4⊕ are reported. The fluorescence quenching rate constants were correlated to Δ G0values. The results suggest that 2⊕ is an excited state electron acceptor and 4⊕ is an excited state electron donor. 3⊕, on the other hand, can act as an acceptor or donor in photoinduced electron transfer (PET) reactions. Laser flash photolysis studies also supported these observations. These cations thus present an interesting case, where replacement of oxygen atoms by N-alkyl groups leads to a gradual shift of photoinduced electron transfer property from an acceptor to that of a donor

Photophysical and singlet oxygen generation studies of a few water soluble triazatriangulenium salts

1047-1055The photophysical and singlet oxygen generation studies of a few water-soluble triazatriangulenium cations (TATA) are reported. The photophysical studies include absorption spectrum, fluorescence spectrum, fluorescence quantum yield, fluorescence lifetime, triplet life time, triplet quantum yield and phosphorescence spectrum. The singlet and triplet energy levels of the compounds were determined. The triplet state properties have been characterized using nanosecond laser flash photolysis studies. The singlet oxygen generation has been estimated using chemical actinometry using disodium-9,10-anthracenedipropionic acid in water and 1,3-diphenylisobenzofuran in acetonitrile as the chemical actinometers and rose bengal was used as reference

Influence of molecular shape on magnetic field effect on photo-induced geminate radical pair in SDS micellar medium

The magnetic field effects (MFEs) on the dynamics of the two radical pairs (RPs), one generated by photo-excitation of phenyl pyrilium ion (PP+) in the presence of SDS micelles and an electron donor, biphenyl, and the other similarly generated from a SDS micellar solution of biphenyl and trioxotriangulenium carbocation (OXO+), have been compared. At zero field, the RP (PP·/BP·+) has much higher recombination rate, but much lower escape rate in comparison to the RP (OXO· /BP·+). The field-dependent yields and lifetimes show saturation early ( <0.1 T) in case of the latter, but in case of the former, the saturation does not occur, not even at a field of 5 T. The results have been interpreted in terms of relaxation mechanism (RM) for MFE and expected differences in the location of the guest in the micellar host, which affects the ratio of the rate of recombination to the rate of escape

Dibutyltin Compounds Effects on PPARγ/RXRα Activity, Adipogenesis, and Inflammation in Mammalians Cells

Organotins are a group of chemical compounds that have a tin atom covalently bound to one or more organic groups. The best-studied organotin is tributyltin chloride, which is an environmental pollutant and an endocrine disruptor. Tributyltin chloride has been shown to bind to PPARγ/RXRα and induces adipogenesis in different mammalian cells. However, there are few studies with other organotin compounds, such as dibutyltins. The aim of this study was to investigate the effect of dibutyltins diacetate, dichloride, dilaurate, and maleate on the transcriptional activity of the nuclear PPARγ and RXRα receptors, and on adipogenesis and inflammation. Analogous to tributyltin chloride, in reporter gene assay using HeLa cells, we observed that dibutyltins diacetate, dichloride, dilaurate, and maleate are partial agonists of PPARγ. Unlike tributyltin chloride, which is a full agonist of RXRα, dibutyltins dichloride and dilaurate are partial RXRα agonists. Additionally, the introduction of the C285S mutation, which disrupts tributyltin chloride binding to PPARγ, abrogated the dibutyltin agonistic activity. In 3T3-L1 preadipocytes, all dibutyltin induced adipogenesis, although the effect was less pronounced than that of rosiglitazone and tributyltin chloride. This adipogenic effect was confirmed by the expression of adipogenic markers Fabp4, Adipoq, and Glut4. Exposure of 3T3-L1 cells with dibutyltin in the presence of T0070907, a specific PPARγ antagonist, reduced fat accumulation, suggesting that adipogenic effect occurs through PPARγ. Furthermore, dibutyltins dichloride, dilaurate, and maleate inhibited the expression of proinflammatory genes in 3T3-L1 cells, such as Vcam1, Dcn, Fn1, S100a8, and Lgals9. Additionally, in RAW 264.7 macrophages, tributyltin chloride and dibutyltin dilaurate reduced LPS-stimulated TNFα expression. Our findings indicate that dibutyltins diacetate, dichloride, dilaurate, and maleate are PPARγ partial agonists and that dibutyltins dichloride and dilaurate are also partial RXRα agonists. Furthermore, dibutyltins induce adipogenesis in a PPARγ-dependent manner and repress inflammatory genes in 3T3-L1 and RAW 264.7 cells. Although dibutyltins display some partial PPARγ/RXRα agonistic effects, the translation of cell-based results assays into in vivo effects on inflammation and insulin resistance is not entirely known. Nevertheless, further studies are necessary to address their effects in different periods of life and to elucidate the actions of organostanic compounds in whole-body context