Synthesis and studies on spectroscopic as well as electron donating properties of the two alkoxy benzo[b]thiophenes

Misra, T. N.; Ganguly, Tapan; Kamila, Sukanta; Basu, C.; De, Avik

doi:10.1016/s1386-1425(01)00467-x

Cited by 13 publications

(10 citation statements)

References 22 publications

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“…The observed values indicate that the present DMIs act as electron donors (D) in the presence of 9CNA which in turn serves as an electron accepting species (A) in the PET reaction. The possibility of occurrence of PET within the present donor acceptor systems has been predicted by computing the Gibb's free energy of ET reactions (Δ ) from the well-known Rehm−Weller relation − is the first singlet−singlet transition energy ((0,0) band) of the acceptor and fourth term represents the coulomb stabilization term whose contribution to the value of Δ is negligible (∼0.06 eV) in highly polar solvent ACN. Δ values for different donor−acceptor systems in ACN are listed in Table .…”

Section: Resultsmentioning

confidence: 99%

Photophysics of Some Disubstituted Indoles and Their Involvements in Photoinduced Electron Transfer Reactions

et al. 2003

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Steady state electronic absorption, fluorescence emission, polarized spectra of some disubstituted indoles, 2,3-dimethylindole (23DMI), 2,5-dimethylindole (25DMI), and 1,2-dimethylindole (12DMI), were studied in solvents of different polarity coupled with time resolved measurements. The electrochemical measurements demonstrate that DMIs should act as electron donors in photoinduced electron transfer (PET) reactions with 9Cyanoanthracene (9CNA) which serves as the electron acceptor. The photoexcited 9CNA undergoes fluorescence quenching in the presence of DMI both in nonpolar n-heptane (NH) and highly polar acetonitrile (ACN) solvents though no ground state complex formation was apparent between the reactants. In NH, the observation of the reduction of fluorescence emission intensity of 9CNA accompanied by the formation of emissive exciplex was made only for the N-methyl substituted indole 12DMI. Transient absorption spectra recorded by the laser flash photolysis technique show that photoinduced charge separation reaction proceeds both in the excited singlet and triplet states of 9CNA. Moreover, it is also established that production of the monomeric triplet of 9CNA occurs through the ion recombination mechanism. In NH, the possibility of the formation of a contact neutral radical, through the H-atom transfer reaction, as an additional route for rapid nonradiative decay of the exciplex is hinted at in the case of N-H indoles 23DMI and 25DMI. Nevertheless, it is inferred that in the case of 12DMI the observed emissive exciplex in nonpolar medium is due to its inability to form a contact neutral radical. In ACN, the major nonradiative pathway appears to be due to photoinduced ET rather than formation of exciplex.

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Section: Resultsmentioning

confidence: 99%

Photophysics of Some Disubstituted Indoles and Their Involvements in Photoinduced Electron Transfer Reactions

et al. 2003

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“…Electrochemical measurements (using standard calomel electrode as the reference electrode and tetraethylammoniumperchlorate (TEAP) as the supporting elctrolyte) were performed with a PAR model 370-4 electrochemistry system. 10,11 3. Results and discussion…”

Section: 2b Laser Flash Photolysismentioning

confidence: 99%

Photophysical properties of 5-hydroxyindole (5HI): Laser flash photolysis study

Misra

Pal

et al. 2002

J Chem Sci

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Steady state fluorescence emission and transient absorption spectra of 9fluorenone (9FL) were measured in the presence of 5-hydroxyindole (5HI) in highly polar acetonitrile (ACN) environment at ambient temperature. Cyclic voltammetry measurements demonstrate that ground state 5HI as a donor could take part in highly exothermic electron transfer (ET) reactions with excited 9FL, which should serve as electron acceptor. From the transient absorption measurements it is inferred that in geminate ion-pair (GIP) (or contact ion pair), formed initially due to photoinduced ET, the decay of this contact ion-pair occurs not only through ion recombination (back electron transfer to ground state of reactants), but through the other processes also such as proton-transfer (hydrogen abstraction) from radical cation to anion and separation of ion-pair producing the free ions. From the computed reorganisation energy parameter (λ) and experimentally observed 0 ET G ∆ − values it is hinted that there is a possibility that highly exothermic forward electron transfer reactions in the singlet state S 1 occur, within present reacting systems, in Marcus inverted region. Back transfer seems to follow the same path. Investigations with similar other reacting systems are underway.

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“…This salt decomposes, forming the corresponding carbonyl (methanal in this case),12 sulfide (dimethyl sulfide here), and HI (Scheme ). It is also well known that methanal and methanol, together in the presence of HI, can generate iodomethyl methyl ether 13, 14. We demonstrated above that iodomethyl methyl ether can act as an electrophile in the Ciucanu and Kerek alkylation, and thus attach to any of the carbohydrate hydroxyl groups in the same way that methyl iodide methylates hydroxyl groups.…”

Section: Resultsmentioning

confidence: 54%

Characterisation and proposed origin of mass spectrometric ions observed 30 Th above the ionised molecules of per‐O‐methylated carbohydrates

Robinson¹,

Routledge²,

Thomas‐Oates³

2005

Rapid Comm Mass Spectrometry

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Derivatisation of carbohydrates by permethylation significantly improves the mass spectrometric intensity of carbohydrate-derived ions and allows more readily interpretable fragmentation; in addition, samples are conveniently separated from salts, and larger oligosaccharides are more readily ionised. It has previously been recognised that, in the mass spectra of permethylated carbohydrates, a series of ions indicating species 30 Da larger than the fully methylated carbohydrate molecules are also observed. These species have not been characterised in the literature despite their apparently ubiquitous occurrence in the mass spectra of permethylated carbohydrates. Tandem mass spectrometry (MS/MS) experiments were performed on permethylated carbohydrates and reduced permethylated carbohydrates that exhibit the artefact, demonstrating that the artefact is not reducing terminal specific, and that the artefact can be introduced at any hydroxyl residue. It was further demonstrated through the use of different alkylation reagents that the origin of this artefact group is the alkylating reagent itself. It is proposed that side reactions that occur between the permethylation reagents allow the production of small amounts of iodomethyl methyl ether. This reagent can then compete with methyl iodide for reaction with the carbohydrate -OH groups. The result is partial incorporation of a methoxymethyl moiety instead of a methyl group, detected as '+30' artefact ions.

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Synthesis and studies on spectroscopic as well as electron donating properties of the two alkoxy benzo[b]thiophenes

Cited by 13 publications

References 22 publications

Photophysics of Some Disubstituted Indoles and Their Involvements in Photoinduced Electron Transfer Reactions

Photophysics of Some Disubstituted Indoles and Their Involvements in Photoinduced Electron Transfer Reactions

Photophysical properties of 5-hydroxyindole (5HI): Laser flash photolysis study

Characterisation and proposed origin of mass spectrometric ions observed 30 Th above the ionised molecules of per‐O‐methylated carbohydrates

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