Abstract:Both 2,5-bis-2(l-naphthyl)vinylpyrazJne (BNVP) and 2,5-bis-2(2-naphthyl)vinylpyrazine (B2NVP) diolefinic dyes have relatively short excited-state lifetimes, high fluorescence efficiencies and low photochemical quantum yields. BNVP solutions in dimethyl formamide and methylene chloride give amplified spontaneous emission (ASE) with a maximum at 500 nm. The low solubility of B2NVP in organic solvents does not allow the measurement of ASE for this dye. The excited state absorption spectra (ESA) of BNVP show an ab… Show more
“…Diolefinic compounds containing heterocyclic moieties of the general formula AŕCHCHArCHCHAŕ have been extensively reported as laser dyes. − A new candidate in this family of compounds is 1,4-bis[β-(2-quinolyl)vinyl]benzene (BQVB). In the present paper we report the fluorescence, lifetime, and spectral characteristics and laser action of this compound …”
The diolefinic dye BQVB is an efficient fluorescer with φ f values as high as 0.82 in n-heptane. The dye exhibits low values of the excited state lifetimes of ca. 0.4 ns. Both electronic absorption and fluorescence spectra are sensitive to medium acidity, and in acidic media a strong fluorescence is obtained at 500 nm. The laser activity of BQVB has been investigated. The dye solution in N,N-dimethylformamide (DMF) gives laser emission around 450 nm upon excitation by 337.1 nm nitrogen laser pulse. The excited state absorption S 2 r S 1 of BQVB has been measured using laser flash photolysis, and in DMF the S 2 r S 1 absorption occurs at ca. 762 nm. Energy transfer from BQVB to rhodamine 6G and to molecular oxygen has been studied. The quantum yields for the trans-cis photoisomerization (φ c ) of BQVB in different organic solvents are also reported.
“…Diolefinic compounds containing heterocyclic moieties of the general formula AŕCHCHArCHCHAŕ have been extensively reported as laser dyes. − A new candidate in this family of compounds is 1,4-bis[β-(2-quinolyl)vinyl]benzene (BQVB). In the present paper we report the fluorescence, lifetime, and spectral characteristics and laser action of this compound …”
The diolefinic dye BQVB is an efficient fluorescer with φ f values as high as 0.82 in n-heptane. The dye exhibits low values of the excited state lifetimes of ca. 0.4 ns. Both electronic absorption and fluorescence spectra are sensitive to medium acidity, and in acidic media a strong fluorescence is obtained at 500 nm. The laser activity of BQVB has been investigated. The dye solution in N,N-dimethylformamide (DMF) gives laser emission around 450 nm upon excitation by 337.1 nm nitrogen laser pulse. The excited state absorption S 2 r S 1 of BQVB has been measured using laser flash photolysis, and in DMF the S 2 r S 1 absorption occurs at ca. 762 nm. Energy transfer from BQVB to rhodamine 6G and to molecular oxygen has been studied. The quantum yields for the trans-cis photoisomerization (φ c ) of BQVB in different organic solvents are also reported.
“…Among others, donor‐substituted distyrylpyrazines are appropriate fluorophores for sensing purposes. Some had been prepared and used in optoelectronic devices, as lasing materials, and also as two‐photon absorbing dyes …”
p-aminostyryl)pyrazines with voluminous substituents on the nitrogen and in the adjacent positions were prepared via twofold aldol condensation. Absorption and emission spectra are influenced by increasing steric hindrance because the orbital overlap between nitrogen and p-system is modulated by voluminous groups. Strong solvatochromism of the fluorescence and huge Stokes shifts result from amplified donor-acceptor interaction in the excited state. Protonation occurs at the terminal amino groups first, followed by protonation of the central pyrazine.With increasing strength of acid, absorption and emission spectra are first shifted to the blue followed by a redshift.
“…The interaction of these compounds with the environment can result in significant spectroscopic changes, useful for sensing purposes [13, 14]. A few alkoxy-substituted distyrylpyrazines had been prepared [15–17] and investigated for optoelectronic devices, as emitting materials for lasing purposes [18, 19], and also as two-photon absorbing dyes [20]. The generally applied synthetic routes to styrylpyrazines are based on the Lewis acid- catalyzed condensation of aromatic aldehydes [21] and on the deprotonation of methylpyrazines and aldol condensation with aromatic aldehydes.…”
A series of linear and angular distyrylpyrazines and lateral donor groups has been prepared by aldol condensation between dimethylpyrazines and the appropriate aromatic aldehyde. The optical absorption and emission properties of these systems were studied in different solvents and media. The materials display a strong solvatochromism of the emission that is reflected by large red shifts of their fluorescence emission maxima on increasing the solvent polarity. This behaviour suggests a highly polar emitting state, which is characteristic of compounds that undergo an internal charge transfer upon excitation. Upon protonation, the UV-vis spectra are altered, and the fluorescence intensity of the neutral compound vanishes. These molecules can be used as colorimetric and luminescence polarity and pH sensors.
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