Prototropic reactions for 1-, 2-, and 4-fluorenamides in the ground and excited singlet states

1988 ◽  
Vol 66 (9) ◽  
pp. 2375-2385 ◽  
Author(s):  
Ramasamy Manoharan ◽  
Sneh K. Dogra
Keyword(s):  
Fluorescence Spectra ◽  
Medium Effect ◽  
Long Wavelength ◽  
Protonation Reaction ◽  
Singlet States ◽  
Wavelength Absorption ◽  
Excited Singlet States ◽  
Acidity Scale ◽  
Ring Carbon Atom ◽  
Long Wavelength Absorption Band

Absorption and fluorescence spectra of 1-, 2- and 4-fluorenamides (1-FAm, 2-FAm, 4-FAm) were studied in different solvents and at various acid concentrations. This study indicates that the long wavelength absorption band is long-axis polarised in 2-FAm whereas in 1-FAm and 4-FAm, it is composed of long- and short-axis polarised transitions. The —CONH2 group in 1-FAm and 4-FAm is coplanar with the fluorene moiety, whereas the same group in 2-FAm is non-coplanar with the fluorene ring in non-polar solvents, both in S0 and S1 states, but attains coplanarity in the polar and hydrogen bonding solvents in the S1 state. Hammett's acidity scale is not valid for the protonation reaction of amides and a medium effect is observed on the absorption spectra of the monocations in strong sulphuric acid. The prototropic equilibrium for the protonation of ring carbon atom is not established in the S1 state, due to the slower rate of protonation reaction. Proton-induced fluorescence quenching of the monocations is followed before the monocations are being protonated.

scholarly journals Электронное строение и спектрально-флуоресцентные свойства лазерных красителей тиопирило-4-трикарбоцианинов

2021 ◽  
Vol 129 (7) ◽  
pp. 862
Author(s):  
А.А. Ищенко ◽  
И.В. Курдюкова ◽  
М.В. Богданович ◽  
С.Л. Бондарев ◽  
А.А. Романенко ◽  
...  
Keyword(s):  
Radiative Transition ◽  
Polymethine Chain ◽  
Long Wavelength ◽  
Vibronic Interactions ◽  
Wide Range ◽  
Wavelength Absorption ◽  
Fluorescent State ◽  
Long Wavelength Absorption Band ◽  
Angle Of Rotation ◽  
Ab Initio Dft

It was found that the long-wavelength absorption band of the laser dye IR 1061 and its analogue with an unsubstituted polymethine chain is strongly broadened and decreases in intensity in polar solvents, while the fluorescence band remains narrow and practically does not change in a wide range of solvent polarities. Based on the quantum-chemical calculations of these dyes by the ab initio DFT/B3LYP/6-31G (d,p) and TDDFT methods, taking into account the polarity of the medium by the PCM method, it is shown that the reason for this difference is the weakening of solvation in the fluorescent state as compared to the ground state due to the greater equalization of the charge in the first than in the latter. An increase in the alternation of bond orders in the polymethine chain in the fluorescent state was found, which causes an increase of vibronic interactions in the radiative transition as compared to the absorptive one. Spectral effects caused by a change in the angle of rotation of phenyl groups in the thiopyrylium cycle upon excitation have been analyzed.

Erstmaliger Nachweis von π–π Dimerenbildung bei stabilen 1,4-Dialkylchinoxalinium-Radikalkationen. Struktur, Spektroskopie und Magnetismus / First Evidence for π-π-Dimerization of the Stable 1,4-Dialkylquinoxalinium Radical Cations. Structure, Spectroscopy and Magnetism

1993 ◽  
Vol 48 (9) ◽  
pp. 1181-1186 ◽  
Author(s):  
H.-D. Hausen ◽  
Wolfgang Kaim ◽  
Andreas Schulz ◽  
Michael Moscherosch ◽  
Jeanne Jordanov
Keyword(s):  
Solid State ◽  
Magnetic Measurements ◽  
Magnetic Moments ◽  
Cation Radical ◽  
Radical Cations ◽  
Long Wavelength ◽  
Wavelength Absorption ◽  
Molecular Structure Analysis ◽  
Long Wavelength Absorption Band ◽  
Quinoxaline Ring

Crystal and molecular structure analysis of 1,4-diethylquinoxalinium iodide shows a virtually planar quinoxaline ring with 11 conjugated π-electrons. In contrast to the triiodide of the 1,4,6,7-tetramethyl derivative or to the tetraphenylborate salt of 1,4-diethylquinoxalinium cation radical the iodide exhibits π-π-dimerized radical cations in the solid state with synplanar ethyl groups and a rather small intermolecular distance of about 315 pm between the π-planes of the primarily interacting 1,4-diazine rings. Solid state magnetic measurements between 2 and 300 K show considerably diminished magnetic moments due to partial spin-pairing, and UV/VIS spectroscopic measurements in acetonitrile reflect the π—π-interaction in solution through the appearance of a long-wavelength absorption band.

Elaboration of an unexplored substitution site in synthetic bacteriochlorins

2015 ◽  
Vol 19 (07) ◽  
pp. 887-902 ◽  
Author(s):  
Nuonuo Zhang ◽  
Kanumuri Ramesh Reddy ◽  
Jianbing Jiang ◽  
Masahiko Taniguchi ◽  
Roger D. Sommer ◽  
...  
Keyword(s):  
Bathochromic Shift ◽  
Fluorescence Emission ◽  
Bacterial Photosynthesis ◽  
Alkoxy Group ◽  
The Self ◽  
X Ray ◽  
Long Wavelength ◽  
Substitution Site ◽  
Wavelength Absorption ◽  
Long Wavelength Absorption Band

The ability to introduce substituents at designated sites about the perimeter of synthetic bacteriochlorins – analogs of bacteriochlorophylls of bacterial photosynthesis – remains a subject of ongoing study. Here, the self-condensation of a dihydrodipyrrin-dioxolane affords a 5-[2-(trimethylsiloxy)ethoxy]bacteriochlorin. Like a 5-methoxybacteriochlorin, the latter undergoes regioselective bromination at the 15-position, directed by the distal 5-alkoxy group. On the other hand, attempted bromination of a bacteriochlorin bearing a 5-(2-hydroxyethoxy) group resulted in intramolecular ether formation with the adjacent β-pyrroline position to give an annulated dioxepine ring (confirmed by single-crystal X-ray structural analysis). The hydroxyethoxy group at the 5-position can be derivatized by acylation. In addition, the installation of auxochromes (methoxycarbonyl, phenylethynyl) at the β-pyrrole rings causes a substantial bathochromic shift of the long-wavelength absorption band (812 nm) and companion fluorescence emission band (821 nm). Taken together, the modification of the 5-substituent complements existing methods for installing a single substituent on the bacteriochlorin macrocycle.

Synthesis and spectroscopic properties of benzo- and naphthofuryl-3-hydroxychromones

2001 ◽  
Vol 79 (4) ◽  
pp. 358-363 ◽  
Author(s):  
Andrey S Klymchenko ◽  
Turan Ozturk ◽  
Vasyl G Pivovarenko ◽  
Alexander P Demchenko
Keyword(s):  
Excited State ◽  
Proton Transfer ◽  
Spectroscopic Properties ◽  
Molecular Probe ◽  
Absorption Bands ◽  
Methyl Group ◽  
Long Wavelength ◽  
Excited State Proton Transfer ◽  
Wavelength Absorption ◽  
Long Wavelength Absorption Band

With the focus of designing new fluorescent probes, four new 3-hydroxy-chromone derivatives bearing benzofuran and naphthofuran groups were synthesized. They show bathochromic absorption shifts relative to 3-hydroxyflavone with the ability of retention to display the excited-state proton transfer. Disruption of the planarity by the methyl group in the furan ring leads to a decrease of both the extinction coefficient and the contribution of long wavelength absorption band, while molecules without a methyl group showed two distinct absorption bands. Shifts to longer wavelengths are also observed in fluorescent spectra, and the absence of the methyl group results in a dramatic increase of fluorescence quantum yield and lifetime. Of the extended 3-hydroxychromone derivatives, 3-hydroxy-2-naphtho[2,1-b]furan-2-yl-chromone has shown comparable, and in some cases better, absorption and fluorescence properties than the 3-hydroxychromones synthesized so far, which make it a highly promising candidate as molecular probe for analytical chemistry, biophysics, and cellular biology.Key words: benzo- and naphthofuryl-3-hydroxyflavone, synthesis, electronic spectra, fluorescence, excited state proton transfer.

scholarly journals The fluorescence analysis of laser photolysis of phenols in water

2002 ◽  
Vol 4 (2) ◽  
pp. 79-83 ◽  
Author(s):  
O. Tchaikovskaya ◽  
I. Sokolova ◽  
O. Bazyl ◽  
V. Swetlichnyi ◽  
T. Kopylova ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Laser Light ◽  
Fluorescence Analysis ◽  
Dynamic Changes ◽  
Long Wavelength ◽  
Chlorine Substitution ◽  
Wavelength Absorption ◽  
Chemical Techniques ◽  
Long Wavelength Absorption Band ◽  
Photolysis Of Phenol

Photolysis of phenol andp-chlorophenol exposed to KrCl- and Nd-YAG laser light is studied by electron spectroscopy and fluorescence and quantum chemical techniques. The decrease of the quantum yield of phenol fluorescence with increase in the excitation energy is not related to dynamic changes in the intramolecular photophysical processes; rather this is a result of increased photoreaction efficiency. Chlorine substitution for para-state of phenol is shown to strengthen the OH-bond in excitation into the long wavelength absorption band.

Surface photochemistry: use of spiropyrans as indicators of surface polarity

1984 ◽  
Vol 62 (5) ◽  
pp. 1001-1002 ◽  
Author(s):  
Paul De Mayo ◽  
Ali Safarzadeh-Amiri ◽  
S. King Wong
Keyword(s):  
Absorption Band ◽  
Silica Gel ◽  
Solvent Polarity ◽  
Surface Polarity ◽  
Long Wavelength ◽  
Wavelength Absorption Band ◽  
Wavelength Absorption ◽  
Long Wavelength Absorption Band

The position of the long wavelength absorption band in the spectrum of a spiropyran is sensitive to solvent polarity. This property has been used to determine the polarity of the silica gel surface.

Synthesis of perylene-porphyrin dyads for light-harvesting studies

2002 ◽  
Vol 06 (10) ◽  
pp. 626-642 ◽  
Author(s):  
Robert S. Loewe ◽  
Kin-ya Tomizaki ◽  
Fabien Chevalier ◽  
Jonathan S. Lindsey
Keyword(s):  
Ground State ◽  
Light Harvesting ◽  
Molecular Architecture ◽  
Efficient Energy Transfer ◽  
Aryl Group ◽  
Long Wavelength ◽  
Efficient Energy ◽  
Wavelength Absorption ◽  
Meso Position ◽  
Long Wavelength Absorption Band

The spectral coverage of porphyrin-based light-harvesting arrays can be enhanced through the use of suitable accessory pigments. Perylene-monoimide dyes can serve as valuable accessory pigments with porphyrins. To investigate the choice of perylene-monoimide and the effects of molecular architecture on light-harvesting efficacy, five perylene-porphyrin dyads were prepared. Each dyad employs a diphenylethyne linker that bridges the perylene N-imide site and the porphyrin meso-position. Three dyads incorporate a mono-phenoxy perylene at the o-, m-, or p-position of the meso-aryl group on the porphyrin. The two remaining dyads incorporate a perylene-monoimide (bearing zero or three phenoxy substituents) at the p-position of the meso-aryl group on the porphyrin. The introduction of phenoxy groups on the perylenes increases the solubility, a key requirement for use in light-harvesting arrays. The long-wavelength absorption band of the perylene shifts from 506 nm to 532 or 533 nm upon substitution with one or three phenoxy groups, respectively. The synthesis of the dyads entails Pd -mediated coupling of a bromo-perylene and an ethynyl porphyrin, or the mixed-aldehyde condensation with a perylene-aldehyde, mesitaldehyde, and pyrrole. Five perylene-monoimide dyes bearing an ethyne or bromo substituent at the p-position of the N-aryl unit were developed for this modular chemistry. Each perylene-porphyrin dyad exhibits efficient energy transfer from the excited perylene to the ground-state porphyrin.

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