Electronic spectroscopy of aromatic Schiff bases. V. Specific interactions involved between some typical benzylideneaniline molecules and small polar molecules

1982 ◽  
Vol 60 (18) ◽  
pp. 2332-2339 ◽  
Author(s):  
Michel Belletete ◽  
Gilles Durocher
Keyword(s):  
Radiative Decay ◽  
Polar Solvent ◽  
Electronic Spectroscopy ◽  
Quantum Yields ◽  
Polar Molecules ◽  
Strong Electron ◽  
Decay Constants ◽  
Fluorescence Quantum Yields ◽  
Polar Species ◽  
Solvent Molecules

Fluorescence quantum yields [Formula: see text], theoretical first-singlet radiative decay constants (kF(t)), and first-singlet non-radiative decay constants (knr) of some benzylideneanilines (BA) dissolved in methylcyclohexane have been obtained. High values of knr are interpreted by the twisting of the molecules around the azomethine bond (C=N) in the first singlet excited state. The absorption spectra of some BA's have also been obtained in methylcyclohexane with various added amounts of polar molecules. BA's with strong electron-donor and/or strong electron-acceptor substituents in the para positions give rise to the formation of ground state complexes with small polar molecules. The stoichiometry of the complex is one BA molecule for two polar solvent molecules; when ethanol is used as a polar solvent, it is further involved in hydrogen bonding formation. The fluorescence spectra of 4-dimethylaminobenzylidene-4′-nitroaniline have been obtained in methylcyclohexane with various added amounts of polar species. The results are interpreted by the formation of exciplexes with polar compound. The Lippert–Mataga theory and the more generalized Kawski theory failed to explain the solute-solvent interactions disussed in this paper.

scholarly journals Inverted energy gap law for the nonradiative decay in fluorescent floppy molecules: larger fluorescence quantum yields for smaller energy gaps

2019 ◽  
Vol 6 (12) ◽  
pp. 1948-1954 ◽  
Author(s):  
Junqing Shi ◽  
Maria A. Izquierdo ◽  
Sangyoon Oh ◽  
Soo Young Park ◽  
Begoña Milián-Medina ◽  
...  
Keyword(s):  
Radiative Decay ◽  
Energy Gap ◽  
Quantum Yields ◽  
Nonradiative Decay ◽  
Fluorescence Quantum Yields ◽  
Energy Gaps ◽  
Energy Gap Law ◽  
Solution Increase ◽  
Floppy Molecules ◽  
Franck Condon

The non-radiative decay of substituted dicyano-distyrylbenzenes in solution increase with the Franck–Condon energy, being opposite to the conventional energy gap law.

The influence of phenylethynyl linkers on the photo-physical properties of metal-free porphyrins

2000 ◽  
Vol 04 (07) ◽  
pp. 669-683 ◽  
Author(s):  
GARY A. BAKER ◽  
FRANK V. BRIGHT ◽  
MICHAEL R. DETTY ◽  
SIDDHARTH PANDEY ◽  
COREY E. STILTS ◽  
...  
Keyword(s):  
Excited State ◽  
Radiative Decay ◽  
Phenyl Group ◽  
Quantum Yields ◽  
Fluorescence Lifetimes ◽  
Strongly Coupled ◽  
Metal Free ◽  
Fluorescence Quantum Yields ◽  
Porphyrin Core ◽  
Absorbance Spectra

Series of 5,10,15,20-tetraarylporphyrins 1 and 5,10,15,20-tetrakis[4-(arylethynyl)phenyl]porphyrins 2 were prepared via condensation of pyrrole with the appropriate benzaldehyde or 4-(arylethynyl)benzaldehyde derivative (3). Condensation of meso-phenyldipyrromethane with mixtures of benzaldehyde and 4-(trimethylsilyl-ethynyl)benzaldehyde gave a separable mixture of mono- (6), bis- (both cis-7 and trans-8) and tris[4-(trimethylsilylethynyl)phenyl]porphyrin (9). Following removal of the trimethylsilyl groups of 6–9, the 4-ethynylphenyl groups of 11–14 were coupled to 1-iodo-3,5-di(trifluoromethyl)benzene with Pd ( OAc )2 to give 15–18 bearing one, two (both cis- and trans-) and three 4-[bis-3,5-(trifluoromethyl)phenylethynyl]phenyl groups respectively. Coupling of 11 and 1-iodo-4-nitrobenzene with Pd ( OAc )2 gave porphyrin 19 with one 4-(4-nitrophenylethynyl)phenyl group. Porphyrin 24 with a p-quinone linked to the porphyrin core via a phenylethynyl group was prepared via similar chemistry. The absorbance spectra, emission maxima, excited-state fluorescence lifetimes, quantum yields of fluorescence, rates of fluorescence and rates of non-radiative decay were measured for each of the porphyrins. Absorbance spectra and emission maxima were nearly identical for all the porphyrins of this study, which suggests that the aryl groups and 4-(arylethynyl)phenyl groups are not strongly coupled to the porphyrin core in these metal-free compounds. Fluorescence quantum yields and rates of radiative decay were larger for porphyrins bearing 4-(arylethynyl)phenyl groups, while excited-state fluorescence lifetimes were somewhat shorter. These effects were additive for each additional 4-(arylethynyl)phenyl group.

The Relaxation Time of the Orientation Polarization and its Influence on the Luminescence Intensity Distribution*

1984 ◽  
Vol 39 (5) ◽  
pp. 509-510 ◽  
Author(s):  
A. Kawski
Keyword(s):  
Relaxation Time ◽  
Intensity Distribution ◽  
Luminescence Intensity ◽  
Polar Solvent ◽  
Characteristic Relaxation Time ◽  
Polar Molecules ◽  
Spectral Emission ◽  
Orientation Polarization ◽  
Trans Stilbene ◽  
Solvent Molecules

The characteristic relaxation time τR of the orientation polarization of polar solvent molecules around polar luminescent molecules influences the spectral emission distribution depending on τF > τR or τF ≦ τR. This is shown on the luminescence of the polar molecules 4-isocyanate- 4'-dimethylamino-transstilbene (CDS), 4-isocyanate- 4'-methoxy-trans-stilbene (CMS) and 4-isocyanate- 3',4'-dimethoxy-trans-stilbene (CDMS) (having a very short lifetime τF < 10 ps) in chlorobenzene

scholarly journals Free Rotor Styrylcyanine Chromogens

1986 ◽  
Vol 6 (6) ◽  
pp. 381-389 ◽  
Author(s):  
M. M. Habashy ◽  
M. S. Antonious ◽  
M. Abdel-Kader ◽  
M. S. A. Abdel-Mottaleb
Keyword(s):  
Radiative Decay ◽  
Decay Channel ◽  
Stokes Shift ◽  
Solvent Polarity ◽  
Quantum Yields ◽  
Excitation Wavelength ◽  
Charge Densities ◽  
Fluorescence Quantum Yields ◽  
Organized Assemblies ◽  
Sensitive Function

Fluorescence spectra (maximum wavelength λF) and fluorescence quantum yields (φF) were measured for four structurally related styrylcyanine chromogens of the pyridinium and quinolinium type (1–4) in different solvents at ambient temperature and 77 K. The response of λF and φF values to changes in solvent polarity, solvent hydrogen bonding donor strength, viscosity and temperature was a sensitive function of chromogen structure. The sensitivities of the λF and φF values correlate with the degree of charge transfer character of the S1,CT state; Stokes shift of fluorescence was progressively decreased while φF value was enhanced as the CT character of S1,CT state increases. Moreover, a large edge-excitation red shift was observed in ethanol glass at 77 K. The dominant photophysical features for these dyes are discussed in terms of strong emission from an intramolecular CT state characterized by different solvation sites indicated by the observation of the excitation-wavelength dependent phenomenon in ethanol at 77 K and an important non-radiative decay channel involving rotation of the different parts of molecules leading to a more relaxed weakly fluorescent S1,CT created in fluid media. The viscosity dependence of fluorescence properties (a marked increase in φF was observed with increasing viscosity) suggests that these dyes can be useful reporters of microviscosity for different sites in various organized assemblies. Moreover, it was suggested that increasing H-bonding donor strength of the solvent activates a rotatory non-radiative decay channel probably by localizing charge densities and decreasing CT nature of the S1,CT state.

Fluorescence behaviour of some 4-substituted halobenzenes

1985 ◽  
Vol 50 (8) ◽  
pp. 1753-1763 ◽  
Author(s):  
Bohumír Koutek ◽  
Lubomír Musil ◽  
Jiří Velek ◽  
Milan Souček
Keyword(s):  
Decay Rate ◽  
Radiative Decay ◽  
Mean Value ◽  
Quantum Yields ◽  
Intersystem Crossing ◽  
Radiative Decay Rate ◽  
Fluorescence Quantum Yields ◽  
Band Position ◽  
Fluorescence Characteristics ◽  
Acetonitrile Solutions

The fluorescence characteristics of 4-substituted chloro and fluorobenzenes I and II were studied in isooctane and acetonitrile solutions. It was found that all compounds exhibit a weak (substituent and solvent dependent) fluorescence in the range 305-370 nm with quantum yields 1.2 . 10-2-2.3 . 10-1. The relation between the substituent nature and fluorescence band position may be quantified by log νf~ = ρσp + log νf~0, the magnitude of the shift paralleling the donor strength of the substituent. Fluorescence quantum yields are increased approximately by a factor 2 on going from isooctane to acetonitrile and solvent-induced shifts are proportional to the static dipole moment change Δμ which occurs upon excitation. Radiative decay rate varies only slightly around a mean value of 5 . 107 s-1 and shows no substantial difference between chloro (I) and fluoro (II) derivatives. The non-radiative decay rate (of the order ~ 109 s-1) was found to be about 5 times higher in the case of chloro compounds due to the more efficient S1 - Tn intersystem crossing.

Photophysical and photochemical properties of novel phthalocyanines bearing non-peripherally substituted mercaptoquinoline moiety

2012 ◽  
Vol 16 (07n08) ◽  
pp. 845-854 ◽  
Author(s):  
Göknur Yaşa ◽  
Ali Erdoğmuş ◽  
Ahmet Lütfi Uğur ◽  
M. Kasım Şener ◽  
Ulvi Avcıata ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Electronic Spectroscopy ◽  
Quantum Yields ◽  
Solubility In Water ◽  
Fluorescence Quantum Yields ◽  
H Nmr ◽  
Good Solubility ◽  
Ft Ir ◽  
Photochemical Properties ◽  
First Time

The synthesis, photophysical and photochemical properties of nonperipherally (α) mercaptoquinoline substituted Zn(II) , TiO(IV) and Mg(II) and quaternized Zn(II) phthalocyanines are described for the first time. These complexes (2 to 5) and their precursor are characterized by elemental analysis, FT-IR, 1H NMR, electronic spectroscopy as well as mass spectroscopy. Complexes 2, 4 and 5 have good solubility in organic solvents such as CHCl3 , DCM, DMSO, DMF, THF and toluene and are not aggregated in all solvents within a wide concentration range. Complex 3 showed very good solubility in water as well as DMSO and DMF. General trends are described for singlet oxygen, photodegradation and fluorescence quantum yields of these complexes in DMSO and DMF. While complex 2 has higher singlet oxygen and fluorescence quantum yields than 3, 4 and 5, complex 4 has higher fluorescence quantum yields in DMF and DMSO than 2, 3 and 5. The effect of the solvents and metal on the photophysical and photochemical parameters of the metallophthalocyanines are also reported.

Decay dynamics of aromatic thione triplet states in fluid solution

1983 ◽  
Vol 61 (5) ◽  
pp. 894-900 ◽  
Author(s):  
A. Safarzadeh-Amiri ◽  
R. E. Verrall ◽  
R. P. Steer
Keyword(s):  
Room Temperature ◽  
Radiative Decay ◽  
Quantum Yields ◽  
Triplet States ◽  
Fluid Solution ◽  
Excitation Spectra ◽  
Decay Constants ◽  
Diffusion Controlled ◽  
Phosphorescence Emission ◽  
Group Rotation

Phosphorescence emission and excitation spectra, quantum yields, and lifetimes of several aromatic thiones have been measured in fluid solution at room temperature. Excitation to any of the excited electronic states accessible in the near-uv and visible regions of the spectrum results in population of the lowest triplet state with near unit quantum yield. Triplets of relatively inflexible thiones decay non-radiatively with rate constants of the order of 105 s−1 whereas thiones capable of higher amplitude flexion or group rotation exhibit non-radiative decay constants ≥ 107 s−1 at infinite dilution in aprotic solvents. Self-quenching occurs at diffusion-controlled rates.

Synthesis, photophysical and photochemical studies of novel liquid crystalline phthalocyanines

2009 ◽  
Vol 13 (06) ◽  
pp. 722-738 ◽  
Author(s):  
M. Menaf Ayhan ◽  
Mahmut Durmuş ◽  
Ayşe G. Gürek
Keyword(s):  
Liquid Crystalline ◽  
Preliminary Investigation ◽  
Electronic Spectroscopy ◽  
Quantum Yields ◽  
Scanning Calorimetry ◽  
Fluorescence Quantum Yields ◽  
Polarized Microscopy ◽  
Aggregation Behaviors ◽  
Photochemical Properties ◽  
New Compounds

Ni(II) and Zn(II) phthalocyanines carrying four or eight branched oligo(ethyleneoxy)-thia groups on peripheral positions have been synthesized from new phthalonitrile derivatives. The new compounds have been characterized by elemental analysis, IR, NMR, mass spectra and electronic spectroscopy. The aggregation behaviors of the phthalocyanine complexes were studied in different solvents and concentrations. General trends are described for photodegradation, singlet oxygen and fluorescence quantum yields, and fluorescence lifetimes of these compounds in dimethylsulfoxide (DMSO). The effects of the substitution on the photophysical and photochemical parameters of the nickel(II) (3a and 4a) and zinc(II) phthalocyanines (4b) are also reported. The octasubstituted zinc(II) complex (3b) is not stable for these measurements. Preliminary investigation of the photophysical and photochemical properties of phthalocyanine complexes are very useful for further PDT applications. The mesogenic properties of these new materials were studied by differential scanning calorimetry (DSC), optical polarized microscopy and X-ray investigations.

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