‘Excimer’ fluorescence VII. Spectral studies of naphthalene and its derivatives

1965 ◽  
Vol 284 (1399) ◽  
pp. 551-565 ◽  
Keyword(s):  
Fluorescence Spectra ◽  
Entropy Change ◽  
Spectral Studies ◽  
Pure Liquid ◽  
Methyl Ethyl ◽  
Excimer Fluorescence ◽  
Mean Values ◽  
Fluorescence Characteristics ◽  
Excimer Formation ◽  
Monomer Fluorescence

The fluorescence spectra of solutions of naphthalene and fourteen of its methyl, ethyl, dimethyl and trimethyl derivatives were observed as a function of molar concentration c at 20 °C and as a function of temperature from 20 to -70 °C. All the compounds show similar excimer fluorescence characteristics with mean values of the excimer binding energy B = 0.28 ± 0.03 eV and of the excimer interaction energy V' m = 0.765 ± 0.03 eV, with the exception of 1,8-dimethyl naphthalene (B = 0.14 eV) in which excimer formation is sterically hindered. The monomer fluorescence quantum efficiencies and ionization potentials were also determined. The fluorescence spectra of liquid 1,6-dimethyl naphthalene and its solutions in three solvents were observed, and the rate parameters and the entropy change ∆ S on excimer formation were determined, B and ∆ S (= -19.1 cal mole -1 deg -1 ) have similar values in the pure liquid and in cis -decalin and dilute ( c ≤ 1 m) cyclohexane solutions, but slight differences occur in n -heptane and concentrated (c > 1 m ) cyclohexane solutions.

‘Excimer’ fluorescence - X. Spectral studies of 9-methyl and 9, 10-dimethyl anthracene

1966 ◽  
Vol 291 (1427) ◽  
pp. 570-582 ◽  
Keyword(s):  
Transition Probabilities ◽  
Entropy Change ◽  
Radiative Transition ◽  
Fluorescence Yield ◽  
Concentration Quenching ◽  
Spectral Studies ◽  
Quantum Yields ◽  
Excimer Fluorescence ◽  
Excimer Formation ◽  
Monomer Fluorescence

The monomer and excimer fluorescence spectra and quantum yields of solutions of 9-methyl anthracene and 9-10-dimethyl anthracene in several solvents were observed as a function of concentration and temperature ( T ). The monomer and excimer fluorescence quantum efficiencies, the molar excimer/monomer fluorescence yield K , and the Stern–Volmer concentration quenching parameter K' , were determined at room temperature. K was observed as a function of T , and the excimer binding energy B evaluated. At high T, K for a given solute is independent of the solvent, indicating that B , ∆ S , the entropy change on excimer formation, and ( k fD ) 0 /( k fM ) 0 , the ratio of the excimer and monomer radiative transition probabilities in vacuo , are solvent-independent molecular properties. It is proposed that the excimer structure of any compound is similar to that of two adjacent molecules in the crystal lattice, with a reduced intermolecular spacing, and that the excimer fluorescence polarization is that of the 1 L a — 1 A monomer fluorescence. This model accounts for the different types of photodimerization behaviour in the meso -substituted anthracenes. It is proposed that all concentration quenching in aromatic hydrocarbons is due to the formation of excimers and/or stable photodimers.

‘Excimer’ fluorescence I. Solution spectra of 1:2-benzanthracene derivatives

1963 ◽  
Vol 274 (1359) ◽  
pp. 552-564 ◽  
Keyword(s):  
Quantum Yield ◽  
Crystal Lattice ◽  
Excited States ◽  
Concentration Dependence ◽  
Fluorescence Spectra ◽  
Excimer Fluorescence ◽  
Relative Quantum Yield ◽  
Relative Quantum ◽  
Different Types ◽  
Excimer Formation

Observations have been made of the concentration dependence of the fluorescence spectra of solutions of 1:2-benzanthracene and fifteen of its hydrocarbon derivatives. All of the compounds, except the 9,10-dim ethyl derivative, exhibit dim er emission at higher concentrations. The lower excited states, 1 L b and 1 L a , satisfy Förster’s conditions for fluorescent dim er formation. The factors determining the relative quantum yield of excimer fluorescence are discussed. The different types of crystal fluorescence spectra shown by the compounds are explained in terms of excimer formation in the crystal lattice.

'Excimer’ fluorescence VI. Benzene, toluene, p -xylene and mesitylene

1965 ◽  
Vol 283 (1392) ◽  
pp. 83-99 ◽  
Keyword(s):  
Binding Energy ◽  
Steric Hindrance ◽  
Fluorescence Spectra ◽  
Potential Model ◽  
Excimer Fluorescence ◽  
Benzene Toluene ◽  
Methyl Derivatives ◽  
Excimer Formation ◽  
Excitation Conditions

Observations were made of the fluorescence spectra of cyclohexane and n -hexane solutions of benzene, toluene, p -xylene and mesitylene and of the pure liquids as a function of concentration and temperature under standard excitation conditions. Excimer fluorescence is observed in benzene, toluene and mesitylene, and there is evidence for excimer formation in p -xylene. The data are analysed to determine the fluorescence quantum efficiencies, the rate parameters and other properties of the monomer-excimer systems. The following values are obtained for the excimer binding energy B ; benzene, 0.22 eV; toluene, 0.17 eV; p -xylene, > 0.11 eV; and mesitylene, 0.12 eV. The results are consistent with the excimer potential model, and the reduction in B in the methyl derivatives is attributed to steric hindrance.

Intramolecular excimer fluorescence from folded ground state rotamers of N,N'dimethyl-N,N'-dipyrenylurea protophanes

2003 ◽  
Vol 81 (6) ◽  
pp. 770-776 ◽  
Author(s):  
Frederick D Lewis ◽  
Todd L Kurth
Keyword(s):  
Ground State ◽  
Fluorescence Spectra ◽  
Fluid Solution ◽  
Absorption And Fluorescence Spectra ◽  
Model Compounds ◽  
Excimer Fluorescence ◽  
Decay Times ◽  
Intramolecular Excimer ◽  
Rotational Equilibrium ◽  
Monomer Fluorescence

The molecular structure, absorption, and fluorescence spectra of N,N'-dimethyl-N,N'-di-1-pyrenylurea and N,N'-dimethyl-N,N'-di-2-pyrenylurea have been investigated and compared to the properties of N,N,N'-trimethyl-N'-pyrenylurea model compounds. Di-1-pyrenylurea exists as a mixture of folded (E,E) syn- and anti-rotamers that interconvert via flipping of one of the pyrene rings to an unfolded (E,Z) rotamer geometry. The symmetric di-2-pyrenylurea exists as a single folded (E,E) conformation which is in equilibrium with a less-stable, unfolded (E,Z) rotamer. The absorption and fluorescence spectra of the dipyrenylureas at 77 K in a rigid glass are similar to those of monopyrenylurea model compounds. However, in fluid solution, the dipyrenylureas exhibit excimer fluorescence and very weak monomer fluorescence which have identical decay times. This behavior is attributed to fast rotational equilibrium between folded rotamers which exhibit excimer fluorescence and unfolded rotamers which exhibit monomer fluorescence. The behavior of the dipyrenylureas is compared with that of other systems that form intramolecular pyrene excimers and diarylureas.Key words: excited state rotamers, dipyrenylureas, pyrene excimers, ureaphane.

'Excimer’ fluorescence III. Lifetime studies of 1:2-benzanthracene derivatives in solution

1964 ◽  
Vol 277 (1369) ◽  
pp. 270-278 ◽  
Keyword(s):  
Light Source ◽  
Fluorescence Yield ◽  
Response Functions ◽  
Fluorescence Lifetimes ◽  
Concentrated Solutions ◽  
Excimer Fluorescence ◽  
Methyl Derivatives ◽  
Excimer Formation ◽  
Lifetime Studies ◽  
Monomer Fluorescence

Observations were made of the fluorescence lifetimes of 1:2-benzanthracene and fourteen of its methyl derivatives in dilute deoxygenated cyclohexane solutions. 1:2-benzanthracene and its 5-, 6- and 10-methyl derivatives were also studied in more concentrated solutions. The time response functions of the monomer and excimer fluorescence components were measured by two independent methods, namely the phase and modulation fluorometer and the pulsed light source techniques. The quantum efficiency of the monomer fluorescence in dilute solutions, and the relative excimer/monomer fluorescence yield I D I M in concentrated solutions, were also observed. The results are analyzed to determine the rate parameters of monomer and excimer fluorescence and of excimer formation and dissociation. It is found that only about half the collisions between excited and unexcited monomers result in excimer formation. This behaviour differs from that of pyrene and it is indicative of weaker excimer interaction in the 1:2-benzanthracene derivatives. The factors determining I D I M are discussed.

‘Excimer’ fluorescence V. Influence of solvent viscosity and temperature

1964 ◽  
Vol 280 (1381) ◽  
pp. 289-297 ◽  
Keyword(s):  
Transition Probability ◽  
Radiative Transition ◽  
Quantum Yields ◽  
Excimer Fluorescence ◽  
Diffusion Controlled ◽  
Relative Quantum ◽  
Fluorescence Characteristics ◽  
Steric Configuration ◽  
Monomer Fluorescence ◽  
Influence Of Solvent

The fluorescence characteristics of pyrene solutions in seven different solvents were studied at temperatures from – 100 to 90 °C. Observations were made of the relative quantum yields of excimer and monomer fluorescence and of the fluorescence spectra and time characteristics. The data, which were analyzed to determine the rate parameters and their associated activation energies, are consistent with an excimer formation process which is diffusion-controlled and reversible. The pyrene excimer binding energy B = 0·40 (± 0·01) eV and its radiative transition probability k f D = 1·2 x 10 7 s -1 are independent of the solvent and of the temperature. This indicates that the excimer has a stable steric configuration.

'Excimer’ fluorescence. IV. Solution spectra of polycyclic hydrocarbons

1964 ◽  
Vol 277 (1371) ◽  
pp. 571-582 ◽  
Keyword(s):  
Molecular Structure ◽  
Potential Energy ◽  
Steric Hindrance ◽  
Fluorescence Spectra ◽  
Energy Levels ◽  
Ground States ◽  
Polycyclic Hydrocarbons ◽  
Excimer Fluorescence ◽  
Chemical Combination ◽  
Excimer Formation

The fluorescence spectra of solutions of the following compounds which show excimer fluorescence are recorded: 5-ethyl, 5-butyl, 5-propyl, 5-amyl and 6-isopropyl 1:2-benzanthracene; 1:2:3:4-dibenzanthracene, perylene, 1:12-benzperylene and anthanthrene; and 2,5-diphenyloxazole. The spectra of these and other compounds showing excimer fluorescence are analyzed and discussed in terms of the potential energy of the dimer in its excited and ground states. A consideration of the molecular structure and energy levels of further compounds which do not show excimer fluorescence in solution indicates various factors which may inhibit excimer formation, namely (i) chemical combination, (ii) steric hindrance, and (iii) weakness of interaction.

How switching the substituent of a pyrene derivative from a methyl to a butyl affects the fluorescence response of polystyrene randomly labeled with pyrene

2010 ◽  
Vol 88 (3) ◽  
pp. 217-227 ◽  
Author(s):  
Mark Ingratta ◽  
Manoj Mathew ◽  
Jean Duhamel
Keyword(s):  
Organic Solvents ◽  
Excellent Agreement ◽  
Fluorescence Spectra ◽  
Series Solutions ◽  
Specific Nature ◽  
Polymer Backbone ◽  
Excimer Fluorescence ◽  
Fluorescence Response ◽  
Different Types ◽  
Blob Model

A series of polystyrenes randomly labeled with 1-pyrenebutanol were prepared by copolymerizing styrene and 1-pyrenebutylacrylate yielding the CoBuE–PS series. Solutions of CoBuE–PS were prepared in nine organic solvents having viscosities ranging from 0.36 to 5.5 mPa·s and the fluorescence spectra and pyrene monomer and excimer fluorescence decays were acquired. Analysis of the fluorescence spectra yielded the IE/IM ratio, whereas analysis of the fluorescence decays with the fluorescence blob model (FBM) yielded the parameters N blobo , <kblob × Nblob> , and k blobo . These parameters were compared to those obtained with two other series of pyrene-labeled polystyrenes, which had been studied earlier, namely CoA–PS and CoE–PS where pyrene was attached to the polymer backbone via a methylamide and benzyl methylether linker, respectively. Although the parameters IE/IM, N blobo , <kblob × Nblob>, and k blobo took different values according to the specific nature of the linker connecting pyrene to the polystyrene backbone, they exhibited trends that were quite similar for all the pyrene-labeled polystyrene constructs. The excellent agreement between the parameters retrieved for the three different types of pyrene-labeled polystyrenes suggests that the FBM accounts satisfyingly for differences in the nature of the label used, while still retrieving information pertinent to the polymer of interest.

scholarly journals Unfolding of Helical Poly(L-Glutamic Acid) in N,N-Dimethylformamide Probed by Pyrene Excimer Fluorescence (PEF)

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1690
Author(s):  
Weize Yuan ◽  
Remi Casier ◽  
Jean Duhamel
Keyword(s):  
Glutamic Acid ◽  
Local Density ◽  
Guanidine Hydrochloride ◽  
Racemic Mixture ◽  
Excimer Fluorescence ◽  
Excimer Formation ◽  
Blob Model ◽  
Α Helix ◽  
The Relationship ◽  
Pyrene Excimer Formation

The denaturation undergone by α–helical poly(L-glutamic acid) (PLGA) in N,N-dimethylformamide upon addition of guanidine hydrochloride (GdHCl) was characterized by comparing the fluorescence of a series of PLGA constructs randomly labeled with the dye pyrene (Py-PLGA) to that of a series of Py-PDLGA samples prepared from a racemic mixture of D,L-glutamic acid. The process of pyrene excimer formation (PEF) was taken advantage of to probe changes in the conformation of α–helical Py-PLGA. Fluorescence Blob Model (FBM) analysis of the fluorescence decays of the Py-PLGA and Py-PDLGA constructs yielded the average number (<Nblob>) of glutamic acids located inside a blob, which represented the volume probed by an excited pyrenyl label. <Nblob> remained constant for randomly coiled Py-PDLGA but decreased from ~20 to ~10 glutamic acids for the Py-PLGA samples as GdHCl was added to the solution. The decrease in <Nblob> reflected the decrease in the local density of PLGA as the α–helix unraveled in solution. The changes in <Nblob> with GdHCl concentration was used to determine the change in Gibbs energy required to denature the PLGA α–helix in DMF. The relationship between <Nblob> and the local density of macromolecules can now be applied to characterize the conformation of macromolecules in solution.

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