Inter- and Intramolecular Interactions of Polymers as Studied by Fluorescence Spectroscopy. II. Excimer Formation of Polyesters Having Pendant 1-Naphthylmethyl Groups

1976 ◽  
Vol 9 (3) ◽  
pp. 451-455 ◽  
Author(s):  
Shigeo Tazuke ◽  
Fumio Banba
Keyword(s):  
Fluorescence Spectroscopy ◽  
Intramolecular Interactions ◽  
Excimer Formation

Excimer Formation in Oligo[2,5-bis(hexadecyloxy)-1,4-phenylene]s Followed by Fluorescence Spectroscopy

2001 ◽  
Vol 66 (10) ◽  
pp. 1473-1489 ◽  
Author(s):  
Drahomír Výprachtický ◽  
Věra Cimrová ◽  
Luďka Machová ◽  
Veronika Pokorná
Keyword(s):  
Fluorescence Spectroscopy ◽  
Hydrophobic Interactions ◽  
Group Analysis ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Coupling Reaction ◽  
Fluorescence Emission Spectra ◽  
Time Resolved ◽  
Sandwich Type ◽  
Excimer Formation

Using the steady-state and time-resolved fluorescence spectroscopy, the behavior of "hairy-rod" oligo- and poly[2,5-bis(hexadecyloxy)-1,4-phenylene]s in tetrahydrofuran solutions was investigated. The materials were prepared by the Yamamoto coupling reaction using zinc as a reducing metal, the nickel(II)/triphenylphosphine complex as a catalyst, and 2,2'-bipyridine as a coligand. The appropriate oligomer fractions were separated by fractional precipitation and characterized by GPC and end group analysis. The fluorescence quantum yield of oligomers and polymers increased with their increasing conjugation length. The fluorescence emission spectra of polymers and longer oligomers exhibited one emission maximum at 390 nm with a single-exponential decay and fluorescence lifetimes (τ) around 1 ns. The substitution in positions 2 and 5 forces the adjacent backbone benzene units out of the plane, which results in twist angles 60-80°, and the bulky substituents exclude the cofacial sandwich-type configuration necessary for excimer formation. However, with shorter oligomers, another emission band at 460 nm appeared. Fluorescence decays at 460 nm were found to be double-exponential with longer excited-state lifetimes [e.g. τ1 = 6.9 ns (76%), τ2 = 2.4 ns (24%)]. With shorter oligomers (dimer, trimer), we assume a sandwich-type configuration with sufficiently close interchain distance and hence the excimer can form. Hydrophobic interactions of long aliphatic side chains in a polar medium play an important role in the excimer formation.

Studies of Temperature-Dependent Excimer-Monomer Conversion in Dendrimeric Antenna Supermolecules by Fluorescence Spectroscopy

2000 ◽  
Vol 651 ◽  
Author(s):  
Youfu Caoa ◽  
Jeffrey S. Moore ◽  
Raoul Kopelman
Keyword(s):  
Fluorescence Spectroscopy ◽  
Organic Solvents ◽  
Equilibrium Constants ◽  
Emission Spectra ◽  
Monomer Conversion ◽  
Temperature Dependent ◽  
Dissociation Dynamics ◽  
Potential Applications ◽  
Different Temperatures ◽  
Excimer Formation

AbstractPhenylacetylene (PA) dendrimer labeled with perylene (See Fig 1) is discovered to exhibit temperature-dependent emission spectra in certain organic solvents over the temperature range of 20-65°C. The monomer signal is increasing rapidly when temperature increases, while the excimer signal decreases slowly. Models of excimer formation and weakly associated pairs (M+M) dissociation dynamics are included, and the equilibrium constants at different temperatures are calculated. This behavior suggests potential applications in fluorescence-based thermometry.

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