http://www.columbia.edu/~ps24/PDFs/Fluorescence%20Probe%20Studies%20on%20the%20Structure%20...%20Alumina%20Wate.pdf

Fluorescence probe studies on the structure of the adsorbed layer of dodecyl sulfate at the alumina—water interface

Inclusion compounds in the systems naphthalene–β-cyclodextrin (CDx) and 2-methoxynaphthalene (MN)–o-dicyanobenzene (DB)–β-cyclodextrin in aqueous solution were studied by means of absorption and fluorescence spectra. In the former system a naphthalene excimer fluorescence was observed. By the analyses of the concentration dependence of the absorption spectra and the excimer fluorescence intensities, the species responsible for the excimer fluorescence is identified as a 2:2 inclusion compound which is formed by association of two 1:1 naphthalene–CDx inclusion compounds, not a 2:1 inclusion compound in which two naphthalene molecules enter into the cavity of one CDx molecule. In the latter system, absorption and fluorescence spectra due to a charge transfer complex of MN with DB were observed. By analyses similar to the naphthalene case, the existence of a 1:1:2 association compound formed between a MN–CDx inclusion compound and a DB–CDx inclusion compound is confirmed. Fluorescence quenching by I− and IO3...

Association of Inclusion Compounds of β-Cyclodextrin in Aqueous Solution

The emission properties of poly(N‐vinylcarbazole) (PVK), poly(N‐ethyl‐2‐vinylcarbazole), and poly(N‐ethyl‐3‐vinylcarbazole) have been investigated. Dilute fluid solutions of all three vinylcarbazole polymers are observed to exhibit a structureless emission band at energies approximately 5400 cm−1 to the red of the (0,0) band of the normal molecular fluorescence of isolated monomer compounds. On the basis of earlier work appropriate model compounds, this emission is assigned as that from an intrachain excimer state in which two interacting pendant groups, one of which is electronically excited, achieve an overlapping, eclipsed, sandwichlike configuration. The emission spectrum of PVK is characterized by the appearance of a second structureless emission band which appears at higher energy than the intrachain excimer fluorescence common to all three vinylcarbazole polymers. This emission band is unique to PVK and under certain conditions to its model compound, 1,3‐bis(N‐carbazolyl)propane. This emission is assigned as that from a second intrachain excimer. Contrary to the lower energy intrachain excimer, the polymer conformation appropriate for formation of this state exists prior to the initial excitation step.

Emission properties of vinylcarbazole polymers

Tetracyanoethylene and enol ethers. A model for 2 + 2 cycloadditions via zwitterionic intermediates

Ion pairing and premicellar association have been often invoked to explain results obtained in studies of aqueous solutions of ionic dimeric surfactants (gemini surfactants), mainly by means of surface tension and electrical conductivity, at concentrations below the critical micellization concentration (cmc). The present work was undertaken in an attempt to find out under which conditions these effects come into play. For this purpose the electrical conductivity of solutions of many dimeric surfactants of the type spacer-α,ω-bis(alkyldimethylammonium bromide) have been measured. The alkyl chain contained m=10–18 carbon atoms. The spacer group was either an alkanediyl with s carbon atoms (m-s-m surfactants) or a xylylene m-xylyl-m surfactants). The results show that ion pairing occurs in solutions of m-s-m dimers with m≤10, mostly as a result of their high cmc values. The results for 12-s-12 dimers with s≤10 and for 12-xylyl-12 showed no evidence of either ion pairing or premicellar association. Premicellar association was present for 12-s-12 dimers with s≥12, for m-8-m dimers with m≥14, and for 16-xylyl-16. It showed through a positive curvature of the specific conductivity versus concentration plot and the presence of a maximum in the equivalent conductivity vs (concentration)0.5 plot at concentrations below the cmc. The free energy associated with the premicellar association of m-8-m dimers has been estimated from the available cmc and micelle ionization degree data.

Alkanediyl-α,ω-Bis(dimethylalkylammonium Bromide) Surfactants

Intramolecular excimer formation and fluorescence quenching in dinaphthylalkanes

Excimer fluorescence and dimer phosphorescence from a naphthalene sandwich pair

Reversible intramolecular photodimerization of 1,3-bis(.alpha.-naphthyl)propane

Cycloaddition. X. Reversibility in the biradical mechanism of cycloaddition. Tetrafluoroethylene and 1,1-dichloro-2,2-difluoroethylene with 2,4-hexadiene

Carol J. Dempster

Papers

Intramolecular excimer formation and fluorescence quenching in dinaphthylalkanes

Excimer fluorescence and dimer phosphorescence from a naphthalene sandwich pair

Reversible intramolecular photodimerization of 1,3-bis(.alpha.-naphthyl)propane

Cycloaddition. X. Reversibility in the biradical mechanism of cycloaddition. Tetrafluoroethylene and 1,1-dichloro-2,2-difluoroethylene with 2,4-hexadiene

Intramolekulare excimeren-bldg. und fluoreszenzloeschung in dinaphthylalkanen