A. Pardo

Solvent dependence of the inhibition of intramolecular charge-transfer in N-substituted 1,8-naphthalimide derivatives as dye lasers

Abstract Fluorescence, lasing efficiency and photostability of the 4-methoxy and 4-acetamide-N-substituted 1,8-naphthalimide derivatives in alcohols have been investigated. An intramolecular charge-transfer (CT) inhibits the fluorescence and laser emission in the derivatives with an amino terminal group in the side chain. The addition of protons (acetic acid) quenches the intramolecular CT, and a high lasing efficiency in the green-blue zone of the spectrum is obtained with a N 2 pulsed laser ( FWHM ∼- 5.5 ns). The results have been interpreted on the basis of the acidity, polarity and viscosity of the solvents. Photostability tests with a pulsed N 2 laser and a Xe lamp (150 W) show good behavior for all molecules, except in ethylene glycol.

Some β-carboline derivatives as fluorescence standards

Abstract We present in this work a study on the standard properties of five β-carboline derivatives: nor-harmane or β-carboline, harmane, harmine, 2-methyl harmine and harmaline in H2SO4 aqueous solutions. The cationic species absorb and emit in these media, therefore, we have measured the fluorescence quantum yield and lifetime values of cationic species. Fluorescence spectra of these five cationic species cover a region between 400–560 nm. These five spectra show a strong overlapping.

Synthesis and photophysical properties of some N-substituted-1,8-naphthalimides

Abstract The synthesis and photophysical properties of some 3-amino-N-substituted-1,8-naphthalimide derivatives are presented. The flourescence behaviour of these compounds in protic and aprotic solutions is consistent with the formation of an exciplex structure. The exciplex formation is due to a proton transfer in the excited state. This exciplex formation eliminates non-radiative channels and therefore an increase in quantum yield is observed.

Photophysical properties of 1,8-naphthalimide derivatives

Abstract A study of the photophysical properties of the derivatives of 1,8-naphthalimide is presented. The absorption and fluorescence spectra in protic and aprotic media are consistent with the assumption of exciplex formation. The application of the technique of single-photon counting was of great importance for the lifetime measurements. The exciplex formation is interpreted as resulting from proton migration.

Solvent effects on the photophysical properties of N-substituted 1,8-naphthalimide derivatives

Abstract The photophysical properties of two N -substituted 1,8-naphthalimide derivatives were studied in various solvents (dichloromethane, benzene, dimethyl sulphoxide and water). The variations in the fluorescence spectra, absorption spectra, quantum yield and fluorescence lifetime were analysed. The results obtained are slightly different from the conclusions of previous investigations.

PMO-RKR-van der Waals potential energy curves for the X1Σ+ and A1Σ+ states of the isotopic lithium hydrides

Abstract The potential energy curves for the X 1 Σ + and A 1 Σ + states of lithium hydrides and deuterides have been calculated by a new procedure which uses: (a) a perturbed Morse oscillator for the minimum zone; (b) a Rydberg-Klein-Rees potential for the zone of energy levels which can be represented from the experimental data; (c) a van-der Waals-type potential for the asymptotic part of the potential. All the calculated potentials have been checked by solving numerically the radial Schrodinger equation. From the wavefunctions generated we have obtained the vibrational energy eigenvalues and B v values, observing a very good agreement with the experimental data.

N-substituted 1,8-naphthalimide derivatives as high efficiency laser dyes

Abstract A study of the photophysical properties of novel N -substituted 1,8-naphthalimide derivatives was performed in our laboratory. Some derivatives with a methoxy group in position 4 of the naphthalic ring have a high fluorescence quantum yield. The lasing efficiency of these compounds in acetonitrile solution, using an N 2 laser as the pumping system, is reported.

Quantum yield and fluorescence lifetime measurements of neutral and cationic species for six β-carboline derivatives

Abstract A study of some emission parameters (quantum yield and fluorescence lifetime) for six alkaloid derivatives of β-carboline is presented. Depending on pH value, various species can exist in solution. In this work we have studied only two of them: cationic and neutral species (see fig. 1). The variation of quantum yield and fluorescence lifetime has been analysed for different substituted β-carboline rings and for some derivatives which do not present the aromatic character on the pyrimidinic nucleus.

Double exponential fluorescence decay in the protonation equilibrium of 4-methoxy-N-[2-(1-pyrrolidin)ethyl]-1,8-naphthalimide]

Abstract Fluorescence decay of 4-methoxy-N-[2-(1-pyrrolidin)ethyl]-1,8-naphthalimide] in water solution is analyzed. At pH values around 10, a double exponential decay function is observed. When pH > 10 or pH

A study of the B1Πu → X1Σ+g system of Na2

We report here an analysis of the B1Πu → X1Σ+g band system of the sodium dimer. The body of data includes laser-induced emission of Na2 consisting of discrete molecular fluorescence (107 fluorescence series) excited by visible lines from an argon ion laser and rotational relaxation lines for strong transitions. In order to enlarge the data set of transitions within this band system, which cover both X1Σ+g and B1Πu states up to dissociation, the results were combined with spectroscopic experimental data available in the literature. The obtained Dunham coefficients were used to derive the corresponding molecular potentials using basically the RKR method. Hybrid potential energy curves for the X1Σ+g and B1Πu states have been checked by solving numerically the radial Schrodinger equation observing a good agreement with the experimental data.