<title>Electro-optical and fluorescence lifetime studies of aminophthalimide probes in liquids</title>

The modified electro-optical absorption and emission methods are described as well as their use for measurements of electrical dipole moments of five aminophthalimides in ground and excited states. It is found that there exists a principal difference between properties of 3- aminophthalimide (3AP) and 4-amino-N-methylphthalimide (4ANMP) in different solvents. The equilibrated dipole moment of 3AP in its excited state is practically independent on the solvent polarity, in comparison with 4ANMP. The possible mechanism of this effect is discussed.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Spectral and electrooptical absorption and emission studies on internally hydrogen bonded benzoxazole `double' derivatives: 2,5-bis(benzoxazolyl)hydroquinone (BBHQ) and 3,6-bis(benzoxazolyl)pyrocatechol (BBPC). Single versus double proton transfer in the excited BBPC revisited

Abstract Ground and excited state dipole moments and polarizabilities of 2,5-bis(benzoxazolyl)hydroquinone (BBHQ) and 3,6-bis(benzoxazolyl)pyrocatechol (BBPC) are determined by means of electrooptical absorption and emission measurements. BBHQ is found to exhibit a small, while BBPC a large increase of the static polarizability in the Franck–Condon (FC) excited singlet state. The change of the dipole moments upon excitation to the FC state is zero within experimental error. However, both molecules show dipole moments in the fluorescent states of their phototautomers, of about 5 D, the major component being parallel to the long molecular axis. The experimental and theoretical results strongl…

<title>Coumarin fluorescent probes by electro-optical and laser spectrofluorimetry methods</title>

Modified electro-optical absorption and emission methods were used to measure the dipole moments of six coumarin fluorescent probes (CU1, CU4, CU7, CU30, CU120, CU334) in the equilibrated ground, excited Franck-Condon and equilibrated excited states. The measurements were performed in cyclohexane and dioxane at room temperature. The equilibrated ground and excited states dipole measured by electro-optical methods are compared with those derived from other measurements techniques and from semiempirical calculations. Experiments and calculations performed in this work reveal a set of anomalous and interesting properties of CU7 and CU30 in solutions. The spectral dependence of some electro-opt…

Intramolecular Charge Transfer as Revealed by Results from the Measurement of Ground and Excited State Dipole Moments

Dipole moments of aminophthalimides determined by modified electro-optical absorption and emission measurements

Modified electro-optical absorption and emission methods were used to measure the electric dipole moments of five aminophthalimides in their ground and excited states. The equilibrated ground and excited state dipole moments measured by these methods are in reasonable agreement with those derived from other measurement techniques, confirming the general validity of these methods. A difference is observed between the properties of 3-aminophthalimide (3AP) and 4-amino-N-methylphthalimide (4ANMP) in different solvents. The equilibrated dipole moment of 3AP in its excited state is practically independent of the solvent polarity in contrast with 4ANMP. The possible mechanism of this effect is di…

Influence of rotational diffusion on the electric field induced effect on the fluorescence spectrum of diluted solutions I. Theory and numerical simulations

Abstract The theory for the calculation of excited state dipole moments from electrooptical emission measurements, developed by Baumann and Deckers (Ber. Bunsenges. Phys. Chem. 81 (1977) 786) presupposes a Boltzmann distribution for the emitting molecules. Using the anisotropic rotational diffusion model and taking into account all important electric field induced effects, we derive equations that describe quantitatively the electric field effect on the fluorescence of an ensemble of solute rigid molecules which are not yet equilibrated with respect to their orientation when emitting. Numerical simulations are performed to compare the general case and the limiting case of a prevailing Boltz…

Electro-optical and laser spectrofluorimetry study of coumarins 7 and 30: evidence for the existence of the close-lying electronic states and conformers

Our experiments and calculations reveal a set of anomalous and interesting properties of coumarin 7 (CU7) and coumarin 30 (CU30) in solution. The spectral dependence of electro-optical coefficients and, consequently, dipole moments indicates that the absorption band is a superposition of several (at least two) electronic transitions. Probably, there are two close-lying π,π* singlet electronic excited states which contribute to the first absorption band. The calculations using the MM2 program show that both dyes in the ground state have two stable plane anti conformers. From time-resolved spectrofluorimetric measurements we obtained evidence for the existence of conformers in paraffin oil so…

Use of the red-edge excitation effect for investigation of dielectric interactions in biomembranes

Dipole moments of the fluorescent probes 1-phenylnaphthylamine (1-AN) and 1-anilinonaphthalene-8-sulfonate (1,8-ANS) are measured using electro-optical absorption and emission methods. Dipole moments in the ground and excited states were measured in cyclohexane and dioxane. It is shown that the charge distributions in the 1-AN and 1,8-ANS molecules differ substantially. The spectral dependence of the electro-optical coefficients suggests that the absorption spectrum of 1,8-ANS is due to a superposition of (at least two) electronic transitions. It is found that spectra of 1-AN in erythocyte ghosts are inhomogeneously broadened. The above effect makes it possible to selectively excite probe m…

Linear and nonlinear optical properties of some organoxenon derivatives

We employ a series of state-of-the-art computational techniques to study the effect of inserting one or more Xe atoms in HC2H and HC4H, on the linear and nonlinear optical (L&NLO) properties of the resulting compounds. It has been found that the inserted Xe has a great effect on the L&NLO properties of the organoxenon derivatives. We analyze the bonding in HXeC2H, and the change of the electronic structure, which is induced by inserting Xe, in order to rationalize the observed extraordinary L&NLO properties. The derivatives, which are of interest in this work, have been synthesized in a Xe matrix. Thus the effect of the local field (LF), due to the Xe environment, on the properties of HXeC2…

Ground and excited state dipole moments of coumarin laser dyes: Investigation by electro-optical absorption and emission methods

Abstract Modified electro-optical absorption and emission methods were used to measure the dipole moments of four efficient coumarin laser dyes (CU1, CU4, CU120, CU334) in the equilibrated ground, excited Franck-Condon and equilibrated excited states. The measurements were performed in cyclohexane (CU1, CU120, CU334) and dioxane (all CUs) at room temperature. Our results show that the charge distribution in CU4 differs substantially from that in the other CUs. The equilibrated ground and excited state dipole moments measured by electro-optical methods are compared with those derived from other measurement techniques and from semiempirical calculations. The possible role of twisted intermole…

Dipole moments of aminophthalimides in the ground and excited electronic states

Effect of Lung Recruitment and Titrated Positive End-Expiratory Pressure (PEEP) vs Low PEEP on Mortality in Patients With Acute Respiratory Distress Syndrome : a Randomized Clinical Trial

Importance The effects of recruitment maneuvers and positive end-expiratory pressure (PEEP) titration on clinical outcomes in patients with acute respiratory distress syndrome (ARDS) remain uncertain. Objective To determine if lung recruitment associated with PEEP titration according to the best respiratory-system compliance decreases 28-day mortality of patients with moderate to severe ARDS compared with a conventional low-PEEP strategy. Design, Setting, and Participants Multicenter, randomized trial conducted at 120 intensive care units (ICUs) from 9 countries from November 17, 2011, through April 25, 2017, enrolling adults with moderate to severe ARDS. Interventions An experimental strat…