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In this work, a comprehensive investigation of the salicylideneaniline derivatives is carried out using density functional theory to determine their linear and nonlinear optical (NLO) properties. Geometry optimizations, for gas and solvent phases, of the tautomers (enol and keto forms) are calculated using B3LYP levels with 6-31G(d,p) basis set. An intramolecular proton transfer, for 1SA-E and 2SA-E, is performed by a PES scan process at the B3LYP/6-31G(d,p) level. The optical properties are determined and show that they have extremely high NLO properties. In addition, the RDG analysis, molecular electrostatic potential (MEP), and gap energy are calculated. The low energy gap value indicates the possibility of intramolecular charge transfer. The frontier molecular orbital calculations clearly show the inverse relationship of HOMO-LUMO gap with the first-order hyperpolarizability ([beta] = 59.6471 * [10.sup.-30] esu), confirming that the salicylideneaniline derivatives can be used as attractive future NLO materials. Therefore, the reactive sites are predicted using MEP and the visible absorption maxima are analyzed using a theoretical UV-Vis spectrum. Natural bond orbitals are used to investigate the stability, charge delocalization, and intramolecular hydrogen bond. Key words: first hyper polarizability, HOMO-LUMO energy gap, NLO properties, UV-Vis spectrum, tautomers. Nous completons ici une investigation des derives de salicylideneaniline en utilisant la theorie de la fonctionnelle de densite, afin de determiner leurs proprietes optiques lineaires et non lineaires. Nous calculons l'optimisation geometrique des tautomeres (dans les formes eno (eno) et ceto (keto)), pour les phases gazeuse et solute, en utilisant les niveaux B3YLP et l'ensemble de base 6-31G(d,p). Un transfert intramoleculaire, pour 1SA-E et 2SA-E, est verifie par balayage de l'energie potentielle de surface (EPS/PES) au niveau B3LYP/6-3G(d,p). Nous determinons les proprietes optiques des echantillons et montrons qu'elles sont extremement non lineaires. De plus, l'analyse du Gradient de Densite Reduite (GDR/RDG), le potentiel electrostatique moleculaire (PEM/MEP) et le gap d'energie sont aussi evalues. La faible valeur du gap d'energie indique la possibilite d'un transfert de charge intramoleculaire. Le calcul de l'orbitale moleculaire frontiere montre clairement l'inversion du gap HOMO-LUMO avec une hyperpolarisabilite ([beta] = 59.6471 * [10.sup.-30] esu), confirmant que les derives de salicylideneaniline peuvent etre utilises comme d'interessants materiaux en optique non lineaire (ONL/NLO). Par consequent, nous identifions les sites reactifs en utilisant le PEM et les maxima d'absorption dans le visible sont analyses via le spectre theorique UV-Vis. Les orbitales liees localisees (naturelles) sont utilisees pour analyser la stabilite, la delocalisation de charge et le lien hydrogene intramoleculaire. Mots-cles : premiere super polarisabilite, gap d'energie HOMO-LUMO, proprietes d'optique non lineaire, spectre UV-Vis, tautomeres., 1. Introduction Salicylideneaniline derivatives are of great interest due to the formation of O-H ... N (phenol-imine) and O ... H-N (keto-amine) type hydrogen bonds, which result in tautomerization between [...]

Boronic acid derivatives are novel biologically active fluorescent molecules with numerous applications in various fields. A study of their fluorescent properties reveals some information that can be utilized in sensor design. One such study is fluorescence quenching. Here fluorescence quenching of 2-methoxypyridin-3-yl-3- boronic acid (2MPBA) in different solvents of a wide range of polarities has been carried out at room temperature by steady state fluorescence measurements. Aniline is used as the quencher. The positive deviation observed in Stern-Volmer (S-V) plots is analyzed using different quenching models. Various quenching parameters like S-V constant ([K.sub.SV]), quenching rate parameter ([k.sub.q]), volume constant (V), and kinetic distance (r) have been estimated using extended S-V equations. [K.sub.SV] is found to vary from 12.94 to 62.49 [(mol/L).sup.-1] with respect to solvents. From the calculated values of these parameters it is concluded that the static quenching mechanism is active in the studied system. However the reactions are diffusion-limited, which is confirmed by invoking the finite sink approximation model. Key words: fluorescence quenching, static and dynamic quenching, sphere of action static quenching model, finite sink approximation model. Les derives de l'acide boronique sont de nouvelles molecules fluorescentes, biologiquement actives avec un grand nombre d'applications dans divers champs. Une etude de leurs proprietes de fluorescence donne de l'information qui peut etre utile dans la conception des senseurs. Une de ces etudes touche la desactivation de la fluorescence. A l'aide de mesures de fluorescence en etat stationnaire, nous etudions ici la desactivation de la fluorescence du 2-methoxypyridine-3-yl-3- acide boronique (2MPBA) dans differents solvants couvrant un large domaine de polarite a la temperature de la piece. Nous utilisons l'aniline comme milieu de desactivation. La deviation positive observee dans le graphique de Stern-Volmer (S-V) est analysee en utilisant differents modeles de desactivation. En utilisant les equations etendues de S-V, nous estimons differents parametres de desactivation, comme la constante [K.sub.SV] de S-V, le parametre de taux de desactivation [k.sub.q], le volume constant V et la distance cinetique r. Nous trouvons que [K.sub.SV] varie entre 12,94 et 62,49 [(mol/L).sup.-1], dependant du solvant. A partir de la valeur calculee de ces parametres, nous concluons que le mecanisme de desactivation statique est actif dans les systemes etudies. Cependant, les reactions sont limitees par la diffusion, ce qui est confirme en invoquant le modele de l'approximation du puits fini. [Traduit par la Redaction] Mots-cles: desactivation (extinction) de la fluorescence, desactivation statique et dynamique, modele de la sphere de desactivation statique, modele de l'approximation du puits fini., 1. Introduction Fluorescence quenching is a mechanism by which the fluorescence intensity of a given substance decreases. Because of many novel applications, fluorescence quenching study has attracted many investigators in [...]

Abstract: Corrosion protection of aluminum in 2 mol/L [H.sub.2]S[O.sub.4] solution is examined in the presence of ortho-substituted aniline derivatives using potentiodynamic polarization and electrochemical impedance spectroscopy measurements. Density function theory [...]

Quenching mechanisms of coumarin derivative 6-bromo-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarin (6BDTC) were carried out in different solvents using the steady-state method to understand the role of diffusion in the quenching mechanism. The solute was excited by UV radiation of wavelength 360 nm. Various quenching parameters like frequency of encounter, [k.sub.d]; probability of quenching per encounter, p; and quenching rate parameter, [k.sub.q], were experimentally determined for all solvents. Activation energies of quenching, [E.sub.a], were also determined by using the literature values of activation energy of diffusion, [E.sub.d]. It was found that the values of [E.sub.a] were less than [E.sub.d] in all solvents indicating that the quenching reactions are more significantly influenced by material diffusion. PACS Nos.: 33.50.-j, 87.64.i, 31.70.Hq, 87.15.kg. Resume : Nous avons utilise les mecanismes d'extinction (de luminescence) d'un derive de coumarine 6-bromo-3-[1- (4,5carbomethoy- 1,2,3-triazoloacetyl)]coumarine (6BTDC) dans differents solvants par la methode stationnaire, afin de comprendre le role de la diffusion dans le mecanisme d'extinction. Le solute a ete excite par radiation UV de 360 nm. Nous avons determine experimentalement divers parametres d'extinction pour tous les solvants, comme la frequence de collision ([k.sub.d]), la probabilite d'extinction par collision (p) et le parametre de taux d'extinction ([k.sub.q]). Nous avons aussi determine l'energie d'activation ([E.sub.a])en utilisant les valeurs dans la litterature pour l'energie d'activation de diffusion ([E.sub.d]). Nous avons trouve que les valeurs de [E.sub.a] sont moindres que celles de [E.sub.d] dans tous les solvants, ce qui indique que les reactions d'extinction sont significativement plus influencees par la diffusion. [Traduit par la Redaction], 1. Introduction The mechanism of decreasing the fluorescence intensity of a given substance is known as fluorescence quenching. The different types of quenching mechanisms are dynamic quenching, static quenching, and [...]

Quenching mechanisms of coumarin dyes, namely 6-bromo-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarin (6BDTC) and 8-methoxy-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarin (8MDTC), were carried out in toluene by adopting two methods, namely steady-state and time-resolved methods, to understand the role of diffusion in the quenching mechanism. The solute molecules were excited by UV radiation of wavelength 360 and 330 nm. Various quenching parameters like frequency of encounter ([k.sub.d]), probability of quenching per encounter (p and p=), and quenching rate parameter (kq and k'q) were experimentally determined in all the solvents. Activation energy of quenching ([E.sub.a] and [E.sub.a]) was also determined by using the literature values of activation energy of diffusion ([E.sub.d]). It was found that the values of [E.sub.a] (and [E.sub.a]) were less than [E.sub.d] indicating that the quenching reactions are more significantly influenced by diffusion. PACS Nos.: 33.50.D, 33.50.-j, 87.64.i, 31.70.Hq. A l'aide des methodes stationnaire et resolue dans le temps, afin de comprendre le role de la diffusion dans le mecanisme d'extinction (de luminescence), nous avons active dans le toluene les mecanismes d'extinction de colorants coumarine, nommement le 6-bromo-3-[1-(4,5-dicarbomethoxy-1,2,3-triazoloacetyl)]coumarine (6BDTC) et 8-methoxy-3-[1-(4,5- dicarbomethoxy-1,2,3triazoloacetyl)]coumarine (8MDTC). Les molecules de solute ont ete excitees par radiation UV de longueur d'onde 360 et 330 nm. Nous avons determine experimentalement, dans tous les solvants, differents parametres de desactivation, comme la frequence de collision ([k.sub.d]), la probabilite de desactivation par collision (p et p=) et le parametre de taux de desactivation (kq et kq). Utilisant les valeurs de la litterature pour l'energie d'activation de la diffusion ([E.sub.d]), nous avons determine les energies d'activation de desactivation ([E.sub.a] et [E.sub.a]). Nous trouvons que [E.sub.a] (et [E'.sub.a)] sont plus petites que [E.sub.d], ce qui indique que les reactions de desactivation sont significativement plus affectees par la diffusion. [Traduit par la Redaction], 1. Introduction The mechanism of decreasing the fluorescence intensity of a given substance is known as fluorescence quenching. The different types of quenching mechanisms are dynamic quenching, static quenching, and [...]

Binary mixtures of aniline with benzene, toluene, alkane, alkanol, or N,N-dialkylamide have been investigated in the framework of the DISQUAC model. The reported interaction parameters change regularly with the molecular structure of the mixture components. The model consistently describes a set of thermodynamic properties including liquid-liquid equilibria, vapor-liquid equilibria, and molar excess enthalpies. The two latter properties for ternary systems are well-represented by DISQUAC using binary parameters only (i.e., neglecting ternary interactions). A comparison of DISQUAC results and those obtained from the UNIFAC (Dortmund version) and ERAS models is also shown. The experimental molar excess enthalpies for binary and ternary mixtures are better described by DISQUAC than by UNIFAC. ERAS fails when representing molar excess enthalpies of those binary systems including methanol or ethanol. This may be due to the existence of strong dipolar interactions among aniline molecules as well as to effects related to the equation of state term, evaluated comparing molar excess enthalpies, and molar excess internal energies at constant volume. The study of the aniline systems in terms of the concentration-concentration structure factor also underlines the importance of dipolar interactions in solutions with alkanes or alcohols, which may be due to the high polarizability of the aniline molecule. Key words: thermodynamics, mixtures, aniline, dipolar interactions, structural effects. Etude de melanges binaires d'aniline en presence de benzene, de toluene, d'alcane, d'alcanol et de N,N-dialkylamide dans le contexte du modele DISQUAC. Les parametres d'interaction qui ont ete rapportes varient regulierement en fonction de la structure moleculaire des composes des melanges. Le modele decrit d'une facon consistante un ensemble de proprietes thermodynamiques, y compris les equilibres liquide-liquide, les equilibres vapeur-liquide et les enthalpies molaires en exces. Pour les systemes ternaires, ces deux dernieres proprietes sont bien representees par le modele DISQUAC en n'utilisant que des parametres binaires, c'est-a-dire en negligeant les interactions ternaires. On presente aussi une comparaison des resultats obtenus avec le modele DISQUAC et de ceux obtenus avec les modeles UNIFAC (version Dortmund) et ERAS. Les enthalpies molaires en exces des melanges binaires ou ternaires sont mieux representees par DISQUAC que par UNIFAC. Le modele ERAS n'arrive pas a representer les enthalpies molaires en exces de ces systemes binaires, y compris le methanol ou l'ethanol. Ce resultat peut etre du a l'existence de fortes interactions dipolaires entre les molecules d'aniline ainsi qu'aux effets relies aux termes de l'equation d'etat, qui est evalue en comparant les enthalpies molaires en exces, et les energies internes molaires en exces a volume constant. L'etude des systemes de l'aniline en termes de facteur de structure concentration-concentration met aussi en evidence l'importance des interactions dipolaires en solutions dans des alcanes ou des alcools qui peuvent etre dus a la grande polarisabilite de la molecule d'aniline. Mots cles : thermodynamique, melanges, aniline, interactions dipolaires, effets de structure. [Traduit par la Redaction], Introduction Amines are a very interesting class of compounds. Primary and secondary linear amines are weakly self-associated (1-5). Solutions of tertiary amines with aliphatic hydrocarbons, and particularly with homomorphic alkanes, […]

We have prepared the aryl sulfonamides 4,4'-R-[C.sub.6][H.sub.4]S[O.sub.2]NH[C.sub.6]] [H.sub.4]CH=C[H.sub.2] (R = C[H.sub.3], la; N[O.sub.2], 1b) by addition of 2 equiv, of 4-vinylaniline to the corresponding sulfonyl chlorides. The disulfonamides 4,4,4'-[(R-[C.sub.6][H.sub.4]S[O.sub.2]).sub.2] N[C.sub.6][H.sub.4]CH=C[H.sub.2] (R = C[H.sub.3], 2a; N[O.sub.2], 2b) were also prepared using 4-vinylaniline and 2 equiv, of the sulfonyl chlorides in the presence of DMAP. Although hydroborations of sulfanilamide derivatives 1 suffered from competing hydrogenation reactions, judicious choice of the transition metal catalyst gave selective formation of either the primary or secondary boronate esters in hydroborations of 2a. Key words: boronate esters, catalysed hydroborations, sulfanilamides, vinylaniline. On a prepare les aryl sulfonamides, 4,4'-R-[C.sub.6][H.sub.4]S[O.sub.2]NH[C.sub.6][H.sub.4]CH=C[H.sub.2] (R = C[H.sub.3], 1a; N[O.sub.2], 1b) par l'addition de deux equivalents de 4-vinylaniline aux chlorures de sulfonyle correspondants. On a aussi prepare les disulfonamides 4,4,4'-[(R-[C.sub.6][H.sub.4]S[O.sub.2])sub.2]N[C.sub.6] [H.sub.4]CH=C[H.sub.2] (R = C[H.sub.3], 2a; N[O.sub.2] 2b) a partir de la 4-vinylaniline et de deux equivalents de chlorures de sulfonyle, en presence de DMAR Quoique les reactions d'hydroboration des derives sulfanilamides 1 soient en competition avec les reactions d'hydrogenation, un choix judicieux d'un catalyseur A base d'un metal de transition permet d'obtenir la formation selective des boronates soit pfimaires ou secondaires lors des hydroborations du compose 2a. Mots cles : esters de l'acide boronique, hydroborations catalysees, sulfanilamides, vinylaniline. [Traduit par la Redaction]

A number of carbazoles are synthesized in good yields by the N-iodosuccinimide mediated heterocyclization of o-cyclohex-2'-enylanilines in acetonitrile at -10[degrees]C for 45 min followed by heating with palladium-charcoal (10%) in benzene (80[degrees]C) for 18-20 h. Key words: N-iodosuccinimide, hexahydrocarbazole, heterocyclization, carbazole, Claisen rearrangement.