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We report the successful synthesis and spectroscopic characterization of a novel, water soluble anthanthrene-based derivative, 6,12-bis(TEG)anthanthrene 3. The presence of the two long ethylene glycol side chains gives this large, six-membered polycyclic aromatic compound a high aqueous solubility. It exhibits UV-vis absorption properties similar to those of anthanthrene itself, indicating that the side chains do not have a significant effect on the electronic structure of the central chromophore. The compound exhibits strong, polarity-sensitive fluorescence in aqueous solution in the blue-green region of the spectrum, with a fluorescence quantum yield of 0.13 and a polarity sensitivity factor (PSF) of 2.0. The utility of this new fluorescent molecule as a probe of supramolecular complexation was demonstrated by its inclusion into the molecular host hydroxypropyl-[beta]-cyclodextrin in aqueous solution. Strictly 1:1 inclusion was observed, with a moderately strong binding constant K of 650 [M.sup.-1]. This new fluorescence probe has significant potential applications in fluorescence-based studies of aqueous biochemical and supramolecular systems. Key words: polycyclic aromatic hydrocarbons, PAH, fluorescence, fluorescent probe, cyclodextrins, host-guest inclusion complexes, supramolecular chemistry. Nous presentons la synthese et la caracterisation spectroscopique d'un nouveau derive d'anthanthrene hydrosoluble, le 6,12bis(TEG)anthanthrene 3. La presence des deux longues chaines laterales d'ethyleneglycol confere une grande solubilite aqueuse a ce compose aromatique polycyclique de grande taille a 6 cycles. Le compose presente des proprietes d'absorption dans l'UV-vis semblables a celles de l'anthanthrene en tant que tel, ce qui indique que les chaines laterales n'ont pas d'effet significatif sur la structure electronique du chromophore central. En solution aqueuse, ce compose presente une forte fluorescence sensible a la polarite dans la region bleu-vert du spectre, avec un rendement quantique de fluorescence de 0,13 et un facteur de sensibilite a la polarite (FSP) de 2,0. L'inclusion de cette nouvelle molecule fluorescente dans l'hote moleculaire hydroxypropyl-[.sup.-]cyclodextrine en solution aqueuse nous a permis de demontrer son utilite comme sonde de complexation supramoleculaire. Nous avons observe l'inclusion dans un rapport strict de 1:1, avec une constante de liaison moderement forte (K = 650 [M.sup.-1]). Cette nouvelle sonde de fluorescence pourrait etre d'une grande utilite dans des etudes sur la fluorescence de systemes biochimiques et supramoleculaires en milieu aqueux. [Traduit par la Redaction] Mots-cles : hydrocarbures aromatiques polycycliques, HAP, fluorescence, sonde fluorescente, cyclodextrines, complexes d'inclusion hote-invite, chimie supramoleculaire., Introduction Polycyclic aromatic hydrocarbons (PAHs) are an important family of fluorescent molecules, with interesting photophysical properties, (1-3) which provide significant utility as environmentally sensitive fluorescent probes. (4,5) Such useful fluorescent [...]

Fluorescence spectroscopy provides an excellent technique for investigating heterogeneous systems, due to its high sensitivity and the large effect of the local environment on molecular emission. In addition, the use of polarity-sensitive fluorescent probes as guests in supramolecular host-guest inclusion complexes can be exploited in fluorescent sensors. This paper identifies, tabulates, and quantifies a series of useful polarity-sensitive fluorescent probes, with a wide range of polarity-dependent fluorescence responses. The degree of polarity sensitivity is quantified using the polarity sensitivity factor (PSF), developed in our laboratory. In most cases, such polarity-sensitive probes show increased emission as the local polarity is decreased (PSF > 1); 10 such probes are described. However, less commonly, 'reverse polarity dependence' can occur in which probe emission decreases with decreasing polarity (PSF < 1); four such probes are described. The mechanism for the observed polarity-induced fluorescence changes will also be discussed in selected representative cases. The purpose of this paper is to present details on a broad arsenal of polarity-sensitive fluorescence probes with varying properties, with potentially useful applications in the study of heterogeneous systems, including inclusion phenomena, and in practical applications such as fluorescent sensors, which will be useful to researchers studying supramolecular and other heterogeneous systems using fluorescence spectroscopy. Key words: fluorescence, fluorescent probes, polarity sensitivity, solvent effects, sensors. La spectroscopie de fluorescence constitue une excellente technique pour l'etude des systemes heterogenes grâce a sa sensibilite elevee et a l'ampleur de l'effet d'environnement local sur l'emission moleculaire. De plus, l'utilisation de sondes fluorescentes sensibles a la polarite comme invite dans des complexes d'inclusion de type hôte-invite supramoleculaires peut etre exploitee dans des capteurs fluorescents. Dans le present article, nous decrivons, compilons et quantifions une serie de sondes fluorescentes sensibles a la polarite dont la grande etendue des reponses fluorescentes en fonction de la polarite offre une possibilite d'application pratique. Nous avons quantifie le degre de sensibilite a la polarite au moyen du facteur de sensibilite a la polarite (FSP), une mesure developpee dans notre laboratoire. Dans la plupart des cas, de telles sondes sensibles a la polarite presentent un accroissement de l'emission a mesure que la polarite locale augmente (FSP > 1); dix de ces sondes sont decrites. Or, il arrive, moins souvent toutefois, qu'une << dependance inverse a la polarite >> se produise, où l'emission de la sonde decroit a mesure que la polarite diminue (FSP < 1); quatre de ces sondes sont decrites. Nous commentons egalement, dans certains cas representatifs, le mecanisme a l'origine des variations de fluorescence induites par la polarite que nous observons. Cet article vise a presenter des informations detaillees sur une vaste panoplie de sondes sensibles a la fluorescence aux proprietes variables et qui pourraient se reveler utiles dans l'etude de systemes heterogenes, dont l'etude des phenomenes d'inclusion, et dans des applications pratiques comme les capteurs fluorescents. Ces informations pourraient etre utiles aux chercheurs qui etudient les systemes supramoleculaires et d'autres systemes heterogenes a l'aide de la spectroscopie de fluorescence. [Traduit par la Redaction] Mots-cles : fluorescence, sondes fluorescentes, sensibilite a la polarite, effets de solvant, capteurs., Introduction Fluorescence spectroscopy (1) has been extensively and effectively applied to the study of heterogeneous environments (2,3) such as proteins, (4) membranes (5) and other biological structures, (6) supra-molecular inclusion [...]

Proteins are biomolecules with potential applications in agriculture, food sciences, pharmaceutics, biotechnology, and drug delivery. Interactions of hydrophilic and biocompatible polymers with proteins may impart proteolytic stability, improving the therapeutic effects of biomolecules and also acting as excipients for the prolonged storage of proteins under harsh conditions. The interactions of hydrophilic and stealth polymers such as poly(ethylene glycol), poly(trehalose), and zwitterionic polymers with various proteins are well studied. This study evaluates the molecular interactions of hydrophilic and optically active poly(vitamin B5 analogous methacrylamide) (poly(B5AMA)) with model proteins by fluorescence spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and circular dichroism (CD) spectroscopy analysis. The optically active hydrophilic polymers prepared using chiral monomers of R-(+)- and S-(−)-B5AMA by the photo-iniferter reversible addition fragmentation chain transfer (RAFT) polymerization showed concentration-dependent weak interactions of the polymers with bovine serum albumin and lysozyme proteins. Poly(B5AMA) also exhibited a concentration-dependent protein stabilizing effect at elevated temperatures, and no effect of the stereoisomers of polymers on protein thermal stability was observed. NMR analysis, however, showed poly(B5AMA) stereoisomer-dependent changes in the secondary structure of proteins. [ABSTRACT FROM AUTHOR]

This article describes an interesting variation on the use of interactive anonymous quizzes (IAQs) in the chemistry classroom. In this variation, IAQs are used to introduce new material or topics in a course, as opposed to their traditional use for reviewing previously covered material. Two examples of IAQs used to introduce new topics in a second-year environmental chemistry class are presented, and the class results over a five year period are described and discussed. This new approach promotes critical thinking as well as peer learning, promotes interesting and thoughtful discussions, provides the instructor with an indication of the class pre-knowledge of the new topic, and provides an interesting and stimulating transition between topics in a course. These IAQs provide an excellent method for engaging students and introducing them to new ideas and concepts and are a low-risk, time-efficient, and versatile way to introduce active learning into a chemistry classroom. (Contains 2 tables and 1 note.)

The host properties of a bistren cage compound, previously reported to be an efficient anion sensor, are shown to include encapsulation of small aromatic guest molecules. It is also shown that the intrinsic fluorescence of this cage compound, arising from the anthracenyl moiety in its structure, is sensitive to the encapsulation of aromatic guests in aqueous solution and can be used to measure the binding constants for any such guest. This makes this bistren cage a rare example of a fluorescent host for aromatic guests, and suggests potential applications of this compound as a versatile fluorescent sensor for a variety of guests of interest. The binding of a number of benzene derivatives was studied; these were all found to form 1:2 host-guest inclusion complexes with a wide range in total binding constants ([K.sub.1][K.sub.2]), from 6.4 x [10.sup.3] to 3.5 x [10.sup.7] [(mol/L).sup.-2], indicating a significant degree of selectivity for different benzene derivatives. The binding strength was found to depend on both the guest polarity and aqueous solubility. Key words: bistren cage, host-guest inclusion, fluorescent host, binding constants. Pour un compose bistrene en forme de cage qui, selon des etudes anterieures, serait un senseur anionique efficace, on demontre que ses proprietes hotes incluent l'encapsulation de petites molecules aromatiques invitees. On demontre aussi que la fluorescence intrinseque de ce compose en cage, qui tire son origine dans la portion anthracenyle de sa structure, est sensible a l'encapsulation de molecules aromatiques hotes dans la solution aqueuse et qu'elle peut etre utilisee pour mesurer les constantes de fixation de telles molecules invitees. Cette propriete fait que bistrene en forme de cage est un rare exemple d'un hote pour invites aromatiques et suggere des applications potentielles de ce compose comme senseur fluorescent versatile pour une variete de molecules invitees presentant des interets divers. On a etudie la fixation d'un certain nombre de derives aromatiques qui forment tous des complexes d'inclusion hote:invite 1:2 pour lesquels les constantes de fixation totale ([K.sub.1][K.sub.2]) s'etalent de 6,4 x [10.sup.3] a 3,5 x [10.sup.7] [(mol/L).sup.-2], ce qui suggere un degre significatif de selectivite pour les differents derives du benzene. On a note que la force de la fixation depend a la fois de la polarite de la molecule invitee et de la solubilite dans l'eau. Mots-cles : cage bistrene, inclusion hote-invite, hote fluorescent, constantes de fixation. [Traduit par la Redaction], Introduction Supramolecular host-guest inclusion complexes, in which a small guest molecule becomes encapsulated within the internal cavity of a larger cage-like host molecule, have shown tremendous utility for molecular recognition, [...]

The molecular-recognition properties of the cucurbit[6]uril analogue in aqueous buffer toward a variety of guests including alkanediamines, aromatics, amino acids and nucleobases are studied by fluorescence spectroscopy. Curcurbit[6]uril analogue functions as a versatile fluorescent sensor for the presence of a wide range of chemically and biologically important substances in aqueous solution including nitroaromatics, neurotransmitters, amino acids, and nucleobases.

Photolysis of 2-, 3-, and 4-diaxoacetylpyridines in CH3CN containing n-BuNH2 results in the formation of two transients in each case, as observed by time-resolved IR and UV spectroscopy. In the amide enols from 3- and 4- pyridylketenes, tautomerization to the amide is by contrast accelerated relative to the amide enol from phenylketene, a result attributable to the electron withdrawing and acidifying influence of the ring nitrogen.

Various methods for the enhancement of the fluorescence of the pesticide azinphos-methyl are reported. The addition of hydroxypropyl-[beta]-cyclodextrin was found to moderately enhance the fluorescence by a factor of three, presumably via inclusion of the pesticide into the cyclodextrin cavity. This complexation was found to occur with an association constant of 690 [+ or -] 140 [M.sup.-1]. This enhancement was found to be too low to be useful in a fluorescence-based analytical method for this pesticide. Exposure of azinphos-methyl to UV light was also found to result in enhanced fluorescence, with much larger enhancement than in the case of addition of cyclodextrins. This enhancement was presumed to occur via photolysis of azinphos-methyl to a more fluorescent photoproduct. However, the difficulty of providing a constant UV dosage prevents its useful application as a fluorescence-based analytical method. Finally, it was found that base hydrolysis of azinphos-methyl resulted in a very large fluorescence enhancement. Although this enhancement was previously reported in the literature, it was found that contrary to the published reports, the hydrolysis occurred rapidly at room temperature, with no need for carrying out the reaction at increased temperature. Fluorescence enhancements of a factor of 300 were obtained by simply adding the appropriate amount of an aqueous NaOH solution to the aqueous azinphos-methyl sample. This procedure was used as the basis of a simple fluorescence-based analytical method for azinphos-methyl in water, with excellent linear calibration curves obtained down to concentrations of 5 ppb. Key words: fluorescence spectroscopy, pesticides, azinphos-methyl, fluorescence enhancement, host-guest inclusion.

Fluorescence enhancement of a probe molecule in solution by the container molecule cucurbituril (CB) is reported for the first time. The fluorescence of the probe 2-anilinonaphthalene-6-sulfonate (2,6-ANS) in aqueous [Na.sub.2]S[O.sub.4] solution is found to increase by a maximum factor of 5.0 upon addition of cucurbituril. This fluorescence enhancement is the result of the formation of a host-guest inclusion complex, in which the guest 2,6-ANS is incorporated inside the cavity of the host, cucurbituril. Measurement of the enhancement as a function of cucurbituril concentration yielded a value of the equilibrium constant (K) of 52 [+ or -] 10 [M.sup.-1]. It is proposed that the mode of inclusion involves the phenyl group of the 2,6-ANS, because of the relatively small size of the cucurbituril cavity. It is further proposed that the observed enhancement is a result of loss of rotational mobility of the phenyl ring relative to the naphthyl fluorophore of 2,6-ANS upon inclusion of the phenyl ring. Since the name cucurbituril is derived from the Latin word for "pumpkin," this fluorescent host-guest complex is referred to as a "molecular Jack O'Lantern," with the 2,6-ANS serving as the candle. Key words: host-guest chemistry, fluorescence, cucurbituril, inclusion compounds.

This article discusses use of supra molecular chemistry in chemical research and importance of teaching its concept and applications to advanced undergraduate students.

Research is presented describing the fluorescent properties and structure of the solid compound formed from mixing aqueous salt solutions of the fluorescent probe 1-anilino-8-naphthalenesulfonate (1,8-ANS) and the cage compound cucurbituril.

Alpha-oxoketenes have interesting structural features, synthetic utility and high reactivity. 6-oxocyclohexa-2,4-dienylideneketene was generated by laser flash photolysis and observed in solution. Its reactivity with H(sub2)0, MeOH and Et(sub2)NH with relative reactivities of 1.0, 2.0 and 73, was measured. The hydration is thought to occur by in-plane attack of the H(sub2)0 molecule on the ketenyl carbonyl via a pseudopericyclic transition state.

The formation of several 1,2-bisketenes by the photolysis of cyclobutenediones has been studied, and time-resolved infrared spectroscopy has been used to observe the species. UV spectroscopy was used to measure the rates of thermal conversion of 1,2-bisketenes back to cyclobutenediones, including ketenes with CN,super6, Br,super7 alkynyl,super8 thio,super9 and alkoxysuper10 substituents.

The UV-visible laser flash photolysis technique was used to monitor the absolute kinetics of the reaction of some alkyl and aryl secondary aminium radicals with olefins in acidic acetonitrile solutions. In general, the bimolecular rate constants for the piperidinium radical increased with decreasing ionization potential of the olefin. The rate constants for diethylaminium radicals were significantly smaller than those for the piperidinium radical, suggesting that steric factors strongly affect aminium radical reactions.

Time-resolved UV-vis and infrared laser flash photolysis methods help examine the reactivity of the azidyl radical, N(sub 3)(super .), with olefins, using the pseudohalogen azidyl radical anion N(sub 6)(super.-). The reaction of N(sub 3)(super .) with alkyl olefins does not involve hydrogen atom transfer, suggesting that the reaction proceeds through addition. These addition reactions are controlled by polar effects and are free of steric factors.

Coordination polymers based on Zn(II)-4,4'-bipyridine (Zn-bipy) frameworks containing pyrene intercalated between adjacent layers and aromatic solvent molecules enclathrated within the framework cavities are prepared and characterized. The compounds are highly fluorescent and show broad, featureless emission spectra significantly red-shifted relative to pyrene monomer fluorescence.

The host properties of a new cucurbit[6]uril analogue, studied by fluorescence and (super 1)H NMR spectroscopy, are described. The host is intrinsically fluorescent, and this fluorescence is sensitive to guest encapsulation, which helps in the study of the inclusion of nonfluorescent guests by fluorescence spectroscopy.

Cucurbituril(super 1-4) is an interesting cage compound consisting of a sigma -bonded C,N framework, with two opposing portals defined by carbonyl groups. The association of the two probes 2,6 and 1,8-ANS via complexation with the macrocyclic host cucurbit[7] uril (Q7) is studied using fluorescence, (super 1)H NMR spectroscopy, and molecular modeling.

The lifetimes of the S1 states of azulene, azulene-d8, 4,6,8-trimethylazulene, and guaiazulene (1,4-dimethyl-7-isopropylazulene) have been measured in three nonviscous solvents of different polarity and structure using a two-photon, two-color, pump–probe method with subpicosecond time resolution. A significant solvent effect is measured. The rate constants for S1[larger_closed_square]S0 internal conversion in all four compounds in all three solvents exhibit one common S1–S0 energy gap law correlation, indicating that variations in the electronic relaxation rates are governed exclusively by changes in the Franck–Condon factors for the transition. No effect is observed when the exciting wavelength is changed, indicating that vibrational relaxation is occurring on a time scale which is faster than that of electronic relaxation in these systems. No significant deuterium isotope effect is measured in azulene, indicating that high frequency C–H(D) stretching vibrations do not act as significant accepting modes in the radiationless transition. [ABSTRACT FROM AUTHOR]

In order to clarify previous conflicting reports concerning the existence of an order–disorder phase transition in NH4AlF4 at T∼150 K, the heat capacity of this compound has been measured from T=15 to 305 K, by adiabatic calorimetry. The calorimetric results show a small anomaly in Cp centered at T=157 K (ΔS=0.02 R), and this is attributed to a soft mode phase transition associated with slight changes in the (AlF4)n-n layers. Analysis of the contribution of ammonium ion disorder to the heat capacity indicates that the ammonium ion disorder is gradually thermally excited, and can be adequately described by a three-dimensional Einstein oscillator for which θE ∼400 K. There is no evidence of an order–disorder phase transition association with the ammonium ions. [ABSTRACT FROM AUTHOR]