The reverse micelles of triblock copolymers poly(ethylene oxide)-block-poly(propylene oxide)-block-poly-(ethylene oxide) EO 6 PO 36 EO 6 (Pluronic L62) and EO 13 PO 30 EO 13 (Pluronic L64) in ternary (copolymer/oxylene/water) and binary (copolymer/water) systems with different water contents were evidenced and investigated by fluorescence, absorption, and spin probe techniques. The spectral parameters of the polarity sensitive probes, 1-anilinonaphthalene-8-sulfonic acid (ANS), dansylhexadecylamine (Dansyl), pyrenesulfonic acid (PSA), 4-nitropyridine N-oxide (NP) and 4-(N,N′-dimethyl-N-alkyl)ammonium 2,2′,6,6′-tetramethylpiperidine-1-oxyl iodide (CAT n), were related to the local hydration and polarity by comparison with a series of poly(oxyethylene)/water (TEG/water) calibration mixtures. The data were concordant and complementary, resulting in polarity profiles of the core for all systems and the relative radial positioning of the probes. The order of decreasing hydrophobic character found was Dansyl > NP > CAT 16 > CAT 11 ∼ ANS > CAT 8 > PSA > CAT 4 > CAT 1. A linear relationship was found between the R A (the intensity ratio of two absorption vibronic bands) of PSA in ethanol/water mixtures and Kosower's Z parameter (Z ) -29.0R A + 177.83). Thus, by means of the calibration mixtures, converting different spectral parameters of the mentioned probes, the local polarity values were expressed in terms of Z values. The role of water as a prerequisite for micellization was evidenced and so was the minimum quantity of water required in the ternary systems (W ) 0.2 for L64 and W ) 0.4 for L62). Regarding the water distribution, a more advanced segregation of water is observed in the ternary systems as compared to the binary ones, pointing to the role played by the solvent in this process. Evidence was found for a considerable solvation of the poly(propylene oxide) block with xylene, leading to a looser packing in the corona and in the poly(ethylene oxide) core. In the case of ternary systems, the ordering of the polymer chains in the micelles, measured with a series of x-doxylstearic acid spin probes, indicates the progress of micellar organization with increasing water content, the order increasing and extending further from the polar core and the corona becoming less penetrable. In the corresponding binary systems, the polymer chain rotation is "frozen" at room temperature (295 K) and even at 320 K. The structural characteristics of L62 and L64 ternary systems are rather similar, a conclusion suggested especially by the information the polar probes supplied. There are differences in the microenvironment of more hydrophobic probes, which sense a higher hydrophobicity in the case of L62, the increase of microviscosity being also more marked in the L62 system.

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Three new pyridylindolizine derivatives, 1, 2, 3-tricarbometoxi-7-(4-pyridyl)-pyrrolo[1, 2-a]pyridine (I), 1,2-dicarboethoxy-3-(4-bromobenzoyl)-7-(4-pyridyl)-pyrrolo[1,2-a]pyridine (II) and its isomer 1,2-dicarboethoxy-3- (4-bromobenzoyl) -5- (2-pyridyl) -pyrrolo[1, 2-a]pyridine (III) have been investigated in different solutions by UV-VIS absorption, steady-state, and time-resolved fluorescence methods. The effects of the substituent and solvent on the spectroscopic properties have been demonstrated. The fluorescence decay data could be fitted to a single-exponential function. The lifetime values are higher in protic polar than in aprotic apolar solvents for compound I. In the case of compounds II and III the fluorescence intensities and lifetimes are very low, with the exception of III in aprotic solvents. The absorption and fluorescence properties of the compounds showed a solvent dependence.

The fluorescence properties of three pyridylindolizine derivatives (one tricarbomethoxy-7-pyridyl-pyrrolopyridine and two dicarboethoxy-3-bromobenzoyl-7-pyridyl-pyrrolopyridines) have been investigated by applying density functional theory (DFT) and the time-dependent DFT (TDDFT). Performances of two hybrid-type functionals (BH&HLYP and B3LYP) and one generalized gradient approximation (GGA) functional (PBE) as well as three basis sets (SV(P), DZP, and TZVP) have been assessed. The solvent environment has been modeled with the conductor-like screening model (COSMO). Of the three functionals only BH&HLYP is able to yield reasonable estimates for all the studied indolizine derivatives whereas the success of the PBE and B3LYP functionals is highly dependent on the structure of the studied molecule. The SV(P) basis set provides geometrical changes as well as fluorescence maxima and Stokes shifts that agree with those obtained with DZP and TZVP. When a nonpolar solvent is used, COSMO is able to reproduce the experimental fluorescence maxima and Stokes shifts well. However, the agreement between the calculations and experiments is not as good when a solvent with higher polarity is used.

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