Preparation and characterization of poly(amidoamine) dendrimers functionalized with a rhenium carbonyl complex and PEG as new IR probes for carbonyl metallo immunoassay

The first poly(amidoamine) (PAMAM) dendrimers tethered with both (η⁵-cyclopentadienyl) rhenium tricarbonyl (CpRe(CO)₃) units and polyethylene glycol (PEG) chains were prepared and characterized by combining NMR spectroscopy and Fourier-transform IR spectroscopy. Grafting of CpRe(CO)₃ units was achieved by reductive amination of formyl-CpRe(CO)₃ with the peripheral amines of generation 3 and 4 PAMAMs to yield dendrimers labeled with a variable number of CpRe(CO)₃ units, ranging from 8 to 14 for PAMAM-G3 and 17-30 for PAMAM-G4. PEG chains of different lengths were then attached to some of the remaining peripheral amines, and their respective ability to improve the solubility of the metallodendrimers in aqueous buffered media was evaluated. These metallodendrimers represent new infrared probes designed to be coupled to immunological reagents for the amplification of the IR signal in carbonyl metallo immunoassay (CMIA).     

Calorimetric analysis of the ethanolysis of 1,2-epoxybutane

Polyethers, which are produced by alcoholysis of oxiranes, are often used as solvents in chemical plants. The spectra of the products can be influenced by the choice of the catalyst (acid or base). The results of the base-catalyzed ethanolysis of 1,2-epoxybutane are displayed. The reaction was investigated calorimetrically by varying the molar ratio between ethanol and 1,2-epoxybutane, the starting temperature and the concentration of the catalyst sodium hydroxide. Additionally, the influence of the used alcohol will be shown in one example. To determine the activation parameters, the experiments were evaluated by the nonlinear software package TA-kin v3.3.     

Calorimetric investigation of palladium-catalysed telomerization of isoprene in solution

Telomerization of isoprene is characterized by intense thermal effects. The reaction system di-μ-chlorobis(η³-allyl)-dipalladium(II): tri-n-butylphosphine: sodium methylate: isoprene=1∶2∶3∶200 in a solvent-mixture of methanol∶benzene=1∶3 is used as a model. It is concluded that reaction of the catalyst combined with reduction of Pd(II) is followed by the telomerization reaction. There is a marked influence of Pd and phosphine concentration in the catalyst as well as concentration of isoprene. Results are available to optimize technical applications.     

The triple fluorescence of benzanilide and the dielectric medium modulation of its competitive excitation

The fluorescence of the benzanilide molecule at 298 K is inferred to consist of three independent electronic transitions associated with the single ground-state molecular species. F₁ (λ_max340 nm), the normal fluorescence is observed weakly and is ascribed to an n,π*,-π,π* mixed state. F′₂ is ascribed to the proton-transfer imidol tautomer fluorescence (previously reported) with unresolved λ_max (inferred at ≈460 nm). F″₂ is ascribed to a charge-transfer state fluorescence to the ground state, and occurs as a resolved CT transition in tetrahydrofuran at λ_max 520 nm. Comparison of the spectra of N-methylbenzanilide exhibiting only F₁ and F″₂ (CT) permitted the analysis of the benzanilide spectra.     

Application of an adiabatic precision calorimeter in the field of organic reactions

Adiabatic calorimetry is a suitable method for investigations of reactions because the generated heat remains completely in the reactor. For the investigation of organic reactions, the adiabatic precision calorimeter ACTRON 5 is used. The alcoholyses of phenyl isocyanate and 1,2-butyleneoxide were investigated. The temperature-time course was estimated by means of the nonlinear program TA-kin. Inclusion of the concentration-time course in the estimation procedure led to an increase in the reliability of the parameters. Probes were taken during isoperibolic measurements and were analysed by means of HPLC.     

Electron Energies, Dipole Electric Moments, and Distribution of the Laurdan Molecule over the Conformation States of Methyl Groups

Using the methods of molecular simulation and HyperChem v.5.0 programs (PM3 method), we carried out calculations of the principal spectroscopic characteristics and of the structure of the laurdan molecule in the ground and the first excited electronic states. The thermal static distribution of molecules over various possible orientations of the plane of methyl groups relative to the plane of the naphthalene bicycle was taken into account. The energies and dipole moments of these electronic states have been calculated as functions of the torsion angle of methyl groups. The existence of an additional mechanism of electronic spectrum broadening is shown; it is associated with thermal mismatch of the equilibrium orientations of the rotational fragment of the molecule and with the dependence of the electron transition frequency on the degree of deviation of the angle from the equilibrium value. The dependence of dipole moments on this angle has been found and calculated. This dependence is the strongest for the ground state. The maximum values of dipole moments in the ground and excited states are 4.0 and 7.6 D.     

Lifetime measurements of lithiumD-states

We report lifetime measurements of the 1s ² 3d ² D, 1s ²4d ² D, and 1s ²2p ² P states of lithium. The results τ=14.5±0.7 ns, τ=31.0±1.0 ns, and τ=27.9±1.0 ns respectively were obtained by time resolved detection of the resonance fluorescence following pulsed laser excitation.     

Chemiluminescent studies of excited Mg and Sr atoms with Cl2 in the beam-gas arrangement

The chemiluminescence resulting from the reactions M* + Cl₂ → MCl* + Cl (M = Mg, Sr) has been observed when an atomic beam of Mg or Sr containing a considerable fraction of atoms excited to the long-lived ³P states is intersected by an uncollimated beam of molecular chlorine.     

Experimental and theoretical determination of transition dipole moments of ethyl 5-(4-aminophenyl)- and 5-(4-dimethylaminophenyl)-3-amino-2,4-dicyanobenzoate

The absorption and fluorescence transition dipole moments ( $\hat M_{ge}$ and $\hat M_{eg}$ ) for ethyl 5-(4-aminophenyl)-3-amino-2, 4-dicyanobenzoate (EAADCy) and ethyl 5-(4-dimethylaminophenyl)-3-amino-2, 4-dicyanobenzoate (EDMAADCy) have been determined on the basis of the steady-state and time-resolved spectroscopic measurements and semiempirical quantum-chemical calculations. The values of the transition dipole moments of perpendicular and flattened forms of the investigated molecules were estimated as a function of the solvent polarity. Noted differences between the absorption and emission transition dipole moments (i.e., ${{\hat M_{ge} } \mathord{\left/ {\vphantom {{\hat M_{ge} } {\hat M_{eg} }}} \right. \kern-0em} {\hat M_{eg} }} \ne 1$ ) confirm that the change of the electronic and molecular structure take place in the excited state.