Supramolecular engineering through temperature-induced chemical modification of 2H-tetraphenylporphyrin on Ag(111): flat phenyl conformation and possible dehydrogenation reactions

Scratching the surface: Formation of a monolayer of 2H-tetraphenylporphyrins (2H-TPP) on Ag(111), either by sublimation of a multilayer in the range 525-600?K or by annealing (at the same temperature) a monolayer deposited at room temperature, induces a chemical modification of the molecules. Rotation of the phenyl rings into a flat conformation is observed and tentatively explained, by using DFT calculations, as a peculiar reaction due to molecular dehydrogenation.     

Communication: are metallic glasses different from other glasses? A closer look at their high frequency dynamics

Using high resolution inelastic x-ray scattering we studied the collective dynamics of the Pd(77)Si(16.5)Cu(6.5) metallic glass, focusing on the energy-momentum region where the boson peak appears. The dispersion relation and the width of the acoustic excitations are determined showing how the longitudinal acoustic modes maintain their dispersive character for frequencies well above the boson peak frequencies. Moreover, we prove that close to these frequencies there is a softening of the apparent sound speed indicating a failure of the Debye continuum approximation at the boson peak frequencies and challenging previous results on other metallic glasses.     

Amphiphilic antioxidants from "cashew nut shell liquid" (CNSL) waste

Hydrogenated cardanol and cardols, contained in industrial grade cardanol oil and obtained by distillation of the raw "cashew nut shell liquid" (CNSL), are easily transformed into efficient 4-thiaflavane antioxidants bearing a long alkyl chain on A ring and a catechol group on B ring.     

Non-linear fluorescence lifetime imaging of biological tissues

In recent years fluorescence microscopy has become a widely used tool for tissue imaging and spectroscopy. Optical techniques, based on both linear and non-linear excitation, have been broadly applied to imaging and characterization of biological tissues. Among fluorescence techniques used in tissue imaging applications, in recent years two and three-photon excited fluorescence have gained increased importance because of their high-resolution deep tissue imaging capability inside optically turbid samples. The main limitation of steady-state fluorescence imaging techniques consists in providing only morphological information; functional information is not detectable without technical improvements. A spectroscopic approach, based on lifetime measurement of tissue fluorescence, can provide functional information about tissue conditions, including its environment, red-ox state, and pH, and hence physiological characterization of the tissue under investigation. Measurement of the fluorescence lifetime is a very important issue for characterizing a biological tissue. Deviation of this property from a control value can be taken as an indicator of disorder and/or malignancy in diseased tissues. Even if much work on this topic has still to be done, including the interpretation of fluorescence lifetime data, we believe that this methodology will gain increasing importance in the field of biophotonics. In this paper, we review methodologies, potentials and results obtained by using fluorescence lifetime imaging microscopy for the investigation of biological tissues.     

Isomeric trimethylene and ethylene pendant-armed cross-bridged tetraazamacrocycles and in vitro/in vivo comparisions of their copper(II) complexes

Ethylene cross-bridged tetraamine macrocycles are useful chelators in coordination, catalytic, medicinal, and radiopharmaceutical chemistry. Springborg and co-workers developed trimethylene cross-bridged analogues, although their pendant-armed derivatives received little attention. We report here the synthesis of a bis-carboxymethyl pendant-armed cyclen with a trimethylene cross-bridge (C3B-DO2A) and its isomeric ethylene-cross-bridged homocyclen ligand (CB-TR2A) as well as their copper(II) complexes. The in vitro and in vivo properties of these complexes are compared with respect to their potential application as (64)Cu-radiopharmaceuticals in positron emission tomography (PET imaging). The inertness of Cu-C3B-DO2A to decomplexation is remarkable, exceeding that of Cu-CB-TE2A. Electrochemical reduction of Cu-CB-TR2A is quasi-reversible, whereas that of Cu-C3B-DO2A is irreversible. The reaction conditions for preparing (64)Cu-C3B-DO2A (microwaving at high temperature) are relatively harsh compared to (64)Cu-CB-TR2A (basic ethanol). The in vivo behavior of the (64)Cu complexes was evaluated in normal rats. Rapid and continual clearance of (64)Cu-CB-TR2A through the blood, liver, and kidneys suggests relatively good in vivo stability, albeit inferior to (64)Cu-CB-TE2A. Although (64)Cu-C3B-DO2A clears continually, the initial uptake is high and only about half is excreted within 22 h, suggesting poor stability and transchelation of (64)Cu to proteins in the blood and/or liver. These data suggest that in vitro inertness of a chelator complex may not always be a good indicator of in vivo stability.     

Synthesis of 3-amino-4-fluoropyrazoles

Fluorinated pyrazoles bearing additional functional groups that allow further functionalization are of considerable interest as building blocks in medicinal chemistry. The developed synthetic strategy for new 3-amino-4-fluoropyrazoles consists of a monofluorination of β-methylthio-β-enaminoketones using 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) toward the corresponding monofluorinated enaminoketones, followed by condensation with different hydrazines.     

60]Fullerene-based monolayers as neuroprotective biocompatible hybrid materials

Here we report on the surface immobilization of redox-active [60]fullerene derivatives and the consequent neuroprotective effects toward l-glutamate induced excitotoxicity in human derived undifferentiated neuroblastoma cells.     

Environmental effects on vibrational properties of carotenoids: experiments and calculations on peridinin

Carotenoids are employed in light-harvesting complexes of dinoflagellates with the two-fold aim to extend the spectral range of the antenna and to protect it from radiation damage. We have studied the effect of the environment on the vibrational properties of the carotenoid peridinin in different solvents by means of vibrational spectroscopies and QM/MM molecular dynamics simulations. Three prototypical solvents were considered: cyclohexane (an apolar/aprotic solvent), deuterated acetonitrile (a polar/aprotic solvent) and methanol (a polar/protic solvent). Thanks to effective normal mode analysis, we were able to assign the experimental Raman and IR bands and to clarify the effect of the solvent on band shifts. In the 1500-1650 cm(-1) region, seven vibrational modes of the polyene chain were identified and assigned to specific molecular vibrations. In the 1700-1800 cm(-1) region a strong progressive down-shift of the lactonic carbonyl frequency is observed passing from cyclohexane to methanol solutions. This has been rationalized here in terms of solvent polarity and solute-solvent hydrogen bond interactions. On the basis of our data we propose a classification of non-equivalent peridinins in the Peridinin-Chlorophyll-Proteins, light-harvesting complexes of dinoflagellates.     

Excitonic effects in two-dimensional vibrational spectra of liquid formamide

The linear and two-dimensional infrared (2DIR) responses of the amide I vibrational mode in liquid formamide are investigated experimentally and theoretically using molecular dynamics simulations. The recent method based on the numerical integration of the Schr?dinger equation is employed to calculate the 2DIR spectra. Special attention is devoted to the interplay of the structural dynamics and the excitonic nature of the amide I modes in determining the optical response of the studied system. In particular, combining experimental data, simulated spectra and analysis of the simulated atomic trajectory in terms of a transition dipole coupling model, we provide a convincing explanation of the peculiar features of the 2DIR spectra, which show a substantial increase of the antidiagonal bandwidth with increasing frequency. We point out that, at variance with liquid water, the 2DIR spectral profile of formamide is determined more by the excitonic nature of the vibrational states than by the fast structural dynamics responsible for the frequency fluctuations.     

Nonlinear Correction to the Euler Buckling Formula for Compressed Cylinders with Guided-Guided End Conditions

Euler’s celebrated buckling formula gives the critical load N for the buckling of a slender cylindrical column with radius B and length L as