A general TDDFT procedure has been set up that accurately evaluates the UV/vis absorption spectra of a series of new conjugated metal-free organic dyes based on the triphenylamine (TPA) moiety, which have recently been developed for dye-sensitized solar cells (DSSCs). It turns out that the BHandH functional, combined with the 6-311+G(2d,2p) basis set, gives reliable auxochromic shifts when the bulk solvation effects are included in the model. Indeed, the theoretical procedure provides λmax with a mean absolute deviation limited to ∼0.1 eV only. In addition, we give insights into the geometrical and electronic structures of the dyes, and we unravel the structural modifications allowing to optimize the properties of TPA-based DSSCs. This investigation aims at improving the electron-injection process, as well as the light-harvesting efficiency (LHE) of the dyes. To this purpose, we considered a set of about 20 new dyes, and starting from the TPC-1 structure, the following modifications help to get better electron injection and light-harvesting properties: (i) the extension of the bridging group by addition of an ethylene subunit between the two phenyl groups (TPC-14); (ii) the 16-COOH, 15-OMe, 1a,6-diCN functionalization (TPC-18); (iii) moving the terminal cyano acceptor from the 16 to the 15 position, while introducing two −OMe functions in 11 and 13 positions and/or grafting two −CN groups in 1a and 6 positions on the TPA moiety (TPC-20). These specific modifications induce a maximal increase of the LHE and a more exoenergic free enthalpy of injection (−2.20 eV compared to −1.84 eV for TPC-1). Finally, TPC-23 (which results from the TPC-14/TPC-20 combination) shows an improvement of both the spectroscopic and energetic parameters. Moreover, the molecular topology analysis demonstrates that the coplanarity between the anchoring and the bridging unit is broken, that is, the positive charge is not directly in contact with the TiO2 surface, and the recombination reaction is therefore inhibited.

All biological phenomena depend on molecular recognition, which is either intermolecular like in ligand binding to a macromolecule or intramolecular like in protein folding. As a result, understanding the relationship between the structure of proteins and the energetics of their stability and binding with others (bio)molecules is a very interesting point in biochemistry and biotechnology. It is essential to the engineering of stable proteins and to the structure-based design of pharmaceutical ligands. The parameter generally used to characterize the stability of a system (the folded and unfolded state of the protein for example) is the equilibrium constant (K) or the free energy (deltaG(o)), which is the sum of enthalpic (deltaH(o)) and entropic (deltaS(o)) terms. These parameters are temperature dependent through the heat capacity change (deltaCp). The thermodynamic parameters deltaH(o) and deltaCp can be derived from spectroscopic experiments, using the van't Hoff method, or measured directly using calorimetry. Along with isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC) is a powerful method, less described than ITC, for measuring directly the thermodynamic parameters which characterize biomolecules. In this article, we summarize the principal thermodynamics parameters, describe the DSC approach and review some systems to which it has been applied. DSC is much used for the study of the stability and the folding of biomolecules, but it can also be applied in order to understand biomolecular interactions and can thus be an interesting technique in the process of drug design.

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The successful controlled homopolymerization of acrylonitrile (AN) by cobalt-mediated radical polymerization (CMRP) is reported for the first time. As a rule, initiation of the polymerization was carried out starting from a conventional azo-initiator (V-70) in the presence of bis(acetylacetonato)cobalt(II) ([Co(acac)(2)]) but also by using organocobalt(III) adducts. Molar concentration ratios of the reactants, the temperature, and the solvent were tuned, and the effect of these parameters on the course of the polymerization is discussed in detail. The best level of control was observed when the AN polymerization was initiated by an organocobalt(III) adduct at 0 degrees C in dimethyl sulfoxide. Under these conditions, poly(acrylonitrile) with a predictable molar mass and molar mass distribution as low as 1.1 was prepared. A combination of kinetic data, X-ray analyses, and DFT calculations were used to rationalize the results and to draw conclusions on the key role played by the solvent molecules in the process. These important mechanistic insights also permit an explanation of the unexpected "solvent effect" that allows the preparation of well-defined poly(vinyl acetate)-b-poly(acrylonitrile) by CMRP.

The incremental hydration of the glycine cation is investigated using an ab initio approach fully correcting for basis set superposition errors and explicitly incorporating electron-correlation effects. Structures with zero to four surrounding water molecules have been determined. It is demonstrated that the successive aggregates follow a Darwinian family tree, the most stable complexes systematically belonging to the same branch of the tree. In strong contrast with neutral glycine, the direct hydrogen bonding to the glycine cation is favored over bridging water structures. The agreement between experimental and theoretical hydration enthalpies and Gibbs free energies is impressive, as ab initio estimates almost systematically fit the experimental error bars. For GlyH(+)-(H2O) and GlyH(+)-(H2O)3, we show that two structures are generated by the experimental setup. The present approach also resolves most of the previous theory/experiment discrepancies and provides patterns for the evolution of the vibrational spectra: a decrease of the hydrogen-bond stretching frequency indicating second-shell water molecules. Additionally, the impact of bulk solvent solvation is investigated, as four discrete water molecules still do not fully hydrate the protonated glycine.