Multicolour Optical Coding from a Series of Luminescent Lanthanide Complexes with a Unique Antenna

The bis‐tetrazolate‐pyridine ligand H₂pytz sensitises efficiently the visible and/or near‐IR luminescence emission of ten lanthanide cations (Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb). The Ln^III complexes present sizeable quantum yields in both domains with a single excitation source. The wide range of possible colour combinations in water, organic solvents and the solid state makes the complexes very attractive for labelling and encoding.     

Existence of a compensation law for internal quenching of fluorescence

The existence of a compensation law correlating the pre-exponential factor and the activation energy of the rate parameter for internal quenching of fluorescence is established and explained using theoretical results obtained by Lin. Arguments in favour of S₁ ? T₁ intersystem crossing as the dominating process in non-radiative decay, are presented.     

Force-field modeling through quantum mechanical calculations: molecular dynamics simulations of a nematogenic molecule in its condensed phases

Interaction energy of the 4-n-pentyloxy-4'-cyanobiphenyl (5OCB) dimer is computed at MP2 level, for many geometrical arrangements using the Fragmentation Reconstruction Method (FRM). DFT calculations are performed for a number of geometries of the monomer. The resulting database is used to parameterize an atomistic intra- and inter-molecular force-field suitable for classical bulk simulations. Several structural and dynamical properties in 5OCB isotropic and liquid crystalline phases are computed from molecular dynamics simulation mainly in the NPT ensemble. Lengthy runs (more than 70 ns) and large sample sizes (up to 806 molecules) were used to determine the nematic to isotropic transition temperature up to a precision of few K. Good agreement was found in most of the investigated properties, thus validating the accuracy of the proposed model potential, only derived by quantum mechanical calculations.     

A model study of proton transfer in the H5O2 complex on a bidimensional potential energy surface

We have studied the hydrogen-bonded complex H₃O⁻-H₂O as a model for proton transfer in water. Quantum mechanical computations have been performed in two dimensions (the coordinates are the position of the hydrogen atom and the O-O distance, for a linear geometry), for investigating static and dynamical properties. The validity of the adiabatic separation of the O-O and O-H … O motions has been tested, showing that it holds only in a very restricted range of O-O distances. An initial wavepacket (created by an external perturbation), localized close to one of the two minima, is propagated in time. The proton flux is divided into two contributions, one along the reaction path and the other mainly due to tunnelling.     

Non-stationary states in chemistry

After a brief introduction to the theoretical area concerning the propagation of non-stationary states, two examples of our activities in the field of time-dependent processes are presented and discussed. The first concerns the possibility of controlling photochemical and photophysical processes by properly shaped, short, weak laser pulses. A theoretical approach developed by our group is briefly reviewed and a new example is presented on the control of the energy deposition in a model linear aggregate of ten chromophores. The second example deals with hydrogen transfer in DNA base pairs and presents the result of a time-dependent calculation on adenine–thymine and guanine–cytosine pairs. These calculations show a coherent, periodic behaviour and make it evident that imino-enol tautomerism cannot be interpreted as a source of mutations, since it would generate too many mutation points along the DNA.     

Heat shock protein 70 alters the endosome-lysosomal localization of huntingtin

Huntington's disease is caused by CAG trinucleotide expansions in the gene encoding huntingtin. N- terminal fragments of huntingtin with polyglutamine produce aggregates in the endosome-lysosomal system, where proteolytic fragments of huntingtin is generated. Heat shock protein 70 (HSP70) prevents the formation of protein aggregates, but the effect of HSP70 on the huntingtin in the endosome-lysosomal system is unknown. This study was to determine whether HSP70 alters the distribution of huntingtin in endosome-lysosomal system. HSP70 expressing stable cells (NIH/3T3 or cerebral hybrid cell line A1) were generated, and mutant [(CAG)(100)] huntingtin was transiently overexpressed. Analysis of subcellular distribution by immunocytochemistry or proteolysis cleavage by Western blotting was performed. 18 CAG repeat wild type [WT; (CAG)(18)] huntingtin was used as a control. Cells with huntingtin showed patterns of endosome-lysosomal accumulation, from a "dispersed vacuole (DV)" type into a coalescent "perinuclear vacuole (PV)" type over time. In WT huntingtin, HSP70 increased the cells with the PV types that enhanced the proteolytic cleavage of huntingtin. However, HSP70 reduced cells of the DV and PV types expressing mutant huntingtin, that result in less proteolysis than that of control. In addition, intranuclear inclusions were formed only in mutant cells, which was not affected by HSP70. These results suggest that HSP70 alters the distribution of huntingtin in the endosome- lysosomal system, and that this contributes to huntingtin proteolysis.     

Rigid Conjugated Twisted Truxene Dimers and Trimers as Electron Acceptors

A new class of rigid twisted truxenone oligomers with an enlarged π backbone has been established by oxidative dimerization reactions. The resulting extended conjugated systems have large extinction coefficients and low‐lying LUMO levels and show good solubility in common organic solvents, thus making them attractive compounds as new electron acceptors in organic electronics. Their suitability as electron acceptors has been demonstrated in bulk‐heterojunction organic solar cells with poly({4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl}{3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl}) (PTB7) as the donor material.