Avo, J, Martins S, Parola AJ, Lima JC, Branco PS, Ramalho JPP, Pereira A.
2013.
A Family of Styrylcoumarins: Synthesis, Spectroscopic, Photophysical and Photochemical Properties, 2013. Chempluschem. 78:789-792.
Abstractn/a
Leydet, Y, Batat P, Jonusauskas G, Denisov S, Lima JC, Parola AJ, McClenaghan ND, Pina F.
2013.
Impact of Water on the Cis-Trans Photoisomerization of Hydroxychalcones, 2013. Journal of Physical Chemistry A. 117:4167-4173.
AbstractThe photochromism of a 2-hydroxychalcone has been studied in CH3CN and H2O/CH3OH (1/1, v/v), as well as in analogous deuterated solvents using steady-state (UV-vis absorption, H-1 and C-13 NMR) and time-resolved (ultrafast transient absorption and nanosecond flow flash photolysis) spectroscopies. Whereas the irradiation of trans-chalcone (Ct) under neutral pH conditions leads to the formation of the same final chromene derivative (B) in both media, two distinct photochemical mechanisms are proposed in agreement with thermodynamic and kinetic properties of the chemical reaction network at the ground state. Following light excitation, the first steps are identical in acetonitrile and aqueous solution: the Franck-Condon excited state rapidly populates the trans-chalcone singlet excited state (1)Ct* (LE), which evolves into a twisted state P-1*. This excited state is directly responsible for the photochemistry in acetonitrile in the nanosecond time scale (16 ns) leading to the formation of cis-chalcone (Cc) through a simple isomerization process. The resulting cis-chalcone evolves into the chromene B through a tautomerization process in the ground state (tau= 10 ms). Unlike in acetonitrile, in H2O/CH3OH (1/1, v/v), the P* state becomes unstable and evolves into a new state attributed to the tautomer (1)Q*. This state directly evolves into B in one photochemical step through a consecutive ultrafast tautomerization process followed by electrocyclization. This last case represents a new hypothesis in the photochromism of 2-hydroxychalcone derivatives.
Pacheco, MF, Pereira AI, Branco LC, Parola AJ.
2013.
Varnish removal from paintings using ionic liquids, 2013. Journal of Materials Chemistry A. 1:7016-7018.
AbstractThe possibility of replacing volatile and toxic organic solvents by ionic liquids (ILs) could contribute to safer procedures for conservation and restoration. This study introduces the use of ILs in varnish removal from paintings. The efficacy of this new procedure was assessed by applying different types of ILs in mock-ups of several painting materials and varnishes. The removal of IL residues from the surface of paintings was assessed mainly by FTIR-ATR. The application of ILs to a real painting is illustrated.
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