title: Structural volume changes upon triplet formation of water-soluble porphyrins depend on the resonant effect of the substituents.
abstract: Laser-induced optoacoustic spectroscopy was applied to evaluate the photoinduced structural volume changes upon triplet state formation, Δ(T)V, of an aqueous solution of 5,10,15,20-tetrakis-(4-carboxyphenyl)-porphin. Two molecular forms differing in the ionization state of the carboxylic groups at the para-position of the phenyl ring were studied. The contractions, Δ(T)V, for all water-soluble 5,10,15,20-tetra-aryl-porphyrin compounds studied to date show a linear correlation with the Hammett resonant σ(R) constant. This indicates that the resonance electronic communication spreading over the π-orbitals between the meso-aryl rings and the porphyrin macrocycle determines the molecular contraction of the aqueous sphere around the macrocycle in the triplet state.
authors.affiliation: B.I. Stepanov Institute of Physics of National Academy of Sciences, Nezavisimosti Ave, 68, 220072 Minsk, Belarus. kruk@imaph.bas-net.by
authors.forename: Mikalai M
authors.initials: MM
authors.lastname: Kruk
authors.forename: Silvia E
authors.initials: SE
authors.lastname: Braslavsky
mesh_terms: D006863:Hydrogen-Ion Concentration; D007834:Lasers; D061088:Photoacoustic Techniques; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D014867:Water / Q000737:chemistry*
chemical_list: D011166:Porphyrins; D014867:Water; C018395:tetracarboxyphenylporphine