Advisor(s) - Committee Chair
Robert Farina, Laurence Boucher, David Hartman
Department of Chemistry
Master of Science
The monomer-dimer equilibrium of CuTSPC4- was examined by spectral methods in aqueous solution over a total dye concentration of 2 x 10-8M to 8 x 10-7M at 24°C. The value obtained for the dimerization constant, KD,was 1.1 x 107M-1 which is smaller than literature values. However, the discrepancy is not appreciable considering the differences in the methods used and the experimental conditions of the different solutions. Spectral measurements of the dimerization constant were made at only one temperature since the spectral changes were quite small when the temperature was varied. This observation is consistent with the small heat of reaction associated with the dimerization process which has been reported in the literature for this system. A comparison of the dimerization constant of CuTSPC4- with other cations shows the following trend:
Cu2+ ≥ Ni2+ > H+ > Zn2+ ᷈ Vo2+ > Fe3+ > Co2+
The larger dimerization constants of CuTSPC4- and NiTSPC4- compared to the other tetrasulfonated phthalocyanines is attributed to the lack of axial ligand binding to these metals which enhances the dimerization process. Ligand binding studies made here and elsewhere on the CuTSPC4- and NiTSPC4- systems showed no evidence of ligand binding unlike the FeTSPC3- and CoTSPC4- systems where various ligands have been found to bind at the axial positions of these metals.
Kinetic measurements on the monomer-dimer equilibrium of CuTSPC4- in aqueous solution were made on the stopped-flow apparatus at 24°C using a total dye concentration range of 1 x 10-6 M to 1 x 10-5M. The rate constants for the formation and dissociation of the CuTSPC4- dimer are 3.24 x 106M-1s-1 and 0.27 s-1 , respectively. Activation parameters could not be obtained due to the small spectral changes which occur at different temperatures and hence cannot be measured on the stopped-flow apparatus. The kinetic data show that the formation and dissociation rate constants of CuTSPC4- in aqueous solution is similar to those of NiTSPC4- and VOTSPC4- systems. All these tetrasulfonated metallophthalocyanine systems show no evidence of ligand binding to the central metal ion and have similar dimerization constants. On the other hand the lower dimerization constant of CuTSPC4- relative to these systems can be attributed to the smaller rate constant associated with the formation of the dimer. The presence of axial ligands on the central metal ion is believed to inhibit the formation of the dimer in CoTSPC4-.
Chemistry | Physical Sciences and Mathematics
Scholl, Stephen, "Kinetic & Spectral Studies of Copper(II)-4,4',4",4'"-Tetrasulfophthalocyanine in Aqueous Solution" (1983). Masters Theses & Specialist Projects. Paper 2831.