Tuning Reactivity of Platinum(II) Complexes

corrections due to dilution, a large volume (200ml) of each of the complex solutions was
used during the titrations. Spectrophotometric pH titrations were carried out using
NaOH as the base. Subsequent pH changes were obtained by stepwise additions of
crushed solid NaOH pellets in the pH range 2-3, micropipette dropwise addition of
saturated, 1.0 and 0.1 M NaOH or conc. HClO4 (for reversibility of the pH) to the bulk of
the complex solution, prior to withdrawal of 2 ml aliquots of the solution. After each of
the measurements, the aliquots were not returned to the sample solutions to avoid in
situ contamination by chloride ions from the pH electrode.
6.2.8 Computational Details
The geometries of all the complexes in aqua-form with total charges of +4 were
optimized, in vacuo, using Density functional Theory (DFT) utilizing the B3LYP, 42 a three
parameter hybrid functional method, and the LACVP** (Los Alamos Core Valence
Potentials) 43 pseudo-potentials basis set as implemented in Spartan `04 for Windows ®
program. B3LYP relates to Becke’s three parameter hybrid functional 42 that has been
proven to be superior to traditional functionals. The mononuclear complex, cis-
[Pt(H2O)(NH3)2(4-methylpyridine)] +2 , Pt4, is included for comparative purposes with
respect to the pKa and DFT results of Pt3
6.2.9 Kinetic Measurements
Spectral changes resulting from mixing separately each of the complexes Pt1, Pt2, and
Pt3 with ligand solutions were recorded over the wavelength range 200-600 nm to
establish a suitable wavelength at which the kinetic measurement would be performed
on a Varian Cary 100 Bio spectrophotometer. The kinetics of the lability of coordinated
water was followed spectrophotometrically by monitoring the change in absorbance at
suitable wavelengths. The wavelength values are given as supplementary information in
Table S6.1 (Appendix 6).
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