Tuning Reactivity of Platinum(II) Complexes

[H 2 O -P t-(N N )-P t-O H 2 ] 4 + + O H -
[H 2 O -P t-(N N )-O H ] 3 + + O H -
K a1
K a2
13
[H 2 O -P t-(N N )-O H ] 3 + + H 2 O
[H O -P t-(N N )-O H ] 2+ + H 2 O
w here, N N = pzn, pmn, pdn, qzn, pht bridging ligand
Scheme 5.2: Proposed stepwise deprotonation for the pH dependence of the dinuclear
Pt(II) complexes.
A typical plot of the UV-Visible spectra obtained during the pH titrations for qzn is given
in Figure 5.2 (see also under Supplementary information Figure S5.2, for pmn). The pKa
values of the aqua Pt(II) complexes were calculated from the pH profiles, an example is
shown as an inset in Figure 5.2.
Absorbance
2.0
1.5
1.0
0.5
0.0
Absorbance
0.45
0.40
0.35
0.30
0.25
0.20
2 4 6 8 10
Wavelength(nm)
200 300 400 500
Wavelength (nm)
Figure 5.2: Variation of absorbance with pH for qzn complex in the pH range 2-10, I =
0.1 M HClO4, T = 25 °C. Inset: Titration curve at 305 nm for qzn complex.
All the diaqua complexes exhibited two inflection points and a fit of the absorbance data
to the standard Boltzmann equation, taken one at a time using the Origin 7.5 ®37
software, resulted in two pKa values which are presented in Table 5.2.
λ = 305 nm