Abstract:
The rate of Chloride substitution from [Pt{(40
-ethylglycoxyl)-2,20
:60
,200-terpyridine}Cl]Cl([PtCl(tpy)eg]Cl),
[Pt{(40
-diethylglycoxyl)-2,20
:60
,200-terpyridine}Cl]Cl([PtCl(tpy)deg]Cl) and [Pt{(40
-triethylglycoxyl)-
2,20
:60
,200-terpyridine}Cl]Cl([PtCl(tpy)teg]Cl), by a series of biological nitrogen donor nucleophiles, viz.
pyrazole (Pz), triazole (Tz), imidazole (Im), 1-methylimidazole (MIm) and 1,2-dimethylimidazole
(DIm) under pseudo first-order conditions as a function of concentration and temperature in methanol
using UV/Visible spectrophotometry were investigated. The analysis of kinetic trend on the candidate
complexes show that only the first carbon-oxygen pendant bond plays a crucial role in regulating the
electron density donated by the polyethylenegycoxyl fragment. This is reflected in the insignificant
change in the reactivity as the polyethyleneglycoxyl chain increases. The obtained kinetic data are supported by the DFT calculations that reveal a less electrophilic Pt(II) metal centre for complexes bearing
the 40
-substituent. The temperature dependent studies support an associative mode of activation where
bond formation in the transition state is favoured.
