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Title: Kinetics of substitution of aqua ligands from cis-diaqua (ethylenediamine)platinum(II) perchlorate by guanosine in aqueous medium
Authors: Sengupta, Partha S
Sinha, Ramanath
Bera, Sujit K
De, Gauri S
Issue Date: Apr-2002
Publisher: NISCAIR-CSIR, India
Abstract: The kinetics of the interaction of guanosine with cis-[Pt(en)(H2O)2]2+ + have been studied spectrophotometrically as a Function of [Pt(en)(H2O)22+], [guanosine] and temperature at pH 4.0 where the substrate complex exists predominantly as the diaqua species. Base stacking and metal induced macrochelate formation of guanosine plays a vital role in determining the concentration limit of guanosine during kinetics. Substitution occurs in two consecutive steps; both dependent on the guanosine concentration. Activation parameters for both steps have been calculated. The low ∆H1# (36.28 ± 0.5 kJ mol-1) and large negative values of ∆S1#(- 125.3 ± 1.5 J K-1 mol-1) as well as ∆H2# (36.03 ± 0.6 kJ mol-1) and ∆S2# (-149.2 ± 1.9 J K-1 mol-1) indicate associative modes of activation for both the ligand substitution processes ill the two consecutive steps.
Page(s): 712-717
ISSN: 0975-0975(Online); 0376-4710(Print)
Appears in Collections: IJC-A Vol.41A(04) [April 2002]

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