Chiral and achiral platinum(II) complexes for potential use as chemotherapeutic agents: crystal and molecular structures of cis-[Pt(L 1 ) 2 ] and [Pt(L 1 )Cl(MPSO)] [HL 1 ؍ N,N-diethyl-NЈbenzoylthiourea]
The complexes [Pt(bipy)L]PF 6 and [Pt(phen)L]PF 6 (HL = N-acyl-NЈ,NЈ-di-n-butylthiourea) showed pronounced self-association in CD 3 CN solution at 25 ЊC according to an equilibrium 2[Pt(diimine)-(L-S,O)] ϩ[{Pt(diimine)(L-S,O)} 2 ] 2ϩ for which association constants, K D , have been estimated from the concentration dependence of the 1 H NMR shifts of these complexes. The values of K D range from 1.8 to 114 Ϫ1 depending on the structure of the diimine as well as the nature of the N-acyl group; the values of the 1,10phenanthroline complexes are generally larger than those for the corresponding 2,2Ј-bipyridine analogues. In general, N-1-naphthoyl-NЈ,NЈ-dibutylthiourea complexes self-associate to a lesser extent than the corresponding N-benzoyl analogues. From the temperature dependence of the K D values, the thermodynamic parameters ∆G, ∆H and ∆S have been estimated. An average ∆(∆G) increment of 2.4 ± 0.4 kJ mol Ϫ1 per aromatic ring of the diimine moiety co-ordinated to the complexes is consistent with energies generally associated with π-π stacking and cation π interactions observed for other systems.
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