|
The palladium(Ⅱ) complexes(where, [Pd(L)2X2], L=isoxazole(isox), 3,5-dimethylisoxazole(3,5-diMeisox), 3-methyl, 5-phenylisoxazole(3-Me, 5-Phisox), and 4-amino, 3,5-dimethylisoxazole(4-ADI); X=Cl, Br] with isoxazole and its derivatives are investigated on antitumor activity by EHMO calculation. It is found that the net charge of the two halogen atoms in trans-isomers are greater than those in cis-ones, indicating that ionic character of Pd-X bond in trans-isomers is greater than that of cis-ones, and so dissociation of Cl- ion is easier than that of Br- ion in aqueous solution in body. Furthermore, it is found that the σMO energy of Pd(dx2-y2)-X(px) bond (Eσ(Pd-X)) is higher than that of Pd(dx2-y2)-N(px) bond (Eσ(Pd-N)) without exception, about all the complexes, and also the Eσ(Pd-X) of trans-isomers is higher than that of cis-isomers. From the above facts, the degree of dissociation in Pd-X bond would be related to antitumor activity. In fact, the linear equation of correlation coefficient 0.96 is fairly established between ΔEσ(N-X)(Eσ(Pd-N)－Eσ(Pd-X)) and inhibitory activity coefficient, logIA.
|