EXPERIMENTAL PT-PT PARTIAL STRUCTURE FACTORS OF PLATINUM PYRIMIDINE GREENS BY AWAXS. R. Serimaa, V. Eteläniemi, and M. Torkkeli, Department of Physics, P.O. Box 9, University of Helsinki FIN--00014, Finland; T. Laitalainen, J. Pitkänen, Department of Chemistry, P.O. Box 55, FIN--00014 University of Helsinki, Finland

The extraction of partial structure factors from anomalous x-ray scattering (AWAXS) data is an ill-conditioned problem, the statistical errors in the data seriously reducing the quality of the PSFs. An iterative way to apply the Tikhonov regularization method for solving partial structure factors (PSFs) from AWAXS data is presented [1].

The method is applied for solving the Pt--Pt PSF of platinum pyrimidine greens [2]. The materials, which are of interest due to their anticancer activity [3], contain several atomic species but only the absorption edges of Pt are accessible. Several Pt-greens [2], synthesized by varying ligand structures and reaction conditions, were studied by the AWAXS method. The results, which indicated that the major Pt-structures are mono- and dinuclear, are in contradiction with the widely accepted polymeric Pt-chain model. Studies of Pt-uridine green showed that the Pt-nuclearity can be varied by tuning the reaction conditions.

[1] R. Serimaa, V. Eteläniemi, O. Serimaa, A. Bienenstock and T. Laitalainen. J. Appl. Cryst. in press.

[2] T. Laitalainen, R. Serimaa, S. Vahvaselkä and A. Reunanen. Inorg. Chim. Acta, in press.

R. Serimaa, S. Vahvaselkä, T. Laitalainen and T. Paakkari. J. Am. Chem. Soc. 115 (1993) 10036.

[3] T. Okada, T. Shimura, H. Okuno. Chem. Pharm. Bull. 40 (1992) 264.