A new polynuclear lanthanum picrate complex [La(pic)(2)(TDTD)(15)(H2O)(3)]. pic (pic = picrate, TDTD = trans-1,4-dithiane-1,4-dioxide) was obtained by reacting hydrated lanthanum picrate and TDTD in water. The compound was characterized by IR spectra and X-ray analysis. It crystallizes in space group P (1) over bar with a = 12.267(2), b = 13.012(3), c = 13.888(3) Angstrom, alpha = 109.34(2), beta = 115.97(3), gamma = 83.93(3)degrees, V = 1878.6(9) Angstrom(3). The crystal structure consists of polymeric chains where the TDTD ligands act as bridges between three neighbouring lanthanum ions which are ten coordinated, the coordination sphere containing two bidentate picrate, three water molecules and three oxygens of the three bridging TDTD ligands. (C) 1998 Elsevier Science S.A. All rights reserved.