Structure and conformation of (dibenzyldiaza-18-crown-6)-Nd(III) and Eu(III) thiocyanates: infrared spectroscopic and X-ray crystallographic studies

Dibenzyldiaza-18-crown-6 was utilised as a host to accommodate Nd(III) and Eu(III) metal ions together with thiocyanate as counter ion. The crystallin e complexes formed were studied for their absorption in the infrared region and their crystalline structure by X-ray diffraction. The coordination of the metal ions to the counter ion and also to the donor atoms of the crown ether was clearly seen from the shift of the absorption band of the pure co mpound by up to nearly 15 cm(-1). From these absorption it was found that e ach lanthanide ion was coordinated to six donor atoms (2 N and 4 O) from cr own ether and three donor atoms, N from NCS-. This nine coordination number complex was found to have the stoichiometry of 1:1:3 (crown ether:lanthani de; NCS-). This ratio was further confirmed by X-ray crystallographic metho d. The lanthanide thiocyanate salts existed as an isolated (separate) entit y in the center of the macrocyclic cavity. The three N atoms surrounded the Ln cation in a nearly planar trigonal arrangement with Ln ion being slight ly out of plane. The trigonal plane was perpendicular to and bisects the pl ane of the macrocycle. (C) 1999 Elsevier Science B.V. All rights reserved.