Nine lanthanide complexes with 3,12-bis(carboxymethyl)-6,9-dioxa-3,12-diazatetradecanedioic acid (H(4)egta): [M'(H2O)(n)] [M(egta)(H2O)](2).n H2O (M': Ca, Sr; M: La, Ce, Pr, Dy, Ho, Er) have been prepared and characterized by using their infrared absorption and Raman spectra, magnetic susceptibility and thermal analyses. The results of Raman spectra (600-200 cm(-1)) suggest that these complexes are of two types: the first includes La, Ce, and Pr complexes, and the second Dy, Ho and Er complexes. The crystal and molecular structures of [Ca(H2O)(2)] [La(egta)(H2O)](2).8H(2)O (1), [Ca(H2O)(2)] [Ce(egta)(H2O)](2).6H(2)O (2), [Sr(H2O)(3)] [Dy(egta)(H2O)](2).7H(2)O (3), and [Sr(H2O)(3)] [Ho(egta)(H2O)](2).7H(2)O (4) have been determined by a single-crystal X-ray diffraction method. The crystals of complexes (1) and (2) are iso-morphous to each other: monoclinic, space group P2(1)/c, Z = 2. The central lanthanide metal atom is 10-coordinated, in a distorted bicapped square antiprism geometry, to two nitrogen and six oxygen atoms of egta(4-), a water molecule, and a carboxyl oxygen atom from an adjacent complex ion. The Ca2+ is at the center of the octahedral geometry and ligated by four carboxyl oxygen atoms and two water molecules. Complexes (3) and (4) are iso-morphous to each other: monoclinic, space group P2(1)/n, Z = 4. The central lanthanide metal atom is nine-coordinated, in a distorted tricapped-trigonal prism geometry, to two nitrogen and six oxygen atoms of egta4-, and to a water molecule which bridges to the Sr2+ ion. Two carboxyl groups of [M(egta)(H2O)](-) (M: Dy, Ho) complex ion bridge to the single Sr2+ ion. In addition, the Sr2+ is coordinated by three non-bridged water molecules, and then the Sr2+ is coordinated by nine atoms. A relationship has been found between the average M-N, M-O(ether) and M-O(carboxylate) bond lengths and Shannon's metal crystal radii for a series of complexes shown as [M'(H2O)(n)][M(egta)(H2O)](2).nH(2)O (M': Ca, Sr; M: La, Ce, Nd, Dy, Ho, Er). (C) 2003 Elsevier B.V. All nights reserved..