Syntheses, structures, and magnetic properties of one mononuclear inclusion compound [Cu(II)L1 subset of( H2O)] (1) and three tetrametal systems of the composition [{(CuL1)-L-II}(2) {(CuLMII)-L-II-M-1(H2O)(3)}](ClO4)(2) (M = Cu (2), M = Co (3), M = Mn (4)) derived from the hexadentate Schiff base compartmental ligand N,N'-ethylenebis(3-ethoxysalicylaldimine) (H2L1) have been described. Compounds 1 and 2 crystallize in orthorhombic Pbcn and monoclinic P2(1)/c systems, respectively, and the space group of the isomorphous compounds 3 and 4 is monoclinic C2/c. The water molecule in 1 is encapsulated in the vacant O-4 compartment because of the hydrogen bonding interactions with the ether and phenolate oxygens, resulting in the formation of an inclusion product. The structures of 2-4 consist of the [(CuLMII)-L-II-M-1(H2O)(3)](2+) cation and two mononuclear [(CuL1)-L-II] moieties. In the dinuclear [(CuLMII)-L-II-M-1(H2O)(3)](2+) cation, the metal centers are doubly bridged by the two phenolate oxygens. The second metal center, M-II (Cu in 2, Co in 3, and Mn in 4), in the [(CuLMII)-L-II-M-1(H2O)(3)](2+) cation is pentacoordinated by the two phenoxo oxygens and three water molecules. Two of these three coordinated water molecules interact, similar to that in 1, with two mononuclear [(CuL1)-L-II] moieties, resulting in the formation of the tetrametal [{(CuL1)-L-II}(2) {(CuLMII)-L-II-M-1(H2O)(3)}](2+) system that consists of the cocrystallized dinuclear (one) and mononuclear (two) moieties. Evidently, the cocrystallization observed in 2-4 is related to the tendency of a water molecule to be encapsulated in the vacant O-4 compartment of the mononuclear [(CuL1)-L-II] species. In the case of 2, there are two independent [(CuLCuII)-L-II-Cu-1((HO)-O-2)(3)](2+) units. The tau ((beta - alpha)/60, where, and R are the largest and second largest bond angles, respectively) values in the pentacoordinated environment of the two copper(II) centers in 2 are 0.04 and 0.37, indicating almost ideal and appreciably distorted square pyramidal geometry, respectively. In contrast, the Y values (0.54 for 3 and 0.49 for 4) indicate that the coordination geometry around the cobalt(II) and manganese(II) centers in 3 and 4 is intermediate between square pyramidal and trigonal bipyramidal. The variable-temperature (2-300 K) magnetic susceptibilities of compounds 2 - 4 have been measured. The magnetic data have been analyzed in the model of one exchange-coupled dinuclear (CuMII)-M-II moiety and two noninteracting Cu-II centers. In all three cases, the metal ions in the dinuclear core are coupled by a weak antiferromagnetic interaction (J = -17.4 cm(-1), -8 cm(-1), and -14 cm(-1) for 2, 3, and 4, respectively). The observation of a weak interaction has been explained in terms of the structural parameters and symmetry of the magnetic orbitals.