Metal-template Condensation of 1,3-Diamino-2-propanol and Formaldehyde: Synthesis, Crystal Structure, and Magnetic Properties of a New Dinuclear Copper(II) Complex

Abstract

Polynuclear transition metal complexes with relatively strong intramolecular metal-metal interactions have received considerable attention because of their interesting chemical properties and/or potential applications in various fields, such as supramolecular chemistry, catalysts for organic reactions, and materials chemistry.1-11 Especially, dinuclear copper(II) complexes are known to be useful systems for the study of long-distance metal-metal interactions, since the metal ion has only one unpaired electron.Some μ-alkoxo-μ-carboxylato or μ-alkoxo-μ-methoxypurinate double bridge dinuclear copper(II) complexes, such as 2-5 containing two N 2 O 2 or NO 3 donor sets, have been prepared.3-9 It has been revealed that their metal-metal interactions are influenced by various structural factors, such as the Cu-X-Cu (X = bridging atom) bridging angle, coordination geometry, the nature of the donor atoms, ligand structure, and Cu···Cu distance. For example, although 2-4 exhibit antiferromagnetic coupling with J = -78 − -141 cm . 6-9 However, the effects of the structural factors upon the magnetic properties of such complexes are not thoroughly investigated.Metal-template condensation reactions involving amines and formaldehyde have been utilized for the preparation of various types of polyaza macrocyclic or non-macrocyclic complexes containing N-CH 2 -N linkages.10-14 Recently, such reactions have been extended to the preparation of the alkoxo-bridged dinuclear copper(II) complex 6 that exhibits unusually strong antiferromagnetic interactions between the copper(II) ions; 6 can be prepared by the reaction (Eq. (1)) of bis(3-aminopropyl)amine with formaldehyde in the presence of the metal ion. In this work, we examined the metal-directed reaction (Eq. (2)) involving 1,3-diamino-2-propanol and formaldehyde and prepared a new dinuclear, in which two metal centers are bridged by the alkoxo group of L and the acetate ion. Interestingly, 1·H 2 O exhibits relatively strong ferromagnetic coupling between two copper(II). Synthesis, crystal structure, and chemical properties of the complex are reported. ExperimentalMeasurements. Electronic absorption spectra were obtained with an Analytik Jena Specord 200 UV-vis spectrophotometer, infrared spectra with a Genesis II FT-IR spectrometer, and conductance measurements with a Z18 Oyster conductivity/temperature meter. Microanalyses were performed at