Methylene spacer regulated variation in structures and magnetic properties in copper(II) compounds with O, N, O donor Schiff bases

Tetranuclear [Cu4(L1)2(HL1)2(H2O)](ClO4)2·2H2O (1) and binuclear [Cu2(L2)2]·CH3OH (2) compounds are prepared and the molecular structures elucidated on the basis of X-ray crystallography [H2L1 = 2-[(2-hydroxy-ethylimino)-methyl]-6-methoxy-phenol, H2L2 = 2-[(3-hydroxy-propylimino)-methyl]-6-methoxy-phenol]. Compound 1 is made up of the cation [Cu4(L1)2(HL1)2(H2O)2]2+ and two ClO4− anions which are H-bonded to the cation. The four Cu(II) atoms are not crystallographically equivalent, among then two are in tetragonal [CuNO5] geometries and the rest two are in square pyramidal geometries. The asymmetric unit of compound 2 consists of one neutral [Cu2(L2)2] moiety and a methanol molecule. Each copper atom in compound 2 has a four-coordinate square-planar environment. Compound 1 can be described as an open cage with a [Cu4(μ3-Oal)2(μ2-Oph)2]4+ core (al = alkoxido and ph = phenoxido). Variable temperature solid state magnetic studies between 2–300 K were carried out and the data indicate predominant antiferromagnetic exchange interactions and a spin ground state S = 0. The data were fitted with an average J value model, using the spin Hamiltonian H = −Jav(S1·S2 + S3·S4 + S1·S3 + S2·S4). The best fit was obtained with Jav = −99.0 cm−1. The magnetic properties of compound 2 have also been analyzed and the data show a large antiferromagnetic interaction, in agreement with the [Cu2(μ2-Oal)2]2+ core. The best fit of the data was obtained with J = −891 cm−1 (H = −J S1·S2).

Two copper(II) compounds [Cu4(L1)2(HL1)2(H2O)](ClO4)2·2H2O (1) and [Cu2(L2)2]·CH3OH (2) [H2L1 = 2-[(2-hydroxy-ethylimino)-methyl]-6-methoxy-phenol, H2L2 = 2-[(3-Hydroxy-propylimino)-methyl]-6-methoxy-phenol] have been prepared and characterized by elemental analysis, IR and UV–Vis spectroscopy and single crystal X-ray diffraction studies. Compound 1 can be described as an open cage with a [Cu4(μ3-Oal)2(μ2-Oph)2]4+ core (al = alkoxido and ph = phenoxido). The asymmetric unit of compound 2 consists of one neutral [Cu2(L2)2] moiety and a methanol molecule. Variable temperature magnetic studies between 2–300 K indicated predominant antiferromagnetic exchange interactions and a spin ground state S = 0 in compound 1 (Jav = −99.0 cm−1). The magnetic property of compound 2 showed a large antiferromagnetic interaction (J = −891 cm−1) in agreement with the [Cu2(μ2-Oal)2]2+ core.Figure optionsDownload as PowerPoint slide