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Asymmetric azido-copper(II) bridges: Ferro- or antiferromagnetic? Experimental and theoretical magneto-structural studies

Abstract : Reaction of NaN3 with the [CuII(tn)]2+ ion (tn = 1,3-diaminopropane) in basic aqueous solution yields the azido-bridged complex of formula [Cu2(tn)2(N3)4] (1), which is characterized by X-ray crystallography. The structure of 1 is made up of dinuclear neutral complexes, of formula [Cu2(tn) 2(N3)4], resulting from the assembling of two mononuclear units through two equivalent end-on azide bridges connecting asymmetrically two Cu(tn)(N3)2 entities. These dinuclear units are connected through two asymmetric end-to-end N3 bridges to form a chain of dimers. Magnetic measurements for compound 1 show weak antiferromagnetic exchange interactions between the Cu(II) ions. The magnetic data were modeled using the susceptibility expression derived for an alternating AF S = 1/2 chain. A very satisfactory fit over the whole temperature range was obtained with g = 2.1438(4), J1 = -3.71(2) cm-1, and J2 = -3.10(2) cm-1 (J1 and J2 are the singlet-triplet separations). This magnetic behavior differs from those observed for similar examples which were reported as having alternating ferro- and antiferromagnetic exchange interactions; thus, DFT calculations were done to understand the nature of the magnetic coupling in such asymmetric end-on and end-to-end N3 bridges. Theoretical results show that the double asymmetric end-on bridges produce antiferromagnetic coupling while the end-to-end ones can present ferro- or antiferromagnetic coupling depending on the copper coordination sphere. © 2005 American Chemical Society.
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Submitted on : Wednesday, April 11, 2018 - 1:43:13 PM
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Smail Triki, C.J. Gómez-García, E. Ruiz, J. Sala-Pala. Asymmetric azido-copper(II) bridges: Ferro- or antiferromagnetic? Experimental and theoretical magneto-structural studies. Inorganic Chemistry, American Chemical Society, 2005, 44 (15), pp.5501-5508. ⟨10.1021/ic0504543⟩. ⟨hal-01763760⟩

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