title: Cis-trans isomeric and polymorphic effects on the magnetic properties of water-bridged copper coordination chains.
abstract: The synthesis and magnetic characterization of vanillin-based Cu(II) mononuclear complexes of formula [Cu(van)(2)(H(2)O)(2)](H(2)O)(x) (van = vanillinate; x = 0, compound 1; x = 2, compounds 2 and 3) were performed. Despite the presence of very similar [Cu(van)(2)(H(2)O)(2)] moieties, the crystal structures exhibit distinct Cu···Cu contacts and display three different through-H-bond exchange-coupling pathways. As a result of the relative positions of the water molecules, the experimental (MAGSUS) exchange-coupling constants are dissimilar, i.e., J(1) = -3.0 cm(-1) (the data have been fitted to the Bleaney-Bowers equation considering a dimer; 2J = -6.0 cm(-1)), J(2) = -4.0 cm(-1) (the data have been fitted to the Bonner-Fischer equation for a chain of monomeric copper(II) units), whereas compound 3 is paramagnetic. Subsequently, the theoretical density functional theory (DFT) and wave function theory-based (DDCI) calculations were carried out to better understand the role of the water molecule as a mediator of the magnetic coupling. The use of localized orbitals allows one to elucidate the role of the H-bonds in generating exchange interactions. Since the exchange-coupling constants are strongly dependent on the mechanisms selectively introduced, the role of the H-bond is demonstrated.
authors.affiliation: Fakulteta za kemijo in kemijsko tehnologijo, Univerza v Ljubljani, Aškerčeva c. 5, 1000 Ljubljana, Slovenia. Bojan.Kozlevcar@fkkt.uni-lj.si
authors.forename: Bojan
authors.initials: B
authors.lastname: Kozlevčar
authors.forename: Nives
authors.initials: N
authors.lastname: Kitanovski
authors.forename: Zvonko
authors.initials: Z
authors.lastname: Jagličić
authors.forename: Nuno A G
authors.initials: NA
authors.lastname: Bandeira
authors.forename: Vincent
authors.initials: V
authors.lastname: Robert
authors.forename: Boris
authors.initials: B
authors.lastname: Le Guennic
authors.forename: Patrick
authors.initials: P
authors.lastname: Gamez