title: Synthesis, crystal structures and magnetic properties of bis(μ-dialkoxo)-bridged linear trinuclear copper(II) complexes with aminoalcohol ligands: a theoretical/experimental magneto-structural study.
abstract: The bis(μ-dialkoxo)-bridged trinuclear copper(II) complexes [Cu(3)(ap)(4)(ClO(4))(2)EtOH] (1), [Cu(3)(ap)(4)(NO(3))(2)] (2), [Cu(3)(ap)(4)Br(2)] (3) and [Cu(3)(ae)(4)(NO(3))(2)] (4) (ae = 2-aminoethanolato and ap = 3-aminopropanolato) have been synthesised via self-assembly from chelating aminoalcohol ligands with the corresponding copper(II) salts. The complexes are characterised by single-crystal X-ray diffraction analyses and variable temperature magnetic measurements. The crystal structures of complexes 1-4 consist of slightly bent linear or linear trinuclear [Cu(3)(aa)(4)](2+) (aa = aminoalcoholato) units to which the perchlorate, nitrate or bromide anions are weakly coordinated. The adjacent trinuclear units of 1-4 are connected together by hydrogen bonds and bridging nitrate or bromide anions resulting in the formation of 2D layers. Magnetic studies of 1, 2 and 4 show that J values vary from -379 to +36.0 cm(-1) as the Cu-O-Cu angle (θ) and the out-of-plane shift of the carbon atom of the bridging alkoxo group (τ) vary from 103.7 to 94.4° and from 0.9 to 35.5°, respectively. Magnetic exchange coupling constants calculated by DFT methods are of the same nature and magnitude as the experimental ones. For complexes 1, 2 and 4, which have complementarity effects between the θ and τ angles (small θ values are associated with large τ values and vice versa), an almost linear relationship between the calculated J values with θ angles could be established, thus supporting that the θ and τ angles are the two key structural factors that determine the magnetic exchange coupling for such a type of compounds. Complex 3 does not obey this linear correlation because of the existence of counter-complementarity effects between these angles (small θ values are associated with small τ values and vice versa). It is of interest that the theoretical calculations for the magnetic exchange interaction between next-nearest neighbours indicate that the usual approximation in experimental studies of neglecting the magnetic coupling between the next-nearest neighbours in linear trinuclear complexes could lead to considerable errors, especially when J(1) and J(2) are of the same order of magnitude as J(3).
authors.affiliation: Department of Chemistry, University of Jyväskylä, Jyväskylä, Finland. petri.seppala@jyu.fi
authors.forename: Petri
authors.initials: P
authors.lastname: Seppälä
authors.forename: Enrique
authors.initials: E
authors.lastname: Colacio
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Mota
authors.forename: Reijo
authors.initials: R
authors.lastname: Sillanpää
mesh_terms: D000605:Amino Alcohols / Q000737:chemistry*; D001965:Bromides / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D003460:Crystallization; D008024:Ligands; D008280:Magnetics; D015394:Molecular Structure; D009566:Nitrates / Q000737:chemistry; D010472:Perchlorates / Q000737:chemistry
chemical_list: D000605:Amino Alcohols; D001965:Bromides; D008024:Ligands; D009566:Nitrates; D010472:Perchlorates; D003300:Copper