A novel series of copper(II) complexes of formula [Cu(tren)(mpda)](ClO4)2.1/2H2O (1), [Cu2(tren)2(mpda)](ClO4)4. 2H2O (2), and [Cu2(tren)2(ppda)](ClO4)4.2H2O (3) containing the tetradentate tris(2-aminoethyl)amine(tren) terminal ligand and the potentially bridging 1,n-phenylenediamine [n = 3(mpda) and 4 (ppda)] ligand have been prepared and spectroscopically characterized. X-ray diffraction on single crystals of 1 and 3 show the presence of mono- (1) and dinuclear (3) copper(II) units where the mpda (1) and ppda (3) ligands adopt terminal monodentate (1) and bridging bis(monodentate) (3) coordination modes toward [Cu(tren)]2+ cations with an overall non-planar, orthogonal disposition of the phenylene group and the N–Cu–N threefold axis of the trigonal bipyramid of each copper(II) ion [values of the Cu–N–C–C torsion angle (f) in the range of 50.8(3)–79.2(2) (1) and 80.9(2)–86.5(2)° (3)]. Variable-temperature magnetic susceptibility measurements on the dinuclear complexes 2 and 3 show the occurrence of moderate ferromagnetic (J = +8.3 cm1, 2) and strong antiferromagnetic (J = -51.4 cm1, 3) couplings between the two copper(II) ions across the meta- and para-phenylenediamine bridges, leading to S = 1 (2) and S = 0 (3) ground spin states [H = -JS1.S2 with S1 = S2 = SCu = 1/2]. Density functional theory (DFT) calculations on the triplet (2) and broken-symmetry (BS) singlet (3) ground spin states, support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction through the predominantly p-type orbital pathway of the 1,n-phenylenediamine bridge. Finally, a new magnetostructural correlation between the magnitude of the magnetic coupling (J) and the Cu–N–C–C torsion angle (f) has been found which reveals the role of s- versus p-type orbital pathways in the modulation of the magnetic coupling for m- and p-phenylenediamine-bridged dicopper(II) complexes.
Self-assembled one- and two-dimensional networks based on NH2Me2[ReX5(DMF)] (X = Cl and Br) species: polymorphism and supramolecular isomerism in Re(IV) compounds
DE MUNNO, Giovanni;
2010-01-01
Abstract
A novel series of copper(II) complexes of formula [Cu(tren)(mpda)](ClO4)2.1/2H2O (1), [Cu2(tren)2(mpda)](ClO4)4. 2H2O (2), and [Cu2(tren)2(ppda)](ClO4)4.2H2O (3) containing the tetradentate tris(2-aminoethyl)amine(tren) terminal ligand and the potentially bridging 1,n-phenylenediamine [n = 3(mpda) and 4 (ppda)] ligand have been prepared and spectroscopically characterized. X-ray diffraction on single crystals of 1 and 3 show the presence of mono- (1) and dinuclear (3) copper(II) units where the mpda (1) and ppda (3) ligands adopt terminal monodentate (1) and bridging bis(monodentate) (3) coordination modes toward [Cu(tren)]2+ cations with an overall non-planar, orthogonal disposition of the phenylene group and the N–Cu–N threefold axis of the trigonal bipyramid of each copper(II) ion [values of the Cu–N–C–C torsion angle (f) in the range of 50.8(3)–79.2(2) (1) and 80.9(2)–86.5(2)° (3)]. Variable-temperature magnetic susceptibility measurements on the dinuclear complexes 2 and 3 show the occurrence of moderate ferromagnetic (J = +8.3 cm1, 2) and strong antiferromagnetic (J = -51.4 cm1, 3) couplings between the two copper(II) ions across the meta- and para-phenylenediamine bridges, leading to S = 1 (2) and S = 0 (3) ground spin states [H = -JS1.S2 with S1 = S2 = SCu = 1/2]. Density functional theory (DFT) calculations on the triplet (2) and broken-symmetry (BS) singlet (3) ground spin states, support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction through the predominantly p-type orbital pathway of the 1,n-phenylenediamine bridge. Finally, a new magnetostructural correlation between the magnitude of the magnetic coupling (J) and the Cu–N–C–C torsion angle (f) has been found which reveals the role of s- versus p-type orbital pathways in the modulation of the magnetic coupling for m- and p-phenylenediamine-bridged dicopper(II) complexes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
