Mono-, di-, tri-, and tetranuclear compounds of nickel(II) of formula [Ni(dppn)3](NCS)2 0.5dppn (1), [{Ni- ( d p p n ) ( N C S ) } 2 ( μ - d p p n ) ( μ - N C S ) ] N C S ( 2 ) , [Ni3(dppn)2(N3)2(μ-dppn)2(μ-N3)2](ClO4)2 CH3CH2OH 2H2O (3), and [Ni4(μ-dppn)4(μ-N3)4]Cl4 5H2O (4) [dppn = 3,6-bis(2'- pyridyl)pyridazine] have been prepared and their structures determined by single crystal X-ray diffraction. Compound 1 is made up of mononuclear tris-chelated [Ni(dppn)3]2+ units, thiocyanate counterions, and dppn molecules of crystallization. 2 contains cationic dinuclear units, the six coordination around each metal center being achieved with a pyridazine-dppn and one end-on thiocyanate nitrogen as bridges, a didentate dppn ligand and a terminally bound N-thiocyanate. The electroneutrality in 2 is reached by free thiocyanato anions. 3 contains bent trinuclear cationic units where all nickel(II) ions exhibit a NiN6 chromophore with two bridging bis-didentate dppn and two end-on azide groups connecting the metal centers. Didentate dppn and monodentate azide ligands complete the six coordination at the peripheral nickel(II) ions. The charge in 3 is counterbalanced by perchlorate anions and ethanol and water molecules of crystallization are also present. 4 exhibits a [2 × 2] grid-type of nickel(II) ions where each pair of metal atoms are connected across a pyridazine-dppn fragment and one end-on azido group. Free chloride anions neutralize the positive charge of the grid and water molecules of crystallization are also present. Cryomagnetic susceptibility measurements on crushed crystals of 1-4, in the temperature range 1.9- 300 K, reveal the occurrence of a Curie law for 1 and overall ferromagnetic behavior for 2-4 [J = +4.52(2) (2), +1.32(1) (3), and +10.50(2) and +9.10(2) cm-1 (4)]. The dominant ferromagnetic contribution across the single end-on thiocyanato (2) or azido bridges (3 and 4) versus the antiferromagnetic one through the pyridazine (2-4) is at the origin of this behavior. The values of the intramolecular ferromagnetic interactions in 3 and 4 were substantiated by DFT-type calculations. No ac signals were observed for 2-4 either in the lack of or under nonzero applied dc fields.
From mononuclear compounds to [2 × 2] metallogrids: Ferromagnetically coupled systems built by Nickel(II) and 3,6-Bis(2'- pyridyl)pyridazine (dppn)
De Munno G.
;Bruno R.;Marino N.;
2020-01-01
Abstract
Mono-, di-, tri-, and tetranuclear compounds of nickel(II) of formula [Ni(dppn)3](NCS)2 0.5dppn (1), [{Ni- ( d p p n ) ( N C S ) } 2 ( μ - d p p n ) ( μ - N C S ) ] N C S ( 2 ) , [Ni3(dppn)2(N3)2(μ-dppn)2(μ-N3)2](ClO4)2 CH3CH2OH 2H2O (3), and [Ni4(μ-dppn)4(μ-N3)4]Cl4 5H2O (4) [dppn = 3,6-bis(2'- pyridyl)pyridazine] have been prepared and their structures determined by single crystal X-ray diffraction. Compound 1 is made up of mononuclear tris-chelated [Ni(dppn)3]2+ units, thiocyanate counterions, and dppn molecules of crystallization. 2 contains cationic dinuclear units, the six coordination around each metal center being achieved with a pyridazine-dppn and one end-on thiocyanate nitrogen as bridges, a didentate dppn ligand and a terminally bound N-thiocyanate. The electroneutrality in 2 is reached by free thiocyanato anions. 3 contains bent trinuclear cationic units where all nickel(II) ions exhibit a NiN6 chromophore with two bridging bis-didentate dppn and two end-on azide groups connecting the metal centers. Didentate dppn and monodentate azide ligands complete the six coordination at the peripheral nickel(II) ions. The charge in 3 is counterbalanced by perchlorate anions and ethanol and water molecules of crystallization are also present. 4 exhibits a [2 × 2] grid-type of nickel(II) ions where each pair of metal atoms are connected across a pyridazine-dppn fragment and one end-on azido group. Free chloride anions neutralize the positive charge of the grid and water molecules of crystallization are also present. Cryomagnetic susceptibility measurements on crushed crystals of 1-4, in the temperature range 1.9- 300 K, reveal the occurrence of a Curie law for 1 and overall ferromagnetic behavior for 2-4 [J = +4.52(2) (2), +1.32(1) (3), and +10.50(2) and +9.10(2) cm-1 (4)]. The dominant ferromagnetic contribution across the single end-on thiocyanato (2) or azido bridges (3 and 4) versus the antiferromagnetic one through the pyridazine (2-4) is at the origin of this behavior. The values of the intramolecular ferromagnetic interactions in 3 and 4 were substantiated by DFT-type calculations. No ac signals were observed for 2-4 either in the lack of or under nonzero applied dc fields.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
