Synthesis and Characterization of Nickel(II) Complexes of Nitrogen based Ligands of Type N,N,N′,N′-tetrakis(2-Pyridylmethyl)alkanediamine

Hexadentate ligand of the type N,N,N′,N′-tetrakis(2-pyridylmethyl)alkanediamine (where alkane is butane (L1), hexane (L2) and octane (L3) reacted with Ni(ClO4)2·6H2O (stoichiometry 1:1) in alcoholic solutions yielding mononuclear complexes of the type [Ni(L)](ClO4)2·xH2O. The ligand L1 reacted with Ni(ClO4)2·6H2O in ethanol medium to give a violet powder of [Ni(L1)](ClO4)2·3H2O. The other mononuclear nickel(II) complexes using L2 and L3 were synthesized in methanol solution to give violet powders of [Ni(L2)](ClO4)2·2H2O and [Ni(L3)](ClO4)2·2H2O, respectively. All the three complexes were characterized by IR and elemental analysis. The X-ray crystallographic results for the purple crystals of [Ni(L1)](ClO4)2·3H2O shows the octahedral geometry on the Ni(II) ions together with the tetrahedral perchlorate anions separated from the [Ni(L1)]2+ cation. The crystal structure data show monoclinic space group P 21/c; a = 17.1748(10), b = 9.8273(6), c = 17.8146(10) Å; α = 90º, β = 95.0200(10)º, γ = 90º; V = 2995.2(3) Å3 , Z = 4.

Kinetic Versus Thermodynamic Metalation Enables Synthesis of Isostructural Homo- and Heterometallic Trinuclear Clusters

Temperature-dependent metalation of the new hexadentate ligand (tris(5-(pyridin-2-yl)-1<i>H</i>-pyrrol-2-yl)methane; H₃TPM) enables the selective synthesis of both mononuclear (<i>i.e. </i>Na(THF)₄[Fe(TPM)], kinetic product) and trinuclear (<i>i.e.</i> Fe₃(TPM)₂, thermodynamic product) complexes. Exposure of Na(THF)₄[Fe(TPM)] to FeCl₂ or ZnCl₂ triggers cluster expansion to generate homo- or heterometallic trinuclear complexes, respectively. The developed approach enables systematic variation of ion content in isostructural metal clusters via programmed assembly.

Kinetic Versus Thermodynamic Metalation Enables Synthesis of Isostructural Homo- and Heterometallic Trinuclear Clusters

Temperature-dependent metalation of the new hexadentate ligand (tris(5-(pyridin-2-yl)-1<i>H</i>-pyrrol-2-yl)methane; H₃TPM) enables the selective synthesis of both mononuclear (<i>i.e. </i>Na(THF)₄[Fe(TPM)], kinetic product) and trinuclear (<i>i.e.</i> Fe₃(TPM)₂, thermodynamic product) complexes. Exposure of Na(THF)₄[Fe(TPM)] to FeCl₂ or ZnCl₂ triggers cluster expansion to generate homo- or heterometallic trinuclear complexes, respectively. The developed approach enables systematic variation of ion content in isostructural metal clusters via programmed assembly.

Transition-metal(ii) complexes with a tripodal hexadentate ligand, 1,1,1-tris[2-aza-3-(imidazol-4-yl)prop-2-enyl]ethane, exhibiting incomplete total or absolute spontaneous resolution

Crystal structures and solid-state CD spectra of the compounds, [M(H3L)]Cl(ClO4) (M = Mn, Fe, Co, Ni and Zn) were examined.

Syntheses, Structures, and Characteristics of Three Metal Complexes Constructed Using Hexacarboxylic Acid

In this study, three new 3D coordination polymers (CPs), {[Cd3(L)(H2O)6]·H2O}n (1), {[Cu1.5(L)0.5(bimb)1.5]·5H2O·DMF}n (2), and {[Mn1.5(H3L)(bibp)0.5(H2O)2]·3H2O}n (3) (bimb= 1,3-bis(imidazol-1-yl)benzene, bibp= 1,4-bis((4-imidazol-1-yl)benzyl)piperazine), were prepared under solvothermal or hydrothermal conditions based on a hexadentate ligand (1,3,5-triazine-2,4,6-triamine hexa-acetic acid (H6L)). Structural elucidations were carried out by IR spectra along with single-crystal X-ray diffraction analysis, while thermogravimetric analysis (TGA) (dynamic and isothermal) and XRD techniques were used for property evaluations of the polymers. Furthermore, the fluorescence properties and detection of the Fe3+ ions in 1 were tested at room temperature, and the electrochemical behavior of 2 is also stated in this article.

Spin Cross-Over (SCO) Complex Based on Unsymmetrical Functionalized Triazacyclononane Ligand: Structural Characterization and Magnetic Properties

The unsymmetrical ligand 1-(2-aminophenyl)-4,7-bis(pyridin-2-ylmethyl)-1,4,7-triazacyclononane (L6) has been prepared and characterized by NMR spectroscopy. The L6 ligand is based on the triazamacrocycle (tacn) ring that is functionalized by two flexible 2-pyridylmethyl and one rigid 2-aminophenyl groups. Reaction of this ligand with Fe(ClO4)2·xH2O led to the complex [Fe(L6)](ClO4)2 (1), which was characterized as the first Fe(II) complex based on the unsymmetrical N-functionalized tacn ligand. The crystal structure revealed a discrete monomeric [FeL6]2+ entity in which the unsymmetrical N-functionalized triazacyclononane molecule (L6) acts as hexadentate ligand. As observed in the few parent examples that are based on the symmetrical N-functionalized tacn ligands, the triazacyclononane ring is facially coordinated and the N-donor atoms of the three functional groups (two pyridine and one aniline groups) are disposed in the same side of the tacn ring, leading to a distorted FeN6 environment. The magnetic studies of 1 revealed the presence of an incomplete spin crossover (SCO) transition above 425 K, whose progress would be prevented by a very exothermic thermal decomposition at ca. 472 K, as shown by thermogravimetric and DSC measurements.