Bis-tris propane as a flexible ligand for high-nuclearity complexes

Abstract

a b s t r a c tPolymetallic complexes can be assembled using a wide array of polydentate ligands that give an almost unlimited toolbox to prepare new molecular architectures with fascinating structures and interesting magnetic properties. Bis-tris propane is one such a polydentate ligand that has been used to prepare homo-(3d or 4f) and heterometallic (3d/3d 0 or 3d/4f) complexes, ranging from simple complexes such as {Ni 4 } to spectacular 3d/3d 0 {Cu 8 Zn 8 } or {Mn 18 Cu 6 } complexes. It shows a flexibility in binding mode, utilizing up to six of its potential ligand donor atoms and displaying multiple levels of deprotonation, able to bridge up to six metal ions. The ligand has a particular affinity for binding 3d ions such as Cu(II) or Co (III) in heterometallic syntheses and this can provide a flexible structure-directing effect. This concept has been exploited to prepare new heterometallic 3d/3d 0 complexes that display interesting levels of complexity; 3d/4f complexes such as {Cu 3 Tb 2 } that show single-molecule magnet behavior where superexchange interactions quench quantum tunneling of the magnetization, or {Co 3 Gd 3 } where the magnetocaloric properties arise by using Bis-tris propane to separate the Gd(III) ions and weaken Gd (III). . .Gd(III) interactions.

Magnetic Properties of a Family of [MnIII4LnIII4] Wheel Complexes: An Experimental and Theoretical Study

“…32−35 Using H 6 L, both serendipitous assembly and directed synthesis were employed to synthesize novel compounds, with the most spectacular example being a [Mn 18 Cu 6 ] complex built in a stepwise fashion, starting from a monomeric precursor complex of Cu(II) with H 6 L. 33 Regardless of the approach, H 6 L has a tendency to encapsulate one 3d TM ion in the coordination pocket defined by the propane-1,3-diyldiimino backbone, leaving the flexible hydroxymethyl arms to link to other metal ions and increase the nuclearity of the final complex. 36 A recent example showed how this ligand can be used to synthesize [Ln 2 Cu 3 ] complexes (Ln = Gd, Tb, Dy, Ho, or Er) displaying slow relaxation of the magnetization, which could be tuned by varying the auxiliary anionic ligands present. 37 In this Article, we report the synthesis and characterization of a family of octanuclear, wheel-shaped 3d-4f complexes (NMe 4 ) 3 [Mn 4 Ln 4 (H 2 L) 3 (H 3 L)(NO 3 ) 12 ], for the early members of the lanthanide series [Ln = La (1), Ce (2), Pr (3), Nd (4)].…”

“…In previous work, we have shown how the ligand 1,3-bis­(tris­(hydroxymethyl)­methylamino)­propane (H 6 L, Scheme ) can be used to build up polynuclear assemblies of 3d TM ions. − Using H 6 L, both serendipitous assembly and directed synthesis were employed to synthesize novel compounds, with the most spectacular example being a [Mn 18 Cu 6 ] complex built in a stepwise fashion, starting from a monomeric precursor complex of Cu­(II) with H 6 L . Regardless of the approach, H 6 L has a tendency to encapsulate one 3d TM ion in the coordination pocket defined by the propane-1,3-diyldiimino backbone, leaving the flexible hydroxymethyl arms to link to other metal ions and increase the nuclearity of the final complex . A recent example showed how this ligand can be used to synthesize [Ln 2 Cu 3 ] complexes (Ln = Gd, Tb, Dy, Ho, or Er) displaying slow relaxation of the magnetization, which could be tuned by varying the auxiliary anionic ligands present .…”

Cobalt and zinc halide complexes of 4-chloro and 4-methylaniline: Syntheses, structures and magnetic behavior

“…1,2,3 Extensive work has been done 1) Present address: Dept. of Chemistry, University of Virginia, 409 McCormick Road, Charlottesville, VA 22904 USA recently, especially in the study of transition metal and lanthanide complexes, as a result of the discovery of single molecule, 4,5,6,7,8 single chain, 9,10,11 and single ion magnets. 12,13,14,15 Recent publications have demonstrated the breadth of interest in studies of molecular magnetic materials employing a wide variety of transition metal and lanthanoid ions.…”

“…The dotted lines and dashed lines are fits using the 1D chain model and 2D rectangle lattice model, respectively. Considering the hydrogen bonding first, there are differences between the metal chloride compounds (1,2,5,6) and the metal bromide compounds (3,4,7,8) CoCl2, 36 and CdI2. 40a However, when the ML2X2 complex is square planar, the phenyl rings orient themselves on opposite sides of the coordination plane and a different type of chain structure is formed where the halide ions exhibit short contacts to two different adjacent molecules.…”

Binding Features of {M(3d)(cbdc)2} Blocks (M(3d)=VIVO, CuII; cbdc2–=Dianion of Cyclobutane‐1,1‐Dicarboxylic Acid) in Formation of Heterometallic Structures with d‐Metal Cations

“…One of the intensively developing and promising areas of modern coordination chemistry is the directed design of compounds containing atoms of two transition metals of different nature (for example, 3d‐3d′ or 3d‐4d) bound by bridging organic ligands. The simultaneous presence of heterometallic centers in one coordination compound not only leads to an interesting topology of the resulting structures and supramolecular assemblies but also causes them to possess practically important properties, such as magnetism and catalytic activity . Compounds with V IV or Cu II containing one unpaired electron ( S = 1 / 2 ) as one of the metal centers can become interesting objects for studying spin‐spin exchange interactions, since V IV or Cu II complexes are detected by EPR spectroscopy; this allows one to register even weak exchange interactions between paramagnetic ions.…”