0000000000186376
AUTHOR
Yolanda Rodríguez-martín
Malonate-based copper(II) coordination compounds: Ferromagnetic coupling controlled by dicarboxylates
Studies on structural and magnetic properties of polynuclear transition metal complexes, aimed at understanding the structural and chemical factors governing electronic exchange coupling mediated by multiatom bridging ligands, are of continuing interest to design new molecular materials exhibiting unusual magnetic, optical and electrical properties, bound to their molecular nature. Looking at potentially flexible bridging ligands, the malonate group seems a suitable candidate. The occurrence of two carboxylate groups in the 1,3 positions allows this ligand to adopt simultaneously chelating bidentate and different carboxylato bridging modes (syn–syn, anti–anti and syn–anti trough one or two …
Malonic acid: A multi-modal bridging ligand for new architectures and properties on molecule-based magnets
Abstract In this work, we show how the design of one-, two- and three-dimensional materials can strongly benefit from the use of crystal engineering techniques, which can give rise to structures of different shapes, and how these differences can give rise to different properties. We will focus on the networks constructed by assembling malonate ligands and metal centres. The idea of using malonate (dianion of propanedioic acid, H 2 mal) is that they can give rise to different coordination modes with the metal ions bind. Extended magnetic networks of dimensionalities 1 (1D), 2 (2D) and 3 (3D) can be chemically constructed from malonato-bridged metallic complexes. These coordination polymers b…
Ferromagnetic coupling in the malonato-bridged copper(ii) chains [Cu(Im)2(mal)]nand [Cu(2-MeIm)2(mal)]n(H2mal = malonic acid, Im = imidazole and 2-MeIm = 2-methylimidazole)
Two new malonato-bridged copper(II) complexes of formula [Cu(Im)2(mal)]n (1) and [Cu(2-MeIm)2(mal)]n (2) (Im=imidazole, 2-MeIm=2-methylimidazole and mal=malonate dianion) have been prepared and their structures solved by X-ray diffraction methods. The [Cu(Im)2(mal)] and [Cu(2-MeIm)2(mal)] neutral entities act as monodentate ligands towards the adjacent copper(II) units through one of the two carboxylate groups, the OCO bridge exhibiting an anti-anti conformation. The environment of each copper atom in 1 and 2 is distorted square pyramidal: two carboxylate oxygen atoms from a bidentate malonate and two nitrogen atoms from two imidazole (1) or 2-methylimidazole (2) ligands form the equatorial…
Alternating cationic–anionic layers in the [Mii(H2O)6][Cuii(mal)2(H2O)] complexes linked through hydrogen bonds (M = Mn, Co, Ni, Cu and Zn; H2mal = malonic acid)
The compounds of formula [MII(H2O)6][CuII(mal)2(H2O)2] [M = Mn (1), Co (2), Ni (3), Cu (4), Zn (5) and H2mal = malonic acid] have been prepared and structurally characterised. Each compound adopts a structure where the layers of [Cu(mal)2(H2O)2]2− anions alternate with layers of [M(H2O)6]2+ cations. The layers are linked to each other through hydrogen bonds affording a three-dimensional network. A quasi-Curie law behaviour is observed for the complexes 1–5 in the temperature range 2.0–298 K.
Crystal structure and magnetic properties of the flexible self-assembled two-dimensional square network complex [Cu2(mal)2(H2O)2(4,4′-bpy)] (H2mal=malonic acid and 4,4′-bpy=4,4′-bipyridine)
Abstract The copper(II) complex [Cu 2 (mal) 2 (H 2 O) 2 (4,4′-bpy)] ( 1 ) (H 2 mal=malonic acid and 4,4′-bpy=4,4′-bipyridine) has been prepared and its structure determined by single crystal X-diffraction methods. Compound 1 has a two-dimensional square grid network structure. The square grids are stacked parallel but in a staggered manner on each other along the c -axis, with an interlayer separation of 3.850(1) A. Each layer contains a large cavity of 15.784(1)×15.784(1) A with each edge shared by one malonate group and one 4,4′-bpy ligand and a small planar square of 4.644(1)×4.644(1) A with Cu(II) ions and malonate groups at each corner and side, respectively. Each copper atom is in a d…
Synthesis, crystal structure and magnetic properties of [Cu(bpym)(mal)(H2O)]·6H2O and [Cu2(bpym)(mal)2(H2O)2]·4H2O (bpym=2,2′-bipyrimidine, H2mal=malonic acid)
Abstract Two new mixed-ligand complexes of formula [Cu(bpym)(mal)(H2O)]·6H2O (1) and [Cu2(bpym)(mal)2(H2O)2]·4H2O (2) (bpym=2,2′-bipyrimidine and H2mal=malonic acid) have been synthesised and characterised by X-ray diffraction methods. The crystal structure of 1 consists of mononuclear [Cu(bpym)(mal)(H2O)] units in which the copper atom shows a slightly distorted square-pyramidal environment with two bpym-nitrogen and two malonate-oxygen atoms forming the equatorial plane and a water molecule in the axial position. The structure of 2 is built by centrosymmetric bpym-bridged dinuclear [Cu2(bpym)(mal)2(H2O)2] units, in which the geometry of each Cu(II) ion is similar to that found in 1. Malon…
The flexibility of molecular components as a suitable tool in designing extended magnetic systems
In this work we show how the design of n-dimensional magnetic compounds (nD with n = 1–3) can strongly benefit from the use crystal engineering techniques, which can give rive to structures of different shapes with different properties. We focus on the networks built by assembling the malonato-bridged tetranuclear copper(II) units Cu4(mal)4 (mal2− is the dianion of propanedioic acid, H2mal) through the potentially bridging 2,4′-bipyridine (2,4′-bpy), 4,4′-bipyridine (4,4′-bpy) and pyrazine (pyz). The magneto-structural study of the complexes of formula [Cu4(mal)4(2,4′-bpy)4(H2O)4]·8H2O (1), [Cu4(mal)4(H2O)4(4,4′-bpy)2] (2) (this compound was the subject of a previous report but it is includ…
A new eight-coordinate complex of manganese(II): synthesis, crystal structure, spectroscopy and magnetic properties of [Mn(Hoxam)2(H2O)4] (H2oxam=oxamic acid)
Abstract The crystal structure of an eight-coordinate manganese(II) compound containing oxamato and water molecules as ligands [Mn(Hoxam)2(H2O)4], were H2oxam=oxamic acid, has been determined by X-ray diffraction on single-crystals. The coordinated oxygen atoms are located at the vertices (corners) of a distorted bicapped trigonal antiprism. Hydrogen bonding is responsible for an extended 3D-network. The magnetic susceptibility data of the compound have been investigated. χMT follows the Curie law, at very low temperatures χMT decreases smoothly due to weak intermolecular interactions and/or due to a small zero field splitting of the sextuplet spin state of the Mn(II).
Structural versatility of the malonate ligand as a tool for crystal engineering in the design of molecular magnets
The synthesis of ferro- and ferri-magnetic systems with a tunable Tc and three-dimensional (3-D) ordering from molecular precursors implying transition metal ions is one of the active branches of molecular inorganic chemistry. The nature of the interactions between the transition metal ions (or transition metal ions and radicals) is not so easy to grasp by synthetic chemists working in this field since it may be either electrostatic (orbital) or magnetic (mainly dipolar). Therefore, the systems fulfilling the necessary requirements to present the expected magnetic properties are not so easy to design on paper and realize in the beaker. In this work we show how the design of one-, two- and t…
Crystal structures and magnetic properties of two- and three-dimensional malonato-bridged manganese(ii) complexes
Two new manganese(II) compounds of formula [Mn(mal)(H2O)(2,4′-bpy)]n (1) and [Mn2(mal)2(H2O)2(4,4′-bpy)]n (2) (2,4′-bpy = 2,4′-bipyridine, 4,4′-bpy = 4,4′-bipyridine and H2mal = malonic acid) have been prepared and structurally characterized by X-ray crystallography. Their structures are made up of two- (1) and three-dimensional (2) arrangements of manganese atoms linked by carboxylate-malonate groups in the anti–syn bridging mode (1 and 2) and bis(monodentate) 4,4′-bpy (2). The 2,4′-bpy group in 1 acts as a monodentate ligand. Each manganese atom in 1 and 2 is six-coordinated with four carboxylate-oxygens in the equatorial plane and a nitrogen atom and a water molecule in the axial positio…
Synthesis, crystal structure and magnetic properties of two-dimensional malonato-bridged cobalt(ii) and nickel(ii) compounds
Two isostructural malonato-bridged complexes of formula {[M(H2O)2][M(mal)2(H2O)2]}n [M = Co(II) (1), Ni(II) (2); H2mal = malonic acid] have been synthesised and characterized by X-ray diffraction. Their structure consists of corrugated layers of trans-diaquabismalonatemetalate(II) and trans-diaquametal(II) units bridged by carboxylate–malonate groups in the anti–syn conformation. Two crystallographycally independent metal atoms occur in 1 and 2. The malonate anion acts simultaneously as a bidentate and bis-monodentate ligand. Variable-temperature (1.9–295 K) magnetic susceptibility measurements indicate the occurrence of weak antiferro- (1) and ferromagnetic (2) interactions between the cob…