Supramolecular coordination chemistry of aromatic polyoxalamide ligands: A metallosupramolecular approach toward functional magnetic materials

The impressive potential of the metallosupramolecular approach in designing new functional magnetic materials constitutes a great scientific challenge for the chemical research community that requires an interdisciplinary collaboration. New fundamental concepts and future applications in nanoscience and nanotechnology will emerge from the study of magnetism as a supramolecular function in metallosupramolecular chemistry. Our recent work on the rich supramolecular coordination chemistry of a novel family of aromatic polyoxalamide (APOXA) ligands with first-row transition metal ions has allowed us to move one step further in the rational design of metallosupramolecular assemblies of increasing structural and magnetic complexity. Thus, we have taken advantage of the new developments of metallosupramolecular chemistry and, in particular, the molecular-programmed self-assembly methods that exploit the coordination preferences of paramagnetic metal ions and suitable designed polytopic ligands. The resulting self-assembled di- and trinuclear metallacyclic complexes with APOXA ligands, either metallacyclophanes or metallacryptands, are indeed ideal model systems for the study of the electron exchange mechanism between paramagnetic metal centers through extended π-conjugated aromatic bridges. So, the influence of different factors such as the topology and conformation of the bridging ligand or the electronic configuration and magnetic anisotropy of the metal ion have been investigated in a systematic way. These oligonuclear metallacyclic complexes can be important in the development of a new class of molecular magnetic devices, such as molecular magnetic wires (MMWs) and switches (MMSs), which are major goals in the field of molecular electronics and spintronics. On the other hand, because of their metal binding capacity through the outer carbonyl-oxygen atoms of the oxamato groups, they can further be used as ligands, referred to as metal–organic ligands (MOLs), toward either coordinatively unsaturated metal complexes or fully solvated metal ions. This well-known “complex-as-ligand” approach affords a wide variety of high-nuclearity metal–organic clusters (MOCs) and high-dimensionality metal–organic polymers (MOPs). The judicious choice of the oligonuclear MOL, ranging from mono- to di- and trinuclear species, has allowed us to control the overall structure and magnetic properties of the final oxamato-bridged multidimensional (nD, n = 0–3) MOCs and MOPs. The intercrossing between short- (nanoscopic) and long-range (macroscopic) magnetic behavior has been investigated in this unique family of oxamato-bridged metallosupramolecular magnetic materials expanding the examples of low-dimensional, single-molecule (SMMs) and single-chain (SCMs) magnets and high-dimensional, open-framework magnets (OFMs), which are brand-new targets in the field of molecular magnetism and materials science

An {Fe₆₀} tetrahedral cage: building nanoscopic molecular assemblies through cyanometallate and alkoxo linkers

International audienceA nanoscopic {Fe60} coordination cage (approximately 3 nm) was prepared by the self assembly of a partially blocked tricyanidoferrate(III) complex and tris(alkoxo)-based iron(III) coordination motifs. This cage is a rare example of a mixed cyanido/alkoxo-bridged high nuclearity complex and it exemplifies the great potential of this new synthetic route to generate uncommon molecular architectures using cyanometallates as metalloligands versus alkoxo-based polynuclear entities

[Cr(phen)(ox)2]-: A versatile Bis-Oxalato Building for the Design of Heteropolymetallic System. Crystal Structures and Magnetic Properties of AsPh4[Cr(phen)(ox)2].H2O, [NaCr(phen)(ox)2(H2O)].H2O abd {[Cr(phen)(ox)2]2[Mn2(bipy)2(H2O)2(ox)]}.6H2O

[EN] The new complexes of formula AsPh4[Cr(phen)(ox)(2)] . H2O (1), [NaCr(phen)(ox)(2)(H2O)] . 2H(2)O (2) and {[Cr(phen)(ox)(2)](2)[Mn-2(bpy)(2)(H2O)(2)(ox)]} . 6H(2)O (3) (AsPh4 = tetraphenylarsonium cation; phen = 1,10-phenanthroline; ox = oxalate dianion; bpy = 2,2'-bipyridine) have been prepared and characterized by single-crystal X-ray diffraction. The structure of 1 consists of discrete [Cr(phen)(ox)(2)](-) anions, tetraphenylarsonium cations and uncoordinated water molecules. The chromium environment in 1 is distorted octahedral with Cr-O bond distances between 1.959(3) and 1.947(3) Angstrom and Cr-N bonds of 2.083(4) and 2.072(4) Angstrom. The angles subtended at the chromium atom by the two oxalates are 83.6(2) and 83.3(1)degrees whereas the N-Cr-N angle is 79.9(2)degrees. The [Cr(phen)(ox)(2)](-) unit of 1 is also present in 2 and 3 but it accomplishes different coordination functions, acting as a bridging (2) or terminal (3) ligand. 2 has a layered structure made up of oxalato-bridged bimetallic Cr-III-Na-I helical chains that are interconnected through centrosymmetric Na2O2 units. The two oxalates of [Cr(phen)(ox)(2)](-) in 2 are bis-chelating within the bimetallic chain but one of them is in addition monodentate towards a sodium atom of a neighbouring chain, yielding a sheetlike structure. The sodium atom in 2 has a distorted octahedral geometry with five Na-O(ox) bonds ranging from 2.453(5) to 2.319(4) Angstrom and the sixth position being occupied by an aqua ligand with Na-O(w) = 2.384(6) Angstrom. The intralayer chromium-sodium and sodium-sodium separations through bridging oxalate in 2 are 5.560(4) and 3.643(8) Angstrom, respectively. The structure of 3 consists of neutral tetranuclear (Cr2Mn2II)-Mn-III units in which two terminal [Cr(phen)(ox)(2)](-) entities act as monodentate ligands towards a central oxalato-bridged manganese(II) dimer. Each manganese atom is six-coordinated as MnN2O4: two nitrogen atoms of a chelating bpy, one aqua ligand and three oxalate oxygens build a distorted octahedron around the manganese atom. The Mn-O(ox) and Mn-N(bpy) bond lengths vary in the ranges 2.219(12)-2.160(13) and 2.33(2)-2.14(2) Angstrom, respectively. The intramolecular chromium-manganese separation [5.507(5) and 5.502(5) A for Cr(2) Mn(2) and Cr(1)...Mn(1)] is somewhat shorter that the manganese-manganese one [5.703(2) Angstrom]. The magnetic properties of 1-3 have been investigated in the temperature range 1.9-300 K. Very weak antiferromagnetic interactions between the chromium centers are observed in 1 and 2 in agreement with their crystal structures. In the case of 3, significant intramolecular antiferromagnetic interactions between the adjacent chromium(III) and manganese(II) ions (j = -1.1 cm(-1), through the chelating/monodentate oxalato) and between the two manganese(II) ions (J = - 2.2 cm-1 through the bis-chelating oxalato) occur, the Hamiltonian being defined as (H) over cap = -J (S) over cap(Mn1) . (S) over cap(Mn2) - j[(S) over cap(Cr1) . (S) over cap(Mn1) + (S) over cap(Cr2) . (S) over cap(Mn2)].Financial support from the Spanish Dirección General de Investigación Científica y Técnica (DGICYT) through Project PB97-1397, the Romanian Ministry of Education (Grants 30C/CNCSIS and 1D/CMCSIS), the TMR Program from the European Union (Contract ERBFMRXCT98-0181) and the COST Program (Action 518) is gratefully acknowledged. Thanks are also extended to the Centre d'Informàtica de la Universitat de València for computer resource support.Marinescu, G.; Andruh, M.; Lescouëzec, R.; Muñoz Roca, MDC.; Cano, J.; Lloret, F.; Julve, M. (2000). [Cr(phen)(ox)2]-: A versatile Bis-Oxalato Building for the Design of Heteropolymetallic System. Crystal Structures and Magnetic Properties of AsPh4[Cr(phen)(ox)2].H2O, [NaCr(phen)(ox)2(H2O)].H2O abd {[Cr(phen)(ox)2]2[Mn2(bipy)2(H2O)2(ox)]}.6H2O. New Journal of Chemistry. 24(7):527-536. https://doi.org/10.1039/b002246mS52753624

CCDC 1409712: Experimental Crystal Structure Determination

Related Article: J.-R. Jiménez, A. Mondal, L.-M. Chamoreau, P. Fertey, F. Tuna, M. Julve, A. Bousseksou, R. Lescouëzec, L. Lisnard|2016|Dalton Trans.|45|17610|doi:10.1039/C6DT03151

[Cr(dpa)(ox)2]-: a new bis-oxalato building block for the design of heteropolymetallic systems. Crystal structures and magnetic properties of PPh4[Cr(dpa)(ox)2], AsPh4[Cr(dpa)(ox)2], Hdpa[Cr(dpa)(ox)2].4H2O, Rad[Cr(dpa)(ox)2].H2O and Sr[Cr(dpa)(ox)2]

[EN] The new complexes of formulae PPh4[Cr(dpa)(ox)(2)] (1), AsPh4[Cr(dpa)(OX)(2)] (2), Hdpa[Cr(dpa)(ox)(2)]-4H(2)O (3), Rad[Cr(dpa)(ox)(2)] . H2O (4) and Sr[Cr(dpa)(ox)(2)](2) . 8H(2)O (5) [PPh4 = tetraphenylphosphonium cation; AsPh4 = tetraphenylarsoniurn cation; dpa = 2,T-dipyridylamine; ox = oxalate dianion; Rad = 2-(4-N-methylpyridinium)4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-a-oxyl-3-N-oxide] have been prepared and characterised by single-crystal X-ray diffraction. The structures of 1-4 consist of discrete [Cr(dpa)(ox)(2)](-) anions, tetraphenylphosphonium. (1), tetraphenylarsonium (2), monoprotonated Hdpa (3) and univalent radical (4) cations and uncoordinated water molecules (2-4). The chromium environment in 1-4 is distorted octahedral with Cr-O bond distances between 1.982(2)-1.946(2) Angstrom and Cr-N bonds of 2.0716(17)-2.048(3) Angstrom. The angles subtended at the chromium atom by the two oxalates are 83.6(2)-81.71(8)degrees, whereas the N-Cr-N angles are 87.76(7)-86.24(9)degrees. The [Cr(dpa)(ox)(2)](-) unit of 1-4 is also present in 5 but it acts as a chelating ligand through its two oxalato groups towards divalent strontium cations, yielding heterobimetallic zig-zag chains that run parallel to the a axis. Each chain is formed of diamond-shaped units sharing the strontium atoms, while the two other corners are occupied by two crystallographically independent chromium atoms. The [Cr(dpa)(ox)(2)](-) unit in 5 retains the environment observed in 1-4 and the strontium atom is coordinated to eight oxalate oxygens from four oxalate ligands. The two crystallographycally independent chromium centres within each double chain have opposite chirality. However, the adjacent double chains are related by an inversion centre resulting in achiral layers parallel to the ac plane. The magnetic properties of 1-5 have been investigated in the temperature range 1.9-290 K. A quasi Curie law behaviour is observed for 1-3 and 5 in agreement with their crystal structures, whereas a significant antiferromagnetic interaction between the chromium(m) and the radical centre occurs in the case of 4. The synthetic possibilities offered by the use of the heteroleptic species [CrL(ox)(2)](-) (L = alpha -diimine-type ligand) as a ligand towards metal ions is analysed and discussed in the fight of the available structural results.Financial support from the Spanish Dirección General de Investigación Científica y Técnica (DGICYT) through Projects PB97-1397 and PB98-1044, the Romanian Ministry of Education (Grants 30C/CNCSIS and 1D/CNCSIS) and the TMR Program from the European Union (Contract ERBFMRXCT98-0181) is acknowledged. Thanks are also extended to the Centre d'Informàtica de la Universitat de València for computer resource support.Lescouëzec, R.; Marinescu, G.; Muñoz Roca, MDC.; Luneau, D.; Andruh, M.; Lloret, F.; Faus, J.... (2001). [Cr(dpa)(ox)2]-: a new bis-oxalato building block for the design of heteropolymetallic systems. Crystal structures and magnetic properties of PPh4[Cr(dpa)(ox)2], AsPh4[Cr(dpa)(ox)2], Hdpa[Cr(dpa)(ox)2].4H2O, Rad[Cr(dpa)(ox)2].H2O and Sr[Cr(dpa)(ox)2]. New Journal of Chemistry. 25(10):1224-1235. https://doi.org/10.1039/b104469aS12241235251

Rational design of a new class of heterobimetallic molecule-based magnets: Synthesis, crystal structures, and magnetic properties of oxamato-bridged M 3M2 (M = LiI and MnII; M = NiII and CoII) open-frameworks with a three-dimensional honeycomb architecture

[EN] Two new series of oxamato-bridged heterobimetallic coordination networks of general formula Li-5[Li3M2(mpba)(3)(H2O)(6)] center dot 31H(2)O [M= Ni-II (1a) and Co-II (1b)] and Li-2[Mn3M2(mpba)(3)(H2O)(6)] center dot 22H(2)O [M = Ni-II (2a) and Co-II (2b)] have been prepared from the metal- mediated self-assembly of the hexakis(bidentate), triple-stranded dinickel(I) and dicobalt(II) complexes [M-2(mpba)(3)](8) [mpba = meta-phenylenebis(oxamato)] with either monovalent lithium(I) or divalent manganese(II) ions respectively, in water. X-ray structural analyses of 1a and 1b show an anionic three-dimensional network formed by an infinite parallel array of oxamato-bridged (Li3M2II)-M-I (M = Ni and Co) hexagonal layers, which are interconnected through three m-phenylenediamidate bridges between the M-II ions of opposite propeller chirality (Lambda and Lambda) to give dinuclear metallacrypt and cores of the meso-helicate-type. The intralayer Li-M distance through the oxamate bridge is 5.380(3) (1a) and 5.396(5) (1b) angstrom, while the interlayer M-M distance through the triple m-phenylenediamidate bridge is 6.856(3) (1a) and 6.851(3) (1b) angstrom. Overall, this leads to an open-framework honeycomb structure with large hexagonal pores of ca. 21.8 (1a) and 21.5 angstrom (1b) in diameter which are occupied by linear arrays of water-bridged Li-I countercations. Variable-temperature (2.0-300 K) dc magnetic susceptibility and variable-field (0-5.0 T) magnetization measurements on these two series of compounds reveal a distinct magnetic behavior mainly depending on the diamagnetic or paramagnetic nature of the Li-I and Mn-II ions, respectively. Compounds 1a and 1b behave as rather well-isolated MI2II (M = Ni and Co) dimers with a moderate to weak ferromagnetic coupling(J(Ni-Ni) = + 3.17 cm (1) and J(Co-Co) = + 1.03 cm (1)) between the two M-II ions across the triple m-phenylenediamidate bridge, together with either an appreciable to remarkable local ion axial magnetic anisotropy (D-Ni = -3.35 cm (1)) or spin-orbit coupling (lambda(Co) = - 167.3 cm (1)); the next nearest-neighbor magnetic interactions between the M-II ions through the diamagnetic Li-I ions are negligible. Compounds 2a and 2b behave instead as strongly coupled oxamato-bridged (Mn3M2II)-M-II (M = Ni and Co) ferrimagnetic planes which are weakly interacting through the m-phenylenediamidate bridges, leading thus to a long-range 3D ferromagnetic order at T-C = 6.5 K. In addition, the variable-temperature (2.0-12 K) ac magnetic susceptibility measurements on 2a and 2b show an intriguing frequency-dependent magnetic behavior characteristic of a spin-glass dynamics. This glassy behavior is likely attributed to their amorphous character and/or the moderate to strong magnetic anisotropy of the dinickel(II) and dicobalt(II) precursors.This work was supported by the Ministerio de Educación y Ciencia (MEC, Spain) (Projects CTQ2007-61690 and CSD2007-00010), the Ministère de l Enseignement Supérieur et de la Recherche (MESR, France), the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brazil) (Project COFECUB 460/04), and the Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG, Brazil) (Projects CEX1837/06 and PRONEX 526/07). D.C., E.P., and M.-C.D. thank the CAPES, the MEC, and the MESR/UPMC for grants. J.C. acknowledges the Universitat de València for an invited researcher grant.Cangussu, D.; Pardo, E.; Dul, MC.; Lescouëzec, R.; Herson, P.; Journaux, Y.; Pedroso, EF.... (2008). Rational design of a new class of heterobimetallic molecule-based magnets: Synthesis, crystal structures, and magnetic properties of oxamato-bridged M 3M2 (M = LiI and MnII; M = NiII and CoII) open-frameworks with a three-dimensional honeycomb architecture. Inorganica Chimica Acta. 361(12-13):3394-3402. https://doi.org/10.1016/j.ica.2008.02.042S3394340236112-1