Svetlana G. Baca

Nickel(II)-, cobalt(II)-, copper(II)-, and zinc(II)-phthalate and 1-methylimidazole coordination compounds: synthesis, crystal structures and magnetic properties

Three new coordination polymers [M(Pht)(1-MeIm)2]n (where M=Cu (1), Zn (2), Co (3); Pht2−=dianion of o-phthalic acid; 1-MeIm=1-methylimidazole) and two compounds [M(1-MeIm)6](HPht)2 · 2H2O (M=Co (4), Ni (5)) have been synthesized and characterized by X-ray crystallography. The structures of 1–3 (2 is isostructural to 3) consist of [M(1-MeIm)2] building units connected by 1,6-bridging phthalate ions to form infinite chains. In complex 1, each copper(II) center adopts a square coordination mode of N2O2 type by two O atoms from different phthalate ions and two N atoms of 1-MeIm, whereas in 3 two independent metal atoms are tetrahedrally (N2O2) coordinated to a pair of Pht ligands and a pair of 1-MeIm molecules. There are only van der Waals interactions between the chains in 1, while the three-dimensional network in 3 is assembled by C–H⋯O contacts. In contrast to polymers 1–3 the structures of 4 and 5 (complexes are also isostructural) are made up of the [M(1-MeIm)6]2+ cation, two hydrogen phthalate anions (HPht−) and two H2O solvate molecules. The coordination around each metal(II) atom is octahedral with six nitrogen atoms of 1-MeIm. Extended hydrogen bonding networks embracing the solvate water molecules and a phthalate residue as well as the weak C–H⋯O interactions stabilize the three-dimensional structures. Magnetic studies clearly show that the magnetic ions do not interact with each other. Furthermore, in compound 4 we have another example of a highly anisotropic Co2+ ion with a rhombic g-tensor and large zero-field-splitting. The complexes were also characterized by IR and 1H NMR spectroscopy, thermogravimetric analysis, and all data are discussed in the terms of known structures.

Synthesis and X-ray diffraction study of Zn(II) complexes with o-phthalic acid and aromatic amines ☆

Abstract New zinc (II) complexes [Zn(Pht)A2], where Pht2−=dianion of o-phthalic acid, A=pyridine (1), 3-methylpyridine (2), 4-methylpyridine (3) and [Zn(Pht)A] (A=4-methylpyridine (4)) have been synthesised and characterised by X-ray crystallography. The compounds have polymeric structures due to 1,6-bridging ability of the o-phthalate ligand. Polymeric chains exhibit three types of organisation in the crystal. Complexes 1 and 2 have similar structures, where Zn atom is coordinated by two oxygen atoms of two carboxylate groups and two nitrogen atoms of N-containing ligands. Two independent Zn atoms in 3 have different environments: tetrahedral N2O2 and distorted square-pyramidal N2O3. One of the acid residues behaves as bidentate 1,6-bridge, while the other acts as tridentate (1,6-bridging and 1,3-chelating) ligand. One of the Zn atoms in 4 has a tetrahedral NO3 geometry, while the second is characterised by a distorted octahedral NO5 coordination polyhedron. Both phthalate anions are tetradentate and act as syn–syn, syn–anti and monoatomic Zn–O–Zn bridging ligands. The IR spectra are discussed in relation to the crystal structures.

Zinc(II) carboxylates with imidazole and 2-methylimidazole: unprecedented cyclic dimer and polynuclear coordination polymers based on bridging phthalate ions

Novel zinc(II) coordination polymer [Zn(Pht)(Im)2]n (1), unique cyclic dimer [Zn(Pht)(Im)(H2O)]2 (2) and coordination polymer [Zn(Pht)(2-MeIm)]n (3) (where Pht2−=dianion of o-phthalic acid, Im=imidazole, 2-MeIm=2-methylimidazole) have been synthesized and their structures characterized by X-ray crystallography. Both carboxylate groups of the phthalate dianion coordinate in a monodentate mode bridging two Zn(II) ions with formation of 1D zigzag chain in 1. Two Im ligands play a double role: they coordinate the metal atom and join the coordination polymers via NH⋯O hydrogen bonds into a 3D-network. Complex 2 represents the first example of a metallocycle in which two Zn(II) atoms are bridged by two phthalate ligands forming a 14-membered ring. The Zn(II) atom is coordinated by two O atoms of Pht2− carboxylate groups, N atom of the Im and O atom of the water molecule with formation of tetrahedral NO3 metal-binding site. The molecules of 2 form a 3D-network through NH⋯O and OH⋯O hydrogen bonds between carboxylate groups of Pht2−, Im and water molecules. Compound 3 reveals the characteristic structural features of both compounds 1 and 2. One pair of zinc atoms is linked by 1,6-bridge of two phthalate ligands, while the other is held together through syn–syn bridging carboxylate groups in a 1,3-fashion from the same phthalates. As a result, infinite chains with alternation of 14-membered and eight-membered cycles are formed. Additional hydrogen bonds link the chains to form a 2D-network. IR and 1H NMR spectra of 1–3 are also reported.

One-Dimensional Coordination Polymers from Hexanuclear Manganese Carboxylate Clusters Featuring a {MnII4MnIII2(μ4-O)2} Core and Spacer Linkers

The bridging of hexanuclear mixed-valent carboxylate coordination clusters of the type [Mn(6)O(2)(O(2)CR)(10)] (R = CMe(3); CHMe(2)) featuring a {Mn(II)(4)Mn(III)(2)(mu(4)-O)(2)} core by geometrically rigid as well as flexible spacer ligands such as pyrazine (pyz), nicotinamide (na), or 1,2-bis(4-pyridyl)ethane (bpe) results exclusively in one-dimensional (1D) coordination polymers. The formation of {[Mn(6)O(2)(O(2)CCMe(3))(10)(Me(3)CCO(2)H)(EtOH)(na)] x EtOH x H(2)O}(n) (1), {[Mn(6)O(2)(O(2)CCHMe(2))(10)(pyz)(3)] x H(2)O}(n) (2), and {[Mn(6)O(2)(O(2)CCHMe(2))(10)(Me(2)CHCO(2)H)(EtOH)(bpe)] x Me(2)CHCO(2)H}(n) (3) illustrates a surprising preference of the interlinked {Mn(6)} units toward 1D coordination chains. In the solid-state, the observed chain propagation axes are either colinear (1 and 3) or perpendicular (2), whereby crystal packing is further influenced by solvent molecules. Magnetic properties of these network compounds can be rationalized based on that the magnetism of discrete [Mn(6)O(2)(O(2)CR)(10)]-type coordination clusters with all-antiferromagnetic intramolecular exchange and weak antiferromagnetic intercluster coupling in 1, 2, and 3 follows the expected exchange coupling strength of the employed spacer linkers.

Synthesis and structural characterisation of unprecedented dinuclear zinc(II) complex with H-bonded bridging phthalate ions

Abstract An extremely unusual dimer [(bpy)2Zn(Pht)H(Pht)Zn(bpy)2)](HPht)(H2Pht)·2H2O (1) (where Pht2−=dianion of o-phthalic acid, bpy=2,2′-bipyridine) in which [Zn(bpy)2] metal cores are connected through Pht⋯H⋯Pht bridge has been synthesised and its structure determined by X-ray crystallography.

Cluster-based networks: 1D and 2D coordination polymers based on {MnFe2(μ3-O)}-type clusters.

A straightforward approach to heterometallic Mn-Fe cluster-based coordination polymers is presented. By employing a mixed-valent μ(3)-oxo trinuclear manganese(II/III) pivalate cluster, isolated as [Mn(II)Mn(III)(2)O(O(2)CCMe(3))(6)(hmta)(3)]·(solvent) (hmta = hexamethylenetetramine; solvent = n-propanol (1), toluene (2)) in the reaction with a μ(3)-oxo trinuclear iron(III) pivalate cluster compound, [Fe(3)O(O(2)CCMe(3))(6)(H(2)O)(3)]O(2)CCMe(3)·2Me(3)CCO(2)H, three new heterometallic {Mn(II)Fe(III)(2)} cluster-based coordination polymers were obtained: the one-dimensional polymer chain compounds {[MnFe(2)O(O(2)CCMe(3))(6)(hmta)(2)]·0.5MeCN}(n) (3) and {[MnFe(2)O(O(2)CCMe(3))(6)(hmta)(2)]·Me(3)CCO(2)H·(n-hexane)}(n) (4) and the two-dimensional layer compound {[MnFe(2)O(O(2)CCMe(3))(6)(hmta)(1.5)]·(toluene)}(n) (5). Single-crystal X-ray diffraction analysis reveals a μ(3)-oxo trinuclear pivalate cluster building block as the main constituent in all polymer compounds. Different M:hmta ratios in 1-5 are related to the different structural functions of the N-containing ligand. In clusters 1 and 2, three hmta ligands are monodentate, whereas in chains 3 and 4 two hmta ligands act as bridging ligands and one is a monodentate ligand; in 5, all hmta molecules act as bidentate bridges. Magnetic studies indicate dominant antiferromagnetic interactions between the metal centers in both homometallic {Mn(3)}-type clusters 1 and 2 and heterometallic {MnFe(2)}-type coordination polymers 3-5. Modeling of the magnetic susceptibility data to a isotropic model Hamiltonian yields least-squares fits for the following parameters: J(1)(Mn(II)-Mn(III)) = -6.6 cm(-1) and J(2)(Mn(III)-Mn(III)) = -5.4 cm(-1) for 1; J(1) = -5.5 cm(-1) and J(2)(Mn(III)-Mn(III)) = -3.9 cm(-1) for 2; J(1)(Mn(II)-Fe(III)) = -17.1 cm(-1) and J(2)(Fe(III)-Fe(III)) = -43.7 cm(-1) for 3; J(1) = -23.8 cm(-1) and J(2) = -53.4 cm(-1) for 4; J(1) = -13.3 cm(-1) and J(2) = -35.4 cm(-1) for 5. Intercluster coupling plays a significant role in all compounds 1-5.

Three-component coordination networks based on [Ru(phen)(CN)4]2− anions, lanthanide(III) cations and ancillary oligopyridine ligands

Combination of [Ru(phen)(CN)4]2−, a lanthanide(III) cation and an additional oligopyridine ligand (1,10-phenanthroline or 2,2′∶6′,2″-terpyridine) affords three-component coordination networks based on Ru–CN–Ln linkages, in which some coordination sites of the lanthanide cation are blocked by the oligopyridine ligand.

Ultralarge 3d/4f Coordination Wheels: From Carboxylate/Amino Alcohol-Supported {Fe4Ln2} to {Fe18Ln6} Rings

A family of wheel-shaped charge-neutral heterometallic {FeIII4LnIII2}- and {FeIII18MIII6}-type coordination clusters demonstrates the intricate interplay of solvent effects and structure-directing roles of semiflexible bridging ligands. The {Fe4Ln2}-type compounds [Fe4Ln2(O2CCMe3)6(N3)4(Htea)4]·2(EtOH), Ln = Dy (1a), Er (1b), Ho (1c); [Fe4Tb2(O2CCMe3)6(N3)4(Htea)4] (1d); [Fe4Ln2(O2CCMe3)6(N3)4(Htea)4]·2(CH2Cl2), Ln = Dy (2a), Er (2b); [Fe4Ln2(O2CCMe3)4(N3)6(Htea)4]·2(EtOH)·2(CH2Cl2), Ln = Dy (3a), Er (3b) and the {Fe18M6}-type compounds [Fe18M6(O2CCHMe2)12(Htea)18(tea)6(N3)6]·n(solvent), M = Dy (4, 4a), Gd (5), Tb (6), Ho (7), Sm (8), Eu (9), and Y (10) form in ca. 20–40% yields in direct reaction of trinuclear FeIII pivalate or isobutyrate clusters, lanthanide/yttrium nitrates, and bridging triethanolamine (H3tea) and azide ligands in different solvents: EtOH for the smaller {Fe4Ln2} wheels and MeOH/MeCN or MeOH/EtOH for the larger {Fe18M6} wheels. Single-crystal X-ray diffraction analyses revealed that 1–3 consist of planar centrosymmetric hexanuclear clusters built from FeIII and LnIII ions linked by an array of bridging carboxylate, azide, and aminopolyalcoholato-based ligands into a cyclic structure with a cavity, and with distinct sets of crystal solvents (2 EtOH per formula unit in 1a–c, 2 CH2Cl2 in 2, and 2 EtOH and 2 CH2Cl2 in 3). In 4–10, the largest 3d/4f wheels currently known, nearly linear Fe3 fragments are joined via mononuclear Ln/Y units by a set of isobutyrates and amino alcohol ligands into virtually planar rings. The magnetic properties of 1–10 reveal slow magnetization relaxation for {Fe4Tb2} (1d) and slow relaxation for {Fe4Ho2} (1c), {Fe18Dy6} (4), and {Fe18Tb6} (6).

From pink to blue and back to pink again: changing the Co(II) ligation in a two-dimensional coordination network upon desolvation

Heating of a pink two-dimensional Co(II) coordination network {[Co2(μ2-OH2)(bdc)2(S-nia)2(H2O)(dmf)]·2(dmf)·(H2O)}n (1) built from 1,4-benzenedicarboxylic acid (H2bdc) residues and thionicotinamide (S-nia) ligands initiates a single-crystal-to-single-crystal transition accompanied by removal of both coordinated and co-crystallized solvents. In the dry blue form, [Co(bdc)(S-nia)]n (dry_1), the Co(II) centers changed from an octahedral to a square pyramidal configuration.

Understanding the magnetism of {Fe2Ln} dimers, step-by-step

A magnetochemical comparison between the {FeIII4LnIII2}-type coordination clusters [Fe4M2(OH)2(N3)2(bdea)4(O2CCMe3)5(H2O)]NO3·2(EtOH) (M = Dy, Y) and [Fe4M2(OH)2(N3)2(bdea)4(O2CCMe3)4(NO3)2]·3(EtOH) (M = Gd, Eu; H2bdea = N-butyldiethanolamine), of which {Fe4Dy2} reveals slow molecular magnetization relaxation up to 6 K, allows assessment of the exchange coupling governing the clusters’ multiplet patterns.