The supramolecular chemistry of metal complexes with heavily substituted imidazoles as ligands: Cobalt(II) and zinc(II) complexes of 1-methyl-4,5-diphenylimidazole

Solvatomorphism in a series of copper(II) complexes with the 5-phenylimidazole/perchlorate system as ligands

In the course of an investigation of the supramolecular behaviour of copper(II) complexes with the 5-phenylimidazole/perchlorate ligand system (`blend') remarkable solvatomorphism has been observed. By employing a variety of crystallization solvents (polar protic, polar/non-polar aprotic), a series of 12 crystalline solvatomorphs with the general formula [Cu(ClO4)2(LH)4]·x(solvent) have been obtained [LH = 5-phenylimidazole, x(solvent) = 3.3(H2O) (1), 2(methanol) (2), 2(ethanol) (3), 2(1-propanol) (4), 2(2-propanol) (5), 2(2-butanol) (6), 2(dimethylformamide) (7), 2(acetone) (8), 2(tetrahydrofurane) (9), 2(1,4-dioxane) (10), 2(ethyl acetate) (11) and 1(diethyl ether) (12)]. The structures have been solved using single-crystal X-ray diffraction and the complexes were characterized by thermal analysis and infrared spectroscopy. The solvatomorphs are isostructural (triclinic, P1), with the exception of compound 9 (monoclinic, P21/n). The supramolecular structures and the role of the various solvents is discussed. All potential hydrogen-bond functionalities, both of the [Cu(ClO4)2(LH)4] units and of the solvents, are utilized in the course of the crystallization process. The supramolecular assembly in all structures is directed by strong recurring Nimidazole-H...Operchlorate motifs leading to robust scaffolds composed of the [Cu(ClO4)2(LH)4] host complexes. The solvents are located in channels and, with the exception of the disordered waters in 1 and the diethyl ether in 12, participate in hydrogen-bonding formation with the [Cu(ClO4)2(LH)4] complexes, serving as both hydrogen-bond acceptors and donors (for the polar protic solvents in 2-6), or solely as hydrogen-bond acceptors (for the polar/non-polar aprotic solvents in 7-11), linking the complexes and contributing to the stability of the crystalline compounds.

Influence of ligand positional isomerism on the molecular and supramolecular structures of cobalt(II)-phenylimidazole complexes

In a study to evaluate the impact of flexible positional isomeric ligands on the coordination geometry and self-assembly process of 3d metal complexes, the synthesis of eight new cobalt(II) complexes with the 2-phenylimidazole (LH) and 5-phenylimidazole (L'H) ligands has been carried out. A variety of parameters/conditions have been probed using the general Co^II/X^-/LH or L'H (X^- = Cl^-, Br^-, I^-, NO₃^-, NCS^-, ClO₄^-, SO₄^2-) reaction system. Interestingly, X-ray analyses reveal two distinct groups of complexes: reactions with LH only lead to tetrahedral or quasi-tetrahedral complexes {i.e. [CoCl₂(LH)₂] (1), [CoI₂(LH)₂] (2), [Co(NO₃)₂(LH)₂] (3), [Co(NCS)₂(LH)₂] (4)}, whereas L'H favours octahedral coordination {i.e. [Co(L'H)₄(MeCN)(H₂O)]I₂ (5), [Co(L'H)₄(MeCN)(H₂O)](NO₃)₂ (6) and [Co(NCS)₂(L'H)₄)]·2MeOH (7·2MeOH)}. A tetrahedral [Co(NCS)₂(L'H)₂)] (8) complex was also concurrently isolated with complex 7. The effects of the positional isomeric ligands LH and L'H and of the coordinated inorganic anions on the stoichiometry and packing arrangements of the complexes are thoroughly discussed. The supramolecular assembly is firmly directed, in all types of complexes, by robust N-H...X (X = Cl, I, O or S) motifs, leading to varying dimensionalities (1D, 2D or 3D) and packing arrangements. The formation of these motifs has been activated by choosing appropriate anions X, acting as terminal ligands or counterions. At a second level of organization, additional subordinate C-H...X (X = Cl, I, O or S), C-H...π and π...π intermolecular interactions complement the rigidity of the complexes' packing towards compact 3D assemblies. Hirshfeld surface analyses provided insight into the intermolecular interactions, allowed quantification of the individual contact types and comparison between the complexes.

Sonochemical synthesis and characterization of new seven coordinated zinc, cadmium and mercury nitrate complexes: New precursors for nanostructure metal oxides

The nitrate complexes of group 12 elements with a tridentate Schiff base ligand (L = (E)-N1-((E)-3- phenylallylidene)-N2-(2-((E)-((E)-3-phenylallylidene) amino)ethyl) ethane-1,2-diamine) were synthesized via sonochemical process and characterized by various physical and chemical methods. The structural analysis of the zinc nitrate complex by single crystal X-ray diffraction analysis shows that the central atom is seven-coordinated by three nitrogen atoms from the Schiff base ligand as well as four oxygen atoms from two different nitrate anions. The geometry around the metal center can be described as a distorted pentagonal bipyramid. The crystal packing analysis of zinc nitrate complex indicates that the intermolecular interactions related to nitrate groups plays the essential role in the orientation of supramolecular structure. Hirshfeld surfaces (HS) and their corresponding fingerprint plots (FP) have been also used for further investigation of crystal structure of zinc nitrate complex. Furthermore thermal analyses (TG/DTG) of three nanostructure complexes were carried out and discussed. Finally, direct thermolysis of zinc and cadmium nitrate complexes in air atmosphere led to the production of zinc and cadmium oxide nanoparticles.

Supramolecular features in the engineering of 3d metal complexes with phenyl-substituted imidazoles as ligands: the case of copper(ii)

Interesting packing features are present in eleven Cu(ii) complexes with phenyl-substituted imidazoles.

Employment of methyl 2-pyridyl ketone oxime in 3d/4f-metal chemistry: dinuclear nickel(II)/lanthanide(III) species and complexes containing the metals in separate ions

The use of methyl 2-pyridyl ketone oxime (mpkoH) for the synthesis of Ni(II)/Ln(III) (Ln = lanthanide) complexes, using "one-pot" reactions in the absence of an external base, is described. Depending on the reaction and crystallization conditions employed, two families of complexes have been obtained. The first family consists of true heterometallic species and involves complexes [NiLn(mpko)(3)(mpkoH)(3)](ClO(4))(2), where Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho and Er. The second family contains the pseudo heterometallic complexes [Ni(mpkoH)(3)](2)[Ln(NO(3))(6)](ClO(4)), where Ln = La, Ce, Pr, Nd and Sm. The crystal structures of [NiCe(mpko)(3)(mpkoH)(3)](ClO(4))(2) (1), [NiDy(mpko)(3)(mpkoH)(3)](ClO(4))(2) (8) and [Ni(mpkoH)(3)](2)[La(NO(3))(6)](ClO(4)) (11) have been determined by single-crystal, X-ray crystallography. Complexes 1·1.2MeOH·0.6H(2)O and 8·1.2MeOH·0.6H(2)O crystallise in the monoclinic space group P2(1)/a and are isomorphous; there are two crystallographically independent cations in the unit cell, but their interatomic distances and angles differ little. The Ni(II) and Ln(III) ions are bridged by three oximate groups belonging to the η(1):η(1):η(1):μ mpko(-) ligands. The Ni(II) centre is octahedrally coordinated by the six nitrogen atoms of the mpko(-) ligands in a facial arrangement. The Ln(III) centre is bound to an (O(oximate))(3)N(6) set of donor atoms, the nitrogen atoms belonging to the three N,N'-bidentate chelating mpkoH ligands. The stereochemistry of the Ln(III) atoms has been evaluated by means of continuous shape measures (CShM). The two crystallographically independent Ce(III) atoms in 1 have tricapped trigonal prismatic and capped square antiprismatic coordination geometries, while the polyhedra of the Dy(III) atoms in 8 are both close to a tricapped trigonal prism. The octahedral Ni(II) atoms in 11 are both facially bound to a N(6) set of donor atoms from three N,N'-bidentate chelating mpkoH ligands, while the 12-coordinate La(III) centre in [La(NO(3))(6)](3-) is coordinated by six bidentate chelating nitrato groups. Variable-temperature, solid state dc magnetic susceptibility studies were carried out on complexes 2, 6, 7 and 8. The dc susceptibility data for 6 in the 2.0-300 K range have been fit to a model with one J value, revealing an antiferromagnetic Ni(II)···Gd(III) exchange interaction [J = -1.1 cm(-1) based on H = -J (Ŝ(Ni)·Ŝ(Gd))]. Antiferromagnetic Ni(II)···Pr(III), Ni(II)···Tb(III) and Ni(II)···Dy(III) exchange interactions have also been suggested for 2, 7 and 8, respectively. The combined work demonstrates the usefulness of mpko(-) in the preparation of interesting Ni(II)/Ln(III) compounds, without requiring the presence of external base and ancillary organic ligands.

Zinc(II) and Nickel(II) Benzoate Complexes from the Use of 1-methyl-4,5-diphenylimidazole

Two new complexes, [Zn(O(2)CPh)(2)(L)(2)].2MeOH (1.2MeOH) and [Ni(2)(O(2)CPh))(4)(L)(2)].2MeCN (2.2MeCN), have been synthesized and characterized by X-ray analysis in the course of an ongoing investigation of the M(II)/X(-)/L [M(II) = Co, Ni, Cu, Zn; X(-) = Cl(-), Br(-), I(-), NCS(-), NO(3) (-), N(3) (-), PhCO(2) (-); L = 1-methyl-4,5-diphenylimidazole] reaction system, aiming at understanding and assessing the relative strength and the way in which the intermolecular interactions control the supramolecular organization of these compounds. In the mononuclear complex 1.2MeOH, the benzoate ion acts as a monodentate ligand resulting in a distorted tetrahedral N(2)O(2) coordination environment. Complex 2.2MeCN exhibits a dinuclear paddle-wheel structure; each Ni(II) has a square pyramidal NiNO(4) chromophore with four benzoate oxygens in the basal plane and the pyridine-type nitrogen atom of one ligand L at the apex. The structure of 1.2MeOH is stabilized by intramolecular pi-pi interactions between aromatic rings of adjacent 4,5-diphenylimidazole moieties; it is a feature also evidenced in similar compounds of the type [MX(2)L(2)].