Effect of diamagnetic Zn(II) ions on the SMM properties of a series of trinuclear ZnDy2 and tetranuclear Zn2Dy2 (LnIII = Dy, Tb, Gd) complexes: combined experimental and theoretical studies.

To study the effect of diamagnetic ions on magnetic interactions, utilizing a compartmental ligand (Z)-2-(hydroxymethyl)-4-methyl-6-((quinolin-8-ylimino)methyl)phenol (LH2), two different series of ZnII-LnIII complexes, namely the trinuclear series of [DyZn2(L)2(µ2-OAc)2(CH3OH)2]·NO3·MeOH (1), [TbZn2(L)2(µ2-OAc)2(CH3OH)2]·NO3·5MeOH·H2O (2), and [GdZn2(L)2(µ2-OAc)2(CH3OH)2]·NO3·MeOH·CHCl3 (3) and the tetranuclear series of [Dy2Zn2(LH)4(NO3)4(µ2OAc)]·NO3·MeOH·H2O (4), [Tb2Zn2(LH)4(NO3)4(µ2-OAc)]·NO3·MeOH·2H2O (5), and [Gd2Zn2(LH)4(NO3)4(µ2-OAc)]·NO3·MeOH·2H2O (6), were synthesized. Trinuclear ZnII-LnIII complexes 1-3 consist of one LnIII ion sandwiched between two peripheral ZnII ions forming a bent type ZnII-DyIII-ZnII array with an angle of 110.64°. Tetranuclear ZnII-LnIII complexes 4-6 are basically a combination of two dinuclear moieties of [LnZn(LH)2(NO3)2]+ connected by one bidentate bridging acetate ion in µ2-OAc coordination mode. The detailed magnetic analysis reveals that complexes 1 and 4 are single molecule magnets having energy barriers of 34.98 K and 46.71 K with relaxation times (τ0) of 5.05 × 10-4 s and 5.24 × 10-4 s, respectively. Ab initio calculations were employed to analyze the magnetic anisotropy and magnetic exchange interaction between the ZnII and LnIII centers with the aim of gaining better insights into the magnetic dynamics of complexes 1-6.

Hexa- and octanuclear copper(II) complexes with a tetraeicosaaza amine macrocycle.

One hexa- and two octanuclear Cu(II) complexes were synthesised from different metal salts and a very large (8 + 8) tetraeicosaaza macrocycle. These nitrate, chloride and sulphate coordination compounds were characterised by taking elemental analysis, spectroscopy, crystallography and magnetic susceptibility measurements. Their crystal structures revealed different interesting coordination modes of Cu(II) cations and nuclearity in these centrosymmetric complexes. For the sulphate complex two different, homo- vs. heterochiral, arrangements of the same macrocycle L3 around the same Cu(II) cations take place.

Experimental and theoretical magnetostructural studies on discrete heterometallic cyanide-bridged dinuclear FeIIIMnII and tetranuclear FeIII2CuII2 complexes bearing tripodal pyrazolyl borate and tetradentate phenolate-based ligands.

Two new complexes [FeIII(Tp)(CN)2(µ-CN)MnIICl(HL1)]·3DMF (1) and {[FeIII(Tp)(CN)(µ2-NC)2CuII(HL2)](ClO4)}2·6DMF (2) (HL1 = 2-((((1-methylbenzimidazol-2-yl)methyl)(pyridin-2-ylmethyl)amino)methyl)phenol and HL2 = 2-(((pyridin-2-ylmethyl)(quinolin-2-ylmethyl)-amino)methyl)phenol) have been synthesized and characterized by elemental analysis and IR and UV/vis spectroscopy. Structural analysis revealed that 1 is a discrete dinuclear coordination complex and 2 is a discrete tetranuclear coordination complex. In complex 1, each MnII is in a distorted octahedral MN4OCl environment where coordination is satisfied by three nitrogen atoms and one oxygen atom of the ligand, and a chloride group and one nitrogen atom from cyanide. In complex 2, each Cu is in a distorted octahedral MN5O environment where coordination is satisfied by three nitrogen atoms and one oxygen atom of the ligand, and two nitrogen atoms from two cyanides. Direct current (dc) variable-temperature magnetic susceptibility measurements on polycrystalline samples of 1 and 2 were carried out in the temperature range of 1.8-300 K. Investigation of the magnetic properties reveals the occurrence of weak antiferromagnetic coupling between the low-spin FeIII (S = 1/2) ions and high-spin MnII (S = 5/2) ions in 1, while 2 exhibits ferro- and antiferromagnetic coupling between the metal ions in the tetranuclear CuII2FeIII2 unit. DFT calculations show ferromagnetic coupling in both complexes, although this appears to be weak in the case of complex 1. In addition, magnetostructural correlations reveal the magnetic behavior against Mn-N-C and Fe-C-N angles in 1 and Cu-N-C and Fe-C-N angles in 2.

Synthesis, Crystal Structures, and Optical and Magnetic Properties of Samarium, Terbium, and Erbium Coordination Entities Containing Mono-Substituted Imine Silsesquioxane Ligands.

Mono-substituted cage-like silsesquioxanes of the T8-type can play the role of potential ligands in the coordination chemistry. In this paper, we report on imine derivatives as ligands for samarium, terbium, and erbium cations and discuss their efficient synthesis, crystal structures, and magnetic and optical properties. X-ray analysis of the lanthanide coordination entities [MCl3(POSS)3]·2THF [M = Er3+ (3), Tb3+ (4), Sm3+ (5)] showed that all three compounds crystallize in the same space group with similar lattice parameters. All compounds contain an octahedrally coordinated metal atom, and additionally, 3 and 5 structures are strictly isomorphous. However, surprisingly, there are two different molecules in the crystal structure of the terbium coordination entity 4, monomer (sof 65%) and dimer (sof 35%), with one and two metal centers. Absorption measurements of the investigated materials recorded at 300 K showed that regardless of the lanthanide involved, their energy band gap equals 2.7 eV. Moreover, the analogues containing Tb3+ and Sm3+ exhibit luminescence typical of these rare earth ions in the visible and infrared spectral range, while the compound with Er3+ does not generate any emission. Direct current variable-temperature magnetic susceptibility measurements on polycrystalline samples of 3-5 were performed between 1.8 and 300 K. The magnetic properties of 3 and 4 are dominated by the crystal field effect on the Er3+ and Tb3+ ions, respectively, hiding the magnetic influence between the magnetic cations of adjacent molecules. Complex 5 exhibits a nature typical for the paramagnetism of the samarium(III) cation.

Multinuclear Ni(II) and Cu(II) complexes of a meso 6 + 6 macrocyclic amine derived from trans-1,2-diaminocyclopentane and 2,6-diformylpyridine.

Four hexanuclear chloride and sulphate Ni(II) and Cu(II) complexes 1, 2, 4 and 5 and one tetranuclear nitrate Cu(II) complex 3 have been synthesised from appropriate metal salts and 6 + 6 octadecaaza macrocyclic ligands. All obtained coordination compounds have been characterised by elemental analysis, spectroscopic methods (ESI MS, NMR and EPR), magnetic susceptibility measurements and X-ray crystallography. Their X-ray crystal structures reveal different coordination modes of metal cations involved in the obtained centro-symmetrical coordination compounds. The conformational folding of the macrocyclic ligand adopted in the respective complexes depends on the number of metal cations bound within the macrocycle but not on their type. The cavities of these multinuclear complexes might be occupied by solvent molecules and counter anions bound by hydrogen bonds or might be empty in the case where the macrocyclic ring of the ligand is squeezed in the middle. All obtained Ni(II) and Cu(II) coordination compounds are paramagnetic. This has been proved by their 1H NMR and EPR spectra and magnetic measurements. Direct current (DC) variable-temperature magnetic susceptibility measurements on the polycrystalline samples of 1-5 were carried out in the temperature range of 1.8-300 K. The magnetic behaviour of 1 and 2 is dominated by the magnetic anisotropy of the nickel(II) ion masking the magnetic interactions between magnetic centres. The magnetic data of 3-5 reveal small antiferromagnetic interactions within the Cu4 and Cu6 units. EPR experiments for 3-5 show, at 9.6 and 34 GHz frequencies, that the predominant contribution to the orbitals occupied by the unpaired electrons in the ground state originates from dx2-y2.

A 3D MOF based on Adamantoid Tetracopper(II) and Aminophosphine Oxide Cages: Structural Features and Magnetic and Catalytic Properties.

This work describes an unexpected generation of a new 3D metal-organic framework (MOF), [Cu4(µ-Cl)6(µ4-O)Cu(OH)2(µ-PTA═O)4]n·2nCl-EtOH·2.5nH2O, from copper(II) chloride and 1,3,5-triaza-7-phosphaadamantane 7-oxide (PTA═O). The obtained product is composed of diamandoid tetracopper(II) [Cu4(µ-Cl)6(µ4-O)] cages and monocopper(II) [Cu(OH)2] units that are assembled, via the diamandoid µ-PTA═O linkers, into an intricate 3D net with an nbo topology. Magnetic susceptibility measurements on this MOF in the temperature range of 1.8-300 K reveal a ferromagnetic interaction (J = +20 cm-1) between the neighboring copper(II) ions. Single-point DFT calculations disclose a strong delocalization of the spin density over the tetranuclear unit. The magnitude of exchange coupling, predicted from the broken-symmetry DFT studies, is in good agreement with the experimental data. This copper(II) compound also acts as an active catalyst for the mild oxidation and carboxylation of alkanes. The present study provides a unique example of an MOF that is assembled from two different types of adamantoid Cu4 and PTA═O cages, thus contributing to widening a diversity of functional metal-organic frameworks.

Synthesis, Crystal Structures, and Spectroscopic Properties of Novel Gadolinium and Erbium Triphenylsiloxide Coordination Entities.

In alkali metal and lanthanide coordination chemistry, triphenylsiloxides seem to be unduly underappreciated ligands. This is as surprising as that such substituents play a crucial role, among others, in stabilizing rare oxidation states of lanthanide ions, taking a part of intramolecular and molecular interactions stabilizing metal-oxygen cores and many others. This paper reports the synthesis and characterization of new lithium [Li4(OSiPh3)4(THF)2] (1), and sodium [Na4(OSiPh3)4] (2) species, which were later used in obtaining novel gadolinium [Gd(OSiPh3)3(THF)3]·THF (3), and erbium [Er(OSiPh3)3(THF)3]·THF (4) configuration, it can result in res were determined for all 1-4 compounds, and in addition, IR, Raman, absorption spectroscopy studies were conducted for 3 and 4 lanthanide compounds. Furthermore, direct current (dc) variable-temperature magnetic susceptibility measurements on polycrystalline samples of 3 and 4 were carried out in the temperature range 1.8-300 K. The 3 shows behavior characteristics for the paramagnetism of the Gd3+ ion. In contrast, the magnetic properties of 4 are dominated by the crystal field effect on the Er3+ ion, masking the magnetic interaction between magnetic centers of neighboring molecules.

Synthesis, Structural, and Cytotoxic Properties of New Water-Soluble Copper(II) Complexes based on 2,9-Dimethyl-1,10-Phenanthroline and Their One Derivative Containing 1,3,5-Triaza-7-Phosphaadamantane-7-Oxide.

A series of water-soluble copper(II) complexes based on 2,9-dimethyl-1,10-phenanthroline (dmphen) and mixed-ligands, containing PTA=O (1,3,5-triaza-7-phosphaadamantane-7-oxide) have been synthesized and fully characterized. Two types of complexes have been obtained, monocationic [Cu(NO3)(O-PTA=O)(dmphen)][PF6] (1), [Cu(Cl)(dmphen)2][PF6] (2), and neutral [Cu(NO3)2(dmphen)] (3). The solid-state structures of all complexes have been determined by single-crystal X-ray diffraction. Magnetic studies for the complex 1-3 indicated a very weak antiferromagnetic interaction between copper(II) ions in crystal lattice. Complexes were successfully evaluated for their cytotoxic activities on the normal human dermal fibroblast (NHDF) cell line and the antitumor activity using the human lung carcinoma (A549), epithelioid cervix carcinoma (HeLa), colon (LoVo), and breast adenocarcinoma (MCF-7) cell lines. Complexes 1 and 3 revealed lower toxicity to NHDF than A549 and HeLa cells, meanwhile compound 2 appeared to be more toxic to NHDF cell line in comparison to all cancer lines. Additionally, interactions between the complexes and human apo-transferrin (apo-Tf) using fluorescence and circular dichroism (CD) spectroscopy were also investigated. All compounds interacted with apo-transferrin, causing same changes of the protein conformation. Electrostatic interactions dominate in the 1/2 - apo- Tf systems and hydrophobic and ionic interactions in the case of 3.

Copper(II) Coordination Polymers Self-Assembled from Aminoalcohols and Pyromellitic Acid: Highly Active Precatalysts for the Mild Water-Promoted Oxidation of Alkanes.

Three novel water-soluble 2D copper(II) coordination polymers-[{Cu2(µ2-dmea)2(H2O)}2(µ4-pma)]n·4nH2O (1), [{Cu2(µ2-Hedea)2}2(µ4-pma)]n·4nH2O (2), and [{Cu(bea)(Hbea)}4(µ4-pma)]n·2nH2O (3)-were generated by an aqueous medium self-assembly method from copper(II) nitrate, pyromellitic acid (H4pma), and different aminoalcohols [N,N-dimethylethanolamine (Hdmea), N-ethyldiethanolamine (H2edea), and N-benzylethanolamine (Hbea)]. Compounds 2 and 3 represent the first coordination polymers derived from H2edea and Hbea. All the products were characterized by infrared (IR), electron paramagnetic resonance (EPR), and ultraviolet-visible light (UV-vis) spectroscopy, electrospray ionization-mass spectroscopy (ESI-MS(±)), thermogravimetric and elemental analysis, and single-crystal X-ray diffraction (XRD), which revealed that their two-dimensional (2D) metal-organic networks are composed of distinct dicopper(II) or monocopper(II) aminoalcoholate units and µ4-pyromellitate spacers. From the topological viewpoint, the underlying 2D nets of 1-3 can be classified as uninodal 4-connected layers with the sql topology. The structures of 1 and 2 are further extended by multiple intermolecular hydrogen bonds, resulting in three-dimensional (3D) hydrogen-bonded networks with rare or unique topologies. The obtained compounds also act as highly efficient precatalysts for the mild homogeneous oxidation, by aqueous H2O2 in acidic MeCN/H2O medium, of various cycloalkanes to the corresponding alcohols and ketones. Overall product yields up to 45% (based on cycloalkane) were attained and the effects of various reaction parameters were investigated, including the type of precatalyst and acid promoter, influence of water, and substrate scope. Although water usually strongly inhibits the alkane oxidations, a very pronounced promoting behavior of H2O was detected when using the precatalyst 1, resulting in a 15-fold growth of an initial reaction rate in the cyclohexane oxidation on increasing the amount of H2O from ∼4 M to 17 M in the reaction mixture, followed by a 2-fold product yield growth.

New Tetracopper(II) Cubane Cores Driven by a Diamino Alcohol: Self-assembly Synthesis, Structural and Topological Features, and Magnetic and Catalytic Oxidation Properties.

Two new coordination compounds with tetracopper(II) cores, namely, a 1D coordination polymer, [Cu4(µ4-H2edte)(µ5-H2edte)(sal)2]n·10nH2O (1), and a discrete 0D tetramer, [Cu4(µ4-Hedte)2(Hpmal)2(H2O)]·7.5H2O (2), were easily self-assembled from aqueous solutions of copper(II) nitrate, N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine (H4edte), salicylic acid (H2sal), or phenylmalonic acid (H2pma). The obtained compounds were characterized by IR and electron paramagnetic resonance spectroscopy, thermogravimetric and elemental analysis, and single-crystal X-ray diffraction. In addition to different dimensionalities, their structures reveal distinct single-open [Cu4(µ2-O)(µ3-O)3] (in 1) or double-open [Cu4(µ2-O)2(µ3-O)2] (in 2) cubane cores with 3M4-1 topology. In crystal structures, numerous crystallization water molecules are arranged into the intricate infinite 1D {(H2O)18}n water tapes (in 1) or discrete (H2O)9 clusters (in 2) that participate in multiple hydrogen-bonding interactions with the metal-organic hosts, thus extending the overall structures into very complex 3D supramolecular networks. After simplification, their topological analysis revealed the binodal 6,10- or 6,8-connected underlying 3D nets with unique or rare 6,8T2 topology in 1 and 2, respectively. The magnetic properties of 1 and 2 were investigated in the 1.8-300 K temperature range, indicating overall antiferromagnetic interactions between the adjacent Cu(II) ions within the [Cu4O4] cores. The obtained compounds also act as bioinspired precatalysts for mild homogeneous oxidation, by aqueous hydrogen peroxide at 50 °C in an acidic MeCN/H2O medium, of various cyclic and linear C5-C8 alkanes to the corresponding alcohols and ketones. Overall product yields of up to 21% (based on alkane) were achieved, and the effects of various reaction parameters were studied.

Trinuclear Cu(II) complexes of a chiral N6O3 amine.

Enantiopure trinuclear Cu(II) complexes 3 and 4 of macrocyclic amine 1 derived from the 3 + 3 condensation of 2,6-diformyl-4-methylphenol and (1S,2S)-1,2-diaminocyclohexane have been synthesized and characterized by ESI MS and NMR spectroscopy. The X-ray crystal structures of both complexes have been determined. The structure of the chloride derivative 3 indicates unusual combination of distorted tetragonal bipyramidal, square pyramidal and square geometries of the three Cu(II) ions bound by macrocycle 1. The acetate complex 4 also exhibits unsymmetrical trinuclear core with the bridging and terminal acetate anions. The complexation of Cu(II) ions by macrocycle 1 has been studied using potentiometric methods and both protonation and binding constants of 1 have been determined. The distribution of the complex forms indicates cooperative binding of three metal ions by 1. The overall magnetic behaviour for 3 corresponds to an antiferromagnetically coupled triangular system. Compound 4 shows the presence of antiferromagnetic coupling (J = -74.9(1) cm(-1)) between the metal centers in equilateral triangular array.

Trinuclear thiocyanate-bridged compounds of the type [ML]2[Mn(NCS)4](ClO4)2 (where M = Cu(II), Ni(II); L = N-dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene).

The complexes of general formula [ML]2[Mn(NCS)4](ClO4)2 (where M = Cu(II), Ni(II); L = N-dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) were obtained and the crystal structures of both heteronuclear compounds were determined at 173 K. Complex [CuL]2[Mn(NCS)4](ClO4)2 (1) crystallizes in a monoclinic space group, C2/c, with a = 41.297(9) A, b = 7.571(2) A, c = 16.417(4) A, beta = 96.97(15) degrees, Z = 8, whereas complex [NiL]2[Mn(NCS)4](ClO4)2.H2O (2) crystallizes in a monoclinic space group, P2/c, with a = 21.018(5) A, b = 7.627(2) A, c = 16.295(4) A, beta = 104.47(1) degrees, Z = 4. The magnetic behaviour of (1) and (2) has been investigated over the temperature range 1.8-300 K. Complex (1) displays ferromagnetic coupling inside the trinuclear core of CuMnCu and compound (2) behaves like a mononuclear Mn(II) system. The magnetic properties of the second compound (2) with a similar trinuclear structure shows that Ni(II) ions have a diamagnetic character and a rather weak zero-field splitting at the central Mn(II) ion occurs. Finally, the magnitudes of the Cu(II)-M(II) interactions with M = Ni and Mn have been compared and qualitatively justified.