New tricopper(ii) cores self-assembled from aminoalcohol biobuffers and homophthalic acid: synthesis, structural and topological features, magnetic properties and mild catalytic oxidation of cyclic and linear C5–C8 alkanes

Two new compounds with distinct tricopper(ii) cores were synthesised and applied as bio-inspired pre-catalysts for mild oxidation of alkanes.

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.

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.

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 d_x²-y².

Tetranuclear copper(ii) cubane complexes derived from self-assembled 1,3-dimethyl-5-(o-phenolate-azo)-6-aminouracil: structures, non-covalent interactions and magnetic property

A new doubly opened 4 + 2 Cu₄O₄ cubane cluster exhibits strong antiferromagnetic exchange coupling with J₁ = −110.1 cm⁻¹, and J₂ = −27.1 cm⁻¹.