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ACS Omega ; 4(15): 16450-16461, 2019 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-31616823


The unusual temperature behavior of the electron spin resonance (ESR) spectra and magnetic properties are experimentally observed in copper(II) complexes with a dendritic ligand based on the Boltorn H30 polymer (Perstorp Specialty Chemicals AB, Sweden) functionalized with fumaric acid residues in a molar ratio of 1:6. The ESR spectra at low temperatures show signs of transition to higher spin states at temperatures below 8-10 K, and the temperature dependences of the integral ESR signal intensities and magnetic susceptibility show the positive deviation from the Curie-Weiss law, thereby pointing to the presence of ferromagnetic exchange interactions in the system under study. The values of the exchange interaction parameters are calculated by quantum-chemical simulation of the possible structure of the copper(II) complex when assuming the formation of trinuclear coordination sites embedded in the hyperbranched polymer structure. The results of density functional theory calculations indicate the possibility of ferromagnetic exchange through carboxylate bridges in the trinuclear magnetic clusters, and the calculated values of the exchange interaction parameters make it possible to construct theoretical curves of the temperature dependence of the effective magnetic moment, which satisfactorily fit the experimental data, especially considering that polymers are characterized by disperse molecular weights and chemical structures.

Dalton Trans ; 48(35): 13413-13422, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31433418


Novel heteroleptic Er(iii) and Yb(iii) naphthalocyaninato-phthalocyaninates containing an octa-phenyl or octa-phenoxysubstituted naphthalocyanine deck were synthesised and identified by 1H NMR, EPR and high resolution MALDI-TOF/TOF mass spectrometry. Direct synthesis of novel homoleptic Yb(iii) bis (octa-phenylnaphthalocyaninate) was carried out. Downfield lanthanide induced shifts of the aromatic protons in target compounds were observed compared with the corresponding diamagnetic Lu(iii) complexes. In the near-IR absorption spectra, an increase in ionic radius from Lu(iii) to Er(iii) resulted in a bathochromic shift of the intervalence band up to 1473 nm. This work presents the first experimental EPR study of Yb(iii) bis naphthalocyaninate, where a set of magnetic parameters and properties (including spin, magnitude and sign of magnetic anisotropy parameter D, increased splitting in a crystal field, ferromagnetic f-π interaction etc.) were determined and interpreted by both EPR and SQUID techniques and supported by theoretical considerations.

Chem Asian J ; 14(17): 2979-2987, 2019 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-31298502


New nickel-based complexes of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with BF4 - counterion or halide co-ligands were synthesized in THF and MeCN. The nickel(I) complexes were obtained by using two approaches: 1) electrochemical reduction of the corresponding nickel(II) precursors; and 2) a chemical comproportionation reaction. The structural features and redox properties of these complexes were investigated by using single-crystal X-ray diffraction (XRD), cyclic voltammetry (CV), and electron paramagnetic resonance (EPR) and UV/Vis spectroscopy. The influence of temperature and solvent on the structure of the nickel(I) complexes was studied in detail, and an uncommon reversible solvent-induced monomer/dimer transformation was observed. In the case of the fluoride complex, the unpaired electron was found to be localized on the dpp-bian ligand, whereas all of the other nickel complexes contained neutral dpp-bian moieties.