Field-assisted slow relaxation of magnetization in Cu() complexes with pentaheterocyclic triphenodioxazine ligands: the quasi-one-dimensional the binuclear case

• Published in: New journal of chemistry 2023-11, Vol.47 (46), p.21353-2136
• Main Authors: Korchagin, D. V, Ivakhnenko, E. P, Demidov, O. P, Knyazev, P. A, Efimov, N. N, Morgunov, R. B, Starikov, A. G, Palii, A. V, Minkin, V. I, Aldoshin, S. M
• Format: Article
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d3nj04614a

Two new copper( ii ) complexes have been obtained by the reaction of sterically crowded triphenodioxazine ligands with Cu( ii ) hexafluoroacetylacetonate. Compound 1 is a co-crystal of Cu(hfac) 2 moieties and triphenodioxazine molecules within a quasi-one-dimensional crystal structure with only weak Cu N short intermolecular interactions (Cu N distances are equal to 2.69(1) and 2.75(1) Å). In contrast, complex 2 has a binuclear structure with two Cu(hfac) 2 units bridged through triphenodioxazine ligand with the covalent Cu-N bond length of 2.335(2) Å. The magnetic AC susceptibility data show that in spite of the absence of zero-field splitting in the Cu( ii ) ion having the ground state with spin S = 1/2, both compounds demonstrate slow magnetic relaxation at the applied magnetic field. For a quasi-one-dimensional complex 1 , the optimal field for observing slow magnetic relaxation is 400 Oe, while for the binuclear complex it is 2500 Oe. The observed temperature dependence of the relaxation time in 1 is well described by the combination of Raman and direct mechanisms of relaxation, while for complex 2 the inclusion of Raman mechanism and quantum tunneling of magnetization is required to describe the relaxation behavior. Cu( ii ) hexafluoroacetylacetonate with triphenodioxazine ligands gives complexes with different crystal structures and magnetic properties.