Publication in Dalton Transactions

The 17-membered piperazine-based macrocyclic ligand LdiProp (1,5,13,17,22-pentaazatricyclo[15.2.2.17,11]docosa-7,9,11(22)-triene) was resynthesized in high yield with help of linear pump. Its Mn(II), Fe(II), Co(II) and Ni(II) complexes of general formula [MnLdiProp(ClO4)2] (1), [FeLdiProp(CH3CN)](ClO4)2 (2), [CoLdiProp(CH3CN)](ClO4)2 (3), [NiLdiProp](ClO4)2 (4) were prepared and thoroughly characterized. X-ray diffraction analysis confirmed that Mn(II) complex 1 has capped trigonal prismatic geometry with coordination number seven, Fe(II) and Co(II) complexes 2 and 3 are trigonal prismatic with coordination number six and Ni(II) complex 4 has square pyramidal geometry with coordination number five. The decrease of coordination number is accompanied by a shortening of M–N distances and an increase of torsion of piperazine ring from the equatorial plane. Magnetic measurement reveal moderate for 4 and rather large magnetic anisotropy for 2 and 3 (axial zero-field splitting parameter D(Ni) = 9.0 cm–1, D(Fe) = –14.4 cm–1, D(Co) = –25.8 cm–1, together with rather high rhombicity). Co(II) complex 3 behaves as field-induced SMM with a combination of Raman and direct or Orbach and direct relaxation mechanisms. Obtained magnetic data were extensively supported by theoretical CASSCF calculations. The flexibility and rather large 17-membered macrocyclic cavity of ligand LdiProp could be responsible for the variation of coordination numbers and geometries for investigated late-first row transition metals.

 

 

Date: 8. jul 2020 | Author: agch

Department of Inorganic Chemistry

Faculty of Science
Palacký University in Olomouc

17. listopadu 12
CZ-771 46 Olomouc
Czech Republic

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email : agch(at)upol.cz