The first pentagonal-bipyramidal vanadium( iii ) complexes with a Schiff-base N 3 O 2 pentadentate ligand: synthesis, structure and magnetic properties

• Published in: Dalton transactions : an international journal of inorganic chemistry 2020-11, Vol.49 (43), p.15287-15298
• Main Authors: Bazhenova, Tamara A., Zorina, Leokadiya V., Simonov, Sergey V., Mironov, Vladimir S., Maximova, Olga V., Spillecke, Lena, Koo, Changhyun, Klingeler, Rüdiger, Manakin, Yuriy V., Vasiliev, Alexander N., Yagubskii, Eduard B.
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/D0DT03092A

A series of three mononuclear pentagonal-bipyramidal V( iii ) complexes with the equatorial pentadentate N 3 O 2 ligand (2,6-diacethylpyridinebis(benzoylhydrazone), H 2 DAPBH) in the different charge states (H 2 DAPBH 0 , HDAPBH 1− , DAPBH 2− ) and various apical ligands (Cl − , CH 3 OH, SCN − ) were synthesized and characterized structurally and magnetically: [V(H 2 DAPBH)Cl 2 ]Cl·C 2 H 5 OH ( 1 ), [V(HDAPBH)(NCS) 2 ]·0.5CH 3 CN·0.5CH 3 OH ( 2 ) and [V(DAPBH)(CH 3 OH) 2 ]Cl·CH 3 OH ( 3 ). All three complexes reveal paramagnetic behavior, resulting from isolated S = 1 spins with positive zero-field splitting energy expected for the high-spin ground state of the V 3+ (3d 2 ) ion in a PBP coordination. Detailed high-field EPR measurements for compound 3 show that its magnetic properties are best described by using the spin Hamiltonian with the positive ZFS energy ( D = +4.1 cm −1 ) and pronounced dimer-like antiferromagnetic spin coupling ( J = −1.1 cm −1 ). Theoretical analysis based on superexchange calculations reveals that the long-range spin coupling between distant V 3+ ions (8.65 Å) is mediated through π-stacking contacts between the planar DAPBH 2− ligands of two neighboring [V(DAPBH)(CH 3 OH) 2 ] + complexes.