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We report the synthesis, crystal structure and magnetic properties of the new heptacoordinated mononuclear erbium(III) complex (Et3NH)[Er(H2DAPS)Cl2] (H4DAPS = 2,6-diacetylpyridine bis-(salicylhydrazone)) (1). The coordination polyhedron around the Er(III) ion features a slightly distorted pentagonal bipyramid formed by the pentagonal N3O2 chelate ring of the H2DAPS ligand in the equatorial plane and two apical chloride ligands. Detailed high-frequency/high-field electron paramagnetic resonance (HF-EPR) studies of 1 result in the precise determination of the crystal field (CF) splitting energies (0, 290 and 460 GHz) and effective g-values of the three lowest Kramers doublets (KDs) of the Er(III) ion. The obtained HF-EPR data are in good agreement with the results from CF analysis for the Er(III) ion based on the simulation of the dc magnetic data of 1. The results from dynamic susceptibility measurements indicate that there is no slow relaxation of magnetisation behaviour. This observation is discussed in terms of the electronic structure of 1 obtained from experimental and theoretical results. [ABSTRACT FROM AUTHOR]

A series of three mononuclear pentagonal-bipyramidal V(III) complexes with the equatorial pentadentate N3O2 ligand (2,6-diacethylpyridinebis(benzoylhydrazone), H2DAPBH) in the different charge states (H2DAPBH0, HDAPBH1−, DAPBH2−) and various apical ligands (Cl−, CH3OH, SCN−) were synthesized and characterized structurally and magnetically: [V(H2DAPBH)Cl2]Cl·C2H5OH (1), [V(HDAPBH)(NCS)2]·0.5CH3CN·0.5CH3OH (2) and [V(DAPBH)(CH3OH)2]Cl·CH3OH (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 V3+ (3d2) 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 V3+ ions (8.65 Å) is mediated through π-stacking contacts between the planar DAPBH2− ligands of two neighboring [V(DAPBH)(CH3OH)2]+ complexes. [ABSTRACT FROM AUTHOR]

The interaction of Cu(II) with the following secondary N-substituted derivatives of di(2-picolyl)amine (1) are reported: N-cyclohexylmethyl-di(2-picolyl)amine (2), N-benzyl-di(2-picolyl)amine (3), N-(4-pyridylmethyl)-di(2-picolyl)amine (4), N-(4-carboxymethylbenzyl)-di(2-picolyl)amine (5), N-(9-anthracen-8-ylmethyl)-di(2-picolyl)amine (6), 1,3-bis[di(2-picolyl)aminomethyl]benzene (7), 1,4-bis[di(2-picolyl)aminomethyl]benzene (8) and 2,4,6-tris[di(2-picolyl)amino]triazine (9). The solid complexes [Cu(2)(μ-Cl)]2(PF6)2, [Cu(3)(μ-Cl)]2(PF6)2·0.5CH2Cl2, Cu(4)(ClO4)2, Cu(5)2(ClO4)2, [Cu(6)(ClO4)2(H2O)]·0.5H2O, Cu2(7)(ClO4)4, [Cu2(8)(Cl)4] and [Cu2(9+H)(μ-OCH3)2(H2O)](ClO4)3·C4H10O were isolated and X-ray structures of [Cu(2)(μ-Cl)]2(PF6)2, [Cu(3)(μ-Cl)]2(PF6)2·0.5CH2Cl2,[Cu(6)2(ClO4)2(H2O)]·0.5H2O, [Cu2(8)Cl4] and [Cu2(9+H)(μ-OCH3)2(H2O)](ClO4)3·C4H10O were obtained. The series is characterised by a varied range of coordination geometries and lattice architectures which in the case of [Cu(6)(ClO4)2(H2O)]·0.5H2O includes a chain-like structure formed by unusual intermolecular π-interactions between metal bound perchlorate anions and the aromatic rings of adjacent anthracenyl groups. Variable temperature magnetic susceptibility measurements have been performed for [Cu(2)(μ-Cl)]2(PF6)2and [Cu(3)(μ-Cl)]2(PF6)2·0.5H2O over the range 2–300 K. Both compounds show Curie-Weiss behaviour, with the data indicating weak antiferromagnetic interaction between the pairs of copper ions in each complex. Liquid–liquid (H2O/CHCl3) extraction experiments involving 1–3and 7–9as extractants showed that, relative to the parent (unsubstituted) dipic ligand 1, substitution at the secondary amine site in each case resulted in an increase in extraction efficiency towards Cu(II) (as its perchlorate salt); at least in part, this increase may be attributed to the enhanced lipophilicities of the N-substituted derivatives. [ABSTRACT FROM AUTHOR]