Dimers magnetic properties

Fig. 3 Magnetic properties and molecular structure of the dimeric species [Fe(H2 0)4]2(bpym) (S04)2 (adapted from [3])... 

With bidentate SBs, monomeric [VO(SB)2] complexes are normally formed. On the contrary, with tridentate dibasic SBs, dimeric species often form. It appears that the dibasic character of the ligands forces the VOz+ ion to dimerize leading to anomalous magnetic properties. Proposed structures have not been verified owing to their non-crystalline nature. Insolubility precluded molecular weight determinations and ESR and electronic spectral studies have been carried out in the solid state only. 

The synthesis and characterization of V02+ complexes of hydrazones (94) and (95) derived from benzoylhydrazine and o-hydroxy aromatic aldehydes and ketones were also reported772 and molecular weight determinations, IR, electronic spectra and magnetic properties were explained assuming a dimeric structure (96) with each unit having a five-coordinate square pyramidal geometry. 

In an early publication, Zelentsov reported the preparation of a complex with subnormal magnetic properties 44 = 0.87 BM) with the SB (101).777 The compound was prepared from dibenzoylmethane and o-aminophenol. The V02+ complex with (102) has also been shown to be involved in antiferromagnetic exchange with J = —139 cm-1. Revenko and Gerbeleu prepared several V02+ complexes of (103) derived from Hsal and thiosemicarbazide which were reported to involve ONS coordination.778 The measured were 1.27, 1.21 and 1.33 BM for R = H, Cl and Br, respectively. The complexes are not anhydrous and a dimeric structure (104) was proposed. 

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