EXAFS AND MAGNETIC STUDIES OF 2 NEW MIXED-VALENCE HEXANUCLEAR MANGANESE COMPLEXES OF FORMULA [MN6O2(X-BENZOATO)(10)(ETOH)(4)] (X=2-CL AND 3-CL) - COMPARISON WITH THE BENZOATE ANALOG

Two new mixed-valence hexanuclear manganese complexes of formula [Mn6O 2(X-benzoato)(10) (EtOH)(4)] being X = 2-Cl and 3-Cl have been synthes ized and characterized by elementary analysis and X-ray absorption mea surements which were compared with the benzoate analogue, whose X-ray structure has been previously reported. The analysis of XANES and EXAF S spectra indicates that the core of the two new hexanuclear complexes is almost identical to the benzoate derivative, consisting of two Mn4 O tetrahedra that share an edge giving a global formula of Mn6O2. The two manganese ions shared in these tetrahedra are Mn-III and the four nonshared manganese ions are Mn-II. Magnetic susceptibility measuremen ts from room temperature to 4 K have been made for the two complexes t ogether with the benzoate analogue. In the three cases there is a clea r global antiferromagnetic coupling giving a ground state S = 0.