Molecular structure and spectral properties of mono- and dinuclear complexes formed by manganese(II), 2,6-dimethoxybenzoate and 2,2'-bipyridineor 2-methylpyrazine

Article abstract of DOI:10.1016/0020-1693(95)04638-P

The adducts formed by reaction of [Mn(dmb)2(H2O)3]n*nH2O, dmb=2,6-dimethoxybenzoato(1-), with 2,2'-bipyridine (bpy) or 2-methylpyrazine (2-Mepz) were isolated in the solid state and characterized by single crystal X-ray diffraction, IR and EPR spectroscopy, and thermogravimetry. The adduct [Mn2(dmb)4(bpy)2(H2O)2]*bpy crystallizes in the monoclinic space group P21/n, with a=15.983(4), b=11.048(4), c=17.682(4)?, β=97.66(3)°, V=3094.4(16)?**3, Z=2 and D(calc)=1.415 g*cm**-3. The complex exhibits a dinuclear structure where two manganese(II) atoms sharetwo carboxylate groups adopting a rather uncommon single-atom bridging mode. The coordination at each metal nucleus is completed by a further carboxylate group, acting as a monodentate donor, a water molecule and a chelating bidentate bipyridine molecule. The crystals of the adduct [Mn(dmb)2(2-Mepz)2(H2O)2] are monoclinic, space group P21/n, with a=8.024(3), b=10.314(3), c=18.289(4)?, β=94.72(3)°, V=1508.5(8)?**3, Z=2 and D(calc)=1.412 g*cm**-3. The compound is mononuclear and consists of hexacoordinate ions bound to trans-pairs of monodentate carboxylates, water molecules and nitrogenous base molecules. The bpy adduct exhibits EPR spectra distinctive of magnetically coupled dimanganese(II)units.