EPR Spectral Studies of Manganese(I) Based Molecular Squares

Manganese(I) based molecular squares of type [Mn(CO)3Br(μ-L)]4 where L = pyrazine, 4,4′-bipyridine, trans-1,2-bis(4-pyridyl)ethylene were synthesized and studied in detail by EPR spectroscopy. The continuous wave electron paramagnetic resonance (CW EPR) spectrum of these compounds consists of a broad transition at g = 2.006 and 4.16 that corresponds to an interacting low spin Mn(II) center and a narrow transition at g = 2.004 that corresponds to a nitrogen center radical. These results are discussed in detail and the observation of these characteristic EPR spectral signals is attributed to a partial transfer of an electron from Mn(I) center to the nitrogenous ligand through MLCT.