Simulation strategies for unusual EPR spectra of binuclear mixed-valence manganese complexes: synthesis, properties, and x-ray structures of the MnIIMnIII complexes [Mn2(bpmp)(.mu.-OAc)2](ClO4)2.cntdot.H2O and [Mn2(bcmp)(.mu.-OAc)2](ClO4)2.cntdot.CH2Cl2