Electronic structure and metal-metal interaction in edge- and face-sharing bioctahedral compounds of molybdenum

Ab initio configuration interaction calculations have been performed for the title compounds to study the nature of the metal-metal interaction. By analyzing the energy diagrams and the CI wave functions, it can be shown that the metal-metal interaction in such compounds has a dual nature, namely, formation of some direct metal-metal bonds and antiferromagnetic coupling of remaining electron pairs. Experimental observations of the magnetic behavior of the compounds can be explained satisfactorily by the calculated energy diagrams which include low-lying magnetic excited states as the result of the weak exchange coupling.