Manganese (I) complexes of p-xylene and [2n] cyclophanes from a theoretical sight

Theoretical B3LYP/6-311G** calculations were performed in order to understand the electronic structure and the structural behavior of bis(p-xylene) and bis([2,2]-p-cyclophane) manganese (I) complexes. The minimum energy configuration of bis(p-xylene) has D2d symmetry while that of bis([2,2]-p-cyclophane) has D2 symmetry. The energy difference between the D2d and the D2h structures for both compounds is small. The results of the calculation for the pseudorotational barrier indicate that a process of interconversion may be possible. A comparison between experimental and theoretical infrared spectra was done for bis(p-xylene) Mn(I). Theoretical and experimental spectra are in good agreement. For both compounds, the HOMO has a big contribution from the metal orbital. In bis([2,2]-p-cyclophane) manganese (I) the HOMO and HOMO-1 form a bridge between the rings, this can explain some of the electric flow. Much of the evidences that we present in this work, indicates that transannular electronic interaction for bis([2,2]-p-cyclophane) manganese (I) is present.