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

Theoretical B3LYP/6-311G** calculations were performed in order to understa nd the electronic structure and the structural behavior of bis(p-xylene) an d bis([2,2]-p-cyclophane) manganese (I) complexes. The minimum energy confi guration of bis(p-xylene) has D-2d symmetry while that of bis([2,2]-p-cyclo phane) has D-2 symmetry. The energy difference between the D-2d and the D-2 h structures for both compounds is small. The results of the calculation fo r the pseudorotational barrier indicate that a process of interconversion m ay be possible. A comparison between experimental and theoretical infrared spectra was done for bis(p-xylene) Mn(I). Theoretical and experimental spec tra are in good agreement. For both compounds, the HOMO has a big contribut ion from the metal orbital. In bis([2,2]-p-cyclophane) manganese (I) the HO MO and HOMO-I form a bridge between the rings, this can explain some of the electric how. Much of the evidences that we present in this work, indicate s that transannular electronic interaction for bis([2,2]-p-cyclophane) mang anese (I) is present. (C) 2000 Published by Elsevier Science S.A. All right s reserved.