Binding Energy of Methane with Metal Dication Complex Ion [Mn(BENZENE)2]2+ in the Gas Phase

A theoretical and experimental study on [Mn(Benzene)2]2+ has been undertaken in the gas phase. The ions were prepared using a combination of the pick-up technique and high energy electron impact, and then held in a cold ion trap where they were excited with tuneable UV radiation and further activated with methane. The following [Mn(Benzene)2 CH4]2+, [Mn(Benzene)2(CH4)2]+, [Mn(Benzene)2(CH4)2H2O)]+ and [Mn(Benzene)2CO2(CH3)2]+ were successfully identified after the experimental analysis. Two optimised geometries of [Mn(Benzene)2]2+ were observed, namely the C2V eclipse and C2 staggered . The DFT calculated binding energy of methane to manganese benzene dication complex ion [Mn(Benzene)2]2+ at BP86/6- 311++G(d, p) is 15.30 kJ/mol comparing with the calculated 20.55 kJ/mol recorded on the potential energy curve (PEC). The difference of about 5.25 kJ/mol results from the fact that the calculated charge on the manganese metal centre at the optimised geometry of [Mn(Benzene)2 CH4]2+ was 1.30 while a charge of Mn=2.0 was assumed in the PEC calculation