Joseph K. Koka / Elixir Appl. Chem. 126 (2019) 52487-52494 52487 1.0 Introduction Gas phase chemistry of ions provides important insight into the reactivity, thermochemistry, reaction mechanisms, and structures of ions without the added complexity of solvent. Although a lot of work has been done both theoretically and experimentally on metal-benzene complexes very little if not at all is focused on activation of methane with manganese-benzene complexes. Literature revealed that Soteras et al has theoretically investigated the structural and electronic effects of the interaction of six singly charged metal cations including manganese with benzene [1]. Kurikawa et al in the gas-phase produced, neutral metal−benzene complexes, M n (benzene) m (M = Sc to Cu), using a laser vaporization method and characterized them by mass spectrometry, photoionization spectroscopy, and chemical probe experiments [2]. The neutral (M n Bz n+1 ) was studied by Miyajima et al using magnetic deflection approach [5] including vanadium−benzene organometallic complexes V n (C 6 H 6 ) m produced by a laser vaporisation synthesis method [22]. Xiang et al theoretically studied the electronic and magnetic properties for MBz polymers with M=Sc, Ti, V, Cr, and Mn has shown that all chains, except CrBz are metallic [3] Martínez et al in their work presented first-principle calculations of photoabsorption of cross sections of M n Bz n+1 sandwiches with M=Ti, V, Cr, and n ≤ 3 [4]. While Ravindra et al, studied the electronic Structure and Properties of Transition Metal−Benzene Complexes and observed that the variation of the metal−benzene distances, dissociation energies, ionization potentials, electron affinities, and spin multiplicities across the 3d series in MBz complexes differs qualitatively from those in M(Bz) 2 [6]. Again, Miyajima et al by a laser vaporization synthesis method produced metal−benzene organometallic clusters M n (C 6 H 6 ) m (M = Al, Sc, Ti, and V) [7]. Willey et al using laser vaporization investigated photodissociation dynamics, spectroscopy and binding energies of metal ion-benzene complexes [8]. Meyer et al by collision–induced dissociation with Xe guided beam tandem mass spectrometer determined the sequential bond energies of the mono–bis benzene complexes of the first row transition metal ions M + =Ti + -Cu + [9]. Binding energies were successfully estimated for the complexes of benzene with the first-row transition-metal ions (M + = Ti + −Cu + ) via both kinetic modeling and quantum chemical simulation [10]. Hongming et al using maximally localized wannier functions analysed details of closely related materials, single benzene (Bz) molecule, organometallic vanadium-Bz infinite chain, and V 2 Bz 3 sandwich cluster [11]. Jaeger et al by the application of laser vaporization produced Ni + (benzene) n (n = 1−6) and Ni + (benzene) n (n = 1,2) [12] and further produced metal−benzene complexes of the form M(benzene) n (M = Ti, V, Fe, Co, Ni) [13]. Despite the fact that carbon dioxide is typically painted as the bad boy of greenhouse gases and its emissions are five times greater than methane, they are similarly problematic because methane is roughly 25 times the global warming potential of carbon dioxide [18]. Recent calculations suggest that atmospheric CH 4 emissions have been responsible for approximately 20% of Earth’s warming since pre-industrial times [21]. Hence any large-scale chemical conversion of methane into other valuable and/or environmentally friendly chemical compounds would have a remarkable impact on the climate. Bis benzene manganese dication complex ions [Mn(Benzene) 2 ] 2+ were formed in the gas phase and activated with methane. Tele: +233241727668 E-mail address: jkoka1@ucc.edu.gh © 2019 Elixir All rights reserved ARTICLE INFO Article history: Received: 28 November 2018; Received in revised form: 01 January 2019; Accepted: 11 January 2019; Keywords Binding Energy, Methane, Manganese, Benzene, Dication. Binding energy of Methane with Metal Dication Complex ion [Mn(benzene) 2 ] 2+ in the Gas Phase Joseph K. Koka School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom. School of Physical Science, Department of Chemistry, University of Cape Coast, Ghana. ABSTRACT 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 CH 4 ] 2+ , [Mn(Benzene) 2 (CH 4 ) 2 ] + , [Mn(Benzene) 2 (CH 4 ) 2 H 2 O)] + and [Mn(Benzene) 2 CO 2 (CH 3 ) 2 ] + were successfully identified after the experimental analysis. Two optimised geometries of [Mn(Benzene) 2 ] 2+ were observed, namely the C 2V eclipse and C 2 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 CH 4 ] 2+ was 1.30 while a charge of Mn=2.0 was assumed in the PEC calculation. © 2019 Elixir All rights reserved. Elixir Appl. Chem. 126 (2019) 52487-52494 Applied Chemistry Available online at www.elixirpublishers.com (Elixir International Journal)