Stability of one- and two-layers [TM(Benzene)(m)](+/- 1), m <= 3; TM = Fe, Co, and Ni, complexes
The structural and energetic properties for neutral and charged complexes of transition metal atoms and benzene molecules, TM(C6H6)(m) (<=) (3), TM = Fe, Co, Ni, were studied using density functional theory. Including dispersion corrections all-electron calculations were done with the BPW91-D2 and M11L functionals. Basis sets of 6-311++G(2d,2p) and Def2TZVP quality were employed. Binding energies, D-0, ionization energies, IE, and electron affinities, EA, were determined for the located ground states. Structural and electronic parameters accounting for the stability of TM(C6H6)(m) were also addressed. Metal-carbon (eta(2)-eta(6)) coordination occur in the neutral arid positively charged TM(C6H6)(1,2) species. But in the Co-C6H6 and Ni-C6H6 ions the metal atom seats on two hydrogen atoms,eta(2)(H), of the benzene ring, with the peculiarity that the ground state geometries are planar. In the neutral and charged TM(C6H6)(3), TM = Fe, Co and Ni species a benzene molecule lies in the external region and by means of CH-pi and pi -pi stacking interactions it is bonded to the ligands lying in the first coordination layer. Although weak, some external molecules present direct interactions with the metal atom. The D-0 for the molecules in the outer region is much smaller than the one for the ligands in the first layer. Therefore, solvent behavior is exhibited by the studied neutral and charged [TM(C6H6)(3)](+/- 1) complexes. Experiment and theory agree that: D-0(Fe+(C6H6)(2)) > D-0(Co+(C6H6)(2)) > D-0(Ni+C6H6)(2)) and D-0(NiC6H6) > D-0(CoC6H6). Reasonable accuracy was found for the D-0 of each complex; other tendencies are not fully reproduced at these levels of theory. The small D-0's of CoC6H6 and NiC6H6 and those of the anions, complicate their determination. In general, the EA increases from m =1 to 2 and from 2 to 3. The IE decreases from m =1 to 3, being due to delocalization trough the C delta-H delta+center dot center dot center dot pi network of bonds. (C) 2016 Elsevier B.V. All rights reserved.