Photoelectron spectroscopy and theoretical studies of [Com(pyrene)n]− (m=1,2 and n=1,2) complexes

Abstract

Anion photoelectron spectroscopic experiments and density functional theory based calculations have been used to investigate the structural, electronic, and magnetic properties of neutral and anionic [Co(m)(pyrene)(n)] (m,n=1-2) complexes. The calculated electron affinities and vertical transition energies of Co(m)(pyrene)(n) are in good agreement with the measured values. Our results provide clear evidence for dimerization of Co atoms and formation of sandwich structures in these complexes. While the calculated spin magnetic moments of neutral Co(2)(pyrene)(n) complexes suggest a preference for ferromagnetic coupling between Co atoms, the spin magnetic moment of Co atom in Co(pyrene) and Co(pyrene)(2) complexes was reduced to 1mu(B).

Photoelectron spectroscopic study of iron-pyrene cluster anions

“…In the case of Isomer-1, the doublet spin state (2S + 1 = 2) is 0.30 eV higher in energy, while in Isomer-2, the doublet is 0.56 eV higher in energy than their corresponding quartet spin states. The lowest energy isomer of [Fe 1 (pyrene) 1 ] − cluster is similar to that of the previously reported 49 Co(pyrene) − cluster. Since, the energy difference between the two isomers of the anion is within the computational uncertainty (∼0.20 eV); the electron verti-cal detachment energies were calculated for both the isomers.…”

“…Thus, both Isomer-1 and Isomer-2 are contributing towards the photoelectron spectrum of [Fe 1 (pyrene) 1 ] − cluster indicating that both these isomers are present in the anion cluster beam. It is to be noted here that presence of multiple isomers has been reported in our earlier studies 42,49 of Fe(coronene) and Co(pyrene) clusters. The lowest energy isomer of neutral Fe 1 (pyrene) 1 cluster is similar to that of its anionic counterpart, albeit with a weaker Fe-pyrene interaction.…”

“…The convergence for total energy and gradient were set to 10 −9 Hartree and 10 −4 Hartree/Å, respectively. The accuracy and reliability of our basis set has been established in our previous studies 41,42,49 on various metal-organic complexes. The stabilities of the lowest energy isomers found in this work have been verified by carrying out vibrational frequency calculations.…”

“…Many experimental and theoretical studies have provided information regarding the interactions between various transition metals and organic ligands, such as benzene, pyridine, 22 fullerene (C 60 ), 6,15,[23][24][25][26][27][28][29][30][31] coronene, 15,[32][33][34][35][36][37][38][39][40][41][42] cyclooctatetrene (COT), 6,43,44 and pyrene. 37,45,46,49 Most of these studies have focused on characterizing the bonding between the d-electrons in the subject transition metals and the πelectrons of the organic ligands. Since the per atom magnetic moments of transition metal clusters are often larger than those exhibited by the same metal in its condensed state, 47 organic ligands may be able to help some metal clusters retain their high per atom magnetic moments, and this could lead to the synthesis of novel magnetic materials.…”

“…Recently, a joint experimental and theoretical study was reported by the current authors focusing on the geometrical and electronic structures as well as the magnetic properties of Co m (Pyrene) n clusters. 49 In the present paper, we report the photoelectron spectroscopic study of the negatively charged [Fe m (pyrene) n ] − (m = 1-2; n = 1-2) complexes. A comparison between the results of this work and our previous studies of iron-benzene and iron-coronene complexes assists in building a fuller picture of the interaction between the iron atoms/clusters and aromatic hydrocarbon networks.…”