Ligand Rotation Induced Oxidation State Change and Spin Appearance of the Bis(phthalocyaninato)cerium (CePc₂) Molecule on the Au(111) Surface

Abstract

We demonstrate that a nonmagnetic molecule is changed into magnetic when its internal structure is rotated by forming an ordered film on a metal surface. We used a double-decker complex, bis­(phthalocyaninato)­cerium (CePc2), where the valence of the Ce atom changes between +3 and +4 with a small energy barrier. CePc2 is nonmagnetic in bulk and becomes magnetic in the monolayer film on Au(111). The intra-molecular structure and the magnetic property are revealed using scanning tunneling microscopy/spectroscopy. We attribute the mechanism to a change of the rotational angle (θ) between the upper and lower Pc ligands, driven by the steric repulsive force originating from forming an almost square lattice on Au(111). The θ changes from θ = 45° of the bulk value into θ = 0° for the film. GGA + U calculation indicates that the change from θ = 45° to θ = 0° causes the Ce valence change from the nonmagnetic +4 state into the magnetic +3 state.

Spin dynamics phenomena of a cerium(iii) double-decker complex induced by intramolecular electron transfer

“…Complexes 1 and 2 were prepared according to previously reported literature procedures. 48,[51][52][53] Synthesis of TBA + [Ce(obPc The following was performed to obtain a single crystal. A mixture of Ce(obPc) 2 (0.78 mg), DMSO (0.58 mL), and N 2 H 4 •H 2 O (0.02 mL) was heated at 120 °C for 1 h, affording a blue solution of the anionic double-decker complex ([Ce (obPc) 2 ] − ).…”

“…This observation implies that IET can be regulated through the manipulation of the interface. 53,87 XAFS allows element-selective measurements, from which information on the local structure and electronic states can be obtained. XAFS spectra are analysed in the energy region from the absorption edge, divided into XANES (from the absorption edge to about 50 eV) and EXAFS (from the XANES region to about 1000 eV).…”

“…ESI-MS: m/z 1164.20 [M + ] (calcd.1164.21)". 53 The cerium(III) double-decker complex TBA + [Ce(Pc) 2 ] − (2) was prepared by adding Ce(Pc) 2 (78 mg, 0.067 mmol) and 1.2 mL of N 2 H 4 •H 2 O to 30 mL of DMSO, heating to boiling with a heat gun, and sonicating for 30 min until the green neutral form completely disappeared to afford a blue solution, which is the colour of the anionic form [Ce(Pc) 2 ] − . TBA•Br (600 mg) was added to the above solution, and then the solution was heated with a heat gun and sonicated for 30 min.…”

“…Furthermore, proton switching, 102 dimerization, [103][104][105] fullerene co-crystals, 106 and one-dimensional expansion approaches 10,107 by regulating the coordination geometries and intermolecular interactions are conceivable. 108 The spin dynamics of a Ce ion can be altered by adjusting the interactions between conduction electrons (holes) due to molecular orbital overlap 53 and the interactions between frontier orbitals and Ce f orbitals induced by the distortions of the π-conjugated porphyrinoids with electrondonating substituents.…”