Direct Synthesis of Vanadium Phthalocyanine and Its Electronic and Magnetic States in Monolayers and Multilayers on Ag(111)

Abstract

Vanadium phthalocyanine (VPc) monolayers and multilayers were synthesized on Ag(111), and the electronic and magnetic states of an unachieved VPc with a divalent state of V were investigated. The VPc monolayer was fabricated by directly depositing the V atoms on a metal-free phthalocyanine (H 2 Pc) monolayer under ultrahigh-vacuum conditions. The VPc multilayer was synthesized by repeated VPc monolayer deposition and subsequent sample annealing at approximately 450 K. The N 1s X-ray photoelectron spectra (XPS) of these samples showed a remarkable reduction in the peak assigned to H-bonded N atoms, concomitant with the appearance of a new peak attributed to V-bonded N atoms close to the peak of iminic N. Additionally, the oxidation state of V estimated from the V 2p XPS peak position corresponded to 1.6 and 2.4 in the monolayer and multilayer samples, respectively. These results clearly imply that VPc monolayers and multilayers were successfully obtained. The main ground-state electronic configuration of the V center was found to be 2 E g by angle-dependent V L-edge X-ray absorption spectroscopy. Furthermore, X-ray magnetic circular dichroism (XMCD) measurements suggest that this 2 E g state was mixed with the 2 A 1g state by spin−orbit coupling in the ground state. Data revealed that VPc shows a paramagnetic state on the Ag surface and in an H 2 Pc film but an antiferromagnetic state in the multilayer. Partial electron charge transfer was also observed from the Ag surface to the V center at the VPc/Ag(111) interface, leading to a significant decrease in XMCD signals in the monolayer.

Two- and Three-Electron Oxidation of Single-Site Vanadium Centers at Surfaces by Ligand Design

“…The V 2p 3/2 BE for a sub-monolayer quantity of pure V (no ligand) on the reconstructed Au(100) surface (Figure 1a; 512.7 eV) matches the value reported for bulk V metal (charge-neutral) (512.7 eV 22 ) showing that final state effects in the V/Au surface environment are comparable those at the V surface, as expected. 23 24 and V(II) oxide. 15 (c) Oxidation of V by ligand 2 is evidenced by the 1.9 eV shift to higher binding energy and referenced to V(III)-N complexes.…”

“Pigments of Life”, Molecules Well Suited to Investigate Metal–Ligand Symmetry‐Restricted Covalency

“…[33j]). As such, it has to be noted that PcV XAS data have been recorded only three years ago, after Eguchi et al succeeded in the direct synthesis of PcV monolayers and multilayers on Ag(111) in ultrahigh vacuum. At variance to PcCu, whose 3d 9 Cu II central ion unambiguously implies a 2 B 1g GS, the square‐planar coordination of the 3d 3 V II ion in PcV may generate either a high‐spin (HS) or a low‐spin (LS) configuration with three ( S = 3/2) or one ( S = 1/2) unpaired electrons respectively.…”

“…X‐ray absorption spectroscopy (XAS) is solidly recognized as a tool able to probe, element‐selectively, the empty frontier molecular orbitals (MOs), the M coordinative environment, as well as the nature and the strength of the M–ligand (M–L) interaction in M complexes . In this microreview, we focus on the comparison of homogeneous theoretical results, some of them recently published by our group,[16f] pertaining to the modelling of XAS outcomes recorded at the M L 2,3 ‐edge of a series of PcM‐based complexes (M = Cu, V;[16f], see Figure , panels a, c and d) as well as of TPPCu/TPP(F)Cu, (see Figure , panel b) deposited as films on coinage metals. Even though the Cu II L 2,3 ‐edge spectra of CuPc,[16c], [16d] TPPCu and TPP(F)Cu have been modelled in the past by exploiting a relativistic time‐dependent density functional theory based on the two‐component zeroth‐order regular approximation within the Tamm–Dancoff approximation (hereafter, TD‐DFT SO‐ZORA TDA), their ab initio simulation has been reconsidered herein to ensure a comparison between totally homogeneous theoretical outcomes (Supporting Information).…”

“…In fact, besides ligand‐field and M–L covalency effects, the spin–orbit (SO) coupling between the possible many final‐state multiplets needs to be taken into account . The M L 2,3 ‐edge spectra of PcCu, PcV, PcVO,, TPPCu[30b] and TPP(F)Cu[30b] reviewed herein have been simulated by using the current Restricted Open Shell Configuration Interaction with Singles (DFT/ROCIS) method,, , which has been widely employed to model M L 2,3 ‐edge spectra of mononuclear complexes,, [33j], 2D complex systems,[16e] clusters[33i] and protoporphyrins , . Moreover, according to a well‐tested procedure,, , the outcomes of L 2,3 ‐edge XAS measurements considered herein have been rationalized by assuming that PcM‐based and TPPCu/TPP(F)Cu deposits consist of weakly interacting molecules and by completely neglecting the adsorbate/substrate interaction.…”

Effect of Solvent on the Spectroscopic, Electrochemical and Spectroelectrochemical Properties of Near-Infrared Oxovanadium(IV) α,α’-Octapentoxyphthalocyanine

“…[7] Oxovanadium(IV)-phthalocyanines, the high-valence metallo-phthalocyanines have various potential applications such as optical active materials, non-linear optical materials and catalysis, [8] but solvent dependent spectroscopic and electrochemical investigations have never been described before. In this paper, the solventdependent UV-vis, magnetic cicular dichroism (MCD) spectra, cyclic voltammetry (CV), DPV and thin-layer spectroelectrochemistry will be described.…”