Methanol‐Triggered Vapochromism Coupled with Solid‐State Spin Switching in a Nickel(II)‐Quinonoid Complex

Abstract

A highly methanol‐selective vapochromic response has been realized in a NiII‐quinonoid complex, [Ni(HLMe)2] (H2LMe=4‐methylamino‐6‐methyliminio‐3‐oxocyclohexa‐1,4‐dien‐1‐olate) which exhibits a reversible structural transformation including a coordination geometrical change between the square‐planar and octahedral structure by the selective uptake of methanol vapor. This was accompanied by a remarkable color change between purple and orange, as well as temperature‐robust spin‐state switching in the solid state under ambient conditions. It is remarkable that the properties are derived by the fine structural modification of the quinonoid ligand such as methyl or ethyl analogues. Such a system has high potential for applications in memory devices as well as chemical sensors and smart responsive materials.

Interfacial Spin Manipulation of Nickel-Quinonoid Complex Adsorbed on Co(001) Substrate

“…The magnetic moment of the Ni atom, Ni-O(N) bond length in gas phase, and in different chemisorbed configurations are shown in Table 1. Our calculations predict a zero moment (S = 0) for the gas-phase NiQ molecule, consistent with experiments [38]. We note, with regard to the obtained S = 0 state, that we verified that the zero-moment property is robust against variations of the Coulomb U value between 2 and 8 eV.…”

“…Thus, an on-surface spin-state switching to a high-spin state can be induced by adsorption of NiQ on the Co substrate. Compared to the reported magnetochemical reaction [38] in which two MeOH groups bond to Ni in the axial ligand positions, in the on-surface reaction, the molecule bonds one-sided to the top-layer surface atoms. The spin moment on the molecule is less than what would be expected for the high-spin S = 1 state.…”

“…We modeled the square-planar NiQ molecule structure according to the reported data [38]. To start with, we optimized the geometry of the isolated NiQ molecule in the gas phase.…”

“…Recently, Kar et al designed a methanol-triggered vapochromism and spin-switching in a Ni(II)-quinonoid (NiQ) complex [Ni(HL) 2 , H 2 L = 4-methylamino-6-methyliminio-3-oxocyclohexa-1, 4-dien-1-olate], which is a planar molecule. They showed that the addition of methanol (MeOH) to the molecule leads to a magnetochemical reaction, in which the central Ni atom of the molecule changes it co-ordination from square-planar to octahedral by axial ligation of two MeOH groups at the Ni site, accompanied by a temperature-robust spin transition from S = 0 to S = 1 [38]. This observation suggests that the Ni(II)-quinonoid could be a potential candidate material for application in spintronics devices.…”

Hetero-Bimetallic Effect as a Route to Access Multinuclear Complexes

“…As far-redin the optoelectronic field (OPV, DSSC, photodetection, conducand selective gas sensors thanks to the presence of two spin state changes in the case of nickel for instance). 18 (R = nBu) (m = 144 mg, 0.399 mmol, 1 equiv.) in THF (v = 4 mL) was added at room temperature overnight and the solvent was and the obtained precipitate was isolated as a dark green crystalline powder (m = 193 as obtained by slow diffusion with CDCl 3 / n-heptane.…”