Quenching and Restoration of Orbital Angular Momentum through a Dynamic Bond in a Cobalt(II) Complex

Abstract

Orbital angular momentum plays a vital role in various applications, especially magnetic and spintronic properties. Therefore, controlling orbital angular momentum is of paramount importance to both fundamental science and new technological applications. Many attempts have been made to modulate the ligand-field induced quenching effects of orbital angular momentum to manipulate magnetic properties. However, to date, reported changes in the magnitude of orbital angular momentum are small in both molecular and solid-state magnetic materials. Moreover, no effective methods currently exist to modulate orbital angular momentum. Here, we report a dynamic bond approach to realize a large change in orbital angular momentum. We have developed a Co(II) complex that exhibits coordination number switching between six and seven. This cooperative dynamic bond switching induces considerable modulation of the ligand field, thereby leading to substantial quenching and restoration of the orbital angular momentum. This switching mechanism is entirely different from those of spin-crossover and valence tautomeric compounds, which exhibit switching in spin multiplicity.

Ab Initio Methods in First‐Row Transition Metal Chemistry

“…While quantitative results with CASPT2 and NEVPT2 can be achieved when appropriate active spaces and basis sets are chosen, it is noteworthy to mention that even with small basis sets and minimal active spaces, CASPT2 or NEVPT2 in some cases can give results being close to experimental data. [160,161] However, the results likely benefit from fortuitous error cancellation and should be interpreted with care.…”

Role of Coordination Number and Geometry in Controlling the Magnetic Anisotropy in FeII, CoII, and NiII Single‐Ion Magnets

“…Out of these three complexes, only complex 2 shows U eff =23 cm −1 under an applied dc field. Very recently, a Co II complex [Co(NO 3 ) 2 (L)] (where L=ethyl‐2.6‐di(1 H ‐pyrazol‐1‐yl)isonicotinate) ( 4 ) has been reported by Sato and co‐workers, which shows a temperature‐dependent dynamic switching from seven‐ to six‐coordinate geometry [22] . The seven‐coordinate structure is stabilised at low temperature (1–50 K) and six coordination at high temperature (>135 K).…”

Desolvation–Solvation-Induced Reversible On–Off Switching of Two Memory Channels in a Cobalt(II) Coordination Polymer: Overlay of Spin Crossover and Structural Phase Transition

“…[11,12] In addition to the significant changes in magnetism, modulation on spin states may also synergize with other functionalities, such as electrical conductivity, [13,14] ferroelectric property, [15,16] negative thermal expansion, [17,18] or luminescence, [19,20] portending such kind of molecules toward multi-functional materials. Moreover, magnetic changes may be also achieved in a non-spin switching manner, induced by the so-called structural phase transition (SPT), such as order/disorder rearrangement, [21,22] dynamic coordination bond breakage/formation, [23] ligand rotation, [24] or cis-trans isomerism. [25] Thereafter, the incorporation of both spin and non-spin transitions (SCO + SPT) in one molecule has provided a new promising strategy for the construction of multifunctional systems, which are useful for multi-switching and ternary memory devices.…”