Chemically and Light-Driven Coordination-Induced Spin State Switching (CISSS) of a nonheme-iron complex

Abstract

The new Fe(II) complex [Fe(trident)(bmik)](ClO4)2 (1) (trident = bis(2-pyridylmethyl)benzylamine and bmik = bis(1-methylimidazole)ketone) exhibits a change of magnetic moment in dichloromethane (DCM) solution upon addition of pyridine which is attributed to the Coordination-Induced Spin State Switching effect (CISSS). By attaching a photoisomerizable azopyridine sidegroup to the tridentate ligand the complex [Fe(azpy-trident)(bmik)](ClO4)2 (2; azpy-trident = [N,N-bis(2-pyridylmethyl)]-3-(3-pyridylazo)benzylamine) is obtained. As detected by Evans NMR spectroscopy, 2 reversibly changes its magnetic moment in homogeneous solution upon photoirradiation which is attributed to intermolecular Light-Driven Coordination-Induced Spin State Switching (LD-CISSS). Further support for this interpretation is inferred from concentration-dependent Evans NMR measurements.

Vapochromic effect in switchable molecular-based spin crossover compounds

“…Finally, it is worth mentioning the existence of the coordination-induced spin state switch (CISSS). [86][87][88][89][90][91][92][93][94][95] This phenomenon is defined as a switch in the spin state of the metal centre, due to a change of the coordination number of the central ion. In most cases, the switch in the spin state is achieved by light irradiation (ligand-driven coordinationinduced spin state switching, LD-CISSS) 87,88,90,[94][95][96][97] or takes place in solution [86][87][88][89]91,92,[94][95][96][97][98][99][100][101] or in thin films/monolayers.…”

“…[86][87][88][89][90][91][92][93][94][95] This phenomenon is defined as a switch in the spin state of the metal centre, due to a change of the coordination number of the central ion. In most cases, the switch in the spin state is achieved by light irradiation (ligand-driven coordinationinduced spin state switching, LD-CISSS) 87,88,90,[94][95][96][97] or takes place in solution [86][87][88][89]91,92,[94][95][96][97][98][99][100][101] or in thin films/monolayers. 93 There are only a limited number of examples of solid-state CISSS vapochromism, where the inclusion of a vapour leads to a change in the spin state of the metal centre, [102][103][104] but we have decided to focus this review on purely spin crossover examples, and have excluded those resulting from coordination-induced spin state switching.…”

Light‐Switchable Metal Complexes: Introducing Photoresponsive Behaviour Through Azoheteroarenes

“…The photoisomerization of the ligand unit helps to modify the steric/electronic environment around the metal centers, in turn, influencing the catalysis. For optimizing the design principles of an effective photoswitchable organometallic catalyst, it is necessary to choose a photochrome showing [126,127,128,131] The scheme involving compounds 70 reproduced from ref. [126], copyright 2022, with permission from Walter de Gruyter and Company.…”

“…For optimizing the design principles of an effective photoswitchable organometallic catalyst, it is necessary to choose a photochrome showing [126,127,128,131] The scheme involving compounds 70 reproduced from ref. [126], copyright 2022, with permission from Walter de Gruyter and Company. The scheme involving compounds 71 adapted from ref.…”

Ni-Centered Coordination-Induced Spin-State Switching Triggered by Electrical Stimulation

“…, from a high-spin (HS) to a low-spin (LS) state, are triggered by rational/drastic modifications of the first coordination sphere of a given metal center upon stimulation. The few examples reported to date in the literature involve a quite limited number of transition metals, namely, Fe­(II), − Mn­(V), or Ni­(II), ,,− selected for their ability to undergo HS ↔ LS transitions following the addition or removal of ligand(s) from the metal center (Figure a). , All of these achievements involve the use of chemicals (pH) ,, or light ,− ,,, as triggers for molecular motions, leading to an increase or decrease in the coordination number of the metal. In contrast, far less progress has been made in these directions with electron-responsive systems, even though electricity stands as a particularly attractive, controllable, and clean trigger in the perspective of applications in solid-state devices. − The few examples of redox-triggered magnetic switching reported so far in literature are based on Prussian blue analogues or transition-metal complexes exhibiting valence tautomerism. − …”