Photoinduced Mo−CN Bond Breakage in Octacyanomolybdate Leading to Spin Triplet Trapping

Abstract

The photoinduced properties of the octacoordinated complex K4MoIV(CN)8⋅2 H2O were studied by theoretical calculations, crystallography, and optical and magnetic measurements. The crystal structure recorded at 10 K after blue light irradiation reveals an heptacoordinated Mo(CN)7 species originating from the light‐induced cleavage of one Mo−CN bond, concomitant with the photoinduced formation of a paramagnetic signal. When this complex is heated to 70 K, it returns to its original diamagnetic ground state, demonstrating full reversibility. The photomagnetic properties show a partial conversion into a triplet state possessing significant magnetic anisotropy, which is in agreement with theoretical studies. Inspired by these results, we isolated the new compound [K(crypt‐222)]3[MoIV(CN)7]⋅3 CH3CN using a photochemical pathway, confirming that photodissociation leads to a stable heptacyanomolybdate(IV) species in solution.

Isolation and Structural Characterization of Eightfold Protonated Octacyanometalates [M(CNH)8]4+ (M=MoIV, WIV) from Superacids

“…Since the early 2000s, a plethora of octacyanometalate‐based supramolecular coordination networks as well as polynuclear complexes and cluster compounds have been reported. The ease of oxidation of [M(CN) 8 ] 4− (M=Mo, W) to [M(CN) 8 ] 3− and the accessibility of an excited triplet state for [M(CN) 8 ] 4− (M=Mo, W) by light irradiation make octacyanometalates suitable building blocks for photomagnetic materials, while paramagnetic [M(CN) 8 ] 3− (M=Mo, W) are promising building blocks for single‐molecule magnets …”

“…Since the early 2000s, a plethora of octacyanometalate-based supramolecular coordination networks as well as polynuclear complexes and cluster compounds [20][21][22][23][24] have been reported. [25][26][27][28] while paramagnetic [M(CN) 8 ] 3À (M = Mo, W) are promising building blocks for single-molecule magnets. [29] While treatment of octacyanometalates with hydrogen chloride gives adducts of the neutral acids H 4 [30] [31] and H 4 [Mo- [32] •2 HF both crystallize in the monoclinic space group P2 1 /n and are isomorphous.…”

Isolierung und strukturelle Charakterisierung der achtfach protonierten Octacyanometallate [M(CNH)8]4+ (M=MoIV,WIV) aus Supersäuren

“…Seit den frühen 2000er Jahren wurde über eine Vielzahl Octacyanometallat‐basierter supramolekularer Netzwerke sowie mehrkerniger Komplexe und Cluster‐Verbindungen berichtet . Die leichte Oxidierbarkeit von [M(CN) 8 ] 4− (M=Mo,W) zu [M(CN) 8 ] 3− und die Verfügbarkeit eines angeregten Triplett‐Zustands von [M(CN) 8 ] 4− (M=Mo,W) durch Bestrahlung machen Octacyanometallate der Oxidationsstufe +IV zu geeigneten Bausteinen für photomagnetische Materialien, während die paramagnetischen Komplexe der Oxidationsstufe +V, also [M(CN) 8 ] 3− (M=Mo,W), vielversprechende Bestandteile für molekulare Magnete sind …”

“…Bestrahlung machen Octacyanometallate der Oxidationsstufe + IV zu geeigneten Bausteinen für photomagnetische Materialien, [25][26][27][28] während die paramagnetischen Komplexe der Oxidationsstufe + V, also [M(CN) 8 ] 3À (M = Mo,W), vielversprechende Bestandteile für molekulare Magnete sind. [29] Während die Umsetzung von Octacyanometallaten mit Chlorwasserstoff zu Addukten von den neutralen Säuren [30] [31] und [32] 2) und in einer ähnlichen Grçßenordnung wie bei protonierten Nitrilen mit Hexafluorometallat-Gegenionen (2.5-2.8 ).…”

Tuning the Optical Properties of Magnetic Materials

“…A very recent report on the K 4 [Mo IV (CN) 8 ] complex provides evidence that the origin of its photomagnetic effect is reversible photodissociation of the Mo-CN bond. [29] In this chapter, we highlight examples of photoinduced magnetisation phenomena in Co-W bimetallic assemblies.…”