K⊂{[FeII(Tp)(CN)3]4[CoIII(pzTp)]3[CoII(pzTp)]}: a neutral soluble model complex of photomagnetic Prussian blue analogues

Abstract

Straightforward access to a new cyanide-bridged {Fe₄Co₄} “molecular box” containing a potassium ion, namely K⊂{[Fe^II(Tp)(CN)₃]₄[Co^III(^pzTp)]₃[Co^II(^pzTp)]} (1) (with Tp and ^pzTp = tris- and tetrakis(pyrazolyl)borate, respectively), is provided, alongside its full characterisation. A detailed analysis of the molecular structure (X-ray diffraction, mass spectrometry, NMR spectroscopy) and electronic properties (EPR spectroscopy, SQUID magnetometry, UV/Vis spectroscopy, cyclic voltammetry) reveals that 1 shows slow magnetic relaxation and a remarkable photomagnetic effect at low temperature which is reminiscent of some FeCo Prussian Blue Analogues (PBAs), and is ascribed to a photo-induced electron transfer. However, in contrast with these inorganic polymers, the overall neutral compound 1 is soluble and remarkably stable in organic solvents such as CH₂Cl₂. Moreover, 1 shows interesting redox versatility, with electrochemical experiments revealing the possible access to six stable redox states.