Substituent-Influenced Spin Crossover in Fe-III Quinolylsalicylaldiminates

作者：Sertphon Darunee; Harding David J^*; Harding Phimphaka; Murray Keith S; Moubaraki Boujemaa; Adams Harry; Alkas Adil; Telfer Shane G

来源：European Journal of Inorganic Chemistry, 2016, 2016(3): 432-438.

DOI：10.1002/ejic.201501188

• Spin crossover
• Iron
• N, O ligands
• Magnetic properties
• Substituent effects

The new ligand Hqsal-4-OMe was synthesized, and four iron(III) complexes, [Fe(qsal-4-OMe)(2)] Y center dot CH2Cl2 [Hqsal-4-OMe = 4-methoxy-N-(8-quinolyl) salicylaldimine; Y = ClO4 (1), NO3 (2)] and [Fe(qsal-4-OMe)(2)] Y (Y = PF6 (3), OTf (4)] as well as the isomer [Fe(qsal-5-OMe)(2)] PF6 center dot CH2Cl2 (5), were prepared. UV/Vis spectroscopic studies indicated that the complexes are highspin in solution and exhibit a ligand-to-metal charge-transfer band around 400 nm. X-ray crystallographic studies on [Fe(qsal-4-OMe)(2)] Y center dot CH2Cl2 (Y = ClO4, NO3) and [Fe(qsal-4-OMe)(2)] PF6 at 97 K revealed high-spin FeIII centres with one of the qsal-4-OMe ligands significantly distorted from planarity. In contrast, in 5 the FeIII centre is low-spin at low temperature, and the roomtemperature structure of 5 shows about 25 % spin crossover (SCO). The structure of [Fe(qsal-4-OMe)(2)] Y center dot sol shows weak pp interactions between neighbouring cations, while 5 exhibits stronger p-p interactions that link it into a 1D chain. SQUID magnetometric studies revealed that 1-4 are essentially highspin, whereas 5 undergoes gradual and almost complete SCO up to 350 K. A combination of distortions to the qsal-4-OMe ligand and intermolecular C-H center dot center dot center dot O interactions involving both the coordinated phenolate oxygen atom and the OMe group seem to be responsible for the loss of SCO.

• 出版日期2016-1