1338601-62-9Relevant academic research and scientific papers
Synthesis and electronic structure determination of N-alkyl-substituted bis(imino)pyridine iron imides exhibiting spin crossover behavior
Bowman, Amanda C.,Milsmann, Carsten,Bill, Eckhard,Turner, Zoe R.,Lobkovsky, Emil,Debeer, Serena,Wieghardt, Karl,Chirik, Paul J.
, p. 17353 - 17369 (2011)
Three new N-alkyl substituted bis(imino)pyridine iron imide complexes, (iPrPDI)FeNR (iPrPDI = 2,6-(2,6-iPr 2-C6H3-N=CMe)2C5H 3N; R = 1-adamantyl (1Ad), cyclooctyl (CyOct), and 2-adamantyl (2Ad)) were synthesized by addition of the appropriate alkyl azide to the iron bis(dinitrogen) complex, ( iPrPDI)Fe(N2)2. SQUID magnetic measurements on the isomeric iron imides, (iPrPDI)FeN1Ad and ( iPrPDI)FeN2Ad, established spin crossover behavior with the latter example having a more complete spin transition in the experimentally accessible temperature range. X-ray diffraction on all three alkyl-substituted bis(imino)pyridine iron imides established essentially planar compounds with relatively short Fe-Nimide bond lengths and two-electron reduction of the redox-active bis(imino)pyridine chelate. Zero- and applied-field Moessbauer spectroscopic measurements indicate diamagnetic ground states at cryogenic temperatures and established low isomer shifts consistent with highly covalent molecules. For (iPrPDI)FeN2Ad, Moessbauer spectroscopy also supports spin crossover behavior and allowed extraction of thermodynamic parameters for the S = 0 to S = 1 transition. X-ray absorption spectroscopy and computational studies were also performed to explore the electronic structure of the bis(imino)pyridine alkyl-substituted imides. An electronic structure description with a low spin ferric center (S = 1/2) antiferromagnetically coupled to an imidyl radical (Simide = 1/2) and a closed-shell, dianionic bis(imino)pyridine chelate (SPDI = 0) is favored for the S = 0 state. An iron-centered spin transition to an intermediate spin ferric ion (SFe = 3/2) accounts for the S = 1 state observed at higher temperatures. Other possibilities based on the computational and experimental data are also evaluated and compared to the electronic structure of the bis(imino)pyridine iron N-aryl imide counterparts.
