Reversible quantitative guest sensing via spin crossover of an iron(ii) triazole

Abstract

Discrete mononuclear [FeII(tolpzph)2(NCS)2]·THF (1·THF), shows highly sensitive, robust and reversible solvent-dependent spin crossover, enabling it to act as a quantitative small molecule sensor.

Predictable Electronic Tuning By Choice of Azine Substituent in Five Iron(II) Triazoles: Redox Properties and DFT Calculations

“…As described previously, the five L azine ligands (Figure ; azine =pyridazine, pyrazine, pyridine, 2‐pyrimidine and 4‐pyrimidine) used in this study were synthesized by the straightforward extension of the general method described in 2004 by Klingele and Brooker . The five mononuclear iron(II) tris ‐ligand complexes, [Fe II ( L azine ) 3 ](BF 4 ) 2 , and four solvatomorphs, were obtained from 3:1 reactions, in air, of the chosen L azine ligand with [Fe II (H 2 O) 6 ](BF 4 ) 2 in either CH 2 Cl 2 /CH 3 OH (10:1) or CH 3 CN solution.…”

“… The symmetrical Rdpt 1,2,4‐triazole ligand (box), and the family of non‐symmetrically azine ‐substituted Rat 1,2,4‐triazole ligands ( L azine ) with five different azine rings ( azine =pyridazine, pyrazine, pyridine, 2‐pyrimidine and 4‐pyrimidine) used in this study and which have previously produced SCO‐active iron(II) complexes.…”

“…We have recently employed five monotopic azine ‐substituted 1,2,4‐ triazole ligands, L azine (Figure , Rat ligands) to generate a large family of mononuclear iron(II) complexes, [Fe II ( L azine ) 2 (NCE) 2 ] (E=S, Se and BH 3 ), that are SCO‐active in both the solid‐ and solution‐phase . The solution studies on these complexes have enabled us to (i) investigate the effects of solvent polarity on the spin state; (ii) place five azines in order of increasing ligand field strength in [Fe II ( L azine ) 2 (NCBH 3 ) 2 ] complexes (4‐pyrimidine <2‐pyrimidine < pyridine < pyrazine < pyridazine), and (iii) develop a simple and general method that enables us to predict, before synthesis, the spin state of metal complexes in solution, once a trend line is established for the family of interest [T 1/2 from Evans method on the complex vs. 15 N chemical shift for the ligand, either measured or calculated by density functional theory (DFT)] .…”

Solvent-dependent SCO Behavior of Dinuclear Iron(II) Complexes with a 1,3,4-Thiadiazole Bridging Ligand

“…35−39 The effect can, in very few cases, even be reversibly triggered by desolvation and resolvation of the solvent molecules. [36][37][38]40 In this paper, we present two dinuclear iron(II) SCO complexes [Fe 2 (μ-L) 2 ]X 4 *4DMF (X = BF 4 − (1·4DMF) and ClO 4 − (2·4DMF)) with magnetic properties highly depending on the solvent content in the solid state. The main structure of these complexes is analogous to previously reported complexes 1·2H 2 O and 2·0.5H 2 O from our group, 41 with the bis-(tridentate) 1,3,4-thiadiazole bridging ligand L (2,5-bis[(2-pyridylmethyl)amino]methyl-1,3,4-thiadiazole).…”

Spin-Crossover Materials towards Microwave Radiation Switches

“…As photonic materials they attract attention for the development of optical switches24, protective elements25, microthermometers26 etc. A unique sensitivity of their transition properties towards chemical influences make them attractive candidates for the active elements of chemical sensors with optical, spectroscopic, magnetic or other techniques of detection272829.…”