Electron paramagnetic resonance characterization and electron spin relaxation of manganate ion in glassy alkaline LiCl solution and doped into Cs2SO4

• Published in: Journal of inorganic biochemistry Vol. 229; p. 111732
• Main Authors: Mahapatro, Surendra N., Hovey, Tanden A., Ngendahimana, Thacien, Eaton, Sandra S., Eaton, Gareth R.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.04.2022
• Subjects: Electron spin relaxation; Glassy alkaline LiCl; Manganate ion; Electron spin relaxation; Glassy alkaline LiCl; Manganate ion
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2022.111732

Manganate ion, MnO42−, has important roles in catalysis and potential roles in water treatment. EPR spectra of MnO42− in a glassy alkaline solution of concentrated LiCl at X-band and Q-band at 80 K exhibit g1 = 1.9776 ± 0.001, g2 = 1.9677 ± 0.001, g3 = 1.9560 ± 0.001 and A1 = 182 ± 9, A2 = 275 ± 15, and A3 = 400 ± 15 MHz. In Cs2SO4 the spectra were simulated with 1.908 ± 0.001, g2 = 1.909 ± 0.001, g3 = 1.937 ± 0.001 and A1 = 90 ± 20, A2 = 100 ± 20, and A3 = 400 ± 15 MHz. Simulations required large distributions in A values which suggests that hyperfine splittings are sensitive to differences in geometry. Continuous wave spectra are observable at 80 K in glassy alkaline LiCl, but only up to about 20 K in Cs2SO4. In glassy alkaline LiCl electron spin relaxation was measured at X-band using spin echo and inversion recovery from 4.2 to 60 K. Tm is 4.6 μs at 4.2 K and decreases at higher temperatures as it becomes driven by T1. T1 decreases from ca. 34 ms at 4.2 K to ca. 240 ns at 60 K. Tm and T1 in Cs2SO4 are too short to measure by electron spin echo. The distorted tetrahedral geometry of MnO42− results in faster relaxation than for other 3d1 spin systems that have square pyramidal (C4v) or distorted octahedral geometries. [Display omitted] •Electron paramagnetic resonance g values of MnO42− are characteristic of S = ½.•Electron spin relaxation for MnO42− is faster than for other d1 ions.•Relaxation of MnO42− is faster in crystalline Cs2SO4 than in glassy alkaline LiCl.•Electron spin relaxation of distorted tetrahedral ions is faster than other geometries.