Pulse EPR and ENDOR Study of Manganese Doped [(CH3)2NH2][Zn(HCOO)3] Hybrid Perovskite Framework

Abstract

We present a pulse electron paramagnetic resonance (EPR) and electron–nuclear double resonance (ENDOR) study of a manganese-doped [(CH3)2NH2][Zn(HCOO)3] dense metal–organic framework which exhibits a structural phase transition at 163 K. The echo-detected field sweep Mn2+ EPR spectrum of the low-temperature phase is in a perfect agreement with the previous continuous-wave EPR results, while the spectrum of the disordered phase reveals a significant EPR transition-dependent relaxation. The 1H ENDOR pattern indicates several protons in the vicinity of the Mn2+ ion. The experimental ENDOR spectrum is successfully simulated using the proton hyperfine tensors calculated by the density functional theory. A multifrequency electron spin echo envelope modulation (ESEEM) spectroscopy shows a peculiar signal which is unaffected by the external magnetic field. The modulation depth of this signal starts to decrease above 40 K, coinciding with the temperature at which the methyl groups of the (CH3)2NH2+ cations start t...