Physical Chemistry Chemical Physics 2018-04-12

Electron paramagnetic resonance of copper doped [(CH3)2NH2][Zn(HCOO)3] hybrid perovskite framework

Mantas Simenas, Aneta Ciupa, Gediminas Usevicius, Kęstutis Aidas, Daniel Klose, Gunnar Jeschke, miroslaw maczka, Georg Völkel, Andreas Poppl, Juras Banys

Index: 10.1039/C8CP01426D

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Abstract

We report a continuous-wave (CW) and pulse electron paramagnetic resonance (EPR) as well as pulse electron nuclear double resonance (ENDOR) study of Cu2+ doped [(CH3)2NH2][Zn(HCOO)3] hybrid perovskite which exhibits a structural phase transition. The multifrequency (X, Q and W-band) CW EPR measurements allow to study the temperature evolution of the Cu2+ ion local environment. The spectrum of the ordered (low-temperature) phase reveals an axially distorted octahedral Cu2+ site confirming successful replacement of the Zn2+ ions and formation of the CuO6 octahedra. The CW EPR spectrum of the disordered (high-temperature) phase shows an additional broad line which gradually diminishes on cooling. The EPR linewidth of the axially symmetric Cu2+ ion site exhibits an anomaly at the phase transition point and Arrhenius-type behavior in the disordered phase. The temperature dependent Cu2+ spin Hamiltonian parameters change abruptly at the phase transition point indicating a strong first-order character of the transition. The X-band pulse ENDOR spectrum of the ordered phase reveals several protons in the vicinity of the Cu2+ center.