Solid-State NMR Characterization of the Reorientational Dynamics of A-site Cations in 2D OIHPs
Chien-Chieh Lin a b, Shing-Jong Huang Shing-Jong Huang c, Chun-Wei Chen a d f, Tsyr-Yan Dharma Yu a e
a International Graduate Program of Molecular Science and Technology (NTU-MST), National Taiwan University, Taipei 10617, Taiwan
b Molecular Science and Technology Program, Taiwan International Graduate Program (TIGP), Academia Sinica, Taipei 11529, Taiwan
c Instrumentation Center, National Taiwan University, Taipei 10617, Taiwan
d Department of Materials Science and Engineering, National Taiwan University, Taipei 10617, Taiwan
e Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
f Center of Atomic Initiative for New Materials (AI-MAT), National Taiwan University, Taipei 10617, Taiwan
Proceedings of Online Conference on Atomic-level Characterisation of Hybrid Perovskites (HPATOM2)
Online, Spain, 2022 February 2nd - 3rd
Organizers: Michael Hope and Eve Mozur
Invited Speaker, Tsyr-Yan Dharma Yu, presentation 003
DOI: https://doi.org/10.29363/nanoge.hpatom.2022.003
Publication date: 30th October 2021

The reorientational dynamics of A-site cations in two-dimensional organic-inorganic hybrid perovskites (2D OIHPs) play an important role in determining the physical and optoelectronic properties of the materials. However, only scant studies are aviable for studying the reorientational dynamics of A-site cations incorporated in D OIHPs. In this work, we adope isotope-labeling strategy for preparing two different 2D OIHPs samples, consisting of uniformly ¹⁵N- and ¹³C-enriched methylammonium ([U-13C,U-15N]MA) or methyl-d3-ammonium (CD3NH3+),  respectively. One the one hand,  rotational-echo double resonance (REDOR) NMR was used to measure the effective dipolar coupling between the 13C and 15N nuclei of MA, which is modulated by the molecular reorientational motion of MA. On the other hand, the molecular  reorientational motion of CD3NH3+, providing motional modulation to the deuterium quadrupole coupling of  CD3NH3+, can also be studied using the 2H NMR spectral lineshape analysis of CD3NH3incorporated in 2D OIHPs. Our 2H NMR study revealed the existence of the multiple modes of the reorientational motions of CD3NH3+ and the REDOR NMR reflected the averaged dipolar coupling between the 13C and 15N nuclei of MA undergoing different modes of motions. We would like to share that our study revealed some interesting interplay between the A-site cation dynamics and the structural rigidity of the organic spacers.

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