The dataset is organised into two components:

(1) NMR_Source_Data (folder) This folder contains the complete set of solid-state NMR experiments in .csdf format. It includes: High-temperature MAS (10 kHz) NMR data collected during heating of crystalline and glassy (S-NEA)2PbBr4 samples: 1H (200.1 MHz), 13C (50.3 MHz), 207Pb (41.9 MHz) Ambient-temperature high-field MAS (60 kHz) NMR data for both crystalline and glassy (S-NEA)2PbBr4 samples: 1H (750.0 MHz) and 13C (188.6 MHz)

(2) Source Data.xlsx (spreadsheet) This file contains the numerical values underlying all plots in the main article, organised by figure. Included datasets: Figure 1b Differential scanning calorimetry data (argon atmosphere, 10 °C min-1) for (S-NEA)2PbBr4: first heating (upscan 1); first cooling (downscan); second heating (upscan 2) Figure 1c Powder X-ray diffraction data for crystalline and glassy (S-NEA)2PbBr4 samples. Figure 2a Total scattering structure factors S(Q) for crystalline and glassy (S-NEA)2PbBr4 samples Figure 2b Corresponding pair distribution functions D(r) Figure 3a Temperature-dependent Pb coordination numbers, Pb–Br bond lengths, and raw variable-temperature PDF data collected in situ during heating Figure 3b THz/Far-IR vibrational spectra and extracted Pb–Br stretching-mode frequencies during heating to 200 °C and cooling Figure 3d Temperature dependence of the 207Pb chemical shift during heating of crystalline (S-NEA)2PbBr4 samples Figure 3e Temperature dependence of the 207Pb chemical shift during heating of glassy (S-NEA)2PbBr4 samples.