Abstract:The thermal properties of organic–inorganic (CH3NH3)2CoBr4 crystals were investigated using differential scanning calorimetry and thermogravimetric analysis. The phase transition and partial decomposition temperatures were observed at 460 K and 572 K. Nuclear magnetic resonance (NMR) chemical shifts depend on the local field at the site of the resonating nucleus. In addition, temperature-dependent spin–lattice relaxation times (T1ρ) were measured using 1H and 13C magic angle spinning NMR to elucidate the param… Show more
The physical properties of the organic–inorganic hybrid crystals having the formula [NH3(CH2)3NH3]ZnX4 (X = Cl, Br) were investigated. The phase transition temperatures (TC; 268K for Cl and 272K for Br) of the two crystals bearing different halogen atoms in their skeletons were determined through differential scanning calorimetry. The thermodynamic properties of the two crystals were investigated through thermogravimetric analysis. The structural dynamics, particularly the role of the [NH3(CH2)3NH3] cation, were probed through 1H and 13C magic-angle spinning nuclear magnetic resonance spectroscopy as a function of temperature. The 1H and 13C NMR chemical shifts did not show any changes near TC. In addition, the 1H spin–lattice relaxation time (T1ρ) varied with temperature, whereas the 13C T1ρ values remained nearly constant at different temperatures. The T1ρ values of the atoms in [NH3(CH2)3NH3]ZnCl4 were higher than those in [NH3(CH2)3NH3]ZnBr4. The observed differences in the structural dynamics obtained from the chemical shifts and T1ρ values of the two compounds can be attributed to the differences in the bond lengths and halogen atoms. These findings can provide important insights or potential applications of these crystals.
The physical properties of the organic–inorganic hybrid crystals having the formula [NH3(CH2)3NH3]ZnX4 (X = Cl, Br) were investigated. The phase transition temperatures (TC; 268K for Cl and 272K for Br) of the two crystals bearing different halogen atoms in their skeletons were determined through differential scanning calorimetry. The thermodynamic properties of the two crystals were investigated through thermogravimetric analysis. The structural dynamics, particularly the role of the [NH3(CH2)3NH3] cation, were probed through 1H and 13C magic-angle spinning nuclear magnetic resonance spectroscopy as a function of temperature. The 1H and 13C NMR chemical shifts did not show any changes near TC. In addition, the 1H spin–lattice relaxation time (T1ρ) varied with temperature, whereas the 13C T1ρ values remained nearly constant at different temperatures. The T1ρ values of the atoms in [NH3(CH2)3NH3]ZnCl4 were higher than those in [NH3(CH2)3NH3]ZnBr4. The observed differences in the structural dynamics obtained from the chemical shifts and T1ρ values of the two compounds can be attributed to the differences in the bond lengths and halogen atoms. These findings can provide important insights or potential applications of these crystals.
“…The TGA result, also displayed in Figure , shows the crystal to be almost stable up to approximately 525 K. Above 525 K, the compound [NH 3 (CH 2 ) 2 NH 3 ]ZnCl 4 ( M w = 269.31 mg) experiences a molecular weight loss with increasing temperature. From the total molecular weights, the amounts of residue were obtained using eqs and , …”
In this study, we investigated the
structural dynamic features
of the [NH3(CH2)2NH3]ZnCl4 crystal as a function of temperature through magic angle
spinning (MAS) 1H nuclear magnetic resonance (NMR), MAS 13C NMR, and static 14N NMR. From the chemical shifts,
changes in the structural environments of 13C and 14N were evident. The 1H spin–lattice relaxation
time (T
1ρ) values at high temperatures
undergo molecular motion according to the Bloembergen–Purcell–Pound
theory, and the 13C T
1ρ value also varied abruptly with increasing temperature. Although
the phase-transition temperature was not detected from the differential
scanning calorimetry result, the chemical shifts and T
1ρ results showed discontinuities around 300 K.
Herein, the activation energies of molecular motion for 1H and 13C obtained from T
1ρ are discussed. In addition, we compare the structural dynamics of
diammonium-type [NH3(CH2)2NH3]ZnCl4 obtained in this study and monoammonium-type
[CH3NH3]2ZnCl4 previously
reported. The findings reported herein can provide important insights
for potential applications of [NH3(CH2)2NH3]ZnCl4 crystals.
“…Relaxation times, including longitudinal spin-lattice relaxation (T 1 ) and transverse spin-spin relaxation (T 2 ), reveal valuable information for studying molecular dynamics in practical NMR applications [1][2][3]. The combination of relaxation times and other detection parameters, such as chemical shifts and spin-spin scalar (J) couplings, endows NMR spectroscopy with its superiority over other detection methods in structural studies [4][5][6].…”
Longitudinal spin-lattice relaxation (T1) and transverse spin-spin relaxation (T2) reveal valuable information for studying molecular dynamics in NMR applications. Accurate relaxation measurements from conventional 1D proton spectra are generally subject to challenges of spectral congestion caused by J coupling splittings and spectral line broadenings due to magnetic field inhomogeneity. Here, we present an NMR relaxation method based on real-time pure shift techniques to overcome these two challenges and achieve accurate measurements of T1 and T2 relaxation times from complex samples that contain crowded NMR resonances even under inhomogeneous magnetic fields. Both theoretical analyses and detailed experiments are performed to demonstrate the effectiveness and ability of the proposed method for accurate relaxation measurements on complex samples and its practicability to non-ideal magnetic field conditions.
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