An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Mixed-metal (PtII, PdII) μ-NH2-complexes are readily formed upon reaction of trans-[(NH3)2PtL2] (L = 2-aminopyridine-N1 or pyrazolate-N1; charges omitted) with [enPd(H2O)2]2+.
Dynamic 2H NMR spectroscopy employing line shape studies and spin−lattice relaxation experiments is used to investigate the molecular dynamics of the perdeuterated pyridinium cations in pyridinium tetrafluoroborate in the temperature range between 120 and 290 K. Special interest lies in the two solid−solid phase transitions occurring at 204 K and at 238.7 K. The experimental spectra show that the pyridinium cations perform fast rotation around the pseudo C6 axis at high temperatures. Decreasing the temperature leads to successive slowing down of the rotational motion resulting in nearly completely immobile and preferentially oriented pyridinium cations at 120 K. Simulating the spectra with a 3-site or a 6-site jump model shows that both are appropriate to describe the experimental NMR data. The models yield population probabilities which permit the calculation of the orientational contribution to the polarization and the enthalpy change. For both models distinct deviations from the macroscopic properties are found. We therefore suggest that, in addition to the cation orientation, the classical ferroelectric mechanism operates which has a partly compensating effect. A displacement of anion vs cation sublattice by 0.23−0.25 Å is sufficient to account for the missing polarization contribution. Both these ferroelectric mechanisms are potentially continuous in their onset, which is compatible with second-order transitions, but it appears that they may both be borderline cases between second and first order.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The interaction of muoniated cyclohexadienyl radicals with zeolite environments in NaY, HY, and USY has been studied using mainly avoided level crossing muon spin rotation (ALC-μSR) spectroscopy, which utilizes spin-polarized positive muons as local probes. A strong interaction of C6H6Mu with sodium cations in NaY is indicated and leads to significant distortion of the C6H6Mu structure from planarity, accompanied by large shifts in hyperfine coupling constant (hfcc) values compared to those in bulk benzene. Much weaker interactions of this radical with Brønsted acid sites in USY/HY are deduced from the measured muon and proton hfcc values, indicative of a largely planar radical, that, in contrast to those in NaY, also exhibit a strong dependence on benzene loading. The small shifts in hfcc values seen in USY/HY compared to those in the bulk relate to the nature of OH binding sites and possibly also to effects arising from varying local dielectric constants at different benzene packing densities. The muon ALC resonances in these frameworks exhibit a marked increase in widths at temperatures near 300 K and at low benzene loadings, evidence for molecular dynamics, indicating desorption and reorientation of C6H6Mu, in marked contrast to the nearly static widths seen in NaY up to 470 K.
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