Here we report the completely reversible spin state switch of the naturally diamagnetic tris(bipyridine)iron(ii) complex and the spin crossover complex bis(2,6-bis(1H-pyrazol-3-yl)pyridine)iron(ii) by the variation of the pH followed by H-NMR, UV-Vis spectroscopy, and magnetic and relaxivity measurements in solution and as composite materials encapsulated in a zeolite matrix.

A nano confinement strategy is presented to control the spatial orientation and emission polarization of phosphorescent metal complexes. Through nano-confinement of the phosphorescent metal complex [Ru(bpy)3 ](2+) by attaching it to anionic clay nanoplatelets, it is possible to simultaneously lock the spatial orientation of the complex and fix its emission polarization. This quasi-epitaxial approach may provide a future work strategy directed at light emitting diodes and lasers.

Because of strong Coulomb interactions, the delamination of charged layered materials becomes progressively more difficult with increasing charge density. For instance, highly charged sodium fluorohectorite (NaMgLiSiOF, Na-Hec) cannot be delaminated directly by osmotic swelling in water because its layer charge exceeds the established limit for osmotic swelling of 0.55 per formula unit SiOF. Quite surprisingly, we found that this hectorite at the border of the smectite and vermiculite group can, however, be utterly delaminated into 1-nm-thick platelets with a high aspect ratio (24 000) in a two-step process. The hectorite is first converted by partial ion exchange into a one-dimensionally ordered, interstratified heterostructure with strictly alternating Na and n-butylammonium (C4) interlayers. This heterostructure then spontaneously delaminates into uniform single layers upon immersion in water whereas neither of the homoionic phases (Na-Hec and C4-Hec) swells osmotically. The delamination of more highly charged synthetic layered silicates is a key step to push the aspect ratio beyond the current limits.

Increasing dynamics in solids featuring nuclei subjected to second-order quadrupolar interactions lead to central-transition spectra that undergo two consecutive line-shaped transitions. Conventional motional narrowing occurs when the molecular exchange rate is on the order of the strength of the dominant interaction. In a second step, the resulting intermediately narrowed spectra change further when the motion becomes faster than the Larmor precession rate, leading to terminally narrowed spectra that can display a residual quadrupolar shift. We derive analytic expressions for this shift and analyze the quadrupolar central-transition spectra in terms of CN symmetrical cone models. Increasing the number of sites to N ≥ 3, the terminally narrowed spectra remain unaltered, while the intermediately narrowed spectra remain unaltered only for N ≥ 5. This finding relates to the different (cubic vs. icosahedral) symmetries that are required to average out the spatial second- and fourth-rank terms in the second-order quadrupolar interaction. Following recent work (Hung et al., Solid State Nucl Magn Reson 84:14–19, 2017), 17O NMR is applied to examine the three-site rotation of the nitrate group in NaNO3. Line shapes are measured and analyzed, and in addition to prior work, satellite-transition and stimulated-echo experiments are carried out. The final-state amplitudes extracted from the latter are reproduced using model calculations. It is shown how two-dimensional exchange spectra relating to N-site cone motions can be decomposed in terms of effective two-site-jump spectra. This latter approach is successfully tested for NaNO3.

Oxygen-17 spin relaxation and stimulated-echo experiments are carried out to study temperature-dependent reorientational time scales in potassium permanganate. From an analysis of the present data, an energy barrier of 0.35 eV is found. This activation energy is much larger than the one reported previously (Jakobsen et al. Quantitative Dynamics and Structure for Crystalline Cs2WO4 and KMnO4 Determined from High-Field 17O Variable-Temperature MAS NMR Experiments, J. Phys. Chem. C 2014, 118, 20639–20646), but it is on the order of magnitude expected from observations for the dynamics of other tetraoxoanions in ionic crystals. The various contributions to the measured spin relaxation times and details regarding the two-time correlation functions for KMnO4 are discussed.