Nature of the incommensurate-paraelectric transition: A two-dimensional exchange-difference NMR study

Dynamics of the quasiordered structure in the regioregulatedπ-conjugated polymer poly(4-methylthiazole-2,5-diyl)

“…For investigation of dynamic processes such as chemical exchange, cross relaxation, spin diffusion, and atomic hopping motion, the two-dimensional exchange spectroscopy has a number of advantages over the one-dimensional techniques. The 2DEX NMR method particularly provides the valuable data when trying to observe slow dynamics in solids 20,23,64,65,66 . A spatial motion of certain atom (or molecule) such as diffusion or reorientation is detected in the form of frequency change during the mixing time, t mix .…”

“…Dynamics of modulation waves in IC solids is also investigated by various NMR experiments. In Rb 2 ZnCl 4 (and its analogue) 7,15,16,17,18,19,20 , bis(4-chlorophenyl) sulfone 13 , and barium sodium niobate 21,22,23 , it is known that the structural modulation wave with respect to atomic displacements from equiblium positions produces a discommensuration in the higher temperature regime of incommensurate-commensurate transition temperature. As far as π-conjugated polymers are concerned, there are, however, quite limited publications concerning quasi-ordered phases.…”

The Dynamic Structure of Regioregulated Poly(4-methylthiazole-2,5-diyl)

“…The 2DEX NMR method provides particularly valuable information on slow dynamics in solids. [30][31][32][33][34] Dynamics, such as diffusion and/or reorientation, of certain atom (or molecule) is detected in the form of frequency change during the mixing time, t mix . Moving nuclei experience a change of resonace frequency between at the beginning and at the end of t mix and then create cross peaks, while static nuclei without changing the frequency (or moving nuclei with a frequency of much higher than 1=t mix ) produce the diagonal signals in the two-dimensional spectrum.…”

Solid-State93Nb and13C NMR Investigations of Half-Sandwich Niobium(I) and Niobium(V) Cyclopentadienyl Complexes

“…However, its moderately sized nuclear quadrupole moment ( Q ( 93 Nb) = −0.32 × 10 -28 m 2 ) often results in severe quadrupolar broadening of central-transition NMR powder patterns, which in some cases is prohibitive in terms of routine spectral acquisition and interpretation. Nonetheless, solid-state 93 Nb NMR has been used to study a variety of different systems, including inorganic niobium halides, intercalated H-bronzes of NbVO 5 , niobium borides and deuterides, , and a variety of niobates. − There have also been a number of 93 Nb NMR studies featuring a variety of modern two-dimensional (2D) solid-state NMR experiments, including multiple quantum magic-angle spinning (MQMAS) and satellite-transition magic-angle spinning (STMAS) experiments, which are used for resolving peaks that may be obscured due to broad overlapping quadrupolar NMR patterns, as well as nutation and 2D-exchange NMR. − …”