Thermoelectric Properties of Fe0.2Co3.8Sb12-xTex ... - Physics

Heteronuclear Double Quantum Correlation Experiments
Involving Protons for the study of Partially Ordered and
Rigid Systems
Y. Jayasubba Reddy a,b and K.V. Ramanathan a
a NMR research Center, Indian Institute of Science Bangalore-560012, India
b Departmment of Physics
The current objective of our research is to develop and apply high resolution solid state NMR
methods to study the intermolecular interactions and 3D molecular structure of small molecules
(like drugs, tri and octa peptides and thermotropic liquid crystals) at isotopic natural abundance.
1 H NMR chemical shifts and dipolar couplings are the powerful probe for intermolecular
interactions, more specifically H-bonding, cis-trans conformation, π-π interactions and
dimerization, which control the self assembly of molecules in the solid state.
While considering all these advantages we have utilized 1 H based heteronuclear correlation
experiments. Multiple quantum correlation spectroscopy in the case of rigid and semi rigid
systems can provide useful proximity information, as the coherences can be generated between
dipolar coupled spin systems. Here we present our efforts in utilizing proton double quantum and
carbon single quantum correlation experiments for the case of static oriented liquid crystal
samples and rigid biological samples. Correlations based on both scalar and dipolar couplings are
being explored. Examples of studies with some proline based tripeptides which exhibit cis-trans
isomerism, thiophene based systems and a liquid crystalline material will be presented. To
confirm the resonance assignments, we have also used the GIPAW module contained in the open
source Quantum Esspresso (QE) code and chemical shifts with reasonable agreement with
experiment have been obtained.