Some Aspects of the NMR Spin spin Coupling Constant Calculation

P. F. PROVASI

Manaus

Congreso; Internacional Conference on Molecules, Polymers and Material Physics; 2014

p { margin-bottom: 0.08in; }Mostof the intrinsic properties of molecules formed by first and secondrow elements and which involve the formation and breaking of thechemical bonds, can be explained within a good approximation by thenon-relativist self consistent Hartree-Fock (HF) theory. Some other,more sensitive properties, like the parameter of the Nuclear MagneticResonance (NMR) spectroscopic parameters: nuclear magneticshielding (σ) and indirectnuclear spin-spin coupling constant (J) require for atheoretical reproduction a higher approximation like SOPPA,SOPPA(CCSD), MCSCF, CC and DFT without forgetting the important roleplayed by the basis set used to approximate atomic orbitals (AOs) ormolecular orbitals (MOs) inherent to the studied systems.TheNMR spectroscopy has been widely developed since its discovery by thegroups of Purcell and Bloch. The first theoretical explanation onthe electronic origin of J and sparameters was given by Ramsey and actually its application andinterest area goes from Physics and Chemistry to Biology andMedicine. Its spectroscopic parameters are highly sensitive toseveral intra- and inter-molecular factors which make NMR onepowerful analysis tools at the molecular level.Thissensitivity together with the growing viability of computationalresources let the search for a more accurate, and therefore, a moredetailed description of such molecular properties. In particular, thedependence of the J and sparameters with the molecular electronic structure, lets investigatethe electron correlation and relativistic corrections that affectthese parameters, consequently, provide a better understanding of themolecular structure and some factors influencing it.