Synthesis, complete NMR assignments, and NOE versus GIAO data assisted ab initio modelling the overall conformations of amide 3,4′-diquinolinyl sulfides in solution. Another approach to analysis of flexible systems

13C longitudinal relaxation time measurements and DFT-GIAO NMR computations for two ammonium ions of a tetraazamacrocyclic scorpiand system

“…Indeed, several forms of some multi-component systems initially located as their global energy minima were occasionally not recognized in solutions, by using typical GIAO-supported approaches [6, 78–80]. The majority of discrepancies of this kind was usually explained by specific solute–solvent effects only seldom adequately taken into account in the computational treatment in normal use.…”

“…Interestingly, both conformers N1 and N2 of H 4 1 4+ were previously recognized as forms most favored in the gas-phase [ 6 ], but they were not proposed finally as existing in the real aqueous medium on the basis of a ‘ solution environment (i.e., NMR spectroscopic) match criterion ’ [ 6 , 11 , 78 ]. Indeed, several forms of some multi-component systems initially located as their global energy minima were occasionally not recognized in solutions, by using typical GIAO-supported approaches [ 6 , 78 – 80 ]. The majority of discrepancies of this kind was usually explained by specific solute–solvent effects only seldom adequately taken into account in the computational treatment in normal use.…”

A Benefit of Using the IDSCRF- over UFF-Radii Cavities and Why Joint Correlations of NMR Chemical Shifts Can Be Advantageous: Condensed Pyridines as an IEF-PCM/GIAO/DFT Case Study

“…The correlations between predicted and observed δ K ’s were analyzed by a linear regression model, and calculated data were plotted against experimental data in the normal way. − ,,,, The greater value of r or r 2 was considered an indication of better adjustment of correlated data sets. In turn, the two statistical metrics, that is, the corrected root-mean-square deviation, CRMSD = [(1/ n )∑ i (δ K, i corr – δ K, i obsd ) 2 ] 1/2 (where n is the total number of δ K values in a set of data), and the corrected mean absolute deviation, CMAD = (1/ n )∑ i |δ K, i corr – δ K, i obsd |, were used as estimates of the uncertainties of results.…”

“…Simultaneous treatments of more than one type of nuclei ( 1 H, 13 C, 15 N, etc.) are scarce, − and only a few of them deal with single molecules (usually the H/C approach). − ,− However, there is no reason in principle to do such joint multinuclear analyses, provided that adequate reference standards of δ K ’s will be used. A linear relationship between δ H,C,... calcd and δ H,C,... obsd is implicitly assumed in this case, which is generally accepted for the results of highly accurate electron-correlated calculations involving a solvation model. − …”

Tautomeric populations of the charged species of 1,12-diamino-3,6,9-triazadodecane (SpmTrien) studied with computer simulations and cluster expansions

“…Tautomeric populations of each charge state were then obtained by constrained least‐squares fitting of the theoretically calculated 15 N NMR chemical shifts of the tautomers to the observed shifts. Correlation analyses of calculated chemical shieldings and experimental chemical shifts have been earlier used to analyze conformational and tautomeric mixtures . However, studies applying optimization techniques in determining populations are rare .…”