Solvent Effects on ¹⁵N NMR Shielding of 1,2,4,5-Tetrazine and Isomeric Tetrazoles:  Continuous Set Gauge Transformation Calculation Using the Polarizable Continuum Model

Abstract

Solvent-induced effects on nitrogen NMR shielding of 1,2,4,5-tetrazine and two isomeric tetrazoles are calculated using density functional theory combined with the polarizable continuum model and using the continuous set gauge transformation. Direct and indirect solvent effects on shielding are also calculated. It has been shown that the observed solvent-induced shielding variation is more strongly related to the intensity of the solvent reaction field rather than on the change of molecular geometry induced by the solvent.

14,15N NMR Shielding Constants from Density Functional Theory

“…This assumption is supported by the results obtained by Manalo and co-workers. 28 All geometry optimizations and SCF calculations have been performed using Version 3.5 of the DEMON-KS 29 program, whereas the time-dependent calculations have been performed with Version 3.2 of the DEMON-DYNARHO program.…”

Interactions between pairs of antimalarial drugs studied by experimental and ab initio13C NMR chemical shifts

“…With the addition of the second drug, the total ion concentration in the sample also changes. In order to correct for this change, ammonium chloride was added to each drug alone to determine how much the 13 C chemical shifts in the drug change with ion concentration. This is then taken into account in determining how much of the chemical shift can be assigned to ring-current effects.…”

“…Sample and instrument temperatures were controlled at 298 K. Proton-decoupled 13 C spectra were acquired with WALTZ decoupling, a spectral width of 25149.3 Hz, and acquisition time of 1.301 s. Spectra were Table 3.…”

“…Supermolecular chemical shift calculations were done using the B3LYP 7,8 functional with a 6-31GŁŁ 9 basis set. The continuous set of gauge transformation 10 method with the polarizable continuum model 11,12 (PCM-CSGT) 13 was used to include solvent effects in the calculations. NICS 3 were calculated using CSGT.…”

“…The experimental determination of ring-current effects in these systems is fairly difficult as other contributions may be present. An internal reference is used to remove most of the bulk susceptibility effects, and corrections regarding ionic contributions have been addressed by measuring the changes in 13 C chemical shifts in the presence of NH 4 Cl.…”