Reference interaction site model self-consistent field with constrained spatial electron density approach for nuclear magnetic shielding in solution

Abstract

We propose a new hybrid approach combining quantum chemistry and statistical mechanics of liquids for calculating the nuclear magnetic resonance (NMR) chemical shifts of solvated molecules. Based on the reference interaction site model self-consistent field with constrained spatial electron density distribution (RISM–SCF–cSED) method, the electronic structure of molecules in solution is obtained, and the expression for the nuclear magnetic shielding tensor is derived as the second-order derivative of the Helmholtz energy of the solution system. We implemented a method for calculating chemical shifts and applied it to an adenine molecule in water, where hydrogen bonding plays a crucial role in electronic and solvation structures. We also performed the calculations of 17O chemical shifts, which showed remarkable solvent dependence. While converged results could not be sometimes obtained using the conventional method, in the present framework with RISM–SCF–cSED, an adequate representation of electron density is guaranteed, making it possible to obtain an NMR shielding constant stably. This introduction of cSED is key to extending the method’s applicability to obtain the chemical shift of various chemical species. The present demonstration illustrates our approach’s superiority in terms of numerical robustness and accuracy.

The accuracy limit of chemical shift predictions for species in aqueous solution

“…As an alternative to continuum calculations we have in the past investigated the performance of the embedded cluster reference interaction site model (EC-RISM) as a solvation approach for QM methods in the context of NMR predictions. 27,33 This model combines calculations of the electronic and liquid structure by adding the interaction of a set of polarizing background charges to the electronic Hamiltonian which, as opposed to continuum models, represent the electrostatic potential distribution derived from the solute–solvent site distribution functions (SDFs) of an atomistically resolved solvent description within the 3D RISM approximation. In this way, the effect of directional hydrogen bonds can be mimicked even in the absence of explicit solvent molecules.…”

Vibrational Self-Consistent Field (VSCF) and Post-VSCF Method Calculations Combined with the Reference Interaction Site Model Self-Consistent Field Method Coupled with the Constrained Spatial Electron Density Distribution: Applications to NaHCOO in Aqueous Phase

“…To address these challenges, we have developed quantum chemical computations using the reference interaction site model self-consistent field method in conjunction with the constrained spatial electron density distribution (RISM–SCF–cSED). , This method combines principles from both quantum and statistical mechanics and has demonstrated versatility across various solvent systems, encompassing protic and aprotic solvents and supercritical water (SCW) systems. − In a previous investigation, we successfully expounded upon the minor nonlinear Raman shift (∼10 cm –1 ) observed in the CN stretching vibration of p -aminobenzonitrile ( p -ABN) relative to the reduced density of SCW . Additionally, we elucidated the changes in Raman intensity exhibited by p -nitroaniline ( p NA) under different solvent environments, including SCW …”

RISMiCal: A software package to perform fast RISM/3D‐RISM calculations

“…88,89 The RISM/3D-RISM program has also been implemented in quantum chemistry program packages such as Amsterdam Density Functional, 90 SALMON, 91 Quantum ESPRESSO, 92 and GAMESS. 93 These packages have been widely used in solvation studies of various molecular systems. However, with the developments in computational molecular science, solvation calculations for more complex systems are required, and as mentioned above, the development of even faster 3D-RISM programs is needed.…”