The coupling constant polarizability and hyperpolarizabilty of ¹J(NH) in N‐methylacetamide, and its application for the multipole spin–spin coupling constant polarizability/reaction field approach to solvation

Abstract

We present a benchmark study of a combined multipole spin-spin coupling constant (SSCC) polarizability/reaction field (MJP/RF) approach to the calculation of both specific and bulk solvation effects on SSCCs of solvated molecules. The MJP/RF scheme is defined by an expansion of the SSCCs of the solvated molecule in terms of coupling constant dipole and quadrupole polarizabilities and hyperpolarizabilities derived from single molecule ab initio calculations. The solvent electric field and electric field gradient are calculated based on data derived from molecular dynamics (MD) simulations thereby accounting for solute-solvent dynamical effects. The MJP/RF method is benchmarked against polarizable QM/MM calculations for the one-bond N-H coupling constant in N-methylacetamide. The best agreement between the MJP/RF and QM/MM approaches is found by truncating the electric field expansion in the MJP/RF approach at the linear electric field level. In addition, we investigate the sensitivity of the results due to the choice of one-electron basis set in the ab initio calculations of the coupling constant (hyper-)polarizabilities and find that they are affected by the basis set in a way similar to the coupling constants themselves.

First hyperpolarizability of water in bulk liquid phase: long-range electrostatic effects included via the second hyperpolarizability

“…For pedagogical reasons, we will first highlight here the limitation of this gas-phase reference model, that was already mentioned in the literature. 36,57 If the linear proportionality factor g 0 is known, and the same for all molecules, this approach would be very helpful: the liquid first hyperpolarizability depends only on e env . An MD simulation can provide e env for each molecule, and the liquid phase first hyperpolarizability is calculated using eqn (5), so that no expensive QM/MM approach is needed.…”

“…Such limitations of perturbation field expansions to model solvation effects had already been discussed in the literature. When studying the nuclear magnetic shielding tensors of the atoms of N-methylacetamide solvated by liquid water, Kjaer et al 36 have shown that the field experienced by the nuclei is very inhomogeneous, so that considering one averaged field from all configurations and/or across all nuclei is not a good approximation. 3.2.2 Separation into short and long-range neighbors.…”

“…In a second step, possessing a database of {b env ,g env } for individual molecules in liquid water, we can additionally scrutinize the validity of the field perturbation approach represented by eqn (2). Similar field expansions for the calculation of solvent effects have been tested for observables such as nuclear magnetic shieldings, 36 or linear and non linear optical properties. 37 However, the precision of the field expansion for the non-linear optical properties were limited, 37 and more terms are needed in the perturbation expression.…”

CCSD‐CTOCD static dipole shielding polarizability for quantification of the chiral NMR effects in oxaziridine derivatives

“…Consequently, we have analyzed the convergence of the calculated value of the pseudo-scalar r ð1Þ I with a hierarchy of Dunning's correlation consistent basis sets for the considered (R)-N-fluor-C-methyl-oxa-aziridine. In Table 1, our results of r ð1Þ I for heavy nuclei 13 C, 14 N, 17 O, and 19 F are shown. We present the paramagnetic, D, and total contributions, which have been computed at the CHF-QR(CTOCD-DZ) level of theory.…”

“…The effects of an electric field on NMR spectral parameters have been theoretically determined since some time ago, [3,[6][7][8][9][10][11][12][13][14] either in a purely analytically manner through quadratic response (QR) methods or by numerical differentiation of analytical shielding tensors. Even though there are predominate calculations at the coupled Hartree-Fock (CHF) level, correlation contributions may be important as the nuclear magnetic shieldings are, in many molecules, strongly affected by electron correlation.…”