Computational approach to molecular magnetic properties by continuous transformation of the origin of the current density

Efficient mapping of ring currents in fullerenes and other curved carbon networks

“…Such currents can be inferred indirectly from their effects on observable magnetic properties (exaltation of magnetisability [17][18][19], downfield chemical shifts of external hydrogen nuclei [20]) and properties that are sub-observables, in Hirschfelder's sense [21], such as the characteristically negative NICS value at the ring centre or some other chosen point [22]. Inferences of this type all have difficulties associated with masking of ring-current effects by other contributions to the property [23][24][25][26][27], but ring-current aromaticity can in fact be deduced directly from calculation of the induced current itself, by solution of the Schrödinger equation for the molecule immersed in the magnetic field, using an appropriate distributed-origin method [28][29][30][31]. The present paper is concerned with the application of this technique to fullerenes and similar curved-carbon molecules.…”

Polygonal current models for polycyclic aromatic hydrocarbons and graphene sheets of various shapes

“…The CTOCD-DZ predictions of magnetizability of the centersymmetric PAHs considered here are invariant in a translation of the gauge origin. [66,67,74] CTOCD-DZ magnetic shielding tensors are origin independent for all molecular point group symmetries. [66] At any rate, it should be recalled that the three components of the shielding tensor, and NICS, [52] at the CM of cyclic systems with D nh symmetry, are origin independent even if they are calculated by gaugeless basis sets within the common origin approach.…”

“…[66,67,74] CTOCD-DZ magnetic shielding tensors are origin independent for all molecular point group symmetries. [66] At any rate, it should be recalled that the three components of the shielding tensor, and NICS, [52] at the CM of cyclic systems with D nh symmetry, are origin independent even if they are calculated by gaugeless basis sets within the common origin approach. [74] For an assessment of the PCM model we compared values of n kgraph , the contribution of p-electrons to the out-of-plane magnetizability computed as described elsewhere, [29,30,33] with the corresponding n kcalc from the ab initio calculations.…”

“…The magnetic properties needed to determine the parameters of the model were calculated at the coupled Hartree-Fock level, within the procedure allowing for continuous translation of the origin of the current density-diamagnetic zero (CTOCD-DZ). [66][67][68][69][70] 6-31G** basis sets of Gaussian functions for C, B, N, and H atoms were used. The same basis sets were also used to optimize molecular geometries (using Gaussian03 [71] ) and to evaluate, via the SYSMO package, [72] r-and p-electron contributions to the out-of-plane components of magnetizability and magnetic shielding of points along the C n symmetry axis orthogonal to the molecular plane, at distance h from the origin.…”

Current density maps, magnetizability, and nuclear magnetic shielding tensors of bis-heteropentalenes. II. Furo-furan Isomers

“…The gauge invariant results obtained via the London orbitals, indicated by LO in Table II, are partitioned into diamagnetic, d , and paramagnetic, p , contributions, evaluated with respect to the center of mass. The notation adopted for the various CTOCD estimates [15][16][17][21][22][23][24] is the same as in paper I of this series. 6 The least symmetric molecule, furo͓3,4-b͔furan, has been studied only via the GIAO approach of the DALTON package.…”