25 years of NICS - much more than nothing!

Puchta, Ralph; Đorđević, Slađana; Radenković, Slavko; Jiao, Haijun; Hommes, Nicolaas J. R. van Eikema

doi:10.2298/jsc211203057p

Cited by 5 publications

(3 citation statements)

References 78 publications

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“…[38] One of the most well-known magnetic indexes in measuring the aromaticity of rings is the nucleus-independent chemical shift (NICS). [37,39] Reversing the sign of the magnetic shielding at a ring center gives the NICS value of the ring. Negative NICS values mean aromatic and positive for antiaromatic.…”

Section: Organic Bases Have Received Considerable Attention Due To Theirmentioning

confidence: 99%

Predicting a New Δ‐Proton Sponge‐Base of 4,12‐Dihydrogen‐4,8,12‐triazatriangulene through Proton Affinity, Aromatic Stabilization Energy, and Aromatic Magnetism

Al-Yassiri

Puchta

2023

ChemPhysChem

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Herein, we report designing a new Δ (delta‐shaped) proton sponge base of 4,12‐dihydrogen‐4,8,12‐triazatriangulene (compound 1) and calculating its proton affinity (PA), aromatic stabilization, natural bond orbital (NBO), electron density ρ(r), Laplacian of electron density ∇2ρ(r), (2D‐3D) multidimensional off‐nucleus magnetic shielding (σzz(r) and σiso(r)), and scanning nucleus‐independent chemical shift (NICSzz and NICS). Density functional theory (DFT) at B3LYP/6‐311+G(d,p), ωB97XD/6‐311+G(d,p), and PW91/def2TZVP were used to compute the magnetic shielding variables. In addition, relevant bases like pyridine, quinoline, and acridine were also studied and compared. The protonation of compound 1 yields a highly symmetric carbocation of three Hückel benzenic rings. Comparing our findings of the studied molecules showed that compound 1 precedes others in PA, aromatic isomerization stabilization energy, and basicity. Therefore, the basicity may be enhanced when a conjugate acid gains higher aromatic features than its unprotonated base. Both multidimensional σzz(r) and σiso(r) off‐nucleus magnetic shieldings outperformed electron‐based techniques and can visually monitor changes in aromaticity that occur by protonation. The B3LYP/6‐311+G(d,p), ωB97XD/6‐311+G(d,p), and PW91/def2TZVP levels showed no significant differences in detailing isochemical shielding surfaces.

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Section: Organic Bases Have Received Considerable Attention Due To Theirmentioning

confidence: 99%

Predicting a New Δ‐Proton Sponge‐Base of 4,12‐Dihydrogen‐4,8,12‐triazatriangulene through Proton Affinity, Aromatic Stabilization Energy, and Aromatic Magnetism

Al-Yassiri

Puchta

2023

ChemPhysChem

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“…It has been demonstrated that NICS values calculated for osmabenzenes are dominantly influenced by the local currents around the metal atom . Thus, the single-point NICS index, − which is one of the most employed aromaticity measurements, is not a reliable tool for analyzing the metallabenzenes aromaticity.…”

Section: Introductionmentioning

confidence: 99%

Aromaticity of Osmaacenes in Their Lowest-Lying Singlet and Triplet States

Radenković

Solà

2023

Inorg. Chem.

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The aromatic character of a series of osmaacenes in their lowest-lying singlet and triplet states was thoroughly examined by means of the magnetically induced current densities and multicentre delocalization indices (MCIs). Both employed approaches agree that the osmabenzene molecule (OsB) in the S0 state exhibits dominant π-Hückel-type aromatic character, with a small but nonnegligible amount of π-Craig–Möbius aromaticity. Contrary to benzene, which is antiaromatic in the T1 state, OsB preserves some of its aromaticity in the T1 state. In higher members of the osmaacene series in the S0 and T1 states, the central Os-containing ring becomes nonaromatic, acting as a barrier between the two side polyacenic units which, on the other hand, exhibit a significant extent of π-electron delocalization.

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“…Gerothanassis et al published two review papers on DFT prediction of d( 13 C) and d( 1 H) chemical shifts and 3 J( 13 C-O-O-1 H) coupling constants used in structural studies on hydroperoxides. 18,19 An interesting review on calculation and applications of magnetic index of aromaticity, nuclear independent chemical shift (NICS) was published by Puchta et al 20 Intermolecular interactions are of utmost importance in both natural producs and material science and NMR is a very useful tool in their experimental and theoretical characteristic.…”

Section: Introductionmentioning

confidence: 99%

Theory and computation of nuclear shielding

2023

Nuclear Magnetic Resonance

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This chapter continues earlier reviews of essential works on theoretical issues of nuclear magnetic shieldings published from 1 January to 31 December 2022. As previously, the chapter concentrates on theoretical calculations of nuclear shielding parameters and/or chemical shifts in case of free molecules in the gas phase and solution, and in some cases in the solid state using a periodic formulation. The nuclear shieldings in solution are mainly calculated using inexpensive polarizable continuum model of solvent (PCM). The use of discrete solvent molecules (in particular water and other polar solvents), which is essential for correct description of hydrogen bonding, is often omitted by numerous authors. Most calculations use a relatively simple and fast, but reliable density functional theory (DFT) combined with gauge-including atomic orbital (GIAO) approach. On the other hand, reports on prediction of nuclear magnetic shielding parameters using high level theoretical methods combined with large and flexible basis sets are not so common due to the enormous computational cost. In addition, correction of raw theoretical nuclear magnetic shieldings due to ro-vibration (zero-point vibration correction, ZPVC) and temperature corrections (TC), as well as implicit and explicit solvent effects and relativistic corrections are not often reported.

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25 years of NICS - much more than nothing!

Abstract: The famous aromaticity index NICS (Nucleus Independent Chemical Shift) was introduced 25 years ago. The authors use this anniversary for a short and incomplete personal retrospect.

Cited by 5 publications

References 78 publications

Predicting a New Δ‐Proton Sponge‐Base of 4,12‐Dihydrogen‐4,8,12‐triazatriangulene through Proton Affinity, Aromatic Stabilization Energy, and Aromatic Magnetism

Predicting a New Δ‐Proton Sponge‐Base of 4,12‐Dihydrogen‐4,8,12‐triazatriangulene through Proton Affinity, Aromatic Stabilization Energy, and Aromatic Magnetism

Aromaticity of Osmaacenes in Their Lowest-Lying Singlet and Triplet States

Theory and computation of nuclear shielding

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