HOMAc: A Parameterization of the Harmonic Oscillator Model of Aromaticity (HOMA) That Includes Antiaromaticity

The Journal of Organic Chemistry, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 15, 2025

The harmonic oscillator model of aromaticity (HOMA) offers a straightforward route to quantifying that requires no other information than the bond lengths conjugated ring in question. Given such is often readily obtainable from quantum-chemical calculations, it pertinent improve this parametrized as much possible. Here, new version HOMA presented where, atypically, corresponding parameters are derived actual both aromatic and antiaromatic (rather nonaromatic) reference compounds, calculated with high-level method. resulting model, which we denote HOMAc, covers CC, CN, NN, CO bonds tested at eight different levels theory for 45 (single-ring, multi-ring, carbocyclic, N,O-heterocyclic) molecules across aromatic-antiaromatic spectrum. Thereby, found HOMAc provides description antiaromaticity better accord magnetic, energetic, π-delocalization-based data does standard parametrization HOMA. Altogether, results highlight possibility realize more reliable geometry-based probing (anti)aromaticity use substantial freedom choice

Language: Английский

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HOMA Index Establishes Similarity to a Reference Molecule

Journal of Chemical Information and Modeling, Journal Year: 2023, Volume and Issue: 63(24), P. 7744 - 7754

Published: Dec. 6, 2023

The article shows that the definition of HOMA index geometrical aromaticity satisfies axioms a similarity function between examined and benzene ring. Consequently, for purely mathematical reasons, works exceptionally well as an aromaticity: it expresses geometric to archetypal aromatic benzene. Thus, if molecule is geometrically similar benzene, then also chemically similar, therefore, aromatic. However, property legitimizes using HOMA-like indices express molecules other than whether cyclic or linear existing hypothetical. paper demonstrates example HOMA-similarity cyclohexane, which (relaxed)-saturicity not accompanied by strong structural strains steric hindrances. Further, shown can evaluate properties whole molecules, such 25 unbranched catacondensed isomers hexacene. exhibits significant quadratic correlation with total energy differences planar from nonplanar ones deviate. Moreover, hexacene significantly correlates Kekulé count connected resonance in Hückel approximation. As result, study be used only analyses but general chemical descriptor applicable rings, chains, composed molecular moieties, even molecules.

Language: Английский

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py.Aroma: An Intuitive Graphical User Interface for Diverse Aromaticity Analyses

Published: June 21, 2024

The nucleus-independent chemical shift (NICS) criterion plays a significant role in evaluating (anti-)aromaticity. While readily accessible even for non-computational chemists, adding ghost atoms multi-points NICS evaluations poses challenge. In this note, I introduce py.Aroma, freely available and open-source Python package designed specifically analyzing Through its user-friendly graphical interface, py.Aroma simplifies enhances aromaticity analyses by offering key features such as HOMA/HOMER index computation, Gaussian-type input file generation diverse calculations corresponding output processing, NMR spectra plotting, generating computational supporting information (SI) scientific manuscripts. Additionally, pre-compiled executables macOS Windows are at https://wongzit.github.io/program/pyaroma. Make facilitate accessibility users lacking programming experience or time constraints. believe will prove to be valuable tool the chemistry community.

Language: Английский

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False Identification of (Anti)aromaticity in Polycyclic Molecules in Ground and Excited States Through Incorrect Use of NICS

Journal of Physical Organic Chemistry, Journal Year: 2025, Volume and Issue: 38(3)

Published: Feb. 10, 2025

ABSTRACT Aromaticity is a key concept in physical organic chemistry. However, as it cannot be measured directly, assessed indirectly via other properties (energetic, electronic, geometric and magnetic). Although these describe aromaticity, they are not solely related to aromaticity the observed values also can stem from, for example, magnetically induced local currents at certain atoms or groups, strain σ‐skeleton. This lead misinterpretations. Here, we highlight pitfall (anti)aromaticity assessment of polycyclic molecules when mainly based on nucleus independent chemical shifts (NICSs). The NICS index misinterpreted indicate ‘aromaticity’ ‘antiaromaticity’ nonaromatic rings result paratropic diatropic ring adjacent rings. We explore if such false indications by (i) stronger Baird‐aromatic ‐antiaromatic excited states (mainly triplet quintet, but singlet) than closed‐shell singlet ground states, (ii) current an causes weaker one ‘antiaromaticity’. Based our computations conclude that larger aromatic all types (e.g., state cyclooctatetraene ring) have greater influence smaller ones, yet, see no indication effect states. Instead, annulene more influential their (antiaromatic) regardless (aromatic) ones.

Language: Английский

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3,4‐Dimethylenecyclobutene: A Building Block for Design of Macrocycles with Excited State Aromatic Low‐Lying High‐Spin States

Chemistry - A European Journal, Journal Year: 2024, Volume and Issue: 30(27)

Published: March 4, 2024

Abstract 3,4‐Dimethylenecyclobutene ( DMCB ) is an unusual isomer of benzene. Motivated by recent synthetic progress to substituted derivatives this scaffold, we carried out a theoretical and computational analysis with particular focus on the extent (anti)aromatic character in lowest excited states different multiplicities. We found that parent non‐aromatic its singlet ground state (S 0 ), triplet (T 1 while it aromatic quintet (Q as represented multiplicity cyclobutadiene CBD ring two uncoupled same‐spin methylene radicals. Interestingly, Q state, despite having four unpaired electrons, placed merely 4.8 eV above S , there corresponding tetraradical 0.16 above. The potentially highly useful structural motif for design larger molecular entities interesting optoelectronic properties. Here, designed macrocycles composed fused units, according our computations, these have low‐lying nonet i. e ., octaradical states) at energies 2.40 0.37 their result local Hückel‐ Baird‐aromatic individual 6π‐ 4π‐electron monocycles.

Language: Английский

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Effect of Benzo‐Annelation on Triplet State Energies in Polycyclic Conjugated Hydrocarbons

Chemistry - A European Journal, Journal Year: 2024, Volume and Issue: 30(29)

Published: March 16, 2024

Abstract In a series of earlier studies, the effect benzo‐annelation was found to be useful tool for tuning aromaticity in polycyclic conjugated compounds desired level. this work we studied (anti)aromaticity benzo‐annelated derivatives three hydrocarbons (anthracene, fluoranthene and biphenylene) their lowest lying singlet (S 0 ) triplet (T 1 states by means energy (ef), harmonic oscillator model (HOMA), multicentre delocalization indices (MCI), magnetically induced current densities (MICDs) nucleus independent chemical shifts (NICS). We showed that is topology‐based which can used modify T state excitation energies ( E )). A quantitative established being able accurately predict based only on numbers angularly, linearly geminally annelated benzene rings. addition, it demonstrated directly related (anti)aromatic character central ring molecules S state.

Language: Английский

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Excited-state protonation and reduction enables the umpolung Birch reduction of naphthalenes

Chem, Journal Year: 2024, Volume and Issue: unknown

Published: Nov. 1, 2024

Language: Английский

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Polycyclic Heteroaromatic π‐Linkers Provide Dithienylethene Switches with Favorable Thermal and Photochemical Properties for Solar‐Energy Storage

ChemPhotoChem, Journal Year: 2024, Volume and Issue: 8(7)

Published: Feb. 9, 2024

Abstract Dithienylethene photoswitches with an aromatic π‐linker as the bridge between two thiophene units are attractive starting materials for developing molecular solar thermal energy (MOST) storage systems, partly because aromaticity of their ring‐open forms is a favorable feature regard to energy‐storage densities ring‐closed produced by photoinduced electrocyclization (photocyclization) reactions. At same time, this typically leads small barriers cycloreversion reactions, which not desirable in context. Here, we use computational methods show that problem can be circumvented polycyclic heteroaromatic π‐linkers. Specifically, through tuning character individual rings such (like indole or isoindole), it shown possible strike delicate balance seemingly contrasting requirements simultaneously achieving both high density and large barrier. Furthermore, design also found provide quick efficient photocyclization reaction, owing onset excited‐state antiaromaticity upon light absorption form. Altogether, dithienylethenes π‐linkers appear have photochemical properties suitable further development into future MOST systems.

Language: Английский

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Aromaticity and Antiaromaticity

Published: May 17, 2024

During the last decades, concept of aromaticity has evolved and broadened to incorporate new types such as σ-, δ-, ϕ-aromaticity, all-metal aromaticity, spherical three-dimensional hyperaromaticity, open-shell systems, excited state Möbius aromaticity. Not only have appeared but also aromatic species species, heteroderivatives metallabenzenes, metallabenzynes, many others. The study this complex variety different aromaticities required development methods for its detection that are usually based on fact molecules or most these properties: (i) a continuous electron delocalization, (ii) more stability than one would expect, (iii) bond length equalization, (iv) particular chemical reactivity, (v) differencial spectroscopic properties, (vi) special response in presence magnetic fields. Although been known nearly two centuries, there is no way measure it experimentally. To gain insight into exact nature, examine several abovementioned characteristics, namely, geometrical, electronic, magnetic, thermodynamic, reactivity properties. In years, we seen advances evaluated. chapter discusses, first, second, examines measures third, reviews rules and, finally reports series metallabenzenes related compounds.

Language: Английский

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Cyclo[n]carbons and catenanes from different perspectives: disentangling the molecular thread

Physical Chemistry Chemical Physics, Journal Year: 2023, Volume and Issue: 25(43), P. 29386 - 29403

Published: Jan. 1, 2023

All-carbon atomic rings, cyclo[ n ]carbons, have recently attracted vivid attention of experimentalists and theoreticians.

Language: Английский

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