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Original scientific paper
https://doi.org/10.5562/cca3538

Some Observations on Triplet Ground-States in the Context of ‘Topological’ (HLPM) Ring-Currents in Conjugated Systems

Timothy K. Dickens   ORCID icon orcid.org/0000-0003-0342-3597 ; Peterhouse, Cambridge CB2 1RD, England, United Kingdom
Roger B. Mallion   ORCID icon orcid.org/0000-0002-3642-269X ; Peterhouse, Cambridge CB2 1RD, England, United Kingdom

Fulltext: english, pdf (2 MB) pages 445-455 downloads: 261* cite
APA 6th Edition
Dickens, T.K. & Mallion, R.B. (2019). Some Observations on Triplet Ground-States in the Context of ‘Topological’ (HLPM) Ring-Currents in Conjugated Systems. Croatica Chemica Acta, 92 (4), 445-455. https://doi.org/10.5562/cca3538
MLA 8th Edition
Dickens, Timothy K. and Roger B. Mallion. "Some Observations on Triplet Ground-States in the Context of ‘Topological’ (HLPM) Ring-Currents in Conjugated Systems." Croatica Chemica Acta, vol. 92, no. 4, 2019, pp. 445-455. https://doi.org/10.5562/cca3538. Accessed 20 Apr. 2021.
Chicago 17th Edition
Dickens, Timothy K. and Roger B. Mallion. "Some Observations on Triplet Ground-States in the Context of ‘Topological’ (HLPM) Ring-Currents in Conjugated Systems." Croatica Chemica Acta 92, no. 4 (2019): 445-455. https://doi.org/10.5562/cca3538
Harvard
Dickens, T.K., and Mallion, R.B. (2019). 'Some Observations on Triplet Ground-States in the Context of ‘Topological’ (HLPM) Ring-Currents in Conjugated Systems', Croatica Chemica Acta, 92(4), pp. 445-455. https://doi.org/10.5562/cca3538
Vancouver
Dickens TK, Mallion RB. Some Observations on Triplet Ground-States in the Context of ‘Topological’ (HLPM) Ring-Currents in Conjugated Systems. Croatica Chemica Acta [Internet]. 2019 [cited 2021 April 20];92(4):445-455. https://doi.org/10.5562/cca3538
IEEE
T.K. Dickens and R.B. Mallion, "Some Observations on Triplet Ground-States in the Context of ‘Topological’ (HLPM) Ring-Currents in Conjugated Systems", Croatica Chemica Acta, vol.92, no. 4, pp. 445-455, 2019. [Online]. https://doi.org/10.5562/cca3538

Abstracts
When the quasi graph-theoretical Hückel–London–Pople–McWeeny (HLPM) approach is used to calculate ‘topological’ π-electron ring-currents and bond-currents in conjugated hydrocarbons, a problem is identified that occurs whenever application of the Aufbau process gives rise to a π-electronic ground-state configuration that is a triplet. This circumstance seems to occur only occasionally and, even when it does, the generally somewhat outré molecular graphs in question appear unlikely to represent extant or viable conjugated systems. The molecular graphs of four examples are used to illustrate this ‘triplet ground-state problem’, only one of which represents a hydrocarbon that has actually been synthesised. It is pointed out that the ‘triplet ground-state problem’ does constitute an intrinsic limitation of the HLPM approach. It is, though, a limitation that is also necessarily inherent in other equivalent (though ostensibly different) methods of calculating magnetic properties due to π-electron ring-currents — methods that are likewise founded on the Hückel molecular-orbital conventions. When a triplet ground-state arises, topological ring-currents and bond-currents cannot be calculated by the HLPM method and its equivalents. Infinite paramagnetism is formally to be predicted in such situations.

Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 International License.

Keywords
Topological Ring-Currents in Conjugated Systems; π-Electron Triplet Ground-States; Aufbau Principle; Infinite Paramagnetism

Hrčak ID: 228120

URI
https://hrcak.srce.hr/228120

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