Ab initio calculations on m-quinone. The ground state is a triplet

Fort, Raymond C.; Getty, Stephen J.; Hrovat, David A.; Lahti, Paul M.; Borden, Weston Thatcher

doi:10.1021/ja00045a031

Cited by 66 publications

(76 citation statements)

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“…Therefore, to confirm our prediction that the lowest singlet state of MBQ was 1 B 2 , rather than 1 A 1 as in MBQDM , all we needed to do was to assign the signals in Xuebin’s spectrum of MBQ .− 25. Calculations, using ezSpectrum,20 allowed Dr. Bo Chen in my research group to assign the signals in Xuebin’s NIPE spectrum of MBQ , and thus, confirm experimentally our computational prediction, made more than 20 years earlier,26 that the lowest singlet state of MBQ was 1 B 2 and not 1 A 1 24…”

Section: Analysis Of the Nipe Spectrum Of Meta‐benzoquinone Radicalsupporting

confidence: 63%

“…My own interest in MBQ also predated my group’s work on (CO) 4 ,8,10,15 not by one year, as in Xuebin’s case, but by 20 years. In 1992, my group published calculations, which made the surprising prediction that substitution of the oxygen atoms in MBQ for the CH 2 groups in meta‐ benzoquinodimethane ( MBQDM ) would have little effect on the energy difference between the lowest singlet state and the triplet ground state 26…”

Section: Analysis Of the Nipe Spectrum Of Meta‐benzoquinone Radicalmentioning

confidence: 99%

“…Therefore, in MBQ , the lowest singlet state is predicted not to be 1 A 1 , as in MBQDM , but to be 1 B 2 . The fact that an excited singlet state of MBQDM becomes the lowest state of MBQ is the reason why the substitution of O for CH 2 is calculated to have such a small effect on the energy difference between the lowest singlet state and the triplet ground state 26…”

Section: Analysis Of the Nipe Spectrum Of Meta‐benzoquinone Radicalmentioning

confidence: 99%

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The Unpredictability of Research Directions and the Synergy between Theory and Experiment in Physical‐Organic Chemistry

Borden

2015

Israel Journal of Chemistry

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Research projects in physical‐organic chemistry can go in unpredictable directions. One such project, described herein, began with the discovery of a large, imaginary, calculated vibrational frequency and soon led to the prediction that cyclobutanetetraone (CO)4 had a triplet ground state. Molecular orbital (MO) theory provided the understanding of why (CO)4 was calculated to have a planar triplet ground state and why, in contrast, (SiO)4 was calculated to have a tetrahedral singlet ground state. Qualitative MO theory, as well as calculations, also predicted that (CO)3, (CO)5, and (CO)6 should all be found to have singlet ground states. Testing experimentally these predictions about (CO)n molecules, n=3–6, led to a very fruitful collaboration with Dr. Xuebin Wang, who obtained the negative ion photoelectron (NIPE) spectra of the radical anions of these four molecules and also of (CS)4. Assignments of the signals in these five NIPE spectra required computing the vibrational progressions in them. The necessary acquisition of the ability to simulate the signals in NIPE spectra resulted in the successful analysis of the very complex spectrum of meta‐benzoquinone (MBQ) radical anion, which Dr. Wang had already obtained and published. Analysis of this spectrum confirmed the prediction, made more than 20 years previously, that the ordering of the two lowest singlet states in MBQ was reversed from that in meta‐benzoquinodimethane (MBQDM). The research described herein illustrates not only the unpredictability of where some research projects will eventually lead, but also the synergy between calculations and experiments in physical‐organic chemistry.

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Section: Analysis Of the Nipe Spectrum Of Meta‐benzoquinone Radicalsupporting

confidence: 63%

Section: Analysis Of the Nipe Spectrum Of Meta‐benzoquinone Radicalmentioning

confidence: 99%

Section: Analysis Of the Nipe Spectrum Of Meta‐benzoquinone Radicalmentioning

confidence: 99%

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The Unpredictability of Research Directions and the Synergy between Theory and Experiment in Physical‐Organic Chemistry

Borden

2015

Israel Journal of Chemistry

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“…[139,140] least one further good argument in favor of dimerization of monomer 3 as the source of the observed radicals: in this case, the energy required for diradical formation is compensated (at least partially) by the generation of two aromatic systems. However, what might be the constitution of those dimeric diradicals?…”

Section: The Radical Chain-growth Hypothesismentioning

confidence: 99%

The Gilch Synthesis of Poly(p‐phenylene vinylenes): Mechanistic Knowledge in the Service of Advanced Materials

Schwalm

Wiesecke

Immel

et al. 2009

Macromol. Rapid Commun.

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A consistent picture is presented of the mechanistic details and intermediates of the Gilch polymerization leading to poly(p-phenylene vinylenes) (PPVs). In-situ generated p-quinodimethanes are shown to be the real monomers, and spontaneous formation of the initiating radicals is effected by dimerization of some of these monomers to dimer diradicals, the latter also being the reason why significant amounts of [2.2]paracyclophanes are formed as side-products. Chain propagation predominantly proceeds by radical chain growth, occasionally interrupted by polyrecombination events between the growing α,ω-macro-diradicals. Based on this knowledge, oxygen is identified as a very efficient molar-mass regulating agent, and the temporary gelation of the reaction mixtures is interpreted to be the consequence of a very high entanglement of the polymers immediately after their formation. Last but not least, it is rationalized why the usually considered constitutional defects in Gilch PPVs might not be the only and most relevant ones with respect to the efficiency and durability of the organic light emitting devices produced thereof, and why cis-configurated halide-bearing vinylene moieties should be perceived as being among the most critical candidates. These considerations result in the recommendation of straightforward measures that should lead to clearly improved PPVs.

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“…Most of the known stable quinonoids were however derived from the parent para-quinone (I) and ortho-quinone (II). The meta-quinone has been shown to be a biradical species with a triplet ground state and a singlet-triplet separation gap at about 40 kJ/mol [3]. Recently, Siri and Braunstein (SB) [4] have been successful in synthesizing, for the first time, the novel molecule (III) which is formally a diamino derivative of meta-quinone.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure of zwitterionic diamino-meta-quinonoid molecules: identity of UV absorption bands

Delaere

Nam

Nguyen

2003

Chemical Physics Letters

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Ab initio calculations on m-quinone. The ground state is a triplet

Cited by 66 publications

References 0 publications

The Unpredictability of Research Directions and the Synergy between Theory and Experiment in Physical‐Organic Chemistry

The Unpredictability of Research Directions and the Synergy between Theory and Experiment in Physical‐Organic Chemistry

The Gilch Synthesis of Poly(p‐phenylene vinylenes): Mechanistic Knowledge in the Service of Advanced Materials

Electronic structure of zwitterionic diamino-meta-quinonoid molecules: identity of UV absorption bands

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