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Title: p -Carborane Conjugation in Radical Anions of Cage–Cage and Cage–Phenyl Compounds

Abstract

Optical electron transfer (intervalence) transitions in radical anions of p-carborane oligomers attest to delocalization of electrons between two p-carboranes cages or a p-carborane and a phenyl ring. Oligomers of the 12 vertex p-carborane (C 2B 10H 12) cage, [12], with up to 3 cages were synthesized, as well as p-carboranes with one or two trimethylsilylphenyl groups, [6], attached to the carbon termini. Pulse radiolysis in tetrahydrofuran produced radical anions, determined redox potentials by equilibria and measured their absorption spectra. Density functional theory computations provided critical insight into the optical electron transfer bands and electron delocalization. One case, [6–12–6], showed both Robin–Day class II and III transitions. The class III transition resulted from a fully delocalized excess electron across both benzene rings and the central p-carborane, with an electronic coupling H ab = 0.46 eV between the cage and either benzene. This unprecedented finding shows that p-carborane bridges are not simply electron withdrawing insulators. In other cases with more than ~1/2 of the excess electron localized on a [12], large cage distortions were triggered, producing a partially open cage with a nido-like structure. This resulted in class II transitions with similar Hab but massive reorganization energies. The computations also predicted delocalizationmore » in radical cations, but complexities in cation formation allowed only tentative experimental support of the predictions. Thus, the results with anions provide clear evidence for carborane conjugation that might be exploited in molecular wire materials, which are classically composed of all π-conjugated molecules.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3];  [1];  [4]; ORCiD logo [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Dept.
  2. Academy of Sciences of the Czech Republic (ASCR), Prague (Czech Republic). Inst. of Organic Chemistry and Biochemistry
  3. Brookhaven National Lab. (BNL), Upton, NY (United States). Chemistry Dept.; Monash Univ., Victoria (Australia). School of Chemistry
  4. Academy of Sciences of the Czech Republic (ASCR), Prague (Czech Republic). Inst. of Organic Chemistry and Biochemistry; Univ. of Colorado, Boulder, CO (United States). Dept. of Chemistry and Biochemistry
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division; National Science Foundation (NSF); Academy of Sciences of the Czech Republic (ASCR), Prague (Czech Republic). Inst. of Organic Chemistry and Biochemistry
OSTI Identifier:
1425003
Report Number(s):
BNL-114846-2017-JAAM
Journal ID: ISSN 1089-5639; TRN: US1801995
Grant/Contract Number:  
SC0012704; CHE 1566435; 61388963
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
Additional Journal Information:
Journal Volume: 122; Journal Issue: 3; Journal ID: ISSN 1089-5639
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY

Citation Formats

Cook, Andrew R., Valášek, Michal, Funston, Alison M., Poliakov, Pavel, Michl, Josef, and Miller, John R. p -Carborane Conjugation in Radical Anions of Cage–Cage and Cage–Phenyl Compounds. United States: N. p., 2017. Web. doi:10.1021/acs.jpca.7b10885.
Cook, Andrew R., Valášek, Michal, Funston, Alison M., Poliakov, Pavel, Michl, Josef, & Miller, John R. p -Carborane Conjugation in Radical Anions of Cage–Cage and Cage–Phenyl Compounds. United States. doi:10.1021/acs.jpca.7b10885.
Cook, Andrew R., Valášek, Michal, Funston, Alison M., Poliakov, Pavel, Michl, Josef, and Miller, John R. Thu . "p -Carborane Conjugation in Radical Anions of Cage–Cage and Cage–Phenyl Compounds". United States. doi:10.1021/acs.jpca.7b10885. https://www.osti.gov/servlets/purl/1425003.
@article{osti_1425003,
title = {p -Carborane Conjugation in Radical Anions of Cage–Cage and Cage–Phenyl Compounds},
author = {Cook, Andrew R. and Valášek, Michal and Funston, Alison M. and Poliakov, Pavel and Michl, Josef and Miller, John R.},
abstractNote = {Optical electron transfer (intervalence) transitions in radical anions of p-carborane oligomers attest to delocalization of electrons between two p-carboranes cages or a p-carborane and a phenyl ring. Oligomers of the 12 vertex p-carborane (C2B10H12) cage, [12], with up to 3 cages were synthesized, as well as p-carboranes with one or two trimethylsilylphenyl groups, [6], attached to the carbon termini. Pulse radiolysis in tetrahydrofuran produced radical anions, determined redox potentials by equilibria and measured their absorption spectra. Density functional theory computations provided critical insight into the optical electron transfer bands and electron delocalization. One case, [6–12–6], showed both Robin–Day class II and III transitions. The class III transition resulted from a fully delocalized excess electron across both benzene rings and the central p-carborane, with an electronic coupling Hab = 0.46 eV between the cage and either benzene. This unprecedented finding shows that p-carborane bridges are not simply electron withdrawing insulators. In other cases with more than ~1/2 of the excess electron localized on a [12], large cage distortions were triggered, producing a partially open cage with a nido-like structure. This resulted in class II transitions with similar Hab but massive reorganization energies. The computations also predicted delocalization in radical cations, but complexities in cation formation allowed only tentative experimental support of the predictions. Thus, the results with anions provide clear evidence for carborane conjugation that might be exploited in molecular wire materials, which are classically composed of all π-conjugated molecules.},
doi = {10.1021/acs.jpca.7b10885},
journal = {Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory},
issn = {1089-5639},
number = 3,
volume = 122,
place = {United States},
year = {2017},
month = {12}
}

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Works referencing / citing this record:

Thermal and Photophysical Properties of Highly Quadrupolar Liquid-Crystalline Derivatives of the [ closo -B 12 H 12 ] 2− Anion
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Thermal and Photophysical Properties of Highly Quadrupolar Liquid-Crystalline Derivatives of the [ closo -B 12 H 12 ] 2− Anion
journal, January 2019

  • Ali, Muhammad O.; Lasseter, John C.; Żurawiński, Remigiusz
  • Chemistry - A European Journal, Vol. 25, Issue 10
  • DOI: 10.1002/chem.201805392

Dinuclear acetylide-bridged ruthenium( ii ) complexes with rigid non-aromatic spacers
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  • Naik, Surabhi; Scottwell, Synøve Ø.; Li, Hsiu L.
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