Control of the orbital derealization and implications for molecular rectification in the radical anions of porphyrins with coplanar 90° and 180° β,β′-fused extensions

Wenbo, E; Kadish, KM; Sintic, PJ; Khoury, T; Govenlock, LJ; Ou, Z; Shao, J; Ohkubo, K; Reimers, JR; Fukuzumi, S; Crossley, MJ

Control of the orbital derealization and implications for molecular rectification in the radical anions of porphyrins with coplanar 90° and 180° β,β′-fused extensions

Wenbo, E Kadish, KM Sintic, PJ Khoury, T Govenlock, LJ Ou, Z Shao, J Ohkubo, K Reimers, JR

Fukuzumi, S Crossley, MJ

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Publication Type:: Journal Article
Citation:: Journal of Physical Chemistry A, 2008, 112 (3), pp. 556 - 570
Issue Date:: 2008-01-24

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Field	Value	Language
dc.contributor.author	Wenbo, E	en_US
dc.contributor.author	Kadish, KM	en_US
dc.contributor.author	Sintic, PJ	en_US
dc.contributor.author	Khoury, T	en_US
dc.contributor.author	Govenlock, LJ	en_US
dc.contributor.author	Ou, Z	en_US
dc.contributor.author	Shao, J	en_US
dc.contributor.author	Ohkubo, K	en_US
dc.contributor.author	Reimers, JR https://orcid.org/0000-0001-5157-7422	en_US
dc.contributor.author	Fukuzumi, S	en_US
dc.contributor.author	Crossley, MJ	en_US
dc.date.issued	2008-01-24	en_US
dc.identifier.citation	Journal of Physical Chemistry A, 2008, 112 (3), pp. 556 - 570	en_US
dc.identifier.issn	1089-5639	en_US
dc.identifier.uri	http://hdl.handle.net/10453/28169
dc.description.abstract	Through-porphyrin electronic communication is investigated using "linear-type" and "corner-type" bis(quinoxalino)porphyrins in free-base form and their ZnII, CuII, NiII, and PdII derivatives. These compounds are porphyrins with quinoxalines fused on opposite or adjacent β,β'-pyrrolic positions; they were synthesized from 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)- porphyrin-2,3,12,13- and -2,3,7,8-tetraone, respectively, by reaction with 1,2-phenylenediamine. The degree of electron spin derealization into the fused rings in the π-radical anions of the free-base and metal(II) bisquinoxalinoporphyrins was elucidated by electrochemistry, UV-vis absorption, and electron spin resonance (ESR) spectra of the singly reduced species and density functional theory calculations. Hyperfine splitting patterns in the ESR spectra of the π-radical anions show that symmetric molecules have delocalized electron spin, indicating that significant inter-quinoxaline interactions are mediated through the central porphyrin unit, these interactions being sufficient to guarantee throughmolecule conduction. However, when molecular symmetry is broken by tautomeric exchange of the inner nitrogen hydrogens in the free-base porphyrin with a corner-type quinoxaline substitution pattern, the π-radical anion becomes confined so that one quinoxaline group is omitted from spin derealization. This indicates the appearance of a unidirectional barrier to through-molecule conduction, suggesting a new motif for chemically controlled rectification. © 2008 American Chemical Society.	en_US
dc.relation.ispartof	Journal of Physical Chemistry A	en_US
dc.relation.isbasedon	10.1021/jp076406g	en_US
dc.title	Control of the orbital derealization and implications for molecular rectification in the radical anions of porphyrins with coplanar 90° and 180° β,β′-fused extensions	en_US
dc.type	Journal Article
utslib.citation.volume	3	en_US
utslib.citation.volume	112	en_US
utslib.for	0306 Physical Chemistry (incl. Structural)	en_US
utslib.for	0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics	en_US
utslib.for	0307 Theoretical and Computational Chemistry	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Mathematical and Physical Sciences
utslib.copyright.status	closed_access
pubs.issue	3	en_US
pubs.publication-status	Published	en_US
pubs.volume	112	en_US

Abstract:

Through-porphyrin electronic communication is investigated using "linear-type" and "corner-type" bis(quinoxalino)porphyrins in free-base form and their ZnII, CuII, NiII, and PdII derivatives. These compounds are porphyrins with quinoxalines fused on opposite or adjacent β,β'-pyrrolic positions; they were synthesized from 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)- porphyrin-2,3,12,13- and -2,3,7,8-tetraone, respectively, by reaction with 1,2-phenylenediamine. The degree of electron spin derealization into the fused rings in the π-radical anions of the free-base and metal(II) bisquinoxalinoporphyrins was elucidated by electrochemistry, UV-vis absorption, and electron spin resonance (ESR) spectra of the singly reduced species and density functional theory calculations. Hyperfine splitting patterns in the ESR spectra of the π-radical anions show that symmetric molecules have delocalized electron spin, indicating that significant inter-quinoxaline interactions are mediated through the central porphyrin unit, these interactions being sufficient to guarantee throughmolecule conduction. However, when molecular symmetry is broken by tautomeric exchange of the inner nitrogen hydrogens in the free-base porphyrin with a corner-type quinoxaline substitution pattern, the π-radical anion becomes confined so that one quinoxaline group is omitted from spin derealization. This indicates the appearance of a unidirectional barrier to through-molecule conduction, suggesting a new motif for chemically controlled rectification. © 2008 American Chemical Society.

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