Color in bridge-substituted cyanines

Olsen, Seth (2016) Color in bridge-substituted cyanines. Journal of Physical Chemistry A, 120 51: 10245-10251. doi:10.1021/acs.jpca.6b10340


Author Olsen, Seth
Title Color in bridge-substituted cyanines
Journal name Journal of Physical Chemistry A   Check publisher's open access policy
ISSN 1089-5639
1520-5215
Publication date 2016-12-01
Year available 2016
Sub-type Article (original research)
DOI 10.1021/acs.jpca.6b10340
Open Access Status Not yet assessed
Volume 120
Issue 51
Start page 10245
End page 10251
Total pages 7
Place of publication Washington, DC United States
Publisher American Chemical Society
Language eng
Abstract Theories of color in cyanine dyes have evolved around the idea of a "resonance" of structures with distinct bonding and charge localization. Understanding the emergence of resonance models from the underlying many-electron problem remains a central issue for these systems. Here, the issue is addressed using a maximum-entropy approach to valence-bond representations of state-averaged complete-active space self consistent field models. The approach allows calculation of energies and couplings of high-energy valence bond structures that mediate superexchange couplings and chemical bonding. A series of valence-bond Hamiltonians for a series of bridge-substituted derivatives of Michler's hydrol blue (a monomethine cyanine) is presented. The Hamiltonians are approximated with a simple linear model parametrized by the Brown Okamoto sigma(+)(p) parameter of the bridge substituent. A quantitative lower bound on sigma(+)(p), beyond which a resonant cyanine-like ground state will not exist, is presented. The large effective coupling in two-state resonance models emerges from superexchange associated with either covalent bonding or charge-carrier delocalization, with the former contribution significantly the stronger. The results provide ab initio justification for empirical diabatic-state models of methine optical response. They are of general interest for understanding the optoelectronic response in cyanines.
Formatted abstract
Theories of color in cyanine dyes have evolved around the idea of a “resonance” of structures with distinct bonding and charge localization. Understanding the emergence of resonance models from the underlying many-electron problem remains a central issue for these systems. Here, the issue is addressed using a maximum-entropy approach to valence-bond representations of state-averaged complete-active space self-consistent field models. The approach allows calculation of energies and couplings of high-energy valence-bond structures that mediate superexchange couplings and chemical bonding. A series of valence-bond Hamiltonians for a series of bridge-substituted derivatives of Michler’s hydrol blue (a monomethine cyanine) is presented. The Hamiltonians are approximated with a simple linear model parametrized by the Brown–Okamoto σp+ parameter of the bridge substituent. A quantitative lower bound on σp+, beyond which a resonant cyanine-like ground state will not exist, is presented. The large effective coupling in two-state resonance models emerges from superexchange associated with either covalent bonding or charge-carrier delocalization, with the former contribution significantly the stronger. The results provide ab initio justification for empirical diabatic-state models of methine optical response. They are of general interest for understanding the optoelectronic response in cyanines.
Keyword Michlers Hydrol Blue
Period Transient Spectroscopy
Electronic-Absorption-Spectra
Tight-Binding Linkages
Essential-State Model
Asymptotic Band-Gap
Auramine-O
Energy-Transfer
Excited-State
Cationic Diarylmethanes
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID DP110101580
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Mathematics and Physics
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