Asymmetric charge separation and recombination in symmetrically functionalized σ–π hybrid oligosilanes
- Department of Chemistry; Johns Hopkins University; Baltimore; USA
The flexibility of σ-conjugated silanes presents new opportunities for manipulating charge generation, transport, and non-linear optical properties of materials. Recently we synthesized a series of acceptor–donor–acceptor (ADA) compounds in which a methylated oligosilane core (D) is flanked by electron-deficient cyanovinyl-substituted arenes (A). Based on a detailed characterization of the photophysics of ADA and donor–acceptor (DA) architectures using both steady state and ultrafast spectroscopic measurements we illustrate that asymmetric charge separation occurs directly following light absorption. Lippert analysis of solvatochromic emission indicates large changes in dipole moments on excitation consistent with the formation of dipolar emissive states. Time resolved absorption measurements reveal common excited-state relaxation behavior across molecular structures: spectral dynamics associated with the relaxation of nascent excited states occur on a common timescale for all structures within the same solvent environment, whereas charge recombination via excited-state decay consistently follows a common energy gap law. Ultrafast time-resolved Raman measurements reveal that reduction of the cyanovinyl moieties is instantaneous with excitation, with only minor shifts in vibrational features over the course of excited-state relaxation. We conclude that excited-state symmetry breaking that gives rise to asymmetric intramolecular charge transfer (ICT) is associated with the conformation of the central Si chain. In contrast, ultrafast solvent reorganization or solvent-controlled intramolecular dynamics only serve to stabilize nascent dipolar excited states, rather than induce charge separation from an initial quadrupolar state.
- Research Organization:
- Lawrence Berkeley National Laboratory-National Energy Research Scientific Computing Center
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- DOE Contract Number:
- AC02-05CH11231; SC0013906
- OSTI ID:
- 1492851
- Journal Information:
- Dalton Transactions, Journal Name: Dalton Transactions Journal Issue: 27 Vol. 46; ISSN 1477-9226; ISSN ICHBD9
- Country of Publication:
- United States
- Language:
- English
Similar Records
Concerted electron-proton transfer in the optical excitation of hydrogen-bonded dyes
Fast intramolecular electron transfer and dual fluorescence. Configurational change of the amino nitrogen (pyramidal{yields}planar)
Fluorescent Benzocoumarin-π-Extended Styryl Hybrids: Solvatochromism, Excess Dipole Moment, NLO Properties and DFT Study
Journal Article
·
Tue May 24 00:00:00 EDT 2011
· Proceedings of the National Academy of Sciences of the United States of America
·
OSTI ID:1065648
Fast intramolecular electron transfer and dual fluorescence. Configurational change of the amino nitrogen (pyramidal{yields}planar)
Journal Article
·
Sun Mar 31 23:00:00 EST 1996
· AIP Conference Proceedings
·
OSTI ID:21163627
Fluorescent Benzocoumarin-π-Extended Styryl Hybrids: Solvatochromism, Excess Dipole Moment, NLO Properties and DFT Study
Journal Article
·
Sun Jan 14 23:00:00 EST 2018
· Journal of Fluorescence (Online)
·
OSTI ID:22795673