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Weingarten AS, Dannenhoffer AJ, Kazantsev RV, Sai H, Huang D, Stupp SI. Chromophore Dipole Directs Morphology and Photocatalytic Hydrogen Generation. J Am Chem Soc 2018; 140:4965-4968. [PMID: 29624383 PMCID: PMC6072259 DOI: 10.1021/jacs.7b12641] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The spontaneous self-assembly of chromophores into light-harvesting antennae provides a potentially low-cost approach to building solar-to-fuel conversion materials. However, designing such supramolecular architectures requires a better understanding of the balance between noncovalent forces among the molecular components. We investigated here the aqueous assembly of perylene monoimide chromophore amphiphiles synthesized with different substituents in the 9-position. The molecular dipole strength decreases as the nature of the substituent is altered from electron donating to electron withdrawing. Compounds with stronger molecular dipoles, in which dipolar interactions stabilize assemblies by 10-15 kJ·mol-1, were found to form crystalline nanoribbons in solution. In contrast, when the molecular dipole moment is small, nanofibers were obtained. Highly blue-shifted absorption maxima were observed in assemblies with large dipoles, indicating strong electronic coupling is present. However, only the moderate dipole compound had the appropriate molecular packing to access charge-transfer excitons leading to enhanced photocatalytic H2 production.
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Affiliation(s)
- Adam S. Weingarten
- Department of Chemistry, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
| | - Adam J. Dannenhoffer
- Department of Materials Science and Engineering, Northwestern University, 2220 Campus Dr, Evanston, IL 60208, USA
| | - Roman V. Kazantsev
- Department of Chemistry, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
| | - Hiroaki Sai
- Simpson Querrey Institute for Bionanotechnology, Northwestern University, 303 E. Superior St, Chicago, Illinois 60611, USA
| | - Dongxu Huang
- Department of Materials Science and Engineering, Northwestern University, 2220 Campus Dr, Evanston, IL 60208, USA
| | - Samuel I. Stupp
- Department of Chemistry, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA
- Department of Materials Science and Engineering, Northwestern University, 2220 Campus Dr, Evanston, IL 60208, USA
- Simpson Querrey Institute for Bionanotechnology, Northwestern University, 303 E. Superior St, Chicago, Illinois 60611, USA
- Department of Medicine, Northwestern University, 251 E. Huron St, Chicago, Illinois 60611, USA
- Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Rd, Evanston, Illinois 60208, USA
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Kazantsev RV, Dannenhoffer AJ, Weingarten AS, Phelan BT, Harutyunyan B, Aytun T, Narayanan A, Fairfield DJ, Boekhoven J, Sai H, Senesi A, O'Dogherty PI, Palmer LC, Bedzyk MJ, Wasielewski MR, Stupp SI. Crystal-Phase Transitions and Photocatalysis in Supramolecular Scaffolds. J Am Chem Soc 2017; 139:6120-6127. [PMID: 28436654 PMCID: PMC5556754 DOI: 10.1021/jacs.6b13156] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
![]()
The
energy landscape of a supramolecular material can include different
molecular packing configurations that differ in stability and function.
We report here on a thermally driven crystalline order transition
in the landscape of supramolecular nanostructures formed by charged
chromophore amphiphiles in salt-containing aqueous solutions. An irreversible
transition was observed from a metastable to a stable crystal phase
within the nanostructures. In the stable crystalline phase, the molecules
end up organized in a short scroll morphology at high ionic strengths
and as long helical ribbons at lower salt content. This is interpreted
as the result of the competition between electrostatic repulsive forces
and attractive molecular interactions. Only the stable phase forms
charge-transfer excitons upon exposure to visible light as indicated
by absorbance and fluorescence features, second-order harmonic generation
microscopy, and femtosecond transient absorbance spectroscopy. Interestingly,
the supramolecular reconfiguration to the stable crystalline phase
nanostructures enhances photosensitization of a proton reduction catalyst
for hydrogen production.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Andrew Senesi
- X-ray Science Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
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Hestand NJ, Kazantsev RV, Weingarten AS, Palmer LC, Stupp SI, Spano FC. Extended-Charge-Transfer Excitons in Crystalline Supramolecular Photocatalytic Scaffolds. J Am Chem Soc 2016; 138:11762-74. [DOI: 10.1021/jacs.6b05673] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Nicholas J. Hestand
- Department
of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
| | | | | | | | | | - Frank C. Spano
- Department
of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States
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Weingarten AS, Kazantsev RV, Palmer LC, Fairfield DJ, Koltonow AR, Stupp SI. Supramolecular Packing Controls H₂ Photocatalysis in Chromophore Amphiphile Hydrogels. J Am Chem Soc 2015; 137:15241-6. [PMID: 26593389 PMCID: PMC4676032 DOI: 10.1021/jacs.5b10027] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
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Light harvesting supramolecular assemblies
are potentially useful
structures as components of solar-to-fuel conversion materials. The
development of these functional constructs requires an understanding
of optimal packing modes for chromophores. We investigated here assembly
in water and the photocatalytic function of perylene monoimide chromophore
amphiphiles with different alkyl linker lengths separating their hydrophobic
core and the hydrophilic carboxylate headgroup. We found that these
chromophore amphiphiles (CAs) self-assemble into charged nanostructures
of increasing aspect ratio as the linker length is increased. The
addition of salt to screen the charged nanostructures induced the
formation of hydrogels and led to internal crystallization within
some of the nanostructures. For linker lengths up to seven methylenes,
the CAs were found to pack into 2D crystalline unit cells within ribbon-shaped
nanostructures, whereas the nine methylene CAs assembled into long
nanofibers without crystalline molecular packing. At the same time,
the different molecular packing arrangements after charge screening
led to different absorbance spectra, despite the identical electronic
properties of all PMI amphiphiles. While the crystalline CAs formed
electronically coupled H-aggregates, only CAs with intermediate linker
lengths showed evidence of high intermolecular orbital overlap. Photocatalytic
hydrogen production using a nickel-based catalyst was observed in
all hydrogels, with the highest turnovers observed for CA gels having
intermediate linker lengths. We conclude that the improved photocatalytic
performance of the hydrogels formed by supramolecular assemblies of
the intermediate linker CA molecules likely arises from improved exciton
splitting efficiencies due to their higher orbital overlap.
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Affiliation(s)
- Adam S Weingarten
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.,Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , Evanston, Illinois 60208, United States
| | - Roman V Kazantsev
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.,Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , Evanston, Illinois 60208, United States
| | - Liam C Palmer
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.,Simpson Querrey Institute for BioNanotechnology, Northwestern University , Chicago, Illinois 60611, United States
| | - Daniel J Fairfield
- Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Andrew R Koltonow
- Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States
| | - Samuel I Stupp
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.,Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University , Evanston, Illinois 60208, United States.,Simpson Querrey Institute for BioNanotechnology, Northwestern University , Chicago, Illinois 60611, United States.,Department of Materials Science and Engineering, Northwestern University , Evanston, Illinois 60208, United States.,Department of Medicine, Northwestern University , Chicago, Illinois 60611, United States.,Department of Biomedical Engineering, Northwestern University , Evanston, Illinois 60208, United States
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