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Thompson NB, Mulfort KL, Tiede DM. Toward a quantitative description of solvation structure: a framework for differential solution scattering measurements. IUCRJ 2024; 11:423-433. [PMID: 38700232 PMCID: PMC11067739 DOI: 10.1107/s2052252524003282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Accepted: 04/15/2024] [Indexed: 05/05/2024]
Abstract
Appreciating that the role of the solute-solvent and other outer-sphere interactions is essential for understanding chemistry and chemical dynamics in solution, experimental approaches are needed to address the structural consequences of these interactions, complementing condensed-matter simulations and coarse-grained theories. High-energy X-ray scattering (HEXS) combined with pair distribution function analysis presents the opportunity to probe these structures directly and to develop quantitative, atomistic models of molecular systems in situ in the solution phase. However, at concentrations relevant to solution-phase chemistry, the total scattering signal is dominated by the bulk solvent, prompting researchers to adopt a differential approach to eliminate this unwanted background. Though similar approaches are well established in quantitative structural studies of macromolecules in solution by small- and wide-angle X-ray scattering (SAXS/WAXS), analogous studies in the HEXS regime-where sub-ångström spatial resolution is achieved-remain underdeveloped, in part due to the lack of a rigorous theoretical description of the experiment. To address this, herein we develop a framework for differential solution scattering experiments conducted at high energies, which includes concepts of the solvent-excluded volume introduced to describe SAXS/WAXS data, as well as concepts from the time-resolved X-ray scattering community. Our theory is supported by numerical simulations and experiment and paves the way for establishing quantitative methods to determine the atomic structures of small molecules in solution with resolution approaching that of crystallography.
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Affiliation(s)
- Niklas B. Thompson
- Division of Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439 USA
| | - Karen L. Mulfort
- Division of Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439 USA
| | - David M. Tiede
- Division of Chemical Sciences and Engineering, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439 USA
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2
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Ryland ES, Liu X, Kumar G, Raj SL, Xie ZL, Mengele AK, Fauth SS, Siewerth K, Dietzek-Ivanšić B, Rau S, Mulfort KL, Li X, Cordones AA. Site-specific electronic structure of covalently linked bimetallic dyads from nitrogen K-edge x-ray absorption spectroscopy. J Chem Phys 2024; 160:084307. [PMID: 38415835 DOI: 10.1063/5.0192809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 01/15/2024] [Indexed: 02/29/2024] Open
Abstract
A nitrogen K-edge x-ray absorption near-edge structure (XANES) survey is presented for tetrapyrido[3,2-a:2',3'-c:3″,2″-h:2‴,3‴-j]phenazine (tpphz)-bridged bimetallic assemblies that couple chromophore and catalyst transition metal complexes for light driven catalysis, as well as their individual molecular constituents. We demonstrate the high N site sensitivity of the N pre-edge XANES features, which are energetically well-separated for the phenazine bridge N atoms and for the individual metal-bound N atoms of the inner coordination sphere ligands. By comparison with the time-dependent density functional theory calculated spectra, we determine the origins of these distinguishable spectral features. We find that metal coordination generates large shifts toward higher energy for the metal-bound N atoms, with increasing shift for 3d < 4d < 5d metal bonding. This is attributed to increasing ligand-to-metal σ donation that increases the effective charge of the bound N atoms and stabilizes the N 1s core electrons. In contrast, the phenazine bridge N pre-edge peak is found at a lower energy due to stabilization of the low energy electron accepting orbital localized on the phenazine motif. While no sensitivity to ground state electronic coupling between the individual molecular subunits was observed, the spectra are sensitive to structural distortions of the tpphz bridge. These results demonstrate N K-edge XANES as a local probe of electronic structure in large bridging ligand motifs, able to distinctly investigate the ligand-centered orbitals involved in metal-to-ligand and ligand-to-ligand electron transfer following light absorption.
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Affiliation(s)
- Elizabeth S Ryland
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Xiaolin Liu
- University of Washington, Seattle, Washington 98195, USA
| | - Gaurav Kumar
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Sumana L Raj
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Zhu-Lin Xie
- Division of Chemical Sciences and Engineering, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Alexander K Mengele
- Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Sven S Fauth
- Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Kevin Siewerth
- Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Benjamin Dietzek-Ivanšić
- Leibniz Institute of Photonic Technology, Research Department Functional Interfaces, Albert-Einstein Straße 9, 07745 Jena, Germany and Friedrich Schiller University Jena, Institute of Physical Chemistry, Helmholtzweg 4, 07743 Jena, Germany
| | - Sven Rau
- Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Karen L Mulfort
- Division of Chemical Sciences and Engineering, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Xiaosong Li
- University of Washington, Seattle, Washington 98195, USA
| | - Amy A Cordones
- Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
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Rosko MC, Wheeler JP, Alameh R, Faulkner AP, Durand N, Castellano FN. Enhanced Visible Light Absorption in Heteroleptic Cuprous Phenanthrolines. Inorg Chem 2024; 63:1692-1701. [PMID: 38190287 DOI: 10.1021/acs.inorgchem.3c04024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
This work presents a series of Cu(I) heteroleptic 1,10-phenanthroline chromophores featuring enhanced UVA and visible-light-harvesting properties manifested through vectorial control of the copper-to-phenanthroline charge-transfer transitions. The molecules were prepared using the HETPHEN strategy, wherein a sterically congested 2,9-dimesityl-1,10-phenanthrolne (mesPhen) ligand was paired with a second phenanthroline ligand incorporating extended π-systems in their 4,7-positions. The combination of electrochemistry, static and time-resolved electronic spectroscopy, 77 K photoluminescence spectra, and time-dependent density functional theory calculations corroborated all of the experimental findings. The model chromophore, [Cu(mesPhen)(phen)]+ (1), lacking 4,7-substitutions preferentially reduces the mesPhen ligand in the lowest energy metal-to-ligand charge-transfer (MLCT) excited state. The remaining cuprous phenanthrolines (2-4) preferentially reduce their π-conjugated ligands in the low-lying MLCT excited state. The absorption cross sections of 2-4 were enhanced (εMLCTmax = 7430-9980 M-1 cm-1) and significantly broadened across the UVA and visible regions of the spectrum compared to 1 (εMLCTmax = 6494 M-1 cm-1). The excited-state decay mechanism mirrored those of long-lived homoleptic Cu(I) phenanthrolines, yielding three distinguishable time constants in ultrafast transient absorption experiments. These represent pseudo-Jahn-Teller distortion (τ1), singlet-triplet intersystem crossing (τ2), and the relaxed MLCT excited-state lifetime (τ3). Effective light-harvesting from Cu(I)-based chromophores can now be rationalized within the HETPHEN strategy while achieving directionality in their respective MLCT transitions, valuable for integration into more complex donor-acceptor architectures and longer-lived photosensitizers.
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Affiliation(s)
- Michael C Rosko
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Jonathan P Wheeler
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Reem Alameh
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Adrienne P Faulkner
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Nicolas Durand
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Felix N Castellano
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
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Xie ZL, Gupta N, Niklas J, Poluektov OG, Lynch VM, Glusac KD, Mulfort KL. Photochemical charge accumulation in a heteroleptic copper(i)-anthraquinone molecular dyad via proton-coupled electron transfer. Chem Sci 2023; 14:10219-10235. [PMID: 37772110 PMCID: PMC10529959 DOI: 10.1039/d3sc03428c] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 08/30/2023] [Indexed: 09/30/2023] Open
Abstract
Developing efficient photocatalysts that perform multi electron redox reactions is critical to achieving solar energy conversion. One can reach this goal by developing systems which mimic natural photosynthesis and exploit strategies such as proton-coupled electron transfer (PCET) to achieve photochemical charge accumulation. We report herein a heteroleptic Cu(i)bis(phenanthroline) complex, Cu-AnQ, featuring a fused phenazine-anthraquinone moiety that photochemically accumulates two electrons in the anthraquinone unit via PCET. Full spectroscopic and electrochemical analyses allowed us to identify the reduced species and revealed that up to three electrons can be accumulated in the phenazine-anthraquinone ring system under electrochemical conditions. Continuous photolysis of Cu-AnQ in the presence of sacrificial electron donor produced doubly reduced monoprotonated photoproduct confirmed unambiguously by X-ray crystallography. Formation of this photoproduct indicates that a PCET process occurred during illumination and two electrons were accumulated in the system. The role of the heteroleptic Cu(i)bis(phenanthroline) moiety participating in the photochemical charge accumulation as a light absorber was evidenced by comparing the photolysis of Cu-AnQ and the free AnQ ligand with less reductive triethylamine as a sacrificial electron donor, in which photogenerated doubly reduced species was observed with Cu-AnQ, but not with the free ligand. The thermodynamic properties of Cu-AnQ were examined by DFT which mapped the probable reaction pathway for photochemical charge accumulation and the capacity for solar energy stored in the process. This study presents a unique system built on earth-abundant transition metal complex to store electrons, and tune the storage of solar energy by the degree of protonation of the electron acceptor.
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Affiliation(s)
- Zhu-Lin Xie
- Division of Chemical Sciences and Engineering, Argonne National Laboratory USA
| | - Nikita Gupta
- Division of Chemical Sciences and Engineering, Argonne National Laboratory USA
- Department of Chemistry, University of Illinois at Chicago USA
| | - Jens Niklas
- Division of Chemical Sciences and Engineering, Argonne National Laboratory USA
| | - Oleg G Poluektov
- Division of Chemical Sciences and Engineering, Argonne National Laboratory USA
| | | | - Ksenija D Glusac
- Division of Chemical Sciences and Engineering, Argonne National Laboratory USA
- Department of Chemistry, University of Illinois at Chicago USA
| | - Karen L Mulfort
- Division of Chemical Sciences and Engineering, Argonne National Laboratory USA
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5
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Wang L, Xie ZL, Li X, Lynch VM, Mulfort KL. Optical detection of alcohols with a Cu(I)HETPHEN complex by reversible aldehyde to hemiacetal conversion. Analyst 2023; 148:4274-4278. [PMID: 37615298 DOI: 10.1039/d3an01005h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/25/2023]
Abstract
A heteroleptic copper(I) bis(phenanthroline) complex with aldehyde groups at the 4,7 positions of the phenanthroline ligand was synthesized. The complex is responsive to alcohol, resulting in a distinct colour change caused by the facile reaction of the aldehyde group with alcohol, forming a hemiacetal product. The aldehyde species can be regenerated after heating the intermediate at 80 °C for 10 minutes, demonstrating the reusability of the complex for alcohol detection. This work presents a new strategy for applying transition metal complexes in small molecule sensing by installing functional groups in the secondary coordination sphere which reversibly react with analytes.
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Affiliation(s)
- Lei Wang
- School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai 200093, China.
- Division of Chemical Sciences and Engineering, Argonne National Laboratory, Lemont, IL 60439, USA.
| | - Zhu-Lin Xie
- Division of Chemical Sciences and Engineering, Argonne National Laboratory, Lemont, IL 60439, USA.
| | - Xin Li
- School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai 200093, China.
| | - Vincent M Lynch
- Department of Chemistry, University of Texas Austin, Austin, TX, 78712, USA
| | - Karen L Mulfort
- Division of Chemical Sciences and Engineering, Argonne National Laboratory, Lemont, IL 60439, USA.
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