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Unsymmetrical Bis-Alkynyl Complexes Based on Co(III)(cyclam): Synthesis, Ultrafast Charge Separation, and Analysis.

Publication ,  Journal Article
Banziger, SD; Li, X; Valdiviezo, J; Zeller, M; Zhang, P; Beratan, DN; Rubtsov, IV; Ren, T
Published in: Inorganic chemistry
November 2019

Donor-bridge-acceptor (D-B-A) systems with a polarizable bridge can afford rapid photoinduced electron transfer dynamics that may be susceptible to rate modulation by infrared excitation. We describe the synthesis, characterization, and electronic structure of a class of readily assembled D-B-A structures linked by a cobalt cyclam bridge. The reaction between [Co(cyclam)Cl2]Cl and 4-ethynyl-N-isopropyl-1,8-naphthalimide (HC2NAPiPr) yields [Co(cyclam)(C2NAPiPr)Cl]Cl (1), which reacts with LiC2Y at -78 °C to afford [Co(cyclam)(C2NAPiPr)(C2D)]Cl with D as C6H4-4-NMe2 (2a), NAPiPr (2b), Ph (2c), and C6H4-4-N(4-MeOPh)2 (2d). Molecular structures of 1 and 2a were established using single-crystal X-ray diffraction, while the redox properties and fluorescence profiles of compounds 1 and 2 were examined using voltammetric and steady-state emission techniques, respectively. The electronic structures and photophysical properties of these compounds were studied using density functional theory and time-dependent density functional theory methods. The excited-state dynamics of compounds 1, 2a, and 2d were explored using femtosecond transient absorption spectroscopy with 400 nm excitation and detection in both the visible and mid-IR spectral regions. Formation of a long-lived excited state was complete within 20 ps of excitation in all three compounds. Ultrafast spectral changes observed in 2a and 2d within the first 20 ps indicated the formation of a charge separated state (CS state, D+-B-A-) with characteristic times of less than 0.1 and 0.25 ps, respectively. The CS state undergoes rapid charge recombination (8 ps in 2a and 4 ps in 2d). The CS dynamics is facilitated by the Co center, which mixes the bright NAP-centered electronic state with a pure CS state. The mixing strength depends on the donor energetics and conformation, which significantly influences the charge transfer dynamics in 2a and 2d.

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Published In

Inorganic chemistry

DOI

EISSN

1520-510X

ISSN

0020-1669

Publication Date

November 2019

Volume

58

Issue

22

Start / End Page

15487 / 15497

Related Subject Headings

  • Inorganic & Nuclear Chemistry
  • 3403 Macromolecular and materials chemistry
  • 3402 Inorganic chemistry
  • 0399 Other Chemical Sciences
  • 0306 Physical Chemistry (incl. Structural)
  • 0302 Inorganic Chemistry
 

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Banziger, S. D., Li, X., Valdiviezo, J., Zeller, M., Zhang, P., Beratan, D. N., … Ren, T. (2019). Unsymmetrical Bis-Alkynyl Complexes Based on Co(III)(cyclam): Synthesis, Ultrafast Charge Separation, and Analysis. Inorganic Chemistry, 58(22), 15487–15497. https://doi.org/10.1021/acs.inorgchem.9b02557
Banziger, Susannah D., Xiao Li, Jesús Valdiviezo, Matthias Zeller, Peng Zhang, David N. Beratan, Igor V. Rubtsov, and Tong Ren. “Unsymmetrical Bis-Alkynyl Complexes Based on Co(III)(cyclam): Synthesis, Ultrafast Charge Separation, and Analysis.Inorganic Chemistry 58, no. 22 (November 2019): 15487–97. https://doi.org/10.1021/acs.inorgchem.9b02557.
Banziger SD, Li X, Valdiviezo J, Zeller M, Zhang P, Beratan DN, et al. Unsymmetrical Bis-Alkynyl Complexes Based on Co(III)(cyclam): Synthesis, Ultrafast Charge Separation, and Analysis. Inorganic chemistry. 2019 Nov;58(22):15487–97.
Banziger, Susannah D., et al. “Unsymmetrical Bis-Alkynyl Complexes Based on Co(III)(cyclam): Synthesis, Ultrafast Charge Separation, and Analysis.Inorganic Chemistry, vol. 58, no. 22, Nov. 2019, pp. 15487–97. Epmc, doi:10.1021/acs.inorgchem.9b02557.
Banziger SD, Li X, Valdiviezo J, Zeller M, Zhang P, Beratan DN, Rubtsov IV, Ren T. Unsymmetrical Bis-Alkynyl Complexes Based on Co(III)(cyclam): Synthesis, Ultrafast Charge Separation, and Analysis. Inorganic chemistry. 2019 Nov;58(22):15487–15497.
Journal cover image

Published In

Inorganic chemistry

DOI

EISSN

1520-510X

ISSN

0020-1669

Publication Date

November 2019

Volume

58

Issue

22

Start / End Page

15487 / 15497

Related Subject Headings

  • Inorganic & Nuclear Chemistry
  • 3403 Macromolecular and materials chemistry
  • 3402 Inorganic chemistry
  • 0399 Other Chemical Sciences
  • 0306 Physical Chemistry (incl. Structural)
  • 0302 Inorganic Chemistry