Research ArticleChemistry

A single-stranded coordination copolymer affords heterostructure observation and photoluminescence intensification

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Science Advances  02 Jan 2019:
Vol. 5, no. 1, eaau0637
DOI: 10.1126/sciadv.aau0637
  • Fig. 1 Bis(dipyrrinato)zinc(II) coordination polymers and mononuclear complexes.

    (A and B) Synthetic schemes and chemical structures of (A) homopolymers Homo-1 to Homo-3 and (B) copolymers Co-1-k and Co-2-k (k = 1 to 7). Chemical structures of constitutive bridging dipyrrin proligands (H2L1, H2L2, and H2L3) and bridging dipyrrin ligands (L1, L2, and L3) are also provided. (C) Moles of proligands H2L1 and H2L3 used to prepare Co-1-k are listed. r and x denote the mixing ratio of H2L1 to (H2L1 + H2L3) and actual mole fraction of L1 in Co-1-k, respectively. (D) Moles of proligands H2L2 and H2L3 used to prepare Co-2-k are listed. r′ and x′ denote the mixing ratio of H2L2 to (H2L2 + H2L3) and actual mole fraction of L2 in Co-2-k, respectively. (E) Chemical structures of mononuclear complexes Mono-1 to Mono-5. The heteroleptic complexes (Mono-4 and Mono-5) show brighter fluorescence than the homoleptic ones (Mono-1 to Mono-3).

  • Fig. 2 Exfoliation and UV/vis spectroscopy in toluene.

    (A) Exfoliation of the coordination polymer into single strands. (B and C) Photographs of a toluene dispersion of Co-1-3 upon illumination with laser flux: (B) red and (C) green. In (C), the green flux scattering is concealed with orange PL. (D) Normalized UV/vis spectra of bridging dipyrrin proligands H2L1 and H2L3 and homopolymers Homo-1 and Homo-3. a.u., arbitrary units. (E) UV/vis spectra of Co-1-k (k = 1 to 7) normalized at 490 nm. (F) Relationship between the actual mole fraction of L1 to (L1 + L3) in Co-1-k (x) and mixing ratio of H2L1 to (H2L1 + H2L3) (r).

  • Fig. 3 AFM analysis.

    (A) AFM height image of single strands of Co-1-3 appearing as white lines on a HOPG substrate. (B) Height histograms for individual single strands of Co-1-3. (C) Height histograms for all single strands of Co-1-3 (magenta), Homo-1 (orange shaded), and Homo-3′ (blue shaded). (D) Chemical structures of corresponding mononuclear complexes Mono-1 and Mono-3′, with sizes estimated by density functional theory (DFT) calculation. AFM images of (E) Co-1-1, (G) Co-1-2, (I) Co-1-5, and (K) Co-1-7. Height histograms for (F) Co-1-1, (H) Co-1-2, (J) Co-1-5, and (L) Co-1-7, along with those of Homo-1 (orange shaded) and Homo-3′ (blue shaded). (M) Gaussian-fitted height histograms for Co-1-k, Homo-1, and Homo-3′. (N) Plot of central value of Gaussian curve and actual mole fraction of L1 (x) for Co-1-k, Homo-1, and Homo-3′.

  • Fig. 4 PL spectroscopy in toluene.

    (A) PL spectra of Homo-1 (magenta) and Homo-3 (green) excited at 550 and 490 nm, respectively. (B to H) Co-1-k (k = 1 to 7) excited at 550 nm (circles) and 490 nm (solid lines). (I) UV/vis spectra of Homo-1 + Homo-3 (solid line) and Co-1-4 (dotted line) with normalization at 490 nm. (J) PL spectra of Homo-1 + Homo-3 (solid line) and Co-1-4 (dotted line) upon excitation with 490-nm light. (K) Illustration of exciton transfer behavior: interwire exciton transfer in Homo-1 + Homo-3 is negligible, whereas intrawire exciton transfer in Co-1-4 is efficient.

  • Fig. 5 PL quantum yield dependence on x in toluene.

    (A and B) ϕPL-x plots for coordination copolymers Co-1-k (k = 1 to 7, squares), homopolymers (Homo-1 and Homo-3, triangles), and additional copolymer samples (circles) excited at (A) 550 nm and (B) 490 nm.

  • Fig. 6 Numerical simulation for PL efficiency.

    (A) Four types of constituent dipyrrinato ligands in coordination copolymers Co-1-k, DHomo-L1, DHomo-L3, DHetero-L1, and DHetero-L3. (B) Possible intrawire exciton migration pathways considered in the numerical simulation. (C and D) Simulated ϕPL-x plot with various N when excited at (C) 550 nm and (D) 490 nm.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/1/eaau0637/DC1

    Fig. S1. Oak Ridge thermal ellipsoid plot drawings of H2L3·2HBr and H2L3′·2HBr·(solvent)n with a thermal ellipsoid set at the 50% probability level.

    Fig. S2. XPS for proligands and coordination polymers.

    Fig. S3. Quantification of the elemental ratio from XPS.

    Fig. S4. Elemental abundances in Co-1-k and Homo-1 determined by elemental and ICP-AES analysis.

    Fig. S5. PL enhancement mechanism for a heteroleptic complex.

    Fig. S6. UV/vis spectroscopy for Co-2-k in toluene.

    Fig. S7. Photovoltaic conversion of Co-1-6, Homo-3, and Homo-1.

    Fig. S8. Three-electrode electrochemical cell used for the photoelectric conversion.

    Fig. S9. AFM images of Co-1-3 on other substrates.

    Fig. S10. AFM for Homo-1.

    Fig. S11. AFM for Homo-3′.

    Fig. S12. Gaussian fitting of AFM height histograms of Co-1-k, Homo-1, and Homo-3′.

    Fig. S13. PL lifetimes (τPL) in toluene.

    Fig. S14. PL of Co-2-k in toluene.

    Fig. S15. PL quantum yield dependence on x′ in toluene.

    Fig. S16. Calculated ϕPL dependence on x.

    Fig. S17. UV/vis absorption spectroscopy for copolymers and corresponding mononuclear complexes in toluene.

    Table S1. Crystallographic data.

    Table S2. PL properties of Co-1-k, Homo-1, and Homo-3 in toluene.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Oak Ridge thermal ellipsoid plot drawings of H2L3·2HBr and H2L3′·2HBr·(solvent)n with a thermal ellipsoid set at the 50% probability level.
    • Fig. S2. XPS for proligands and coordination polymers.
    • Fig. S3. Quantification of the elemental ratio from XPS.
    • Fig. S4. Elemental abundances in Co-1-k and Homo-1 determined by elemental and ICP-AES analysis.
    • Fig. S5. PL enhancement mechanism for a heteroleptic complex.
    • Fig. S6. UV/vis spectroscopy for Co-2-k in toluene.
    • Fig. S7. Photovoltaic conversion of Co-1-6, Homo-3, and Homo-1.
    • Fig. S8. Three-electrode electrochemical cell used for the photoelectric conversion.
    • Fig. S9. AFM images of Co-1-3 on other substrates.
    • Fig. S10. AFM for Homo-1.
    • Fig. S11. AFM for Homo-3′.
    • Fig. S12. Gaussian fitting of AFM height histograms of Co-1-k, Homo-1, and Homo-3′.
    • Fig. S13. PL lifetimes (τPL) in toluene.
    • Fig. S14. PL of Co-2-k in toluene.
    • Fig. S15. PL quantum yield dependence on x′ in toluene.
    • Fig. S16. Calculated ϕPL dependence on x.
    • Fig. S17. UV/vis absorption spectroscopy for copolymers and corresponding mononuclear complexes in toluene.
    • Table S1. Crystallographic data.
    • Table S2. PL properties of Co-1-k, Homo-1, and Homo-3 in toluene.

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