Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

Natascha Breuer,
Irina Gruber,
Christoph Janiak and
Thomas J. J. Müller

Full Research Paper
Published 12 Nov 2019

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1. Graphical Abstract
2. Scheme 1: Consecutive three-component alkynylation–Michael addition–cyclocondensation (AMAC) synthesis of α-p...
  
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3. Scheme 2: Consecutive pseudo-four-component alkynylation–Michael addition–cyclocondensation (AMAC) synthesis ...
  
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4. Scheme 3: Consecutive pseudo-four-component alkynylation–Michael addition–cyclocondensation (AMAC) synthesis ...
  
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5. Scheme 4: Model system for the optimization of the Michael addition–cyclocondensation reaction step to 1H-pyr...
  
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6. Scheme 5: Formation of α-pyrone 6a and 1H-pyridine 5a at 20 °C.
  
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7. Scheme 6: Formation of α-pyrone 6a starting from alkynone 3b having an electron-donating substituent.
  
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8. Scheme 7: Formation of 1H-pyridine 5b starting from alkynone 3d having an electron-withdrawing substituent.
  
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9. Scheme 8: Formation of 1H-pyridine 8a by Michael addition–cyclocondensation reaction.
  
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10. Scheme 9: Mechanistic rationale for the formation of the 1H-pyridine 5a.
  
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11. Scheme 10: Formation of 1H-pyridine 8a from alkynone 3b and dimer 7.
  
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12. Figure 1: Molecular structure of 1H-pyridine 5a (50% thermal ellipsoids), showing the intramolecular N–H···O ...
  
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13. Figure 2: Supramolecular C–H···N [36-39] and C–H···π [40-49] interactions around the 6-positioned phenyl ring in 5a. Detail...
  
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14. Figure 3: 1H-Pyridine derivatives 5 as solids under daylight (top), under UV light (λ_exc = 365 nm, c(5) = 10⁻⁴...
  
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15. Figure 4: Selected normalized absorption (solid lines) and emission (dashed lines) spectra of 1H-pyridines 5a...
  
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16. Figure 5: Selected normalized emission spectra of 1H-pyridine 5a and 5b in the solid state at T = 298 K.
  
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17. Figure 6: Selected normalized absorption (solid lines) and emission (dashed lines) spectra of 1H-pyridines 8a...
  
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18. Figure 7: Solid-state luminescence of 1H-pyridines 5a, 8a and 8b (λ_exc = 365 nm).
  
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19. Figure 8: α-Pyrones 6 as solids under daylight (top), selected derivatives under UV light (λ_exc = 365 nm, c(6...
  
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20. Figure 9: Selected normalized absorption spectra of α-pyrones 6a, 6b, 6d, and 6e recorded in dichloromethane ...
  
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21. Figure 10: Selected normalized absorption (solid lines) and emission (dashed lines) spectra of α-pyrones 6c, 6e...
  
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22. Figure 11: Absorption (top) and fluorescence (bottom) of compound 6c with variable solvent polarity (left to t...
  
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23. Figure 12: Absorption (solid lines) and emission (dashed lines) spectra of α-pyrone 6c in five solvents of dif...
  
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24. Figure 13: Lippert plot for α-pyrone 6c (n = x, r² = 0.970).
  
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25. Figure 14: Normalized emission spectra of selected α-pyrones 6a–d,f in the solid state at T = 298 K.
  
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26. Figure 15: Fluorescence of compound 6e in different THF/water fractions (top, λ_exc = 365 nm, handheld UV lamp)...
  
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27. Figure 16: Selected DFT-computed (B3LYP 6-311G**) Kohn–Sham FMOs for 1H-pyridines 5f and 5g representing contr...
  
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28. Figure 17: Selected DFT-computed (B3LYP 6-311G**) Kohn–Sham FMOs for 1H-pyridines 6a, 6c, 6e, 6f, and 6g and r...
  
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