Fluorescence of 4-Cyanophenylhydrazones: From Molecular Design to Electrospun Polymer Fibers
Abstract
1. Introduction
2. Results and Discussion
2.1. Crystal Structure Analysis
2.2. Analysis of Absorption Properties of Phenylhydrazones
2.3. Analysis of Fluorescent Properties of Phenylhydrazones
2.4. Modulation of Hydrazone Properties in Electrospun Polymer Matrices
2.4.1. Morphological Analysis and Structural Stability
2.4.2. Photophysical Properties and Dye–Polymer Interactions
2.4.3. Influence of Dye Concentration on Quantum Yield in the PVP Matrix
2.4.4. Thermal Stability of Fluorescence Properties
3. Materials and Methods
3.1. Synthesis of Phenylhydrazones
3.2. Preparation of Electrospinning Solutions
3.3. Electrospinning Process
3.4. Instrumental Studies
3.4.1. Single-Crystal X-Ray Diffraction (SC-XRD) Studies
3.4.2. FTIR and ATR Spectroscopy
3.4.3. NMR
3.4.4. DSC
- Results of FTIR, NMR and DSC measurements:
3.4.5. UV-VIS Spectroscopy
3.4.6. Fluorescence Spectroscopy
- Excitation and Emission Spectra: High-resolution excitation spectra were recorded over a focused range (250–450 nm) while monitoring the emission at the respective maxima identified in the initial screening (464 nm for H3 and 485 nm for H13 systems). Correspondingly, detailed emission spectra were recorded upon excitation at several distinct wavelengths (280 nm, 320 nm, 380 nm) to verify the principle of excitation-emission independence within the polymer host.
- Quantum Yield of Doped Matrices: The absolute quantum yields of the dye-doped mats were also determined using the FS5 instrument’s integrating sphere. The excitation wavelengths were specifically selected to match the absorption maxima of the hydrazones once embedded within the polymer matrix (415 nm for H3-doped matrices and 405 nm for H13-doped matrices), which can differ slightly from the pure powder form.
- Temperature-Dependent Studies: The thermal stability of the polymer mats was assessed using a temperature-controlled reflectance setup integrated with the FS5 spectrometer. For the analysis, the sample was positioned on a heating plate equipped with an adjacent thermocouple to monitor the surface temperature. A 460 nm LED was employed as a stable excitation source, and emission was recorded at 25 °C, 50 °C, and 100 °C. Each measurement was taken at the moment the thermocouple confirmed that the setpoint temperature had been reached.
3.4.7. Scanning Electron Microscopy (SEM)
3.5. Computational Methods
4. Conclusions
Supplementary Materials
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Compound | H-Bond Motifs or NH···π (Ring) Interactions | π···π Ring-Stacking Motifs (System) | π···π Stacking Between Hydrazone Moiety and Ring (System) | π···π Stacking Between Cyano group and Ring |
---|---|---|---|---|
H1 | NH···NC, L1C(8) | – | hm···R2 (dimers) | CN···R2 |
H2 | NH···NC, L1C(8) | – | – | CN···R2 |
H3 | NH···R2 | – | – | – |
H4 | NH···NC, L2C22(16)[C(8)] | HT1 and HT2 (columnar) * | – | – |
H5 | NH···N, L1C(3) OH···NC, L1C(15) | HT2 (dimers) | – | – |
H6 | NH···NC, L1C(8) | HH2 (columnar) | – | – |
H7 | NH···NC, L1C(8) NH···ON, L1C(10) | – | hm···PhCN (columnar) | CN···PhCN |
H8 | NH···NC, L4C44(32)[C(8)] | – | – | CN···PhCN |
H9 | NH···NC, L1C(8) | HH1 (columnar) | – | – |
H10 | NH···NC, L1C(8) | HH2 (columnar) | – | – |
H11 | NH···NC, L1C(8) NH···ON, L1R22(9) | HT2 (columnar) | – | – |
H12 | NH···NC, L1C(8) | HH2 (columnar) | – | – |
H13 | NH···NC, L1C(8) | – | hm···R2 (dimers) | – |
H14 | NH···NC, L1C(8) | HT2 (dimers) | – | – |
Compound | λex (nm) | λem (nm) | Int | H → L Transition | Orbital Transition | Φf | τ (ns) |
---|---|---|---|---|---|---|---|
H1 | 343 | 440 | 252 | H-1 → L + 3 H → L + 4 | π → π* | 0.23 | 0.94 |
419 | 440 | 436 | H → L + 2 | π → π* | 0.11 | ||
H2 | 338 | 425 | 227 | H-1 → L + 2 | π → π* | 0.25 | 0.72 |
407 | 425 | 407 | H-1 → L | π → π* (LLCT) | 0.20 | ||
H3 | 362 | 462 | 249 | H-1 → L + 6 | π → π* (LLCT) | 0.22 | 12.50 |
438 | 462 | 359 | H-1 → L | π → π* (LLCT) | 0.10 | ||
H4 | 372 | 434 | 17 | H-2 → L + 2 H-3 → L | π → π* | 0.02 | 0.45 |
H5 | 367 | 433 | 16 | H → L + 4 | π → π* | 0.03 | <0.2 # |
H6 | 357 | 463 | 101 | H-3 → L | π → π* (LLCT) | 0.07 | 1.18 |
434 | 463 | 171 | H-2 → L | π → π* (LLCT) | 0.04 | ||
H8 | 344 | 446 | 121 | H → L + 2 H-2 → L | π → π* | 0.05 | 0.58 |
425 | 446 | 244 | H → L | π → π* (LLCT) | 0.03 | ||
H12 | 366 | 421 | 43 | H-1 → L + 2 | π → π* | 0.02 | 1.33 |
H13 | 351 | 494 | 135 | H-1 → L + 3 H-3 → L + 1 H-2 → L | π → π* | 0.40 | 5.14 |
439 | 494 | 296 | H → L + 1 | π → π* | 0.22 |
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Sobczak-Tyluś, P.; Sierański, T.; Świątkowski, M.; Trzęsowska-Kruszyńska, A.; Bogucki, O. Fluorescence of 4-Cyanophenylhydrazones: From Molecular Design to Electrospun Polymer Fibers. Molecules 2025, 30, 3638. https://doi.org/10.3390/molecules30173638
Sobczak-Tyluś P, Sierański T, Świątkowski M, Trzęsowska-Kruszyńska A, Bogucki O. Fluorescence of 4-Cyanophenylhydrazones: From Molecular Design to Electrospun Polymer Fibers. Molecules. 2025; 30(17):3638. https://doi.org/10.3390/molecules30173638
Chicago/Turabian StyleSobczak-Tyluś, Paulina, Tomasz Sierański, Marcin Świątkowski, Agata Trzęsowska-Kruszyńska, and Oskar Bogucki. 2025. "Fluorescence of 4-Cyanophenylhydrazones: From Molecular Design to Electrospun Polymer Fibers" Molecules 30, no. 17: 3638. https://doi.org/10.3390/molecules30173638
APA StyleSobczak-Tyluś, P., Sierański, T., Świątkowski, M., Trzęsowska-Kruszyńska, A., & Bogucki, O. (2025). Fluorescence of 4-Cyanophenylhydrazones: From Molecular Design to Electrospun Polymer Fibers. Molecules, 30(17), 3638. https://doi.org/10.3390/molecules30173638