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Figure 6. (A) Images of the change in fluorescence of 3aa upon grinding and fuming with DCM at 365 nm UV irradiation. (B) Normalized PL spectra of 3aa recorded before grinding, after grinding, and after fuming the sample in a mortar and pestle at room temperature (A,, = 375 nm). (C) XRD diffractograms of pristine, ground, and fumed 3aa samples. (D, E) FESEM images of luminogen 3aa taken (D) before and (E) after grinding the solid sample.

Figure 6 (A) Images of the change in fluorescence of 3aa upon grinding and fuming with DCM at 365 nm UV irradiation. (B) Normalized PL spectra of 3aa recorded before grinding, after grinding, and after fuming the sample in a mortar and pestle at room temperature (A,, = 375 nm). (C) XRD diffractograms of pristine, ground, and fumed 3aa samples. (D, E) FESEM images of luminogen 3aa taken (D) before and (E) after grinding the solid sample.

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‘Department of Chemistry and “Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, North Guwahati 781039, India
‘Department of Chemistry and “Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, North Guwahati 781039, India
"Reaction conditions: unless otherwise noted, all reactions were carried out with 1(a—o) (0.3 mmol), 2(a—h) (0.36 mmol), [RuCl,(p- cymene) |, (5 mol %), Cu(OAc),-H,O (0.66 mmol), TfOH (0.45 mmol), DCE (2.0 mL) in an air atmosphere at 120 °C for 10-14 h. "Isolated yield after column chromatography. “Isomeric ratio was determined by 'H NMR (see the Supporting Information).
"Reaction conditions: unless otherwise noted, all reactions were carried out with 1(a—o) (0.3 mmol), 2(a—h) (0.36 mmol), [RuCl,(p- cymene) |, (5 mol %), Cu(OAc),-H,O (0.66 mmol), TfOH (0.45 mmol), DCE (2.0 mL) in an air atmosphere at 120 °C for 10-14 h. "Isolated yield after column chromatography. “Isomeric ratio was determined by 'H NMR (see the Supporting Information).
Figure 1. (A) Optimized structure of 3aa. (B) Molecular orbital amplitude plots of HOMO and LUMO of 3aa using density functional theory calculation at the B3LYP/6-31G (d, p) basis set level in acetonitrile solvent modeled by the PCM approach. Theoretical Investigation. To gain insight into the geometry and electronic structure of the annulated quaternary ammonium salts, density functional theory (DFT) calculations were performed with a B3LYP/6-31G (d, p) basis set level in acetonitrile solvent modeled by the polarizable continuum model (PCM) approach (the Gaussian 09 program).*’ The density functional theory (DFT) calculation of 3aa reveals that the electron density in the highest occupied molecular orbital (HOMO) is localized at the two phenyl rings derived from diphenylacetylenes, whereas the lowest unoccupied molecular orbital (LUMO) is localized at the extended quinoxalium core (Figure 1). The optimized ground-state structure of 3aa
Figure 1. (A) Optimized structure of 3aa. (B) Molecular orbital amplitude plots of HOMO and LUMO of 3aa using density functional theory calculation at the B3LYP/6-31G (d, p) basis set level in acetonitrile solvent modeled by the PCM approach. Theoretical Investigation. To gain insight into the geometry and electronic structure of the annulated quaternary ammonium salts, density functional theory (DFT) calculations were performed with a B3LYP/6-31G (d, p) basis set level in acetonitrile solvent modeled by the polarizable continuum model (PCM) approach (the Gaussian 09 program).*’ The density functional theory (DFT) calculation of 3aa reveals that the electron density in the highest occupied molecular orbital (HOMO) is localized at the two phenyl rings derived from diphenylacetylenes, whereas the lowest unoccupied molecular orbital (LUMO) is localized at the extended quinoxalium core (Figure 1). The optimized ground-state structure of 3aa
The AEEgen concentration-dependent morphological inves- tigation confirmed the formation of nanocrystals at 60 “M (Figure 3A) and distorted nanospherical aggregates at 30 wM Figure 3. FESEM images of the morphology of the luminogen 3aa formed in (A) 99.2% f,, at a concentration of 60 4M and in (C) 99.6% fw at a concentration of 30 4M by a drop-casting technique applied on aluminum foil at room temperature. The insets are the magnified images of the corresponding morphology. (B) TEM image of crystalline 3aa aggregates formed in a DMF/water mixture with a 99.2% water fraction. Concentration: 60 #M. (D) TEM image of distorted spherical 3aa aggregates formed in a DMF/water mixture with a 99.6% water fraction. Concentration: 30 “M.
The AEEgen concentration-dependent morphological inves- tigation confirmed the formation of nanocrystals at 60 “M (Figure 3A) and distorted nanospherical aggregates at 30 wM Figure 3. FESEM images of the morphology of the luminogen 3aa formed in (A) 99.2% f,, at a concentration of 60 4M and in (C) 99.6% fw at a concentration of 30 4M by a drop-casting technique applied on aluminum foil at room temperature. The insets are the magnified images of the corresponding morphology. (B) TEM image of crystalline 3aa aggregates formed in a DMF/water mixture with a 99.2% water fraction. Concentration: 60 #M. (D) TEM image of distorted spherical 3aa aggregates formed in a DMF/water mixture with a 99.6% water fraction. Concentration: 30 “M.
Figure 4. (A) PL spectra of 3aa in MeOH/glycerol mixtures with different glycerol fractions (f,) with concentration = 15 pM, ,, = 375 nm, and slit = 2. (B) PL spectra of 3aa in DMF with concentration = 60 UM, A, = 375 nm, and slit = 2 nm. AEE Mechanism. The restriction in intramolecular motions including rotation and vibration is the main reason behind the turn-on fluorescence emission in any aggregated state. The single-crystal X-ray and DFT-optimized structure of AEEgen 3aa reveals that the two rotatable phenyl rings and the slightly bent propeller-shaped vibratable quinoxaline core are available for the nonradiative deactivation. To ascertain the existence of RIM in the aggregated state, two control experiments, namely, viscochromism and thermochromism, were carried out. In the viscochromism experiment, the photoluminescence (PL) measurement of 3aa was carried out at varying composition of 3-fold more viscous glycerol solvent (f, = 0, 30, 60, and 90%) in MeOH (Figure 4A). With varying percentage of glycerol, a
Figure 4. (A) PL spectra of 3aa in MeOH/glycerol mixtures with different glycerol fractions (f,) with concentration = 15 pM, ,, = 375 nm, and slit = 2. (B) PL spectra of 3aa in DMF with concentration = 60 UM, A, = 375 nm, and slit = 2 nm. AEE Mechanism. The restriction in intramolecular motions including rotation and vibration is the main reason behind the turn-on fluorescence emission in any aggregated state. The single-crystal X-ray and DFT-optimized structure of AEEgen 3aa reveals that the two rotatable phenyl rings and the slightly bent propeller-shaped vibratable quinoxaline core are available for the nonradiative deactivation. To ascertain the existence of RIM in the aggregated state, two control experiments, namely, viscochromism and thermochromism, were carried out. In the viscochromism experiment, the photoluminescence (PL) measurement of 3aa was carried out at varying composition of 3-fold more viscous glycerol solvent (f, = 0, 30, 60, and 90%) in MeOH (Figure 4A). With varying percentage of glycerol, a
Figure 5. (A) ORTEP diagram of 3aa along with the dihedral angles of the two phenyl rings to the quinoxaline plane as mentioned. Crystal packing « 3aa. (B) Various intramolecular H-bonding interactions shown in a ball-and-stick model, where distances are in A. (C) C—H---O and C-H-- rydrogen bonds with triflate ions with the C—H---N interactions also shown. (D, E) Multiple C—H---7 and weak z--- interactions between th nolecules. (F) Space-filling model of 3aa showing weak z---7 interactions.
Figure 5. (A) ORTEP diagram of 3aa along with the dihedral angles of the two phenyl rings to the quinoxaline plane as mentioned. Crystal packing « 3aa. (B) Various intramolecular H-bonding interactions shown in a ball-and-stick model, where distances are in A. (C) C—H---O and C-H-- rydrogen bonds with triflate ions with the C—H---N interactions also shown. (D, E) Multiple C—H---7 and weak z--- interactions between th nolecules. (F) Space-filling model of 3aa showing weak z---7 interactions.
over adhesive tape (Figure 7A), whereas 3ba furnished deep green LFPs (Figure 7B). Figure 7. High-resolution fluorescence images of latent fingerprints on adhesive tape developed with (A) 3ab and (B) 3ba, showing second- level investigation.
over adhesive tape (Figure 7A), whereas 3ba furnished deep green LFPs (Figure 7B). Figure 7. High-resolution fluorescence images of latent fingerprints on adhesive tape developed with (A) 3ab and (B) 3ba, showing second- level investigation.
The Z-stack analysis of the treated cells clearly indicates the uptake of these compounds into HeLa cells (Figure S27, Supporting Information). Similarly, Figure S28 (Supporting Information) shows the bright luminescence of HeLa cells after treatment with 3ja, 3ad, and 3fa. Shorter incubation time suggests their superior penetrability into the cell membrane. From CLSM images (Figure 9), it is apparent that the fluorescence signals are abundant in the cell cytoplasm and to a lower extent in the nucleus. Thus, it is evident that these compounds could be used as excellent luminescent probes for rapid staining of the cell cytoplasm. The staining ability of these compounds is mainly attributed to their positive charge as well as amphiphilic character. The positively charged species Effect on Cell Cycle. Flow cytometry-based analysis was performed to delineate the impact of compounds on the cell cycle of HeLa cells rendering growth inhibition. Treatment of HeLa cells with compounds 3ha, 3aa, and 3ea + 3’ea Figure 8. Effect of compounds 3ha, 3aa, 3ea + 3’ea, 3ja, 3ad, and 3fa in terms of reduction in the percentage of viable cells as demonstrated by the alamarBlue assay. Statistical significance has been determined by one-way ANOVA, with *p < 0.05; **p < 0.01; ***p < 0.001; and ****p < 0.0001.
The Z-stack analysis of the treated cells clearly indicates the uptake of these compounds into HeLa cells (Figure S27, Supporting Information). Similarly, Figure S28 (Supporting Information) shows the bright luminescence of HeLa cells after treatment with 3ja, 3ad, and 3fa. Shorter incubation time suggests their superior penetrability into the cell membrane. From CLSM images (Figure 9), it is apparent that the fluorescence signals are abundant in the cell cytoplasm and to a lower extent in the nucleus. Thus, it is evident that these compounds could be used as excellent luminescent probes for rapid staining of the cell cytoplasm. The staining ability of these compounds is mainly attributed to their positive charge as well as amphiphilic character. The positively charged species Effect on Cell Cycle. Flow cytometry-based analysis was performed to delineate the impact of compounds on the cell cycle of HeLa cells rendering growth inhibition. Treatment of HeLa cells with compounds 3ha, 3aa, and 3ea + 3’ea Figure 8. Effect of compounds 3ha, 3aa, 3ea + 3’ea, 3ja, 3ad, and 3fa in terms of reduction in the percentage of viable cells as demonstrated by the alamarBlue assay. Statistical significance has been determined by one-way ANOVA, with *p < 0.05; **p < 0.01; ***p < 0.001; and ****p < 0.0001.
Figure 9. Confocal laser scanning microscopy images of HeLa cells stained with (A) 3ha, (B) 3aa, and (C) 3ea + 3’ea. Cells were incubated with 145 wM AEEgens for 10 min. Excitation: 458 nm. Emission range: 480—605 nm. Scale bar: 20 pm.
Figure 9. Confocal laser scanning microscopy images of HeLa cells stained with (A) 3ha, (B) 3aa, and (C) 3ea + 3’ea. Cells were incubated with 145 wM AEEgens for 10 min. Excitation: 458 nm. Emission range: 480—605 nm. Scale bar: 20 pm.
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