A comparative study of nine berberine salts in the solid state: optimization of the photoluminescence and self-association properties through the choice of the anion

Abstract

The arrangement of an ionic fluorophore in the crystalline state was regulated by the presence of various counter-ions and the effect on spectroscopic and self-association properties was studied. To do so, nine salts of berberine (i.e. a fluorescent natural alkaloid) were investigated. Most of them contained organic anions and were prepared using an ion-exchange process. Berberine chloride and hemisulfate were also used for the sake of comparison. The diffuse reflectance and photoluminescence spectra were recorded on powder compounds. All salts were emissive in the solid state and the emission efficiency was increased seven-fold with the nature of the anion. The optical properties were tentatively discussed on the basis of the crystal-packing mode. The possibility of implementing a bottom-up approach to generate microparticles was investigated using the reprecipitation method. Salts that contain the most hydrophobic anions gave a large number of homogeneous, elongated microparticles. This study showed that most of the berberine salts could be used as fluorescent materials, but proper choice of the anion allows using the self-association properties to best advantage.

Ionic aggregation-induced emission dye with bulky counterions for preparation of bright near-infrared polymeric nanoparticles

“…1A) by ionassociation. [79][80][81][82][83][84][85] For this, we mixed TPE-DPA-Py iodide (2 μM) with a 10-fold molar excess of the corresponding counterions in water. Dynamic light scattering (DLS) measurements showed that TPE-DPA-Py iodide in the presence of counterions forms relatively small particles ranging from ca.…”

“…Thus, both TPE-F5 and TPE-F12 exhibited typical AIE behaviour, in line with other AIEgens reported earlier. 43,78,82 Remarkably, the emission maximum of TPE-F5 and TPE-F12 in water reached NIR region ~700 nm. On the other hand, the AIE experiments using dye salts with smaller counterions (TPE-PF6 and TPE-ClO4) also showed AIE behaviour, and their fluorescence quantum yields at 80% water were even higher than those with bulky anions.…”

Plug-and-Play Optical Materials from Fluorescent Dyes and Macrocycles

“…Toward fluorescent materials, new approaches have employed the co-assembly of cationic dyes with large anions. [37][38][39] Most successful are the works of Reisch and Klymchenko that obtained very high brightnesses using a covalently modified cationic rhodamine dye that was also ion paired with bulky fluorinated anions to become lipophilic and then loaded into polymer nanoparticles. [40][41][42] Despite the ability to translate optical properties, under the appropriate conditions, most of the assemblies do not display the crystalline ordering expected from use of strong structure-directing units.…”

Crystallographic and Energetic Insights into Reduced Dissolution and Physical Stability of a Drug–Surfactant Salt: The Case of Norfloxacin Lauryl Sulfate

“…In this study, we provide more direct evidence of proton transfer between the drug cation and LS – anion through an analysis of crystal structure, from which molecular insights into the changes in pharmaceutical properties, such as solubility and dissolution rate, could be gained. Crystal structures of a handful of complexes between LS – and organic molecules have been reported, including berberine, 9-aminoacridine (a cationic dye), O- lauroylethanolamine, and quinolinium and isoquinolinium (ionic liquid crystals) . However, most reported drug–lauryl sulfate complexes are amorphous, except for trimethoprim and metformin, which precipitated out as crystalline solids. , Single-crystal structures of trimethoprim and metformin complexes with LS – have not been reported.…”