curcumin and boron-difluoride

Topics: Amines; Benzene; Boron Compounds; Curcumin; Density Functional Theory; Electron Transport; Fluorescent Dyes; Kinetics; Models, Molecular; Molecular Structure; Structure-Activity Relationship

The synthesis of boron difluoride complexes of a series of curcuminoid derivatives containing various donor end groups is described. Time-dependent (TD)-DFT calculations confirm the charge-transfer character of the second lowest-energy transition band and ascribe the lowest energy band to a "cyanine-like" transition. Photophysical studies reveal that tuning the donor strength of the end groups allows covering a broad spectral range, from the visible to the NIR region, of the UV-visible absorption and fluorescence spectra. Two-photon-excited fluorescence and Z-scan techniques prove that an increase in the donor strength or in the rigidity of the backbone results in a considerable increase in the two-photon cross section, reaching 5000 GM, with predominant two-photon absorption from the S0-S2 charge-transfer transition. Direct comparisons with the hemicurcuminoid derivatives show that the two-photon active band for the curcuminoid derivatives has the same intramolecular charge-transfer character and therefore arises from a dipolar structure. Overall, this structure-relationship study allows the optimization of the two-photon brightness (i.e., 400-900 GM) with one dye that emits in the NIR region of the spectrum. In addition, these dyes demonstrate high intracellular uptake efficiency in Cos7 cells with emission in the visible region, which is further improved by using porous silica nanoparticles as dye vehicles for the imaging of two mammalian carcinoma cells type based on NIR fluorescence emission.

Topics: Animals; Boron Compounds; Curcumin; Fluorescence; Fluorescent Dyes; Ionophores; Molecular Structure; Photochemical Processes; Photons; Quantum Theory; Spectrometry, Fluorescence

Stable tetracoordinated organoboron complexes as classic fluorescent molecules have found various applications in material and medical sciences. A new class of curcumin-BF2 complexes has been prepared from the condensation of 2,2-difluoro-1,3-dioxaborylpentadione with a variety of aldehydes and its photophysical properties were characterized. Systematic variations were observed in the absorption spectra of these curcumin-BF2 dyes in solutions, which are well correlated with their structural features, including characteristics of the aromatic groups and presence of a para electron-donating substituent. Strong fluorescence that is tunable from 500 to 800 nm via variation of the polarity of the solvent and a moderate to good fluorescence quantum yield ranging from 0.24 to 0.58 in dichloromethane were observed in curcumin-BF2 complexes 1. By contrast, their asymmetrical analogue, curcumin-BF2 complexes 3 exhibit much lower fluorescence quantum yields. Besides their excellent photostabilities, these curcumin-BF2 dyes also show singlet oxygen generating capabilities.

Topics: Boron Compounds; Cell Line, Tumor; Crystallography, X-Ray; Curcumin; Fluorescent Dyes; Humans; Microscopy, Fluorescence; Models, Molecular; Molecular Structure; Photochemical Processes