Boron Difluoride Curcuminoid Fluorophores with Enhanced Two‐Photon Excited Fluorescence Emission and Versatile Living‐Cell Imaging Properties

Abstract

The synthesis of boron difluoride complexes of as eries of curcuminoidd erivatives 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 donors trengtho ft he end groups allows coveringab road spectral range, from the visible to the NIR region, of the UV-visible absorptiona nd fluorescence spectra.T wo-photon-excited fluorescence and Z-scan techniques prove that an increase in the donor strengtho r in the rigidity of the backboner esultsi naconsiderable increase in the two-photon cross section, reaching 5000 GM, with predominant two-photona bsorption from the S 0 -S 2 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 ad ipolar structure. Overall,t his structure-relationship study allowst he optimization of the two-photon brightness (i.e., 400-900GM) with one dye that emits in the NIR region of the spectrum.I na ddition, these dyes demonstrate high intracellularu ptakee fficiencyi nC os7 cells with emission in the visible region, which is further improved by using porous silican anoparticles as dye vehicles for the imaging of two mammalian carcinomac ells type based on NIR fluorescence emission.

Influence of the electron donor groups on the optical and electrochemical properties of borondifluoride complexes of curcuminoid derivatives: a joint theoretical and experimental study

“…33 Compounds 18, 19 where obtained from the p-N,N-dimethylamino-o-propoxyphenylcontaining hemicurcuminoid derivative. 34 The reaction of the hemicurcuminoid intermediate with one equivalent of the second aldehyde afforded the ligands. The borondiuoride complexes were obtained as described above for the symmetrical complexes.…”

“…In all our calculations, we applied the hybrid PBE0 exchange-correlation functional, 45 which is suited to reproduce absorption/emission trends of borondiuoride complexes. 34 In order to determine structural and vibrational parameters, the relatively compact 6-31G(d) atomic basis set was employed, while for electronic transitions the more extended 6-311+G(2d,p) atomic basis set was used. As the inuence of solvent effects is of paramount importance to estimate the electronic transition energies, here we applied the Polarizable Continuum Model (PCM), 46,47 using a linearresponse nonequilibrium approach for the TD-DDFT step.…”

“…26 Owing to their extended p-conjugated structure, their borondiuoride complexes exhibit strong visible absorption and uores-cence, [27][28][29][30][31][32][33] and unique near-infrared (NIR) emission in both solution and in the solid state using one-and two-photon excitation. 34,35 As a result of these features, they are attractive molecules for bioimaging and virtually any application requiring highly absorbing and emitting materials such as organic photovoltaics and optoelectronics.…”

Extended Alkenyl and Alkynyl Benzotriazoles with Enhanced Two‐Photon Absorption Properties as a Promising Alternative to Benzothiadiazoles

“…It is known that some TP chromophores undergo a S 2 ←S 0 transition, instead of the classical S 1 ←S 0 transition, joining higher electronic states (Figure a and Figures S4–S14 in the Supporting Information). This behavior is characteristic of quasi‐centrosymmetric quadrupolar molecules …”

Photophysical and Photoacoustic Properties of π‐Extended Curcumin Dyes. Effects of the Terminal Dimethylamino Electron‐donor and the Bridging Aryl Ring

“…The therapeutic use of turmeric and its easy extraction have made curcumin a highly investigated therapeutic compound. Indeed, interest in the development of synthetic curcumins inspired by the natural pigment has been increasing with applications in molecular devices , nonlinear optics , photovoltaics , light emitting diodes and photocatalysis . However, curcumin derivatives may also serve the medical field from a diagnostic perspective as a molecular contrast agent for fluorescence imaging and even photoacoustics (PA) imaging .…”