Santiago de la Moya

Circularly Polarized Luminescence by Visible-Light Absorption in a Chiral O-BODIPY Dye: Unprecedented Design of CPL Organic Molecules from Achiral Chromophores

Circularly polarized luminescence (CPL) in simple (small, nonaggregated, nonpolymeric) O-BODIPYs (R)-1 and (S)-1 by irradiation with visible light is first detected as proof of the ability of a new structural design to achieve CPL from inherently achiral monochromophore systems in simple organic molecules. The measured level of CPL (|glum|) in solution falls into the usual range of that obtained from other simple organic molecules (10–5–10–2 range), but the latter having more complex architectures since axially chiral chromophores or multichromophore systems are usually required. The new design is based on chirally perturbing the acting achiral chromophore by orthogonally tethering a single axially chiral 1,1′-binaphtyl moiety to it. The latter does not participate as a chromophore in the light-absorption/emission phenomenon. This simple design opens up new perspectives for the future development of new small-sized CPL organic dyes (e.g., those based on other highly luminescent achiral chromophores and/or chirally perturbing moieties), as well as for the improvement of the CPL properties of the organic molecules spanning their use in photonic applications.

Selective lateral lithiation of methyl BODIPYs: synthesis, photophysics, and electrochemistry of new meso derivatives.

Selected meso BODIPYs (chemically reactive, difficult to obtain by established procedures, or photophysically or electrochemically attractive) have been obtained by unprecedented selective lateral lithiation of 8-methylBODIPYs. The physical study of the obtained new meso BODIPYs reveals interesting tunable properties related to the activation of intramolecular charge-transfer processes, endorsing the new synthetic methodology as useful for the development of smarter BODIPY dyes for technological applications.

Bis(haloBODIPYs) with Labile Helicity: Valuable Simple Organic Molecules That Enable Circularly Polarized Luminescence

Simple organic molecules (SOM) based on bis(haloBODIPY) are shown to enable circularly polarized luminescence (CPL), giving rise to a new structural design for technologically valuable CPL-SOMs. The established design comprises together synthetic accessibility, labile helicity, possibility of reversing the handedness of the circularly polarized emission, and reactive functional groups, making it unique and attractive as advantageous platform for the development of smart CPL-SOMs.

Chiral Organic Dyes Endowed with Circularly Polarized Laser Emission

The direct generation of efficient, tunable, and switchable circularly polarized laser emission (CPLE) would have far-reaching implications in photonics and material sciences. In this paper, we describe the first chiral simple organic molecules (SOMs) capable of simultaneously sustaining significant chemical robustness, high fluorescence quantum yields, and circularly polarized luminescence (CPL) ellipticity levels (|glum|) comparable to those of similar CPL-SOMs. All these parameters altogether enable efficient laser emission and CPLE with ellipticity levels 2 orders of magnitude stronger than the intrinsic CPL ones.

Negishi reaction in BODIPY dyes. Unprecedented alkylation by palladium-catalyzed C–C coupling in boron dipyrromethene derivatives

Negishi reactions of 3-halogen and 3,5-dihalogen substituted BODIPYs with different organozinc reagents are reported as the first examples of this valuable palladium-catalyzed C–C coupling reaction into the family of the BODIPY dyes. It is demonstrated that the Negishi coupling is especially useful for obtaining interesting alkylated BODIPYs, including synthetically-valuable asymmetrically-3,5-disubstituted BODIPYs.

Exploring the Application of the Negishi Reaction of HaloBODIPYs: Generality, Regioselectivity, and Synthetic Utility in the Development of BODIPY Laser Dyes

The generality of the palladium-catalyzed C-C coupling Negishi reaction when applied to haloBODIPYs is demonstrated on the basis of selected starting BODIPYs, including polyhalogenated and/or asymmetrical systems, and organozinc reagents. This reaction is an interesting synthetic tool in BODIPY chemistry, mainly because it allows a valuable regioselective postfunctionalization of BODIPY chromophores with different functional groups. In this way, functional patterns that are difficult to obtain by other procedures (e.g., asymmetrically functionalized BODIPYs involving halogenated positions) can now be made. The regioselectivity is achieved by controlling the reaction conditions and is based on almost-general reactivity preferences, and the nature of the involved halogens and their positions. This ability is exemplified by the preparation of a series of new BODIPY dyes with unprecedented substitution patterns allowing noticeable lasing properties.

Rational Design of Advanced Photosensitizers Based on Orthogonal BODIPY Dimers to Finely Modulate Singlet Oxygen Generation

The synthesis, photophysical characterization, and modeling of a new library of halogen-free photosensitizers (PS) based on orthogonal boron dipyrromethene (BODIPY) dimers are reported. Herein we establish key structural factors in order to enhance singlet oxygen generation by judiciously choosing the substitution patterns according to key electronic effects and synthetic accessibility factors. The photosensitization mechanism of orthogonal BODIPY dimers is demonstrated to be strongly related to their intrinsic intramolecular charge transfer (ICT) character through the spin-orbit charge-transfer intersystem crossing (SOCT-ISC) mechanism. Thus, singlet oxygen generation can be effectively modulated through the solvent polarity and the presence of electron-donating or withdrawing groups in one of the BODIPY units. The photodynamic therapy (PDT) activity is demonstrated by in vitro experiments, showing that selected photosensitizers are efficiently internalized into HeLa cells, exhibiting low dark toxicity and high phototoxicity, even at low PS concentration (0.05-5×10-6  m).

Circularly polarized laser emission induced in isotropic and achiral dye systems

The production of efficient, tunable, and switchable circularly polarized laser emission would have far reaching implications in optical communications or biophotonics. In this work, it is demonstrated the direct generation of circularly polarized (CP) laser emission in achiral and isotropic dye laser systems without the use of extracavity polarizing elements, and without resorting to chiral dyes, chiral liquid crystal matrices, or interferometric methods. The origin of this ellipticity arises from the dynamic birefringence induced by the strong and polarized laser pumping and the subsequent orientation anisotropy of the excited molecular dipoles. A complete polarimetric characterization of the polarization state of conventional dye laser oscillators as a function of different experimental parameters is performed and it is shown that the generated light always possesses a certain level of circularity that changes in a distinctive way with pump energy and polarization. These results demonstrate that it is possible to generate and modulate CP laser light from efficient and photostable conventional laser dyes.

N-BODIPYs Come into Play. Smart Dyes for Photonic Materials

N-BODIPYs (diaminoboron dipyrromethenes) are unveiled as a new family of BODIPY dyes with huge technological potential. Synthetic access to these systems has been gained through a judicious design focused on stabilizing the involved diaminoboron chelate. Once stabilized, the obtained N-BODIPYs retain the effective photophysical behavior exhibited by other boron-substituted BODIPYs, such as O-BODIPYs. However, key bonding features of nitrogen compared to those of oxygen (enhanced bond valence and different bond directionality) open up new possibilities for functionalizing BODIPYs, allowing an increase in the number of pendant moieties (from two in O-BODIPYs, up to four in N-BODIPYs) near the chromophore and, therefore, greater control of the photophysics. As a proof of concept, the following findings are discussed: (1) the low-cost and straightforward synthesis of a selected series of N-BODIPYs; (2) their outstanding photophysical properties compared to those of related effective dyes (excellent emission signatures, including fluorescence in the solid state; notable lasing capacities in the liquid phase and when doped into polymers; improved laser performance compared to the parent F-BODIPYs); (3) the versatility of the diaminoboron moiety in allowing the generation of multifunctionalized BODIPYs, permitting access to both symmetric and asymmetric dyes; (4) the capability of such versatility to finely modulate the dye photophysics towards different photonic applications, from lasing to chemosensing.

Exploring BODIPY meso -enamines as singlet-oxygen photosensitizers for PDT

We have recently reported on the control of Vilsmeier-Haack processes in meso-methylBODIPYs with activated DMF as the electrophilic reagent.1 Such a control allows the selective generation of beta-formylBODIPYs, BODIPY meso-enamines or BODIPY meso-iminium/enamine salts, by selecting properly the substitution pattern in the starting BODIPY, the hard (or soft) nature of the activated-DMF reagent, as well as the reaction conditions.1 It was also shown that meso-enamination deeply alters the photophysical properties of the BODIPY chromophore, quenching efficiently the fluorescence by the activation of non-radiative de-excitation channels, including intramolecular charge transfer (ICT), which in turn enables singlet-oxygen generation.1 This result, easy generation of a family of BODIPYs with potentiality to act as singlet-oxygen photosensitizers for photodynamic therapy (PDT)2 without involving heavy atoms or complex polyBODIPY designs, prompted us to detailed explore the scope of such a possibility. This presentation shows the results obtained from such an exploration, by reporting the most interesting results concerning singlet-oxygen generation in a selected family of BODIPY meso-enamines. [1] Palao, E.; Montalvillo-Jimenez, L.; Esnal, I.; Prieto-Montero, R.; Agarrabeitia, A. R.; Garcia-Moreno, I.; Banuelos, J.; Lopez-Arbeloa, I.; de la Moya, S.; Ortiz, M. J., Controlling Vilsmeier-Haack processes in meso-methylBODIPYs: A new way to modulate finely photophysical properties in boron dipyrromethanes. Dyes Pigments. 2017, 141, 286. [2] a) Kamkaew, A.; Lim, S. H.; Lee, H. B.; Kiew, L. V.; Chung, L. Y.; Burgess, K., BODIPY dyes in photodynamic therapy. Chem. Soc. Rev. 2013, 42, 77. b) Awuah, S. G.; You Y., Boron dipyrromethane (BODIPY)-based photosensitizers for photodynamic therapy. RSC Adv. 2012, 2, 11169.