Florencio Moreno

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.

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.

Preparation of dipyrrins from F-BODIPYs by treatment with methanesulfonic acids

An alternative metal-free soft procedure for the preparation of dipyrrins from F-BODIPYs is reported. The new method makes possible to obtain certain dipyrrin derivatives that were unaccessible from F-BODIPYs to date. To demonstrate the ability of the new procedure, dipyrrins having highly reactive groups, such as chloro, cyano or acetoxyl, have been easily obtained from the corresponding F-BODIPY, which shows the synthetic utility of the reported methodology.

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.

Chiroptical behavior of BINOL-based spiranic O -BODIPYs. A study on the influence of the structural factors

Spiranic O-BODIPYs bearing a phenol-based bi(polyarene) unit tethered to the boron center through oxygen atoms constitute an interesting family of BINOL-BODIPY dyads useful for the development of photonic applications due to their synthetic accessibility and tunable photonic properties. We found previously that the electron-donor capability of the involved BINOL moiety switched on a non-emissive intramolecular charge transfer (ICT) state, which restricted the fluorescence efficiency of the dyad. We demonstrated that the influence of this non-radiative deactivation channel can be efficiently modulated by the substitution pattern, either at the dipyrrin core or at the polyarene moiety, being possible to diminish or even virtually cancel the ICT probability, and hence achieve bright fluorescence upon dual excitation at far-away spectral regions.1 Additionally, we demonstrated that this simple structural motif exhibits chiroptical properties (circular dichroism, CD, and circularly polarized luminescence, CPL), as a consequence of the chiral perturbation exerted by the BINOL-based unit over the inherently achiral BODIPY chromophore.2 Based on these previous results, we found interesting to carry out a comprehensive study on the influence of the structure of both the BODIPY chromophore and the BINOL moiety over the chiroptical properties of this family of O-BODIPYs, directed to the improvement of said properties for their use in photonic applications. This communication reports the most important preliminary results obtained from this study, directed to the design of improved BODIPYs for Chiroptics. [1] Gartzia-Rivero, L.; Sanchez-Carnerero, E. M.; Jimenez, J.; Banuelos, J.; Moreno, F.; Maroto, B. L.; Lopez-Arbeloa, I.; de la Moya, S. Modulation of ICT probability in bi(polyarene)-based O-BODIPYs: towards the development of low-cost bright arene-BODIPY dyads. Dalton Trans. 2017, 46, 11830. [2] Sanchez-Carnerero, E. M.; Moreno, F.; Maroto, B. L.; Agarrabeitia, A. R.; Ortiz, M. J.; Vo, B. G.; Muller, G.; de la Moya, S. Circularly Polarized Luminescence by Visible-Light Absorption in a Chiral O-BODIPY Dye: Unprecedented Design of CPL Organic Molecules from Achiral Chromophores. J. Am. Chem. Soc. 2014, 136, 3346.