J. Vidal-Gancedo/J. Veciana (ICMAB-CSIC)
P. Mayorga-Burrezo, D. Blasi, V.G. Jiménez, T. Parella, I. Ratera, A.G. Campaña and J. Veciana
Chem. Eur. J., 26, 3776-3781 (2020). DOI
An enantiopure propeller-like trityl-brominated radical: Bringing together a high racemization barrier and an efficient circularly polarized luminescent magnetic emitter
A new persistent organic free radical has been synthetized with Br atoms occupying the ortho‐ and para‐positions of a trityl core. After the isolation of its two propeller‐like atropisomers, Plus (P) and minus (M), their absolute configurations were assigned by a combination of theoretical and experimental data. Remarkably, no hints of racemization were observed up to 60 °C for more than two hours, due to the higher steric hindrance imposed by the bulky Br atoms. Therefore, when compared to its chlorinated homologue (t1/2=18 s at 60 °C), an outstanding stability against racemization was achieved. A circularly polarized luminescence (CPL) response of both enantiomers was detected. This free radical shows a satisfactory luminescent dissymmetry factor (|glum(592 nm)|≈0.7×10−3) despite its pure organic nature and low luminescence quantum yield (LQY). Improved organic magnetic CPL emitters derived from the reported structure can be envisaged thanks to the wide possibilities that Br atoms at para‐positions offer for further functionalization.
J. L. Muñoz-Gómez, E. Monteagudo, V. Lloveras, T. Parella, J. Veciana and J. Vidal-Gancedo
RSC Advances, 6, 27077-27082 (2016). DOI
Optimized polarization build-up times in dissolution DNP-NMR using a benzyl amino derivative of BDPA
The synthesis of two novel BDPA-like radicals, a benzyl amino (BAm-BDPA, 7) and a cyano (CN-BDPA, 5) derivative, is reported and their behaviour as polarizing agents for fast dissolution Dynamic Nuclear Polarization (DNP) is evaluated. The radical 7 is a promising candidate for DNP studies since it is soluble in neat [1-13C]pyruvic acid (PA), and therefore the use of an additional glassing agent for sample homogeneity is avoided. In addition, a 60 mM sample of 7 offers optimum 13C NMR signal enhancements using fairly short polarization times (about 1800 s). It is shown that DNP-NMR measurements using 7 can be performed much more efficiently in terms of the signal enhancement per polarization build-up time unit than when using the reference OX63 or BDPA radicals. These enhanced features are translated to a substantial reduction of polarization times that represents an optimum temporary use of the DNP polarizer and allow economized liquid helium consumption.
J. L. Muñoz-Gómez, E. Monteagudo, V. Lloveras, T. Parella, J. Veciana and J. Vidal-Gancedo
Org. Biomol. Chem., 13, 2689-2693 (2015). DOI
A benzyl alcohol derivative of the BDPA radical for fast dissolution dynamic nuclear polarization NMR spectroscopy
A new polarizing agent for Dynamic Nuclear Polarization (BA-BDPA) is described. It meets all the requirements to become a promising candidate for its use in in vivo DNP-NMR experiments: it is soluble in neat [1-13C]pyruvic acid, insoluble in the dissolution transfer solvent and is effective as a polarizing agent in fast dissolution DNP-NMR applications, without the need for using glassing agents. Moreover, it enables a simple but effective in-line radical filtration to obtain hyperpolarized solutions of [1-13C]- pyruvic acid free of radicals that offers a better polarization performance.
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