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Publications 2019

2019

Physically Cross-Linked Hydrogel Based on Phenyl-1,3,5-triazine: Soft Scaffold with Aggregation-Induced Emission 

J. M. Galindo, J. Leganes, J. Patiño, A. M. Rodríguez, M. A. Herrero, E. Díez-Barra, S. Merino, A. M. Sanchez-Migallón, E. Vazquez

ACS Macro Lett. 2019, 8, 1391−1395

DOI: 10.1021/acsmacrolett.9b00712

A phenyltriazine compound has been used for the first time as a monomer in the construction of a hydrogel. This physically cross-linked soft material showed blue fluorescence when excited under UV-light. Polymer formation and intermolecular H-bonds arising from triazine moieties operate as aggregation-induced emission (AIE) mechanisms. The combination of soft materials and AIE properties expands the applications of these materials. As a proof of concept, two luminescent dyes have been incorporated into the hydrogel to produce a white-light-emitting material.

 

NMR Microcoils for On-line Reaction Monitoring in Flow Chemistry: Integrated Approaches for Practical Applications. S. V. Luis, E. García-Verdugo, RSC 2019

M. V. Gomez and A. H. Velders

Nuclear Magnetic Resonance (NMR) spectroscopy is one of the most important and powerful analytical tools available to the scientific community, and to synthetic chemists in particular. Standard, commercially available, high-field NMR spectrometers (running from 4.7 to 23.5 T, corresponding to 200, respectively 1000 MHz 1H Larmor frequency) have their radiofrequency antennas incorporated in probe heads that allow measuring samples in 5 mm tubes. Commercial probe heads that allow on-flow monitoring of reactions are based on, typically 5 mm, saddle coil designs, but these require relatively large amounts of material and/or have poor filling factors and correspondingly poor mass sensitivity. In 1994 Sweedler and co-workers launched the field of microcoil NMR spectroscopy, and the past two decades have seen several groups starting to fabricate their own small-volume probe-heads. Here we provide an overview of the different types of NMR microcoils that haven been developed to measure volumes in the lower microliter and (sub-)nanoliter scale, and then focus on the main geometries of microcoils exploited for use in reaction monitoring as solenoids, planar spiral, and stripline coils. Several examples are presented of on-flow and stationary reaction monitoring with such microcoils. The rapid progress in the field promises that many more groups will enter the field of NMR microcoil reaction monitoring in the coming years.

 

 

De Novo Design of Organic Photocatalysts: Bithiophene Derivatives for the Visible-light Induced C-H Funtionalization of Heteroarenes.

C. Bottecchia, R. Martín, I. Abdiaj, E. Crovini, J. Alcazar, J. Orduna, M. J. Blesa, J. R. Carrillo, P. Prieto, T. Noël.

Advanced Synthesis Catalysis2019, 361, 945-950.

DOI: 10.1002/adsc.201801571

Herein, we report the de novo synthesis and characterization of a series of substituted bithiophene derivatives as novel and inexpensive organic photocatalysts.

DFT calculations were used to predict a priori their absorption spectra and redox potentials, which were then confirmed with empirical data. The photocatalytic activity of this novel class of organic photoredox catalyst was demonstrated in two visible‐light mediated strategies for the C−H functionalization of heteroarenes. The implementation of these strategies in a continuous‐flow photo‐microreactor afforded moderate to excellent yields within few minutes of reaction time. Due to their straightforward synthesis, low cost and good photocatalytic properties we believe that the proposed bithiophene derivatives could be employed as a new class of organic photoredox catalysts.

 

 

High Thermal Stability pH responsive Organogels of 2H-benzo[d]1,2,3-triazole Derivatives as Pharmaceutical Crystallization Media.

I. Torres-Moya, B. Saikia, P. Prieto, J. R. Carrillo, J. W. Steed.

CrystEngComm2019, 21, 2135-2143. 

DOI: 10.1039/c8ce01742e

2H-Benzo[d]1,2,3-triazole derivatives with a range of chemical functionalities showed significant organogel formation, particularly bis-amide derivative 4e which gave robust thermally stable gels, in a range of solvents down to 0.1 wt%. The gelators proved responsive under pH stimuli or to the presence of metal cations. The gels also proved to be useful vehicles to crystallize pharmaceutical drugs, resulting in a change in polymorphic outcome in the case of sulfathiazole compared to the solution crystallization outcome.

 

Modulation of Waveguide Behaviour of an ICT 2H-Benzo[d][1,2,3]Triazole derivative with Graphene.

I. Torres, J. M. González-Domínguez, A. Díaz-Ortiz, C. Romero-Nieto, F. Rominger, E. Vazquez, J. R. Carrillo, P. Prieto.

Org. Elect. 2019, 68, 1-8.

doi.org/10.1016/j.orgel.2019.01.033

Needle-like supramolecular structures prepared by the organized aggregation of a 2H-benzo[d][1,2,3]triazole derivative with few-layer graphene using the slow diffusion technique are described. The as-prepared aggregate shows, by using scanning electron microscopy (SEM), the formation of needles with graphene attached on the surface, which was corroborated by Raman spectroscopy and optical microscopy. The graphene-modified aggregate acts as a selective optical waveguide for green light, in contrast to the pristine aggregate which emits green and red light. These new materials may be of crucial importance for the development of high-performance optoelectronic devices.

 

Synthesis and Properties of New Multiple TCNE-adducts from Dialkynyl-N-(het)arylpyrroles.

P. Pierrat, C. Cebrián, M. Beley, P. C. Gros, I. Torres-Moya, P. Prieto, S. Hess.

Eur. J. Org. Chem. 2019. 4341-4348.

DOI: 10.1002/ejoc.201900447

 We report the synthetic routes to mono‐ and di‐TCBD adducts onto N‐(het)arylpyrrole derivatives. We present herein two series of panchromatic chromophores bearing different combinations of donor–acceptor moieties. Additionally, we observe an impact of the nature of the central core. Cyclic voltammograms show very different behaviors at negative potentials between the two series. Particularly, four waves are observed for symmetrical di‐TCDB adducts, thus indicating a communication through the central unit despite the non‐planarity of these molecules.

 

Design, Synthesis and Amplified Spontaneous Emission of 1,2,5-Benzothiadiazole Derivatives

R. Martín, P. Prieto, J. R. Carrillo, A. M. Rodríguez, A. de Cózar, P. G. Boje, M. A. Díaz-García, M. G. Ramírez.

J. Mater. Chem. C. 2019, 7, 9996-10007.

DOI: 10.1039/c9tc03148k

The design, synthesis and evaluation of the amplified spontaneous emission (ASE) properties of a series of arylalkynyl-benzo[c][1,2,5]thiadiazole (BTD) and [1,2,5]thiadiazolo[3,4-g]quinoxaline (TDQ) derivatives are described. The synthetic strategy entailed the use of Sonogashira and Stille reactions based on the different aromatic natures of the two cores. The ASE properties were measured in thin polystyrene (PS) films doped with different concentrations of the synthesised compounds. BTD derivatives showed narrowing of the photoluminescence spectra (PL), thus revealing their potential laser applications. Only one TDQ derivative showed ASE. X-ray diffraction analysis was carried out to understand the observed results and to establish structure–property relationships. Molecules that showed strong molecular packing quenched the PL emission, thus giving rise to higher ASE thresholds. This is the first study in which ASE has been studied in BTD and TDQ derivatives and it represents a step forward in understanding this class of compounds for laser applications.

 

Extended Alkenyl and Alkynyl Benzotriazoles with Enhanced Two-Photon Absorption Properties as a Promising Alternative to Benzotiadiazoles.

I. Torres-Moya, C. Benitez-Martin, B. Donoso, C. Tardío, R. Martín, J. R. Carrillo, Á. Díaz-Ortiz, F. Nájera, P. Prieto, E. Perez-Inestrosa.

Chem. Eur. J. 2019, 25, 15572–15579.

DOI: 10.1002/chem.201903493.

A series of donor–π–acceptor–π–donor (D‐π‐A‐π‐D) benzoazole dyes with 2H‐benzo[d][1,2,3]triazole or BTD cores have been prepared and their photophysical properties characterized. The properties of these compounds display remarkable differences, mainly as a result of the electron‐donor substituent. Dyes with the best properties have visible‐light absorption over λ=400 nm, large Stokes shifts in the range of about 3500–6400 cm−1, and good fluorescence emission with quantum yields of up to 0.78. The two‐photon absorption properties were also studied to establish the relationship between structure and properties in the different compounds synthesized. These results provided cross sections of up to 1500 GM, with a predominance of S2←S0 transitions and a high charge‐transfer character. Time‐dependent DFT calculations supported the experimental results.

 

Cycloaddition of Nitrile Imines to Graphene: A Theoretical and Experimental Approach

H. Uceta, M. Vizuete, J. R. Carrillo, M. Barrejón, P. Prieto, F. Langa.

Chem. Eur. J. 2019, 25, 14644-14650.

DOI: 10.1002/Chem.201903105.

Density functional theory (DFT) studies of the interaction between graphene sheets and nitrile oxides have proved the feasibility of the reaction through 1,3‐dipolar cycloaddition. The viability of the approach has been also confirmed experimentally through the cycloaddition of few‐layer exfoliated graphene and nitrile oxides containing functional organic groups with different electronic nature. The cycloaddition reaction has been successfully achieved in one‐pot from the corresponding oximes under microwave (MW) irradiation. The successful formation of the isoxazoline ring has been confirmed by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X‐ray photoelectron spectroscopy (XPS).

 

Biothiophenes as a New Class of Organic Photoredox Catalysts.

C. Bottecchia, R. Martín, I. Abdiaj, E. Crovini, J. Alcazar, J. Orduna, M. J. Blesa, J. R. Carrillo, P. Prieto, T. Noël.

Synfacts, 2019, 15, 07, 0721.

DOI: 10.1055/s-0039-1689908

 

Flow Chemistry in Drug Discovery

J. Alcázar, A. de la Hoz, A. Díaz-Ortiz

Green Synthetic Processes and Procedures. Edited by Roberto Ballini. Chapter 4. Pp 57-78.

RSC. 2019

DOI: https://doi.org/10.1039/9781788016131-00053

This chapter provides an overview of the use of flow chemistry in drug discovery settings, first introducing the green characteristics of flow chemistry and then describing the drug discovery process and how both worlds can be matched. Examples are provided that cover all stages of drug discovery, from the identification of the initial hits to the preparation of Active Pharmaceutical Ingredients. The automation and integration of new green technologies are also reported.

A Critical Overview on the Effect of Microwave Irradiation in Organic Synthesis

Á. Díaz‐Ortiz, P. Prieto, A. de la Hoz

Chem. Rec. 201919, 85-97

DOI: 10.1002/tcr.201800059

Despite the great success of Microwave Assisted Organic Synthesis (MAOS) there is still a lack of knowledge about the interaction of the electromagnetic radiation with matter. In consequence, it has been very difficult to rationalize the effect of microwave irradiation in chemistry, to determine the existence of microwave effects (thermal and non‐thermal) and to develop predictive models on the characteristics required for a reaction to be improved under microwaves. This has been a handicap to develop new chemistry under microwave irradiation and the origin of many controversies. This personal account collects some new findings in this field and our work on the use of computational chemistry to develop predictive models and to determine parameters related to thermal and non‐thermal effects, with clear advantages over experimental methods where separation of these effect is almost impossible.

 

A spectral numerical model and an experimental investigation on radial microwave irradiation of water and ethanol in a cylindrical vessel

M.C. Navarro , A. Díaz-Ortiz , P. Prieto, A. de la Hoz

Applied Mathematical Modelling 201966, 680–694

DOI: 10.1016/j.apm.2018.09.035

In this paper the heating of a liquid sample in a cylindrical container subject to radial mi- crowave irradiation is studied numerically and experimentally. Two different solvents are used: water and ethanol. The model includes temperature dependence of the dielectric properties. A multi-dimensional axisymmetric numerical model based on spectral element methods, which allows the achievements of accurate results with low order spatial ex- pansions, is developed for solving heat and momentum equations coupled with Maxwell’s equations. Laboratory experiments are performed in a monomode microwave reactor. Nu- merical and experimental results are compared and analyzed. Results are of interest as they provide new possibilities in the prediction and understanding of the thermal behav- ior of a solvent under microwave irradiation.