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Publications 2017

2017

Colored Optical Waveguides in Self-assembled Thiadiazole-based Materials.

R. Martín, P. Prieto, J. R. Carrillo, I. Torres, C. A. Strassert. K. Soloviova, A. M. Rodríguez, L. Sánchez, A. Díaz-Ortiz.

Dyes & Pygments, 2018, 151, 327-334.

DOI: 10.1016/j.dyepig.2018.01.001

 The photophysical features and waveguiding behavior of two series of thiadiazoles are reported. The different substitution patterns on the thiadiazole moiety (1,3,4- or 1,2,5-system) result in bent and linear molecular geometries in which the peripheral substitution plays a prominent role in their aggregation ability. Thus, only the presence of the 3,4,5-trimethoxyaryl moiety favors the aggregation of thiadiazoles 5 and 8 into crystalline supramolecular structures. The linear geometry and the aggregation of the methoxy-substituted benzo[c][1,2,5]thiadiazole 8 have been corroborated by X-diffraction analysis. The photoluminescence (PL) quantum yields of the aggregated heterocycles 5 and 8 decreases with respect to the PL quantum yield in solution due to an aggregation-caused quenching (ACQ) effect. Despite this ACQ, the crystalline aggregates of both bent and linear thiadiazoles 5 and 8 exhibit waveguiding behavior with different emission colors (red, green and blue).

Grignard Reagents on a Tab: Direct Magnesium Insertion under Flow Conditions

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

Org. Lett. 2017, 19, 3747−3750

An on-demand preparation of organomagnesium reagents is presented using a new flow protocol. The risks associated with the activation of magnesium are circumvented by a new on-column initiation procedure.  Required amounts of solutions with a precise titration were obtained. Telescoped flow or batch reactions allow access to a diverse set of functional groups.

The organic chemistry of poly(1H-pyrazol-1-yl)methanes

I. Alkorta, R. M. Claramunt, E. Díez-Barra, J. Elguero, A. de la Hoz, C. López

Coordination Chemistry Reviews 339 (2017) 153–182

Since their first synthesis by Hückel (1937) and the first systematic exploration by Trofimenko (1970), interest in poly(1H-pyrazol-1-yl)methanes (bis, tris and tetrakis) has increased dramatically. This review focuses on the synthesis and reactivity of these ligands and contains 541 different structures and 269 references. After a brief historical introduction, the synthesis, reactivity, and nature of the coordinated metals are described along with some properties of these compounds, particularly the complete set of X-ray molecular structures. All of the formulae are represented to show the extraordinary richness of poly(1H-pyrazol-1-yl)methanes and to promote the use of the already known poly(1H-pyrazol-1-yl)methanes in coordination chemistry and the design of new ligands with the reported procedures.

Reformatsky and Blaise reactions in flow as a tool for drug discovery. One pot diversity oriented synthesis of valuable intermediates and heterocycles

L. Huck, M. Berton, A. de la Hoz, A. Díaz-Ortiz, J. Alcázar

Green Chem., 2017, 19, 1420-1424

The application of Reformatsky and Blaise reactions for the preparation of a diverse set of valuable intermediates and heterocycles in a one-pot protocol is described. To achieve this goal, a greener activation protocol for zinc in flow conditions has been developed to introduce this metal efficiently into α-bromoacetates. The organozinc compounds were added to a diverse set of ketones and nitriles to obtain a wide range of functional groups and heterocyclic systems.

Cover of a special issue on Recent advances in flow chemistry in the pharmaceutical industry. Editor: Stefan G. Koenig and Helen F. Sneddon

NMR reaction monitoring in flow synthesis

M.V. Gomez, A. de la Hoz

Beilstein J. Org. Chem. 2017, 13, 285-300.

Recent advances in the use of flow chemistry with in-line and on-line analysis by NMR are presented. The use of macro- and microreactors, coupled with standard and custom made NMR probes involving microcoils, incorporated into high resolution and benchtop NMR instruments is reviewed. Some recent selected applications have been collected, including synthetic applications, the determination of the kinetic and thermodynamic parameters and reaction optimization, even in single experiments and on the μL scale. Finally, software that allows automatic reaction monitoring and optimization is discussed.

Thematic issue on Automated Chemical Synthesis by invitationEditor. Ian R. Baxendale, Marcus Baumann, Richard Bourne

Non-conventional Techniques in Sustainable Flow Chemistry

A. de la Hoz, A. Díaz-Ortiz

Sustainable Flow Chemistry – Chapter 9. Methods and Applications.  Ed. L. Vaccaro, pp. 219-248.

Wiley-VCH

Enabling techniques have undergone significant developments in the past decade and the use of these approaches has modified the way in which organic synthesis is conducted. Continuous-flow processes benefit from facile automation, reproducibility, safety, process reliability and good heat and mass transfer. New synthetic technology platforms, however, are based on the combination of two or more of these enabling techniques. Flow methodologies have been combined with heterogeneous catalysis using supported reagents and scavengers on a wide variety of supports. In addition, neoteric solvents such as supercritical fluids have found a wide range of applications under flow conditions. However, one of the main advantages has been the application of non-conventional techniques for the introduction of energy into reactions, such as microwaves, ultrasound, electrochemistry, photochemistry and inductive heating. This approach provides conditions that are not easily achieved in batch reactions, since energy is transmitted and controlled in different ways in these two systems.

Understanding MAOS through Computational Chemistry

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

Chem. Soc. Rev. 2017, 46, 431-451

The importance of microwave irradiation in Organic Synthesis today is unquestionable, but in many cases the nature of these improvements remains unknown. Exploiting the benefits that microwave irradiation has in chemistry is still hindered by a lack of understanding of the physical principles of the interaction of microwave irradiation with the components of a reaction. Moreover, dielectric properties vary with temperature and along the reaction coordinate and this makes the situation more complex. Experimental determinations employed to date in Microwave-Assisted Organic Chemistry (MAOS) are characterized by the importance of thermal heating. In this way the separation of thermal heating from any other effect of the elecromagnetic radiation is completely impossible. This review provides an overview of the use of Computational Chemistry in MAOS to provide a theoretical understanding of the factors that can be used to explain the improvements in MAOS and how computational calculations can be used as a predictive tool.

Green synthesis of 1,3,5-triazines with applications in supramolecular chemistry and materials chemistry

A. Sánchez-Migallón, A. de la Hoz

Targets in Heterocyclic Systems 2017, 20, 140,175.

The 1,3,5-triazine ring is an extraordinary fragment that can take part in most types of intermolecular bonds. Microwave irradiation provides an efficient and green procedure for the selective preparation of s-triazines. Symmetrical and unsymmetrical 1,3,5-triazines have been obtained in good to excellent yields in short reaction times and under solvent free conditions. The structures have been determined by NMR-spectroscopy and X-ray crystallography. The optoelectronic and electrochemical properties have been investigated. The formation of complexes with Pd(II) and Ag(I), as well as the molecular recognition of glutarimide and riboflavin, demonstrate the extraordinary applications of these compounds.

By invitation of the editors: O. A. Attanasi, P. Merino, D. Spinelli

Tunable emission in aggregated T-Shaped 2H-Benzo[d][1,2,3]triazoles with waveguide behaviour

I. Torres, A. Díaz-Ortiz, L. Sánchez, J. Orduna, M.J. Blesa, J.R. Carrillo, P. Prieto

Dyes Pigments 142 (2017) 212-225

Symmetrical Donor-Acceptor-Donor (D-A-D) 2H-benzo[d][1,2,3]triazole derivatives have been designed by DFT calculations and prepared by a multistep synthetic protocol. The design strategy involved the identification of a suitable acceptor benzotriazole core and modification of the steric volume and donor strength of the branches in order to modulate the Intramolecular Charge Transfer (ICT) process and, consequently, the band gap. Self-assembly of the reported triazoles afforded organized supramolecular structures, the morphologies of which were visualized by SEM imaging. The outcomes demonstrated the effect that the donor moiety has on the emission properties and the morphologies of the aggregates. The aggregates that had a crystal-like structure, with smooth surfaces and flat end facets, exhibited optical waveguide behaviour with tunable colour emission. Depending on the initial design, the different emission wavelengths are related to the band gap of the benzotriazole derivatives.