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Publications 2021



New Organic Materials Based on Multitask 2H-benzo[d]1,2,3-triazole Moiety


I. Torres-Moya, J. R. Carrillo, Á. Díaz-Ortiz, P. Prieto

Chemosensors 2021, 9, 267


Multifunctionality is a desirable aspect in materials science. Indeed, the development of multifunctional compounds is crucial for sustainable chemistry by saving resources and time. In this sense, 2H-benzo[d]1,2,3-triazole (BTz) is an excellent candidate with promising characteristics, including its ability to self-assemble; its acceptor character, which enables the synthesis of donor-acceptor structures; and its facile modulation using standard chemical methods. Thus, due to its interesting properties, it is possible to produce different derivatives with applications in different fields, as summarized in this article, with the correct substitution at the BTz cores. Optoelectronic or biomedical applications, amongst others, are highlighted.


DOI: 10.3390/chemosensors9090267

Structure, isomerization and dimerizationprocesses of naringenin flavonoids

A. González Moreno, P. Prieto, M. C. Ruiz Delgado, E. Domínguez, A. Heredia, A. de Cózar

Phys. Chem. Chem. Phys., 2021, 23, 18068

In this study, the theoretical and experimental results on the molecular structure and reactivity of the plant flavonoids naringenin chalcone and naringenin are reported. UV-vis and Raman spectra were recorded and their main bands have been assigned theoretically. Moreover, the analysis of the naringenin chalcone–naringenin cyclization–isomerization reaction and the formation of homodimers and heterodimers have been performed within a DFT framework. The presence of H-bonded water networks is mandatory to make the cyclization energetically suitable, suggesting that this equilibrium will occur in an aqueous intracellular environment rather than in the extracellular and hydrophobic plant cuticles. Additionally, the preferential formation of homodimers stabilized by π–π stacking that will interact with other dimers by H-bonding over the formation of naringenin chalcone–naringenin heterodimers is also proposed in a hydrophobic environment. These results give a plausible model to explain how flavonoids are located within the cuticle molecular arrangement.

DOI: 10.1039/d1cp01161h


Polarised Optical Emission from Organic Anisotropic Microoptical Waveguides Grown by Ambient Pressure Vapour-deposition

C. Tardío, V. V. Pradeep, R. Martín, A. M. Rodríguez, A. de la Hoz, R. Jada, M. Annadhasan, P. Prieto, R. Chandrasekar

Chem Asian J. 2021, 16, 3476–3480

Ambient pressure chemical vapour deposition of 5,5’-bis((2-(trifluoromethyl)phenyl)ethynyl)-2,2’-bithiophene provides ultrapure needle-shaped crystals. The crystal‘s
supramolecular structure consists of an array of hydrogen bonds and π-π interactions leading to anisotropic arrangements. The cyan emitting crystals exhibit an optical waveguiding tendency with guided polarised optical emissions due to anisotropic molecular arrangements.



Flow Chemistry in Fine Chemical Production

A. M. Rodríguez, I. Torres, A. Díaz-Ortiz, A. de la Hoz, J. Alcázar

in Flow Chemistry Graduate Textbook Volume 1-2. 2nd Edition. F. Darvas, G. Dormán, V. Hessel, S. V. Ley eds. De Gruyter.  

Vol. 2, 193-228, 2021

ISBN: 9783110693591 eISBN: 9783110693775

Flow Chemistry technology has been extensively researched in the pharma and life science industry over the last two decades. In recent years, flow chemistry has also expanded to other industrial fields, such as agrochemicals and fragrance development. It is clear that flow chemistry can provide significant advantages over more commonly used methods and it has the potential to revolutionise certain aspects of R&D in the industries mentioned above. These new methods need to comply with environmental regulations and pollution prevention to avoid climate change and environmental damage, both factors that are now of critical importance.


C(sp3)−C(sp3) Bond Formation via Electrochemical Alkoxylation and Subsequent Lewis Acid Promoted Reactions

E. López,C. van Melis,R. Martín,A. Petti,A. de la Hoz, A.Díaz-Ortíz,A. P. Dobbs,K. Lam,J. Alcázar

Adv. Synth. Catal. 2021, 363, 4521-4525

A two-step transition metal-free methodology for the C(sp3)−C(sp3) functionalisation of saturated N-heterocyclic systems is disclosed. First, aminal derivatives are generated through the anodic oxidation of readily accessible carboxylic acids. Then, in the presence of BF3 ⋅ OEt2, iminium ions are unmasked and rapidly alkylated by organozinc reagents under flow conditions. Secondary, tertiary and quaternary carbon centers have been successfully assembled using this methodology. Such an approach is especially relevant to drug discovery since it increases C(sp3)-functionalities rapidly within a molecular framework. As proof of concept, our methodology was applied to derivatization of peptides and an API.



The mechanism of the reaction of hydrazines with α,β-unsaturated carbonyl compounds to afford hydrazones and 2-pyrazolines (4,5-dihydro-1H-pyrazoles): Experimental and theoretical results

The reaction of hydrazines with α,β-unsaturated carbonyl compounds to afford 2-pyrazolines was studied using a dissymmetric chalcone (phenyl/p-tolyl) and three hydrazines, hydrazine itself, phenylhydrazine and thiosemicarbazide. Several products were identified, and some reaction paths established thanks to the evolution of 1H and 13C NMR spectra with time. Theoretical calculations on energies and chemical shifts were of paramount importance to ascertain the structure of some products. For important steps, the transition states were calculated while IRCs proved necessary to find some unexpected intermediates.



Insights Into the Micelle-Induced β-Hairpin-to-α-Helix Transition of a LytA-Derived Peptide by Photo-CIDNP Spectroscopy


A choline-binding module from pneumococcal LytA autolysin, LytA239–252, was reported to have a highly stable nativelike β-hairpin in aqueous solution, which turns into a stable amphipathic α-helix in the presence of micelles. Here, we aim to obtain insights into this DPC-micelle triggered β-hairpin-to-α-helix conformational transition using photo-CIDNP NMR experiments. Our results illustrate the dependency between photo-CIDNP phenomena and the light intensity in the sample volume, showing that the use of smaller-diameter (2.5 mm) NMR tubes instead of the conventional 5 mm ones enables more efficient illumination for our laser-diode light setup. Photo-CIDNP experiments reveal different solvent accessibility for the two tyrosine residues, Y249 and Y250, the latter being less accessible to the solvent. The cross-polarization effects of these two tyrosine residues of LytA239–252 allow for deeper insights and evidence their different behavior, showing that the Y250 aromatic side chain is involved in a stronger interaction with DPC micelles than Y249 is. These results can be interpreted in terms of the DPC micelle disrupting the aromatic stacking between W241 and Y250 present in the nativelike β-hairpin, hence initiating conversion towards the α-helix structure. Our photo-CIDNP methodology represents a powerful tool for observing residue-level information in switch peptides that is difficult to obtain by other spectroscopic techniques.


3-Pyrazolines (2,3-dihydro-1H-pyrazoles): synthesis, reactivity, physical and biological properties

A. de la Hoz, R. M. Claramunt, J. Elguero, I. Alkorta

Arkivoc 2021, part ix, 75-129

DOI: 10.24820/ark.5550190.p011.521

This account provides a summary of the current knowledge on 3-pyrazolines, an important but rather neglected field of heterocyclic chemistry. The review is divided into sections on the synthesis, reactivity, structure and biological properties and covers the literature from 1937 to 2020. In an effort to clarify some results, theoretical calculations were carried out anew.


Mechanical Processing of Naturally Bent Organic Crystalline Microoptical Waveguides and Junctions

V. V. Pradeep, C. Tardío, I. Torres-Moya, A. M. Rodríguez, A. V. Kumar, M. Annadhasan, A. de la Hoz, P. Prieto,* R. Chandrasekar*
Small 2021, 17, 2006795
DOI: 10.1002/smll.202006795
Precise mechanical processing of optical microcrystals involves complex microscale operations viz. moving, bending, lifting, and cutting of crystals. Some of these mechanical operations can be implemented by applying mechanical force at specific points of the crystal to fabricate advanced crystalline optical junctions. Mechanically compliant flexible optical crystals are ideal candidates for the designing of such microoptical junctions. A vapor‐phase growth of naturally bent optical waveguiding crystals of 1,4‐bis(2‐cyanophenylethynyl)benzene (1) on a surface forming different optical junctions is presented. In the solid‐state, molecule 1 interacts with its neighbors via CH⋅⋅⋅N hydrogen bonding and π–π stacking. The microcrystals deposited at a glass surface exhibit moderate flexibility due to substantial surface adherence energy. The obtained network crystals also display mechanical compliance when cut precisely with sharp atomic force microscope cantilever tip, making them ideal candidates for building innovative T‐ and Δ‐shaped optical junctions with multiple outputs. The presented micromechanical processing technique can also be effectively used as a tool to fabricate single‐crystal integrated photonic devices and circuits on suitable substrates.