Search

An anionic azobenzene-appended derivative of L-ValylGlycine self-assembles into nanotubes in water. Irradiation with 365 nm light provokes trans–cis isomerization of the azobenzene unit and subsequent tube disassembly. Thermal or photoinduced (457 nm light) recovery of the trans isomer restores the nanotubes.

Simulations based on molecular dynamics coupled to excitation energy calculations were used to generate simulated absorption spectra for a family of halide derivatives of azobenzene, a family of photoswitch molecules with a weak absorption band around 400–600 nm and potential uses in living tissue. This is a case where using the conventional approach in theoretical spectroscopy (estimation of absorption maxima based on the vertical transition from the potential energy minimum on the ground electronic state) does not provide valid results that explain how the observed band shape extends towards the low energy region of the spectrum. The method affords a reasonable description of the main features of the low-energy UV-Vis spectra of these compounds. A bathochromic trend was detected linked to the size of the halide atom. Analysis of the excitation reveals a correlation between the energy of the molecular orbital where excitation starts and the energy of the highest occupied atomic orbital of the free halide atom. This was put to the test with a new brominated compound with good results. The energy level of the highest occupied orbital on the free halide was identified as a key factor that strongly affects the energy gap in the photoswitch. This opens the way for the design of bathochromically shifted variants of the photoswitch with possible applications.

It is well known that light-induced multiple trans-cis-trans photoisomerizations of azobenzene derivatives attached to various matrices (polymeric, liquid crystalline polymers) result in polymer mass movement leading to generation of surface reliefs. The reliefs can be produced at small as well as at large light intensities. When linearly polarized light is used in the process, directional photo-induced molecular orientation of the azo molecules occurs, which leads to the generation of optical anisotropy in the system, providing that thermal effects are negligible. On the other hand, large reliefs are observed at relatively strong laser intensities when the optofluidization process is particularly effective. In this article, we describe the competitive thermocapillary Marangoni effect of polymer mass motion. We experimentally prove that the Marangoni effect occurs simultaneously with the optofluidization process. It destroys the orientation of the azopolymer molecules and results in cancelation of the photo-induced birefringence. Our experimental observations of polymer surface topography with atomic force microscopy are supported by suitable modelings.

The reversible photoisomerization of azobenzenes has been extensively studied to construct systems with optical responsiveness; however, this process limits the luminescence of these compounds. Recently, there have been many efforts to design and synthesize fluorescent azobenzene compounds, such as inhibition of electron transfer, inducing aggregation, and metal-enhancement, which make the materials ideal for application in fluorescence probes, light-emitting devices, molecular detection, etc. Herein, we review the recently reported progress in the development of various fluorescent azobenzenes and summarize the possible mechanism of their fluorescence emission. The potential applications of these materials are also discussed. Finally, in order to guide research in this field, the existing problems and future development prospects are discussed.

The possibility to characterize the electronic excited state of a spectrally active molecule based only on the solvatochromic study of electronic absorption spectra is demonstrated. The values of the regression coefficients given the contribution of universal interactions to the spectral shift and their theoretically established dependences on the solute molecule microscopic parameters are used. The values of the dipole moment, polarizability, and ionization potential in the ground electronic state of a spectrally active molecule are established by quantum mechanical methods. Two azo dye molecules are chosen in order to exemplify this method., Показана можливiсть охарактеризувати електронний збуджений стан спектрально активної молекули на основi лише сольватохромного дослiдження електронних спектрiв поглинання. Використанi величини коефiцiєнтiв регресiї з урахуванням вкладу унiверсальних взаємодiй у спектральний зсув i їх теоретично встановленi залежностi вiд мiкроскопiчних параметрiв розчинених молекул. Квантово-механiчнi методи застосованi для розрахунку дипольного моменту, поляризованостi i потенцiалу iонiзацiї основного стану. Метод iлюстрований на прикладi двох молекул азобарвника.

In the present study, photoirradiation molecularly imprinted polymer (MIP) with azobenzene was used as a functional monomer for the selective separation of the branched cyclodextrins. The functional monomer 4-methacryloyloxy azobenzene (MAA) and the molecular template 6-O-α-d-maltosyl-β-cyclodextrin (G2-β-CD) were implemented for the molecular imprinting. The core-shell structure of photoirradiation MIP was visualized by the transmission electron microscopy (TEM). With Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), we identified that G2-β-CD was imprinted into the polymer and removed from the MIP. The binding association constant (Ka) and the maximum number of the binding site (Nmax) were 1.72 × 104 M−1 and 7.93 μmol·g−1 MIP, respectively. With alternate irradiation at 365 and 440 nm light, the prepared MIP reversibly released and rebound to the G2-β-CD, which resulted in the nearly zero amount of G2-β-CD in the solution. The HPLC results indicated that the purity of G2-β-CD could reach 90.8% after going through MIP. The main finding of our study was that the photoirradiation of MIP was an easy and effective method for the selective separation of the branched cyclodextrins.

Azobenzene (di-phenyl-diazene) is a widely-studied prototype for its photoisomerisation capability. Whereas the trans-azobenzene is perfectly planar, the cis conformer assumes an inherent helicity, caused by the steric hindrance of each of the two benzene rings. In this study we explore by first principle DFT calculations the structural, mechanical, and chiroptical properties (Electronic Circular Dichroism spectra, ECD) of n-(phenylazo)-azobenzenes (n=. 1-10) from a computational point of view. The idea is that these polymers may photo-switch from a "strip"-like conformation (when each monomer is trans) to a "spring"-like conformation (when each monomer is cis). By studying the mechanical properties of these photo-induced nano-springs, we surprisingly obtain a nexus between the geometrical and elastic parameters and the Golden Ratio. © 2013 Elsevier B.V.

Phenylazopyridines are photoisomerizable compounds with high potential to control biological functions with light. We have obtained a series of phenylazopyridines with light dependent activity as negative allosteric modulators (NAM) of metabotropic glutamate receptor subtype 5 (mGlu5). Here we describe the factors needed to achieve an operational molecular photoisomerization and its effective translation into in vitro and in vivo receptor photoswitching, which includes zebrafish larva motility and the regulation of the antinociceptive effects in mice. The combination of light and some specific phenylazopyridine ligands displays atypical pharmacological profiles, including light-dependent receptor overactivation, which can be observed both in vitro and in vivo. Remarkably, the localized administration of light and a photoswitchable compound in the peripheral tissues of rodents or in the brain amygdalae results in an illumination-dependent analgesic effect. The results reveal a robust translation of the phenylazopyridine photoisomerization to a precise photoregulation of biological activity. © 2016 American Chemical Society., We are grateful to C. Serra and L. Muñoz for synthetic and analytical support, F. Malhaire for technical support in cell-based pharmacological assays, and Y. Pérez for NMR support. This research has been supported by RecerCaixa foundation (2010ACUP00378 to P.G., J.G., and A.L.), the Marató de TV3 Foundation (110230 to J.G., 110231 to A.L., 110232 to C.G., and 111531 to P.G.), the Catalan government (2010 BP-A 00194 to X.R., 2012FI_B 01122 to S.P., 2012 CTP 00033 and 2012 BE1 00597 to X.G.-S., 2014SGR-1251 to P.G., and 2014SGR-00109 to A.L.), the Spanish Government (CTQ2014-57020-R and PCIN-2013-017-C03-01 to A.L., PIE14/00034, SAF2014-55700-P, and PCIN-2013-019-C03-03 to F.C., and SAF2014-58396-R to J.G.), AWT (SBO-140028) to F.C., and the ERANET Neuron LIGHTPAIN project (to A.L., F.C., J.G., and J.-P.P.); SynBio MODULIGHTOR, Human Brain Project WAVESCALES and Ramon Areces foundation grants (to P.G.); the Agence Nationale de la Recherche (ANR-16-CE16-0010 to A.L. and C.G.).

Light-regulated drugs allow remotely photoswitching biological activity and enable plausible therapies based on small molecules. However, only freely diffusible photochromic ligands have been shown to work directly in endogenous receptors and methods for covalent attachment depend on genetic manipulation. Here we introduce a chemical strategy to covalently conjugate and photoswitch the activity of endogenous proteins and demonstrate its application to the kainate receptor channel GluK1. The approach is based on photoswitchable ligands containing a short-lived, highly reactive anchoring group that is targeted at the protein of interest by ligand affinity. These targeted covalent photoswitches (TCPs) constitute a new class of light-regulated drugs and act as prosthetic molecules that photocontrol the activity of GluK1-expressing neurons, and restore photoresponses in degenerated retina. The modularity of TCPs enables the application to different ligands and opens the way to new therapeutic opportunities., We are grateful to G. Swanson (Northwestern University Feinberg School of Medicine) for the GluK1-2b receptor clone and advice for DRG neuronal culture, and to M. Mayer (National Institutes of Health) for GluK1 S1S2 plasmid and purification protocol. We also thank E. Vázquez (Institut de Biotecnologia i Biomedicina, Universitat Autònoma de Barcelona) for providing the Origami-B (DE3) strain, and O. Seria, J.A. del Rio, G. Callejo and X. Gasull for help with DRG neuron cultures. We are grateful to D. Soto and A. Llobet for helpful discussions. MS was performed at the IRB Barcelona Mass Spectrometry Core Facility, which actively participates in the BMBS European COST Action BM 1403 and is a member of Proteored, PRB2-ISCIII, supported by grant PRB2 (IPT13/0001-ISCIII-SGEFI / FEDER). We want to thank M. Vilaseca and M. Vilanova for technical support with MS. We acknowledge financial support from the RecerCaixa foundation (2010ACUP00378); the Marató de TV3 Foundation (grants 110231 and 111531); the Human Brain Project (HBP SGA 1), the Catalan government (2012FI_B 01122, 2014SGR-1251, 2014SGR-00109 and 2009SGR-1072); the Spanish Government (SAF2012-36375, CTQ2013-43892R and CTQ2014-57020-R); the Ramón Areces foundation and the ERANET Neuron LIGHTPAIN and SynBio MODULIGHTOR projects.

The nitroxide radical coupling (NRC) reaction between the 4-(phenylazo)-benzoyl-2,2,6,6-tetramethylpiperidine-1-oxyl radical (AzO-TEMPO) or the 4-(2-thienylazo)-benzoyl-2,2,6,6-tetramethylpiperidine-1-oxyl radical (ThiO-TEMPO) and polyethylene macroradicals allowed the preparation of “functional” polyolefins bearing covalently grafted azo-aromatic chromophores. A comparison of the photo-physical behavior of the free and grafted RO-TEMPO molecules was carried out by UV-Vis spectroscopy irradiating the free RO-TEMPO solutions and the functionalized polymer films at 366 and 254 nm. Results evidenced the transfer of the photo-physical properties of the chromophores to the polymer matrix. Interestingly, some different isomerization abilities and kinetics between the free and grafted RO-TEMPO moieties, depending on the nature of the aromatic group bonded to the diazo-moiety and on the structure of the polymer matrix, were observed. Indeed, when the chromophores were grafted to the polymer, the isomerization resulted to be less efficient in terms of photo-isomerization degree and isomerization rate than in solution, suggesting a strong effect of the semi-crystalline matrix especially in the case of the more rigid HDPE. Finally the determination of the water contact angle of the functionalized polymers, before and after photo-isomerization, confirmed the occurrence of the isomerization and evidenced an increase of the wettability of the polymer surface owing to the process.

The electrochemical and spectroelectrochemical redox behaviour of two different monomers, suitable for non-linear optical applications, 3-[6-(4-oxy-4′-nitrostilbene)hexyl]thiophene and 3-{6-[4-(4′-nitrophenyl-azo)phenoxy]hexyl}thiophene, are investigated by cyclic voltammetry. In addition the suitable conditions for an electrochemical synthesis of the homopolymer and copolymer with some alkylthiophenes (3-methylthiophene and 3-hexylthiophene) are studied. The polymeric films obtained are characterised by electrochemical methods, spectroelectrochemical UV-vis-NIR and FT-IR in reflectance and compared with the polymer obtained by a chemical method, cast onto Pt and ITO glass surfaces. © 2003 Elsevier Science B.V. All rights reserved.

© 2014, Springer-Verlag Berlin Heidelberg. Density functional theory (DFT) calculations have been used to investigate the structural properties, dipole moments, polarizabilities, Gibbs energies, hardness, electronegativity, HOMO/LUMO energies, and chemical potentials of trans and cis configurations of eight para-substituted azobenzene derivatives. All properties have been obtained using the B3LYP functional and 6-31++G(d,p) basis set. The planar structures have been obtained for all optimized trans configurations. The energy difference between trans and cis configurations for considered derivatives was found to be between 64.2–73.1 kJ/mole. It has been obtained that the p-aminodiazo-benzene (ADAB) has the difference in the dipole moments between trans and cis forms higher than for trans and cis azobenzene.

5

The molecular orbital calculations have been carried out to investigate the structure and stability of (E) / (Z) isomers of some azobenzene derivatives containing maleimide groups. A special attention has been devoted to the compound (E)-1, (E)-1-(4-(phenyldiazenyl)phenyl)-1H-pyrrole-2,5-dione, for which the available crystallographic experimental data have been used to validate the modeling structures computed at the theoretical levels AM1, PM3, RHF/6-31+G(d,p) and B3LYP/6-31+G(d,p). To this end, the discrepancy between experimental and calculated structural parameters has been ascertained in terms of root-mean-square deviation (RMSD). The quantum calculations at the level RHF/6-31+G(d,p) yield the most accurate results on (E)-1 structure giving a deviation error from crystallographic data of about 5.00% for bond lengths and 0.97% for interatomic angles. The theoretical electronic absorption spectra of azobenzene derivatives of concern have been computed by means of configuration-interaction method (CI) at the level of semi-empirical Hamiltonians (AM1 and PM3). Likewise, the molecular energy spectra, electrostatic potential and some quantitative structure activity relationship (QSAR) properties of studied molecules have been computed and discussed in the paper. Electronic supplementary material The online version of this article (doi:10.1186/2193-1801-2-586) contains supplementary material, which is available to authorized users.

2006/2007 The first part of this thesis work concerns the development of an ultra–high–vacuum experimental system, hosting a commercial Low Temperature Scanning Tunneling Microscope (LT-STM), that has been built for characterizing and manipulating single molecules and molecular complexes adsorbed on metal surfaces. The design from scratch, the commissioning and the performance tests of the various components of the system are presented. The preparation chamber that has been developed provides the fundamental surface preparation and analysis instruments, combining the STM analysis with other experimental techniques and allowing for easy setup of additional preparation/analysis instruments. The manipulator sample stage allows for a wide temperature range, needed for the preparation of a variety of surfaces to be investigated in the LT-STM. In the second part of this work, we present two examples of how molecules and molecular complexes can be studied and manipulated with the LT-STM technique. In the first example, within a collaboration established with the group of Dr. Leonhard Grill at the Freie Universität in Berlin, we have characterized an azobenzene derivative adsorbed on the Au(111) surface, a known molecular switch based on a trans–cis isomerization, which can be reversibly induced by the tip of the STM with controlled voltage pulses. We could show how the molecule–molecule interactions play a critical role in determining the switching abilities of the molecules between different self–assembled molecular islands, and how the molecule–substrate interaction can efficiently determine two different spatial periodicities of the switching molecules. In the second example, we have presented preliminary results regarding the characterization of the NH3-NO complex which forms on the Pt(111) surface, showing that by exploiting the manipulation and spectroscopic tools of the LT-STM, it will be possible to investigate at the atomic scale the properties of the hydrogen bond most likely involved the complex. La prima parte di questa tesi descrive lo sviluppo di un sistema sperimentale da ultra–alto–vuoto, dotato di un microscopio a scansione a effetto tunnel a bassa temperatura (LT-STM) disponibile in commercio. Il sistema è stato concepito e costruito per caratterizzare e manipolare singole molecole e complessi di molecole adsorbiti su superfici metalliche. Viene descritta la realizzazione del sistema sperimentale, a partire dalla fase di progettazione fino alla messa in opera e ai vari test di funzionamento che sono stati effettuati. La camera di preparazione che è stata costruita è provvista della strumentazione di base per la preparazione e l’analisi dei campioni di misura, e permette di integrare la tecnica STM con altre tecniche sperimentali e di installare in modo semplice e veloce nuovi strumenti. Il manipolatore è dotato di un sistema di riscaldamento campioni che permette di raggiungere un largo intervallo di temperature, necessario per la preparazione di svariati tipi di campioni da poter studiare tramite l’LT-STM. Nella seconda parte della tesi, vengono presentati due esempi di come, grazie alle potenzialità dell’LT-STM, è possibile caratterizzare e manipolare molecole e complessi di molecole. Nel primo dei due esempi, nell’ambito di una collaborazione con il gruppo del Dr. Leonhard Grill presso la Freie Universität a Berlino, è stato studiato sulla superficie (111) dell’oro il comportamento di un derivato dell’azobenzene, un “interruttore molecolare” basato sul processo di isomerizzazione trans–cis che può essere indotto in modo reversibile tramite impulsi di voltaggio dalla punta del microscopio STM. Si è dimostrato come le interazioni inter–molecolari giocano un ruolo fondamentale nel determinare se, all’interno di isole molecolari con diversa struttura, le molecole possono isomerizzare o meno; inoltre è stato scoperto che l’interazione delle molecole con il substrato può determinare l’ordinamento delle molecole in grado di isomerizzare, in strutture di periodicità definita all’interno delle isole molecolari. Nel secondo esempio che viene descritto, vengono presentati i risultati preliminari della caratterizzazione del complesso NH3-NO che si forma sulla superficie (111) del platino, e viene indicato come sarà possibile caratterizzare la natura dei legami idrogeno, che probabilmente stabilizzano il complesso, tramite le tecniche spettroscopiche e di manipolazione messe a disposizione dall’LT-STM. XX Ciclo 1980

The synthesis of dimethylaminoazobenzene derivatives containing a β-d-glucopyranosyl ring is described. Structures have been defined by 1H NMR techniques, selective decoupling and 1H–1H COSY. Differential thermal analysis (DTA) and thermogravimetry (TG) have been used to describe their thermal behaviour. Genotoxicity (Ames test) comparisons with their p-methoxy counterparts have shown the effect of β-d-glucopyranosyl on reducing the mutagenicity.