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  1. Article ; Online: Excited-State Proton Transfer in Luminescent Dyes: From Theoretical Insight to Experimental Evidence.

    Fontes, Luís F B / Rocha, João / Silva, Artur M S / Guieu, Samuel

    Chemistry (Weinheim an der Bergstrasse, Germany)

    2023  Volume 29, Issue 57, Page(s) e202301540

    Abstract: The effective utilization of luminescent dyes often relies on a comprehensive understanding of their excitation and relaxation pathways. One such pathway, Excited-State Proton Transfer (ESPT), involves the tautomerization of the dye in its excited state, ...

    Abstract The effective utilization of luminescent dyes often relies on a comprehensive understanding of their excitation and relaxation pathways. One such pathway, Excited-State Proton Transfer (ESPT), involves the tautomerization of the dye in its excited state, resulting in a new structure that exhibits distinct emission properties, such as a very large Stokes' shift or dual-emission. Although the ESPT phenomenon is well-explained theoretically, its experimental demonstration can be challenging due to the presence of numerous other phenomena that can yield similar experimental observations. In this review, we propose that an all-encompassing methodology, integrating experimental findings, computational analyses, and a thorough evaluation of diverse mechanisms, is essential for verifying the occurrence of ESPT in luminescent dyes. Investigations have offered significant understanding of the elements impacting the ESPT process and the array of approaches that can be used to validate the existence of ESPT. These discoveries hold crucial ramifications for the advancement of molecular probes, sensors, and other applications that depend on ESPT as a detection mechanism.
    Language English
    Publishing date 2023-09-05
    Publishing country Germany
    Document type Journal Article ; Review
    ZDB-ID 1478547-X
    ISSN 1521-3765 ; 0947-6539
    ISSN (online) 1521-3765
    ISSN 0947-6539
    DOI 10.1002/chem.202301540
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  2. Article ; Online: Influence of the Intramolecular Hydrogen Bond on the Fluorescence of 2-ortho-Aminophenyl Pyridines.

    Esteves, Cátia I C / Fontes, Luís F B / Rocha, João / Silva, Artur M S / Guieu, Samuel

    Chemistry (Weinheim an der Bergstrasse, Germany)

    2022  Volume 28, Issue 53, Page(s) e202201844

    Abstract: The dynamic nature of excited-state intramolecular proton transfer (ESIPT) and its effect on emission spectra is an attractive strategy to create multi-emissive dyes. Here we describe the behavior of a series of hydrogen-bonded triphenylpyridines with a ... ...

    Abstract The dynamic nature of excited-state intramolecular proton transfer (ESIPT) and its effect on emission spectra is an attractive strategy to create multi-emissive dyes. Here we describe the behavior of a series of hydrogen-bonded triphenylpyridines with a set of donor-acceptor combinations that allowed us to perceive the influence of each substitution on the photophysical properties of the dyes. The susceptibility of these ESIPT moieties to pH variations was also studied, elucidating that the level of protonation had a significant effect on the emission color. The assignment of each emission band was made by using DFT and td-DFT calculations that were in agreement with the experimental results. This study emphasizes the versatility of triphenylpyridines that can be synthesized effortlessly with a logical and independent C-2, C-4 and C-6 substitution in order to have the desired ESIPT modulation and subsequent multi-emission response.
    MeSH term(s) Coloring Agents ; Hydrogen Bonding ; Protons ; Pyridines ; Spectrometry, Fluorescence
    Chemical Substances Coloring Agents ; Protons ; Pyridines
    Language English
    Publishing date 2022-08-25
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 1478547-X
    ISSN 1521-3765 ; 0947-6539
    ISSN (online) 1521-3765
    ISSN 0947-6539
    DOI 10.1002/chem.202201844
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  3. Article: Exploring the Luminescence, Redox, and Magnetic Properties in a Multivariate Metal-Organic Radical Framework.

    Valente, Gonçalo / Ferreira, Pedro / Hernández-Rodríguez, Miguel A / Brites, Carlos D S / Amaral, João S / Zelenovskii, Pavel / Paz, Filipe A Almeida / Guieu, Samuel / Rocha, João / Souto, Manuel

    Chemistry of materials : a publication of the American Chemical Society

    2024  Volume 36, Issue 3, Page(s) 1333–1341

    Abstract: Persistent neutral organic radicals are excellent building blocks for the design of functional molecular materials due to their unique electronic, magnetic, and optical properties. Among them, triphenylmethyl radical derivatives have attracted a lot of ... ...

    Abstract Persistent neutral organic radicals are excellent building blocks for the design of functional molecular materials due to their unique electronic, magnetic, and optical properties. Among them, triphenylmethyl radical derivatives have attracted a lot of interest as luminescent doublet emitters. Although neutral organic radicals have been underexplored as linkers for building metal-organic frameworks (MOFs), they hold great potential as organic elements that could introduce additional electronic properties within these frameworks. Herein, we report the synthesis and characterization of a novel multicomponent metal-organic radical framework (
    Language English
    Publishing date 2024-01-23
    Publishing country United States
    Document type Journal Article
    ZDB-ID 1500399-1
    ISSN 1520-5002 ; 0897-4756
    ISSN (online) 1520-5002
    ISSN 0897-4756
    DOI 10.1021/acs.chemmater.3c02460
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Multicomponent Synthesis of Luminescent Iminoboronates.

    Guieu, Samuel / Esteves, Cátia I C / Rocha, João / Silva, Artur M S

    Molecules (Basel, Switzerland)

    2020  Volume 25, Issue 24

    Abstract: A family of iminoboronates was prepared through a one-pot multicomponent reaction, starting from boronic acid, anthranilic acid, and different salicylaldehydes. Their synthesis was straightforward and the complexes were obtained in good to excellent ... ...

    Abstract A family of iminoboronates was prepared through a one-pot multicomponent reaction, starting from boronic acid, anthranilic acid, and different salicylaldehydes. Their synthesis was straightforward and the complexes were obtained in good to excellent yields. Their photophysical properties were assessed in a diluted solution, and the complexes proved to be faintly luminescent. These chelates demonstrated remarkable Aggregation-Induced Emission Enhancement, which was rationalized using crystal structures.
    MeSH term(s) Aldehydes/chemistry ; Boronic Acids/chemistry ; Fluorescent Dyes/chemistry ; Luminescence ; ortho-Aminobenzoates/chemistry
    Chemical Substances Aldehydes ; Boronic Acids ; Fluorescent Dyes ; ortho-Aminobenzoates ; anthranilic acid (0YS975XI6W) ; salicylaldehyde (17K64GZH20)
    Language English
    Publishing date 2020-12-21
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 1413402-0
    ISSN 1420-3049 ; 1431-5165 ; 1420-3049
    ISSN (online) 1420-3049
    ISSN 1431-5165 ; 1420-3049
    DOI 10.3390/molecules25246039
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Cologne/Königswinter

    Zs.MO 81: Show issues

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  5. Article: Benzimidazole-Based N,O Boron Complexes as Deep Blue Solid-State Fluorophores.

    Vaz, Patrícia A A M / Rocha, João / Silva, Artur M S / Guieu, Samuel

    Materials (Basel, Switzerland)

    2021  Volume 14, Issue 15

    Abstract: Benzimidazole-based boranils were designed and synthesized in order to assess the influence of halogen substituents on their optoelectronic properties. All compounds are photoluminescent in solution and solid state. Compared to the free ligands, the new ... ...

    Abstract Benzimidazole-based boranils were designed and synthesized in order to assess the influence of halogen substituents on their optoelectronic properties. All compounds are photoluminescent in solution and solid state. Compared to the free ligands, the new boranils emit at a lower wavelength, by elimination of the excited-state intramolecular proton transfer observed with the ligands. In the solid state, some of the boranils exhibit a deep blue emission, presenting Commission Internationale de l'Éclairage (CIE) coordinates with an x-component of less than 0.16 and a y-component smaller than 0.04, highly desired values for the development of blue emitting materials.
    Language English
    Publishing date 2021-07-31
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2487261-1
    ISSN 1996-1944
    ISSN 1996-1944
    DOI 10.3390/ma14154298
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Three-dimensional nanofibrous and porous scaffolds of poly(ε-caprolactone)-chitosan blends for musculoskeletal tissue engineering.

    Pereira, Andreia Leal / Semitela, Ângela / Girão, André F / Completo, António / Marques, Paula A A P / Guieu, Samuel / Fernandes, Maria Helena V

    Journal of biomedical materials research. Part A

    2022  Volume 111, Issue 7, Page(s) 950–961

    Abstract: One of the established tissue engineering strategies relies on the fabrication of appropriate materials architectures (scaffolds) that mimic the extracellular matrix (ECM) and assist the regeneration of living tissues. Fibrous structures produced by ... ...

    Abstract One of the established tissue engineering strategies relies on the fabrication of appropriate materials architectures (scaffolds) that mimic the extracellular matrix (ECM) and assist the regeneration of living tissues. Fibrous structures produced by electrospinning have been widely used as reliable ECM templates but their two-dimensional structure restricts, in part, cell infiltration and proliferation. A recent technique called thermally-induced self-agglomeration (TISA) allowed to alleviate this drawback by rearranging the 2D electrospun membranes into highly functional 3D porous-fibrous systems. Following this trend, the present research focused on preparing polycaprolactone/chitosan blends by electrospinning, to then convert them into 3D structures by TISA. By adding different amounts of chitosan, it was possible to accurately modulate the physicochemical properties of the obtained 3D nanofibrous scaffolds, leading to highly porous constructs with distinct morphologic and mechanical features. Viability and proliferation studies using adult human chondrocytes also revealed that the biocompatibility of the scaffolds was not impaired after 28 days of cell culture, highlighting their potential to be included into musculoskeletal tissue engineering applications, particularly cartilage repair.
    MeSH term(s) Adult ; Humans ; Tissue Engineering/methods ; Tissue Scaffolds/chemistry ; Chitosan ; Nanofibers/chemistry ; Porosity ; Polyesters/chemistry
    Chemical Substances polycaprolactone (24980-41-4) ; Chitosan (9012-76-4) ; Polyesters
    Language English
    Publishing date 2022-12-15
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2099989-6
    ISSN 1552-4965 ; 1549-3296 ; 0021-9304
    ISSN (online) 1552-4965
    ISSN 1549-3296 ; 0021-9304
    DOI 10.1002/jbm.a.37480
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    In stock of ZB MED Cologne/Königswinter

    Zs.A 6195: Show issues Location:
    Je nach Verfügbarkeit (siehe Angabe bei Bestand)
    bis Jg. 2021: Bestellungen von Artikeln über das Online-Bestellformular
    ab Jg. 2022: Lesesaal (EG)

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  7. Article: Mild Synthesis of Symmetric 3,5-Disubstituted Nitrobenzenes

    Francisco, Telmo N. / Sousa, Joana L. C. / Guieu, Samuel / Silva, Artur M. S. / Albuquerque, Hélio M. T.

    Synlett

    2022  Volume 33, Issue 15, Page(s) 1505–1510

    Abstract: A mild synthesis of 3,5-disubstituted nitrobenzenes from readily available 3-formylchromones is reported. The developed methodology follows a cascade process, promoted by 1,8-diazabicyclo[5.4.0]undec-7-ene. The proposed mechanism involves an initial ... ...

    Abstract A mild synthesis of 3,5-disubstituted nitrobenzenes from readily available 3-formylchromones is reported. The developed methodology follows a cascade process, promoted by 1,8-diazabicyclo[5.4.0]undec-7-ene. The proposed mechanism involves an initial Michael addition of nitromethane at C-2 of a 3-formylchromone. The resultant intermediate undergoes another Michael reaction with a second 3-formylchromone molecule. After ring closure through intramolecular cyclization, the aromatization is completed by deformylation, affording the 3,5-disubstituted nitrobenzenes in 52–86% yield. The reported method produces three new C–C bonds in a simple and straightforward manner, and it is consistent with gram-scale synthesis.
    Keywords nitrobenzenes ; formylchromones ; nitromethane ; Michael addition ; Nef reaction ; cascade reaction
    Language English
    Publishing date 2022-06-13
    Publisher Georg Thieme Verlag KG
    Publishing place Stuttgart ; New York
    Document type Article
    ZDB-ID 2042012-2
    ISSN 1437-2096 ; 0936-5214
    ISSN (online) 1437-2096
    ISSN 0936-5214
    DOI 10.1055/a-1875-2646
    Database Thieme publisher's database

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  8. Article ; Online: Curcumin-based molecular probes for fluorescence imaging of fungi.

    Ferreira, Joana R M / Alves, Mariana / Sousa, Bárbara / Vieira, Sandra I / Silva, Artur M S / Guieu, Samuel / Cunha, Ângela / Nunes da Silva, Raquel

    Organic & biomolecular chemistry

    2023  Volume 21, Issue 7, Page(s) 1531–1536

    Abstract: Fluorescence imaging is a powerful and widely used method to visualize and study living organisms. However, fungi are notoriously difficult to visualize using fluorescence microscopy, given that their cell wall represents a diffusion barrier, and the ... ...

    Abstract Fluorescence imaging is a powerful and widely used method to visualize and study living organisms. However, fungi are notoriously difficult to visualize using fluorescence microscopy, given that their cell wall represents a diffusion barrier, and the synthetic organic dyes available are very limited when compared to molecular probes available for other organisms. Moreover, these dyes are usually available in only one colour, preventing co-staining experiments. To fill this gap, curcumin-based molecular probes were designed based on the rationale that curcumin is fluorescent and has moderate toxicity toward fungi, implying its ability to cross the cell wall to reach targets in the intracellular compartments. A family of boron diketonate complexes was synthesized, based on a curcumin backbone, tuning their emission color from blue to red. These probes did not present noticeable toxicity to filamentous fungus and, when applied to their visualization, readily entered the cells and precisely localized in sub-cellular organelles, enabling their visualization.
    MeSH term(s) Curcumin/pharmacology ; Molecular Probes ; Fluorescent Dyes ; Optical Imaging ; Fungi
    Chemical Substances Curcumin (IT942ZTH98) ; Molecular Probes ; Fluorescent Dyes
    Language English
    Publishing date 2023-02-15
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2097583-1
    ISSN 1477-0539 ; 1477-0520
    ISSN (online) 1477-0539
    ISSN 1477-0520
    DOI 10.1039/d2ob01872a
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article ; Online: Tunable Color of Aggregation-Induced Emission Enhancement in a Family of Hydrogen-Bonded Azines and Schiff Bases.

    Guieu, Samuel / Cardona, Francisco / Rocha, João / Silva, Artur M S

    Chemistry (Weinheim an der Bergstrasse, Germany)

    2018  Volume 24, Issue 65, Page(s) 17262–17267

    Abstract: A simple synthesis strategy afforded a family of hydrogen-bonded azines and Schiff-bases. Although in dilute solution these dyes are faint light emitters, all exhibit bright luminescence upon aggregation. Changing the peripheral substituents from ... ...

    Abstract A simple synthesis strategy afforded a family of hydrogen-bonded azines and Schiff-bases. Although in dilute solution these dyes are faint light emitters, all exhibit bright luminescence upon aggregation. Changing the peripheral substituents from electron donating to electron withdrawing allows emission fine-tuning in a range from bluish-green to orange-red. The crystal structures of the materials reveal that the restriction of intramolecular rotations is the main mechanism for the aggregation-induced emission enhancement properties.
    Language English
    Publishing date 2018-11-02
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 1478547-x
    ISSN 1521-3765 ; 0947-6539
    ISSN (online) 1521-3765
    ISSN 0947-6539
    DOI 10.1002/chem.201802581
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  10. Article ; Online: Photodynamic control of citrus crop diseases.

    Ferreira, Joana R M / Sierra-Garcia, Isabel N / Guieu, Samuel / Silva, Artur M S / da Silva, Raquel Nunes / Cunha, Ângela

    World journal of microbiology & biotechnology

    2021  Volume 37, Issue 12, Page(s) 199

    Abstract: Citrus are economically important fruit crops to which infectious diseases like citrus canker caused by Xanthomonas citri subs. citri, citrus variegated chlorosis caused by Xylella fastidiosa, "huanglongbing" associated with the presence of Candidatus ... ...

    Abstract Citrus are economically important fruit crops to which infectious diseases like citrus canker caused by Xanthomonas citri subs. citri, citrus variegated chlorosis caused by Xylella fastidiosa, "huanglongbing" associated with the presence of Candidatus liberibacter species, anthracnose caused by Colletotrichum gloeosporioides and citrus black spot caused by Phyllosticta citricarpa, impose significant losses. Control measures involve chemical treatment of orchards but often, eradication of infected plants is unavoidable. To circumvent the environmental impacts of pesticides and the socio-economic impacts of eradication, innovative antimicrobial approaches like photodynamic inactivation are being tested. There is evidence of the susceptibility of Xanthomonas citri subs. citri and C. gloeosporioides to photodynamic damage. However, the realistic assessment of perspectives for widespread application of photodynamic inactivation in the control of citrus diseases, necessarily implies that other microorganisms are also considered. This review intends to provide a critical summary of the current state of research on photodynamic inactivation of citrus pathogens and to identify some of the current limitations to the widespread use of photodynamic treatments in citrus crops.
    MeSH term(s) Anti-Infective Agents ; Citrus/microbiology ; Citrus/physiology ; Colletotrichum/radiation effects ; Crops, Agricultural/microbiology ; Photosensitizing Agents ; Plant Diseases/microbiology ; Xanthomonas/radiation effects ; Xylella
    Chemical Substances Anti-Infective Agents ; Photosensitizing Agents
    Language English
    Publishing date 2021-10-19
    Publishing country Germany
    Document type Journal Article ; Review
    ZDB-ID 1499109-3
    ISSN 1573-0972 ; 0959-3993
    ISSN (online) 1573-0972
    ISSN 0959-3993
    DOI 10.1007/s11274-021-03171-7
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