We report an unprecedented reaction of a diketopyrrolopyrrole (DPP) with primary and secondary amines that results in the ring-opening of the core with loss of its fluorescence. The various characterization techniques used in this study, such as X-ray diffraction, NMR spectroscopy, mass spectrometry, and UV-vis analysis, warrant accurate identification of the structures of the newly synthesized compounds. DFT studies were also performed in order to understand the mechanism associated with this reaction.

A convenient synthesis of mono- and bis(aminophenyl)diketopyrrolopyrrole derivatives, and their conversion to diketopyrrolopyrrole-derived maleimides is reported. The ability of the new maleimides to act as turn-on fluorescent probes for the detection of cysteine, homocysteine or glutathione was evaluated and, remarkably, the limits of detection (LOD) were excellent, with one probe achieving 18 nM for cysteine within just 5 min. The new compounds exhibited Stokes shifts ranging from 66 to 73 nm.

This study reports the synthesis and characterization of two novel fluorescent conjugates, RhodTzTzCHO and RhodTzTzRhod, which integrate rhodamine B hydrazide units with a thiazolo[5,4-d]thiazole (TzTz) core via phenyl bridges. While rhodamine derivatives typically undergo ring-opening in acidic media, these conjugates exhibit a particularly unusual pH-dependent behavior: they remain in the nonfluorescent, closed spirolactam form across a wide range of acidic environments, including hydrochloric, sulfuric, and acetic acids. Significant ring-opening, evidenced by the emergence of intense colour and fluorescence, occurs exclusively in the presence of trifluoroacetic acid. This unique selectivity was thoroughly investigated using nuclear magnetic resonance, mass spectrometry, and density functional theory calculations to identify possible protonated structures in solution. Our results demonstrate that the ring opening in both RhodTzTzCHO and RhodTzTzRhod conjugates is strongly influenced by the electronic properties of the bonded groups and the solvent, leading to an extraordinary stabilization of the protonated form with the spirocyclic ring closed, particularly in dimethylformamide. These findings establish rhodamine-TzTz conjugates as robust sensors for specific acidic conditions, suggesting possible utility in contexts where selective acid detection is required.

Herein, we present a family of 7-(diethylamino)coumarin-3-carboxamides, bearing three different aza-crown moieties (chelating unit). All synthesized compounds have shown a colorimetric response and fluorescence ON-OFF behavior to the presence of lead, calcium, magnesium, and copper, with higher affinity toward the latter, even in the presence of other cations in solution. Optical spectroscopies, X-ray crystallography, and EPR experiments show that Cu(II) induces an irreversible oxidation on the coumarin core, with the concomitant formation of Cu(I) and an organic radical species. The emergence of an absorption band in the visible region upon radical formation results in the appearance of blue color, which fades over time, highlighting the potential of these sensors for rapid detection of copper(II) ion under the naked eye.

Diketopyrrolopyrroles (DPP) are a multifaceted family of organic dyes that have attracted considerable attention in optoelectronic applications due to their exceptional optical and electronic properties. In recent years, increasing efforts have been directed toward exploring the potential of DPPs in biological applications, including bioimaging and photodynamic therapy. Herein, we report the synthesis of two neutral and eight cationic DPP derivatives bearing different spacers and diverse cationic groups, and evaluate their photodynamic activity against Gram-positive methicillin-resistant Staphylococcus aureus (MRSA). All compounds, both in the absence and presence of potassium iodide (KI), induced a significant reduction in bacterial concentration (>3 log(10) CFU mL(-1)). In general, cationic derivatives exhibited superior photokilling activity. Notably, three compounds (6, 8 and 9) achieved bacterial photoinactivation to the detection limit of the quantification method after 30 min of white light irradiation at 5.0 mu M, corresponding to a reduction of 7.5 log(10) CFU mL(-1). The presence of KI enhanced the activity of five DPP derivatives. The relationship between structural features, photophysical properties, and photodynamic performance of the cationic DPPs shows that those containing octyl chains were typically more active photosensitizers compared to their benzylic chain counterparts. The enhanced activity of long alkyl chains may be linked to a membrane-destabilization effect. These findings highlight the potential of cationic DPPs as effective photosensitizers for the photodynamic inactivation of Gram-positive bacteria.

Herein, we present a family of 7‐(diethylamino)coumarin‐3‐carboxamides, bearing three different aza‐crown moieties (chelating unit). All synthesized compounds have shown a colorimetric response and fluorescence ON–OFF behavior to the presence of lead, calcium, magnesium, and copper, with higher affinity toward the latter, even in the presence of other cations in solution. Optical spectroscopies, X‐ray crystallography, and EPR experiments show that Cu(II) induces an irreversible oxidation on the coumarin core, with the concomitant formation of Cu(I) and an organic radical species. The emergence of an absorption band in the visible region upon radical formation results in the appearance of blue color, which fades over time, highlighting the potential of these sensors for rapid detection of copper(II) ion under the naked eye.

Diketopyrrolopyrroles (DPP) display remarkable photophysical and electronic properties, and are well-known for their application in the optoelectronic field. Currently, these compounds have gained special relevance for biological applications, including bioimaging, photodynamic therapy or as theranostic agents. In this work, the potential of two new cationic diketopyrrolopyrroles (1a and 2a) to (photo)inactivate Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli was assessed. Despite the low production of singlet oxygen (1O2), the combined action of these compounds with potassium iodide, after white light activation, triggers the production of reactive iodine species (RIS) which effectively inactivate the bacteria. At a concentration of 5.0 mu M, the dicationic compound 2a (+KI) photoinactivated S. aureus and the bioluminescent E. coli to the detection limit of the methods (7.00 log10 CFU and 4.83 log10 RLU reductions, respectively) after only 5 min and 10 min of irradiation. Under similar conditions, the monocationic compound 1a (+KI) required 30 min to fully inactivate S. aureus (7.66 log10 CFU reduction), but did not achieve a total inactivation of Gram-negative E. coli. The results indicate that the photoinactivation efficiency was influenced by the overall charge of the compounds, being both Gram-positive and Gram-negative strains successfully inactivated by the dicationic derivative, whereas the monocationic analogue was only effective against S. aureus.

Diketopyrrolopyrroles (DPP) are a versatile group of dyes and pigments with a wide range of applications, namely in the biological field. In this paper, we report the synthesis and the photodynamic activity of new cationic DPP derivatives that effectively inactivate Gram-positive and Gram-negative bacteria. These new compounds were synthetized using an easy synthetic procedure to introduce one or two pyridin-4-ylsulfanyl units followed by cationization. The photodynamic effectiveness of these DPP derivatives against Pseudomonas aeruginosa [Gram-negative] and methicillin-resistant Staphylococcus aureus [Gram-positive] strains was studied. Their photodynamic activity was also studied in the presence of potassium iodide (KI). Overall, both neutral and cationic DPP derivatives were highly effective in inactivating S. aureus, while only the cationic compounds were efficient against P. aeruginosa. Our findings suggest that for S. aureus, the production of singlet oxygen and a non-symmetrical structure were key factors in the photodynamic inactivation (PDI) success, whereas, for P. aeruginosa, the presence and number of cationic charges played a more significant role. In all cases, the application of KI reduced both the treatment time and PS concentration required for effective photodynamic inactivation of the studied bacteria. The ability to tailor simple DPP derivatives into effective DPP-based PSs for the inactivation of multidrug-resistant pathogenic bacterial strains, and the synergistic impact produced by the addition of KI, opens new possibilities for focused antimicrobial therapy.

An efficient protocol was developed for the microwave-mediated metallation of 5-(4-methoxycarbonylphenyl)-10,15,20-tris(pentafluorophenyl)porphyrin (P1) with bis(benzonitrile)platinum dichloride salt and subsequent 1,3-dipolar cycloaddition of the resulting PtP1 with an azomethine ylide to give two isomeric metallochlorins: PtC1 (main isomer) and PtC3. The methyl ester group of metalloporphyrin PtP1 and metallochlorin PtC1 was successfully hydrolysed in an alkaline medium to yield the corresponding derivatives PtP2 and PtC2 in moderate-to-good yields. As a proof of concept of the reactivity of the carboxy group in PtP2 and PtC2, these compounds were conjugated with a hydroxylated derivative of indomethacin, a known potent non-steroidal anti-inflammatory, obtaining the conjugates PtP2-Ind and PtC2-Ind. The obtained platinum(II) porphyrins and chlorins were characterized by UV-Vis, NMR spectroscopy and mass spectrometry. The structure of PtP1 was also confirmed by X-ray crystallography. Singlet oxygen generation studies were carried out, as well as theoretical calculations, which demonstrated that the prepared Pt(II) complexes can be considered potential photosensitizers for PDT.

The synthesis and spectroscopic studies of four sensors for fluoride chromogenic sensing are described. The new compounds were prepared by the Knoevenagel condensation of diformyl-substituted bipyrrolic and dipyrrolic synthons ([2,2 '-bipyrrole]-5,5 '-dicarbaldehyde and dipyrromethane-1,9-dicarbaldehyde moieties) with malononitrile or indane-1,3-dione. They strongly absorb in the visible region and significant color changes occur in the presence of fluoride anions. Acetate and dihydrogenphosphate anions also induce observable colorimetric changes, albeit to a lesser extent. These changes, which are visible to the unaided eye, are associated with NH- bonding interactions that are unique to each anion. Non-linear regression analysis of the ground- and excited- state changes revealed anion recognition in a 2:1 stoichiometry (Host:Guest), where the electronegative character of the substituents (malononitrile or indane-1,3-dione residues) controls the sensitivity of the binding. The proposed systems all feature exceptional anion receptors that display an impressive chromogenic response through NH-bonding. Among these, compound 3 stands out with exceptionally high affinity constants of up to 7.39x109 M-2, as well as an extremely low limit of detection at 92 ppm. NMR spectroscopy and mass spectrometry confirmed the structures of the synthesized compounds, with increased complexity in the NMR spectra due to the presence of malononitrile and indane-1,3-dione moieties. These findings highlight the potential of incorporating highly conjugated push-pull chromophores into bipyrrolic and dipyrrolic synthons for improved fluoride sensing performance in terms of both binding and signaling.

Click chemistry to allow in vivo conjugation of a fluorophore porphyrin (Por)-tetrazine (Tz) with the human epidermal growth factor receptor 2 (HER2)-targeting trastuzumab conjugated with trans-cyclooctene (TCO) is described here. In vitro experiments confirmed successful click reactions between Por-Tz and trastuzumab-TCO and validated preserved trastuzumab immunoreactivity (no significant change in HER2 binding, p > 0.05). Positron emission tomography (PET) of [89Zr]Zr-DFO-trastuzumab-TCO demonstrated 17.1 ± 2.9% injected dose per gram of tumor at 48 h postinjection. Optical imaging showed an ∼10-fold increase in the click group for Por-Tz when compared with Por-Tz alone. This preclinical data demonstrate a pretargeted approach for dual PET and optical imaging of HER2-expressing tumors.

Characterized by a remarkable chemical versatility and outstanding photophysical properties, porphyrins stand out as one of the most promising classes of photosensitizers for antimicrobial photodynamic therapy (aPDT). In this work, we described the synthesis, as well as the chemical and photophysical characterization of quinolinium-substituted porphyrins, and their corresponding Zn(II) complexes. The efficacy of these porphyrins in the photoinactivation of bacteria was evaluated, both alone and combined with the co-adjuvant potassium iodide, against methicillin-resistant Staphylococcus aureus (MRSA, Gram-positive) and Escherichia coli (Gram-negative) strains. Overall, the results demonstrated the high potential of both cationic porphyrins to effectively photoinactivate bacterial strains. Cationic derivative 2, at a concentration of 1.0 μM, achieved reductions exceeding > 99.99999 % (>7.0 log10 CFU mL-1) for S. aureus after 10 min of white light irradiation (25 mW cm-2) and > 99.9 % (3.52 log₁₀ RLU) for E. coli after 60 min aPDT treatment. Similarly, the Zn(II) counterpart 2a also showed excellent efficiency, achieving ∼99.999 % reduction (4.95 log10 CFU mL-1) against MRSA after 60 min of aPDT at 1.0 μM, and a 3.52 log₁₀ RLU reduction for E. coli after 30 min of PDT at 5.0 μM. The action mechanism of both cationic quinolinium-substituted porphyrins demonstrated to be dependent on the singlet oxygen production, consistent with a Type II photodynamic pathway. The use of potassium iodide (KI) as co-adjuvant led to the production of reactive iodine species (RIS), namely iodine, and increased the photodynamic effect.

In this study, a computer-aided drug design (CADD) approach was developed for a focused chemical library of eight synthesized thiazolo[5,4-c]isoquinoline (TzIQ) derivatives, including four neutral compounds and their corresponding cationic derivatives, all methylated at N4. Our CADD approach involved target prediction using Mondrian conformal prediction with the ChEMBL database, which contains data from 550 human protein targets with diverse bioactivity profiles. This analysis identified that TzIQ had a high probability of being active against the enzyme dihydrofolate reductase (DHFR). Moreover, molecular docking predictions against Staphylococcus aureus DHFR (saDHFR) and Escherichia coli DHFR (ecDHFR) highlighted three promising TzIQ for each enzyme: 2, 4, and 8 for saDHFR, and 4, 7, and 8 for ecDHFR. These compounds demonstrated significant ligand-protein energy scores and relevant binding affinities with the saDHFR and ecDHFR pocket residues, respectively. The subsequent in vitro antibacterial evaluation against S. aureus and E. coli confirmed the docking predictions for derivative 8 in both bacteria. Additionally, derivatives 6 and 7 emerged as novel antibacterial compounds against S. aureus, with all hits exhibiting MIC values <= 100 mu g/mL.

The functionalization of halogenated thiazolo[5,4-c]isoquinolines (TzIQ) through the Suzuki-Miyaura reaction with arylboronic acids is reported here for the first time. Three TzIQ derivatives bearing only chlorine atoms or chlorine and bromine atoms were used in this work. The results unequivocally confirm the impact of different halogen atoms, and their positions on the TzIQ core, on the outcome of these reactions. Excellent chemoselectivity was observed for the TzIQ bearing chlorine and bromine atoms. The new TzIQ derivatives were fully characterized by NMR and MS techniques and the structure of the TzIQ 9b was also confirmed by single-crystal X-ray diffraction. The absorption and emissive properties of the new compounds indicate that some of them may be useful in applications requiring strong luminescence and large Stokes shifts.

The photoactive properties of organic dyes are paramount when foreseeing their applications. This study investigated a series of structurally related diketopyrrolopyrrole-based materials using time-resolved laserinduced lensing technique to evaluate the effects of solvent viscosity and molecular oxygen availability in their photophysical properties. The absorption and photoluminescence spectra were determined, and the molecules diluted in DMSO had their singlet oxygen (1O2) production measured. The thermal and photostability of the architectures under investigation are quantitatively measured and discussed. The results showed that the thermal conversion rate is - 30 % for all studied systems. Consequently, their high quantum yield efficiencies are - 70 %. The photoactive response results provided relevant information for current and future applications of these materials, which may broaden their technological relevance towards bifunctional probes.

Diketopyrrolopyrroles (DPPs) are a versatile group of dyes and pigments with valuable optoelectronic properties. In this work we report the synthesis of highly fluorescent DPP derivatives through straightforward nucleophilic aromatic substitution reactions with thiols and phenols. These nucleophilic substitutions occur at room temperature and manifest a remarkable selectivity for the 4-position of the pentafluorophenyl groups. Both symmetrical (disubstitution) and non-symmetrical (monosubstitution) DPP derivatives are formed in excellent overall yields. The optical properties of the newly synthesized compounds are also discussed. The new platform may be useful for bioorthogonal chemistry.

New β-amino-substituted porphyrin derivatives bearing carboxy groups were synthesized and their performance as sensitizers in dye-sensitized solar cells (DSSC) was evaluated. The new compounds were obtained in good yields (63–74%) through nucleophilic aromatic substitution reactions with 3-sulfanyl- and 4-sulfanylbenzoic acids. Although the electrochemical studies indicated suitable HOMO and LUMO energy levels for use in DSSC, the devices fabricated with these compounds revealed a low power conversion efficiency (PCE) that is primarily due to the low open-circuit voltage (Voc) and short-circuit current density (Jsc) values.

Industrialization and town urbanization have led to an exponential need for clean water and new wastewater treatment strategies. Currently, photocatalysis is the most appealing method to destroy organic pollutants in water, and the use of sunlight, with the assistance of a solid photocatalyst, is considered one of the most sustainable approaches. The use of heterogeneous photocatalysts has unique advantages, namely their recovery and reuse for several cycles without loss of activity. Due to their remarkable optical and photophysical properties, porphyrin (Por) dyes can be used in homogenous and heterogeneous photocatalysis. Different supports can be used to immobilize Pors, allowing the final material to extend its absorption into the white light region since most of the supports only absorb UV light. This review focuses on the photocatalytic performance of non-immobilized and immobilized porphyrins in the photodegradation of organic pollutants for wastewater treatment application. Industrialization and town urbanization have led to an exponential need for clean water and new wastewater treatment strategies.

In the present work, several coumarin-3-carboxamides with different azacrown ether moieties were designed and tested as potential luminescent sensors for metal ions. The derivative containing a 1-aza-15-crown-5 as a metal chelating group was found to yield the strongest response for Ca2+ and Pb2+, exhibiting an eight- and nine-fold emission increase, respectively, while other cations induced no changes in the optical properties of the chemosensor molecule. Job’s plots revealed a 1:1 binding stoichiometry, with association constants of 4.8 × 104 and 8.7 × 104 M–1, and limits of detection of 1.21 and 8.04 µM, for Ca2+ and Pb2+, respectively. Computational studies suggest the existence of a PET quenching mechanism, which is inhibited after complexation with each of these two metals. Proton NMR experiments and X-ray crystallography suggest a contribution from the carbonyl groups in the coumarin-3-carboxamide fluorophore in the coordination sphere of the metal ion.

The assessment of thiazolothiazoles (TzTz) as photosensitizers in photodynamic inactivation (PDI) experiments is reported for the first time. Mono and dicationic TzTz derivatives were synthesized, and their photosensitizing ability was assessed on Staphylococcus aureus cells, both in suspension or attached to a surface, and using white light. The biological results showed that the photodynamic efficiency of these derivatives is dependent on the TzTz structure and irradiation time. The best results were obtained with the monocationic derivative TPATzTzPyMe & thorn; that allowed to reach a value over 7 log (99.9999 %) cell inactivation after white light irradiation for 30 min. Furthermore, TPATzTzPyMe & thorn; also revealed to be effective on the inactivation of S. aureus adhered to surfaces, a good indication of its potential to prevent biofilm formation. TPATzTzPyMe & thorn; was also effective against Escherichia coli , with a reduction in cell viability of 5.7 log after irradiation for 30 min.