Triarylamines and phenothiazines are electron-rich Π-systems and, therefore, as donor components omnipresent in organic electronics, organic photonics, and organic photovoltaics.1 For establishing design principles of donor systems, the interplay between modelling and experimental studies are fruitful, and, therefore, concise access to substance libraries of functional Π-systems by multicomponent reactions2,3 is highly desirable. Employing Pd-catalyzed sequences allows for the efficiently concatening ofelementary steps with a maximum of functional group tolerance in a one-pot fashion.4,5,6 These synthetic methodological advances allow xtensive physical organic structure–property correlations to be established in the electronic ground state (oxidation potential) as well as in the electronic excited state (absorption, emission). Concatenating Suzuki arylation and Buchwald–Hartwig amination in a consecutive three-component fashion7 sets the stage for comprehensive physical–organic correlation studies on the redox, absorption and emission properties of 3,10-diaryl phenothiazines8 and p-,m- and o-aryl triarylamines.9,10

1 Shirota, Y.; Kageyama, H. Chem. Rev. 2007, 107, 953.
2 Levi, L.; Müller, T. J. J. Chem. Soc. Rev. 2016, 45, 2825.
3 Brandner, L.; Müller, T. J. J. Front. Chem. 2023, 11, 1124209.
4 Müller, T. J. J. Top. Organomet. Chem. 2006, 19, 149.
5 Lessing, T.; Müller, T. J. J. Appl. Sci. 2015, 5, 1803.
6 Kornet, M. M.; Müller, T. J. J. Molecules 2024, 29, 5265.
7 Mayer, L.; Kohlbecher, R.; Müller, T. J. J. Chem. Eur. J. 2020, 26, 15130.
8 Mayer, L.; Müller, T. J. J. Eur. J. Org. Chem. 2021, 24, 3516.
9 Kohlbecher, R.; Müller, T. J. J. Chem. Eur. J. 2024, 30, e202304119.
10 Kohlbecher, R.; Lippert, T.; Schröder, H.; Jordan, D. N.; Janiak, C.; Müller, T. J. J. Eur. J. Org. Chem. 2026, 29, e70312.

The rational design of supramolecular assemblies enables precise modulation of molecular optical properties through controlled intermolecular interactions. This study employs density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to investigate the structure–property relationships governing the second-order nonlinear optical (NLO) responses in host–guest complexes formed between C₆₀ and carbon nanoring derivatives (B-PLY-CPP and N-PLY-CPP). The optimized geometries of B-PLY-CPP@C₆₀ and N-PLY-CPP@C₆₀ confirm stable convex–concave π–π stacking, with interaction energies of approximately –35 kcal/mol. The static​ first hyperpolarizability (β_tot), calculated at the CAM-B3LYP/6-31G(d) level, reveals that the N-doped complex (N-PLY-CPP@C₆₀) achieves a β_tot value of 1.01 × 10⁴ au, which is significantly higher than that of its B-doped analogue and is competitive with classic push–pull NLO chromophores. This enhancement correlates directly with a more efficient intermolecular charge transfer from the nanoring host to the C₆₀ guest, as evidenced by a substantial red-shift in the calculated low-energy absorption band. Analysis using a two-level model confirms that the superior NLO response originates from a lower transition energy and a larger transition dipole moment associated with this charge-transfer excitation. The results provide comparative mechanistic insights​ into how heteroatom doping and supramolecular organization can be used to tailor charge-transfer excited-state characteristics and enhance second-order NLO activity in carbon-based materials, highlighting a viable supramolecular strategy for property modulation.

Introduction: Sustainable, biocompatible fluorescent probes are increasingly needed for clinically relevant analytes. Protamine, the only clinically used antidote for heparin overdose, and uric acid, a key biomarker for metabolic, renal, and cardiovascular disorders, both require reliable quantification in biological fluids for effective clinical management.

Methods: Sulfur- and nitrogen-doped carbon dots (S,N-CDs) were synthesized via a one-step hydrothermal method using Ricinus communis (castor) seeds as a carbon source and thiourea as the nitrogen and sulfur dopant. Finely ground castor seed powder was mixed with thiourea in distilled water and heated in a sealed autoclave at 180 °C for 6 h to obtain S,N-CDs suitable for fluorescence-based sensing.

Results: The S,N-CDs showed uniform spherical morphology (2–8 nm), green emission (λ_em = 520 nm), and good stability toward pH variation, ionic strength, and photobleaching. Surface functional groups enabled a fluorescence turn-off response to both targets. Protamine was quantified over 3.2–7.2 µM (limit of detection 0.45 µM), with recoveries of 98.9–103.1% in spiked human serum. Uric acid was detected over 50–124.8 µM (limit of detection 16.7 µM), with recoveries of 94.9–101.8% in serum and 92.6–95.3% in urine. These results indicate that the probe can operate in complex biological matrices using a simple, low-cost fluorescence readout.

Conclusion: Castor seed-derived S,N-CDs function as an application-focused fluorescent probe for dual detection of protamine and uric acid in biological fluids. This study demonstrates a sustainable synthesis route and links the surface functionality of the CDs to their fluorescence response, supporting their utility for applied biosensing rather than mechanistic photophysical advancement.

Organic ligands containing conjugated C=N bonds can significantly enhance photophysical behavior [1]. While Ag(I) coordination polymers exhibit intriguing photophysical properties [2], Ag(I) is more reactive and less stable than Cd(II), motivating the exploration of Cd(II)-based systems as viable alternatives. In this work, we report the synthesis, photochemical, and photoluminescent properties of a new Cd(II) complex, [CdL₂I₂H₂O], L = ethyl-5-amino-1-methyl-1H-pyrazole-4-carboxylate.

The obtained compound was characterized by ATR-FTIR, molar conductivity in DMF, and X-ray diffraction. Room temperature fluorescence of the samples was measured using a 355 nm UV solid-state pulsed laser.

White crystals of the complex [CdL₂I₂H₂O] were obtained by reacting CdI₂ with L in methanol and in its mixture with other solvents as MeCN, Me₂CO, and H₂O. In the obtained complex, L coordinates through the unsubstituted nitrogen atom of the pyrazole ring. The asymmetric unit of this mononuclear complex comprises one Cd(II), two N-coordinated pyrazole ligands, two iodido ligands, and one coordinated water molecule. The Cd(II) center adopts a distorted trigonal-bipyramidal geometry.

Complex shows strong near-UV to blue fluorescence. The compound emits at 393 nm (powder/pellet) with FWHM 72/80 nm; intensity rises from 44,600 to 151,687 a.u.

A novel mononuclear Cd(II) complex pyrazole derivative ligand was synthesized and characterized. With its simple and accessible synthesis, [CdL₂I₂(H₂O)] represents a promising candidate for advancing existing Cd(II)-based luminophores and exploring structure–property relationships in photoluminescent materials.

[1] Ristić, P.; Sreekala, C. O.; Kulkarni, N. V.; Senthurpandi, D.; Mathew, J. J. Mol. Struct. 2022, 1266, 133512. https://doi.org/10.1016/j.molstruc.2022.133512

[2] Ristić, P.; Filipović, N.; Blagojević, V. A.; Ćirković, J.; Barta Holló, B.; Đokić, V. R.; Donnard, M.; Gulea, M.; Marjanović, I.; Klisurić, O. R.; Todorović, T. R. CrystEngComm 2021, 23, 4799–4815. https://doi.org/10.1039/d1ce00394a

Engineering luminescent nanomaterials capable of emitting stable multispectral visible light remains a key challenge in the development of advanced bioimaging technologies. While white-light emission from rare-earth co-doped phosphors has been widely explored, most existing systems rely on multi-component architectures, high-temperature synthesis routes, or host matrices with limited biocompatibility, restricting their applicability in biomedical environments. Achieving multispectral emission within a single, biocompatible, and structurally stable host therefore remains an open challenge.

In this work, a simple and low-energy room-temperature co-precipitation route (≈25 °C) is reported for the synthesis of spherical Dy³⁺/Eu³⁺ co-doped fluorapatite (Ca₅(PO₄)₃F) nanoparticles, establishing fluorapatite as an efficient single-host platform for multispectral emission. Owing to its intrinsic biocompatibility and structural flexibility, fluorapatite enables the simultaneous incorporation of multiple rare-earth ions without compromising phase purity or crystallographic integrity. Structural characterization confirms successful Dy³⁺ and Eu³⁺ substitution within the apatite lattice, while FESEM analysis reveals uniformly distributed spherical nanocrystalline particles.

Under near-UV excitation at 380 nm, the co-doped nanoparticles exhibit combined visible emission arising from the characteristic Dy³⁺ blue/yellow transitions and Eu³⁺ red emission, resulting in an overall white-light appearance. This combined multispectral emission enables the collection of spectral signals from multiple regions of the visible spectrum using a single nanomaterial, which is particularly advantageous for multispectral bioimaging and multiplexed detection. Importantly, this multispectral luminescence is achieved using a single excitation wavelength and a single biocompatible host matrix, eliminating the need for hybrid or multi-phase phosphor systems and reducing spectral cross-talk.

The combination of room-temperature synthesis, intrinsic biocompatibility, spherical morphology, and single-host multispectral emission positions Dy³⁺/Eu³⁺ co-doped fluorapatite nanoparticles as a versatile platform for multispectral biomedical imaging and related applications requiring stable luminescent probes.

The design of efficient organic sensitizers for dye-sensitized solar cells (DSSCs) depends critically on understanding their electronic structure and optical absorption behavior, as these properties directly influence light harvesting, charge separation, and electron injection efficiency. Triphenylamine-based p-type organic dyes are promising sensitizers owing to their strong electron-donating nature, molecular stability, and structural versatility. In this work, a systematic theoretical investigation is performed to elucidate the electronic and optical properties of a series of triphenylamine-derived organic dyes using density functional theory (DFT) and time-dependent density functional theory (TD-DFT).

Ground-state geometries are optimized at the B3LYP/6-31G* level to determine the highest occupied and lowest unoccupied molecular orbital (HOMO–LUMO) energies and their spatial distributions, which are crucial for effective charge transfer and energetic alignment in DSSCs. The analysis shows that structural modifications within the triphenylamine framework strongly affect orbital localization and energy gaps, thereby influencing intramolecular charge-transfer characteristics. TD-DFT calculations are employed to simulate optical absorption spectra, focusing on absorption intensity and spectral position in the visible region. The results demonstrate that extending π-conjugation and enhancing molecular planarity lead to red-shifted absorption bands with increased oscillator strengths, improving overlap with the solar spectrum and suggesting enhanced photocurrent generation.

Molecular electrostatic potential surface analysis further reveals the distribution of electron-rich and electron-deficient regions, providing insight into the role of functional groups in facilitating donor–acceptor interactions and charge redistribution. Overall, this study establishes clear structure–property–performance relationships and offers practical design guidelines for developing triphenylamine-based organic dyes with improved light-harvesting capability and potential DSSC efficiency.

Imidazo-pyrimidine derivatives are promising biologically relevant fluorophores due to their structural similarity with nucleic acids and pronounced photophysical response in biologically relevant microenvironments. These imidazo-pyrimidine derivatives present well-defined photophysical characteristics exhibiting fluorescence. In this work, we present a unified spectroscopic and computational investigation to elucidate the structure–function relationship and interaction dynamics of novel bio-imperative imidazo-pyrimidine derivatives with serum proteins and biomimicking micellar systems. Steady-state spectroscopic studies demonstrate strong binding interactions between one such derivative (SB1) and serum proteins, with a markedly higher affinity toward human serum albumin (HSA) compared to bovine serum albumin (BSA). These findings are corroborated by quenching and denaturation experiments as well as molecular docking analyses, which reveal preferential localization of the probe within a more hydrophobic binding pocket of HSA stabilized by π–π and alkyl interactions. This study extends the investigation to self-assembled systems, with another imidazo-pyrimidine derivative (BFIP), examining probe–micelle interactions in cationic CTAB and anionic SDS micelles using UV–visible spectroscopy, fluorescence measurements, dynamic light scattering, and molecular dynamics simulations. The surface charge of the micelles plays a decisive role in governing the interaction mechanism, with the probe forming a stable, hydrophobically driven complex within the CTAB micellar core, while remaining largely solvent-exposed and weakly associated in the pre-micellar regions of SDS. Density functional theory calculations encompassing FMO analysis, ESP mapping, and polarity statements further validate the structure–activity relationship of the probe and their propensity to interact with biomimicking systems. Collectively, this multiscale study provides comprehensive insights into how microenvironmental polarity, charge, and hydrophobicity modulate the binding and photophysical behaviour of imidazo-pyrimidine derivatives in diverse biomimetic systems, highlighting their potential as sensitive molecular probes for such systems, paving their applications in biomedical and pharmaceutical domains. This mainly highlights the novelty statement of the work.

The widespread occurrence of organic pollutants in water has prompted research into advanced purification strategies. 17α-ethinylestradiol (EE2), a synthetic estrogen widely used in contraceptives and hormone therapies, poses serious health risks, including prostate cancer and reduced sperm production. Heterogeneous photocatalysis, an advanced oxidation process, offers an efficient and sustainable solution for removing such contaminants.

The aim of this study was to investigate new (un)doped perovskite materials (YMnO₃, Sn-doped YMnO₃, and Co-doped YMnO₃) in the photocatalytic degradation of EE2, under different experimental conditions (catalyst type, initial pH) using simulated solar irradiation (SSI), as well as a reusability test.

The obtained results showed that the highest photocatalytic efficiency was achieved in the presence of the Co-doped YMnO_3, where 70% of EE2 was successfully removed after 120 min of SSI. The higher activity of the doped material compared to the pristine YMnO₃ was explained by the sponge-like morphology and the higher surface area. Since the highest removal efficiency was recognized for Co-doped YMnO_3, the experiments regarding the influence of initial pH on the photocatalytic activity were carried out in the presence of this newly prepared material. The obtained findings demonstrate that the highest removal efficiency was achieved without modifying the initial pH value of ~9. This behavior was explained by the favorable electrostatic interactions between YMO-Co and EE2. Moreover, photocatalyst reusability was assessed over three consecutive cycles in the presence of Co-doped YMnO₃, under SSI conditions, at pH 9 in ultrapure water. Only a slight decrease in photocatalytic efficiency (≤5%) was observed, indicating that the catalyst retained high activity even after three successive runs.

Acknowledgements

The authors thank the financial support of the Ministry of Science, Technological Development and Innovation of the Republic of Serbia (Grants No. ‪451-03-137/2025-03/ 200125 & 451-03-136/2025-03/200125).

Sulfur quantum dots (SQDs) have gained significant attention due to their tunable photoluminescence, high photostability, and low toxicity, offering an eco-friendly alternative to heavy-metal-based QDs. However, their application as independent sensory platforms is limited by the absence of intrinsic receptor groups.

This study presents a novel synthesis of SQDs using decasubstituted amide- and amino-functionalized pillar[5]arenes (P[5]As), addressing three key challenges. Firstly, the P[5]As act as effective surface passivation agents. The high density of electron-donating amino groups ensures their stable anchoring to the SQD surface, suppressing defect formation and aggregation. Secondly, these amino groups generate an alkaline medium necessary for sulfur dissolution and nanoparticle formation, eliminating the need for traditionally used NaOH in SQD synthesis, thereby reducing the number of reagents. Finally, P[5]As are capable of forming host–guest inclusion complexes, which imparts molecular recognition functionality to the SQDs. The sensory potential of the resulting nanomaterials was evaluated by studying their interaction with a series of antitumor drugs (tegafur, floxuridine, 5-fluorouracil, dacarbazine, and lomustine).

The following methods were applied to achieve the goal: NMR, IR, UV-vis, and fluorescence spectroscopy; MALDI-TOF mass spectrometry; elemental analysis; DLS; and TEM.

For the first time, SQDs were synthesized in the presence of P[5]As, serving as both surface passivation agents and alkaline medium providers. The resulting P[5]As-SQDs exhibit high-intensity blue fluorescence, average sizes of up to 10 nm, and a spherical morphology. UV-vis spectroscopy demonstrated the selective binding of 5-fluorouracil to the P[5]As-SQDs, confirming the key role of the macrocyclic ligand in recognition. Binding constants (lgK_as) determined by UV-vis and fluorescence titration were 2.42 and 2.06, respectively.

Thus, functionalization with amide- and amino-functionalized P[5]As provides a validated single-step strategy to create stable, recognition-capable SQDs. This approach opens promising avenues for developing SQD-based sensors, particularly for detecting specific bioactive molecules such as 5-fluorouracil.

Introduction
Aggregation-induced emission (AIE) dyes are a newly discovered class of molecules that have gained significant research attention. AIE dyes present enhanced emission intensity upon their aggregation with other molecules.
Methods
In this research, the sodium tetraphenylethylene 4,4′,4″,4‴-tetrasulfonate dye was electrostatically complexated with a series of poly(2-(diisopropylamino)ethyl methacrylate-co-2-(dimethylamino)ethyl methacrylate-co-oligoethylene glycol methyl ether methacrylate), P(DIPAEMA-co-DMAEMA-co-OEGMA) multiresponsive terpolymers. Different ratios of terpolymers to dye were used to investigate the aggregation-induced emission phenomenon and its dependence on dye concentration. All experiments were performed in aqueous solutions, while interaction with fetal bovine serum (FBS) proteins was also tested.
Results
Dynamic light scattering (DLS) measurements and Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy confirmed the successful complexation of dye with all terpolymers and their stability. Ultrasmall nanoparticles with a hydrodynamic radius of 5-7 nm were achieved across various formulations. As the polymers utilized are thermoresponsive, temperature-induced DLS measurements showcased the thermoresponsiveness of the polymer-dye nanosystems. Photophysical studies using ultraviolet-visible (UV-Vis) and fluorescence (FS) spectroscopy revealed the aggregation-induced emission phenomenon and enhanced emission intensity compared to that of the pure dye. All nanoformulations presented no significant interactions with FBS. Finally, the fluorescence emission intensity of nanoformulations in FBS medium was retained.
Conclusions
Polymer-dye thermoresponsive nanoformulations presenting the AIE phenomenon were fabricated via an easily scalable method. Further biocompatibility and in vivo tests can confirm the stealthiness and the ability of such nanoparticles to penetrate the blood-brain barrier. These promising ultrasmall nanosystems can find applications in photochemistry and bioimaging, where enhanced emission intensity is required.