Tetraphenylethylene (TPE) derivatives are key building blocks for solid-state fluorophores, offering tunable emission wavelengths and high quantum efficiencies. While it is nowadays well established, especially in recent literature, that rotation around the central CC bond dominates deactivation in solution and that its restriction in solid state results in aggregation-induced emission (AIE), the impact of substitution on TPE dynamics in solution remains largely unexplored. This is likely due to the challenge of efficiently separating E and Z isomers in most synthesized molecules. Here, we report the solution-phase photophysics of stereopure, extended TPE derivatives using both steady-state and femtosecond transient spectroscopies. Introducing triphenylamine (TPA) substituents generates distinct spectral differences between E and Z isomers, enabling modulation of the photostationary state and selective control of the isomeric equilibrium via irradiation wavelength. Notably, this photochromism is accompanied by a pronounced decrease in the photoisomerization quantum yield (Φiso) relative to non-extended TPEs, consistent with the "amino conjugation effect" previously observed in stilbene derivatives. Time-resolved spectroscopies provide mechanistic insight, revealing the substituent's influence on emissive and dark state lifetimes, as well as access to a conical intersection through rotation around the ethylenic bond, supported by TD-DFT calculations. These findings offer a new understanding of electron-donor substituted TPEs and their potential as tunable photochromic materials.

Aza-boron-dipyrromethenes (aza-BODIPYs) are established fluorescent imaging agents derived from aza-DIPY ligands coordinated to boron. While many modifications of the aza-DIPY core have optimized the photophysical properties, replacing boron with a metal ion remains underexplored. Here, we report four zirconium-based aza-DIPY complexes (aza-ZrDIPYs) and show that this substitution enables bimodal NIR-I fluorescence and photoacoustic imaging. The complexes were fully characterized and evaluated photophysiologically. The bromo derivative, aza-ZrDIPY-Br, displayed particularly favorable dual-mode properties. It showed low in vitro cytotoxicity and an effective uptake in two human cell lines. In mice bearing subcutaneous U87-MG glioblastoma tumors, intravenous or peritumoral administration led to passive tumor accumulation, with tumor-to-background ratios of up to 5 (photoacoustic) and 2 (optical). These results highlight aza-ZrDIPY-Br as a promising bimodal probe for tumor imaging, with future work aimed at improving specificity through active targeting.

Solid-state fluorophores exhibiting high emission efficiency in the far-red and near-infrared (NIR) regions are a highly sought-after class of materials for applications ranging from optoelectronics to bioimaging contrast agents. Building on recently reported tetraphenylethylene (TPE) analogues bearing two triazole groups on the central ethylene bond, we developed a two-step synthetic strategy toward NIR solid-state emitters involving (i) quaternization of the triazole units and (ii) anion exchange at the resulting triazolium moieties. Detailed spectroscopic investigations in solution first allowed us to elucidate the mechanisms governing their luminescence. The same compounds were then found to display NIR aggregation-induced emission (AIE) together with large two-photon absorption cross-sections. This enables the formation of bright aqueous nanosuspensions displaying efficient one- and two-photon excited emission, which were successfully employed as contrast agents for in cellulo and in vivo bioimaging.

Aza-boron-dipyrromethenes (aza-BODIPYs) are established fluorescent imaging agents derived from aza-DIPY ligands coordinated to boron. While many modifications of the aza-DIPY core have optimized the photophysical properties, replacing boron with a metal ion remains underexplored. Here, we report four zirconium-based aza-DIPY complexes (aza-ZrDIPYs) and show that this substitution enables bimodal NIR-I fluorescence and photoacoustic imaging. The complexes were fully characterized and evaluated photophysiologically. The bromo derivative, aza-ZrDIPY-Br, displayed particularly favorable dual-mode properties. It showed low in vitro cytotoxicity and an effective uptake in two human cell lines. In mice bearing subcutaneous U87-MG glioblastoma tumors, intravenous or peritumoral administration led to passive tumor accumulation, with tumor-to-background ratios of up to 5 (photoacoustic) and 2 (optical). These results highlight aza-ZrDIPY-Br as a promising bimodal probe for tumor imaging, with future work aimed at improving specificity through active targeting.

Fluorinated porphyrins have attracted considerable attention in PDT, sensing and catalysis. Guided by demands for functional porphyrins with tunable electronic properties, high photostability, and controlled supramolecular organization, we report a synthetic approach to meso-tetrakis[4-(diethoxyphosphoryl)-2,3,5,6-tetrafluorophenyl]porphyrin (H2TF4PPP), which combines the advantages of diethyl phosphonate and fluorine substituents within a highly symmetrical porphyrin molecule. X-ray diffraction analysis of H2TF4PPP reveals that diethyl phosphonates govern the crystal packing, while the macrocycles avoid π-π stacking. Zn(II) and Pd(II) complexes with H2TF4PPP were prepared in high yields. In contrast, insertion of In(III) ions exhibiting strong Lewis acidity was accompanied by partial hydrolysis of phosphonate groups. H2TF4PPP and its Zn(II) and Pd(II) complexes efficiently generate singlet oxygen displaying a good solubility in various organic solvents. The noble-metal-free porphyrin H2TF4PPP surpasses Pd(II) complex of non-fluorinated analogue (PdTPPP) in photocatalytic performance, enabling sustainable oxidation of sulfides to sulfoxides with oxygen. H2TF4PPP forms a stable Langmuir monolayer which can be transferred onto solid substrates, yielding dense single-layer films containing fiber-shaped nanoparticles. The films thus obtained are emissive and their photostability surpasses that of H2TPPP films. Water-soluble porphyrins H2TF4PPP-A and PdTF4PPP-A with phosphonic acid groups were also prepared and briefly investigated.

Photochemistry has revolutionized the chemical industry by introducing sustainable and energy‐efficient processes that are vital for the manufacture of advanced materials which align with Industry 4.0 standards. Among photochemical techniques, photopolymerization stands out as a rapid, controlled, and eco‐friendly approach, making it particularly suitable for applications like 3D printing. This research in two‐photon‐induced photopolymerization for 3D microfabrication led to groundbreaking performance, thanks to the use of custom π‐ extended molecular architectures as photoinitiators. Building on these results, a photoactivable initiation system for photoinduced‐atom transfer radical polymerization (photoATRP) is now reported using a similar π ‐extended photoinitiator. Through comprehensive optimization, we successfully created a functional multicomponent photoinitiating system, with its detailed mechanism thoroughly established in solution. By covalently attaching alkyl halides to glass surfaces, we were able to implement the surface‐induced photo‐ATRP technique to create customized brush polymer architectures. This work not only advances the understanding of photoATRP mechanisms but also introduces new strategies for functional surface engineering, with potential applications in two‐photon‐induced surface modification of 3D/4D structures via photoATRP.

Molecules exhibiting photo-switching behavior are essential for the development of various photonic and optoelectronic devices. In this study, we report the synthesis of five novel donor-pi-acceptor organic dyes, in which a stilbene moiety serves as a pi-linker between the electron-donating and electron-withdrawing units. To address the challenge of developing photo-switchable molecules responsive to visible light, we performed fundamental optical characterization in both solution and solid state. The photoisomerization capability was confirmed for all compounds through real-time absorption measurements, enabling the calculation of E -> Z isomerization kinetics. The presence of both isomeric forms was further validated by 1H NMR spectroscopy. These experimental findings were supported by quantum chemical calculations, which identified the most stable conformers and accurately predicted their spectral properties. Moreover, pump-probe experiments demonstrated that irradiation with linearly polarized light efficiently triggers photo-induced birefringence in dye-doped polymer systems, with a notable "memory effect" observed for all studied compounds. Remarkably, the dyes are highly sensitive to light, and the birefringence saturation can be achieved at light intensities comparable to natural daylight, highlighting their broad potential application in optoelectronic devices.

While nowadays ubiquitous in a variety of optoelectronic applications, fluorophores displaying aggregation induced emission (AIE) and in particular those constructed around the tetraphenylethylene (TPE) core suffer severe limitations. In particular, it has been reported in many instances that stereoconfiguration around the central double bond may severely impact the solid-state luminescence properties (maximal emission wavelength and fluorescence quantum yield). Stereoselective synthesis of extended TPE cores remains challenging, and separation of diastereoisomer mixtures is generally tedious. In this paper, we introduce ditriazolostilbene moities (DTS) as an alternative to TPE. DTS offers two significant advantages over its TPE counterpart: firstly, a fully stereoselective synthesis of the (E)-isomer, and secondly, the use of a copper-catalyzed azide-alkyne cycloaddition (CuAAc) reaction in the final step, which simplifies access to novel derivatives. We illustrate the benefits of this approach using stereopure and (E) and (Z)-aggregates, powders and crystals of the molecule and show that emission properties are considerably dependent on their stereoconfiguration.

The development of new fluorophores emitting in the near-infrared (NIR-I and/or NIR-II) region is currently a major focus of research in fields such as optics, energy, and medical imaging. Among these fluorophores, aza-BODIPYs have emerged as a particularly promising family. However, the challenge lies in determining which structural modifications are necessary to achieve the desired photophysical properties. This study aims to elucidate the impact of electron-donating groups, specifically N,N-dialkylamino groups, on these properties, depending on their number and position. A series of 14 aza-BODIPYs, without and with one to four N,N-dimethylamino groups, was synthesized, chemically characterized (NMR, HRMS, X-ray diffraction), and photochemically analyzed. Their photophysical properties were compared, and molecular modeling ((TD)-DFT) was performed to rationalize these properties. Preliminary tests in biological media were also conducted.

The development of aggregation-induced emission (AIE)-exhibiting compounds heavily relies on our evolving comprehension of their behavior at interfaces, an understanding that still remains notably limited. In this study, we explored the preparation of two-dimensional (2D) sensing films from 2,3-diphenylquinoxaline-based diazapolyoxa- and polyazamacrocycles displaying AIE via the Langmuir-Blodgett (LB) technique. This systematic investigation highlights the key role of the heteroatom-containing tether of 2,3-diphenylquinoxalines in the successful fabrication of Langmuir layers at the air-water interface and the transfer of AIE-emitting supramolecular aggregates onto solid supports. Using both diazapolyoxa- and polyazamacrocycles, we prepared AIE-exhibiting monolayer films containing emissive supramolecular aggregates on silica, mica, and quartz glass and characterized them using ultraviolet-visible (UV-vis) and photoluminescence (PL) spectroscopies, atomic force microscopy (AFM) imaging, and fluorescence microscopy. We also obtained multilayer AIE-emitting films through the LB technique, albeit with increased complexity. Remarkably, by employing the smallest macrocycle N2C3Q, we successfully prepared LB films suitable for the visual detection of acidic vapors. This sensing material, which contains a much lesser amount of organic dye compared with traditional drop-cast films, can be regenerated and utilized for real-life sample analysis, such as monitoring the presence of ammonia in the air and the freshness of meat.

Quinoxaline-based AIEgens with flexible receptor units were prepared using macrocyclization through the Pd-catalyzed amination reaction. They were then used to prepare AIE-exhibiting test strips for measuring acidity in vapors and aqueous media.

The emission quenching observed in devices utilizing luminescent materials such as solid thin films is a prevalent issue. Consequently, searching for new organic luminescent compounds exhibiting aggregation-induced emission (AIE) behavior and characterized by relatively simple and cost-effective synthesis is of crucial interest among applications from optoelectronics and organic lasing branches. Herein, we report the optical properties of three furan-based carbazole-substituted compounds, namely, tBuCBzSO2Ph, tBuCBzSPh, and tBuCbzTCF, exhibiting the aforementioned AIE phenomenon. The optical properties of dyes were determined in classical spectroscopic experiments supported by quantum-chemical calculations. The thermal investigations and electrochemical properties of dyes were performed to verify their usefulness in the construction of organic light-emitting diodes (OLEDs). In pursuit of this objective, OLEDs with a different design were fabricated, and their performance was subject to evaluation. In more detail, the different design strategies relying on the utilization of neat-dye films, as well as the preparation of dye-doped poly(9-vinylcarbazole):2-(4-tert-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (PVK:PBD) matrices were examined. The analysis that was conducted indicated the superior potential of tBuCBzSPh for optoelectronic applications. Notably, the positive impact of the AIE effect on the emission of the OLEDs and the ability to establish the lasing phenomenon in asymmetric, poly(methyl methacrylate) (PMMA)-doped polymeric slab waveguides were verified. The study showed that the combination of the strong intramolecular charge transfer (ICT) effect with dye aggregation enables the tuning of the emission of the OLED toward the first biological window, making examined dyes promising candidates for biomedical purposes. The same optical region can be attained for laser emission at relatively low pumping conditions, reaching as low as 7.3 kW of optical power for the tBuCBzSO2Ph compound.

Organic molecules have been intensively studied during the last few decades because of their photonics and biological applications. In this material class, the fluorene molecules present outstanding optical features, for example, high values of two-photon absorption (2PA) cross-sections, visible transparency, and high fluorescence quantum yield. Also, it is possible to improve the nonlinear optical response by modifying the fluorene molecular structure. In this context, herein, we have synthesized V and Y-shaped branching oligofluorenes containing two and three fluorene moieties in each branch. Such a molecular strategy may exponentially enhance the nonlinear optical response due to the coherent coupling among the molecular arms. Thus, we combined the use of femtosecond Z-scan spectroscopy and white light transient absorption spectroscopy (TAS) to understand the molecular structure and 2PA property relationship of branching oligofluorenes. The results show that there is a universal relationship between the 2PA cross-section and the effective π-electron number (Neff) given by σ2PA(GM) = (079 ± 0.03)Neff2, which is independent of the molecular shape (linear, V or Y-shaped). Therefore, the intramolecular charge transfer responsible for the cooperative effect among the branches does not occur. This statement is corroborated by the results of the femtosecond TAS technique.

This study presents the synthesis, the spectroscopic and electrochemical properties of new bis- and tetra-substituted azaboron-dipyrromethene (aza-BODIPY) dyes substituted by different electron donating groups connected to the aza-BODIPY core through a thiophene unit. In line with theoretical calculations, experimental measurements point out the positive impact of the thiophene group that behave as a secondary donor group leading to an enhancement of the intramolecular charge transfer process in comparison to previously reported aza-BODIPY dyes. This heterocycle has also been found to tune the oxidative potential and to stabilize the electro-generated species.

The aggregation of a TCF-based dye exhibiting AIE is used to enhance the random lasing emission intensity up to 170 times. The transition from small aggregates to crystals forms a second lasing band and is responsible for 2-photon pumped lasing.

Tetraphenylethylene (TPE) derivatives have been a key building block in the development of solid-state fluorophores with tunable emission wavelength and large quantum efficiencies. Recent literature has brought an array of evidence that rotation around the central C=C bond constitutes main route of deexcitation in solution, and that its restriction in solid-state leads to aggregation-induced emission (AIE) in this family of derivatives. However, the influence of substitution on the dynamics of TPEs in solution has so far received little attention, probably because of the difficulty in efficiently separating (E) and (Z) isomers. Here we report the photophysical properties in solution of extended stereopure TPE derivatives. The introduction of triphenylamine (TPA) substituent results in differences in the spectral properties between the (E) and (Z) isomers, thereby allowing modulation of the photostationary state (PSS) and thus switching in the equilibrium between these two forms depending on the irradiation wavelength. Importantly, we show that this photochromism is observed with a very marked decrease in the photoisomerization quantum yields (Φiso) of TPE-TPA, compared to non-extended TPE derivatives, which we attribute to the so called “amino conjugation effect” already reported for several stilbene derivatives. As a generalization of this mechanism, we show that TPA substitution provides similar effect on other stilbenoid derivatives. These results provide important new insight into the photophysics of electron donor substituted TPEs, and their possible use as photochromic materials.

Amino-heptamethines are highly conjugated cationic dyes featuring electronic absorption in the red region and strong near-infrared (NIR) fluorescence. Unlike their parent chloro-heptamethine cyanines, the substitution of the central position of their polymethine skeleton with an amine confers them a high Stokes shift. This work reports the synthesis of amino-heptamethines and the investigation of their optical properties, including two photon absorption in the NIR and short-wave infrared (SWIR) ranges, which has been overlooked for such chromophores so far. Their structures were tailored, introducing selected substitutuents on the indolenine moieties to modulate their hydrophobic/hydrophilic balance and investigate their potential as NIR-to-NIR two photon probes for the bio-imaging of living cells.

Tunability is an important aspect of lasers. Nowadays there are many possible ways to achieve this advantageous property; however, dynamic tuning is limited. Red to InfraRed emissive dyes allow a direct visualization of molecular interactions, through deep tissue penetration, along with minimal tissue damage. In our studies we use simple systems based on a single dye-doped polymeric thin films for distributed feedback (DFB) and random lasing (RL) investigations. As active compounds we have applyed novel push-pull luminescent diphenylaminofluorene and tiophene derivatives, with different acceptor groups. Integration of such luminescent dyes with transparent polymeric medium allows fabricating real-time lasing tunability in the visible region and first biological window (650-950 nm). The observed spectral tuning of 150 nm is a groundbreaking value obtained in a single-dye system. Also Excited-State Intramolecular Proton Transfer (ESIPT) compounds, have attracted our considerable attention, due to their unique optical properties. In this contribution we show a novel bis-trimethylsilyl substituted 2-(2’hydroxyphenyl)benzothiazole (HBT) derivatives functionalized with a trifluoromethyl - a strong electron-withdrawing group. Such structure enabled real-time red-green-blue (RGB) switching of emission, both in solution and solid-state, providing white laser light emission. We show strong dependence on environment polarity, as well as Aggregation-Induced Emission Enhancement (AIEE) properties, and successful implementation of ESIPT molecules in DFB lasing, both in solution and solid-state.

We determine the two-photon absorption (2PA) cross section spectra branched polyfluorenes distinguished by the number of fluorenes and chemical architecture. Moreover, the optical properties were determined in function of the effective electrons number of each compound.