Abstract Achieving long-lived luminescence in complexes of earth-abundant metals remains challenging because excited states in first-row transition-metal systems typically deactivate rapidly under ambient conditions. Strategies capable of prolonging emission lifetimes in such compounds are therefore of considerable interest. Here we show that iron(III) complexes incorporating pyrene-functionalized ligands display luminescence in fluid solution at room temperature with lifetimes up to 6.5 ns. Spectroscopic analysis indicates that excited-state equilibration occurs through reversible intramolecular electron transfer from the pyrene unit to the iron centre, generating a charge-separated state. Although the ligand-to-metal charge-transfer state can also undergo reversible energy transfer to nearby pyrene triplet states, intramolecular electron transfer dominates, leading to the formation of a pyrene + -iron(II) charge-separated state that acts as a long-lived excited-state reservoir. Equilibration involving this state produces biphasic emission from the iron centre. These findings identify reversible intercomponent electron transfer as a strategy for achieving prolonged luminescence lifetimes in complexes of earth-abundant metals.

Silicon plays a crucial role in modern microelectronics and telecommunications. Recent advancements in nanotechnology have expanded its applications, particularly in photonics. Quantum confinement effects in silicon nanostructures, such as nanocrystals and nanowires (Si NWs), enable light emission in the visible-to-near-infrared (IR) spectrum at room temperature. Among these, Si NWs are particularly promising as they are compatible with existing microelectronic fabrication processes. Given the importance of near-IR light sources for telecommunications, research has focused on enhancing the silicon-based emission in this spectral range. This study presents the development of a hybrid light-harvesting antenna composed of quantum-confined Si NWs and Ru-(II)/Os-(II)-based dendrons. By leveraging energy transfer processes, these hybrid systems achieve near-IR emission at ∼920 nm with a remarkable 99.5% efficiency, as confirmed by lifetime measurements. The dye was anchored to the Si NWs via a carboxyl-functionalized bipyridine ligand, enhancing the stability of these hybrid systems. The demonstrated Si NWs/RuOs2 hybrid antenna offers significant advantages, including high energy transfer efficiency, stability, and compatibility with cost-effective silicon technology making these structures promising candidate for photonic applications.

Bacterial infections pose a significant health threat, worsened by the growing issue of antibiotic resistance and biofilm formation. Phototherapies, particularly photodynamic therapy (PDT), offer promising non-invasive alternatives due to their high efficacy and minimal side effects. These therapies utilize photosensitizers (PSs), which, when activated by light, generate reactive oxygen species (ROS) that lead to bacterial cell death. Recent advancements have focused on enhancing PDT by integrating PSs with nanomaterials. Halloysite nanotubes (HNTs), a natural clay mineral, are of particular interest due to their unique properties, including intrinsic antibacterial activity and the ability to integrate into bacterial biofilms. By combining HNTs with photosensitizers, we aimed to improve treatment efficacy. In this study, we synthesized a novel glucosyl OPE derivative and covalently attached it to HNTs, forming the composite HNTs@Glu-OPE. This system was thoroughly characterized, and its ROS generation capabilities were tested under 365 nm light irradiation using uric acid as a probe. Loaded with vancomycin, HNTs@Glu-OPE represents a multifunctional approach to PDT, enhancing both the delivery and effectiveness of therapeutic agents against resistant bacterial strains.

The osmium(II) polypyridyl complex [Os(tpy)(pydppn)]2+ (tpy = 2,2′:6′,2″-terpyridine; pydppn = 3-(pyrid-2′-yl)-4,5,9,16-tetraaza-dibenzo[a,c]naphthacene) was synthesized and characterized to evaluate the effect of an extended planar π-system on photophysical properties and DNA interactions. This complex represents the π-expanded analog of the previously studied [Os(tpy)(pydppz)]2+ system. Electrochemical studies revealed a reversible Os(II)/Os(III) oxidation at +0.99 V vs. SCE and five ligand-centered reductions, generally less negative than those of the smaller pydppz analog, consistent with enhanced electron-accepting ability. In acetonitrile, the complex exhibits UV absorption bands at 328 and 473 nm and near-infrared emission at 840 nm, assigned to a long-lived 3MLCT state (τ = 110 ns, Φ = 0.02). Upon titration with calf-thymus DNA, [Os(tpy)(pydppn)]2+ shows a pronounced light-switch effect, hypochromism, red-shifted MLCT bands, induced circular dichroism, and an increase in DNA melting temperature (ΔTm = 8.9 ± 0.5 °C), consistent with intercalative binding. Viscometric titrations further support intercalation, with a binding constant KB ≈ 1.2 × 106 M−1. Transient absorption spectroscopy indicates that DNA binding prolongs the excited-state lifetime and modifies vibrational relaxation pathways. These results highlight how π-system extension in Os(II) complexes modulates photophysical behavior and DNA affinity, offering insights for the rational design of NIR-emitting, DNA-targeted luminescent probes and potential phototherapeutic agents.

The synergistic combination of the ruthenium-based tetranuclear dendrimer photosensitizer with the highly efficient water oxidation catalyst Ru(bda)(pic)2 enables effective water oxidation under low-energy light irradiation in phosphate buffer 20 mM/acetonitrile 3% (pH 7). This study demonstrates that the integrated system can produce a significant amount of oxygen using visible light at wavelengths greater than 650 nm (up to 160 nmol), achieving quite good turnover number (3.5 × 10−3), high quantum yields (0.23) and enhanced stability. These results highlight the potential of this approach to efficiently drive solar water splitting for fuel production, even with low-energy illumination, thereby advancing the development of sustainable photochemical systems for solar energy conversion.

Photodynamic therapy (PDT) is a minimally invasive technique—used for the local eradication of neoplastic cells—that exploits the interaction of light, oxygen, and a photo-responsive drug called photosensitizer (PS) for the local generation of lethal ROS. Push-pull chromophores, that bear electron donor (D) and acceptor (A) groups linked through a π-electron bridge, are characterized by a non-homogeneous charge distribution in their excited state, with charge transfer from one extremity of the chain to the other one (Internal Charge Transfer—ICT). This phenomenon has a direct impact on the photophysical features of the push-pull compounds, as the bathochromic shift of the emission maxima and intersystem crossing (ISC) of the excited state are directly connected with the production of reactive oxygen species (ROS). In continuing our research regarding the synthesis and use of oligophenylene ethynylenes (OPEs) in PDT, two new push-pull glycosyl OPE-NOF and OPE-ONF—featuring electron-donor N,N-dimethylamino (N) and dimetoxyaryl (O) and acceptor tetrafluoroaryl (F) moieties on the OPE chain—have been efficiently prepared. The interchanged position of the D groups onto the conjugated skeleton was aimed to tune and optimize the push-pull effect, while the introduction of glucoside terminations was directed to give biocompatibility and bioaffinity to the chromophores. OPE-NOF, OPE-ONF, and the synthetic intermediates were fully characterized, and their photophysical properties were investigated by using UV-Vis absorption and emission spectroscopy. OPE-NOF showed a strong charge-transfer character and high PDT effect on HeLa cancer cells when irradiated with non-harmful blue light, causing massive cancer cell death.

As a development of our research on biocompatible glycoconjugate probes and specifically multi-chromophoric systems, herein, we report the synthesis and early bactericidal tests of two luminescent glycoconjugates whose basic structure is characterized by two boron dipyrromethene difluoride (BODIPY) moieties and three galactoside rings mounted on an oligophenylene ethynylene (OPE) skeleton. BODIPY fluorophores have found widespread application in many branches of biology in the last few decades. In particular, molecular platforms showing two different BODIPY groups have unique photophysical behavior useful in fluorescence imaging. Construction of the complex architecture of the new probes is accomplished through a convergent route that exploits a series of copper-free Heck–Cassar–Sonogashira cross-couplings. The great emergency due to the proliferation of bacterial infections, in conjunction with growing antibiotic resistance, requires the production of new multifunctional drugs and efficient methods for their targeted delivery to control bacteria-associated diseases. Preliminary studies of the glycoconjugate properties as antibacterial agents against representatives of Gram-negative (P. aeruginosa) and Gram-positive (S. aureus) pathogens, which are associated with chronic infections, indicated significant bactericidal activity ascribable to their structural features.

A luminescent calix[5]arene with a covalently linked dansyl chromophore substituent has been successfully used, both in solution and in the gas phase (ESI-MS), for the recognition of biogenic amines that contain linear alkylammonium structural unit. Binding constant values, determined by fluorescence spectroscopy, revealed a greater affinity for cadaverine, spermidine, and L-lysine, in which the terminal ammonium group allows for additional stabilizing interactions with the dansyl moiety.

AbstractThree new chromophores based on difluoroborondipyrromethene dyes (Bodipy‐1, Bodipy‐2, and Bodipy‐3) are used as precursors to prepare luminescent solar concentrators (LSC) based on poly‐acrylate, following a thermally activated polymerization involving lauryl methacrylate as monomer, ethyl glycol dimethacrylate as cross‐linking agent, and lauroyl peroxide as initiator. The new dyes exhibit typical BODIPY absorption and emission properties in dichloromethane fluid solution, assigned to the lower‐lying singlet π–π∗ level, which in the case of Bodipy‐2 and Bodipy‐3, both containing diamino‐substituted styryl subunits in their structure, has a strong charge transfer contribution. The LSCs obtained starting from each of the three Bodipys are interfaced to silicon photovoltaic (PV) cells, and the PV light‐to‐energy conversion efficiencies ηopt for the three systems are calculated. The results yield ηopt of 4.53% for LSC‐Bodipy‐1, 5.26% for LSC‐Bodipy‐2, and 8.23% for LSC‐Bodipy‐3. The optical efficiency for LSC‐Bodipy‐3 is a remarkable value among the LSC based on organic dyes.

Abstract Iron(III) complexes with long-lived luminescence in fluid solution at room temperature (up to 6.5 ns, significantly longer than benchmark compounds) have been prepared, by taking advantage of the excited-state equilibration approach, for the first time applied to earth-abundant, iron(III) compounds. Pyrene subunits have been covalently-linked by methylene linkage to [Fe(phtmeimb)2]+ (1; phtmeimb is {phenyl[tris(3-methylimidazol-1-ylidene)]borate}−), so obtaining complex 3, and have been used to synthesize [Fe(pytmeimb)2]+ (2; pytmeimb is {2-pyrene[tris(3-methylimidazol-1-ylidene)]borate}−). In 2 and 3, the ligand-to-metal charge transfer (2LMCT) state decays by energy transfer to closely-lying p-p* pyrene triplets. Equilibrated states are so formed, resulting in 2LMCT emission from the Fe(III) subunit, in which pyrene triplets serve as long-lived excited-state reservoirs. In 2, symmetry-breaking charge separation in dilute fluid solution at room temperature also occurs.

This study presents a breakthrough in the detection of polycyclic aromatic hydrocarbons (PAHs), particularly pyrene, recognized as persistent organic pollutants (POPs) with significant bioaccumulation and cancer risks. An optical sensor based on silicon nanowires (Si NWs) is presented, leveraging an approach that combines silane treatment and functionalization with 6-monodeoxy-6-monoamino-beta-cyclodextrin. This method innovatively utilizes the quantum-confinement properties of Si NWs and noncovalent interactions for molecular recognition, enabling highly sensitive pyrene detection in water without prior treatment. The anchoring of beta-CD quenches the optical emission of quantum-confined carriers in Si NWs, whereas the inclusion of pyrene in the receptor cavity restores the luminescence of the system, producing a disruption of luminescence quenching induced by the analyte. The sensor achieves a limit of detection (LoD) of 2 x 10(-4) ppb and a limit of quantification (LoQ) of 0.01 ppb, covering a dynamic range over 6 orders of magnitude. This advancement integrates nanophotonics and supramolecular chemistry, marking a significant leap in environmental monitoring methodologies.

The supramolecular polymerization of a bis-pillar[5]arene dicarboxylic acid monomer (H) in the presence of a mixture of complementary bis-guests 1,12-dodecanediyl-bis-1,1 '-1H-imidazole (G1) and bis-N,N'-(6-(1H-imidazole)decyl)-perylene bisimide (G2), produces an AA/BB-type supramolecular copolymer H/G1/G2 that retains the properties of the parent bi-component systems, that is, H/G1 solubility and H/G2 photoresponsiveness. The supramolecular copolymer showed stimuli-responsiveness, reacting to the presence of the cancer marker, spermine (S), by disassemblying and releasing G2. Once released, the perylene bisimide monomer (quenched in the copolymer by host-to-guest electron transfer), showed a remarkable increase of emission intensity. ESI-MS data are fully consistent with the formation of the H/G1/G2 copolymer, and AFM investigations on films cast from H/G1/G2 and H/G1/G2 + S solutions demonstrated that the supramolecular copolymer sensing abilities are retained also in the solid state. A supramolecular copolymer, composed of a bis-pillar[5]arene diacid and complementary alkylidene- and perylene-bisimide-bis-imidazole comonomers, acts as an OFF/ON luminescent sensor for spermine.

We report the absorption spectra and photophysical properties of homo and hetero-aggregate assemblies of a strongly emissive N-annulated perylene dye (P) and of a dyad made of P and a methyl viologen derivative (P-MV), in ethanol-water solutions. In homo-aggregate assemblies of P, the pi-pi* fluorescence of the isolated chromophore is replaced by excimer emission at lower energy, with a lifetime of 900 ps, due to excimer formation from the initially prepared excitons. In homo-aggregate assemblies of P-MV, photoinduced charge separation, with formation of P+-MV- species, occurs in 3 ps with a charge recombination of 20 ps. In hetero-aggregate P/P-MV systems, the light energy absorbed by the P components delocalizes over various P subunits, and when a P-MV unit is reached, charge separation occurs; however, excimer emission is present for P/P-MV ratio larger than 3 : 1, indicating that delocalized excitons within the hetero-aggregate systems extend over a limited number of P chromophores.

Two new supramolecular photocatalysts containing Ru(II) polypyridine units as light-harvesting photosensitizers and Re(I) polypyridine subunits as catalytic centers have been prepared. The new species, RuRe2A and Ru2ReA, contain catalytic Re(I) subunits coordinated by the preformed CO2TEOA adduct (known to be the effective catalytic subunits; TEOA is triethanolamine) and exhibit quite efficient and selective photoreduction of CO2 to CO, with outstanding TONs of 2368 and 2695 and a selectivity of 99.9% and 98.9%, respectively. Such photocatalytic properties are significantly improved with respect to those of previously studied RuRe2 and Ru2Re parent compounds, containing chloride ligands instead of the CO2TEOA adduct. Comparison between photocatalytic performance of the new species and their parent compounds allows to investigate the effect of the CO2TEOA insertion process as well as the eventual effect of the presence of chloride ions in solution on the photocatalytic processes. The improved photocatalytic properties of RuRe2A and Ru2ReA compared with their parent species are attributed to a combined effect of different distribution of the one-electron reduced form of the supramolecular photocatalysts on the Ru-subunit(s) (leading to decreased CO formation due to a poisoning ligand loss process) and on the Re-subunit(s) and to the presence of chloride ions in solution for RuRe2 and Ru2Re, which could interfere with the CO2TEOA adduct formation, a needed requisite for CO forming catalysis. These results strongly indicate the utility of preparing supramolecular photocatalysts containing preformed adducts.

The developments made towards increasingly photoactive copper(I) complexes has led to their use in many applications involving light, in particular light emission or photocatalytic activities. Herein, we describe an unprecedented in-depth study of the photophysical properties of two of the most used copper(I) photosensitizers, [Cu(bcp)(Xantphos)]+ and [Cu(bcp)(DPEphos)]+ (bcp = bathocuproine, Xantphos = 4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene, DPEphos = Bis[(2-diphenylphosphino)phenyl]ether). This study combines traditional spectroscopic techniques with state-of-the-art femtosecond time-resolved transient absorption and fluorescence up-conversion spectroscopy and is further supported by quantum-chemical calculations. This combined analysis hints at the presence of a low-lying ligand-centered dark triplet state which plays a crucial role by acting as a reservoir for the excited hetereloptic copper(I) complexes.

[This corrects the article DOI: 10.1021/acscatal.3c01407.].

The enormous increase in the consumption of personal protection equipment, such as facemasks, mainly related to the COVID-19 pandemic, has shone light on the metric tons of plastic waste that are released into the oceans, with dramatic environmental concerns. Here, we report on the preparation of carbon dots (C-dots) following an environmentally friendly synthetic strategy using surgical facemasks as the starting material. Such C-dots are highly photostable and luminescent and were used to prepare luminescent solar concentrators exhibiting - once connected to silicon photovoltaic panels - a remarkable solar-to-energy conversion of 6.1%. Our results could suggest a way both to alleviate the serious environmental problem and to produce low-cost materials for solar energy conversion purposes. Facemask-derived C-dots were used to prepare luminescent solar concentrators exhibiting a remarkable solar-to-energy conversion of 6.1%.