The development of phosphorescent probes for in vitro and in vivo bioimaging

Room Temperature Phosphorescence in Crystalline Iodinated Eumelanin Monomer

We report the room temperature phosphorescence upon iodination on a crystalline eumelanin monomer with shielded hydroxyl moieties, ethyl 5,6-dimethoxyindole-2-carboxylate (DMICE). Ultrafast intersystem crossing (ISC) is observed in the iodinated (IDMICE) as well as brominated (BDMICE) analogues of the eumelanin monomer derivative in solution. The triplet quantum yields (φT) and intersystem crossing rates (kISC) of the halogenated eumelanin derivatives areφ T B D M I C E ${{\phi{} }_{T}^{BDMICE}}$ =25.4±1.1 %;k I S C B D M I C E ${{k}_{ISC}^{BDMICE}}$ =1.95×109 s-1 andφ T I D M I C E ${{\phi{} }_{T}^{IDMICE}}$ =59.1±1.6 %;k I S C I D M I C E = ${{k}_{ISC}^{IDMICE}=}$ 1.36×1010 s-1, as monitored using transient absorption spectroscopy. Theoretical calculations based on nuclear ensemble method reveal that computed kISC and spin-orbit coupling matrix elements for eumelanin derivatives are larger for IDMICE relative to BDMICE. The halogen and π-π interactions, with distinct excitonic coupling and higher ISC rate promote phosphorescence in IDMICE molecular crystals. Accessing triplet excited states and resultant photoluminescence through structural modification of eumelanin scaffolds paves way for exploring the versatility of eumelanin-inspired molecules as bio-functional materials.

Iridium-based Polymeric Multifunctional Imaging Tools for Biochemistry

Herein, we report the development of a macromolecular multifunctional imaging tool for biological investigations, which is comprised of an N-(2-hydroxypropyl)methacrylamide backbone, iridium-based luminescent probe, glutamate carboxypeptidase II (GCPII) targeting ligand, and biotin affinity tag. The iridium luminophore is a tris-cyclometalated complex based on [Ir(ppy)3] with one of its 2-phenylpyridine ligands functionalized to allow conjugation. Synthesized macromolecular probes differed in the structure of the polymer and content of the iridium complex. The applicability of the developed imaging tools has been tested in flow cytometry (FACS) based assay, laser confocal microscopy, and fluorescence lifetime imaging microscopy (FLIM). The FACS analysis has shown that the targeted iBodies containing the iridium luminophore exhibit selective labelling of GCPII expressing cells. This observation was also confirmed in the imaging experiments with laser confocal microscopy. The FLIM experiment has shown that the iBodies with the iridium label exhibit a lifetime greater than 100 ns, which distinguishes them from typically used systems labelled with organic fluorophores exhibiting short fluorescence lifetimes. The results of this investigation indicate that the system exhibits interesting properties, which supports the development of additional biological tools utilizing the key components (iridium complexes, iBody concept), primarily focusing on the longer lifetime of the iridium emitter.

Enhancing the tumor penetration of multiarm polymers by collagenase modification

Tumor penetration is a critical determinant of the therapy efficacy of nanomedicines. However, the dense extracellular matrix (ECM) in tumors significantly hampers the deep penetration of nanomedicines, resulting in large drug-untouchable areas and unsatisfactory therapy efficacy. Herein, we synthesized a third-generation PAMAM-cored multiarm copolymer and modified the polymer with collagenase to enhance its tumor penetration. Each arm of the copolymer was a diblock copolymer of poly(glutamic acid)-b-poly(carboxybetaine), in which the polyglutamic acid block with abundant side groups was used to link the anticancer agent doxorubicin through the pH-sensitive acylhydrazone linkage, and the zwitterionic poly(carboxybetaine) block provided desired water solubility and anti-biofouling capability. The collagenase was conjugated to the ends of the arms via the thiol-maleimide reaction. We demonstrated that the polymer-bound collagenase could effectively catalyze the degradation of the collagen in the tumor ECM, and consequently augmented the tumor penetration and antitumor efficacy of the drug-loaded polymers.

Phosphorescent Cyclometalated Palladium(II) and Platinum(II) Complexes Derived from Diaminocarbene Precursors

Metal-mediated self-assembly of isocyanides and methyl 4-aminopyrimidine-5-carboxylate leads to luminescent PdII and PtII complexes featuring C,N-cyclometalated acyclic diaminocarbene (ADC) ligands. The solid-state luminescent properties of these diaminocarbene derivatives are attributed to their triplet-state metal/metal-to-ligand charge-transfer (3MMLCT) nature, which is driven by attractive intermolecular M···M interactions further reinforced by the intramolecular π-π interactions even in the structure of the Pd compound, which is the first Pd-ADC phosphor reported.

NIR-II Emission from Cyclometalated Dinuclear Pt(III) Complexes

Half-lantern Pt(II) dinuclear complexes [{Pt(C∧Npz)(μ-S∧NR)}2] (HC∧Npz = 1-naphthalen-2-yl-1H-pyrazole; R = H, HS∧N: 2-mercaptopyrimidine 1; R = CF3, HS∧NF: 4-(trifluoromethyl)-2-mercaptopyrimidine 2) were selectively obtained as single isomers with the C∧N groups in an anti-arrangement and rather short metallophilic interactions (dPt-Pt = 2.8684(2) Å for 2). They reacted with haloforms in the air and sunlight to obtain the corresponding oxidized diplatinum(III) derivatives [{Pt(C∧Npz)(μ-S∧NR)X}2] (X = Cl (1-Cl), Br (1-Br), I (1-I, 2-I)). The single-crystal X-ray structures exhibit Pt-Pt distances typical for the existence of a metal-metal bond, which evidence fairly well the influence of the axial ligand (X). The reactions of 1 and 2 with CHI3 in the dark afforded mixtures of [IPt(C∧Npz)(μ-S∧N)2Pt(C∧Npz)CHI2] and 1-I or 2-I, with the former being the major species under an Ar atmosphere, while the reactions of 1 with CHBr3 and CHCl3 need light to occur. These Pt2(III,III) complexes display low-energy absorptions and emissions that strongly depend on the axial ligand. In the solid state, they show a broad NIR emission ranging from 985 to 1070 nm at RT that suffers a hypsochromic shift when cooling down to 77 K. The photoemissive behavior of the dinuclear Pt(II) and Pt(III) systems is disclosed with the aid of density functional theory calculations.

Quasi-Chromophores Segregated by Single-Chain Nanoparticles of Fluorinated Zwitterionic Random Copolymers Showing Remarkably Enhanced Fluorescence Emission Capable of Fluorescent Cell Imaging

Organic and polymer fluorescent nanomaterials are a frontier research focus. Here in this work, a series of fluorinated zwitterionic random copolymers end-attached with a quasi-chromophoric group of pyrene or tetraphenylethylene (TPE) are well synthesized via atom transfer radical polymerization with activators regenerated by electron transfer (ARGET ATRP). Those random copolymers with total degree of polymerization 100 or 200 are able to produce fluorescent single-chain nanoparticles (SCNPs) through intra-chain self-folding assembly with quite uniform diameters in the range of 10-20 nm as characterized by dynamic light scattering and transmission electron microscopy. By virtue of the segregation or confinement effect, both SCNPs functionalized with pyrene or TPE group are capable of emitting fluorescence, with pyrene tethered SCNPs exhibiting stronger fluorescence emission reaching the highest quantum yield ≈20%. Moreover, such kind of fluorescent SCNPs manifest low cytotoxicity and good cell imaging performance for Hela cells. The creation of fluorescent SCNPs through covalently attached one quasi-chromophore to the end of one fluorinated zwitterionic random copolymer provides an alternative strategy for preparing polymeric luminescence nanomaterials, promisingly serving as a new type of fluorescent nanoprobes for biological imaging applications.

One Dianionic Luminophore with Three Coordination Modes Binding Four Different Metals: Toward Unexpectedly Phosphorescent Transition Metal Complexes

This work reports on a battery of coordination compounds featuring a versatile dianionic luminophore adopting three different coordination modes (mono, bi, and tridentate) while chelating Pd(II), Pt(II), Au(III), and Hg(II) centers. An in-depth structural characterization of the ligand precursor (H2 L) and six transition metal complexes ([HLPdCNtBu], [LPtCl], [LPtCNtBu], [LPtCNPhen], [HLHgCl], and [LAuCl]) is presented. The influence of the cations and coordination modes of the luminophore and co-ligands on the photophysical properties (including photoluminescence quantum yields (ΦL ), excited state lifetimes (τ), and average (non-)radiative rate constants) are evaluated at various temperatures in different phases. Five complexes show interesting photophysical properties at room temperature (RT) in solution. Embedment in frozen glassy matrices at 77 K significantly boosts their luminescence by suppressing radiationless deactivation paths. Thus, the Pt(II)-based compounds provide the highest efficiencies, with slight variations upon exchange of the ancillary ligand. In the case of [HLPdCNtBu], both ΦL and τ increase over 30-fold as compared to RT. Furthermore, the Hg(II) complex achieves, for the first time in its class, a ΦL exceeding 60% and millisecond-range lifetimes. This demonstrates that a judicious ligand design can pave the way toward versatile coordination compounds with tunable excited state properties.

[Imaging of In Vivo Oxygen Tension Based on Phosphorescence Lifetime Microscopy]

Molecular oxygen plays essential roles in aerobic organisms as a terminal electron acceptor in the electron transport chain in mitochondria. The intracellular oxygen concentration of the entire body is strictly regulated by a balance between the supply of oxygen from blood vessels and the consumption of oxygen in mitochondria. The disruption of oxygen homeostasis in the body often results in serious pathologies such as cancer, cerebral infarction, and chronic kidney disease, and thus considerable effort has been devoted to the development of suitable techniques allowing the qualitative and quantitative detection of tissue oxygen levels. This review focuses on recent advances in the visualization of oxygen levels in tissue based on phosphorescence lifetime measurements using exogenously small molecular oxygen probes. Specially, I introduce the principle of oxygen sensing by means of phosphorescence quenching, recent advances in intracellular and intravascular oxygen probes based on iridium(III) complexes, a system for measuring phosphorescence lifetime combined with confocal scanning microscopy, and the applications of these technologies to in vivo oxygen measurements, emphasizing the usefulness of iridium(III) complexes as biological oxygen probes.

Molecularly Engineered Room-Temperature Phosphorescence for Biomedical Application: From the Visible toward Second Near-Infrared Window

Phosphorescence, characterized by luminescent lifetimes significantly longer than that of biological autofluorescence under ambient environment, is of great value for biomedical applications. Academic evidence of fluorescence imaging indicates that virtually all imaging metrics (sensitivity, resolution, and penetration depths) are improved when progressing into longer wavelength regions, especially the recently reported second near-infrared (NIR-II, 1000-1700 nm) window. Although the emission wavelength of probes does matter, it is not clear whether the guideline of "the longer the wavelength, the better the imaging effect" is still suitable for developing phosphorescent probes. For tissue-specific bioimaging, long-lived probes, even if they emit visible phosphorescence, enable accurate visualization of large deep tissues. For studies dealing with bioimaging of tiny biological architectures or dynamic physiopathological activities, the prerequisite is rigorous planning of long-wavelength phosphorescence, being aware of the cooperative contribution of long wavelengths and long lifetimes for improving the spatiotemporal resolution, penetration depth, and sensitivity of bioimaging. In this Review, emerging molecular engineering methods of room-temperature phosphorescence are discussed through the lens of photophysical mechanisms. We highlight the roles of phosphorescence with emission from visible to NIR-II windows toward bioapplications. To appreciate such advances, challenges and prospects in rapidly growing studies of room-temperature phosphorescence are described.

Enhanced luminescence properties through heavy ancillary ligands in [Pt(C^N^C)(L)] complexes, L = AsPh3 and SbPh3

In the frame of our research aiming to develop efficient triplet-emitting materials, we are exploring the concept of introducing additional heavy atoms into cyclometalated transition metal complexes to enhance intersystem-crossing (ISC) and thus triplet emission through increased spin-orbit coupling (SOC). In an in-depth proof-of-principle study we investigated the double cyclometalated Pt(II) complexes [Pt(C^N^C)(PnPh3)] (HC^N^CH = 2,6-diphenyl-pyridine (H2dpp) or dibenzoacridine (H2dba); Pn = pnictogen atoms P, As, Sb, or Bi) through a combined experimental and theoretical approach. The derivatives containing Pn = P, As, and Sb were synthesised and characterised comprehensively using single crystal X-ray diffraction (scXRD), UV-vis absorption and emission spectroscopy, transient absorption (TA) spectroscopy and cyclic voltammetry (CV). Across the series P < As < Sb, a red-shift is observed concerning absorption and emission maxima as well as optical and electrochemical HOMO-LUMO gaps. Increased photoluminescence quantum yields ΦL and radiative rates kr from mixed metal-to-ligand charge transfer (MLCT)/ligand centred (LC) triplet states are observed for the heavier homologues. Transient absorption spectroscopy showed processes in the ps range that were assigned to the population of the T1 state by ISC. The heavy PnPh3 ancillary ligands are found to enhance the emission efficiency due to both higher Pt-Pn bond strength and stronger SOC related to increased MLCT character of the excited states. The experimental findings are mirrored in hybrid (TD-)DFT calculations. This allowed for extrapolation to the rather elusive Bi derivatives, which were synthetically not accessible. This shortcoming is attributed to the transmetalation of phenyl groups from BiPh3 to Pt, as supported by experimental NMR/MS as well as DFT studies.

Nanomedicine Strategies in Conquering and Utilizing the Cancer Hypoxia Environment

Cancer with a complex pathological process is a major disease to human welfare. Due to the imbalance between oxygen (O2) supply and consumption, hypoxia is a natural characteristic of most solid tumors and an important obstacle for cancer therapy, which is closely related to tumor proliferation, metastasis, and invasion. Various strategies to exploit the feature of tumor hypoxia have been developed in the past decade, which can be used to alleviate tumor hypoxia, or utilize the hypoxia for targeted delivery and diagnostic imaging. The strategies to alleviate tumor hypoxia include delivering O2, in situ O2 generation, reprogramming the tumor vascular system, decreasing O2 consumption, and inhibiting HIF-1 related pathways. On the other side, hypoxia can also be utilized for hypoxia-responsive chemical construction and hypoxia-active prodrug-based strategies. Taking advantage of hypoxia in the tumor region, a number of methods have been applied to identify and keep track of changes in tumor hypoxia. Herein, we thoroughly review the recent progress of nanomedicine strategies in both conquering and utilizing hypoxia to combat cancer and put forward the prospect of emerging nanomaterials for future clinical transformation, which hopes to provide perspectives in nanomaterials design.

The Dual Luminescence Lifetime pH/Oxygen Sensor: Evaluation of Applicability for Intravital Analysis of 2D- and 3D-Cultivated Human Endometrial Mesenchymal Stromal Cells

The oxygenation of cells and tissues and acidification of the cellular endolysosomal system are among the major factors that ensure normal functioning of an organism and are violated in various pathologies. Recording of these parameters and their changes under various conditions is an important task for both basic research and clinical applications. In the present work, we utilized internalizable dual pH/O2 lifetime sensor (Ir-HSA-FITC) based on the covalent conjugation of human serum albumin (HSA) with fluorescein isothiocyanate (FITC) as pH sensor and an orthometalated iridium complex as O2 sensor. The probe was tested for simultaneous detection of acidification level and oxygen concentration in endolysosomes of endometrial mesenchymal stem/stromal cells (enMSCs) cultivated as 2D monolayers and 3D spheroids. Using a combined FLIM/PLIM approach, we found that due to high autofluorescence of enMSCs FITC lifetime signal in control cells was insufficient to estimate pH changes. However, using flow cytometry and confocal microscopy, we managed to detect the FITC signal response to inhibition of endolysosomal acidification by Bafilomycin A1. The iridium chromophore phosphorescence was detected reliably by all methods used. It was demonstrated that the sensor, accumulated in endolysosomes for 24 h, disappeared from proliferating 2D enMSCs by 72 h, but can still be recorded in non-proliferating spheroids. PLIM showed high sensitivity and responsiveness of iridium chromophore phosphorescence to experimental hypoxia both in 2D and 3D cultures. In spheroids, the phosphorescence signal was detected at a depth of up to 60 μm using PLIM and showed a gradient in the intracellular O2 level towards their center.

Afterglow/Photothermal Bifunctional Polymeric Nanoparticles for Precise Postbreast-Conserving Surgery Adjuvant Therapy and Early Recurrence Theranostic

Adjuvant whole-breast radiotherapy is essential for breast cancer patients who adopted breast-conserving surgery (BCS) to reduce the risk of local recurrences, which however suffer from large-area and highly destructive ionizing radiation-induced adverse events. To tackle this issue, an afterglow/photothermal bifunctional polymeric nanoparticle (APPN) is developed that utilizes nonionizing light for precise afterglow imaging-guided post-BCS adjuvant second near-infrared (NIR-II) photothermal therapy. APPN consists of a tumor cell targeting afterglow agent, which is doped with a NIR dye as an afterglow initiator and a NIR-II light-absorbing semiconducting polymer as a photothermal transducer. Such a design realizes precise afterglow imaging-guided NIR-II photothermal ablation of minimal residual breast tumor foci after BCS, thus achieving complete inhibition of local recurrences. Moreover, APPN enables early diagnosis and treatment of local recurrence after BCS. This study thus provides a nonionizing modality for precision post-BCS adjuvant therapy and early recurrence theranostic.

Sono-Driven STING Activation using Semiconducting Polymeric Nanoagonists for Precision Sono-Immunotherapy of Head and Neck Squamous Cell Carcinoma

Immunotherapy has offered new opportunities to treat head and neck squamous cell carcinoma (HNSCC); however, its clinical applications are hindered by modest therapeutic outcomes and the "always-on" pharmacological activity of immunomodulatory agents. Strategies for precise spatiotemporal activation of antitumor immunity can tackle these issues but remain challenging. Herein, a semiconducting polymeric nanoagonist (SPNM) with in situ sono-activatable immunotherapeutic effects for precision sono-immunotherapy of HNSCC is reported. SPNM is self-assembled from a sonodynamic semiconducting polymer core conjugated with a stimulator of interferon genes (STING) agonist (MSA-2) via a singlet oxygen cleavable linker. Under sono-irradiation, SPNM produces singlet oxygen not only to eradicate tumor cells to trigger immunogenic cell death but also to unleash caged STING agonists via the cleavage of diphenoxyethene bonds for in situ activation of the STING pathway in the tumor region. Such sono-driven STING activation mediated by SPNM promotes effector T cell infiltration and potentiates systemic antitumor immunity, eventually leading to tumor growth inhibition and long-term immunological memory. This study thus presents a promising strategy for the precise spatiotemporal activation of cancer immunotherapy.

Cyclometalated platinum(II) complexes with acyclic diaminocarbene ligands for OLED application

A novel series of cyclometalated platinum(II) complexes bearing acyclic diaminocarbene (ADC) ancillary ligands were designed and prepared. Their photophysical properties were systematically studied through experimental and theoretical investigations. All complexes exhibit green phosphorescence with a quantum efficiency of up to 45% in 2 wt% doped PMMA film at room temperature. The complexes are used as light-emitting dopants for organic light-emitting diode (OLED) fabrication. The devices displayed a green emission with a maximum current efficiency of 2.9 cd A^-1 and a luminance of 2700 cd m^-2. These results show that these cyclometalated platinum(II) complexes can be used as efficient green emitting components of OLED devices.

Multi-stimuli-responsive molecular fluorescent probes for bioapplications

Stimuli-responsive fluorescent probes have been widely utilized in detecting the physiological and pathological states of living systems. Numerous stimuli-responsive fluorescent probes have been developed due to their advantages of good sensitivity, high resolution, and high contrast fluorescent signals. In this feature article, the progress of multi-stimuli-responsive probes, including organic molecules and metal complexes, for the detection of various biomarkers for bio-applications is summarized. The feature article focuses on the applications of organic-molecule- and metal-complex-based molecular probes in biological systems for detecting different biomarkers of cancer or other diseases. The current challenges and potential future directions of these probes for applications in biological systems are also discussed.

Room-Temperature Phosphorescence from Pd(II) and Pt(II) Complexes as Supramolecular Luminophores: The Role of Self-Assembly, Metal-Metal Interactions, Spin-Orbit Coupling, and Ligand-Field Splitting

The synthesis as well as the structural and photophysical characterization of two isoleptic bis-cyclometalated Pt(II) and Pd(II) complexes, namely [PtL] and [PdL], bearing a tailored dianionic tetradentate ligand (L2-) are reported. The isostructural character and intermolecular interactions of [PtL] and [PdL] were assessed by NMR spectroscopy and X-ray diffraction analysis. Both complexes show fully ligand-controlled aggregation, demonstrating that a judicious molecular design can tune the photophysical properties. In fact, by introduction of fluorine atoms on defined positions and methoxy groups on complementary sites, metal-metal interactions can be forced by a head-to-tail stacking. Hence, [PtL] shows luminescence from metal-perturbed ligand-centered or from metal-metal-to-ligand charge-transfer triplet states in diluted solutions, in frozen glasses and in crystals, with high photoluminescence quantum yields and long lifetimes in the microsecond range. At room temperature (RT) in concentrated fluid solutions, the palladium analogue [PdL] surprisingly emits luminescence from aggregated species involving supramolecular interactions. Time-resolved photoluminescence and transient absorption spectroscopies demonstrated that ultrafast intersystem crossing occurs for both metals, which outruns any competitive relaxation pathway from the photoexcited singlet state. Furthermore, we demonstrate that the radiationless deactivation can be suppressed in frozen glassy matrices at 77 K and by intermolecular interactions in fluid solutions at RT. In both cases and as indicated by density functional theory calculations, the lowest emissive state acts as an energy trap from which the thermal population of dissociative states with formal occupation of an antibonding Pd-centered 4dx2-y2 orbital is suppressed. This occurs as the energy gap between the emissive and the dark states surpasses kT.

One-Pot Three Carbon Dots with Various Lifetimes Rooted in Different Decarboxylation Degrees for Matrix-Free, Anti-Oxygen, and Time-Resolved Information Encryption and Cellular Imaging

Activating long-lived room temperature phosphorescence (RTP) in the aqueous environment and thus realizing matrix-free, anti-oxygen, and time-resolved information encryption and cellular imaging remain a great challenge. Here, we fabricated three types of carbon dots (C-dots), i.e., fluorescent C-dots (F-C-dots) and two types of phosphorescent C-dots denoted as Pw-C-dots and Py-C-dots by a one-pot strategy. Their formation was attributed to the difference in the decarboxylation degree at high temperatures using trimesic acid (TMA) as a sole precursor. Unexpectedly, the yield reached as high as ∼92%, and the proportions were ∼27% for F-C-dots, ∼17% for Pw-C-dots, and ∼56% for Py-C-dots. These nanomaterials could help implement carbon peaking and carbon neutrality. Both green RTP of the two C-dots resulted from the small energy gap (ΔEST). These two RTP C-dots had a long lifetime of over 270 ms with a relatively high quantum yield (4.5 and 6.2%). They exhibited excellent photostability and anti-photobleaching performances. The dry and wet powders of the RTP C-dots were applied to high-level information encryption. The lifelike patterns were greatly different from those of the original ones and could last for several seconds to the naked eye, demonstrating that the RTP C-dots could be potentially employed as anti-oxygen and time-resolved contrast reagents. Most significantly, the cellular imaging experiments showed that the biofriendly PVP-coated Py-C-dots could localize at lysosomes and sustain hundreds of milliseconds. This approach not only pioneers a time-resolved lysosome localization model but also opens up a promising door for anti-oxygen and time-resolved RTP cytoimaging.

Triplet Emitting C^N^C Cyclometalated Dibenzo[c,h]Acridine Pt(II) Complexes

In a series of Pt(II) complexes [Pt(dba)(L)] containing the very rigid, dianionic, bis-cyclometalating, tridentate C^N^C2− heterocyclic ligand dba2− (H2dba = dibenzo[c,h]acridine), the coligand (ancillary ligand) L = dmso, PPh3, CNtBu and Me2Imd (N,N’-dimethylimidazolydene) was varied in order to improve its luminescence properties. Beginning with the previously reported dmso complex, we synthesized the PPh3, CNtBu and Me2Imd derivatives and characterized them by elemental analysis, 1H (and 31P) NMR spectroscopy and MS. Cyclic voltammetry showed partially reversible reduction waves ranging between −1.89 and −2.10 V and increasing along the series Me2Imd < dmso ≈ PPh3 < CNtBu. With irreversible oxidation waves ranging between 0.55 (L = Me2Imd) and 1.00 V (dmso), the electrochemical gaps range between 2.65 and 2.91 eV while increasing along the series Me2Imd < CNtBu < PPh3 < dmso. All four complexes show in part vibrationally structured long-wavelength absorption bands peaking at around 530 nm. TD-DFT calculated spectra agree quite well with the experimental spectra, with only a slight redshift. The photoluminescence spectra of all four compounds are very similar. In fluid solution at 298 K, they show broad, only partially structured bands, with maxima at around 590 nm, while in frozen glassy matrices at 77 K, slightly blue-shifted (~580 nm) bands with clear vibronic progressions were found. The photoluminescence quantum yields ΦL ranged between 0.04 and 0.24, at 298 K, and between 0.80 and 0.90 at 77 K. The lifetimes τ at 298 K ranged between 60 and 14040 ns in Ar-purged solutions and increased from 17 to 43 µs at 77 K. The TD-DFT calculated emission spectra are in excellent agreement with the experimental findings. In terms of high ΦL and long τ, the dmso and PPh3 complexes outperform the CNtBu and Me2Imd derivatives. This is remarkable in view of the higher ligand strength of Me2Imd, compared with all other coligands, as concluded from the electrochemical data.

Lighting up Micro-/Nanorobots with Fluorescence

Micro-/nanorobots (MNRs) can be autonomously propelled on demand in complex biological environments and thus may bring revolutionary changes to biomedicines. Fluorescence has been widely used in real-time imaging, chemo-/biosensing, and photo-(chemo-) therapy. The integration of MNRs with fluorescence generates fluorescent MNRs with unique advantages of optical trackability, on-the-fly environmental sensitivity, and targeting chemo-/photon-induced cytotoxicity. This review provides an up-to-date overview of fluorescent MNRs. After the highlighted elucidation about MNRs of various propulsion mechanisms and the introductory information on fluorescence with emphasis on the fluorescent mechanisms and materials, we systematically illustrate the design and preparation strategies to integrate MNRs with fluorescent substances and their biomedical applications in imaging-guided drug delivery, intelligent on-the-fly sensing and photo-(chemo-) therapy. In the end, we summarize the main challenges and provide an outlook on the future directions of fluorescent MNRs. This work is expected to attract and inspire researchers from different communities to advance the creation and practical application of fluorescent MNRs on a broad horizon.

Fluorene-decorated Ir(III) complexes: synthesis, photophysics and tunable triplet excited state properties in aggregation

Two new heteroleptic cationic Ir(III) complexes bearing benzothiazole and pyridine motifs on fluorene groups were synthesized and characterized. Complexes Ir1 and Ir2 exhibit ¹π,π* transitions below 430 nm, with broad but weak metal-to-ligand and ligand-to-ligand charge transfer absorption bands above 430 nm. Both complexes possess long-lived emissions (τ_em = 0.37 μs for Ir1, τ_em = 5.41 μs for Ir2) and triplet excited states (τ_TA = 0.14 μs for Ir1, τ_TA = 6.06 μs for Ir2). Their optical properties in solution and aggregated states were also investigated. Both Ir(III) complexes exhibit aggregation-induced phosphorescence emission behavior in an acetonitrile-water mixture. As the water content increased to 90%, the emission intensities of complexes Ir1 and Ir2 increased nearly 3 times and 2.8 times, respectively. Moreover, nonlinear transmittance experiments were performed in CH₃CN and a CH₃CN-H₂O mixture (f_w = 90%), and the strength of the reverse saturable absorption (RSA) at 532 nm followed the trend: Ir2 (CH₃CN) ≥ Ir1 (CH₃CN) > Ir2 (CH₃CN-H₂O) > Ir1 (CH₃CN-H₂O). Abundant triplet state excitons participated in the radiative transition progress, which inhibited the RSA process. These results indicate that the fluorene-decorated Ir(III) complexes are suitable for aggregation emission and optical power limiting applications.

Novel D-A chromophores with condensed 1,2,4-triazine system simultaneously display thermally activated delayed fluorescence and crystallization-induced phosphorescence

Control of photophysical properties is crucial for the continued development of electroluminescent devices and luminescent materials. Preparation and study of original molecules uncovers design rules towards efficient materials and devices. Here we have prepared 7 new compounds based on the popular donor-acceptor design used in thermally activated delayed fluorescence emitters. We introduce for the first time benzofuro[3,2-e]-1,2,4-triazine and benzothieno[3,2-e]-1,2,4-triazine acceptors which were connected to several common donors: phenoxazine, phenothiazine, carbazole and 3,6-di-tert-butylcarbazole. DFT calculations, and steady-state and time-resolved photophysical studies were conducted in solution and in solid states. While derivatives with azine moieties are non-emissive in any form, the compounds comprising 3,6-di-tert-butylcarbazole display TADF in all cases. More interestingly, the two derivatives substituted with a carbazole donor are TADF active when dispersed in a polymer matrix and phosphorescent at room temperature in neat films (microcrystalline form).

Long-Lived Photoluminescence of Molecular Group 14 Compounds through Thermally Activated Delayed Fluorescence

Photoluminescent molecules exploiting the sizable spin-orbit coupling constants of main group metals and metalloids to access long-lived triplet excited states are relatively rare compared to phosphorescent transition metal complexes. Here we report the synthesis of three air- and moisture-stable group 14 compounds E(^MePDP^Ph)₂, where E = Si, Ge, or Sn and [^MePDP^Ph]^2- is the doubly deprotonated form of 2,6-bis(5-methyl-3-phenyl-1H-pyrrol-2-yl)pyridine. In solution, all three molecules exhibit exceptionally long-lived triplet excited states with lifetimes in the millisecond range and show highly efficient photoluminescence (Φ ≤ 0.49) due to competing prompt fluorescence and thermally activated delayed fluorescence at and around room temperature. Temperature-dependent steady-state emission spectra and photoluminescent lifetime measurements provided conclusive evidence for the two distinct emission pathways. Picosecond transient absorption spectroscopy allowed further analysis of the intersystem crossing (ISC) between singlet and triplet manifolds (τ_ISC = 0.25-3.1 ns) and confirmed the expected trend of increased ISC rates for the heavier elements in otherwise isostructural compounds.

Mobile Phone Flashlight-Excited Red Afterglow Bioimaging

Organic room temperature phosphorescence (RTP) materials with ultralong lifetime possess the remarkable advantage in bioimaging for elimination of background noise by characteristic time scale. However, most of RTP luminogens need to be excited by the harmful ultraviolet (UV) lamp, and exhibit green or yellow emission with shallow tissue penetration, constraining the in vivo bioimaging for further application in clinical diagnosis and pathological study. In this text, the much safer excitation process by sunlight and mobile phone flashlight is realized by organic luminogens with various electronic pull-push systems. Moreover, the bright red RTP emission with lifetime up to 344 ms is achieved by optimizing molecular geometry and electronic property. Especially, the mobile phone flashlight-excited red afterglow imaging of lymph nodes in living mice has been realized for the first time, affording a safe and conventional approach to achieve the afterglow imaging of living mice with deep issue penetration and high signal-to-noise ratios.

Tetrathienothiophene Porphyrin as a Metal-Free Sensitizer for Room-Temperature Triplet–Triplet Annihilation Upconversion

Optically excited triplet states of organic molecules serve as an energy pool for the subsequent processes, either photon energy downhill, such as room temperature phosphorescence, or photon energy uphill process—the triplet–triplet annihilation upconversion (TTA-UC). Manifestation of a high intersystem crossing coefficient is an unavoidable requirement for triplet state formation, following the absorption of a single photon. This requirement is even more inevitable if the excitation light is non-coherent, with moderate intensity and extremely low spectral power density, when compared with the light parameters of 1 Sun (1.5 AM). Coordination of a heavy atom increases substantially the probability of intersystem crossing. Nevertheless, having in mind the global shortage in precious and rare-earth metals, identification of metal-free organic moieties able to form triplet states becomes a prerequisite for environmental friendly optoelectronic technologies. This motivates us to synthesize a metal-free thienothiophene containing porphyrin, based on a condensation reaction between thienothiophene-2-carbaldehyde and pyrrole in an acidic medium by modified synthetic protocol. The upconversion couple tetrathienothiophene porphyrin/rubrene when excited at λ = 658 nm demonstrates bright, delayed fluorescence with a maximum emission at λ = 555 nm. This verifies our hypothesis that the ISC coefficient in thienothiophene porphyrin is efficient in order to create even at room temperature and low-intensity optical excitation densely populated organic triplet ensemble and is suitable for photon energy uphill processes, which makes this type of metal-free sensitizers even more important for optoelectronic applications.

Biomedical polymers: synthesis, properties, and applications

Biomedical polymers have been extensively developed for promising applications in a lot of biomedical fields, such as therapeutic medicine delivery, disease detection and diagnosis, biosensing, regenerative medicine, and disease treatment. In this review, we summarize the most recent advances in the synthesis and application of biomedical polymers, and discuss the comprehensive understanding of their property-function relationship for corresponding biomedical applications. In particular, a few burgeoning bioactive polymers, such as peptide/biomembrane/microorganism/cell-based biomedical polymers, are also introduced and highlighted as the emerging biomaterials for cancer precision therapy. Furthermore, the foreseeable challenges and outlook of the development of more efficient, healthier and safer biomedical polymers are discussed. We wish this systemic and comprehensive review on highlighting frontier progress of biomedical polymers could inspire and promote new breakthrough in fundamental research and clinical translation.

Irreversible Humidity-Responsive Phosphorescence Materials from Cellulose for Advanced Anti-Counterfeiting and Environmental Monitoring

Organic phosphorescence materials have many unique advantages, such as a large Stokes shift, high signal-to-noise ratio, and no interference from background fluorescence and scattered light. But, they generally lack responsiveness. Herein, we developed a new type of biopolymer-based phosphorescence materials with excellent processability and irreversible humidity-responsiveness, via introducing the imidazolium cation to cellulose chain. In the resultant cellulose derivatives, the imidazolium cation promotes the intersystem crossing, meanwhile the cation, chloride anion, and hydroxyl group form multiple hydrogen bonding interactions and electrostatic attraction interactions, which successfully inhibit the nonradiative transitions. As a result, the ionic cellulose derivatives exhibit green phosphorescence at room temperature and can be processed into phosphorescent films, coatings, and patterns. More interestingly, their phosphorescence emission changes when the different processing solvents are used. The ionic cellulose derivatives processed with acetone have a negligible phosphorescence, while they give an irreversible humidity-responsive phosphorescence, which means that the ionic cellulose derivatives processed with acetone exhibit significantly enhanced phosphorescence once they meet water vapor. Such novel irreversible responsive phosphorescence materials have huge potential in advanced anticounterfeiting, information encryption, molecular logic gates, smart tags, and process monitoring.

Ultralong phosphorescence cellulose with excellent anti-bacterial, water-resistant and ease-to-process performance

Herein, we present a phosphorescent cationized cellulose derivative by simply introducing ionic structures, including cyanomethylimidazolium cations and chloride anions, into cellulose chains. The imidazolium cations with the cyano group and nitrogen element promote intersystem crossing. The cyano-containing cations, chloride anions and hydroxyl groups of cellulose form multiple hydrogen bonding interactions and electrostatic attraction interactions, effectively inhibiting the non-radiative transitions. The resultant cellulose-based RTP material is easily processed into phosphorescent films, fibers, coatings and patterns by using eco-friendly aqueous solution processing strategies. Furthermore, after we construct a cross-linking structure by adding a small amount of glutaraldehyde as the cross-linking agent, the as-fabricated phosphorescent patterns exhibit excellent antibacterial properties and water resistance. Therefore, considering the outstanding biodegradability and sustainability of cellulose materials, cellulose-based easy-to-process RTP materials can act as antibacterial, water-resistant, and eco-friendly phosphorescent patterns, coatings and bulk materials, which have enormous potential in advanced anti-counterfeiting, information encryption, disposable smart labels, etc.

Ruthenium(ii)-arene complexes as anti-metastatic agents, and related techniques

With the discovery of cisplatin, a vast area of applications of metallodrugs in cancer treatment was opened but due to the side effects caused by the cisplatin complexes, researchers began to look for alternatives with similar anticancer properties but fewer side effects. Ruthenium was found to be a promising candidate, considering its significant anticancer properties and low side effects. Several ruthenium complexes, viz. NAMI-A, KP1019, KP1339, and TLD1433, have entered clinical trials. Some other arene ruthenium complexes such as RM175 and RAPTA-C have also entered clinical trials but very few of them have shown anti-metastatic properties. Herein, we provide information and probable mechanistic pathways for ruthenium(ii)-arene complexes that have been studied, so far, for their anti-metastatic activities. Also, we discuss the techniques and their significance for determining the anti-metastatic effects of the complexes.

Bioimaging agents based on redox-active transition metal complexes

Detecting the fluctuation and distribution of various bioactive species in biological systems is of great importance in determining diseases at their early stages. Metal complex-based probes have attracted considerable attention in bioimaging applications owing to their unique advantages, such as high luminescence, good photostability, large Stokes shifts, low toxicity, and good biocompatibility. In this review, we summarized the development of redox-active transition metal complex-based probes in recent five years with the metal ions of iron, manganese, and copper, which play essential roles in life and can avoid the introduction of exogenous metals into biological systems. The designing principles that afford these complexes with optical or magnetic resonance (MR) imaging properties are elucidated. The applications of the complexes for bioimaging applications of different bioactive species are demonstrated. The current challenges and potential future directions of these probes for applications in biological systems are also discussed.

This review summarizes transition metal complexes as bioimaging agents in optical and magnetic resonance imaging.

Tuning the luminescence of transition metal complexes with acyclic diaminocarbene ligands

Organometallics featuring acyclic diaminocarbene ligands have recently emerged as powerful emitters for use in electroluminescent technologies.

Phosphorescent NIR emitters for biomedicine: applications, advances and challenges

Application of NIR (near-infrared) emitting transition metal complexes in biomedicine is a rapidly developing area of research. Emission of this class of compounds in the "optical transparency windows" of biological tissues and the intrinsic sensitivity of their phosphorescence to oxygen resulted in the preparation of several commercial oxygen sensors capable of deep (up to whole-body) and quantitative mapping of oxygen gradients suitable for in vivo experimental studies. In addition to this achievement, the last decade has also witnessed the increased growth of successful alternative applications of NIR phosphors that include (i) site-specific in vitro and in vivo visualization of sophisticated biological models ranging from 3D cell cultures to intact animals; (ii) sensing of various biologically relevant analytes, such as pH, reactive oxygen and nitrogen species, RedOx agents, etc.; (iii) and several therapeutic applications such as photodynamic (PDT), photothermal (PTT), and photoactivated cancer (PACT) therapies as well as their combinations with other therapeutic and imaging modalities to yield new variants of combined therapies and theranostics. Nevertheless, emerging applications of these compounds in experimental biomedicine and their implementation as therapeutic agents practically applicable in PDT, PTT, and PACT face challenges related to a critically important improvement of their photophysical and physico-chemical characteristics. This review outlines the current state of the art and achievements of the last decade and stresses the most promising trends, major development prospects, and challenges in the design of NIR phosphors suitable for biomedical applications.

Understanding the ancillary ligand effect on luminescent cyclometalated Ir(III) complex as a reporter for 2-acetylaminofluorene DNA(AAF-dG) adduct

Mutagenic agents such as aromatic amines undergo metabolic activation and produce DNA adducts at C8 position of guanine bases. N-2-acetylaminofluorene (AAF) generates different mutational outcomes when placed at G₁, G₂, and G₃ of a NarI sequence (-G₁G₂CG₃CC/T-). These outcomes are dictated by the conformations adopted by these adducts. Detection of such lesions is of considerable interest owing to their hazardous effects. Here, we report the synthesis of three cyclometalated [Ir(L)₂dppz]⁺ complexes (L = 2-phenylpyridine (ppy) 1; benzo[h]quinoline (bhq) 2; 2-phenylquinoline (pq) 3; dppz = dipyrido[3,2-a:2',3'-c]phenazine) and their interaction with AAF adducted NarI DNA. Remarkably, complexes 1 and 2 displayed dominant ³LC transition characteristic of polar environment despite binding to the adducted sites. On the other hand, complex 3 binds to NarI sequences and behaves as a luminescent reporter for AAF-modified DNA. The results reported here emphasize that molecular light switching phenomenon can be stimulated by switching ancillary ligands and might act as potential probes for covalent-DNA defects.

Recent progress in metal-based molecular probes for optical bioimaging and biosensing

Biological imaging and biosensing from subcellular/cellular level to whole body have enabled non-invasive visualisation of molecular events during various biological and pathological processes, giving great contributions to the rapid and impressive advances in chemical biology, drug discovery, disease diagnosis and prognosis. Optical imaging features a series of merits, including convenience, high resolution, good sensitivity, low cost and the absence of ionizing radiation. Among different luminescent probes, metal-based molecules offer unique promise in optical bioimaging and biosensing in vitro and in vivo, arising from their small sizes, strong luminescence, large Stokes shifts, long lifetimes, high photostability and tunable toxicity. In this review, we aim to highlight the design of metal-based molecular probes from the standpoint of synthetic chemistry in the last 2 years for optical imaging, covering d-block transition metal and lanthanide complexes and multimodal imaging agents.

Dynamic Manipulating Space-Resolved Persistent Luminescence in Core-Shell MOFs Heterostructures via Reversible Photochromism

Photo-controllable persistent luminescence at the single crystal level can be achieved by the integration of long-lived room temperature phosphorescence (RTP) and photochromism within metal-organic frameworks (MOFs) for the first time. Moreover, the multiblock core-shell heterojunctions have been prepared utilizing the isostructural MOFs through an epitaxial growth process, in which the shell exhibits bright yellow afterglow emission that gradually disappears upon further irradiation, but the core does not show such property. Benefitting from combined persistent luminescence and photochromic behavior, a multiple encryption demo can be facilely designed based on the dynamic manipulating RTP via reversible photochromism. This work not only develops new types of dynamically photo-controllable afterglow switch, but also provides a method to obtain MOFs-based optical heterojunctions towards potential space/time-resolved information encryption and anti-counterfeiting applications.

Functionalizing Collagen with Vessel-Penetrating Two-Photon Phosphorescence Probes: A New In Vivo Strategy to Map Oxygen Concentration in Tumor Microenvironment and Tissue Ischemia

The encapsulation and/or surface modification can stabilize and protect the phosphorescence bio-probes but impede their intravenous delivery across biological barriers. Here, a new class of biocompatible rhenium (ReI ) diimine carbonyl complexes is developed, which can efficaciously permeate normal vessel walls and then functionalize the extravascular collagen matrixes as in situ oxygen sensor. Without protective agents, ReI -diimine complex already exhibits excellent emission yield (34%, λem   = 583 nm) and large two-photon absorption cross-sections (σ2   = 300 GM @ 800 nm) in water (pH 7.4). After extravasation, remarkably, the collagen-bound probes further enhanced their excitation efficiency by increasing the deoxygenated lifetime from 4.0 to 7.5 µs, paving a way to visualize tumor hypoxia and tissue ischemia in vivo. The post-extravasation functionalization of extracellular matrixes demonstrates a new methodology for biomaterial-empowered phosphorescence sensing and imaging.

Near-infrared emitting iridium complexes: Molecular design, photophysical properties, and related applications

Organic light-emitting diodes (OLEDs) have become popular displays from small screens of wearables to large screens of televisions. In those active-matrix OLED displays, phosphorescent iridium(III) complexes serve as the indispensable green and red emitters because of their high luminous efficiency, excellent color tunability, and high durability. However, in contrast to their brilliant success in the visible region, iridium complexes are still underperforming in the near-infrared (NIR) region, particular in poor luminous efficiency according to the energy gap law. In this review, we first recall the basic theory of phosphorescent iridium complexes and explore their full potential for NIR emission. Next, the recent advances in NIR-emitting iridium complexes are summarized by highlighting design strategies and the structure-properties relationship. Some important implications for controlling photophysical properties are revealed. Moreover, as promising applications, NIR-OLEDs and bio-imaging based on NIR Ir(III) complexes are also presented. Finally, challenges and opportunities for NIR-emitting iridium complexes are envisioned.

Strategies to promote permeation and vectorization, and reduce cytotoxicity of metal complex luminophores for bioimaging and intracellular sensing

Transition metal luminophores are emerging as important tools for intracellular imaging and sensing. Their putative suitability for such applications has long been recognised but poor membrane permeability and cytotoxicity were significant barriers that impeded early progress. In recent years, numerous effective routes to overcoming these issues have been reported, inspired in part, by advances and insights from the pharmaceutical and drug delivery domains. In particular, the conjugation of biomolecules but also other less natural synthetic species, from a repertoire of functional motifs have granted membrane permeability and cellular targeting. Such motifs can also reduce cytotoxicity of transition metal complexes and offer a valuable avenue to circumvent such problems leading to promising metal complex candidates for application in bioimaging, sensing and diagnostics. The advances in metal complex probes permeability/targeting are timely, as, in parallel, over the past two decades significant technological advances in luminescence imaging have occurred. In particular, super-resolution imaging is enormously powerful but makes substantial demands of its imaging contrast agents and metal complex luminophores frequently possess the photophysical characteristics to meet these demands. Here, we review some of the key vectors that have been conjugated to transition metal complex luminophores to promote their use in intra-cellular imaging applications. We evaluate some of the most effective strategies in terms of membrane permeability, intracellular targeting and what impact these approaches have on toxicity and phototoxicity which are important considerations in a luminescent contrast or sensing agent.

Free-radical cyclization approach to polyheterocycles containing pyrrole and pyridine rings

A wide range of derivatives with new pyrido[2,1-a]pyrrolo[3,4-c]isoquinoline skeleton was synthesized by free-radical intramolecular cyclization of o-bromophenyl-substituted pyrrolylpyridinium salts using the (TMS)₃SiH/AIBN system. The cyclization provides generally good yields of pyrido[2,1-a]pyrrolo[3,4-c]isoquinoline hydrobromides having no additional radical-sensitive substituents. The free bases can be obtained from the synthesized hydrobromides in quantitative yield by basification at room temperature. The selectivity control of intramolecular arylation was achieved by replacing the halogen: the use of 1-(2-(ortho-bromophenyl)-4-(ortho-iodophenyl)pyrrol-3-yl)pyridinium bromide makes it possible to obtain a monocyclization product, and the bicyclization product from the dibromo derivative. The procedure is also applicable to obtain 3-arylpyrido[2,1-a]pyrrolo[3,2-c]isoquinoline derivatives including 2-unsubstituted skeletons that are inaccessible via Pd-catalyzed cyclization.

Triple-mode tunable long-persistent luminescence in a 3D zinc-organic hybrid

A 3D zinc-organic hybrid [Zn3(D-Cam)3(tib)2]·2H2O (1) exhibits triple-mode dependent (including excitation wavelength, time and temperature) long-persistent luminescence. Experimental and theoretical calculations support that the long lifetime and color-tunable afterglow may be due to the dispersive electronic state distribution. Furthermore, the hybrid is also used for optical anti-counterfeiting and information encryption applications.

Development of mesoporous silica-based nanoprobes for optical bioimaging applications

A mesoporous silica nanoparticle (MSN)-based nanoplatform has attracted growing attention in the biomedical field due to the unique characteristics of MSNs including a high surface area, tunable pore sizes, colloidal stability, ease of functionalization, and desirable biocompatibility. Typically, MSNs are designed as nanocarriers for the incorporation of a variety of contrast agents for bioimaging, which can address the intrinsic drawbacks of contrast agents, including poor solubility in water, rapid photobleaching, and low stability. This review summarizes the recent advances in the field of MSN-based nanoprobes for fluorescence imaging and photoacoustic (PA) imaging applications. The approaches for the incorporation of contrast agents into MSN-based nanoplatforms including encapsulating contrast agents within MSNs, covalently conjugating contrast agents on the surface or pores of MSNs, physically absorbing contrast agents in the pores of MSNs, and doping contrast agents in the framework of MSNs are introduced. MSN-based nanoprobes for fluorescence imaging and PA imaging are discussed. The enhanced fluorescence imaging and PA imaging performances of MSN-based nanoprobes relative to the bare contrast agents are introduced and the underlying mechanisms are discussed in detail. Finally, current challenges and perspectives of MSN-based nanoprobes in the bioimaging field are discussed.

Recent advances in cancer photo-theranostics: the synergistic combination of transition metal complexes and gold nanostructures

In this mini review, we highlight advances in the last five years in light-activated cancer theranostics by using hybrid systems consisting of transition metal complexes (TMCs) and plasmonic gold nanostructures (AuNPs). TMCs are molecules with attractive properties and high potential in biomedical application. Due to their antiproliferative abilities, platinum-based compounds are currently first-choice drugs for the treatment of several solid tumors. Moreover, ruthenium, iridium and platinum complexes are well-known for their ability to photogenerate singlet oxygen, a highly cytotoxic reactive species with a key role in photodynamic therapy. Their potential is further extended by the unique photophysical properties, which make TMCs particularly suitable for bioimaging. Recently, gold nanoparticles (AuNPs) have been widely investigated as one of the leading nanomaterials in cancer theranostics. AuNPs—being an inert and highly biocompatible material—represent excellent drug delivery systems, overcoming most of the side effects associated with the systemic administration of anticancer drugs. Furthermore, due to the thermoplasmonic properties, AuNPs proved to be efficient nano-sources of heat for photothermal therapy application. Therefore, the hybrid combination TMC/AuNPs could represent a synergistic merger of multiple functionalities for combinatorial cancer therapy strategies. Herein, we report the most recent examples of TMC/AuNPs systems in in-vitro in-vivo cancer tharanostics application whose effects are triggered by light-exposure in the Vis–NIR region, leading to a spatial and temporal control of the TMC/AuNPs activation for light-mediated precision therapeutics.

Effect of π···π Interactions of Donor Rings on Persistent Room-Temperature Phosphorescence in D4-A Conjugates and Data Security Application

Organic room-temperature phosphorescence (RTP) materials with persistent RTP (PRTP) have attracted huge interest in inks, bioimaging, and photodynamic therapy. However, the design principle to increase the lifetime of organic molecules is underdeveloped. Herein, we show donor(D₄)-acceptor(A) molecules (TOEPh, TOCPh, TOMPh, TOF and TOPh) with similar orientation of donor rings in aggregates that cause a large number of noncovalent interactions. We observed that TOEPh, TOCPh, TOMPh and TOF showed PRTP, whereas TOPh showed only phosphorescence emission (Φ_P = ∼11%) with no PRTP property at ambient conditions. The spectroscopic and single-crystal X-ray analyses confirm the molecular assembly via J-aggregation with a face-to-face orientation of the donor rings. The crystal structure analysis (TOEPh, TOCPh, TOMPh, TOF) reveals that moderate π···π interactions (3.706 to 4.065 Å) between the donor rings cause the enhancement of the phosphorescence lifetime (26 to 245 ms), whereas the short phosphorescence lifetime (12 ms) of TOPh was observed because of the absence of π···π interactions. We found that TOEPh shows a long lifetime (245 ms) as compared to other derivatives because of the presence of ethoxy (-OEt) groups that enables spin-orbit coupling caused by strong lone pair (O)···π interactions present in the molecule. Utilizing the PRTP feature of TOEPh and the fluorescence emission of TOPh, we have shown data security applications in poly(methyl methacrylate).