Near-IR Core-Substituted Naphthalenediimide Fluorescent Chemosensors for Zinc Ions: Ligand Effects on PET and ICT Channels

Molecular Engineering of a Doubly Quenched Fluorescent Probe Enables Ultrasensitive Detection of Biothiols in Highly Diluted Plasma and High-Fidelity Imaging of Dihydroartemisinin-Induced Ferroptosis

The occurrence and development of diseases are accompanied by abnormal activity or concentration of biomarkers in cells, tissues, and blood. However, the insufficient sensitivity and accuracy of the available fluorescence probes hinder the precise monitoring of associated indexes in biological systems, which is generally due to the high probe intrinsic fluorescence and false-negative signal caused by the reactive oxygen species (ROS)-induced probe decomposition. To resolve these problems, we have engineered a ROS-stable, meso-carboxylate boron dipyrromethene (BODIPY)-based fluorescent probe, which displays quite a low background fluorescence due to the doubly quenched intrinsic fluorescence by a combined strategy of the photoinduced electron transfer (PET) effect and "ester-to-carboxylate" conversion. The probe achieved a high S/N ratio with ultrasensitivity and good selectivity toward biothiols, endowing its fast detection capability toward the biothiol level in 200×-diluted plasma samples. Using this probe, we achieved remarkable distinguishing of liver injury plasma from normal plasma even at 80× dilution. Moreover, owing to its good stability toward ROS, the probe was successfully employed for high-fidelity imaging of the negative fluctuation of the biothiol level in nonsmall-cell lung cancer (NSCLC) during dihydroartemisinin-induced ferroptosis. This delicate design of suppressing intrinsic fluorescence reveals insights into enhancing the sensitivity and accuracy of fluorescent probes toward the detection and imaging of biomarkers in the occurrence and development of diseases.

Dual-Responsive and Aggregation-Induced-Emission Probe for Selective Imaging of Infectious Urolithiasis

Identifying infected stones is crucial due to their rapid growth and high recurrence rate. Here, the calcium-magnesium dual-responsive aggregation-induced emission (AIE)-active probe TCM-5COOH (Tricyano-methlene-pyridine-5COOH), distinctively engineered to distinguish high-threat infection calculi from metabolic stones, is presented. Upon incorporation of flexible alkyl carboxyl group, TCM-5COOH featuring five carboxyl moieties demonstrates excellent water solubility and enhanced penetration into porous infectious stones. The robust chelation of TCM-5COOH with stone surface-abundant Ca2+ and Mg2+ inhibits vibrational relaxation, thus triggering intense AIE signals. Remarkably, the resulting complex exhibits high insolubility, effectively anchoring within the porous structure of the infection calculi and offering prolonged illumination. Jobs' plot method reveals similar response characteristics for Ca2+ and Mg2+, with a 1:2 coordination number for both ions. Isothermal titration calorimetry (ITC) results demonstrate higher enthalpy change (ΔH) and lower entropy change (ΔS) for the reaction, indicating enhanced selectivity compared to TCM-4COOH lacking the alkyl carboxyl group. Synchrotron X-ray absorption fine spectroscopy (XAFS) validates TCM-5COOH's interaction with Ca2+ and Mg2+ at the microlevel. This dual-responsive probe excels in identifying infectious and metabolic calculi, compatible with endoscopic modalities and laser excitation, thereby prompting clinical visualization and diagnostic assessment.

Synthesis, Photophysical Properties and Self-Assembly of a Tetraphenylethylene-Naphthalene Diimide Donor-Acceptor Molecule

The development of new π-conjugated molecular structures with controlled self-assembly and distinct photophysical properties is crucial for advancing applications in optoelectronics and biomaterials. This study introduces the synthesis and detailed self-assembly analysis of tetraphenylethylene (TPE) functionalized naphthalene diimide (NDI), a novel donor-acceptor molecular structure referred to as TPE-NDI. The investigation specifically focuses on elucidating the self-assembly behavior of TPE-NDI in mixed solvents of varying polarities, namely chloroform: methylcyclohexane (CHCl3 : MCH) and chloroform: methanol (CHCl3 : MeOH). Employing a several analytical methodologies, including UV-Vis absorption and fluorescence emission spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and dynamic light scattering (DLS), these self-assembled systems have been comprehensively examined. The results reveal that TPE-NDI manifests as distinct particles in CHCl3 : MCH (fMCH =90 %), while transitioning to flower-like assemblies in CHCl3 : MeOH (fMeOH =90 %). This finding underscores the critical role of solvent polarity in dictating the morphological characteristics of TPE-NDI self-assembled aggregates. Furthermore, the study proposes a molecular packing mechanism, based on SEM data, offering significant insights into the design and development of functional supramolecular systems. Such advancements in understanding the molecular self-assembly new π-conjugated molecular structures are anticipated to pave the way for novel applications in material science and nanotechnology.

A Near InfraRed Emissive Chemosensor for Zn2+ and Phosphate Derivatives Based on a Di-(2-picolyl)amine-styrylflavylium Push-Pull Fluorophore

A new Near InfraRed (NIR) fluorescent chemosensor for metal ions and anions is herein presented. The fluorophore is based on a styrylflavylium dye, a synthetic analogue of the natural anthocyanin family, with a di-(2-picolyl)amine (DPA) moiety as the metal chelating unit. The substitution pattern of the styrylflavylium core (with tertiary amines on positions 7 and 4') shifts the optical properties of the dye towards the NIR region of the electronic spectra, due to a strong push-pull character over the π-conjugated system. The NIR chemosensor is highly sensitive to the presence of Zn²⁺, which induces a strong CHelation Enhanced Fluorescence (CHEF) effect upon binding to the DPA unit (2.7 fold increase). The strongest competing ion is Cu²⁺, with a complete fluorescence quenching, while other metals induce lower responses on the optical properties of the chemosensor. Subsequent anion screening of the Zn²⁺-chemosensor coordination compound has demonstrated a distinct selectivity towards adenosine 5'-triphosphate (ATP) and adenosine 5'-diphosphate (ADP), with high association constants (K ~ 10⁶ M^-1) and a strong CHEF effect (2.4 and 2.9 fold fluorescence increase for ATP and ADP, respectively). Intracellular studies with the Zn²⁺-complexed sensor showed strong luminescence in the cellular membrane of Gram^- bacteria (E. coli) and mitochondrial membrane of mammalian cells (A659), which highlights its possible application for intracellular labelling.

A New 'Off-On' System Based on Core-Substituted Naphthalene Diimide with Dimethylamine for Reversible Acid-Base Sensing

A new 'Off-On' system designed and synthesised by functionalisation of a naphthalene diimide (NDI) core with dimethylamine produces 4,9-bis(dimethylamino)-2,7-dioctylbenzo[lmn][3,8]-phenanthroline-1,3,6,8-(2H,7H)-tetraone, abbreviated as DDPT (1). DDPT 1 was synthesised using a simple strategy, namely aromatic nucleophilic substitution using Br2 -NDI with dimethylamine at 110 °C. DDPT was characterized by 1 H and 13 C NMR spectroscopy, ESI mass spectrometry and elemental analysis. DDPT 1 was then used for optical studies through protonation of its dimethylamine core with trifluoroacetic acid (TFA), blue-shifting the absorption band from 600 nm to 545 nm in solution. Interestingly, the fluorescence of DDPT 1 is weak in solution with a quantum yield Φ=0.09, which is significantly enhanced to Φ=0.78 upon addition of TFA. The limit of detection (LOD) was determined to 2.77 nm. Furthermore, DDPT 1 can be used for naked eyed detection not only under UV light (365 nm) but also using visible light, as clear changes can be clearly seen upon addition of TFA. The binding constant of DDPT was calculated to 2.1×10-3  m-1 . Importantly, DDPT 1 showed reversible switching by alternative addition of acid (TFA) and base (triethylamine) without loss of activity. Immobilised on paper, DDPT 1 can be used for strip-test sensing in which the colour changes from blue to reddish when expose to TFA vapours and reverse in the presence of triethylamine vapours.

A Review on Organic Colorimetric and Fluorescent Chemosensors for the Detection of Zn(II) Ions

Organic compounds display several electronic and structural features which enable their application in various fields, ranging from biological to non-biological. These compounds contain heteroatoms like sulfur, nitrogen and, oxygen, which provide coordination sites to act as ligands in the field of coordination chemistry and are used as chemosensors to detect various metal ions. This review article covers different organic compounds including Schiff bases, thiourea, pyridine, rhodamine, triazole, pyrene, coumarin, imidazole, diaminomaleonitrile, naphthoxazole, pyrimidine, thiophene, thioether, and other functional groups based chemosensors that contain heteroatoms like sulfur, nitrogen and, oxygen for fluorimetric and colorimetric detection of Zn(II) ions in different environmental, agricultural, and biological samples. Further, the sensing performances of these chemosensors have been compared and discussed which could help the readers for the future design of organic fluorescent and colorimetric chemosensors for the detection of Zn(II) ions. We hope this study will support the new thoughts to design a simple, efficient, selective, and sensitive chemosensor for the detection of Zn(II) ions in different samples (environmental, agricultural, and biological).

Mixed Ionic and Electronic Conduction in Small-Molecule Semiconductors

Small-molecule organic semiconductors have displayed remarkable electronic properties with a multitude of π-conjugated structures developed and fine-tuned over recent years to afford highly efficient hole- and electron-transporting materials. Already making a significant impact on organic electronic applications including organic field-effect transistors and solar cells, this class of materials is also now naturally being considered for the emerging field of organic bioelectronics. In efforts aimed at identifying and developing (semi)conducting materials for bioelectronic applications, particular attention has been placed on materials displaying mixed ionic and electronic conduction to interface efficiently with the inherently ionic biological world. Such mixed conductors are conveniently evaluated using an organic electrochemical transistor, which further presents itself as an ideal bioelectronic device for transducing biological signals into electrical signals. Here, we review recent literature relevant for the design of small-molecule mixed ionic and electronic conductors. We assess important classes of p- and n-type small-molecule semiconductors, consider structural modifications relevant for mixed conduction and for specific interactions with ionic species, and discuss the outlook of small-molecule semiconductors in the context of organic bioelectronics.

Naphthalenediimides with High Fluorescence Quantum Yield: Bright-Red, Stable, and Responsive Fluorescent Dyes

The naphthalenediimide (NDI) scaffold in contrast to its higher congeners possess low-fluorescence. In spite of elegant synthetic developments, a highly emissive NDI is quite rare to find, as well as, a green-light-emitting NDI is yet to be explored. Herein, we report a novel class of symmetric and asymmetric NH₂ -substituted core-NDIs (1-5) with tunable fluorescence in the visible region and extending to the NIR frontier. Importantly, the bis-NH₂ -substituted NDI 2 revealed quantum yield, Φ f of ≈81 and ≈68 % in toluene and DMSO, respectively, suggesting versatility of the fluorophore in a wide range of solvent polarity. The dye 1 is shown to be the first NDI-based green-light emitter. The donor piperidine group in 5 diminish the Φ f by 40-fold providing a lever to modulate the excited-state intramolecular proton transfer (ESIPT) process. Our synthetic protocol applies a Pd catalyst and a benign hydride source simplifying the non-trivial -NH₂ group integration at the NDI-core. TD-DFT calculations predicted strong intramolecular hydrogen bonds in the excited state in the bulk nonpolar medium and responsiveness to solvent polarity. The maximization of the NDI emission outlined here would further boost the burgeoning repertoire of applications of the NDI scaffold.

Successive Detection of Zinc Ion and Citrate Using a Schiff Base Chemosensor for Enhanced Prostate Cancer Diagnosis in Biosystems

Sensitive and quantitative detection of prostate cancer (PC) requires a chemosensor with an applicable sensing strategy. A star-shaped Schiff base triaminoguanidine-integrated thiophene fluorophore TAT was rationally designed with nitrogen and sulfur atoms to coordinate with Zn²⁺ as the initial step and to chelate with citrate as the following step. Formation of the complex TAT-Zn²⁺ induced an intramolecular charge transfer and caused a red-shifted, Zn²⁺ concentration-dependent fluorescence at 507 nm. Chelation of TAT-Zn²⁺ with citrate led to an emission band at 692 nm upon an aggregation-induced emission mechanism. The distinctive fluorescence emissions of Zn²⁺ and citrate biomarkers were demonstrated first in on-site paper-based test strips showing gradually enhanced colors at yellow and red channels and second in both in vitro and in vivo by using PC3 cells and BALB/c nude mouse animal models, respectively. The in vitro test confirmed the mitochondria organelle-targeting property of TAT, and the in vivo performance manifested the successful application of the probe in recognizing the prostate cancer. This is the first applicable chemosensor that could be in continuous recognition of dual PC biomarkers Zn²⁺ and citrate in cancer diagnosis with a mitochondria organelle-targeting ability.

Performance of TDDFT Vertical Excitation Energies of Core-Substituted Naphthalene Diimides

We have evaluated the performance of various density functionals, covering generalized gradient approximation (GGA), global hybrid (GH) and range‐separated hybrid (RSH), using time dependent density functional theory (TDDFT) for computing vertical excitation energies against experimental absorption maximum (λ_max) for a set of 10 different core‐substituted naphthalene diimides (cNDI) recorded in dichloromethane. The computed excitation in case of GH PBE0 is most accurate while the trend is most systematic with RSH LCY‐BLYP compared to λ_max. We highlight the importance of including solvent effects for optimal agreement with the λ_max. Increasing the basis set size from TZ2P to QZ4P has a negligible influence on the computed excitation energies. Notably, RSH CAMY‐B3LYP gave the least error for charge‐transfer excitation. The poorest agreement with λ_max is obtained with semi‐local GGA functionals. Use of the optimally‐tuned RSH LCY‐BLYP* is not recommended because of the high computational cost and marginal improvement in results.

Polyoxometalate-based room-temperature phosphorescent materials induced by anion–π interactions

A series of polyoxometalate-based host–guest materials emit strong red room-temperature phosphorescence attributed to intermolecular charge-transfer states which was caused by unorthodox anion–π interactions.

Evaluating the merit of a diethylamino coumarin-derived thiosemicarbazone as an intramolecular charge transfer probe: efficient Zn(ii) mediated emission swing from green to yellow

We report the synthesis and photophysical properties of a coumarin based probe (1E)-1-(1-(7-(diethylamino)-2-oxo-2H-chromen-3-yl) ethylidene) thiosemicarbazide (DIDOT). DIDOT shows a polarity dependent change in the emission maxima in the solution phase. This is explained by the increased dipole moment in the excited state by an intramolecular charge transfer (ICT) process. DIDOT can successfully detect Zn(ii) in aqueous methanol by a shift in the charge transfer emission maxima from approximately 506 to approximately 535 nm. This shift led to a change in the color of the emission from green to yellow under UV-light. The mechanism of Zn(ii) detection has been delineated using electrospray ionization-mass spectrometry (ESI-MS), Fourier-transform infrared spectroscopy (FTIR) and fluorescence time resolved studies coupled with theoretical calculations. The increment in the charge transfer in the Zn(ii) complex of DIDOT over the bare receptor as a consequence of conformational locking was determined to be the underlying cause of the cation detection phenomenon. The limit of detection and binding constant values of DIDOT towards Zn(ii) were approximately 3 × 10^-8 M and 2.35 × 10⁵ M^-1 respectively. Finally, the practical utility of DIDOT has been demonstrated by successful detection and quantification of Zn(ii) in spiked water samples.

Golgi Apparatus Polarity Indicates Depression-Like Behaviors of Mice Using in Vivo Fluorescence Imaging

Depression is associated with decreased expression of brain-derived neurotrophic factor (BDNF) which assembled in Golgi apparatus. The changes might be closely related to variation in Golgi apparatus polarity. Thus, developing a nondestructive method to detect polarity in living cells and in vivo can facilitate accurate diagnosis and prognosis of depression. Herein, we created a new near-infrared Golgi-targetable fluorescent probe (Golgi-P) in which the merocyanine and benzoyl difluoroboronate moieties sense polarity changes. Golgi-P exhibited a decrease in fluorescence intensity and red-shift of maximum emission wavelength as the increase in polarity. Using Golgi-P, we discovered distinctly higher polarity in brains of mice with depression phenotype for the first time. Furthermore, our results disclosed that the elevation of polarity could due to the reduced synthesis of BDNF. Altogether, this study offers a new strategy for the accurate diagnosis of depression.

Efficient Radical-Enhanced Intersystem Crossing in an NDI-TEMPO Dyad: Photophysics, Electron Spin Polarization, and Application in Photodynamic Therapy

A compact naphthalenediimide (NDI)-2,2,6,6-tetramethylpiperidinyloxy (TEMPO) dyad has been prepared with the aim of studying radical-enhanced intersystem crossing (EISC) and the formation of high spin states as well as electron spin polarization (ESP) dynamics. Compared with the previously reported radical-chromophore dyads, the present system shows a very high triplet state quantum yield (Φ_T =74 %), a long-lived triplet state (τ_T =8.7 μs), fast EISC (1/k_EISC =338 ps), and absorption in the red spectral region. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy showed that, upon photoexcitation in fluid solution at room temperature, the D₀ state of the TEMPO moiety produces strong emissive (E) polarization owing to the quenching of the excited singlet state of NDI by the radical moiety (electron exchange J>0). The emissive polarization then inverts into absorptive (A) polarization within about 3 μs, and then relaxes to a thermal equilibrium while quenching the triplet state of NDI. The formation and decay of the quartet state were also observed. The dyad was used as a three-spin triplet photosensitizer for triplet-triplet annihilation upconversion (quantum yield Φ_UC =2.6 %). Remarkably, when encapsulated into liposomes, the red-light-absorbing dyad-liposomes show good biocompatibility and excellent photodynamic therapy efficiency (phototoxicity EC₅₀ =3.22 μm), and therefore is a promising candidate for future less toxic and multifunctional photodynamic therapeutic reagents.

Potentially toxic elements and environmentally-related pollutants recognition using colorimetric and ratiometric fluorescent probes

A safer detection or sensing of toxic pollutants is one among several environmental contamination issues, across the globe. The ever-increasing industrial practices and controlled or uncontrolled release of toxic pollutants from various industrial sectors is a key source of this environmental problem. Significant research efforts have been or being made to tackle this problematic issue to fulfill the growing needs of the modern world. Despite many useful aspects, heavy metals are posing noteworthy toxicological concerns and human-health related issues at various levels of the ecosystem. In this context, notable efforts from various regulatory authorities, the increase in the concentration of these toxic heavy metals in the environment is of serious concern, so real-time monitoring is urgently required. Herein, we reviewed fluorescent sensor based models and their potentialities to address the detection fate of hazardous pollutants including chromium, manganese, cobalt, nickel, copper, and zinc as model elements. The novel aspects of turn-on/off fluorescent sensors have also been discussed from a state of the art viewpoint. In summary, comprehensive literature regarding fluorescent sensor based models and their potentialities to detect various types of toxic pollutants is reviewed.

Intramolecular Energy and Electron Transfers in Bodipy Naphthalenediimide Triads

Borondipyrromethene (BDP) naphthalenediimide (NDI) triads (BDP-NDI) and diiodo-BDP derivative (DiiodoBDP-NDI)) were synthesized to study the Förster resonance energy transfer (FRET) and its impact on the triplet state formation and dynamics. In these triads, diiodo-BDP and BDP are the energy donors and NDI is the energy acceptor. Nanosecond transient absorption spectra of triads indicated that triplet state is localized on NDI moiety, either by selective photoexcitation of the Diiodo-BDP or NDI unit. The intersystem crossing (ISC) is attributed to intramolecular heavy atom effect. The triplet state quantum yield was found to be 54% with a lifetime of 38 μs. However, no triplet state is observed for BDP-NDI system either by exciting BDP or NDI unit. Thus, we confirmed that charge recombination does not produce a triplet state. Interestingly, DiiodoBDP-NDI can be used as broadband excitable (500-620 nm) triplet photosensitizer, and high triplet-triplet annihilation (TTA) upconversion quantum yield of Φ_UC = 2.8% was observed with 9,10-bis(phenylethynyl)-anthracene (BPEA) as a triplet acceptor/emitter.

Recent Advances on Functionalized Upconversion Nanoparticles for Detection of Small Molecules and Ions in Biosystems

Significant progress on upconversion-nanoparticle (UCNP)-based probes is witnessed in recent years. Compared with traditional fluorescent probes (e.g., organic dyes, metal complexes, or inorganic quantum dots), UCNPs have many advantages such as non-autofluorescence, high chemical stability, large light-penetration depth, long lifetime, and less damage to samples. This article focuses on recent achievements in the usage of lanthanide-doped UCNPs as efficient probes for biodetection since 2014. The mechanisms of upconversion as well as the luminescence resonance energy transfer process is introduced first, followed by a detailed summary on the recent researches of UCNP-based biodetections including the detection of inorganic ions, gas molecules, reactive oxygen species, and thiols and hydrogen sulfide.

An efficient and sensitive chemosensor based on salicylhydrazide for naked-eye and fluorescent detection of Zn2

We reported here the synthesis of a diarylethene with a 2,4-dihydroxybenzoyl hydrazine moiety (1O) for Zn2+ recognition. The compound is easy to prepare with a high yield up to 85%. Compound 1O can act as a highly selective and specific fluorescent sensor for Zn2+ without interference by other common metal ions. The LOD for Zn2+ detection was determined to be 1.28 × 10-6 mol L-1. Meanwhile, 1O can be used as a naked-eye detector for the Zn2+ ion with an obvious color change from colorless to olive. Based on the fluorescent properties of 1O, we constructed a logic circuit with four inputs of the combinational stimuli of UV/vis light and Zn2+/EDTA, and one output of fluorescence intensity.

Efficient catalytic vicinal diamination of arylene diimides

New substitution patterns for rylene diimides by catalytic diamination.

Hydrazine bridged coumarin-pyrimidine conjugate as a highly selective and sensitive Zn2+ sensor: Spectroscopic unraveling of sensing mechanism with practical application

We report the synthesis and Zn²⁺ sensing of a novel coumarin-hydrazine conjugate 3-{1-[(4, 6-Dimethyl-pyrimidin-2-yl)-hydrazono]-ethyl}-chromen-2-one (3). Compound 3 can act as a neat fluorescent Zn²⁺ sensor by an increment in fluorescence intensity along with an appreciable red shift. Fluorescence enhancement is caused by complexation through cis-trans isomerization process in the presence of Zn²⁺ ion. The practical utility of 3 was demonstrated by successful test kit experiment to detect Zn²⁺ in water under UV-light.

A NIR fluorescent probe for the detection of fluoride ions and its application in in vivo bioimaging

A near-infrared fluorescent probe has been developed, which is available for visualizing exogenous fluoride ions in vitro and in vivo.

Design, Synthesis and Evaluation of Bifunctional Acridinine-Naphthalenediimide Redox-Active Conjugates as Antimalarials

A novel class of bifunctional molecules was synthesized integrating acridine (Ac) and redox-active naphthalenediimide (NDI) scaffolds directly and through a flexible linker (en). We evaluated in vitro antiplasmodial activity, physicochemical properties, and a possible mode of action. Theoretical studies suggested electronic segmentation between the electron-rich Ac and electron-deficient NDI scaffolds. Orthogonal Ac-NDI molecules showed activities in the micromolar to submicromolar range against a chloroquine (CQ)-sensitive strain of human malaria pathogen Plasmodium falciparum (maximum activity, IC₅₀: 0.419 μM). The flexible Ac-en-NDI molecules were most potent and showed activity in the nanomolar range against both CQ-sensitive (with most effective compounds, IC₅₀: 3.65 and 4.33 nM) as well as CQ-resistant (with most effective compounds, IC₅₀: 52.20 and 28.53 nM) strains of P. falciparum. Significantly, with CQ-resistant strains, the activity of the most effective compounds was 1 order of magnitude better than that of standard drug CQ. Ac-en-NDI-conjugated molecules were significantly more potent than the individual NDI and Ac-based molecules. The structure-activity relationship (SAR) suggests that the flexible spacer (en) linking the Ac and NDI scaffolds plays a vital role in exhibiting improved potency. None of the molecules triggered hemolysis in culture, and the most potent compounds did not show cytotoxicity in vitro against mammalian fibroblast NIH3T3 cells at their respective IC₅₀ values. The other significant outcome of this work is that some of the investigated molecules have the potential to affect multiple processes in the parasite including the hemozoin formation in digestive vacuoles (DVs), mitochondrial membrane potential, and the redox homeostasis of the parasite.

Self-assembled vesicle and rod-like aggregates of functionalized perylene diimide: reaction-based near-IR intracellular fluorescent probe for selective detection of palladium

Aggregates ofPS-PDIafter Pd⁰based depropargylation show de-aggregation and near-IR, ratiometric absorbance changes in water and live HeLa cells.

Fluorescent chemosensors manipulated by dual/triple interplaying sensing mechanisms

This review highlights the design strategies and response processes of the fluorescent chemosensors with dual/triple interplaying sensing mechanisms.

Accessing the Long-Lived Triplet Excited States in Transition-Metal Complexes: Molecular Design Rationales and Applications

Transition-metal complex triplet photosensitizers are versatile compounds that have been widely used in photocatalysis, photovoltaics, photodynamic therapy (PDT) and triplet-triplet annihilation (TTA) upconversion. The principal photophysical processes in these applications are the intermolecular energy transfer or electron transfer. One of the major challenges facing these triplet photosensitizers is the short triplet-state lifetime, which is detrimental to the above-mentioned photophysical processes. In order to address this challenge, transition-metal complexes showing long-lived triplet excited states are highly desired. This review article summarizes the development of this fascinating area, including the molecular design rationales, the principal photophysical properties, and the applications of these complexes in PDT and TTA upconversion.

The effect of the regioisomeric naphthalimide acetylide ligands on the photophysical properties of N^N Pt(II) bisacetylide complexes

Two N^N Pt(II) bis(acetylide) complexes Pt-1 and Pt-2 with regioisomeric amino NI acetylide ligands (L-1 and L-2, L-1 = 5-amino-4-ethylnaphthaleneimide; L-2 = 3-amino-4-ethylnaphthaleneimide) were prepared. The photophysical properties of the complexes were studied by steady state and time-resolved spectroscopy. The two complexes with regioisomeric ligands (Pt-1 and Pt-2) show different photophysical properties such as maximal absorption wavelength (485 nm vs. 465 nm), triplet excited state lifetimes (23.7 μs vs. 0.9 μs), and different solvent-polarity dependences of the emission properties. The absorption of the complexes is red-shifted as compared with the previously reported Pt(II) complex containing the 4-ethylnaphthaleneimide ligand. The two complexes with regioisomeric NI ligands were used as triplet photosensitizers for triplet-triplet annihilation (TTA) upconversion; drastically different upconversion quantum yields (15.0% vs. 1.1%) were observed. Our results are useful for designing new visible light-harvesting Pt(II) bisacetylide complexes as triplet photosensitizers which can be used in areas such as photocatalysis, photodynamic therapy and TTA upconversion.

Small bandgap naphthalene diimide copolymers for efficient inorganic–organic hybrid solar cells

The energy level control of efficient inorganic–organic hybrid solar cells induced by using a copolymer was demonstrated.

A simple pincer-type chemosensor for reversible fluorescence turn-on detection of zinc ion at physiological pH range

A dihydrazone based pincer-type chemosensor (Y) which could detect zinc at physiological pH range with reversible fluorescence “Off–On–Off”.

Naphthalene diimides as red fluorescent pH sensors for functional cell imaging

Water-soluble naphthalene diimides have been designed and synthesized as cell permeable pH “turned-on” fluorescent sensors for cellular applications.

Fluorescent, MRI, and colorimetric chemical sensors for the first-row d-block metal ions

Transition metals (d-blocks) are recognized as playing critical roles in biology, and they most often act as cofactors in diverse enzymes; however, improper regulation of transition metal stores is also connected to serious disorders. Therefore, the monitoring and imaging of transition metals are significant for biological research as well as clinical diagnosis. In this article, efforts have been made to review the chemical sensors that have been developed for the detection of the first-row d-block metals (except Cu and Zn): Cr, Mn, Fe, Co, and Ni. We focus on the development of fluorescent sensors (fall into three classes: "turn-off", "turn-on", and ratiometric), colorimetric sensors, and responsive MRI contrast agents for these transition metals (242 references). Future work will be likely to fill in the blanks: (1) sensors for Sc, Ti, and V; (2) MRI sensors for Cr, Mn, Co, Ni; (3) ratiometric fluorescent sensors for Cr(6+), Mn(2+), and Ni(2+), explore new ways of sensing Fe(3+) or Cr(3+) without the proton interference, as well as extend applications of MRI sensors to living systems.