Correction: Recent progress of core-substituted naphthalenediimides: highlights from 2010.

Correction for 'Recent progress of core-substituted naphthalenediimides: highlights from 2010' by Sheshanath V. Bhosale et al., Org. Biomol. Chem., 2012, 10, 6455-6468, https://doi.org/10.1039/C2OB25798J.

Mimicking the Natural World with Nanoarchitectonics for Self-Assembled Superstructures.

Scientists are often inspired by nature, where naturally occurring morphologies, such as those that resemble animals and plants, can be created in the lab. In this review, we have provided an overview on complex superstructures of animals, plants and some similar shapes from the natural world. We begin this review with a discussion about the formation of various animal-like shapes from small organic molecules and polymers, and then move onto plants and other selected shapes. Literature surveys reveal that most of the polymers studied tend to form micellar structures, with some exceptions. Nevertheless, small organic molecules tend to form not only micellar structures but also other animal shapes such as worms and caterpillars. These superstructures tend to have high surface areas and variable surface morphology, making them very useful material for applications in various field such as catalysis, solar cells, and biomedicine, amongst others.

Tetraphenylethene Derivatives Modulate the RNA Hairpin-G-Quadruplex Conformational Equilibria in Proto-oncogenes.

RNA G-quadruplex (GQs) sequences in 5'-UTRs of certain proto-oncogenes co-localize with hairpin (Hp) forming sequences resulting in intramolecular Hp-GQ conformational equilibria, which is suggested to regulate cancer development and progression. Thus, regulation of Hp-GQ equilibria with small molecules is an attractive but less explored therapeutic approach. Herein, two tetraphenylethene (TPE) derivatives, TPE-Py and TPE-MePy, were synthesized and their effect on Hp-GQ equilibrium was explored. FRET, CD and molecular docking experiments suggest that cationic TPE-MePy shifts the Hp-GQ equilibrium significantly towards the GQ conformer mainly through π-π stacking and van der Waals interactions. In the presence of TPE-MePy, the observed rate constant values for first and second folding steps were increased up to 14.6 and 2.6-fold, respectively. The FRET melting assay showed a strong stabilizing ability of TPE-MePy (ΔTm=4.36 °C). Notably, the unmethylated derivative TPE-Py did not alter the Hp-GQ equilibrium. Subsequently, luciferase assay analysis demonstrated that the TPE-MePy derivatives suppressed the translation efficiency by ∼5.7-fold by shifting the Hp-GQ equilibrium toward GQ conformers in the 5'-UTR of TRF2. Our data suggests that HpGQ equilibria could be selectively targeted with small molecules to modulate translation for therapy.

2H-Pyran-2-one-Functionalized Diketopyrrolopyrrole Dye: Design, Synthesis, and Explosives Sensor.

In this work, a 2H-pyran-2-one-functionalized diketopyrrolopyrrole (DPP) (coded as receptor 1) was designed, synthesized, and fully characterized by various spectroscopic methods. The physical properties of molecular architecture 1 were studied employing theoretical calculations. Receptor 1 was elegantly scrutinized for the sensing of explosive nitroaromatic compounds (NACs). Receptor 1 exhibited detection of nitro explosives, i.e., picric acid (PA), 2,4-dinitrophenol (DNP), and nitrophenol (NP), via the fluorescence quenching mechanism. The Stern-Volmer equation was employed to evaluate the effectiveness of the quenching process. It was found that 1 exhibited a detection limit of about 7.58 × 10-5, 8.35 × 10-5, and 9.05 × 10-5 M toward PA, DNP, and NP, respectively. The influence of interfering metal ions and anions on PA detection was investigated thoroughly. Furthermore, receptor 1-based low-cost fluorescent thin-layer chromatography (TLC) plates were developed for the recognition of PA.

A cationic AIEgen and hexametaphosphate based simple and convenient fluorometric assay for alkaline phosphatase and its inhibitor.

Alkaline phosphatase (ALP) is an important biomarker to diagnose a number of diseases, such as anaemia, hepatobiliary diseases, chronic nephritis, and hypothyroidism. Therefore, the development of simple and convenient assays to monitor levels of ALP is highly desirable. In the present study, an aggregation-induced emission based simple, real-time, and direct fluorescence detection platform has been developed, by using a tetracationic pyridinium derivative of tetraphenylethylene (TPy-TPE) and anionic sodium hexametaphosphate (HMP) as component units. The sensing system, based on the TPy-TPE-HMP assembly, is highly responsive to the ALP dependent disintegration of the TPy-TPE-HMP aggregation complex, owing to HMP digestion by ALP. The sensing platform has an ALP detection limit of 16 mU mL-1 and linear range of 0-742 mU mL-1, respectively. The enzyme kinetic parameters, Km and Vmax, have been evaluated. In addition, the potential applicability of the TPy-TPE-HMP sensing system has also been shown with diluted human serum samples. Moreover, the TPy-TPE-HMP probe system is also useful for screening inhibitors of ALP.

Naphthalene diimides: perspectives and promise.

In this review, we describe the developments in the field of naphthalene diimides (NDIs) from 2016 to the presentday. NDIs are shown to be an increasingly interesting class of molecules due to their electronic properties, large electron deficient aromatic cores and tendency to self-assemble into functional structures. Almost all NDIs possess high electron affinity, good charge carrier mobility, and excellent thermal and oxidative stability, making them promising candidates for applications in organic electronics, photovoltaic devices, and flexible displays. NDIs have also been extensively studied due to their potential real-world uses across a wide variety of applications including supramolecular chemistry, sensing, host-guest complexes for molecular switching devices, such as catenanes and rotaxanes, ion-channels, catalysis, and medicine and as non-fullerene accepters in solar cells. In recent years, NDI research with respect to supramolecular assemblies and mechanoluminescent properties has also gained considerable traction. Thus, this review will assist a wide range of readers and researchers including chemists, physicists, biologists, medicinal chemists and materials scientists in understanding the scope for development and applicability of NDI dyes in their respective fields through a discussion of the main properties of NDI derivatives and of the status of emerging applications.

Flower-Like Superstructures: Structural Features, Applications and Future Perspectives.

Mimicking natural objects such as flowers, is an objective of scientists not only because of their attractive appearance, but also to understand the natural phenomena that underpin real world applications such as drug delivery, enzymatic reactions, electronics, and catalysis, to name few. This article reviews the types, preparation methods, and structural features of flower-like structures along with their key applications in various fields. We discuss the various types of flower-like structures composed of inorganic, organic-inorganic hybrid, inorganic-protein, inorganic-enzyme and organic compositions. We also discuss recent development in flower-like structures prepared by self-assembly approaches. Finally, we conclude our review with the future prospects of flower-like micro-structures in key fields, being biomedicine, sensing and catalysis.

Recent Advances in Aggregation-Induced Emission Active Materials for Sensing of Biologically Important Molecules and Drug Delivery System.

The emergence and development of aggregation induced emission (AIE) have attracted worldwide attention due to its unique photophysical phenomenon and for removing the obstacle of aggregation-caused quenching (ACQ) which is the most detrimental process thereby making AIE an important and promising aspect in various fields of fluorescent material, sensing, bioimaging, optoelectronics, drug delivery system, and theranostics. In this review, we have discussed insights and explored recent advances that are being made in AIE active materials and their application in sensing, biological cell imaging, and drug delivery systems, and, furthermore, we explored AIE active fluorescent material as a building block in supramolecular chemistry. Herein, we focus on various AIE active molecules such as tetraphenylethylene, AIE-active polymer, quantum dots, AIE active metal-organic framework and triphenylamine, not only in terms of their synthetic routes but also we outline their applications. Finally, we summarize our view of the construction and application of AIE-active molecules, which thus inspiring young researchers to explore new ideas, innovations, and develop the field of supramolecular chemistry in years to come.

Tuning Achiral to Chiral Supramolecular Helical Superstructures.

The design and synthesis of achiral organic functional molecules which can assemble into a chiral with selective handedness in the absence of chiral substances is an important in understanding the role chirality plays within these systems. In this review, we described general approaches towards supramolecular chiral molecules the synthesis and self-assembly of achiral molecule to active chiral molecules to investigate controlled supramolecular chiral nanostructures with their photoluminescent properties for rapid, sensitive and selective detection of analytes of choice. Various small molecules have been discussed for achiral to chiral along with induction of chirality and controlled chiral helical structures in detail. We discussed few examples where stimuli used to control the chirality such as temperature, pH etc. Finally, we will also explore on the photo responsive helicity properties of the aggregation induced emission active molecule such as tetraphenylethene conjugates.

Nitrogen-doped carbon dot threads as a "turn-off" fluorescent probe for permanganate ions and its hydrogel hybrid as a naked eye sensor for gold(III) ions.

Highly fluorescent nitrogen-doped carbon dot (NCD) threads were synthesized via simple pyrolysis of citric acid, p-hydroxybenzoic acid, and ammonia. The NCDs show excitation-independent behavior with maximum excitation and emission wavelengths of 350 nm and 435 nm, respectively. The developed probe was used as a turn-off fluorescent sensor for the selective and sensitive determination of permanganate ions in aqueous media. The probe's hydrogel hybrid displayed a beautiful purple color demonstrating its potential as a naked eye sensor for gold detection. The ratiometric sensor exhibited excellent selectivity towards permanganate ions over 27 other ions with a linear range of 510 nM to 2 µM, a detection limit of 170 nM, and a linear regression value (R2) of 0.9944. Similarly, the linear range and limit of detection for gold ions was 3.89-20 µM and 1.285 µM, respectively. The synthesized NCDs were also used as a fluorescent ink as well as a naked eye marker in association with a gold solution demonstrating its potential forensic and anti-counterfeiting applications. Graphical abstract.

Super porous TiO2 photocatalyst: Tailoring the agglomerate porosity into robust structural mesoporosity with enhanced surface area for efficient remediation of azo dye polluted waste water.

The low surface area of TiO2 (50 m2g-1 - Degussa P25) due to randomly oriented, agglomerated nanostructures and charge carrier recombination tendency, has till date been its major limitation for photocatalytic remediation of polluted wastewater. This study presents an innovative process to design super porous TiO2 nanostructures with high effective surface area (238 m2g-1), robust, structurally ordered mesoporosity via a simple sol-gel assisted reflux method. Detailed material characterization studies suggest that the higher degree of intermolecular ligation in novel templates such as butanetetracarboxylic or tricarballylic acid modified titanium hydroxide gels resulted in retainment of the porous structure during the urea assisted combustion synthesis. The induction of robust structural porosity is accompanied by a reduction in pore size distribution, an increase in pore volume leading to significantly higher total surface area of the synthesized TiO2. Detailed investigation of dye adsorption kinetics and photocatalytic degradation kinetics, complemented by kinetic modeling analysis confirmed that the super porous TiO2 with robust mesoporous structure outperforms the rest of synthesized TiO2 catalyst (having only agglomerate porosity) in terms of its superior adsorption capacity, faster diffusion kinetics and photocatalytic activity for degradation of Amaranth dye. Thus, the super porous TiO2 shows promising potential for application in sustainable photocatalytic technology for remediation of wastewater contaminated with azo dyes.

Arginine-Induced Self-Assembly of Protoporphyrin to Obtain Effective Photocatalysts in Aqueous Media Under Visible Light.

The fabrication of controlled supramolecular nanostructures via self-assembly of protoporphyrin IX (PPIX) was studied with enantiomerically pure l-arginine and d-arginine, and we have shown that stoichiometry controlled the morphology formed. The nanostructure morphology was mainly influenced by the delicate balance of π-π stacking interactions between PPIX cores, as well as H-bonding between the deprotonated acidic head group of PPIX with the guanidine head group of arginine. PPIX self-assembled with l-/d-arginine to create rose-like nanoflower structures for four equivalents of arginine that were 5-10 µm in length and 1-4 µm diameter. We employed UV-vis, fluorescence spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FT-IR) techniques to characterize the resulting self-assembled nanostructures. Furthermore, we investigated the catalytic activity of PPIX and arginine co-assembled materials. The fabricated PPIX-arginine nanostructure showed high enhancement of photocatalytic activity through degradation of rhodamine B (RhB) with a decrease in dye concentration of around 78-80% under simulated visible radiation.

A Biomimetic Supramolecular Approach for Charge Transfer between Donor and Acceptor Chromophores with Aggregation-Induced Emission.

Supramolecular assembly of chromophores with inherent resistance to aggregation-induced self-quenching is significant to applications such as chemical sensing and organic light emitting diodes (OLEDs). In this work, molecular gels with aggregation-induced emission (AIE) are constructed by simply coassembling AIE chromophores (electron donor or acceptor) with a nonfluorescent molecular gelator. The binary gels are fluorescent even at very low concentrations of the AIE chromophores, indicating that the rotation of their aromatic cores is restricted in the gel network. In tertiary gels, the fluorescence of the donor chromophore can be efficiently reduced by the acceptor chromophore through a combination of static and dynamic quenching process, via charge transfer from the donor to the acceptor. This work demonstrates a convenient approach to fabricate a supramolecular charge transfer system using an AIE donor and acceptor.

Functional Naphthalene Diimides: Synthesis, Properties, and Applications.

This comprehensive review surveys developments over the past decade in the field of naphthalene diimides (NDIs). It explores their application toward: supramolecular chemistry; sensors; host-guest complexes for molecular switching devices, such as catenanes and rotaxanes; ion-channels by ligand gating; gelators for sensing aromatic systems; catalysis through anion-π interactions; and NDI intercalations with DNA for medicinal applications. We have also explored new designs, synthesis, and progress in the field of core-substituted naphthalene diimides (cNDIs), and their implications in areas such as artificial photosynthesis and solar cell technology. Also presented are some interesting synthetic routes and procedures that can be used toward further development of NDI-bearing compounds for future applications. Finally, we conclude with our views on NDI chemistry for future research endeavors, and we outline what we believe are the key obstacles that need to be overcome for NDIs to see real world applications.

Proton Triggered Colorimetric and Fluorescence Response of a Novel Quinoxaline Compromising a Donor-Acceptor System.

Quinoxaline-based novel acid-responsive probe Q1 was designed on the basis of a conjugated donor-acceptor (D-A) subunit. Q1 shows colorimetric and fluorometric changes through protonation and deprotonation in dichloromethane. With the addition of the trifluoroacetic acid (TFA), UV-vis absorption spectral changes in peak intensity of Q1 was observed. Moreover, the appearance of a new peaks at 284 nm 434 nm in absorption spectra with the addition of TFA indicating protonation of quinoxaline nitrogen and form Q1.H⁺ and Q1.2H⁺. The emission spectra display appearance of new emission peak at 515 nm. The optical property variations were supported by time resolved fluorescence studies. The energy band gap was calculated by employing cyclic voltammetry and density functional calculations. Upon addition of triethylamine (TEA) the fluorescence emission spectral changes of Q1 are found to be reversible. Q1 shows color changes from blue to green in basic and acidic medium, respectively. The paper strip test was developed for making Q1 a colorimetric and fluorometric indicator.

Chiral Assembly of AIE-Active Achiral Molecules: An Odd Effect in Self-Assembly.

The induction of chirality in supramolecular structures through hierarchical self-assembly of achiral compounds and the control of their handedness are closely related to the evolution of life and the chiral amplification found in nature. Herein, it is shown that the combination of achiral tetraphenylethylene, an aggregation-induced emission (AIE)-active luminophore bearing four alkyl chains with an odd or even number of carbon atoms via an amide linkage in the molecular structure allows the induction and control of supramolecular chirality in well-defined helical superstructures by controlling the solvent composition and polarity. In particular, right-handed supramolecular structures were produced for an even number of carbon atoms in the alkyl chains, whereas an odd number led to the assembly of left-handed superstructures. The twisted superstructure was visualised by SEM, and circular dichroism was used to observe chirality in the assembly. These controlled assemblies of AIE-active molecules are of potential practical value, such as templates for helical crystallisation, catalysis and formation of chiral mechanochromic luminescent superstructures.

Arginine-induced porphyrin-based self-assembled nanostructures for photocatalytic applications under simulated sunlight irradiation.

In this communication, we have investigated the arginine-induced fabrication of porphyrin (TCPP)-based supramolecular nanostructures. These self-assembled porphyrin nanostructures such as nanobelts show enhanced photocatalytic activity for the photodegradation of pollutant Rhodamine B under simulated visible-light irradiation.

A pyrene based fluorescent turn-on chemosensor: aggregation-induced emission enhancement and application towards Fe3+ and Fe2+ recognition.

A pyrene-based probe bearing benzothiazole ionophore (Py-BTZ) was synthesised as a "turn-on" fluorescent chemosensor for the detection of Fe3+ and Fe2+ ions in CH3CN : H2O (1 : 1, v/v) solvent mixes. The chemosensor showed optical as well as colorimetric changes towards Fe3+ and Fe2+ ions along with a remarkable enhancement in fluorescence emission. The detection limit of Py-BTZ towards Fe3+ and Fe2+ ions was found to be 2.61 µM and 2.06 µM, respectively. The binding of Py-BTZ with Fe3+ and Fe2+ was determined by using FT-IR experiments. Interestingly, Py-BTZ shows aggregation induced emission enhancement (AIEE) properties in polar solvent mixes such as CH3CN : H2O (1 : 1, v/v).

Graphene-Supported Spinel CuFe2O4 Composites: Novel Adsorbents for Arsenic Removal in Aqueous Media.

A graphene nanoplate-supported spinel CuFe2O4 composite (GNPs/CuFe2O4) was successfully synthesized by using a facile thermal decomposition route. Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Electron Dispersive Spectroscopy (EDS), X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) were employed to characterize the prepared composite. The arsenic adsorption behavior of the GNPs/CuFe2O4 composite was investigated by carrying out batch experiments. Both the Langmuir and Freundlich models were employed to describe the adsorption isotherm, where the sorption kinetics of arsenic adsorption by the composite were found to be pseudo-second order. The selectivity of the adsorbent toward arsenic over common metal ions in water was also demonstrated. Furthermore, the reusability and regeneration of the adsorbent were investigated by an assembled column filter test. The GNPs/CuFe2O4 composite exhibited significant, fast adsorption of arsenic over a wide range of solution pHs with exceptional durability, selectivity, and recyclability, which could make this composite a very promising candidate for effective removal of arsenic from aqueous solution. The highly sensitive adsorption of the material toward arsenic could be potentially employed for arsenic sensing.

Pyrene-Phosphonate Conjugate: Aggregation-Induced Enhanced Emission, and Selective Fe3+ Ions Sensing Properties.

A new pyrene-phosphonate colorimetric receptor 1 has been designed and synthesized in a one-step process via amide bond formation between pyrene butyric acid chloride and phosphonate-appended aniline. The pyrene-phosphonate receptor 1 showed aggregation-induced enhanced emission (AIEE) properties in water/acetonitrile (ACN) solutions. Dynamic light scattering (DLS) characterization revealed that the aggregates of receptor 1 at 80% water fraction have an average size of ≈142 nm. Field emission scanning electron microscopy (FE-SEM) analysis confirmed the formation of spherical aggregates upon solvent evaporation. The sensing properties of receptor 1 were investigated by UV-vis, fluorescence emission spectroscopy, and other optical methods. Among the tested metal ions, receptor 1 is capable of recognizing the Fe3+ ion selectively. The changes in spectral measurements were explained on the basis of complex formation. The composition of receptor 1 and Fe3+ ions was determined by using Job's plot and found to be 1:1. The receptor 1-Fe3+ complex showed a reversible UV-vis response in the presence of EDTA.