Retraction: Hydrogen sulfate ion sensing in aqueous media based on a fused pyrimido benzothiazole derivative.

[This retracts the article DOI: 10.1039/C6RA01980C.].

Synthesis and Evaluation of Biological Activities for a Novel 1,2,3,4-Tetrahydroisoquinoline Conjugate with Dipeptide Derivatives: Insights from Molecular Docking and Molecular Dynamics Simulations.

Peptide synthesis has opened new frontiers in the quest for bioactive molecules with limitless biological applications. This study presents the synthesis of a series of novel isoquinoline dipeptides using advanced spectroscopic techniques for characterization. These compounds were designed with the goal of discovering unexplored biological activities that could contribute to the development of novel pharmaceuticals. We evaluated the biological activities of novel compounds including their antimicrobial, antibacterial, and antifungal properties. The results show promising activity against Escherichia coli and potent antibacterial activity against MTCC 443 and MTCC 1688. Furthermore, these compounds demonstrate strong antifungal activity, outperforming existing standard drugs. Computational binding affinity studies of tetrahydroisoquinoline-conjugated dipeptides against E. coli DNA gyrase displayed significant binding interactions and binding affinity, which are reflected in antimicrobial activities of compounds. Our integrative significant molecular findings from both wet and dry laboratories would help pave a path for the development of antimicrobial therapeutics. The findings suggest that these isoquinoline-conjugated dipeptides could be excellent candidates for drug development, with potential applications in the fight against bacterial and fungal infections. This research represents an exciting step forward in the field of peptide synthesis and its potential to discover novel bioactive molecules with significant implications for human health.

Zinc Chloride-Catalyzed Synthesis of Carbamates: An Application for the Synthesis of the Anti-Alzheimer's Drug Rivastigmine.

Herein, we report a synthetic protocol for the synthesis of carbamates by employing zinc chloride as a catalyst from carbamoyl chlorides and aromatic/aliphatic alcohols. The developed protocol successfully utilizes the gram-scale synthesis of the FDA-approved rivastigmine drug and its derivative. The utility of zinc chloride over other catalysts such as zinc dust and zinc acetate exhibits a 49-87% yield of carbamates.

Stereoselective total synthesis of arachnid harvestmen natural product: (4S,5S)­4-hydroxy-γ-decalactone.

Herein, we described the novel synthetic strategy for the total synthesis of harvestmen natural product (4S,5S)­4-hydroxy-γ-decalactone (minor) from an inexpensive precursor ((R)-2,2-dimethyl-1,3-dioxolane-4-carbaldehyde) with 31% overall yield. Hydroxy-γ-lactones represent a special class of harvestmen exocrine defense compounds. The present convergent synthesis utilizes classical reactions like the Barbier reaction, the Grignard reaction, and the employment of an olefin as a masked carboxylic acid functionality followed by lactone formation as key steps.

Synthetic Approaches toward the Synthesis of Brivaracetam: An Antiepileptic Drug.

Epilepsy is a chronic neurological disorder in the brain, affecting individuals of all age groups. Nearly 1% of the world population is affected by seizure disorder, of which 80% of the patients are observed in underdeveloped and developing countries. The predominant treatment option for epilepsy includes an antiepileptic drug named brivaracetam. This drug emerged as an unusual success of rational drug discovery in clinical development by exhibiting magnificent affinity toward synaptic vesicle glycoprotein as compared to conventional drug levetiracetam and piracetam. Given its efficiency in limiting the progression of epilepsy, this drug has drawn considerable attention of researchers to devise novel routes of its synthesis. The present review encapsulates the reported literature on synthetic strategies for brivaracetam, which will assist medicinal chemists in the further progress of its synthesis.

Fluorescence based miniaturized microfluidic and nanofluidic systems for biomedical applications.

Over the last two decades miniaturized microfluidic and nanofluidic systems with fluorescence setup emerged as a powerful technological platform for diverse biomedical applications. Bio-macromolecules such as nucleic acids and proteins are the core cellular components, their single molecule analysis allow us to understand biological processes, disease creation and progression, and development of novel treatment policies. Design and development of foolproof treatment methods requires rigorously analysis of nucleic acids and proteins such as length quantifications, sequence profiling, sequence mapping, analysis of conformational changes, analysis and recognition of epigenetic changes, and their interactions with other biomolecules. Miniaturized microfluidic and nanofluidic systems with fluorescence spectroscopy enable worldwide researchers to perform nucleic acids and proteins extractions and single molecule analysis from the trace amount of biological samples. In the present chapter we mostly highlighted over one decade applications of microfluidic and nanofluidic systems for single cell micro ribonucleic acid (miRNA) isolation and detection, deoxyribonucleic acid (DNA) mapping, DNA barcoding, identification of epigenetic mark on single DNA molecule, DNA-protein interactions study, protein sensing, protein sequencing, protein binding kinetics and many other applications. We also presented the recently reported microfluidic platform for the preparation of reproducible unisize aggregation induced emission (AIE) active nanomaterials and their biological applications.

Assessing Differential Binding of Aggregation-Induced Emission-Based Luminogens to Host Interacting Surface Proteins of SARS-CoV-2 and Influenza Virus-An in silico Approach.

Early detection of asymptomatic cases through mass screening is essential to constrain the coronavirus disease 2019 (COVID-19) transmission. However, the existing diagnostic strategies are either resource-intensive, time-consuming, or less sensitive, which limits their use in the development of rapid mass screening strategies. There is a clear pressing need for simple, fast, sensitive, and economical diagnostic strategy for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) screening even in resource-limited settings. In the current work, we assessed the in silico feasibility of directly labeling virus surface proteins using fluorogenic molecules with aggregation-induced emission (AIE) property. Here, we present the results for binding of two such AIE probes, phosphonic acid derivative of tetraphenyl ethylene (TPE-P) and sulfonic acid derivative of tetraphenyl ethylene (TPE-S), to SARS-CoV-2 spike protein based on in silico docking studies. Our results show that both TPE-P and TPE-S bind to angiotensin converting enzyme 2 (ACE2)-binding, and N-terminal domains of SARS-CoV-2 spike protein. Molecular dynamic simulations have revealed specific nature of these interactions. We also show that TPE-P and TPE-S bind to hemagglutinin protein of influenza virus, but the interaction strength was found to be different. This difference in interaction strength may affect the emission spectrum of aforementioned AIE probes. Together, these results form a basis for the development of AIE-based diagnostics for differential detection of SARS-CoV-2 and influenza viruses. We believe that these in silico predictions certainly aid in differentially labeling of the both viruses toward the development of rapid detection by AIE probes.

Introduction to aggregation induced emission (AIE) materials.

Idea of introducing aggregation-induced emission (AIE) fundamentally altered the scientific community's perception of classical photophysical processes. Many exciting new possibilities have been coming into light due to the emergence of AIE, such as ability of rapid detection and in analyzing variety of bioactive substances required to monitor the complexed biological processes. This also became a handy tool in elucidating the essential physiological and pathological behaviors of organisms. AIE luminogens (AIEgens) are luminous substances that are either weakly or non-emissive in organic solvents or hydrophobic environment alone, but it gives strong emissive when aggregated along with transforming polarities upon aggregation. Owing to the their outstanding advantages such as rapid turn on/off of high brightness emission, big Stokes shift, excellent photostability, and strong biocompatibility AIEgens have become first choice among bio-inspired probes in biomedicine. In the view of providing basic information on AIE, this chapter give a brief overview of aggregation-caused quenching (ACQ) phenomenon, approaches to transform ACQ to AIE phenomenon, photo-physics of AIE phenomenon, followed by known and reportedly novel AIE active molecules and their biomedical applications.

AIE materials for nucleus imaging.

Emergence of a captivating phenomenon aggregation induced emission (AIE) in the early years of 21st century attracted worldwide researchers. In the last two decades various novel AIE active biocompatible small molecules, macromolecules and polymers have been developed for diverse biomedical applications. Imaging of specific organelle such as mitochondria, ribosomes, nuclei and many others play important in the controlling and successful treatment of various diseases. Conventional luminescent probe molecules used in the imaging at cellular or subcellular level exhibit very weak emission on dispersion or on aggregation in aqueous media. AIE luminogens development is indispensable to overcome the notorious aggregation-caused quenching (ACQ) issue inherited by conventional fluorophores. In the present chapter we mostly highlighted over one decade development of various AIE active luminogens utilized for imaging of cell nucleus, nucleon and nucleic acids. The development of those AIE luminogens exhibits promising results in the early diagnosis of cancer diseases.

Aggregation induced emission materials for tissue imaging.

Aggregation Induced Emission (AIE) has ample opportunities in the sensing and biomedical field. Recently, AIE molecular architecture, AIE nanoparticles (NPs) and AIE conjugated polymer (CP) probes have shown outstanding performance in bioimaging applications. In this chapter, we are summarizing the updated advancement in AIE based molecular, NP and CP probes for tissue imaging. We are focusing in vivo and in vitro tissue imaging with in-depth morphological and molecular information using microscopic techniques. Also, we have summarized various infrared windows for fluorescence microscopic technique to achieve deep penetration and high resolution of tissue images. In addition, future difficulties and challenges of AIEgens in tissue imaging are shortly discussed.

Bis(2-methyl-pyridinium) tetra-chlorido-cuprate(II): synthesis, structure and Hirshfeld surface analysis.

The title compound, (C6H8N)2[CuCl4], crystallizes in the monoclinic space group I2/c. The coordination around the copper atom is a distorted tetra-hedron. The 2-methyl-pyridinium ion (C6H8N+) inter-acts with the tetra-chloro-cuprate anion through N-H⋯Cl and C-H(phen-yl)⋯Cl contacts, forming a hydrogen-bonded layer-like structure. The supra-molecular structure is further stabilized by C-H(meth-yl)⋯Cl inter-actions between the layers.

Conjoint use of Naphthalene Diimide and Fullerene Derivatives to Generate Organic Semiconductors for n-type Organic Thin Film Transistors.

In this paper, we described the design, synthesis, and characterization of two novel naphthalene diimide (NDI) core-based targets modified with terminal fullerene (C60 ) yield - so called S4 and S5, in which NDI bearing 1 and 2 molecules of C60 , respectively. The absorption, electrochemical and thin-film transistor characteristics of the newly developed targets were investigated in detail. Both S4 and S5 displayed broad absorption in the 450-500 nm region, owing to the effect of conjugation due to fullerene functionalities. The electrochemical measurement suggested that the HOMO and the LUMO energy levels can be altered with the number of C60 units. Both S4 and S5 were employed as organic semiconductor materials in n-channel transistors. The thin film transistor based on S4 exhibited superior electron mobility (µe) values ranging from 1.20×10-4 to 3.58×10-4  cm2  V-1 s-1 with a current on-off ratio varying from 102 to 103 in comparison with the performance of S5 based transistor, which exhibited µe ranging from 8.33×10-5 to 2.03×10-4  cm2  V-1 s-1 depending on channel lengths.

Molecular Aggregation of Naphthalene Diimide(NDI) Derivatives in Electron Transport Layers of Inverted Perovskite Solar Cells and Their Influence on the Device Performance.

One of key factors to design applicable electron transport layers (ETLs) for perovskite solar cells is the morphology of ETLs since a good morphology would help to facilitate the carrier transport at two interfaces (perovskite\ETL and ETL\cathode). However, one drawback of most organic ETL small molecules is the internal undesired accumulation, which would cause the formation of inappropriate morphology and rough ETL surface. Here, by elaborately designing the side chains of NDI derivatives, the molecular interaction could be modified to achieve the aggregation in different degrees, which would eventually affect the accumulation of molecules and surface qualities of ETLs. By speculating from the comparison between the absorption spectra of solutions and films, the sequence of extent of molecule interaction and aggregation was built among three NDI derivatives, which is further confirmed by direct evidence of atomic force microscopy (AFM) images. Then, carrier exaction abilities are simply studied by steady-state photoluminescence spectroscopy. The carrier transport process is also discussed based on cyclic voltammetry, time-resolved photoluminescence spectroscopy and mobility. NDIF1 are proven to have the appropriate internal aggregation to smooth the contact with cathode and low series resistance, and a device performance of 15.6 % is achieved. With the ability of preventing the thermal diffusion of Ag towards the perovskite surface due to the strong interaction between molecules, NDIF2 at high concentration shows the highest fill factor (80 %).

Influences of Structural Modification of Naphthalenediimides with Benzothiazole on Organic Field-Effect Transistor and Non-Fullerene Perovskite Solar Cell Characteristics.

Developing air-stable high-performance small organic molecule-based n-type and ambipolar organic field-effect transistors (OFETs) is very important and highly desirable. In this investigation, we designed and synthesized two naphthalenediimide (NDI) derivatives (NDI-BTH1 and NDI-BTH2) and found that introduction of 2-(benzo[d]thiazol-2-yl) acetonitrile groups at the NDI core position gave the lowest unoccupied molecular orbital (LUMO; -4.326 eV) and displayed strong electron affinities, suggesting that NDI-BTH1 might be a promising electron-transporting material (i.e., n-type semiconductor), whereas NDI-BTH2 bearing bis(benzo[d]thiazol-2-yl)methane at the NDI core with a LUMO of -4.243 eV was demonstrated to be an ambipolar material. OFETs based on NDI-BTH1 and NDI-BTH2 have been fabricated, and the electron mobilities of NDI-BTH1 and NDI-BTH2 are 14.00 × 10-5 and 8.64 × 10-4 cm2/V·s, respectively, and the hole mobility of NDI-BTH2 is 1.68 × 10-4 cm2/V·s. Moreover, a difference in NDI-core substituent moieties significantly alters the UV-vis absorption and cyclic voltammetry properties. Thus, we further successfully employed NDI-BTH1 and NDI-BTH2 as electron transport layer (ETL) materials in inverted perovskite solar cells (PSCs). The PSC performance exhibits that NDI-BTH2 as the ETL material gave higher power conversion efficiency as compared to NDI-BTH1, that is, NDI-BTH2 produces 15.4%, while NDI-BTH1 gives 13.7%. The PSC performance is comparable with the results obtained from OFETs. We presume that improvement in solar cell efficiency of NDI-BTH2-based PSCs is due to the well-matched LUMO of NDI-BTH2 toward the conduction band of the perovskite layer, which in turn increase electron extraction and transportation.

Supramolecular super-helix formation via self-assembly of naphthalene diimide functionalised with bile acid derivatives.

The design of chiral chromophores that lead to self-assembly of higher order helical structures is a powerful tool to understand the hierarchical helical structures of molecules of nature. In this work, we present a self-assembled helical super-structure produced via facial stacking of a bile acid bolaamphiphile derivative with a naphthalene diimide core (NDI-DCA), driven by solvophobic effects in THF-H2O solvent mixtures. The chirality of the helical microstructure is directed by the multiple chiral centres in the precursor molecule. The chirality of the hierarchical assemblies was observed using circular dichroism (CD), Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements. We propose that the NDI-DCA super-structures are formed via similar interactions and mechanisms to those observed in biological molecules such as proteins and DNA.

Supramolecular Chiral Helical Ribbons of Tetraphenylethylene-Appended Naphthalenediimide Controlled by Solvent and Induced by l- and d-Alanine Spacers.

Naphthalenediimide-tetraphenylethylene conjugates with an alanine spacer (coded as: NDI-(Ala-TPE)2 ) were synthesized to study the influence of the chirality of the amino acid spacer on its self-assemblies. Here we particularly show that NDI-Ala-TPE bearing l-alanine gives left-handed (M-type) helical superstructure, while d-alanine produces right-handed (P-type) helical ribbons in THF:H2 O at 40:60 % v/v ratio. However, particular aggregates were observed at 20:80 % v/v ratio. Circular dichroism was used to characterise the induction of chirality and the handedness of the helical superstructures, and the microstructure of the self-assembled materials was visualised using scanning electron microscopy while DLS analysis confirmed the formation of particular aggregates in solution.

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.