Nanoscale Luminescence Imaging/Detection of Single Particles: State-of-the-Art and Future Prospects.

Single-particle-level measurements, during the reaction, avoid averaging effects that are inherent limitations of conventional ensemble strategies. It allows revealing structure-activity relationships beyond averaged properties by considering crucial particle-selective descriptors including structure/morphology dynamics, intrinsic heterogeneity, and dynamic fluctuations in reactivity (kinetics, mechanisms). In recent years, numerous luminescence (optical) techniques such as chemiluminescence (CL), electrochemiluminescence (ECL), and fluorescence (FL) microscopies have been emerging as dominant tools to achieve such measurements, owing to their diversified spectroscopy principles, noninvasive nature, higher sensitivity, and sufficient spatiotemporal resolution. Correspondingly, state-of-the-art methodologies and tools are being used for probing (real-time, operando, in situ) diverse applications of single particles in sensing, medicine, and catalysis. Herein, we provide a concise and comprehensive perspective on luminescence-based detection and imaging of single particles by putting special emphasis on their basic principles, mechanistic pathways, advances, challenges, and key applications. This Perspective focuses on the development of emission intensities and imaging based individual particle detection. Moreover, several key examples in the areas of sensing, motion, catalysis, energy, materials, and emerging trends in related areas are documented. We finally conclude with the opportunities and remaining challenges to stimulate further developments in this field.

Influence of acceptors on the optical nonlinearity of 5H-4-oxa-1,6,9-trithia-cyclopenta[b]-as-indacene-based chromophores with a push-pull assembly: a DFT approach.

Herein, a series of compounds (TPD1-TPD6) having a D-π-A architecture was quantum chemically designed via the structural modulation of TPR. Quantum chemical calculations were employed to gain a comprehensive insight into the structural and optoelectronic properties of the designed molecules at the M06/6-311G(d,p) level. Interestingly, all the designed chromophores displayed narrow energy gaps (2.123-1.788 eV) and wider absorption spectra (λmax = 833.619-719.709 nm) with a bathochromic shift in comparison to the reference compound (λmax = 749.602 nm and Egap = 3.177 eV). Further, Egap values were utilized to evaluate global reactivity parameters (GRPs), which indicate that all the chromophores expressed higher softness (σ = 0.134-0.559 eV-1) and lower hardness (η = 4.155-4.543 eV) values than the reference chromophore. Efficient charge transfer from donors towards acceptors was noted through FMOs, which was also supported by DOS and TDM analyses. Overall, the TPD3 derivative exhibited a remarkable reduction in the HOMO-LUMO band gap (1.788 eV) with a red shift as λmax = 833.619 nm. Furthermore, it exhibited prominent linear and non-linear characteristics such as µtotal = 24.1731 D, 〈α〉 = 2.89 × 10-22 esu, and ßtotal = 7.24 × 10-27 esu, among all derivatives. The above findings revealed that significant non-linear optical materials could be achieved through structural tailoring with studied efficient acceptors.

Mesoporous Cu-Doped Manganese Oxide Nano Straws for Photocatalytic Degradation of Hazardous Alizarin Red Dye.

The present work reports the photocatalytic degradation of alizarin red (AR) using Cu-doped manganese oxide (MH16-MH20) nanomaterials as catalysts under UV light irradiation. Cu-doped manganese oxides were synthesized by a very facile hydrothermal approach and characterized by energy dispersive X-ray spectroscopy, powder X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller analysis, UV-vis spectroscopy, and photoluminescence techniques. The structural, morphological, and optical characterization revealed that the synthesized compounds are nanoparticles (38.20-54.10 nm), grown in high mesoporous density (constant C > 100), possessing a tetragonal phase, and exhibiting 2.98-3.02 eV band gap energies. Synthesized materials were utilized for photocatalytic AR dye degradation under UV light which was monitored by UV-visible spectroscopy and % AR degradation was calculated at various time intervals from absorption spectra. More than 60% AR degradation at various time intervals was obtained for MH16-MH20 indicating their good catalytic efficiencies for AR removal. However, MH20 was found to be the most efficient catalyst showing more than 84% degradation, hence MH20 was used to investigate the effect of various catalytic doses, AR concentrations, and pH of the medium on degradation. More than 50% AR degradation was obtained for all studied parameters with MH20 whereas the pseudo-first-order kinetic model was found to be the best-fitted kinetic model for AR degradation with k = 0.0015 and R2 = 0.99 indicating a significant correlation between experimental data.

Efficient Synthesis of Imine-Carboxylic Acid Functionalized Compounds: Single Crystal, Hirshfeld Surface and Quantum Chemical Exploration.

Two aminobenzoic acid based crystalline imines (HMBA and DHBA) were synthesized through a condensation reaction of 4-aminobenzoic acid and substituted benzaldehydes. Single-crystal X-ray diffraction was employed for the determination of structures of prepared Schiff bases. The stability of super molecular structures of both molecules was achieved by intramolecular H-bonding accompanied by strong, as well as comparatively weak, intermolecular attractive forces. The comparative analysis of the non-covalent forces in HMBA and DHBA was performed by Hirshfeld surface analysis and an interaction energy study between the molecular pairs. Along with the synthesis, quantum chemical calculations were also accomplished at M06/6-311G (d, p) functional of density functional theory (DFT). The frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP), natural bond orbitals (NBOs), global reactivity parameters (GRPs) and natural population (NPA) analyses were also carried out. The findings of FMOs found that Egap for HMBA was examined to be smaller (3.477 eV) than that of DHBA (3.7933 eV), which indicated a greater charge transference rate in HMBA. Further, the NBO analysis showed the efficient intramolecular charge transfer (ICT), as studied by Hirshfeld surface analysis.

Removal of As(V) and Cr(VI) with Low-Cost Novel Virgin and Iron-Impregnated Banana Peduncle-Activated Carbons.

This work reports the investigation of activated carbons from virgin banana peduncle (ZR1) and iron-impregnated banana peduncle (ZR2) as adsorbents for the removal of As(V) and Cr(VI) ions from aqueous solutions. Both adsorbents were characterized through the point of zero charge, powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray, Brunauer-Emmett-Teller, and Fourier transform infrared spectroscopic techniques. The effects of initial pH, contact time, temperature, and initial concentration on metal ion adsorption were investigated. Adsorbents existed as both crystalline and amorphous species having homogeneous surface cavities and surface area of 749.73 and 369.66 m2/g for ZR1 and ZR2, respectively. The maximum As(V) removal of 79.32 and 69.08% was obtained using ZR1 and ZR2, respectively, whereas the maximum Cr(VI) removal was calculated as 69.73% for ZR1 and 73.78% for ZR2. Kinetic modeling data were found to be best fitted for the pseudo-second-order reaction, and rate constants were calculated. The theoretical adsorption capacities (q m) of ZR1 and ZR2 were calculated through Langmuir and Freundlich models. The maximum As(V) adsorption capacities calculated for ZR1 and ZR2 were 13.33 and 9.066 mg/g, respectively, whereas the maximum Cr(VI) adsorption capacity for both was 13.26 mg/g at 298-328 K. The reaction was endothermic with decreased randomness at the solid-liquid interface due to positive entropy and enthalpy values. All kinetic and thermodynamic parameters showed the feasibility of the adsorption process, and characterization after adsorption indicated ZR1 and ZR2 novel activated carbons as efficient and cheapest biosorbents for removing As(V) and Cr(VI).

Enriching NLO efficacy via designing non-fullerene molecules with the modification of acceptor moieties into ICIF2F: an emerging theoretical approach.

Non-fullerene (NF)-based compounds have attracted much attention as compared to fullerene-based materials because of their promising optoelectronic properties, lower synthetic cost and greater stability. Usually, the end-capped groups have a promising impact in magnifying the nonlinear optical (NLO) characteristics in the non-fullerene molecules. Based on this, a series of new NLO active non-fullerene molecules (NFAD2-NFAD6) have been established. The non-fullerene molecules (NFAD2-NFAD6) were designed by end-capped modification in acceptor moieties of the reference (NFAR1), while donor and π-bridge moieties were kept the same in the entire series. Quantum chemistry-based calculations at the M06/6-311G(d,p) level were done to determine the NLO characteristics and for other supportive analyses. The acceptor and donor moieties were utilized at the opposite terminals of NFAD2-NFAD6, which proved to be an effective approach in tuning the FMO band gap. Overall the results of natural bond orbital (NBO), density of state (DOS) and transition density matrices (TDMs) analyses supported the NLO properties of the designed compounds. Among all the studied compounds, NFAD4 was proven to be the most suitable candidate due to its promising NLO properties, well supported by a lower bandgap of 1.519 eV and a maximum absorption wavelength of 999.550 nm. Therefore, NFAD4 was reported with greater amplitude of dipole polarizability (10.429 e.s.u), average polarizability (2.953 × 10-22 e.s.u), first hyperpolarizability (13.16 × 10-27 e.s.u.) and second hyperpolarizability (2.150 × 10-31 e.s.u.) than other derivatives and NFAR1. Subsequently, the present study depicted the significance of utilizing different non-fullerene (NF)-based acceptor moieties to achieve the promising NLO material. This computational study may lead towards new plausible pathways for researchers to design potent NLO substances for impending hi-tech applications.

Microwave-Assisted Synthesis of (Piperidin-1-yl)quinolin-3-yl)methylene)hydrazinecarbothioamides as Potent Inhibitors of Cholinesterases: A Biochemical and In Silico Approach.

Alzheimer's disease (AD), a progressive neurodegenerative disorder, characterized by central cognitive dysfunction, memory loss, and intellectual decline poses a major public health problem affecting millions of people around the globe. Despite several clinically approved drugs and development of anti-Alzheimer's heterocyclic structural leads, the treatment of AD requires safer hybrid therapeutics with characteristic structural and biochemical properties. In this endeavor, we herein report a microwave-assisted synthesis of a library of quinoline thiosemicarbazones endowed with a piperidine moiety, achieved via the condensation of 6/8-methyl-2-(piperidin-1-yl)quinoline-3-carbaldehydes and (un)substituted thiosemicarbazides. The target N-heterocyclic products were isolated in excellent yields. The structures of all the synthesized compounds were fully established using readily available spectroscopic techniques (FTIR, 1H- and 13C-NMR). Anti-Alzheimer potential of the synthesized heterocyclic compounds was evaluated using acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. The in vitro biochemical assay results revealed several compounds as potent inhibitors of both enzymes. Among them, five compounds exhibited IC50 values less than 20 µM. N-(3-chlorophenyl)-2-((8-methyl-2-(piperidin-1-yl)quinolin-3-yl)methylene)hydrazine carbothioamide emerged as the most potent dual inhibitor of AChE and BChE with IC50 values of 9.68 and 11.59 µM, respectively. Various informative structure-activity relationship (SAR) analyses were also concluded indicating the critical role of substitution pattern on the inhibitory efficacy of the tested derivatives. In vitro results were further validated through molecular docking analysis where interactive behavior of the potent inhibitors within the active pocket of enzymes was established. Quinoline thiosemicarbazones were also tested for their cytotoxicity using MTT assay against HepG2 cells. Among the 26 novel compounds, there were five cytotoxical and 18 showed proliferative properties.

Design, synthesis, crystal structure, in vitro cytotoxicity evaluation, density functional theory calculations and docking studies of 2-(benzamido) benzohydrazide derivatives as potent AChE and BChE inhibitors.

A series of hydrazone derivatives of 2-(benzamido) benzohydrazide was designed, synthesized, and characterized utilizing FTIR, NMR and UV spectroscopic techniques along with mass spectrometry. Compound 10 was also characterized through X-ray crystallography. These synthesized compounds were assessed for their potential as anti-Alzheimer's agents by checking their AChE and BChE inhibition properties by in vitro analysis. The synthesized derivatives were also evaluated for their antioxidant potential along with cytotoxicity studies. The results clearly indicated that dual inhibition of both the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) was achieved by most of the compounds (03-13), showing varying IC50values. Remarkably, compound 06 (IC50 = 0.09 ± 0.05 for AChE and 0.14 ± 0.05 for BChE) and compound 13 (IC50 = 0.11 ± 0.03 for AChE and 0.10 ± 0.06 for BChE) from the series showed IC50 values comparable to the standard donepezil (IC50 = 0.10 ± 0.02 for AChE and 0.14 ± 0.03 for BChE). Moreover, the derivative 11 also exhibited selective inhibition against BChE with IC50 = 0.12 ± 0.09. Meanwhile, compounds 04 and 10 exhibited good anti-oxidant activities, showing % scavenging of 95.06% and 82.55%, respectively. Cytotoxicity studies showed that the synthesized compounds showed cell viability greater than 80%; thus, these compounds can be safely used as drugs. DFT and molecular docking studies also supported the experimental findings.

Synthesis, structure-activity relationship and molecular docking studies of 3-O-flavonol glycosides as cholinesterase inhibitors.

The prime objective of this research work is to prepare readily soluble synthetic analogues of naturally occurring 3-O-flavonol glycosides and then investigate the influence of various substituents on biological properties of synthetic compounds. In this context, a series of varyingly substituted 3-O-flavonol glycosides have been designed, synthesized and characterized efficiently. The structures of synthetic molecules were unambiguously corroborated by IR, 1H, 13C NMR and ESI-MS spectroscopic techniques. The structure of compound 22 was also analyzed by X-ray diffraction analysis. All the synthetic compounds (21-30) were evaluated for in vitro inhibitory potential against cholinesterase enzymes. The results displayed that most of the derivatives were potent inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with varying degree of IC50 values. The experimental results were further encouraged by molecular docking studies in order to explore their binding behavior with the active pocket of AChE and BChE enzymes. The experimental and theoretical results are in parallel with one another.

Synthesis, structure-activity relationship and molecular docking of 3-oxoaurones and 3-thioaurones as acetylcholinesterase and butyrylcholinesterase inhibitors.

The present study describes efficient and facile syntheses of varyingly substituted 3-thioaurones from the corresponding 3-oxoaurones using Lawesson's reagent and phosphorous pentasulfide. In comparison, the latter methodology was proved more convenient, giving higher yields and required short and simple methodology. The structures of synthetic compounds were unambiguously elucidated by IR, MS and NMR spectroscopy. All synthetic compounds were screened for their inhibitory potential against in vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. Molecular docking studies were also performed in order to examine their binding interactions with AChE and BChE human proteins. Both studies revealed that some of these compounds were found to be good inhibitors against AChE and BChE.

Crystal structure of N,N'-(1,2-phenyl-ene)bis-(2-chloro-acetamide).

In the title compound, C10H10Cl2N2O2, the secondary amide groups are differently twisted relative to the benzene ring, with dihedral angles between the respective planes of 21.03 (2) and 81.22 (2)°. In the crystal, the mol-ecules are connected by N-H⋯O and C-H⋯O hydrogen bonds, forming a two-dimensional polymeric network parallel to (001). One of the amide carbonyl O atoms accepts two H atoms in N-H⋯O and C-H⋯O inter-actions, forming an R 2 (2)(6) ring motif.

5-Methyl-1-[(4-methyl-phen-yl)sulfon-yl]-1H-pyrazol-3-yl 4-methyl-benzene-sulfonate.

In the title compound, C(18)H(18)N(2)O(5)S(2), the tolyl rings are oriented at a dihedral angle of 16.15 (11)° with respect to one another. The 5-methyl-1H-pyrazol-3-ol ring is roughly planar (r.m.s. deviation = 0.0231 Å) and subtends angles of 73.82 (8) and 89.85 (8)° with the tolyl rings. In the crystal, very weak π-π inter-actions between tolyl groups, with centroid-centroid distances of 4.1364 (19) and 4.0630 (16) Å, together with a C-H⋯π contact generate a three-dimensional network.

Ethyl (3E)-3-[2-(4-bromo-phenyl-sulfon-yl)hydrazin-1-yl-idene]butano-ate.

The asymmetric unit of title compound, C(12)H(15)BrN(2)O(4)S, contains two mol-ecules (A and B), with slightly different conformations: the bromo-phenyl rings and the SO(2) planes of the sulfonyl groups are oriented at dihedral angles of 50.2 (2) (mol-ecule A) and 58.24 (7)° (mol-ecule B), and the ethyl acetate groups make dihedral angles of 63.99 (19)° (A) and 65.35 (16)° (B) with their bromo-phenyl groups. In the crystal, both mol-ecules exist as inversion dimers linked by pairs of N-H⋯O hydrogen bonds, which generate R(2) (2)(14) loops. The dimers are linked by C-H⋯O inter-actions.

2-[(2-Amino-phen-yl)sulfan-yl]-N-(4-meth-oxy-phen-yl)acetamide.

In the title compound, C(15)H(16)N(2)O(2)S, the dihedral angle between the 4-meth-oxy-aniline and 2-amino-benzene-thiole fragments is 35.60 (9)°. A short intra-molecular N-H⋯S contact leads to an S(5) ring. In the crystal, mol-ecules are consolidated in the form of polymeric chains along [010] as a result of N-H⋯O hydrogen bonds, which generate R(3) (2)(18) and R(4) (3)(22) loops. The polymeric chains are interlinked through C-H⋯O inter-action and complete R(2) (2)(8) ring motifs.

1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-aminium chloride-thio-urea (1/1).

In the title compound, C(11)H(14)N(3)O(+)·Cl(-)·CH(4)N(2)S, the components are connected into a two-dimensional polymeric structure parallel to (001) via N-H⋯Cl, N-H⋯O, N-H⋯S and C-H⋯S hydrogen bonds. The dihedral angle between the phenyl and 2,3-dihydro-1H-pyrazole rings is 44.96 (7)°.

N-{4-[(5-Methyl-isoxazol-3-yl)sulfamo-yl]phen-yl}benzamide.

In the title compound, C(17)H(15)N(3)O(4)S, the five-membered isoxazole ring makes dihedral angles of 80.5 (2) and 81.3 (2)° with the two benzene rings, which form a dihedral angle of 39.81 (18)° with each other. A short intra-molecular C-H⋯O contact occurs. The crystal structure is stabilized by inter-molecular N-H⋯O hydrogen bonds, which generate [001] chains, and further consolidated by weak C-H⋯O inter-actions.

Cobinamides as structural probes in B12-biosynthesis: synthesis and spectroscopic analysis of isomers of Co alpha,Co beta-dicyanocobinamide.

Vitamin B(12) and its coenzyme forms are cobalamins (i.e., cobamides, 'complete' with a 5,6-dimethylbenzimidazole nucleotide base), in which the particular corrinoid moiety of the cobinamides is conjugated to alpha-ribazole-3'-phosphate via a phosphate-diester group. Aside of being provided with their particular reactivity, required for their functions as organometallic cofactors in B(12)-dependent enzymes, the cobalamins also depend upon their specific three-dimensional buildup, to be able to adapt the unique constitution of 'base-on' corrinoids by intramolecular Co-coordination of the nucleotide base. We report rational partial syntheses and detailed spectral analyses of three close cobinamide isomers in their Co(alpha),Co(beta)-dicyano forms: of 13-epicobinamide (also called neocobinamide), of 176(S)-epicobinamide, and of 176-isocobinamide. Neocobinamide was obtained under acidic conditions as a degradation product of vitamin B(12). 176(S)-Epicobinamide and 176-isocobinamide were prepared by condensation of cobyric acid with (2S)-1-aminopropan-2-ol and with 3-aminopropan-1-ol, respectively. Natural cobinamide represents the corrinoid nucleus produced by proper microbial biosynthesis (as intermediate for the further assembly of the 'complete' corrinoid cofactors) or is required in some microorganisms, such as Escherichia coli, as an exogenously supplied unit for further biosynthetic buildup. The three compounds may thus be of use as structural probes for the biosynthetic capacity and tolerance in microorganisms, and (some of them) may serve as substrates as well, for further biosynthetic 'completion' of corrinoid cofactors or their analogues.