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A visible light‐mediated oxidative coupling of hydrazides into corresponding N,N'‐ diacylhydrazines using a commercially available and low‐cost metal‐free photocatalyst was reported. The versatility of the reaction has been demonstrated across a broad spectrum of functional groups present in hydrazides. Interestingly, the developed methodology was utilized to synthesize symmetrical and unsymmetrical N,N'‐diacylhydrazines in moderate yields. Density Functional Theory (DFT) calculations, along with control reactions and quenching studies, provide evidence supporting the proposed mechanism, favoring the photoredox pathway. Additionally, NMR and UV‐Vis studies confirmed the generation of H2O2 in the reaction mixture, which strengthens the proposed mechanism. To our knowledge, this is the first report for the conversion of hydrazides to N,N'‐diacylhydrazines using 9‐fluorenone as an organic photoredox catalyst. [ABSTRACT FROM AUTHOR]

The 2,7‐fluorenone‐linked bis(6‐imidazo[1,5‐a]pyridinium) salt H2‐1(PF6)2 reacts with Ag2O in CH3CN to yield the [2]catenane [Ag4(1)4](PF6)4. The [2]catenane rearranges in DMF to yield two metallamacrocycles [Ag2(1)2](PF6)2. 2,7‐Fluorenone‐bridged bis‐(imidazolium) salts H2‐L(PF6)2 (L=2 a, 2 b) react with Ag2O in CH3CN to yield metallamacrocycles [Ag2(L)2](PF6)2 with interplanar distances between the fluorenone rings too small for [2]catenane formation. Intra‐ and intermolecular π⋅⋅⋅π interactions between the fluorenone groups were observed by X‐ray crystallography. The strongly kinked 2,7‐fluorenone bridged bis(5‐imidazo[1,5‐a]pyridinium) salt H2‐4(PF6)2 reacts with Ag2O to yield [Ag2(4)(CN)](PF6), while the tetranuclear assembly [Ag4(4)2(CO3)](PF6)2 was obtained in the presence of K2CO3. [ABSTRACT FROM AUTHOR]

This paper reports the construction of racemic and enantiopure (D‐ and L‐) fluorene and fluorenone‐based novel unnatural amino acid derivatives. The Pd(II)‐catalyzed bidentate directing group‐aided arylation of prochiral β‐C(sp3)‐H bonds in racemic, enantiopure carboxamides of amino acids with iodofluorenes was reported. The construction of novel examples of fluorene and fluorenone motifs containing amino acids comprising of norvaline, leucine, phenylalanine, norleucine, 2‐aminooctanoic acid derivatives having the anti‐stereochemistry (with good enantiopurity) was accomplished. The construction of bis fluorenyl alanine scaffolds and fluorenyl motif‐containing non‐α‐amino acid (aminoalkanoic acid) derivatives was also reported. Examples of removal of the directing group (8‐aminoquinoline) and phthalimide‐protecting group present in the fluorenyl‐based unnatural amino acid derivatives have been shown. Accordingly, fluorene motif‐based amino acid esters and free amino group‐containing unnatural amino acid derivatives were synthesized. The stereochemistry of the major (anti) diastereomers obtained via the prochiral β‐C(sp3)‐H arylation of norvaline, leucine, phenylalanine, norleucine, 2‐aminooctanoic acid derivatives was ascertained from the X‐ray structure of a representative compound. Fluorene‐ and fluorenone‐based motifs are vital skeletons in materials and medicinal chemistry research. Accordingly, this work is a contribution towards enriching the library of fluorene and fluorenone unnatural amino acid scaffolds. [ABSTRACT FROM AUTHOR]

Photoconductive materials have important application value because of their special property of variable conductivity under light. Due to the limitations of the construction of single-component photoconductive materials, photoconductive materials are often combined with organic polymer materials to prepare composite materials. In this work, a series of photoconductive nanofibers array films (PNAFs) are prepared by combining polyvinyl pyrrolidone (PVP), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyoxyethylene (PEO) + PMMA, and polyvinylidene fluoride (PVDF) + PVP polymer substrates with 2,7-dibromo-9-fluorenone (DF), respectively, innovative combination of photoconductive materials with different polymers. PNAFs have excellent green fluorescence and electrical conductivity under light irradiation but no performance under no light irradiation. The transformation of performance can be achieved by the presence or absence of lighting. The effects of the combination of different substrates and photoconductive materials on the conductivity and fluorescent properties of the products are investigated for the first time. This provides ideas for the research of photoconductive materials in the future, and suitable combinations of inorganic and organic substances can be selected according to actual needs. [ABSTRACT FROM AUTHOR]

To obtain novel boron liquid crystals, we successfully combined MIDA boronates with chromophoric fluorene and fluorenone mesogenic units and studied the influence of alkoxy versus alkyl side chains by differential scanning calorimetry (DSC), polarising optical microscopy (POM) and X-ray diffraction (XRD). The fluorenes showed broader temperature ranges of the SmA phase compared to their fluorenone counterparts. By replacing the alkoxy side chains with alkyl side chains, the mesophase ranges could be significantly enlarged and the thermal stability increased. [ABSTRACT FROM AUTHOR]

Oxygen activation is a critical step in heterogeneous oxidative processes, particularly in catalytic, electrolytic, and pharmaceutical applications. Among the various catalysts available for photocatalytic O2 activation, homogeneous aryl ketones are at the forefront. To avoid the degradation and deactivation of aryl ketones, 9‐fluorenone‐based porous organic polymers were designed and regulated by doping them with co‐monomers. The obtained heterogeneous photocatalyst showed good performance in O2 activation, and its performance was better than that of homogeneous 9‐fluorenone. The obtained heterogeneous photocatalyst showed good reusability. We believe that the presented method and findings represent an important step toward designing catalysts tailored for specific tasks. [ABSTRACT FROM AUTHOR]

Cycloparaphenylenes (CPPs) are the smallest possible armchair carbon nanotubes, the properties of which strongly depend on their ring size. They can be further tuned by either peripheral functionalization or by replacing phenylene rings for other aromatic units. Here we show how four novel donor–acceptor chromophores were obtained by incorporating fluorenone or 2‐(9H‐fluoren‐9‐ylidene)malononitrile into the loops of two differently sized CPPs. Synthetically, we managed to perform late‐stage functionalization of the fluorenone‐based rings by high‐yielding Knoevenagel condensations. The structures were confirmed by X‐ray crystallographic analyses, which revealed that replacing a phenylene for a fused‐ring‐system acceptor introduces additional strain. The donor–acceptor characters of the CPPs were supported by absorption and fluorescence spectroscopic studies, electrochemical studies (displaying the CPPs as multi‐redox systems undergoing reversible or quasi‐reversible redox events), as well as by computations. The oligophenylene parts were found to comprise the electron donor units of the macrocycles and the fluorenone parts the acceptor units. [ABSTRACT FROM AUTHOR]

In this study, a naked‐eye colorimetric probe (L) was synthesized by condensation reaction of 9‐fluorenone with 2‐thiophene carboxylic acid hydrazide and characterized by various analytical techniques. The presence of O, N, and S heteroatoms in L would modulate the hard and soft characters, which is responsible for selective complexation of Cu2+ and fluorenone act as signalling unit. The sensing ability of L was studied with various metal ions by colorimetric, test paper strip, and UV‐visible spectrophotometry in DMSO: H2O (6 : 4, v/v). The colorless solution L turned green upon interacting with Cu2+ ions, while other ions did not change color. The probe L exhibits an absorbance band at 354 nm; upon interaction with Cu2+ ions, it exhibits a band at 413 nm due to ligand‐to‐metal charge transfer (LMCT). The probe L binds Cu2+ in a 2 : 1 stoichiometric ratio with an association constant of 3.76×107 M−2, established using Job's and BindFit methods. Further, binding mechanism is supported by EPR and ESI studies. The probe L can work in the pH range of 3.0 to 7.5 and detect as low as 93 nM (6 ppb) by spectrophotometry. Probe L demonstrates a promising potential for detecting Cu2+ ions in the semi‐aqueous medium. [ABSTRACT FROM AUTHOR]

A novel photocatalytic cyclization reaction was developed for the synthesis of quinazolinones from o-aminobenzamides and in-situ generated aldehydes from alcohols using 9-fluorenone as the photocatalyst through a "one-pot" process. Furthermore, alcohols are perfect alternatives to aldehydes due to some unique advantages, such as being green, less toxic, available, and economical. The present protocol showed good tolerance for various substrates and could afford a range of quinazolinones (29 examples) up to 91% under ambient conditions. [ABSTRACT FROM AUTHOR]

Due to the high exposure toxicity and individual variability of polycyclic aromatic hydrocarbons (PAHs), it is difficult to accurately characterize the actual exposure of exposed individuals through external exposure detection. In this study, the monohydroxyl metabolites of naphthalene, phenanthrene, pyrene, and 9-fluorenone were identified in the urine of low-dose PAH-exposed individuals based on ultra-performance liquid chromatography–high-resolution mass spectrometry (UPLC-HRMS), and their concentrations were monitored for 15 consecutive days after exposure. The results showed that the metabolite concentrations of naphthalene, phenanthrene, and pyrene were basically the same, and all of them reached the maximum value at day 8. In contrast, the metabolite of 9-fluorenone reached its maximum value on day 2. This study showed that the four metabolites were strongly correlated with their parent PAH exposure, with a wide detection window, and their assays were specific, sensitive, and reliable, while the sampling difficulty was low, so the four hydroxylated PAHs may be potential low-dose biomarkers of PAH internal exposure. This study will provide methodological and data support for further health risk studies involving internal exposure to organic pollutants such as PAHs. [ABSTRACT FROM AUTHOR]

Two new fluorescent dyes, (E)-1-(2-hydroxybenzylidene)-2-(9H-fluoren-9-ylidene)hydrazine (FIIS) and (E)-1-(2-hydroxynaphtylidene)-2-(9H-fluoren-9-ylidene)hydrazine (FIIN), were synthesized. Photophysical properties were obtained from electronic absorption and emission spectra in DMF solution. The obtained spectra showed large Stokes shifts (∆λ > 80 nm) that could be beneficial in the biological fluorescence imaging domain. Electrochemical properties were studied by cyclic voltammetry in a Bu4NBF4 (0.1 M)/MeCN organic solution. A theoretical study was carried out using the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT) methods, explaining experimental findings and providing a theoretical support for further investigations. The calculations results were in harmony with experimental ones and were used to estimate the global reactivity descriptors of our molecules. Molecular docking calculations conducted against tyrosinase revealed that the two compounds had lower binding energies (− 7.3 and − 8.4 kcal/mol) compared to the used standard, kojic acid (− 5.4 kcal/mol). This suggests them as possible inhibitors of tyrosinase activity. FIIS and FIIN were screened through Lipinski's rule of five via the SwissADME server to assess their absorption, distribution, metabolism, and excretion properties. It was found that both molecules fulfilled the related criteria. [ABSTRACT FROM AUTHOR]

Luminescent materials with tunable emission are becoming increasingly desirable as we move towards needing efficient Light Emitting Diodes (LEDs) for displays. Key to developing better displays is the advancement of strategies for rationally designing emissive materials that are tunable and efficient. We report a series of emissive metal‐organic frameworks (MOFs) generated using BUT‐10 (BUT: Beijing University of Technology) that emits green light with λmax at 525 nm. Post‐synthetic reduction of the ketone on the fluorenone ligand in BUT‐10 generates new materials, BUT‐10‐M and BUT‐10‐R. The emission for BUT‐10‐R is hypsochromically‐shifted by 113 nm. Multivariate BUT‐10‐M structures demonstrate emission with two maxima corresponding to the emission of both fluorenol and fluorenone moieties present in their structures. Our study represents a novel post‐synthetic ligand reduction strategy for producing emissive MOFs with tunable emission ranging from green, white‐blue to deep blue. [ABSTRACT FROM AUTHOR]

A 2,2′-bipyridyl calcium complex based on a tridentate ligand [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]Ca(bipy)(THF) (1) was prepared by the reduction of {[CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]CaI(THF)}2 with potassium graphite in the presence of 2,2′-bipyridine (bipy). Complex 1 is a good Ca(I)synthon, as shown by its reactivity with I2, PhCH2SSCH2Ph, PhCH2SeSeCH2Ph and 9-fluorenone, yielding the calcium iodide complex [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]CaI(bipy) (2), calcium thiolate [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]Ca(SCH2Ph)(bipy) (3), calcium selenolate [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]Ca(SeCH2Ph)(bipy) (4), and calcium ketyl complex [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]Ca[O-(9-C13H8˙)](bipy)·2THF (5·2THF), respectively. In addition, reactions of complex 5 with CS2, CH2＝CHCH2Br and PhCH2Br give the corresponding dimeric bis(thiolate) complex {[S2CC(CMe(NAr))C(Me)NCH2CH2NMe2]Ca(DME)}2 (6), dimeric calcium bromide complex {[(9-CH2＝CHCH2-C13H8-9)-O]CaBr(THF)(bipy)}2 (7) and {[(9-C6H5CH2-C13H8-9)-O]CaBr[O-(9-C13H8)](bipy)}2 (8). These results demonstrated that the calcium ketyl complex 5 can also be employed as a single-electron transfer reagent. All the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses. [ABSTRACT FROM AUTHOR]

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Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are toxic and carcinogenic compounds widely present in the natural environment, posing a serious threat to the environment and human health. However, the removal of OPAHs is mainly hindered by their low water solubility. Cyclodextrins (CDs) are frequently used to form inclusion complexes (ICs) with hydrophobic molecules to improve their solubility. In this study, we investigated the solubility enhancement ability of different CDs on 9-fluorenone, a common OPAH, through phase solubility experiments. We successfully prepared three solid ICs of 9-fluorenone with β-, hydroxypropyl-β-(HP-β-) and sulfobutylether-β-CD (SBE-β-CD) using the cooling crystallization method for the first time and characterized them via powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, etc. Molecular dynamics simulations were employed to investigate the binding modes and stable configurations of the ICs in the liquid phase and to explore the factors affecting their solubility enhancement ability. The results showed that all the CDs had a solubility enhancement effect on 9-fluorenone, with SBE-β-CD displaying the strongest effect, increasing the solubility of 9-fluorenone by 146 times. HP-β-CD, β-CD, α-CD, and γ-CD followed in decreasing order. Moreover, 9-fluorenone formed a ratio of 1:1 ICs to CDs. In addition, the interaction energy between SBE-β-CD and 9-fluorenone was the lowest among the CDs, which further validated the results of the phase solubility experiments from a theoretical perspective. Overall, this study provides a green method for the removal of 9-fluorenone pollutants in the environment and is expected to be applied to the removal and environmental remediation of other OPAHs. [ABSTRACT FROM AUTHOR]

A novel one-pot N–S bond cleavage of tosyl hydrazone derivatives of isatin and fluorenone by (het)arynes was discovered. The reaction produced diverse diaryl and heteroaryl-aryl sulfones as major products and diazomethyledenes of isatin/fluorenone or spiro[indazole-3,3′-indolin]-2′-one via [3+2]-dipolar cycloaddition reaction between diazomethyledenes of isatin/fluorenone and arynes, and N-phenyl benzenesulfonohydrazides via direct N-arylation by arynes. It has been established that the distribution of products depends on the nature of arynes and the source of fluoride ions and substrates. The structure of the products was established by spectroscopic and XRD methods. By invoking the dual reactivity of arynes as nucleophiles and electrophiles, two plausible reaction mechanisms for the formation of all the products are provided. [ABSTRACT FROM AUTHOR]

A novel fluorenone derived Schiff base chemosensor (1) has been synthesized as a colorimetric sensor for fluoride (F−) ions in CH3CN and characterized by various analytical techniques. The chemosensor 1 perceived high selectivity for F− ion detection in the presence of other anions along with naked eye color change from yellow to orange‐red with quantitative detection limit of 900 nM. The UV‐vis changes, density functional theoretical (DFT) calculations and 1H NMR titration studies pointed to F− ion induced deprotonation of −OH of sensor 1 that has been proposed to be responsible for the observed absorption as well as color changes. The sensor 1 has also been efficiently applied for the solid state concentration dependent naked eye detection of F− ions in the form of filter paper strips and smartphone applications. The in‐situ generated 1‐F− complex was further utilized for cascade recognition of calcium gluconate (CG). The reversible and reproducible changes produced by the addition of F− ions and CG enabled 1 to be used as "INHIBIT" molecular logic system and "SET/RESET" memorized device at the molecular level. [ABSTRACT FROM AUTHOR]

An efficient, one‐step method has been used to access a variety of substituted indenones in a regiospecific manner by Grignard addition to indene‐1,3‐dione. This method provides straightforward access to natural products such as neo‐lignans and isoampelopsin D analogues. Moreover, diallyl indenones have been synthesized and employed as ring‐closing metathesis (RCM) precursors for the facile synthesis of substituted fluorenone derivatives through an RCM‐aromatization sequence. [ABSTRACT FROM AUTHOR]

Heterogeneous macrocycles with fluorenone and fluorenol functional groups are synthesized by two facile methods involving post-modification on the macrocycles and one-pot co-cyclization from different monomers. Significantly, benefitting from the well-matched absorption/emission spectra and close distance of fluorenone/fluorenol moieties, the obtained heterogeneous macrocycles exhibit intriguing intramolecular energy transfer (ET) and fluorescence enhancement. [ABSTRACT FROM AUTHOR]

This study describes the development of a series of strong electron-deficient acceptor units, namely, fluorenone imide (FOI) and its derivatives, functionalized with various electron-withdrawing groups, which are developed via functionalization of the fluorenone unit with an imide group and then systematic variation of the attached electron-withdrawing groups at the bridgehead benzylic position. [ABSTRACT FROM AUTHOR]

Three benzofluorenone derivatives, benzo[a]fluorenone (BFA), benzo[b]fluorenone (BFB), and benzo[c]fluorenone (BFC), were studied spectroscopically in comparison with 9‐fluorenone (9‐FL) in solvents of various polarities to better understand the solvatochromism and excited‐state deactivation processes in these molecules. Time‐resolved transient absorption, steady‐state absorption, emission, and fluorescence lifetimes were utilized in this endeavor. Differences in the excited‐state deactivation processes are observed which can be attributed to the varied characters of the singlet and triplet excited states in these molecules which arise from structural differences and solvatochromism. The main deactivation pathway in all of the studied molecules was internal conversion (IC). Ignoring IC, the competition between intersystem crossing (ISC) and fluorescence is highly dependent on the molecule‐solvent system. BFA was found to decay mainly via a triplet state in cyclohexane but via fluorescence in ethyl acetate and acetonitrile. BFB was found to decay via both ISC to a triplet state and emission from the singlet state in cyclohexane but only via ISC in ethyl acetate and acetonitrile. Only emission from the singlet state was observed in BFC in all solvents. [ABSTRACT FROM AUTHOR]

Organic polar crystalline materials, featuring the merits of lightweight, flexibility, and low fabrication costs, are emerging as promising alternatives for inorganic ferroelectrics, but so far, they are not competitive. The main reasons are the moderate polar properties of such materials and the fact that the temperature of the phase transition from polar to nonpolar states (Curie point) is typically located near room temperature. The organic molecular crystal of the fluorenone derivative 2,7‐diphenyl‐9H‐fluorene‐9‐one (DPFO) is demonstrated to feature robust high‐temperature piezo‐ and ferro‐electric properties, with a relatively high local piezoelectric coefficient (d33) of ≈120 pm V−1. The origin of the strong piezoelectricity is attributed to the presence of intrinsic domain structures in the DPFO microfiber crystals, originating from intramolecular co‐operation between the central fluorenone backbone and the external phenyl rings that are found stable up to 423 K. Moreover, this intramolecular co‐operation and the corresponding polar properties are found to depend on the thickness of the DPFO microfiber, resulting in a change from ferroelectric (<0.5 µm) to piezoelectric (≥0.5 µm) behavior. Considering the low cost and flexible production of such fluorenone‐based organic lead‐free ferroelectrics, this is a very promising strategy toward technological applications in electromechanical actuators, sensors, energy harvesters, and non‐volatile memory cells. [ABSTRACT FROM AUTHOR]

This work represents a simple and efficient synthesis of novel 2-amino-N'-(9H-fluoren-9-ylidene)-hexahydroquinoline-3-carbohydrazide derivatives via the multi-component reaction of diverse anilines, dimedone, 9-fluorenone, cyanoacetohydrazide, and aromatic aldehydes in the presence of piperidine as a catalyst. The proposed approach has some advantages as good yields, green medium, short reaction times, simple work-up, and purification process with no chromatographic technique compared with other methods. Supplemental data for this article is available online at at the publisher's website. [ABSTRACT FROM AUTHOR]

In this paper, two novel D-A-D type molecules (EBZFO1 and TBZFO2), which consisting of 7 H-benzo[ c ]fluoren-7-one as electron acceptor (A) unit, 3,4-ethylenedioxythiophene (EDOT) and thiophene (Th) as the terminal donor (D) units, were designed and synthesized. Afterwards, the corresponding D-A polymers of P(EBZFO1) and P(TBZFO2) were prepared by electrochemical deposition method. The electrochemical behavior of the monomers, electrochemical, and electrochromic properties of the D-A polymers were comparatively studied. Although both of the monomers have lower onset oxidation potentials (1.0 V/1.2 V) and good adherence on the electrode, the redox stability of their polymers was very different. P(EBZFO1) displayed much better redox stability (remaining 78.4 % electroactivity after 1000 cycles), good optical stability (2 % reduction in optical contrast after 1500 s), and stable optical memory, while P(TBZFO2) remained inferior redox stability with only 8.82 % of its original electroactivity was retained after 1000 cycles. As a result, higher optical band gap of P(TBZFO2) (1.65 eV) displayed much worse electrochromic performances with the normal optical contrast (11.4 %∼46 %) and relatively slow switching time (2.5–3.8 s). By contrast, P(EBZFO1) (band gap: 1.55 eV) showed favorable optical contrast (15.8 %) at 1100 nm with a very fast response time of 0.24 s, and decent coloration efficiency (228.8 cm2 C−1 at 433 nm). From these results, P(EBZFO1) can further render an appropriate electrochromic material for the smart windows or displays. [Display omitted] • Two fluorenone derivative acceptor units-based D-A type polymer precursors were synthesized. • Different donor units caused outstanding effects on the photophysical properties of the precursors and its polymers. • EBZFO1 and P(EBZFO1) exhibited much lower onset oxidation potentials. • Lower band gap P(EBZFO1) shown favorable redox activity and better redox stability. • P(EBZFO1) has high coloration efficiency, short response time, and good optical memory behavior. [ABSTRACT FROM AUTHOR]

Improving carrier transport rate and suppressing carrier recombination are two huge challenges in the photocatalytic applications of covalent organic frameworks (COFs)-based semiconductors. In this study, we propose a strategy to enhance carrier transport efficiency by regulating the local microenvironment of the electronic characteristics in the acceptors through structural modification. Three different functional group-modified fluorenone-based COFs were successfully synthesized through precise design. The results demonstrate that the photocatalytic hydrogen evolution activities of COFs modified with electron-donating functional groups are significantly higher than that of COFs modified by electron-withdrawing functional groups. Specifically, the photocatalytic hydrogen evolution performance of phenyl-modified FOOPh-COF could reach 228.5 mmol h−1g−1, which is 11.8 times higher than that of Br atom-modified FOOBr-COF (19.3 mmol h−1g−1). Femtosecond time-resolved transient absorption spectroscopy (fs-TAS) results reveal that introducing phenyl groups into the acceptor significantly enhances its inhibitory effect on the carrier recombination. Density functional theory calculations further prove that modifying the acceptor by electron-donating functional groups can achieve the increased electron density in the C O active center. The electrons in the C O region in the phenyl-modified fluorenone structure are more enriched and delocalized, which can enhance the speed of electron migration, shorten the migration distance, and inhibit carrier recombination. After loading Pt, it has the lowest H* adsorption-free energy among three samples. This work clarifies the importance of the functionalization modification of COFs' acceptors in regulating the local electronic environment and further provides new insights into the structure–activity relationship of fluorenone-based COF-based photocatalysts. [Display omitted] • The electron-donating groups in COF can boost exciton dissociation and carrier separation. • The relationships between local electrons in COFs and the photocatalytic activity were revealed. • The improved charge separation and hydrogen-evolution kinetics were confirmed. • Ultrahigh photocatalytic H 2 evolution has been achieved by reasonable structural regulation. [ABSTRACT FROM AUTHOR]

Combined density functional theory and multireference configuration interaction methods including spin‐orbit coupling and spin‐vibronic interactions have been used to elucidate the photophysical pathways of benzophenone (BP), anthrone (A) and fluorenone (FL). Our results reveal that the slower S1(1nπ*) T1(3ππ*) passage of FL in the gas phase, as compared to BP and A, originates from the different electronic structures of the T1(3ππ*) states in these compounds and is not related to the planarity of the nuclear arrangement. Temperature effects on the rate constants of intersystem‐crossing (ISC), reverse ISC (rISC) and fluorescence have been investigated for FL in solvents of different polarity. Experimentally observed trends for rate constants are well reproduced. A nearly temperature‐ and solvent‐independent, slower down‐hill ISC component is attributed to the El‐Sayed‐forbidden S1(1ππ*) T1(3ππ*) transition in these environments. The faster El‐Sayed‐allowed S1(1ππ*) T2(3nπ*) ISC requires thermal activation in tetrahydrofuran and acetonitrile solution so that fluorescence may compete against triplet formation. In cyclohexane solution, S1(1ππ*) and T2(3nπ*) are nearly degenerate according to our calculations. Hence S1 T2 ISC and S1T2 rISC have similar rate constants. If T2 T1 internal conversion could be slowed down by deuteration or perfluorination, for example, FL‐derivatives might show delayed fluorescence. [ABSTRACT FROM AUTHOR]

Attempts to stabilise a TmII metal centre with the bulky β-diketiminate ligand HC[C(Me)=N(DIPP)]2 (BDI) failed (DIPP, 2,6-diisopropylphenyl). Reaction of TmI2 and 2 equiv. (BDI)K gave the TmIII complex (BDI)(BDI-H)Tm (1) in which (BDI-H)2− is a doubly deprotonated ligand. However, following the same route, (BDI)2Sm (2) was isolated in 48% crystalline yield. Complex 2 is highly soluble in aromatic solvents or alkanes and was reacted with various reagents like phenazine, PhSSPh, O2, NO, cuminil and fluorenone. This led to isolation and structural characterisation of the following SmIII complexes: [(BDI)2Sm]2(μ-phenazine) (3), [(BDI)Sm(SPh)(μ-SPh)]2 (4), (BDI)(BDI-H)Sm (5a), (BDI)2Sm(OC13H8) (6) and (BDI)2Sm(NO2) (7). The rich redox reactivity of (BDI)2Sm (2) and its very high solubility in apolar solvents like hexane make it an attractive reducing agent in synthesis. The structure and synthesis of a low-valent β-diketiminate SmII complex are reported and its redox reactivity with various reagents was investigated. With a rich redox reactivity, the SmII complex is an easy-to-prepare, attractive reducing agent that is soluble in apolar organic solvents. [ABSTRACT FROM AUTHOR]

The development of high‐performance n‐type polymer semiconductors is powered by the design and synthesis of electron‐deficient building blocks with optimized physicochemical properties. By meticulously installing an imide group onto fluorene and its cyanated derivative, we report here two very electron‐deficient building blocks, imide‐functionalized fluorenone (FOI) and its cyanated derivative (FCNI), both featuring a deep‐lying lowest unoccupied molecular orbital energy level down to −4.05 eV and highly coplanar framework, endowing them ideal units for constructing n‐type polymers. Thus, a series of polymers are built from them, exhibiting unipolar n‐type transport character with a highest electron mobility of 0.11 cm2 V−1 s−1. Hence, FOI and FCNI offer a remarkable platform for accessing high‐performance n‐type polymers and the imide functionalization of appropriate (hetero)arenes is a powerful strategy for developing polymers with deep‐lying LUMOs for n‐type organic electronics. [ABSTRACT FROM AUTHOR]

A novel fluorenone-naphthyl pendant sensor (FTU) possessing thiourea functionality has been synthesized via a simple condensation method and utilized for the recognition of F - and Hg 2+ ions in the solution of CH 3 CN. The addition of F - and Hg 2+ ions to the FTU solution led to the appearance of red-shifted absorption bands at 340 and 315 nm, respectively. On the other hand, in the fluorescence spectrum, the two-fold decrease in fluorescence intensity of probe FTU was observed with F - ions; while complete quenching of the fluorescence intensity was noticed with Hg 2+ ions at 423 nm. The limit of detection values of F - and Hg 2+ ions were found to be 1.02 & 29.1 nM, respectively, measured by UV-vis studies and 0.0185 & 0.81 nM, respectively, measured by fluorescence studies, which are less than recommended by WHO. DFT computational assessments and 1 H NMR titration experiments pointed to F - induced deprotonation of thiourea NH signals. However, the chelation-enhanced quenching effect (CHEQ) was held responsible for fluorescence quenching with Hg 2+ addition. Moreover, the in-situ formed FTU + F - complex was utilized for secondary sensing of drug sobisis. Furthermore, the real-world applicability of sensor FTU has been successfully scrutinized for the recognition of F - ions in the toothpaste samples. In addition, molecular docking studies revealed that FTU exhibited excellent antibacterial potency towards different gram-positive as well as negative strains., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Fluorenone, a compound with a fused aromatic ring structure, is widely used in scientific research and technological advancements due to its extensive aromaticity, customizable electron-accepting traits, tuneable luminescence, efficient energy, charge transfer abilities, and unique characteristics. It plays a crucial role in material, medical, and chemical domains due to its broad applicability. Fluorenone based compounds exhibit diverse capabilities such as chemo sensing, biological activities, and photovoltaic potentials, showcasing their multifaceted nature in modern research and applications. 9-fluorenone is highly prized in supramolecular chemistry for its outstanding optical, photophysical, and biological attributes, making it a valuable compound with captivating photochemical and physicochemical properties, including the presence of conjugated poly-(en)yens. This comprehensive compilation of fluorenone-based sensors from 2010 to 2024 showcases their real-world applications in sensing, biological studies, and solar cell technology. We anticipate that delving into the insights provided by these literature reports will aid researchers in the fields of chemosensing, biosensing, and solar energy, enabling the development of superior fluorenone derivatives with enhanced practical applications in the future. • omprises development of fluorenone based compounds in past 15 years ranging from 2010 to 2024. • Describes the practical applications of fluorenone in sensing, biological studies, and solar cell technology. • Elucidates the role of position, substituents and nature of conjugation in the various applications of fluorenone. [ABSTRACT FROM AUTHOR]

An efficient synthesis of water-stable and fluorescent ZnS quantum dots has been executed beginning with its organic predecessor possessing fluorenone for sensing bovine serum albumin (BSA) among other proteins. Moreover, the organic predecessor of quantum dots has also been utilized for sensing of F- ions with binding constant of 1.8 × 104 M−1. Various spectroscopic techniques such as high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (PXRD), UV-visible (UV-vis), Fourier transform infrared (FTIR), thermogravimetric (TGA), Energy dispersive X-ray analysis (EDX), circular dichroism (CD) and Fluorescence (FL) spectroscopy have been utilized for the characterization of the developed quantum dots. The emission properties of quantum dots made them useful for the sensing of BSA and Cu2+ accompanied with secondary sensing of urea. The LODs value for BSA and Cu2+ were calculated as 213 and 211 nM, respectively. Demonstrating remarkable efficacy, these quantum dots have been successfully employed for the discernment of BSA in human blood and urine samples, achieving an outstanding recovery rate of up to 99.8%. • Synthesis of fluorescent, water-stable ZnS quantum dots for sensing of BSA and Cu2+ along with secondary sensing of urea. • Characterization of the developed quantum dots by HRTEM, PXRD, UV-vis, FTIR, TGA, EDX, CD and Fluorescence spectroscopy. • Organic predecessor of quantum dots for sensing of F- ions. • Successful detection of BSA in human blood and urine samples with good recovery. [ABSTRACT FROM AUTHOR]

2,7-Substituted fluorenone has a planar and slightly bent aromatic structure and is used as a building block for organic liquid crystals (LCs). Herein, we report for the first time the synthesis, phase-transition behaviour, and mesophase structure of fluorenone-incorporated LC trimers that exhibit an emerging helical twist-bend nematic (NTB) phase. The LC trimers possess a central 2,7-ether-substituted fluorenone and bilateral cyanobiphenyl groups linked via odd alkylene CnH2n spacers (n = 7 or 9) with either ether or thioether outer linkages; these are abbreviated CBOnOFlnOnOCB and CBSnOFlnOnSCB, respectively. The CBOnOFlnOnOCB trimers having only ether linkages display only the conventional nematic (N) phase, whereas the outer thioether-linked CBSnOFlnOnSCB trimers form an NTB phase below the temperature range of the N phase. Furthermore, the phase-transition behaviour of these fluorenone-based LC trimers is compared with that of the corresponding all-biphenyl-based motif trimer analogues, CBOnOBOnOCB and CBSnOBOnSCB. [ABSTRACT FROM AUTHOR]

Interest in polycyclic aromatic hydrocarbons (PAHs) including a functional group in its chemical structure, particularly oxygenated PAHs (OPAHs), has been growing due to the toxicity and wide presence of the compound. Understanding the formation mechanism of OPAHs is very important for reducing their emission during combustion. However, studies on the quantitative evaluation of OPAHs have been very limited. In this study, the formation of OPAHs was quantitatively evaluated in addition to that of PAHs using a flow reactor system in which a mixture of ethylene, O2, and N2 reacted at atmospheric pressure. 5 types of OPAHs were targeted in this study: phenol, benzofuran, dibenzofuran, 9-fluorenone, and benzanthrone. 3 types of monocyclic aromatic hydrocarbons (MAHs) and 17 types of PAHs were also analyzed by gas chromatography mass spectrometry. Measurements were performed at different reaction gas temperatures (1050 to 1350 K), residence times (0.40 to 1.5 second), and equivalence ratios (3.0 to 12.0). Some measured data, mainly MAHs and PAHs, were compared with the concentrations predicted using existing kinetic models. Finally, we evaluated the reaction pathways that contributed to the formation of the OPAHs such as benzofuran, dibenzofuran, 9-fluorenone, and benzanthrone quantified in this study. [ABSTRACT FROM AUTHOR]

Extended fluorenones represent a particular class of polycyclic compounds. The extension of the aromatic system through the fusion of additional benzene rings onto the central tricyclic fluorenone gives rise to an impressive topological diversity and allows to modulate the properties of the original molecule. The multiple ways this aromatic extension can be joined onto the tricyclic core generates multiple spatial arrangements from linear, angular, mixed linear‐angular, to helical. This extensive range of shapes and their subsequent applications has piqued the curiosity of the scientific community, who now creatively compete to develop selective and direct routes to these valuable molecular architectures. Potential applications of these diverse domains have also driven the development of strategies for the installation of various substituents at selected sites of the carbon backbone. This Review intends to provide the reader with an up‐to‐date overview of the methods for constructing extended fluorenones and their properties. [ABSTRACT FROM AUTHOR]

Fluorene and fluorenone are privileged structures with extensive utility in both materials science and drug discovery. Here, we describe syntheses of those moieties through isocyanide-based multicomponent reactions (IMCRs) and the incorporation of the products in diverse and complex derivatives that can be further utilized. We performed six different IMCRs, based on the dual functionality of 9-isocyano-9 H -fluorene, and we describe 23 unprecedented adducts. [ABSTRACT FROM AUTHOR]

Preparation of organic crystals mainly depends on solution‐deposition, sublimation, and melt‐deposition techniques. Solid‐state growth methods are generally not suitable for organic crystal growth due to the unprocurable mass transfer. Herein, we report two pyridine‐substituted fluorenone compounds with extraordinary crystal‐growth capacity, and these compounds can directly and quickly form single crystals from their amorphous solid powder by heating under antisolvent‐assistance conditions. The novel experimental phenomenon and crystal growth mechanism were investigated in depth. The results indicate that multiple intermolecular hydrogen‐bonding sites and planar aromatic structure (prone to π‐π interactions) of these molecules dominate the mass transfer during crystal growth by providing enough energy. This discovery enhances our knowledge of solid‐state methods for single‐crystal growth. [ABSTRACT FROM AUTHOR]

Fluorenone molecular materials provide an excellent platform to engineer new materials that are very promising for photonic and optoelectronic applications, such as very efficient optical second harmonic (SHG) and terahertz (THz) generation, light emitting diodes, biomarkers, solar cells, and sensors. More recently, there have been a lot of research efforts dedicated towards the nonlinear optical (NLO) properties of these fluorenone materials because of their unique combination of chemical, structural, and optical properties. This review addresses the state of the art of this very interesting and potent class of molecular materials. In particular, the NLO susceptibilities, their potential for optical SHG and THz generation and their two‐photon luminescence properties and how to optimize these by rational design are reviewed. Flexibility and easiness of modification of their molecular properties combined with their structural polymorphism enable a variety of applications. Perspectives and future research directions for these fluorenone materials are also presented. [ABSTRACT FROM AUTHOR]

A new derivative of our recently reported nonaromatic fluorenophyrin 5 named fluorenonephyrin 6 was synthesized over a sequence of six steps starting with commercially available fluorene as precursor. Our attempts to direct oxidation of 5 to 6 were not successful. Hence, we synthesized 2,7‐bis(phenyl(1H‐pyrrol‐2‐yl)methyl)‐9‐fluorenone (fluorenone tripyrrane) in five simple steps from fluorene, and condensed it with pentafluorobenzaldehyde under mild acidic conditions in CH2Cl2 followed by oxidation with DDQ and chromatographic purification to afford fluorenonephyrin (9%). 6 was characterized and studied by HR‐MS, 1D and 2D NMR spectroscopy, absorption, electrochemical and DFT/TD‐DFT techniques. The DFT studies revealed that 6 was more distorted than 5 and that introduction of C=O in the macrocyclic core remarkably distorts the pyrrole rings of the dipyrrin unit from the mean plane of macrocyclic framework. The macrocycle showed a band at around 390 nm and a broad band at around 650 nm. The redox properties indicated that the macrocycle was highly electron‐deficient in nature. TD‐DFT studies were in accordance with the experimental observations. [ABSTRACT FROM AUTHOR]

The luminescence property of 2,7-diphenyl-fluorenone (DPFO) was previously reported to be very unusual with a large aggregation-induced effect associated with a fluorescence redshift of 150 nm. The phenomenon is reexamined in this work. It is found that the abnormal observations are caused by the presence of a trace amount of impurity 2,7-diphenyl-fluorene (DPF) in the as-synthesized DPFO. The pure DPFO molecule does have an intense fluorescence (FL) in solid (528 nm), about 4–5 times larger than in its dilute dichloromethane solutions (542 nm), but with a blueshifted rather than redshifted FL wavelength in solid. The enormous FL enhancement and redshifted FL wavelength of the as-synthesized DPFO solid are due to the presence of impurity DPF. The FL of DPF is much stronger than that of DPFO in dilute solutions and it also has shorter FL wave-lengths. In a dilute solution of DPFO with a trace amount of DPF (~1%), the dominant FL peaks are from DPF. Because the electronic absorption peaks of DPF overlaps with DPFO, the electronic energy of DPF can transfer to DPFO. The energy transfer is faster with the increase of concentration because DPF and surrounding DPFO molecules become closer, which quenches the FL of DPF (356 and 372 nm) and enhances the FL of DPFO (542 nm in solution and 528 nm in solid). Therefore, at high concentrations or in solids, only peak at about 542 or 528 nm shows up, and peaks at 356 and 372 nm disappear. [ABSTRACT FROM AUTHOR]

Recently, in catalysis, chitosan has been exploited as a macrochelating ligand for metal active species due to the presence of various functional groups in its structure. Moreover, copper‐based catalysts are classified as one of the most environmentally friendly catalytic systems and their use for the oxidation of alkylarene has not been established much. Therefore, in this work, the hydrothermal synthesis of copper oxide‐chitosan composites as heterogeneous catalysts for the benzylic C−H oxidation of alkylarene was investigated. Characterization results reveal mixed phases of CuO and Cu2O, inferring the ability of chitosan to act as a reducing sugar under the hydrothermal condition. The pre‐existing interaction between copper species and chitosan as well as the co‐existence of the Cu2O and CuO structures give rise to the efficient performance of the catalysts. The synthesized composites exhibit high activity for the oxidation of fluorene to 9‐fluorenone at room temperature and small catalyst loading (1 mol % of Cu, >90 % conversion and 100 % selectivity). Superior TOF was observed, and a good scope of substrates can be converted to corresponding ketones in 48–97 % yields with these copper oxide‐chitosan catalysts. In addition, the catalysts can be used for up to nine cycles without significant decrease of the activity. [ABSTRACT FROM AUTHOR]

The synthesis of new meso-tetrafluorenylporphyrins peripherally functionalized with various 2-ethynyl fluorenyl and/or 2-ethynyl fluorenonyl arms is presented. The impact of these fluorenone units on their linear and nonlinear optical properties is also investigated. Thus, two-photon absorption and singlet oxygen photosensitising properties are evaluated. Improvement of these properties relative to their analogues featuring non-oxidized fluorenyl terminal groups, which make the molecules presented quite appealing for combined 2-photon-based photodynamic therapy (PDT) and imaging, is then briefly discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A phytochemical investigation on the Dendrobium nobile was performed. • One new lignan (1) and one new fluorenone (2) were isolated and identified. • Compounds 1 – 3 showed significant α-glucosidase inhibitory activity. • Molecular docking was performed to study the interactions of compounds 1 and 2 with α-glucosidase. Two new compounds, dendronobilate (1) and 4- O -demethyl-nobilone (2), together with one known fluorenone were isolated from the aerial parts of Dendrobium nobile Lindl. Their structures were characterized by detailed analysis of 1D and 2D NMR spectra, HRESIMS and ECD spectra. Compounds 1 – 3 showed significant α-glucosidase inhibitory activity with IC 50 values of 27.46 ± 3.14, 4.52 ± 0.33, and 10.78 ± 2.05 μM, respectively, which were superior to the acarbose (745.9 ± 3.3 μM). The binding interactions of 1 and 2 with α-glucosidase were investigated using molecular docking simulations. In addition, compound 2 exhibited potent inhibitory effect on NO production in LPS activated RAW264.7 cells with the IC 50 value of 35.40 ± 1.77 μM without cytotoxicity observed. [ABSTRACT FROM AUTHOR]

The electronic transitions of 9-fluorenone FL + and 2,3,6,7-dibenzotropone DBT + cations were detected in 6 K neon matrices following a mass-selective deposition. The absorptions at 649.2 and 472.2 nm are assigned to the 2 ²B1←X˜²A2 FL+ and 22A′←X˜2A′ DBT+ transitions. Absorption spectra of protonated 9-fluorenone H +-FL and 2,3,6,7-dibenzotropone H +-DBT have also been measured. Protonation of the oxygenated polycyclic aromatic hydrocarbons is carried out in a hot cathode source via in situ produced protonated ethanol. Vibrationally resolved absorptions commencing at 423.3 nm of H-FL + and two band systems of H-DBT + with origins at 502.4 and 371.5 nm are assigned to the 21A′←X˜1A′ electronic transition of 9-hydroxy-fluorenyl cation and 1 ¹A←X˜¹A, 2 ¹A←X˜¹A of 2,3,6,7-dibenzocycloheptenol cation. The assignments are based on vertical excitation energy calculations with time dependent density functional theory, symmetry adapted cluster configuration interaction, and MS-CASPT2 methods. [ABSTRACT FROM AUTHOR]

The rotational spectrum of fluoren-9-one, a small oxygenated polycyclic aromatic hydrocarbon, has been recorded and assigned in the 52-74.4 GHz region. The determined small negative value of the inertia defect (-0.3 u Ų) has been explained in terms of vibrational-rotational coupling constants calculated at the B3LYP/cc-pVTZ level of theory. Vibrational anharmonic analysis together with second-order vibrational perturbation theory approximation was applied both to fluorenone and its reduced form, fluorene, to predict the mid- and near-infrared spectra. The data presented here give precise indication on the fluorenone ground state structure, allow for an accurate spectral characterization in the millimeter wave and infrared regions, and hopefully will facilitate extensive radio astronomical searches with large radio telescopes. [ABSTRACT FROM AUTHOR]

The base-catalyzed reaction of diethyl 1,3-acetonedicarboxylate with 2-hydroxybenzylidene indenediones was studied. The reaction provides a facile and expeditious protocol for the synthesis of natural product inspired fluorenone-fused coumarins in good to very good yields. This process resembles a combination of domino Michael–intramolecular Knoevenagel–aromatization–lactonization reactions in a single step. Although this reaction operates with many bases, the best yields were obtained with DMAP as a catalyst. This protocol could open new potential avenues for the synthesis of fused coumarins by the reaction of substituted β-keto esters with different 2-(2-hydroxybenzylidenes) of 1,3-dicarbonyl compounds. [ABSTRACT FROM AUTHOR]

Four fluorenone-based materials were designed, prepared and characterized for organic light emitting diodes. These derivatives possess relatively high thermal stability with the 5% mass loss temperatures in the range of 271–395 °C. The fluorenone-based materials showed oxidation bands in the range of 0.77–1.11 V. Ionization potential values of the films were found to be in the range from 5.11 to 5.41 eV. The differently substituted compounds were utilized as an emitters in organic light emitting diodes. Nevertheless, the doped devices based on 90 wt% 1,3-bis(N-carbazolyl)benzene as a host material have produced orange and red electroluminescence with CIEx,y of (0.52102, 0.43609) and (0.60724, 0.38766) with a low turn on voltage of 5.08 V, maximum external quantum efficiency of 2.54%, maximum brightness efficiency of 7509.14 cd/m−2 and maximum current and power efficiency of 15.73 cd/A−1 and 8.13 lm/W−1 respectively, that these results indicate that the 1,3-bis(N-carbazolyl)benzene host was matched and it is in the well agreement with emitters and select these series of compounds are an attractive approach for the extension of efficient fluorescence organic light emitting diodes. [ABSTRACT FROM AUTHOR]

Abstract Palladium-catalysed sequential one-pot synthesis of fluorenones is described. The reaction comprises intermolecular Suzuki coupling and intramolecular acid-mediated cyclisation in a one-pot procedure. The protocol is also applied to the synthesis of fluorenes using a single column purification.

In this paper, a series of hexacatenars, where the central fluorenone is connected two α-cyanostilbene which is substituted with 3,4,5-trialkoxybenzyl, was synthesized by Pd-catalyzed Suzuki coupling and Knoevenagel reaction as key steps. The LC characteristics, photophysical and electrochemical behaviors were evaluated by using POM, DSC, TGA, XRD, DFT calculations, UV-vis spectroscopy, photoluminescence measurements and CV. A rare mesophase sequence from Colhex/p6mm to Colrec/p2mm was observed and the mesophase width increased upon terminal chain elongation. The photophysical behaviors in different solutions and aggregated states indicated that these compounds exhibited solvatochromism, fluorescence quantum yields and aggregation-induced emission (AIE) behaviors. The electrochemical behaviors in thin film indicated these compounds show low band gap. DFT calculations of the investigated hexacatenars were accomplished to determine the structural, electronic and intermolecular interaction properties. [ABSTRACT FROM AUTHOR]