Potential Treatments for Epiglottic Collapse in Obstructive Sleep Apnea: How Modified Drug-Induced Sleep Endoscopy Help?

OBJECTIVE: In patients with obstructive sleep apnea (OSA), epiglottic collapse (EC) constitutes a major factor in the failure of continuous positive airway pressure therapy and uvulopalatopharyngoplasty. This study explored treatments that can improve EC in patients with OSA through drug-induced sleep endoscopy with target-controlled infusion (TCI-DISE). STUDY DESIGN: Retrospective cohort study. SETTING: Tertiary center. METHODS: This study screened 352 OSA patients who underwent TCI-DISE between 2016 and 2022. Fifty-four patients with EC were included in the final analysis. EC severity was assessed multiple times through TCI-DISE with different interventions. RESULTS: The application of these interventions in patients with anteroposterior epiglottic collapse (apEC) led to a significant decrease in apEC severity from total to partial or no obstruction in 60.0% of patients by head rotation, in 53.6% by mouth closure, in 47.4% who received oral appliances (OA), and in 28.0% who received intermittent negative airway pressure (iNAP). With simultaneous head rotation, apEC severity decreased more significantly from total to partial or no obstruction in 77.8% of patients by mouth closure, in 70.3% who received OA, and in 68.0% who received iNAP. Lateral epiglottic collapse (latEC) severity decreased in 53.8% of patients after OA use and in 61.5% of patients with OA use and head rotation. CONCLUSION: This study identified head rotation with mouth closure as the most effective treatment for apEC through TCI-DISE. Patients with latEC had higher weight, apnea-hypopnea index, and body mass index compared with patients with apEC. OA use with head rotation appeared more effective in latEC through TCI-DISE.

A Benzil- and BODIPY-Based Turn-On Fluorescent Probe for Detection of Hydrogen Peroxide.

Faced with rising threats of terrorism, environmental and health risks, achieving sensitive and selective detection of peroxide-based explosives (PEs) has become a global focus. In this study, a turn-on fluorescent probe (BOD) based on benzil (H2O2-recognition element) and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivative (fluorophore) was developed to sensitively and specifically detect hydrogen peroxide (H2O2). The synthesized BOD had a very weak fluorescence due to intramolecular donor-excited photo-induced electron transfer (d-PET) effect; however, it could emit a strong fluorescence since H2O2 selectively oxidized the benzil moiety and released free BODIPY fluorophore (BOD-COOH). As a result, the proposed BOD detected H2O2 in linear detection ranged from 25 to 125 µM with a detection limit of 4.41 µM. Meanwhile, the proposed BOD showed good selectivity toward H2O2, which is not affected by other common reactive oxygen species (ROS) and ions from explosive residues. In addition, a blue shift from 508 to 498 nm was observed in the absorption spectra upon addition of H2O2. More importantly, the BOD was successfully applied for rapid detection of H2O2 vapor with good sensitivity (down to 7 ppb), which holds great potential for practical use in public safety, forensic analysis and environmental monitoring.

New Benzil and Isoflavone Derivatives with Cytotoxic and NO Production Inhibitory Activities from Placolobium vietnamense.

The phytochemical investigation of Placolobium vietnamense stems led to the isolation of a new isoflavone derivative (1) and three new benzil derivatives (2-4), together with four known pyranoisoflavones (5-8). The structures of all isolated compounds were determined on the basis of extensive spectroscopic analyses, including NMR and HRMS spectral data, as well as comparison of their spectroscopic data with those reported in the literature. The cytotoxicity of all isolated compounds was assessed against the human liver hepatocellular carcinoma (Hep G2) cell line, and compound 1 displayed the most significant cytotoxicity with an IC50 value of 8.0 µM. Furthermore, all isolated compounds were also tested for their inhibitory activity against NO production in RAW 264.7 macrophages. Of these, compound 1 exhibited the strongest inhibitory efficacy against the LPS-induced NO production with the IC50 value of 13.7 µM.

Catalyst-free [2 + 2] photocycloadditions between benzils and olefins under visible light.

The catalyst-free [2 + 2] photocycloaddition between benzils and simple olefins is reported. The adoption of visible light proved essential for the transformation, as shorter wavelengths led to uncontrolled decomposition. When cyclic olefins were used, the reaction occurred smoothly to afford the expected oxetanes regio- and stereoselectively after 24 h of irradiation. In contrast, in the case of acyclic olefins, longer reaction times were typically required and small amounts (ca. 20%) of [4 + 2] photocycloadducts and by-products deriving from competitive hydrogen atom abstraction were observed. The selectivity of the transformation could be consistently improved by decreasing the reaction temperature, thus restoring the desired [2 + 2] reactivity. An overall mechanistic picture is also offered based on the chemical and photophysical quenching experiments and the stereochemical output is rationalized based on Griesbeck models.

Synthesis, biological evaluation (antioxidant, antimicrobial, enzyme inhibition, and cytotoxic) and molecular docking study of hydroxy methoxy benzoin/benzil analogous.

In this work, due to the biological activity evaluation, a series of hydroxy methoxy benzoins (1-8), benzils (10-16) and methoxy benzoin/benzil-O-ß-d-glucosides (17-28) were synthesized. Antioxidant (FRAP, CUPRAC, DPPH), antimicrobial (16 microorganisms, and two yeast), enzyme inhibition (α-amylase, α-glucosidase, AChE, BChE, and tyrosinase) of all synthesized benzoin/benzil analogs were investigated. Benzoins (1-8) showed the most effective antioxidant properties compared to all three methods. Compound 28 against α-amylase, compound 9 against α-glucosidase, compound 11 against AChE, compound 2 against BChE, and compound 13 against tyrosinase showed the best activities with the better or similar IC50 values as used standards. Hydroxy methoxy benzoin compounds (1-8) among all four groups were seen as the most effective against the tested microorganism. Molecular docking analysis showed that all tested compounds 1-28 (0.01-2.22 µM) had the best binding affinity against AChE enzyme. Cytotoxic effects of the many of compounds (1-16, 21, and 24) also investigated and it was found that they caused different effects in different cells. The LDH tests of compounds 1a + b, 4, 7, 8, 9, 11, 12, 21, and 24, seemed to be effective compared to the positive control cisplatin. The cytotoxicity of compounds 6 (9.24%) for MCF7 cancer cells, 8 (5.16%) and 4 (8.26%) for HT29 cancer cells, 24 (9.84%) for Hep3B cells and 8 (8.52%), 7 (5.70%), 4 (6.94) and 9 (7.22%) for C6 cells were at normal values. And also cytotoxic activity of four compounds (5, 9, 21, and 24) among the all synthetic groups, were evaluated to the HeLa and RPE. Compound 5 showed anticancer activity on HeLa and RPE cancer cells as much as or better than cisplatin which was used as standard.

Microbial Synthesis of (S)- and (R)-Benzoin in Enantioselective Desymmetrization and Deracemization Catalyzed by Aureobasidium pullulans Included in the Blossom Protect™ Agent.

In this study, we examined the Aureobasidium pullulans strains DSM 14940 and DSM 14941 included in the Blossom Protect™ agent to be used in the bioreduction reaction of a symmetrical dicarbonyl compound. Both chiral 2-hydroxy-1,2-diphenylethanone antipodes were obtained with a high enantiomeric purity. Mild conditions (phosphate buffer [pH 7.0, 7.2], 30 °C) were successfully employed in the synthesis of (S)-benzoin using two different methodologies: benzyl desymmetrization and rac-benzoin deracemization. Bioreduction carried out with higher reagent concentrations, lower pH values and prolonged reaction time, and in the presence of additives, enabled enrichment of the reaction mixture with (R)-benzoin. The described procedure is a potentially useful tool in the synthesis of chiral building blocks with a defined configuration in a simple and economical process with a lower environmental impact, enabling one-pot biotransformation.

Chiral Benzoins via Asymmetric Transfer Hemihydrogenation of Benzils: The Detail that Matters.

The synthesis of enantiomerically pure benzoins by hydrogenation of readily available benzils has been long thwarted by their base-sensitivity. We show here that an iron(II) hydride complex catalyzes the asymmetric transfer hydrogenation of benzils from 2-propanol. When strictly base-free conditions are granted, excellent enantioselectivity is achieved even with o-substituted substrates, which are particularly challenging to prepare with other methods. Hence, under optimized reaction conditions, chiral benzoins were prepared in good yields (up to 83%) and excellent enantioselectivity (up to 98% ee) in short reaction times (30-75 min). Also, this work confirms that both enantiomers of the benzoin products can be accessed when a metal catalyst is used, which is a clear advantage over enzymatic methods.

Synthesis, crystal structures, antiproliferative activities and reverse docking studies of eight novel Schiff bases derived from benzil.

Eight novel Schiff bases derived from benzil dihydrazone (BDH) or benzil monohydrazone (BMH) and four fused-ring carbonyl compounds (3-formylindole, FI; 3-acetylindole, AI; 3-formyl-1-methylindole, MFI; 1-formylnaphthalene, FN) were synthesized and characterized by elemental analysis, ESI-QTOF-MS, 1H and 13C NMR spectroscopy, as well as single-crystal X-ray diffraction. They are (1Z,2Z)-1,2-bis{(E)-[(1H-indol-3-yl)methylidene]hydrazinylidene}-1,2-diphenylethane (BDHFI), C32H24N6, (1Z,2Z)-1,2-bis{(E)-[1-(1H-indol-3-yl)ethylidene]hydrazinylidene}-1,2-diphenylethane (BDHAI), C34H28N6, (1Z,2Z)-1,2-bis{(E)-[(1-methyl-1H-indol-3-yl)methylidene]hydrazinylidene}-1,2-diphenylethane (BMHMFI) acetonitrile hemisolvate, C34H28N6·0.5CH3CN, (1Z,2Z)-1,2-bis{(E)-[(naphthalen-1-yl)methylidene]hydrazinylidene}-1,2-diphenylethane (BDHFN), C36H26N4, (Z)-2-{(E)-[(1H-indol-3-yl)methylidene]hydrazinylidene}-1,2-diphenylethanone (BMHFI), C23H17N3O, (Z)-2-{(E)-[1-(1H-indol-3-yl)ethylidene]hydrazinylidene}-1,2-diphenylethanone (BMHAI), C24H19N3O, (Z)-2-{(E)-[(1-methyl-1H-indol-3-yl)methylidene]hydrazinylidene}-1,2-diphenylethanone (BMHMFI), C24H19N3O, and (Z)-2-{(E)-[(naphthalen-1-yl)methylidene]hydrazinylidene}-1,2-diphenylethanone (BMHFN) C25H18N2O. Moreover, the in vitro cytotoxicity of the eight title compounds was evaluated against two tumour cell lines (A549 human lung cancer and 4T1 mouse breast cancer) and two normal cell lines (MRC-5 normal lung cells and NIH 3T3 fibroblasts) by MTT assay. The results indicate that four (BDHMFI, BDHFN, BMHMFI and BMHFN) are inactive and the other four (BDHFI, BDHAI, BMHFI and BMHAI) show severe toxicities against human A549 and mouse 4T1 cells, similar to the standard cisplatin. All the compounds exhibited weaker cytotoxicity against normal cells than cancer cells. The Swiss Target Prediction web server was applied for the prediction of protein targets. After analyzing the differences in frequency hits between these active and inactive Schiff bases, 18 probable targets were selected for reverse docking with the Surflex-dock function in SYBYL-X 2.0 software. Three target proteins, i.e. human ether-á-go-go-related (hERG) potassium channel, the inhibitor of apoptosis protein 3 and serine/threonine-protein kinase PIM1, were chosen as the targets. Finally, the ligand-based structure-activity relationships were analyzed based on the putative protein target (hERG) docking results, which will be used to design and synthesize novel hERG ion channel inhibitors.

Structure reactivity relationship in the accelerated formation of 2,3-diarylquinoxalines in the microdroplets of a nebuliser.

Competition experiments in which 1,2-phenylenediamine, C6H4(NH2)2, condenses with equimolar quantities of benzil, (C6H5CO)2, and a 3,3'- or 4,4'-disubstituted benzil (XC6H4CO)2 (X = F, Cl, Br, CH3 or CH3O) to form a mixture of 2,3-diphenylquinoxaline and the corresponding 2,3-diarylquinoxaline (Ar = XC6H4) in the microdroplets produced in a nebuliser allow a Hammett relationship with a ρ value of 1.85 to be developed for this accelerated condensation in the nebuliser. This structure reactivity relationship reveals that an appreciable amount of negative charge builds up on the carbon of the carbonyl group of the benzil during the rate-limiting step of the reaction, thus confirming that this process involves nucleophilic addition of the 1,2-phenylenediamine to the benzil. In general, the presence of an electron donating substituent, particularly in the 4 and 4' positions, in the benzil retards the reaction, whereas an electron attracting substituent, especially in the 3 and 3' position, accelerates it.

H2O2-responsive polymeric micelles with a benzil moiety for efficient DOX delivery and AIE imaging.

Nano drug delivery is a promising domain in biomedical theranostics and has aroused more and more attention in recent years. We report here an amphiphilic polymer TPG1, bearing a H2O2-sensitive benzil and an AIE fluorophore tetraphenylethene (TPE) unit, which is able to self-assemble into spherical nanosized micelles in aqueous solution. Doxorubicin (DOX) can be encapsulated into TPG1 micelles efficiently with the loading capability of up to 59% by weight. The benzil moiety could be cleaved via the Baeyer-Villiger type reaction in the presence of H2O2, leading to the decomposition of TPG1 micelles and release of DOX. In vitro studies indicated that DOX-loaded TPG1 micelles can be internalized by cancer cells, followed by unloading encapsulated DOX under the stimulation of H2O2. The drug release process can be monitored by the AIE fluorescence from the degradation products containing a TPE moiety. MTT assays against HeLa and HepG2 cancer cells demonstrated that DOX-loaded micelles showed good anticancer efficacy. The polymer TPG1 and the corresponding decomposed products showed great biocompatibility. Our data suggest that TPG1 has the potential to be employed for the controlled drug delivery system.

New mixed amino acids complexes of iron(III) and zinc(II) with isonitrosoacetophenone: Synthesis, spectral characterization, DFT study and anticancer activity.

New mixed Fe(III) and Zn(II) complexes with isonitrosoacetophenone (HINAP) and l-amino acids (such as l-histidine, l-phenylalanine and l-proline) have been synthesized and characterized by elemental analyses, UV-Vis, IR and ESR spectroscopy and thermal analyses. The values of molar conductance of the complexes in DMSO solution at 10-3 M concentration indicate their non-electrolyte nature. IR spectroscopy has revealed the coordination of deprotonated ligands to metal through nitrogen and oxygen atoms in an N2O2 arrangement. Density functional theory (DFT) calculations were performed using the hybrid functional of Truhlar and Zhao (M06) with basis set of double zeta quality LANL2DZ to evaluate the cis and trans coordination modes and to ascertain dipole moment, HOMO-LUMO energy gap, chemical hardness, softness and electrophilicity. The magnetic moments and ESR measurements suggest that there is an admixture of S = 5/2 and S = 1/2 spins in Fe(III) complexes. UV-Visible spectra indicate a distorted octahedral geometry around the metal ions. Thermal analyses show the presence of hydrated and coordinated water. The antimicrobial activity was investigated against (G+ and G-) bacteria (Staphylococcus aureus, bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa) and fungi (Candida albicans). The iron and zinc complexes were found to be more active against Gram-positive than Gram negative bacteria. They also show considerable growth inhibition against the fungi tested. In vitro antitumor activity assayed against cancer cell lines of the HEP2 type (cancer cells of the larynx) exhibited significant toxicity of the ligands and their mixed complexes.

Novel, Non-aqueous Bioconversion Systems Using Fungal Spores.

Two novel types of non-aqueous bioconversion systems using fungal spores, either adsorbed on the surface of a filter pad or entrapped in calcium alginate beads, were constructed and applied for a model reaction: reduction of benzil to benzoin by Aspergillus sojae NBRC 32074. The spores adsorbed on a filter pad catalyzed the reduction in some toxic organic solvents, such as methylcyclohexane (log P: 3.61) and din-butyl ether (3.21). For the relationship between the reduction activity and the log P value of the organic solvent, a highly positive correlation (R2: 0.815) was observed. Surprisingly, the reduction proceeded in the more hydrophilic and toxic tert-butyl acetate (log P: 1.76). Glycerol was selected as the best hydride source. The higher the glycerol content, the more the benzoin was produced. While the production of benzil by spores was lower than that by mycelia in harmless di-n-hexyl ether (log P: 5.12), mycelia could not catalyze the reduction in the toxic tert-butyl acetate. In contrast, the spores entrapped in the calcium alginate beads could catalyze the reduction. Although the reduction by alginate-entrapped spores could be stably repeated 5 times in di-n-hexyl ether without a decline in the reduction activity, it was observed that the reduction activity of the spores gradually decreased after repeated reduction in tert-butyl acetate.

Arginine-selective bioconjugation with 4-azidophenyl glyoxal: application to the single and dual functionalisation of native antibodies.

Here, we introduce 4-azidophenyl glyoxal (APG) as an efficient plug-and-play reagent for the selective functionalisation of arginine residues in native antibodies. The selective reaction between APG and arginines' guanidine groups allowed a facile introduction of azide groups on the monoclonal antibody trastuzumab (plug stage). These pre-functionalised antibody-azide conjugates were then derivatised during the "play stage" via a biorthogonal cycloaddition reaction with different strained alkynes. This afforded antibody-fluorophore and antibody-oligonucleotide conjugates, all showing preserved antigen selectivity and high stability in human plasma. Due to a lower content of arginines compared to lysines in native antibodies, this approach is thus attractive for the preparation of more homogeneous conjugates. This method proved to be orthogonal to classical lysine-based conjugation and allowed straightforward generation of dual-payload antibody.

The identification of new substrates of human DHRS7 by molecular modeling and in vitro testing.

Human DHRS7 (SDR34C1) is one of insufficiently described enzymes of the short-chain dehydrogenase/reductase superfamily. The members of this superfamily often play an important pato/physiological role in the human body, participating in the metabolism of diverse substrates (e.g. retinoids, steroids, xenobiotics). A systematic approach to the identification of novel, physiological substrates of DHRS7 based on a combination of homology modeling, structure-based virtual screening and experimental evaluation has been used. Three novel substrates of DHRS7 (dihydrotestosterone, benzil and 4,4'-dimetylbenzil) have been described.

Synthesis of benzil-o-carboxylate derivatives and isocoumarins through neighboring ester-participating bromocyclizations of o-alkynylbenzoates.

Bromide mediated neighboring ester-participating bromocyclizations of o-alkynylbenzoates are described here for the synthesis of benzil-o-carboxylates. 4-bromoisocoumarins are also synthesized when phenyl o-alkynylbenzoate is used as the substrate. Mechanistic studies suggest that the whole process is composed of an electrophilic bromocyclization and a dibromohydration-based ring-opening, and the neighboring ester group participates in the bromocyclization. Interestingly, the two oxygen atoms of the keto carbonyls in benzil-o-carboxylates are both derived from water. The electrophilic bromo source is in situ generated from the oxidation of bromide.

One-pot synthesis of a new 2-substituted 1,2,3-triazole 1-oxide derivative from dipyridyl ketone and isonitrosoacetophenone hydrazone: Nickel(II) complex, DNA binding and cleavage properties.

An efficient and simple one-pot synthesis of a new 1,2,3-triazole-1-oxide via reaction between isonitrosoacetophenone hydrazone and dipyridyl ketone in the EtOH/AcOH at room temperature has been developed smoothly in high yield. The reaction proceeds via metal salt free, in-situ formation of asymmetric azine followed by cyclization to provide 1,2,3-triazole 1-oxide compound. It has been structurally characterized. The 1:1 ratio reaction of the 1,2,3-triazole 1-oxide ligand with nickel(II) chloride gives the mononuclear complex [Ni(L)(DMF)Cl2], hexa-coordinated within an octahedral geometry. Characterization of the 1,2,3-triazole compound and its Ni(II) complex with FTIR, 1H and 13C NMR, UV-vis and elemental analysis also confirms the proposed structures of the compounds. The interactions of the compounds with Calf thymus DNA (CT-DNA) have been investigated by UV-visible spectra and viscosity measurements. The results suggested that both ligand and Ni(II) complex bind to DNA in electrostatic interaction and/or groove binding, also with a slight partial intercalation in the case of ligand. DNA cleavage experiments have been also investigated by agarose gel electrophoresis in the presence and absence of an oxidative agent (H2O2). Both 1,2,3-triazole 1-oxide ligand and its nickel(II) complex show nuclease activity in the presence of hydrogen peroxide. DNA binding and cleavage affinities of the 1,2,3-triazole 1-oxide ligand is stronger than that of the Ni(II) complex.

Design, synthesis, characterization and antimicrobial/antioxidant activities of 1, 4-dicarbonyl-phenyl-dihydrazide based macrocyclic ligand and its Cu(II), Co(II) and Ni(II) complexes.

Mononuclear transition metal complexes of Cu(II), Co(II) and Ni(II) with a newly synthesised macrocyclic ligand derived from 1, 4-dicarbonyl-phenyl-dihydrazide and 1,2-diphenylethane-1,2-dione (2:2) have been synthesised. The synthesised compounds were characterised by various physical and spectroscopic techniques including elemental analysis, FTIR, Uv-Vis., 1H NMR, mass spectra, magnetic moment and XRD. The investigation of these macrocyclic complexes established that the stability of metal-ligand coordination through N atoms as tetradentate chelates. The metal/ligands ratio of 1:1 was proposed to afford octahedral geometry for the complexes. The antimicrobial activity of the compounds against some bacterial and fungal species were done by well diffusion method and the results shows that the metal complexes have a promising biological activity comparable with the parent ligand against all bacterial and fungal species. The antioxidant activity of the compounds was also studied through scavenging effect on DPPH radicals with the copper complex showing enhanced activity than other compounds. Additionally, the docking studies predicted the high antimicrobial activity due to the interaction of ligand with the protein.

Biotransformation Capacity of Carboxylesterase in Skin and Keratinocytes for the Penta-Ethyl Ester Prodrug of DTPA.

The penta-ethyl ester prodrug of the chelating agent diethylene triamine pentaacetic acid (DTPA), referred to as C2E5, effectively accelerated clearance of americium after transdermal delivery. Carboxylesterases (CESs) play important roles in facilitating C2E5 hydrolysis. However, whether CESs in human skin hydrolyze C2E5 remains unknown. We evaluated the gene and protein expression of CESs in distinctive human epidermal cell lines: HEKa, HEKn, HaCaT, and A431. The substrates p-nitrophenyl acetate (pNPA) and 4-nitrophenyl valerate (4-NPV) were used to access esterase and CES activity. C2E5 hydrolysis was measured by radiometric high-performance liquid chromatography after incubation of [(14)C]C2E5 with supernatant fractions after centrifugation at 9000g (S9) prepared from skin cell lines. CES-specific inhibitors were used to access metabolism in human skin S9 fractions with analysis by liquid chromatography-tandem mass spectrometry. We identified the human carboxylesterase 1 and 2 (CES1 and CES2) bands in a Western blot. The gene expression of these enzymes was supported by a real-time polymerase chain reaction (qPCR). pNPA and 4-NPV assays demonstrated esterase and CES activity in all the cell lines that were comparable to human skin S9 fractions. The prodrug C2E5 was hydrolyzed by skin S9 fractions, resulting in a primary metabolite, C2E4. In human skin S9 fractions, inhibition of C2E5 hydrolysis was greatest with a pan-CES inhibitor (benzil). CES1 inhibition (troglitazone) was greater than CES2 (loperamide), suggesting a primary metabolic role for CES1. These results indicate that human keratinocyte cell lines are useful for the evaluation of human cutaneous metabolism and absorption of ester-based prodrugs. However, keratinocytes from skin provide a small contribution to the overall metabolism of C2E5.

INaP selective inhibition reverts precocious inter- and motorneurons hyperexcitability in the Sod1-G93R zebrafish ALS model.

The pathogenic role of SOD1 mutations in amyotrophic lateral sclerosis (ALS) was investigated using a zebrafish disease model stably expressing the ALS-linked G93R mutation. In addition to the main pathological features of ALS shown by adult fish, we found remarkably precocious alterations in the development of motor nerve circuitry and embryo behavior, and suggest that these alterations are prompted by interneuron and motor neuron hyperexcitability triggered by anomalies in the persistent pacemaker sodium current INaP. The riluzole-induced modulation of INaP reduced spinal neuron excitability, reverted the behavioral phenotypes and improved the deficits in motor nerve circuitry development, thus shedding new light on the use of riluzole in the management of ALS. Our findings provide a valid phenotype-based tool for unbiased in vivo drug screening that can be used to develop new therapies.

Self-assembly of Metallamacrocycles Employing a New Benzil-based Organometallic Bisplatinum(II) Acceptor.

A benzil-based semi-rigid dinuclear-organometallic acceptor 4,4'-bis[trans-Pt(PEt(3))(2)(NO(3))(ethynyl)]benzil (bisPt-NO(3)) containing a Pt-ethynyl functionality was synthesized in good yield and characterized by multinuclear NMR ((1)H, (31)P, and (13)C), electrospray ionization mass spectrometry (ESI-MS), and single-crystal X-ray diffraction analysis of the iodide analogue bisPt-I. The stoichiometric (1:1) combination of the acceptor bisPt-NO(3) separately with four different ditopic donors (L(1)-L(4); L(1) = 9-ethyl-3,6-di(1H-imidazol-1-yl)-9H-carbazole, L(2) = 1,4-bis((1H-imidazol-1-yl)methyl)benzene, L(3) = 1,3-bis((1H-imidazol-1-yl)methyl)benzene and L(4) = 9,10-bis((1H-imidazol-1-yl) methyl)anthracene) yielded four [2 + 2] self-assembled metallacycles M(1)-M(4) in quantitative yields, respectively. All these newly synthesized assemblies were characterized by various spectroscopic techniques (NMR, IR, ESI-MS) and their sizes/shapes were predicted through geometry optimization employing the PM6 semi-empirical method. The benzil moiety was introduced in the backbone of the acceptor bisPt-NO(3) due to the interesting structural feature of long carbonyl C-C bond (∼1.54 Å), which enabled us to probe the role of conformational flexibility on size and shapes of the resulting coordination ensembles.