Contact angle hysteresis in multiphase systems

Contact angle (CA) hysteresis is the difference between the maximum (advancing) and minimum (receding) water CA. Hysteresis is caused by adhesion hysteresis in the solid–water contact area (2D effect) and by pinning of the solid–water–air triple line due to the surface roughness (1D effect). In this work, we show that CA hysteresis is present also in more complex systems, such as an organic liquid (oil) in contact with a solid immersed in water. In order to decouple the 1D and 2D effects, we study CA hysteresis in solid–water–air (droplet), solid–air–water (bubble), solid–water–oil, and solid–water–air–oil systems involving rough and microstructured surfaces. The comparative analysis of these systems allows decoupling the 1D and 2D effects as well as hydrogen bonding and entropic forces (water–air tension) and dispersion forces (oil–air tension).     

8-Aza-7-deaza-2′-deoxyguanosine: Phosphoramidite synthesis and properties of octanucleotides

Base-modified octanucleotides derived from d(G1–G2–A–A–T–T–C–C–) ( 11 ) but containing 8-aza-7-deaza-2′-deoxyguanosine ( 2 ) instead of 2′-deoxyguanosine ( 1 ) have been prepared by solid-phase synthesis employing P(III) chemistry. Isobutyrylation of 2 , followed by 4, 4′-dimethoxytritylation and subsequent phosphitylation yielded the methyl or the cyanoethyl phosphoramidites 6a or 6b , respectively. They were used as building blocks in automated DNA synthesis. The resulting octanucleotides 12–14 containing 2 showed increased T_m values compared to the parent oligomer 11 . The oligomers 11 – 14 were employed as sequence-specific probes in endo-deoxyribonuclease Eco RI oligonucleotide recognition. Whereas displacement of dG-2 (enzymic cleavage site of 11 ) abolished phosphodiester hydrolysis, replacement of dG-1 enhanced the cleavage rate compared to 11 .     

Synthetic and spectroscopic study of 5-amino-2-acyl-1,2,4-thiadiazolin-3-ones

5-Amino-2-acyl-1,2,4-thiadiazolin-3-ones 2–1 can be synthesized from 5-amino-2H-1,2,4-thiadiazolin-3-one ( 1–1 ) via a selective acylation with an acid anhydride in pyridine. The ¹H nmr spectral characteristics of 5-amino-2-acyl-1,2,4-thiadiazolin-3-ones 2–1 is in particular, compared with 5-amino-2H-1,2,4-thiadiazolin-3-one ( 1–1 ) and 5-amino-2-alkyl-1,2,4-thiadiazolin-3-ones 1–2, 1–3 . The 5-amino group of 2–1 appeared as two peaks in its ¹H nmr spectrum, which merged to a single peak at a higher temperature, while those of compound 1–1, 1–2 and 1–3 appear only as a single peak. The restricted rotation of the C(5)-N(5) (at amino) bond of 5-amino-2-acetyl-1,2,4-thiadiazolin-3-one (2a-1) is about 14.5 Kcal/mol.     

N-Heterocyclic carbenes as ligands in palladium-catalyzed Tsuji–Trost allylic substitution

A Pd(0)-catalyzed allylic substitution (i.e., Tsuji–Trost reaction) using N-heterocyclic carbene as a ligand was investigated. It has been proven that an imidazolium salt 2d having bulky aromatic rings attached to the nitrogens in its imidazol-2-ylidene skeleton is suitable as a ligand precursor and that a Pd₂dba₃–imidazolium salt 2d–Cs₂CO₃ system is highly efficient for producing a Pd–NHC catalyst in this reaction. Allylic substitution using a Pd–NHC complex differed from that using a Pd–phosphine complex as follows: (1) the reaction using a Pd–NHC complex required elevated temperature (50 °C or reflux in THF), (2) allylic carbonates were inert to a Pd–NHC complex, and (3) nitrogen nucleophiles such as sulfonamide and amine did not react with allylic acetate. It was also found that allylic substitution with a soft nucleophile using a Pd–NHC catalyst proceeds via overall retention of configuration to give the product in a stereospecific manner, the stereochemical reaction course obviously being the same as that of the reaction using a Pd–phosphine complex.     

[(1,3-Dioxolan-2-yliden)methyl]phosphonate und -phosphinate als (einfache) Synthone in der Heterocyclensynthese

[(1,3-Dioxolan-2-ylidene)methyl]phosphonates and -phosphinates as [simple] Synthons in Heterocyclic Synthesis The readily available [(1,3-dioxolane-2-ylidene)methyl]phosphonates and -phosphinates 2a–f (Scheme 1) can be transformed with amines to aliphatic ketene N,O-and N,N-acetales (see Scheme 2, 2a → 3–7 ). Alkanediamines yield with 2a–f the imidazolidines 8a–f and the hexahydropyrimidines 9a–d (Scheme 3). the oxazolidine derivatives 10a–e and the thiazolidine 11 are accessible under special reaction conditions starting from 2a, b (Scheme 4). Hydrazines react with the CN-group-containing ketene O,O-acetals 2a–c to the pyrazoles 12a–g , whereof 12a, d, e can be cyclized to pyrazolo[1,5-a]pyrimidines 13a–d (Scheme 5). Amidines as starting materials transform 2a–c in an analogous way to the pyrimidine derivatives 14a–c (Scheme 6).     

Improved photovoltaic performance of 2,7-pyrene based small molecules via the use of 3-carbazole as terminal unit

Small molecule of Py-2DTBTCz with an Ar(A–D)₂ framework was designed and synthesized as photovoltaic donor materials, in which 2,7-pyrene (Py) and benzothiadiazole (BT) were respectively used as central aryl (Ar) and arm acceptor (A), while 3-carbazole (Cz) as terminal donor (D). For comparison, an A–Ar–A type SM of Py-2DTBT without Cz terminal unit was also prepared. The effects of Cz on optical, electrochemical, hole mobility and photovoltaic properties were investigated. In solution-processed solar cells, it was observed that the Py-2DTBTCz based devices show significant improvement in photovoltaic performance compared to those of Py-2DTBT. Power conversion efficiency (PCE) of Py-2DTBTCz could be as high as 2.89% with a short-circuit current density (J_sc) of 7.68?mAcm^?2. The results indicate that appending an enlarged Cz π-system to the terminal of A–Ar–A-type small molecules for the construction of an Ar(A–D)₂ framework can significantly improve the photovoltaic performance of SMs.     

Neue Alkalimetall‐Koordinationen durch chelatisierende Siloxazaneinheiten in Verbindungen der Formel [X–N–SiMe2–O–SiMe2–N–X]2M4

New Alkali Metal Coordinations by Chelating Siloxazane Units within Molecules of the General Formula [X–N–SiMe₂–O–SiMe₂–N–X]₂M₄ New solvent free alkali metal amides with Si–O–Si bridges of the general formula [X–N–SiMe₂–O–SiMe₂–N–X]₂M₄ (X = ^tBu ( 1 ), SiMe₃ ( 2 ), SiMe₂^tBu ( 3 ) with M = Li; X = ^tBu ( 4 ), SiMe₃ ( 5 ) with M = Na; X = ^tBu mit M = K, Li ( 6 )) have been synthesised and characterised by spectroscopic means. X‐ray structure analyses of the six metal derivatives reveal a common structural principle: the four metal atoms within the molecules are incorporated between two molecular halfs and form the bonding links between the two parts. The central molecular skeleton of the molecular halfs consists of a zig‐zag chain N–Si–O–Si–N. This chain is connected to the second one either ideally or approximately by S₄ (4) symmetry. The point symmetries within the crystal are either S₄ (4) (compounds 2 and 4 ), C₂ (2) (compound 6 ), and C₁ (1) (compounds 3 and 5 ). Compound 1 is special in different aspects: the molecule has the high crystallographic point symmetry D_2d (4m2) and the lithium atoms occupy split atom positions (in a similar way as in compound 2 ). The high symmetry of 1 as well as the split atom positions of the lithium atoms are a consequence of dynamics within the crystal.     

Synthesis,Structure of Zwitterionic 2‐Amino‐N′‐(imidazolidin‐2‐ylidene)benzohydrazides,and Their Transformation into 3‐(Imidazolidin‐2‐ylideneamino)quinazolin‐4(1H)‐one Derivatives

The reaction of 2‐chloro‐4,5‐dihydroimidazole ( 5 ) with 2‐aminobenzohydrazides 6a–e led to the formation of 2‐amino‐N′‐(imidazolidin‐2‐ylidene)benzohydrazides as zwitterions 7a–e , which on treatment with carbon disulfide in the presence of triethylamine afforded 3‐(imidazolidin‐2‐ylideneamino)‐2‐thioxo‐2,3‐dihydroquinazolin‐4(1H)‐ones 8a–e . Compounds 8a–d were further converted into the corresponding 3‐(imidazolidin‐2‐ylideneamino)quinazoline‐2,4(1H,3H)‐diones 9a–d using hydrogen peroxide–sodium hydroxide solution. The structures of the compounds prepared were established by elemental analyses, IR and NMR spectra as well as X‐ray crystallographic analyses of 7e and 9a .     

Heteroleptic [Cu(NN)P2]+-type cuprous complexes and their structural modulation on phosphorescent color: Synthesis,structural characterization,properties, and theoretical calculations

Four new heteroleptic [Cu(NN)P₂]⁺-type cuprous complexes— 1 -TPP, 2 -POP, 3 -Xantphos, and 4 -DPPF—were designed and synthesized using a diimine ligand 2-(2′-pyridyl)benzoxazole (2-PBO) and different phosphine ligands (TPP, triphenylphosphine; POP, bis[2-(diphenylphosphino)phenyl]ether; Xantphos, 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene; DPPF, 1,1′-bis(diphenylphosphino)-ferrocene). All complexes were characterized using single-crystal X-ray diffraction, spectroscopic analysis (infrared, UV–Vis.), elemental analysis, and photoluminescence (PL). Single-crystal X-ray diffraction revealed complexes 1 – 4 as isolated cation complex structures with a tetrahedral CuN₂P₂ coordination geometry and diverse P–Cu–P angles. Their UV–Vis. absorption spectra exhibited a blue-shift sequence in wavelength with an enlarged P–Cu–P angle from 4 to 2 then to 3 and then to 1 . The PL emission peaks of 1 – 3 also exhibited a similar blue-shift sequence ( 2 → 3 → 1 ). Their PL lifetime in microseconds (~7.5, 5.1, and 4.7 μs for 1 , 2 , and 3 , respectively) indicated that their PL behavior represents phosphorescence. Time-dependent density functional theory (TD-DFT) calculation and wavefunction analysis revealed that S₁ and T₁ states of 1 – 3 should be assigned as metal–ligand and ligand–ligand charge-transfer (ML + L'L)CT states. Their UV–Vis. absorption and phosphorescence should be attributed to the charge transfer from the P–Cu–P segment to the 2-PBO ligand. Therefore, as the P–Cu–P angle increased (lower HOMO), the energy of S₁ and T₁ states also increased, following the change of PL color.     

The Reaction of Diethylthiophosphinyl Iodide,Et2P(S)I,with Nucleophiles

The compound Me₂AsSI can exist in two different forms, either as dimethylarsinosulfenyl iodide [or (iodothio)dimethylarsane)], Me₂As–S–I ( A ), or as dimethylthioarsinyl iodide (or dimethylarsinothioic iodide), Me₂As(S)–I ( B ). To confirm that the structure of the product of the reaction between Bunsen's cacodyl disulfide Me₂As(S)–S–AsMe₂ and iodine is A and not B , the known diethylthiophosphinyl iodide (or diethylphosphinothioic iodide), Et₂P(S)–I ( 2 ) was prepared and its hydrolytic stability and reactivity towards a variety of nitrogen, phosphorus(III), arsenic(III), oxygen, and sulfur(II) nucleophiles were studied. The results indicated that only a few reactions of 2 resembled those of A , thus strengthening the proposal that the reaction of Bunsen's cacodyl disulfide with iodine produced A and not B . A series of ³¹P NMR chemical shifts of diethylthiophosphinyl moiety is also reported. Et₂P(S)–DMAP, synthesized and isolated during the presented study, is the ethyl analogue of Me₂P(S)–DMAP, previously described as an important molecule. In our case, Et₂P(S)–DMAP was found to be a good intermediate for the synthesis of phosphoryl or thiophosphoryl derivatives since it was more reactive than 2 towards nucleophiles.     

Mechanistic Investigation of Catalyst‐Transfer Suzuki–Miyaura Condensation Polymerization of Thiophene–Pyridine Biaryl Monomers with the Aid of Model Reactions

We have investigated the requirements for efficient Pd‐catalyzed Suzuki–Miyaura catalyst‐transfer condensation polymerization (Pd‐CTCP) reactions of 2‐alkoxypropyl‐6‐(5‐bromothiophen‐2‐yl)‐3‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)pyridine ( 12 ) as a donor–acceptor (D –A) biaryl monomer. As model reactions, we first carried out the Suzuki–Miyaura coupling reaction of X–Py–Th–X′ (Th=thiophene, Py=pyridine, X, X′=Br or I) 1 with phenylboronic acid ester 2 by using tBu₃PPd⁰ as the catalyst. Monosubstitution with a phenyl group at Th‐I mainly took place in the reaction of Br–Py–Th–I ( 1 b ) with 2 , whereas disubstitution selectively occurred in the reaction of I–Py–Th–Br ( 1 c ) with 2 , indicating that the Pd catalyst is intramolecularly transferred from acceptor Py to donor Th. Therefore, we synthesized monomer 12 by introduction of a boronate moiety and bromine into Py and Th, respectively. However, examination of the relationship between monomer conversion and the M_n of the obtained polymer, as well as the matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectra, indicated that Suzuki–Miyaura coupling polymerization of 12 with (o‐tolyl)tBu₃PPdBr initiator 13 proceeded in a step‐growth polymerization manner through intermolecular transfer of the Pd catalyst. To understand the discrepancy between the model reactions and polymerization reaction, Suzuki–Miyaura coupling reactions of 1 c with thiopheneboronic acid ester instead of 2 were carried out. This resulted in a decrease of the disubstitution product. Therefore, step‐growth polymerization appears to be due to intermolecular transfer of the Pd catalyst from Th after reductive elimination of the Th‐Pd‐Py complex formed by transmetalation of polymer Th–Br with (Pin)B–Py–Th–Br monomer 12 (Pin=pinacol). Catalysts with similar stabilization energies of metal–arene η²‐coordination for D and A monomers may be needed for CTCP reactions of biaryl D–A monomers.     

Production of HfB<Subscript>2</Subscript>–SiC (10–65 vol % SiC) Ultra-High-Temperature Ceramics by Hot Pressing of HfB<Subscript>2</Subscript>–(SiO<Subscript>2</Subscript>–C) Composite Powder Synthesized by the Sol–Gel Method

The formation of HfB₂–SiC (10–65 vol % SiC) ultra-high-temperature ceramics by hot pressing of HfB₂–(SiO₂–C) composite powder synthesized by the sol–gel method was studied. By the example of HfB₂–30 vol % SiC ceramic, it was shown that the synthesis of nanocrystalline silicon carbide is completed at temperatures of as low as ≥1700°C (crystallite size 35–39 nm). The production of the composite materials with various contents of fine silicon carbide at 1800°C demonstrated that the samples of the composition HfB₂–SiC (20–30 vol % SiC) are characterized by the formation of SiC crystallites of the minimum sizes (36–38 nm), by the highest density (89%), and by higher oxidation resistance during heating in an air flow to 1400°C.     

Synthesis,structure, photophysical,and electrochemical properties of donor–acceptor ferrocenyl derivatives

A series of donor–acceptor compounds 2–6 have been synthesized, via Knoevenagel condensation reaction (using conventional method, as well as microwave method). The ferrocene unit acts as a donor, conjugated phenyl–acetylene linker act as a π-electron relay unit, and malononitrile, cyanoacetic acid, and indanone groups act as acceptor. The electronic absorption spectra displayed a broad intramolecular charge transfer (CT) band in the visible region (450–650 nm). The electrochemical studies suggest considerable donor–acceptor interaction. The single crystal X-ray structure of 2, and 3 are reported, the structure reveals that 2 is nearly planar compared to 3. The supramolecular structure of 2 exhibits intramolecular C–H–π, and C–H–N interaction, which leads to formation of 2D network, whereas compound 3 shows head to tail dimer formation through C–H–π, and π–π interaction.     

Synthesis and Molecular Drug Efficacy of Indoline‐based Dihydroxy‐thiocarbamides: Inflammation Regulatory Property Unveiled over COX‐2 Inhibition,Molecular Docking,and Cytotoxicity Prospects

In this study, substituted indoline‐based dihydroxy‐carbamides ( 5a–i ) were synthesized and evaluated as the cyclooxygenase‐2 (COX‐2) inhibitors to testify their inflammatory regulations through COX‐2 inhibition. Enzyme‐linked immunosorbent assay‐based competitive (COX‐2) inhibition (in vitro) followed by a molecular docking study (in silico) was executed to ensure the mode of interaction between 5a–i and COX‐2. Apart from COX‐2 inhibition studies, free‐radical scavenging ability (H₂O₂ estimation method) and the human red blood cell membrane protection (in vitro anti‐inflammatory) capability of the compounds 5a–i assessment were also evaluated. Excellent antimicrobial and anticancer activity exhibited by thiocarbamide substituted compounds ( 5a–d ) than carbamide ( 5e–i ). In molecular docking studies, the obtained binding affinity values of 5a–i indicated the therapeutic selectivity on COX‐2 (PDB ID: 1CX2) over COX‐1 (PDB ID: 1EQG). Established inhibitory constant (ki) values were found as low as in nanomolar/picomolar against COX‐2. Reliable COX‐2 inhibition of 78–92% and IC₅₀ 0.002–1.28 μM were obtained. Human red blood cell membrane was found to be effectively stabilized/protected by 5a–i up to 98%. Excellent antioxidant property (average radical scavenging 92%) and structure–activity relationship predictions confirmed the druggability potentials of 5a–i as effective, future anti‐inflammatory drugs. The cytotoxicity of the compounds was also unveiled by MTT assay using MCF‐7 (human breast cancer), SW620 (human colon cancer), G361 (human skin cancer), human breast normal cell lines (MCF‐10), and cell lines.     

Alternating copolymerizations of styrene and acrylic monomers initiated with carbanions in the presence of ZnCl2

On electrochemical initiation of alternating copolymerizations of styrene–acrylonitrile (AN) and styrene–diethyl fumarate (DEF) in the presence of ZnCl₂, radical anions of AN–ZnCl₂ and DEF–ZnCl₂ complexes produced at the cathode were assumed to initiate copolymerization. In analogy with the cathode-initiated copolymerization, the radical anions of AN–ZnCl₂ and DEF–ZnCl₂, generated with the carbanions such as sodium naphthalene, disodium α-methylstyrene tetramer dianion, and butyllithium, were also found to produce alternating copolymers of styrene–AN and styrene–DEF. On the contrary, no polymers were obtained from methyl methacrylate (MMA)–styrene and methacrylonitrile (MAN)–styrene in the presence of ZnCl₂ either with carbanions or by electrochemical reduction. Styrene–MAN–ZnCl₂ yielded an alternating copolymer with carbanions upon introduction of oxygen.     

Amine-modified maleic anhydride containing terpolymers for the adsorption of uranyl ion in aqueous solutions

Maleic anhydride–styrene–methyl methacrylate (MA–S–MM) terpolymer was prepared. It was modified by ethylenediamine (EDA) and diethylenetriamine (DETA) in order to get cross-linked polymers bearing carboxyl and amine groups. Modified polymers used as an adsorbent for the removal of UO₂ ²⁺ from water. The characterizations of structures of all the polymers were performed by Fourier transform infrared. The adsorptive features of adsorbents were then investigated for UO₂ ²⁺ in view of dependency on ion concentration, pH, temperature and kinetics. Experimentally obtained isotherms were evaluated with reference to Langmuir, Freundlich and Dubinin–Radushkevich models. The maximum monolayer adsorption capacity for UO₂ ²⁺ was found to be 1.59 and 2.43 mol kg^?1 for EDA–MA–S–MM and DETA–MA–S–MM, respectively. It can be said that the new modified polymers prepared in our laboratory have been suggested as new adsorbents for uranyl ions.     

Soluble polyimides containing 1,4:3,6‐dianhydro‐d‐glucidol and fluorinated units: Preparation,characterization, optical,and dielectric properties

Aiming to develop soluble and colorless polyimides, two novel diamines, 2,5‐bis(2‐trifluoromethyl‐4‐amino‐phenoxy)‐1,4:3,6‐dianhydrosorbitol (2a) and 2,5‐bis(2‐methyl‐4‐amino‐phenoxy)‐1,4:3,6‐dianhydrosorbitol (2b), were designed and synthesized by the reduction of corresponding dinitro monomer which was obtained via solvent‐free melt heating method. Polyimides (PI–(1–5)) containing 1,4:3,6‐dianhydro‐d ‐glucidol fragments were prepared from 2a and five kinds of common dianhydrides and PI–6 was synthesized from 2b and 4,4′‐(hexafluoroisopropylidene)‐diphthalic anhydride (6FDA) via a two‐step thermal imidization. All the polyimides were readily soluble in common polar solvents and could afford flexible, tough, and transparent films with transparency as high as 87% at 450 nm. Meanwhile, PI–(1–6) exhibited unexpectedly low dielectric constants of 2.02–2.52 at 1 MHz. In addition, analogs PI–7 derived from 2,5‐bis(4‐amino‐phenoxy)‐1,4:3,6‐dianhydrosorbitol (2c) and 6FDA and PI–8 derived from 4,4′‐bis(4‐amino‐2‐trifluoromethylphenoxy)biphenyl (2d) and 6FDA were also obtained via a two‐step thermal imidization for comparision with PI–(1–6) on aspects of thermal, mechnical, optical, electrical, and morphological properties. The structure–property relationships of PI–(1–8) were discussed in detail. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3253–3265     

Synthesis,spectroscopy and structure of cis,cis,trans:N,N;P,P;S,S-[bis(triphenylphosphine)] [bis(pyrimidine-2-thiolato)]ruthenium(II)

Reaction of RuCl₂(PPh₃)₃with pyrimidine-2-thione (HpymS) in a 1:2?mol ratio in dry benzene in the presence of triethylamine as base yielded a complex of stoichiometry [Ru(pymS)₂(PPh₃)₂] (1). This has been characterized using analytical data and IR, ¹H, ¹³C and ³¹P NMR spectroscopy. ¹H NMR confirmed the deprotonation of HpymS. ³¹P NMR spectra showed a single peak confirming equivalent P atoms. Complex 1 crystallizes in space group Pī and HpymS acts as a η²-N,S-deprotonated bidentate anionic ligand. The coordination geometry around the Ru center is distorted octahedral with cis dispositions of P atoms, as well as two N atoms of pymS^– and trans S atoms of pymS^–. Important bond distances and angles are: Ru–N, 2.119(2), 2.106(2); Ru–S, 2.4256(8), 2.4413(8); and Ru–P, 2.3266(7), 2.3167(7)?Å; P(2)–Ru(1)–P(1), 96.07(3); N(21)–Ru(1)–N(11), 83.46(9); and S(1)–Ru(1)–S(2), 153.02(3)°.     

Characterization of [2Fe–2S]-Cluster-Bridged Protein Complexes and Reaction Intermediates by use of Native Mass Spectrometric Methods

Many iron–sulfur proteins involved in cluster trafficking form [2Fe–2S]-cluster-bridged complexes that are often challenging to characterize because of the inherent instability of the cluster at the interface. Herein, we illustrate the use of fast, online buffer exchange coupled to a native mass spectrometry (OBE nMS) method to characterize [2Fe–2S]-cluster-bridged proteins and their transient cluster-transfer intermediates. The use of this mechanistic and protein-characterization tool is demonstrated with holo glutaredoxin 5 (GLRX5) homodimer and holo GLRX5:BolA-like protein 3 (BOLA3) heterodimer. Using the OBE nMS method, cluster-transfer reactions between the holo-dimers and apo-ferredoxin (FDX2) are monitored, and intermediate [2Fe–2S] species, such as (FDX2:GLRX5:[2Fe–2S]:GSH) and (FDX2:BOLA3:GLRX5:[2Fe–2S]:GSH) are detected. The OBE nMS method is a robust technique for characterizing iron–sulfur-cluster-bridged protein complexes and transient iron–sulfur-cluster transfer intermediates.