2‐(1 H‐1,2,3‐Triazol‐4‐yl)‐Pyridine Ligands as Alternatives to 2,2′‐Bipyridines in Ruthenium(II) Complexes

The synthesis of a variety of 2‐(1H‐1,2,3‐triazol‐4‐yl)‐pyridines by click chemistry is demonstrated to provide straightforward access to mono‐functionalized ligands. The ring‐opening polymerization of ε‐caprolactone initiated by such a mono‐functionalized ligand highlights the synthetic potential of this class of bidentate ligands with respect to polymer chemistry or the attachment onto surfaces and nanoparticles. The coordination to Ru^II ions results in homoleptic and heteroleptic complexes with the resultant photophysical and electrochemical properties strongly dependent on the number of these ligands attached to the Ru^II core.     

Synthesis and X‐ray single‐crystal structure study of 5,5′‐bis(silyl)‐functionalized 3,3′‐dibromo‐2,2′‐dithiophenes

A high‐yield synthesis toward 5,5′‐bis(silyl)‐functionalized 3,3′‐dibromo‐2,2′‐dithiophenes with very efficient work‐up procedure is presented. The molecular structures of two silyl functionalized dibromo‐dithiophenes in the solid state have been determined to investigate the structural influences of different functional groups on the degree of π‐conjugation within the dithiophene moieties, as well as their packing properties. The planar alignment of the tert‐butyldimethylsilyl‐functionalized dibromo‐dithiophene shows a significantly higher degree of conjugation of the π‐system with a more favorable molecular packing than the skewed arrangement of the triisopropylsilyl‐substituted species. Copyright © 2005 John Wiley & Sons, Ltd.     

Hierarchic Supramolecular Interactions within Assemblies in Solution and in the Crystal of 2,3,6,7‐Tetrasubstituted 5,5′‐(Anthracene‐9,10‐diyl)bis[pyrimidin‐2‐amines]

The title compounds 6 and 7 were synthesized in good yield (Schemes 1 and 2), and their mode of assembly was studied both in solution, for the tetrakis(decyloxy) derivative 6 , and in the crystal, for the tetramethoxy analogue 7 . The pyrimidin‐2‐amine moieties of 6 and 7 can engage in three different supramolecular interactions: i) metal ligation via one of the pyrimidine N‐atoms, ii) cooperative double H‐bonding via the NH₂ group, and iii) π–π‐stacking interactions. In solution, coordination of the central Zn‐atom within the soluble porphyrinatozinc complex 19 leads to significant changes in the NMR and absorption spectra of 6 . In the absence of metal ligation, the next strongest interaction is H‐bonding which can operate in nonpolar or moderately polar solvents. In these cases, however, no stacking interaction or inclusion compounds could be put into evidence in the case of 6 by absorption, fluorescence, or NMR spectroscopies. The π‐stacking interactions were only observed in the crystal of 7 in conjunction with double H‐bonding. Slightly disordered DMSO molecules are also H‐bonded to the NH₂ groups of 7 , perturbing the expected packing. The present study illustrates some of the challenges inherent to directing hierarchical assembly processes in the solid state.     

Synthesis of new 2,2′‐disubstituted 5,5′‐dimethyl‐4,4′‐bitriazoles and 2‐(4‐Triazolyl)quinoxalines

Thermal rearrangement of 3‐acylisoxazole arylhydrazones allowed facile preparation of 2H‐1,2,3‐triazoles which were firstly reacted with isoamyl nitrite and then with an opportune arylhydrazine to produce the corresponding α‐hydroxyiminohydrazones 8a‐h . The reaction of compounds 8a‐h with phosphorus pentachloride afforded the desired 4,4′‐bitriazoles 1a‐h . The α‐hydroxyiminoketone derivative 7 or the α‐diketone 14 reacted easily with 1,2‐phenylenediamine to afford 1,2,3‐triazoles 2a‐c bearing the quinoxaline moiety at position 4. Improved yields of the quinoxalines 2a‐c were obtained when 1,2‐phenylenediamine was reacted with the dioxime 15.     

meso‐2,2′‐Di­phenyl‐3,3′,4,4′‐tetra­hydro‐2,2′‐bi­furan‐5,5′(2H,2′H)‐dione

The crystal structure of the title compound, C₂₀H₁₈O₄, contains a crystallographic inversion center. The C—C bond linking the two halves of the mol­ecule is slightly elongated at 1.577 (3) Å.     

Evaluation of N—H…S and N—H…π interactions in O,O′‐diethyl N‐(2,4,6‐trimethylphenyl)thiophosphate: a combination of X‐ray crystallographic and theoretical studies

In the crystal structure of O,O′‐diethyl N‐(2,4,6‐trimethylphenyl)thiophosphate, C₁₃H₂₂NO₂PS, two symmetrically independent thiophosphoramide molecules are linked through N—H…S and N—H…π hydrogen bonds to form a noncentrosymmetric dimer, with Z′ = 2. The strengths of the hydrogen bonds were evaluated using density functional theory (DFT) at the M06‐2X level within the 6‐311++G(d,p) basis set, and by considering the quantum theory of atoms in molecules (QTAIM). It was found that the N—H…S hydrogen bond is slightly stronger than the N—H…π hydrogen bond. This is reflected in differences between the calculated N—H stretching frequencies of the isolated molecules and the frequencies of the same N—H units involved in the different hydrogen bonds of the hydrogen‐bonded dimer. For these hydrogen bonds, the corresponding charge transfers, i.e. lp (or π)→σ*, were studied, according to the second‐order perturbation theory in natural bond orbital (NBO) methodology. Hirshfeld surface analysis was applied for a detailed investigation of all the contacts participating in the crystal packing.     

Semisynthesis of 3′(2′)‐O‐(Aminoacyl)‐tRNA Derivatives as Ribosomal Substrate

An efficient synthesis of (3′‐terminally) 3′(2′)‐O‐aminoacylated pCpA derivatives is described, which could lead to the production of (aminoacyl)‐tRNAs following T4 RNA ligase mediated ligation. The tetrahydrofuranyl (thf) group was used as a permanent protective group for the 2′‐OH of the cytidine moiety which can be removed during the purification of the 3′(2′)‐O‐aminoacylated‐pCpA. This approach allowed for a general synthesis of (3′‐terminally) 3′(2′)‐O‐aminoacylated oligonucleotides. The fully protected pCpA 14 was synthesized by phosphoramidite chemistry and treated with NH₃ solution to remove the 2‐cyanoethyl and benzoyl groups (→ 15 ; Schemes 1 and 2). The 2′‐O‐thf‐protected‐pCpA 15 was coupled with α‐amino acid cyanomethyl esters, and the products 20a – c were deprotected and purified with AcOH buffer to afford 3′(2′)‐O‐aminoacylated pCpA 21a – c in high yields. The 3′(2′)‐O‐aminoacylated pCpA were efficiently ligated with tRNA(? CA) to yield (aminoacyl)‐tRNA which was an active substrate for the ribosome.     

Synthesis and Characterization of 3,3′‐Bis(Dinitromethyl)‐5,5′‐Azo‐1H‐1,2,4‐Triazole

The synthesis of 3,3′‐bis(dinitromethyl)‐5,5′‐azo‐1H‐1,2,4‐triazole ( 5 ) using the readily available starting material 2‐(5‐amino‐1H‐1,2,4‐triazol‐3‐yl)acetic acid ( 1 ) is described. All compounds were characterized by means of NMR, IR, and Raman spectroscopy. The energetic compound 5 was additionally characterized by single‐crystal X‐ray diffraction and DSC measurements. The sensitivities towards impact, friction and electrical discharge were determined. In addition, detonation parameters (e.g. heat of explosion, detonation velocity) of the target compound were computed using the EXPLO5 code based on the calculated (CBS‐4M) heat of formation and X‐ray density.     

All Solid State Chromium(III) Selective Potentiometric Sensor Based on 2‐(1‐(2‐((3‐(2‐Hydroxyphenyl)‐1H‐pyrozol‐1‐yl)methyl)benzyl)‐1H‐pyrazol‐3‐yl)phenol

Highly selective all solid state electrochemical sensor based on a synthesized compound i.e. 2‐(1‐(2‐((3‐(2‐hydroxyphenyl)‐1H‐pyrozol‐1‐yl)methyl)benzyl)‐1H‐pyrazol‐3‐yl)phenol (I) as an ionophore has been prepared and investigated for the selective quantification of chromium(III) ions. The effect of various plasticizers, viz. dibutyl phosphonate (DBP), dibutyl(butyl) phosphonate (DBBP), nitrophenyl octyl ether (NPOE), tris‐(2‐ethylhexyl)phosphonate (TEP), tri‐butyl phosphonate (TBP), dioctyl phthalate (DOP), dioctyl sebacate (DOS), benzyl acetate (BA) and acetophenone (AP) along with anion excluders NaTPB (sodium tetraphenyl borate) and KClTPB (potassium(tetrakis‐4‐chlorophenyl)borate was also studied. The optimum composition of the best performing membrane contained (I):KClTPB:NPOE:PVC in the ratio 15 : 3 : 40 : 42 w/w. The sensor exhibited near Nernstian slope of 20.1±0.2 mV/decade of activity in the working concentration range of 1.2×10^?7–1.0×10^?1 M, and in a pH range of 3.8–4.5. The sensor exhibited a fast response time of 10 s and could be used for about 5 months without any considerable divergence in potentials. The proposed sensor showed very good selectivity over most of the common cations including Na⁺, Li⁺, K⁺, Cu²⁺, Sr²⁺, Ni²⁺, Co²⁺, Ba²⁺, Hg²⁺, Pb²⁺, Zn²⁺, Cs⁺, Mg²⁺, Cd²⁺, Al³⁺, Fe³⁺and La³⁺. The activity of Cr(III) ions was successfully determined in the industrial waste samples by using this sensor.     

NMR analysis of 6‐(2′,3′‐dihydro‐1′H‐inden‐1′‐yl)‐1H‐indene

¹H, ¹³C and two‐dimensional NMR analyses were applied to determine the NMR parameters of 6‐(2′,3′‐dihydro‐1′H‐inden‐1′‐yl)‐1H‐indene. The measurements were accomplished with 0.5 mg of the substance, this quantity being sufficient to determine the chemical shifts of all the H and C atoms, and also the appropriate coupling constants and to give the complete NMR resonance assignments of the molecule. The predicted patterns of the four different H atoms of the methylene groups of the indane structural element coincided completely with the complex patterns in the NMR spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis and functionalization of Poly[5,5′‐(silylene)‐2,2′‐dithienylene]s using silyl triflate intermediates†

Treatment of 5,5′‐dilithio‐2,2′‐dithiophene with (dimethylamino)methylsily bis(triflate)‐ or α, ω‐bis(triflate)‐substituted trisilanes gave poly[5,5′‐(silylene)‐2,2′‐dithienylene]s in high yields. The amino–silyl bond was cleaved selectively by triflic acid, leading to triflate‐substituted derivatives. Conversion of these compounds with nucleophiles gave other functionalized polymers. Platinum‐catalyzed hydrosilylation reactions between silicon–vinyl and silicon–hydrogen derivatives result in polymer networks which may serve as interesting preceramic materials. The structures of the polymers were proven by NMR spectroscopy (²⁹Si, ¹³C, ¹H). Results of thermal gravimetric analysis (TGA), UV spectrometry and conductivity measurements are given. Copyright © 1999 John Wiley & Sons, Ltd.     

Quervernetzung lamellarer Schichten mit Hilfe von (O–H…O)‐Wasserstoffbrücken: Strukturen von M⊕⊖N(SO2C6H4‐4‐COOH)2 (M⊕ = K⊕, Rb⊕, Cs⊕)

Structures of Ionic Di(arenesulfonyl)amides. 4. Cross‐Linking Lamellar Layers by O–H…O Hydrogen Bonds: Structures of M^⊕⊖N(SO₂C₆H₄‐4‐COOH)₂ (M^⊕ = K^⊕, Rb^⊕, Cs^⊕) Syntheses and low‐temperature X‐ray crystal structures are reported for M^IN(SO₂C₆H₄‐4‐COOH)₂, where M = K (monoclinic, space group P2₁/c, Z = 4, Z′ = 1), M = Rb (monoclinic, P2₁, Z = 4, Z′ = 2), or M = Cs (monoclinic, P2₁/c, Z = 4, Z′ = 1). The three compounds are examples of layered inorgano‐organic solids where the inorganic component is comprised of metal cations and N(SO₂)₂ groups and the outer regions are formed by the 4‐carboxy substituted phenyl rings of the folded anions. In the two‐dimensional coordination networks, K^⊕ and Cs^⊕ adopt irregular and chemically distinct [MN₁O₇] octacoordinations, whereas the independent Rb^⊕ cations attain irregular nonacoordinations of type [RbN₂O₇] or [RbO₉] respectively. The crystal packings of the compounds are governed by self‐assembly of parallel layers through exhaustive hydrogen bonding between carboxylic acid groups, resulting in a dense array of cyclic (COOH)₂ motifs within the interlamellar regions.     

Synthesis and Characterization of Bis(triaminoguanidinium) 5,5′‐Dinitrimino‐3,3′‐azo‐1H‐1,2,4‐triazolate – A Novel Insensitive Energetic Material

The synthesis of 5,5′‐diamino‐3,3′‐azo‐1H‐1,2,4‐triazole ( 3 ) by reaction of 5‐acetylamino‐3‐amino‐1H‐1,2,4‐triazole ( 2 ) with potassium permanganate is described. The application of the very straightforward and efficient acetyl protection of 3,5‐diamino‐1H‐1,2,4‐triazole allows selective reactions of the remaining free amino group to form the azo‐functionality. Compound 3 is used as starting material for the synthesis of 5,5′‐dinitrimino‐3,3′‐azo‐1H‐1,2,4‐triazole ( 4 ), which subsequently reacted with organic bases (ammonia, hydrazine, guanidine, aminoguanidine, triaminoguanidine) to form the corresponding nitrogen‐rich triazolate salts ( 5 – 9 ). All substances were fully characterized by IR and Raman as well as multinuclear NMR spectroscopy, mass spectrometry, and differential scanning calorimetry. Selected compounds were additionally characterized by low temperature single‐crystal X‐ray diffraction measurements. The heats of formation of 4 – 9 were calculated by the CBS‐4M method to be 647.7 ( 4 ), 401.2 ( 5 ), 700.4 ( 6 ), 398.4 ( 7 ), 676.5 ( 8 ), and 1089.2 ( 9 ) kJ · mol^–1. With these values as well as the experimentally determined densities several detonation parameters were calculated using both computer codes EXPLO5.03 and EXPLO5.04. In addition, the sensitivities of 5 – 9 were determined by the BAM drophammer and friction tester as well as a small scale electrical discharge device.     

trans‐(Cl)‐[Ru(5,5′‐diamide‐2,2′‐bipyridine)(CO)2Cl2]: Synthesis,Structure, and Photocatalytic CO2 Reduction Activity

A series of trans‐(Cl)‐[Ru(L)(CO)₂Cl₂]‐type complexes, in which the ligands L are 2,2′‐bipyridyl derivatives with amide groups at the 5,5′‐positions, are synthesized. The C‐connected amide group bound to the bipyridyl ligand through the carbonyl carbon atom is twisted with respect to the bipyridyl plane, whereas the N‐connected amide group is in the plane. DFT calculations reveal that the twisted structure of the C‐connected amide group raises the level of the LUMO, which results in a negative shift of the first reduction potential (E_p) of the ruthenium complex. The catalytic abilities for CO₂ reduction are evaluated in photoreactions (λ>400 nm) with the ruthenium complexes (the catalyst), [Ru(bpy)₃]²⁺ (bpy=2,2′‐bipyridine; the photosensitizer), and 1‐benzyl‐1,4‐dihydronicotinamide (the electron donor) in CO₂‐saturated N,N‐dimethylacetamide/water. The logarithm of the turnover frequency increases by shifting E_p a negative value until it reaches the reduction potential of the photosensitizer.     

Surface studies of magnesium oxide‐based catalysts modified with X2 or MgX2 (X = Br,I)

The introduction of a halide (Br, I) onto MgO leads to obtaining catalysts whose catalytic activity in transfer hydrogenation of acrolein with ethanol is significantly higher than that of unmodified MgO. In data found in literature, there is no concise view on how the modification of the surface of MgO with a halide affects its surface properties. Although most of the literature studies indicate a dependence of activity on the initial halide‐containing compound and type of halide, no study comprising both these aspects has been performed. The aim of the present study was to conduct measurements of MgO modified with two halides and with two types of initial halide‐containing compounds with surface‐sensitive techniques to determine how each of these factors influences the surface properties of the catalyst. Titration experiments showed that all of the modified catalysts have a smaller diversity of basic site strengths than unmodified MgO. They also revealed that for all studied systems, the modification of the surface leads to the formation of Brønsted acidic sites, which MgO does not possess. XPS spectra indicate that bromine‐modified catalysts give a broader range of surface species than the appropriate iodine‐modified ones. Moreover, they showed that in the case of both iodine‐modified and bromine‐modified catalysts, the one that exhibited the higher concentration of the appropriate halogen on the surface showed a lower activity in catalytic transfer hydrogenation of acrolein with ethanol. Copyright © 2015 John Wiley & Sons, Ltd.     

2‐(2′‐Pyridyl)‐4,6‐diphenylphosphinine versus 2‐(2′‐Pyridyl)‐4,6‐diphenylpyridine: Synthesis,Characterization, and Reactivity of Cationic RhIII and IrIII Complexes Based on Aromatic Phosphorus Heterocycles

The bidentate P,N hybrid ligand 1 allows access for the first time to novel cationic phosphinine‐based Rh^III and Ir^III complexes, broadening significantly the scope of low‐coordinate aromatic phosphorus heterocycles for potential applications. The coordination chemistry of 1 towards Rh^III and Ir^III was investigated and compared with the analogous 2,2′‐bipyridine derivative, 2‐(2′‐pyridyl)‐4,6‐diphenylpyridine ( 2 ), which showed significant differences. The molecular structures of [RhCl(Cp*)( 1 )]Cl and [IrCl(Cp*)( 1 )]Cl (Cp*=pentamethylcyclopentadienyl) were determined by means of X‐ray diffraction and confirm the mononuclear nature of the λ³‐phosphinine–Rh^III and Ir^III complexes. In contrast, a different reactivity and coordination behavior was found for the nitrogen analogue 2 , especially towards Rh^III as a bimetallic ion pair [RhCl(Cp*)( 2 )]⁺[RhCl₃(Cp*)]^? is formed rather than a mononuclear coordination compound. [RhCl(Cp*)( 1 )]Cl and [IrCl(Cp*)( 1 )]Cl react with water regio‐ and diastereoselectively at the external P?C double bond, leading exclusively to the anti‐addition products [MCl(Cp*)( 1 H ? OH)]Cl as confirmed by X‐ray crystal‐structure determination.     

rac‐ and meso‐3,3′‐Bis(3,5‐di­methyl­phenyl)‐3H,3′H‐2,2′‐biindenyl­idene‐1,1′(2H,2′H)‐dione

In the rac isomer of the title compound, C₃₄H₂₈O₂, the two C—Ph_{di­methyl­phenyl} bond axes make an angle of 58.7 (1)°. There is no short contact between the two 3,5‐di­methyl­phenyl rings, although the dihedral angle between them is 4.93 (7)°. The meso isomer has a center of symmetry at the middle of the C=C bond, and the two C—Ph_{di­methyl­phenyl} bond axes are antiparallel to one another.     

Synthese,Struktur und Eigenschaften von [nacnac]MX3‐Verbindungen (M = Ge,Sn; X = Cl,Br, I)

Synthesis, Structure, and Properties of [nacnac]MX₃ Compounds (M = Ge, Sn; X = Cl, Br, I) Reactions of [nacnac]Li [(2,6‐ⁱPr₂C₆H₃)NC(Me)C(H)C(Me)N(2,6‐ⁱPr₂C₆H₃)]Li ( 1 ) with SnX₄ (X = Cl, Br, I) and GeCl₄ in Et₂O resulted in metallacyclic compounds with different structural moieties. In the [nacnac]SnX₃ compounds (X = Cl 2 , Br 3 , I 4 ) the tin atom is five coordinated and part of a six‐membered ring. The Sn–N‐bond length of 3 is 2.163(4) Å and 2.176(5) Å of 4 . The five coordinated germanium of the [nacnac]GeCl₃ compound 5 shows in addition to the three chlorine atoms further bonds to a carbon and to a nitrogen atom. In contrast to the known compounds with the [nacnac] ligand the afore mentioned reaction creates a carbon–metal‐bond (1.971(3) Å) forming a four‐membered ring. The Ge–N bond length (2.419(2) Å) indicates the formation of a weakly coordinating bond.     

Three Dicyanidometallate(I)‐based Complexes Incorporating Hydrogen‐bonding, π–π Packing and d10–d10 Interactions with Auxiliary 2,2′‐Bipyridyl‐like Ligands

To investigate the influence of the non‐covalent interactions, such as hydrogen‐bonding, π–π packing and d¹⁰–d¹⁰ interactions in the supramolecular motifs, three cyanido‐bridged heterobimetallic discrete complexes {Mn(bipy)₂(H₂O)[Ag(CN)₂]}[Ag(CN)₂] ( 1 ), {Mn(phen)₂(H₂O)[Au(CN)₂]}₂[Au(CN)₂]₂ · 4H₂O ( 2 ), and {Cd(bipy)₂(H₂O)[Au(CN)₂]}[Au(CN)₂] ( 3 ) (bipy = 2,2′‐bipyridine, and phen = 1,10‐phenanthroline), which are based on dicyanidometallate(I) groups with 1:2 stoichiometry of metal ions and 2,2′‐bipyridyl‐like co‐ligands were synthesized and structurally characterized. In compound 1 , hydrogen bonding and π–π interactions governed the supramolecular contacts. In compound 2 , the incorporation of aurophilic, hydrogen bonding and π–π interactions result in a 3D supramolecular network. In compound 3 , hydrogen bonding and π–π stacking interactions result in a 2D supramolecular layer. In the three complexes, hydrogen‐bonding, π–π packing and/or d¹⁰–d¹⁰ interactions can play important roles in increasing the dimensionality of supramolecular assemblies.     

Engineering of UV‐absorbing polypropylene films containing poly(2‐(2′‐hydroxy‐5′‐methacryloxyethylphenyl)‐2H‐benzotriazole) nanoparticles

Ultraviolet‐absorbing nanoparticles (NPs) were prepared by emulsion co‐polymerization of the vinylic monomer 2‐(2′‐hydroxy‐5′‐methacryloxyethylphenyl)‐2H‐benzotriazole (Norbloc?, NB) with the crosslinking monomer divinylbenzene. The effect of total monomer, surfactant, crosslinker, and initiator concentrations on the size and size distribution of the formed NPs was elucidated. The NB monomer and the formed polyNB (PNB) NPs of 19 ± 2 nm were then incorporated into polypropylene (PP) films by melt‐compounding technique by using cast film extrusion. Increasing the PNB NP concentrations integrated within the PP films decreased their UV transmittance. Migration of the UV absorbing PNB NPs from the PP films was not observed during 3 years of storage at room temperature or while exposure to extreme conditions. Under the same conditions, a significant migration was observed for the NB monomer‐containing films. Overall, the PNB NP‐containing films are clear and transparent, although the haze was affected by the addition of NB and PNB NPs. Moreover, the films have good mechanical properties and UV‐blocking quality. Copyright © 2017 John Wiley & Sons, Ltd.