Ball-milling toward nickel(II) diphosphine complexes for direct use in catalysis.

Mechanochemistry turned out to be a powerful synthetic tool enabling the first efficient synthesis of nickel(II) complexes with diphosphine.). It has been demonstrated that solventless ball-milling of nickel(II) halides with diphosphines leads to the [NiX2(diphosphine)] type compounds, which can be directly used in catalysis without any purification. Moreover, it was confirmed that despite the presence of impurities in the resulting complexes, their catalytic activity remains identical to those obtained via traditional solvent-based methods.

Solvent-Free and Efficient Synthesis of Silatranes via an Organocatalytic Protocol under Mild Conditions.

The organocatalytic approach to the formation of silatranyl cages permitted the design of a solvent-free and efficient protocol for the preparation of various organosilatranes. We discovered that amidine derivatives efficiently catalyze the conversion of trialkoxysilanes into organosilatranes, and their catalytic activity is related to the pKBH+ values. NMR studies of equimolar reactions of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) with selected substrates allowed proposing a reliable scheme for the transesterification process and silatranyl cage formation. In addition, green chemistry metrics for the scaled-up synthesis of vinylsilatrane (3k) were appointed. Finally, a scheme for the industrial production of silatrane derivatives with DBU and solvent regeneration was proposed, supported by a catalyst recycling experiment.

Synthesis of bifunctional disiloxanes via subsequent hydrosilylation of alkenes and alkynes.

The first protocol for the synthesis of unsymmetrical bifunctional 1,1,3,3-tetramethyldisiloxane derivatives via subsequent hydrosilylation of alkenes and alkynes is presented. The methodology described has vast functional group tolerance and is extremely efficient towards the formation of novel disiloxane-based building blocks.

A library of new bifunctional alkenes obtained by a highly regiodivergent silylation of 1,5-hexadiene.

An efficient methodology for the synthesis of two groups of silicon-containing alkenes is reported. It includes a highly regioselective functionalization of 1,5-hexadiene through hydrosilylation and dehydrogenative silylation with organofunctional silanes and siloxanes. The established conditions enable selective monofunctionalization of 1,5-hexadiene regardless of the organosilicon modifier used as well as the type of functional group bonded to the silicon-based compound. All products were isolated and fully characterized by NMR spectroscopy and MS techniques.

A substituent-induced post-assembly modification cascade of a metallosupramolecular imine-type Co-complex.

Here, we report a reaction cascade employing the substituent-induced post-assembly modification of a Co(iii) complex. Unexpectedly, we found that the (triisopropylsilyl)alkynyl moiety introduced to the Sonogashira reaction with the bromo-functionalized Co(iii) assembly plays a "Trojan horse" role, triggering a subsequent, second step of the cascade, i.e. Co(iii) to Co(ii) reduction. The reported substituent-activated Sonogashira-redox cascade reaction might set a new direction in the construction of specific chemical sensors.

Pt(0)-Catalysed synthesis of new bifunctional silanes.

We report herein very efficient syntheses of new functional silanes obtained via olefin hydrosilylation. New bifunctional compounds contain attractive functional groups such as epoxy, fluoroalkyl, trisilylamine, chloropropyl, and methacroiloxy which can play different roles in molecular systems. Moreover, the catalytic system proposed by us exhibits high selectivity and tolerance to a wide range of functional groups. It also permitted obtaining total conversions of the starting reagents in a relatively short time under mild conditions.

Microwave-Accelerated C,N-Cyclometalation as a Route to Chloro-Bridged Iridium(III) Binuclear Precursors of Phosphorescent Materials: Optimization, Synthesis, and Studies of the Iridium(III) Dimer Behavior in Coordinating Solvents.

We present the results of our research on the use of microwaves as an unconventional heat source for the acceleration of iridium(III) chloro-bridged dimer preparation. The results enabled us to revise and improve known guidelines for the very quick and highly efficient synthesis of iridium(III) dimeric complexes in a very simple isolation manner. According to the developed methodology, the already known dimers containing ligands based on the 2-phenylpyridinato motif, as well as new ones stabilized with functionalized benzo[h]quinolinato and 2-phenoxypyridinato-based ligands, were efficiently synthesized. The scope of the incorporated ligands included compounds equipped with electron-donating (-Me, -OMe, -OPh, -NMe2), electron-withdrawing (-F, -Br, -CF3, -C6F5), and hole-transporting (-NPh2, -C6H4NPh2) groups. The obtained complexes were characterized by NMR, X-ray diffraction, and electrospray ionization mass spectrometry methods, and their behavior was examined in the presence of coordinating solvents such as dimethyl sulfoxide and acetonitrile. Investigation of the interactions between the above-mentioned solvents and dimers enabled us to confirm the ability of the former to cleave µ-chloride bridges, which enriches the knowledge in the field of organometallic chemistry. This knowledge can be particularly useful for the scientists working in the field of iridium-based materials, helping to avoid misinterpretation of the spectroscopic data.

2-Thiohydantoin Moiety as a Novel Acceptor/Anchoring Group of Photosensitizers for Dye-Sensitized Solar Cells.

Very recently, we have reported the synthesis and evaluation of biological properties of new merocyanine dyes composed of triphenylamine moiety, π-aromatic spacer, and rhodanine/2-thiohydantoin-based moiety. Interestingly, 2-thiohydantoin has never been studied before as an electron-accepting/anchoring group for the dye-sensitized solar cells (DSSCs). In the presented study, we examined the applicability of 2-thiohydantoin, an analog of rhodanine, in DSSC technology. The research included theoretical calculations, electrochemical measurements, optical characterization, and tests of the solar cells. As a result, we proved that 2-thiohydantoin might be considered as an acceptor/anchoring group since all the compounds examined in this study were active. The most efficient device showed power conversion efficiency of 2.59%, which is a promising value for molecules of such a simple structure. It was found that the cells' performances were mainly attributed to the dye loading and the ICT molecular absorption coefficients, both affected by the differences in the chemical structure of the dyes. Moreover, the effect of the aromatic spacer size and the introduction of carboxymethyl co-anchoring group on photovoltaic properties was observed and discussed.

Effect of ß-Ketoiminato Ancillary Ligand Modification on Emissive Properties of New Iridium Complexes.

A series of new bis(benzo[h]quinolinato) Ir(III) complexes with modified ß-ketoiminato ancillary ligands were synthesized, and their electrochemical, photophysical properties were determined with the support of theoretical calculations. Moreover, all the synthesized heteroleptic Ir(III) complexes were examined as dopants of the host-guest type emissive layers in solution-processed phosphorescent organic light emitting diodes (PhOLEDs) of a simple structure. As expected on the basis of voltammetry measurements as well as DFT calculations, all the compounds appeared to be green emitters. Their examination showed that alteration of ß-ketoiminato ligand structure causes frontier orbitals' energy levels to be slightly changed, while significantly affecting photoluminescence and electroluminescence efficiencies of iridium phosphors containing these ligands. It was also found that modification of ancillary ligands might enhance charge trapping on the dopant, thus increasing its efficiency, especially in electroluminescence. From among the iridium complexes studied, the compound bearing 1-naphthyl group bonded to the nitrogen atom of the ancillary ligand proved to be the most efficient emitter. The PhOLED fabricated on the basis of this dopant has reached a luminance level of 16000 cd/m2, current efficiency close to 12 cd/A, and an external quantum efficiency around 3.2%.

Quantum-chemical studies of homoleptic iridium(III) complexes in OLEDs: fac versus mer isomers.

A series of facial fac-[Ir(5-R-bzq)3] and meridional mer-[Ir(5-R-bzq)3] Ir(III) complexes bearing benzo[h]quinoline-based ligands have been studied with the help of density functional theory (DFT) methods. A detailed electronic structure comparison of the two isomers has been addressed to point out the differences in their stability and photophysical properties. An influence of substituent impact on optical and electronic properties of Ir(III) homoleptic complexes was also explored by introducing into the cyclometalated ligands substituents characterized with different electronic properties, e.g., R = H, F, OPh, NMe2, C6F5, and p-C6H4-NPh2. The results herein show that fac and mer isomers exhibit remarkable differences in stability and photophysical properties. The introduction of different functional groups into bzq ligands, despite very similar geometrical structures, significantly affected HOMO and LUMO energy levels and energy gaps of the examined Ir(III) complexes.

Pt-Catalyzed Hydrosilylation of 1,3-Diynes with Triorganosilanes: Regio- and Stereoselective Synthesis of Mono- or Bis-silylated Adducts.

An efficient method has been successfully developed for the functionalization of various 1,3-diynes by the hydrosilylation reaction with triethyl- or triphenylsilane catalyzed by Pt catalysts (Pt2(dvs)3, PtO2, or Pt(PPh3)4). Comprehensive optimization studies were performed for the first time to find suitable process conditions for the stereo- and regioselective formation of mono- or bis-silylated adducts from commercially available substrates and catalysts. Silyl-substituted 1,3-enynes or bis-silyl-functionalized buta-1,3-dienes were obtained with excellent yields and fully characterized.

Highly efficient microwave synthesis of rhodanine and 2-thiohydantoin derivatives and determination of relationships between their chemical structures and antibacterial activity.

Here we report studies on the synthesis of 12 new heterocyclic derivatives that differ in three structural motifs and the simultaneous evaluation of the impact of these three variables on the biological properties. The examined compounds are based on rhodanine and 2-thiohydantoin cores equipped with hydrogen or carboxymethyl substituents at the N-3 position and linked to a triphenylamine moiety through 1,4-phenylene, 1,4-naphthalenylene and 1,9-anthracenylene spacers at the C-5 position of the heterocycles. All the compounds were synthesized very quickly, selectively and in high yields according to the developed microwave-assisted Knoevenagel condensation protocol, and they were characterized thoroughly with NMR, FT-IR and ESI-HRMS techniques. The derivatives were tested for their activity against selected strains of Gram-positive and Gram-negative bacteria and yeast. Two compounds showed good activity against Gram-positive bacteria, and all of them showed low cytotoxicity against three cell lines of the human immune system. Based on membrane permeability assays it was demonstrated that the active compounds do not penetrate the cell membrane, and thus they must act on the bacterial cell surface. Finally, we proved that the evaluated structure modifications had a synergistic effect and the simultaneous presence of a 1,4-phenylene spacer and carboxymethyl group at N-3 caused the highest boost in antimicrobial activity.

Iridium complex catalyzed germylative coupling reaction between alkynes and iodogermanes--a new route to alkynylgermanium and alkynylgermasilicon compounds.

The new reaction of terminal alkynes with iodogermanes proceeding in the presence of an Ir(I)-complex [{Ir(µ-Cl)(CO)2}2] (I) and NEt((i)Pr)2, as a hydrogen iodide acceptor, leads to the formation of functionalized alkynylgermanes. This reaction occurs via direct activation of the C(sp)-H bond in the starting alkyne. Detailed stoichiometric experiments using [Ir(cod)(CCPh)(PCy3)] (IVa) and iodogermane were performed and resulted in a proposal of a reasonable mechanism for the germylative coupling reaction between alkynes and iodogermanes.

Synthesis of new styrylarenes via Suzuki-Miyaura coupling catalysed by highly active, well-defined palladium catalysts.

An efficient synthetic route for well-defined palladium(0) complexes [Pd(η(2)-dba)(PPh3)2] (2), [Pd(η(2)-dba)(PCy3)2] (3) and their crystallographic structures is reported. This is the first crystallographic characterization of palladium complexes coordinated with one dibenzylideneacetone and two phosphines. A highly effective, fully controlled method for selective synthesis of mono- (5-9) and distyrylarenes (10-15) via Suzuki-Miyaura coupling is described.

Silsesquioxyl rhodium(I) complexes--synthesis, structure and catalytic activity.

The first bi- and mononuclear rhodium(I) complexes [{Rh(µ-OSi(8)O(12)(i-Bu)(7))(cod)}(2)] (5), [Rh(cod)(PCy(3))(OSi(8)O(12)(i-Bu)(7))] (6) with a hindered hepta(iso-butyl)silsesquioxyl ligand bonded to the rhodium(I) center through Rh-O-Si bonds have been synthesized and their structures have been solved by spectroscopic methods and X-ray analysis. Their exemplary catalytic properties in silylative coupling of vinylsilanes with styrene are also presented.

Application of HS-SPME in the determination of potentially toxic organic compounds emitted from resin-based dental materials.

Leaching of volatile substances from resin-based dental materials may have a potential impact on the biocompatibility as well as safety of these materials. Information from manufacturers on ingredients in the materials is very often incomplete. Patients and dentists may be in contact with components emitted from cured dental fillings or from substrates applied in their preparation. Therefore, determination of the components of these materials is necessary for better prevention from possible harmful effects caused by dental fillings. The aim of this work was the isolation and identification of organic compounds evolved from four commercial resin-modified glass-ionomer cements (resin-based dental materials applied in dentistry) by using an alternative method of volatile compounds analysis-HS-SPME (headspace-solid phase microextraction). Dental materials were heated in closed vial at various temperatures and volatile substances released into the headspace phase above the sample were isolated on a thin polymeric fibre placed in SPME syringe. Identification was performed by using the GC-MS (gas chromatography-mass spectrometry) technique. Almost 50 RMGIC (resin-modified glass-ionomer cement) components (monomers and additives) were identified. The main identified leachables were: iodobenzene (DPICls-diphenyliodonium chloride degradation product), camphorquinone (photo-initiator), tert-butyl-p-hydroxyanisole (inhibitor), 4-(dimethylamino)ethyl benzoate (co-initiator), ethylene glycol dimethacrylate (monomer).

Synthesis of functionalized vinylgermanes through a new ruthenium-catalyzed coupling reaction.

Vinyl-substituted germanes react stereo- and regioselectively with olefins in the presence of complexes containing Ru-H and Ru-Ge bonds with the formation of functionalized vinylgermanes that cannot be synthesized by olefin cross-metathesis procedures. The reaction opens a new catalytic route for preparation of a class of organogermanes that are potent organometallic reagents for organic synthesis because they show very low toxicity and could replace organotin compounds. The mechanism of this new catalytic route was proven to involve an interesting insertion of the vinylgermane into the Ru-H bond and beta-Ge transfer to the metal with elimination of ethylene and generation of an Ru-Ge bond, followed by insertion of the alkene into the Ru-Ge bond and beta-H transfer to the metal to eliminate the substituted vinylgermane.

Alkoxy/siloxy group exchange in the system vinyltrialkoxysilane-iridium(I) siloxide complex.

A study of reactions of dimeric siloxide iridium complex, [[(cod)Ir(mu-OSiMe3)]2] (1) with vinyltriethoxysilane and vinyltrimethoxysilane has revealed a new type of the reation--alkoxy group transfer from silicon to iridium with a simultaneous transfer of a siloxy group from iridium to silicon--as a result of which vinyldialkoxytrimethyldisiloxane and dimeric alkoxide iridium complex [[(cod)Ir(mu-OR)]2] (3) are formed. The structure of [[(cod)Ir(mu-OEt)]2] (3a) has been solved by X-ray diffraction.