Cooperative Chiral Lewis Base/Palladium-Catalyzed Asymmetric Syntheses of Methylene-Containing δ-Lactams

We herein report a two-step approach for the enantioselective synthesis of novel chiral δ-lactams. By using a cooperative chiral ITU/achiral Pd-catalyst system, this protocol proceeds via an asymmetric α-allylation of activated aryl esters first, followed by an acid-mediated lactam formation. A variety of differently substituted products could be obtained with usually high levels of enantioselectivities and in reasonable yields (16 examples, up to 98 : 2 er and 73 % yield over two steps). In addition, further utilizations of the products via transformations of the exocyclic double bond were successfully carried out as well.

Unexpected Redox Chemistry of P∩N- and As∩N-Rhenium(I) Tricarbonyl Complexes in the Presence of CO2 Acting as an Acid

This study reports on Re tricarbonyl complexes bearing 8-(diphenylphosphanyl)quinoline, P∩N, and 8-(diphenylarsanyl)quinoline, As∩N, as bidendate ligands. We studied the reactivity of these complexes in comparison with fac-Re(N∩N)(CO)3Cl (with N∩N = 2,2'-bipyridine or 4,4'-dimethyl-2,2'-bipyridine). We used a combination of electrochemical and spectroelectrochemical methods with time-resolved spectroscopy over 10 orders of magnitude (100 ps-1 s) to investigate the peculiar reactivity of one-electron-reduced Re(CO)3(P∩N)Cl and Re(CO)3(As∩N)Cl complexes also in the presence of protons.

Aurophilic Molecules on Surfaces. Part II. (NapNC)AuCl on Au(111)

Although aurophilicity is a well-known phenomenon in structural gold chemistry and is found in many crystals of Au(I) complexes, its potential for self-assembly in thin films is not yet explored. This paper is Part II of a study, in which we investigated the ultrathin film formation of chlorido(2-naphthyl isonitrile) gold(I) on gold surfaces. Here, we present the data for the growth of (NapNC)AuCl on isotropic Au(111) surfaces. Already during physical vapor deposition, the condensation of ultrathin films is monitored by photoelectron emission microscopy (PEEM) and incremental and spectrally resolved changes in the optical reflectance (DDRS). Additional structural data obtained by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) reveal that the "crossed swords" packing motif known from the bulk is also present in thin films.

Aurophilic Molecules on Surfaces. Part I. (NapNC)AuCl on Au(110)

Aurophilicity is a well-known phenomenon in structural gold chemistry and is found in many crystals of Au(I) complexes. However, these attractive dispersion forces between and within complexes containing Au(I) moieties have not been well studied in ultrathin films. In this paper, we elucidate the interaction of chlorido(2-naphthyl isonitrile)gold(I) on and with Au(110) surfaces. Already during physical vapor deposition, the condensation of ultrathin films is monitored by photoelectron emission microscopy (PEEM) and by incremental and spectrally resolved changes in the optical reflectance (DDRS). Additional structural data obtained by STM and LEED reveal that the "crossed swords" packing motif known from the bulk is also present in thin films. The molecular arrangement changes several times during thin-film deposition.

Noncovalent Synergy: Aurophilicity and Aryl Stacking in Bis(gold(I)aryl)-dmpm Complexes

Bis(dimethylphosphino)methane (dmpm) was used as a ligand to synthesize four semi-supported dinuclear gold(I) complexes, dmpm(AuR)₂ (R = Cl, C₆H₅, C₆Cl₅, and C₆F₅), which were studied concerning the synergistic effects of two weak noncovalent interactions: aurophilic and aryl-aryl stacking interactions. The chloro-substituted complex was synthesized by the ligand substitution of (tht)AuCl with dmpm and further functionalized by the reaction with PhMgBr or in situ-generated C₆Cl₅Li to afford the phenyl- and pentachlorophenyl-substituted compounds, respectively. The pentafluorophenyl-substituted gold complex was generated by the ligand substitution of (tht)Au(C₆F₅) with dmpm. All complexes were characterized by multinuclear NMR spectroscopy, CHN analyses, and X-ray diffraction experiments. Additionally, the basic photoluminescence properties of dmpm(AuCl)₂, dmpm(AuC₆Cl₅)₂, and dmpm(AuC₆F₅)₂ were examined. The aggregation behavior of dmpm(AuC₆F₅)₂ was further investigated by variable-temperature diffusion-ordered NMR spectroscopy experiments.

Synthesis, structural and photophysical properties of dimethylphosphino(perfluoro-)phenylene-based gold(I) dimers

Starting with 1,2-dibromobenzene and 1,2,3,4-tetrafluorobenzene, dimethyl(2-(trimethylstannyl)phenyl)phosphane, Me₂P(o-C₆H₄)SnMe₃, and dimethyl-[2,3,4,5-tetrafluoro-6-(trimethylstannyl)phenyl]phosphane, Me₂P(o-C₆F₄)SnMe₃, were synthesized and used in tin-gold exchange reactions to prepare two gold(I) dimers, bis[(2-dimethylphosphino)phenyl]di-gold(I), [Au₂(μ-2-C₆H₄PMe₂)₂], and bis[(2-dimethylphosphino)-3,4,5,6-tetrafluorophenyl]di-gold(I), [Au₂(μ-2-C₆F₄PMe₂)₂], respectively. Both tin precursor molecules, as well as the gold(I) complexes, were characterized by multinuclear NMR spectroscopy, CHN analysis and X-ray diffraction experiments. Both gold(I) dimers were further investigated by the means of computational as well as photophysical methods.

Enantioselective organocatalytic syntheses of α-selenated α- and β-amino acid derivatives

Selenium-containing amino acids are valuable targets but methods for the stereoselective α-selenation of simple amino acid precursors are rare. We herein report the enantioselective electrophilic α-selenation of azlactones (masked α-amino acid derivatives) and isoxazolidin-5-ones (masked β-amino acids) using Cinchona alkaloids as easily accessible organocatalysts. A variety of differently substituted derivatives was accessed with reasonable levels of enantioselectivities and further studies concerning the stability and suitability of these compounds for further manipulations have been carried out as well.

Fabrication of a Solution-Processed White Light Emitting Diode Containing a Single Dimeric Copper(I) Emitter Featuring Combined TADF and Phosphorescence

Luminescent copper(I) complexes showing thermally activated delayed fluorescence (TADF) have developed to attractive emitter materials for organic light emitting diodes (OLEDs). Here, we study the brightly luminescent dimer Cu2Cl2(P∩N)2 (P∩N = diphenylphosphanyl-6-methyl-pyridine), which shows both TADF and phosphorescence at ambient temperature. A solution-processed OLED with a device structure ITO/PEDOT:PSS/PYD2: Cu2Cl2(P∩N)2/DPEPO (10 nm)/TPBi (40 nm)/LiF (1.2 nm)/Al (100 nm) shows warm white emission with moderate external quantum efficiency (EQE). Methods for EQE increase strategies are discussed.

A trigonal coordination of Au(I) phosphane complexes stabilized by O-H ⋯ X (X = Cl-, Br-, I-) interactions

In this work, we show that intramolecular hydrogen bonding can be used to stabilize tri-coordinated phosphane-gold(I) complexes. Two molecular structures of 2-(diphenylphosphino)benzoic acid (L) coordinated to a gold(I) atom were determined by single-crystal X-ray diffraction. The linear L-Au-Br shows a standard linear coordination and dimerizes via hydrogen bonds of the carboxylic acid. Upon addition of two additional phosphane ligands the complex [L3Au]X is formed which is stabilized by three intramolecular -C(O)O-H … X hydrogen bonds as proven by the X-ray structure of the respective chlorido-complex. X-ray powder diffractograms suggest the same structure also for X- = Br- and I-.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s00706-021-02843-2.

Green-light photocleavable meso-methyl BODIPY building blocks for macromolecular chemistry

We report the design of easily accessible, meso-methyl BODIPY monomers and their incorporation into photoclippable macromolecules.

Visible Light Photocleavable Ruthenium-Based Molecular Gates to Reversibly Control Release from Mesoporous Silica Nanoparticles

Herein we present hybrid mesoporous silica nanomaterials (MSN) with visible light-sensitive ruthenium complexes acting as gates. Two different [Ru(bpy)₂L1L2]²⁺ complexes were investigated by grafting [Ru(bpy)₂(4AMP)₂](PF₆)₂ (RC1) and [Ru(bpy)₂(PPh₃)Cl]Cl (RC2) via two or one ligands onto the surface of mesoporous silica nanoparticles (MSNs), to give MSN1-RC1 and MSN2-RC2, respectively. The pores were previously loaded with a common dye, safranin O, and release studies were conducted. The number and position of the ligands were shown to influence the photocages behavior and thus the release of the cargo. Release studies from MSN1-RC1 in acetonitrile showed that in the dark the amount of dye released was minimal after 300 min, whereas a significant increase was measured upon visible light irradiation (ca. 90%). While successful as a photochemically-controlled gated system, RC1 was restricted to organic solvents since it required cleavage of two ligands in order to be cleaved from the surface, and in water only one is cleaved. Release studies from the second nanomaterial MSN2-RC2, where the complex RC2 was bound to the MSN via only one ligand, showed stability under darkness and in aqueous solution up to 180 min and, rapid release of the dye when irradiated with visible light. Furthermore, this system was demonstrated to be reversible, since, upon heating to 80 °C, the system could effectively re-close the pores and re-open it again upon visible light irradiation. This work, thus, demonstrates the potential reversible gate mechanism of the ruthenium-gated nanomaterials upon visible light irradiation, and could be envisioned as a future design of photochemically-driven drug delivery nanosystems or on/off switches for nanorelease systems.

Copper(II) complexes bearing cyclobutanecarboxylate and pyridine ligands: a new series of dinuclear paddle-wheel complexes

Four members of a new series of paddle-wheel copper(II) complexes bearing cyclobutanecarboxylate as bridging ligand with pyridine derived ligands in axial positions are reported. They have been characterised by FTIR-ATR, UV–Vis spectroscopy, mass spectrometry, and single crystal X-ray diffraction. The synthesis is straight-forward by combining the carboxylic acid, copper(II) acetate, and a slight excess of a pyridine ligand. The molecular structures of three complexes reveal a coordination mode expected for such type of dinuclear copper(II) carboxylates.

Graphic abstract

Aggregation of Au(i)-complexes on amorphous substrates governed by aurophilicity

In single crystals of 2-naphthylisonitrile-gold(i)-halide (halide = Cl, Br, I) complexes, AuAu distances are found to be significantly shorter than twice the van der Waals radius, indicating attractive interactions between gold atoms in adjacent molecules. In the particular case of the studied 2-naphthylisonitrile-gold(i) complexes, homodimers are the common structural motifs, in which the linearly coordinated gold exhibits a crossed swords arrangement with the Au atoms of two molecules being at the intersection point. The crossed swords motif is preserved upon physical vapour deposition of both the chlorine and bromine derivatives on amorphous substrates like glass and glassy carbon. The determined activation energies of desorption for the chlorine (0.9 eV) and the bromine (1.2 eV) derivative are comparable to that of unsubstituted naphthalene. Using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ion scattering (RBS), we confirmed the chemical integrity of the molecules in thin films and revealed the orientation of the crossed swords dimers with respect to the substrate surface.

Dynamic Supramolecular Ruthenium-Based Gels Responsive to Visible/NIR Light and Heat

A simple supramolecular crosslinked gel is reported with a photosensitive ruthenium bipyridine complex functioning as a crosslinker and poly(4-vinylpyridine) (P4VP) as a macromolecular ligand. Irradiation of the organogels in H2 O/MeOH with visible and NIR light (in a multiphoton process) leads to cleavage of pyridine moieties from the ruthenium complex breaking the cross-links and causing degelation and hence solubilization of the P4VP chains. Real-time (RT) photorheology experiments of thin films showed a rapid degelation in several seconds, whereas larger bulk samples could also be photocleaved. Furthermore, the gels could be reformed or healed by simple heating of the system and restoration of the metal-ligand crosslinks. The relatively simple dynamic system with a high sensitivity towards light in the visible and NIR region make them interesting positive photoresists for nano/micropatterning applications, as was demonstrated by writing, erasing, and rewriting of the gels by single- and multiphoton lithography.

Coumarin-Caged Polyphosphazenes with a Visible-Light Driven On-Demand Degradation

Polymers that, upon photochemical activation with visible light, undergo rapid degradation to small molecules are described. Through functionalization of a polyphosphazene backbone with pendant coumarin groups sensitive to light, polymers which are stable in the dark could be prepared. Upon irradiation, cleavage of the coumarin moieties exposes carboxylic acid moieties along the polymer backbone. The subsequent macromolecular photoacid is found to catalyze the rapid hydrolytic degradation of the polyphosphazene backbone. Water-soluble and non-water-soluble polymers are reported, which due to their sensitivity toward light in the visible region could be significant as photocleavable materials in biological applications.

Palladium complexes containing imino phenoxide ligands: synthesis, luminescence, and their use as catalysts for the ring-opening polymerization of rac-lactide

Abstract

The preparation, structural characterization, luminescence, and catalytic activity of three palladium(II) complexes bearing imino phenoxide ligands are reported. The X-ray studies revealed that the complexes are mononuclear with palladium centres coordinated in a square-planar coordination environment. Two of the complexes are emissive in solution at room temperature. The catalytic activities towards the ring-opening polymerization of rac-lactide (rac-LA) were tested. Polymers with moderate molecular weights and relatively broad dispersity (Ð) were obtained. Kinetic studies revealed that the polymerization followed first-order kinetics.

Graphical abstract

Electronic supplementary material

The online version of this article (10.1007/s00706-017-2119-1) contains supplementary material, which is available to authorized users.

Highly efficient cold-white light emission in a [Au2CuCl2(P∩N)2]PF6 type salt

In the trinuclear, heterometallic cluster compound [Au₂CuCl₂(P∩N)₂]PF₆ metallophilic interactions give rise to very efficient cold-white light emission as a result of at least two thermally non-equilibrated emissive triplet states (one of mainly Cu → py and the other of Au → py character, respectively) with exceptional spin-orbit coupling and short emission lifetimes, which are competitive to Pt^II- and Ir^III-based emitters.

Synthesis of Trifluoroacetyl-Substituted Cyclopropanes Using Onium Ylides

The use of carbonyl-stabilized ammonium- and sulfonium ylides allows for the synthesis of highly-functionalized trifluoroacetyl-substituted cyclopropanes. It turned out that the diastereoselectivities strongly depend on the nature of the chosen ylide and the employed base. The products could be obtained in good yields under operationally simple conditions.

Metallo-Supramolecular Gels that are Photocleavable with Visible and Near-Infrared Irradiation

A photolabile ruthenium-based complex, [Ru(bpy)2 (4AMP)2 ](PF6 )2 , (4AMP=4-(aminomethyl)pyridine) is incorporated into polyurea organo- and hydrogels via the reactive amine moieties on the photocleavable 4AMP ligands. While showing long-term stability in the dark, cleavage of the pyridine-ruthenium bond upon irradiation with visible or near-infrared irradiation (in a two-photon process) leads to rapid de-gelation of the supramolecular gels, thus enabling spatiotemporal micropatterning by photomasking or pulsed NIR-laser irradiation.

Asymmetric Synthesis of 2,3-Dihydrobenzofurans by a [4+1] Annulation Between Ammonium Ylides and In Situ Generated o-Quinone Methides

A highly enantio‐ and diastereoselective [4+1] annulation between in situ generated ammonium ylides and o‐quinone methides for the synthesis of a variety of 2,3‐dihydrobenzofurans has been developed. The key factors controlling the reactivity and stereoselectivity were systematically investigated by experimental and computational means and the energy profiles obtained provide a deeper insight into the mechanistic details of this reaction.

Oxidation Responsive Polymers with a Triggered Degradation via Arylboronate Self-Immolative Motifs on a Polyphosphazene Backbone

Oxidation responsive polymers with triggered degradation pathways have been prepared via attachment of self-immolative moieties onto a hydrolytically unstable polyphosphazene backbone. After controlled main-chain growth, postpolymerization functionalization allows the preparation of hydrolytically stable poly(organo)phosphazenes decorated with a phenylboronic ester caging group. In oxidative environments, triggered cleavage of the caging group is followed by self-immolation, exposing the unstable glycine-substituted polyphosphazene which subsequently undergoes to backbone degradation to low-molecular weight molecules. As well as giving mechanistic insights, detailed GPC and 1H and 31P NMR analysis reveal the polymers to be stable in aqueous solutions, but show a selective, fast degradation upon exposure to hydrogen peroxide containing solutions. Since the post-polymerization functionalization route allows simple access to polymer backbones with a broad range of molecular weights, the approach of using the inorganic backbone as a platform significantly expands the toolbox of polymers capable of stimuli-responsive degradation.

Synthesis, crystal structures and blue emission of zinc(II) halide complexes of 1-alkyl-imidazole and (–)-nicotine

Zn(II) halide complexes of the form L2ZnX2 (X=Cl, Br, I) containing bio-relevant or bio-related ligands like 1-alkyl-imidazoles (alkyl=methyl, ethyl and iso-propyl) or (–)-nicotine are presented. All complexes were characterized by 1H NMR spectroscopy, mass spectrometry and elemental analysis. The molecular structures of the majority of complexes were determined by single crystal X-ray diffraction. The zinc ion exists in a tetrahedral environment coordinated by two halide anions and two nitrogen atoms of the N-heterocycles. Upon photoexcitation the nicotine complexes feature a blue emission which we tentatively assign to phosphorescence.

Copper(II) complexes with imino phenoxide ligands: synthesis, characterization, and their application as catalysts for the ring-opening polymerization of rac-lactide

ABSTRACT

Four new copper complexes based on bidentate imino phenoxide ligands were synthesized and characterized by IR, UV-Vis spectroscopy, ESI mass spectrometry, single crystal X-ray diffraction, and electrochemistry. The crystal structures revealed that the copper(II) atoms are surrounded by phenolate oxygen and imine nitrogen atoms of two ligands in a distorted square-planar geometry. The existence of ligand-centered, as well as Cu(II)-centered quasi-reversible and reversible redox reactions are observed in the cyclic voltammetry experiments of all the complexes. All complexes are able to catalyze the ring-opening polymerization of rac-lactide yielding polymers with moderate molecular weights and moderately broad molecular weight distributions.

GRAPHICAL ABSTRACT

N-Methylmelamines: Synthesis, Characterization, and Physical Properties

N-Methylmelamines have recently gained importance as valuable compounds for manufacturing modified melamine formaldehyde resins and other polymer building blocks. A great advantage of these polymers is the reduction of the carcinogenic formaldehyde. Selecting the polymerization processes (e.g., substance polymerization, polymerization in solution) and controlling the polymerization reaction and properties of these novel materials requires knowledge of the properties of the individual melamine derivatives used as new building blocks. All possible permutations of N-methylmelamines were prepared, and reaction progress was monitored by GC/MS. 2,4,6-Tris(dimethylamino)-1,3,5-triazine was prepared to complete the series; this is, however, also a possible byproduct in various synthesis routes. The reaction conditions were optimized to obtain high yields of each derivative with the highest possible purity. The substances were characterized by NMR and IR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray diffraction. In addition, physical properties, such as solubility, melting points, and pKb values, were determined. The number of amino-, methylamino-, and dimethylamino groups has a significant effect on these properties. In summary, we found that by increasing the number of amino- and methylamino groups, solubility and pKb increase. With increasing number of amino groups, the compounds tend to form hydrogen bonds, and thus, the melting point shifts to higher temperature ranges where they start to decompose.

Synthesis and structural characterization of titanium and zirconium complexes containing half-salen ligands as catalysts for polymerization reactions

Ti(iv) and Zr(iv) complexes of tridentate half-salen ligands were synthesized for the polymerization of lactide and ε-CL, homopolymerization, copolymerization and coupling of epoxides with CO₂. All the complexes were found to be effective catalysts for different polymerization reactions.

Asymmetric syntheses of three-membered heterocycles using chiral amide-based ammonium ylides

Phenylglycinol serves as a powerful chiral auxiliary in ammonium ylide-mediated reactions to obtain chiral epoxides/aziridines with excellent stereoselectivities.

The use of carbonyl-stabilised ammonium ylides to access chiral glycidic amides and the corresponding aziridines has so far been limited to racemic trans-selective protocols. We herein report the development of an asymmetric approach to access such compounds with high levels of stereoselectivity using easily accessible chiral auxiliary-based ammonium ylides. The use of phenylglycinol as the chiral auxiliary was found to be superior to Evans or pseudoephedrine-based auxiliaries resulting in good to excellent stereoselectivities in both, epoxidation and aziridination reactions.

Hemi- and holo-directed lead(II) complexes in a soft ligand environment

To investigate the geometry and stereochemical activity of the lone pair at the lead atom, lead(ii) complexes () with one tripodal (L(1)), one dipodal (L(2)) boron-centred soft ligand and eight other small soft heterocyclic ligands, 2-mercaptobenzimidazole (L(3)), 2-mercapto-5-methylbenzimidazole (L(4)), 3-mercapto-1,2,4-triazole (L(5)H), 3-mercapto-4-methyl-1,2,4-triazole (L(6)), 2-mercapto-1,3,4-thiadiazole (L(7)H), 2-mercapto-5-methyl-1,3,4-thiadiazole (L(8)H), 5-mercapto-1-methyltetrazole (L(9)H) and 2-mercapto-4-phenylthiazole (L(10)H) were prepared. The structures of these complexes were elucidated on the basis of X-ray crystallography, elemental analyses as well as (1)H NMR, (1)H DOSY, (13)C NMR and (207)Pb NMR spectroscopy. The coordination numbers of these complexes vary from 4 to 8. The majority of the complexes are polymeric and possess a hemi-directed environment around the lead atoms. Solution studies revealed that most of the complexes are dissociated in highly polar solvents. Most of the complexes are emissive both under ambient conditions and at 77 K in the solid state. However, no obvious relationship between their solid state structures and luminescence behaviour with respect to the nature of the excited state could be identified.

Synthesis and Characterization of Silver(I) and Gold(I) Complexes Bearing a Pyrido-annelated N-Heterocyclic Carbene: A Rare Example of a Cocrystal Containing Two Different Gold(I) Complexes

The cyclohexyl-substituted imidazo[1,5-a]pyridin-2-ium hexafluorophosphate, 2a, has been prepared as precursor for the respective pyrido-annelated N-heterocyclic carbene. [(NHC)2Ag]PF6, 3, has been synthesized by the reaction of 2a with AgCl=KOH in dichloromethane (DCM). Unexpectedly, the reaction of 3 with (tht)AuBr yielded both (NHC)AuBr and [(NHC)Au(tht)]PF6 which formed a 1 : 1 cocrystal (4a,b). The complexes are aggregated to infinite chains, which are governed by both π-π stacking and weak aurophilic interactions. Subsequent oxidation of the co-crystalline material with CsBr3 gave (NHC)AuBr3, 5. All compounds were characterized by NMR spectroscopy, mass spectrometry and elemental analysis. Additionally, compounds 2a and 5 were investigated by electronic spectroscopy: 2a behaves like a typical aromatic compound exhibiting absorption and fluorescence bands attributable to π-π* transitions. The Au(III) complex 5 exhibits ligand-centered fluorescence at room temperature and both ligand-centered fluorescence and a weak phosphorescence at 77 K.

Highly efficient luminescence of Cu(I) compounds: thermally activated delayed fluorescence combined with short-lived phosphorescence

Luminescent materials showing thermally activated delayed fluorescence (TADF) have gained high attractiveness as emitters in organic light emitting diodes (OLEDs) and other photonic applications. Nevertheless, even utilization of TADF can be further improved, introducing a novel concept. This is demonstrated by a new class of brightly luminescent low-cost Cu(I) compounds, for which the emission stems from both the lowest excited triplet T1 and singlet S1 state. At T = 300 K, these materials exhibit quantum yields of more than ΦPL = 90% at short emission decay times. About 80% of the emission intensity stems from the singlet due to TADF, but importantly, an additional 20% is contributed by the lower lying triplet state according to effective spin-orbit coupling (SOC). SOC induces also a relatively large zero-field splitting of the triplet being unusual for Cu(I) complexes. Thus, the overall emission decay time is distinctly reduced. Combined use of both decay paths opens novel photonic applications, in particular, for OLEDs.

Hydrogen-bonded diketopyrrolopyrrole (DPP) pigments as organic semiconductors

Diketopyrrolopyrroles (DPPs) have recently gained attention as building-blocks for organic semiconducting polymers and small molecules, however the semiconducting properties of their hydrogen-bonded (H-bonded) pigment forms have not been explored. Herein we report on the performance of three archetypical H-bonded DPP pigments, which show ambipolar carrier mobilities in the range 0.01-0.06 cm²/V s in organic field-effect transistors. Their semiconducting properties are correlated with crystal structure, where an H-bonded crystal lattice supports close and relatively cofacial π-π stacking. To better understand transport in these systems, density functional theory calculations were carried out, indicating theoretical maximum ambipolar mobility values of ∼0.3 cm²/V s. Based on these experimental and theoretical results, H-bonded DPPs represent a viable alternative to more established DPP-containing polymers and small molecules where H-bonding is blocked by N-alkylation.

Synthesis, structural and photo-physical studies of bismuth(III) complexes with Janus scorpionate and co-ligands

Some novel complexes of bismuth(III) with the Janus scorpionate ligand [HB(mtda(Me))3](-) (mtda(Me) = 2-mercapto-5-methyl-1,3,4-thiadiazolyl) were synthesised. Na[HB(mtda(Me))3] (1) was reacted with BiX3 (X = Cl, I, NO3) in the molar ratio 2 : 1 to afford the bismuth complexes {HB(mtda(Me))3}2BiCl (3), Na[{HB(mtda(Me))3}2BiI2] (4) and [{HB(mtda(Me))3}2Bi(NO3)]n (5). Two mixed complexes {HB(mtda(Me))3}Bi(phen)Cl2 (6) and {HB(mtda(Me))3}Bi(bipy)Cl2 (7) were obtained using Janus scorpionate as the primary ligand in the presence of 1,10-phenanthroline and 2,2'-bipyridyl, respectively, as co-ligands in the 1 : 1 ratio. The obtained complexes were characterised by (1)H, (13)C and diffusion NMR (DOSY), elemental analyses and mass spectrometry. Structures of the compounds NBu4[HB(mtda(Me))3] (2), 3, 4, 5, 6 and 7 were determined by single crystal X-ray diffraction. The molecular dynamic process in complex 3 was also studied by variable temperature NMR measurements. All bismuth complexes, except for the polymeric 5, are monomeric. Complexes 6 and 7 exhibit (B)H···Bi distances of 2.76(3) and 2.71(2) Å length, respectively. Compounds 2, 6 and 7 were screened for their luminescence activity. At 77 K in ethanol solution, complexes 6 and 7 exhibit phosphorescence from ligand-to-ligand charge transfer (LLCT) and the ligand-centred (LC) excited state, respectively.

Photoreductive generation of amorphous bismuth nanoparticles using polysaccharides--bismuth-cellulose nanocomposites

A simple and highly reproducible synthesis of amorphous bismuth nanoparticles incorporated into a polysaccharide matrix using a photoreduction process is presented. As precursor for the generation of the Bi nanoparticles, organosoluble triphenylbismuth is used. The precursor is dissolved in toluene and mixed with a hydrophobic organosoluble polysaccharide, namely trimethylsilyl cellulose (TMSC) with high DSSi. The solution is subjected to UV exposure, which induces the homolytic cleavage of the bismuth-carbon bond in BiPh3 resulting in the formation of Bi(0) and phenyl radicals. The aggregation of the Bi atoms can be controlled in the TMSC matrix and yields nanoparticles of around 20 nm size as proven by TEM. The phenyl radicals undergo recombination to form small organic molecules like benzene and biphenyl, which can be removed from the nanocomposite after lyophilization and exposure to high vacuum. Finally, the TMSC matrix is converted to cellulose after exposure to HCl vapors, which remove the trimethylsilyl groups from the TMSC derivative. Although TMSC is converted to cellulose, the formed TMS-OH is not leaving the nanocomposite but reacts instead with surface oxide layer of the Bi nanoparticles to form silylated Bi nanoparticles as proven by TEM/EDX.

Gold(I) Complexes Bearing P∩N-Ligands: An Unprecedented Twelve-membered Ring Structure Stabilized by Aurophilic Interactions

The P∩N-ligands Ph2Pqn, 1, Ph2 Piqn, 2, Ph2 Ppym, 3, and the As∩N-ligands Ph2Asqn, 4, Ph2Asiqn, 5, (Ph = phenyl, qn = 8-quinoline, iqn = 1-isoquinoline, pym = 2-pyrimidine) have been synthesized, the ligands 2 and 5 for the first time. Their ligand properties were probed by the synthesis of gold(I) complexes. Reaction with (tht)AuCl (tht = tetrahydrothiophene) yielded the chlorogold complexes Ph2RP-Au-Cl (R = qn, 6; iqn, 7; pym, 8) and Ph2RAs-Au-Cl (R = qn, 9; iqn, 10) in high yields. Further treatment of 7 and 8 with one equivalent of AgBF4 provided the complexes [(Ph2Piqn)Au]BF4, 11, [(Ph2Ppym)Au]BF4, 12, and [(Ph2Piqn)Au(tht)]BF4, 14. For comparison, the previously reported complex [(Ph2Ppy)Au]BF4 (py = pyridine), 13, was re-investigated. The compounds were characterized by elemental analyses, mass spectrometry and NMR spectroscopy. In addition, the solid-state structures of 2, 3, 6, 7, 9 - 14 have been determined by X-ray crystallography. The chloro-gold compounds crystallize in the common rod-like structure known from R3EAuCl (R = aryl, E = P, As) complexes without further aggregation via aurophilic interactions. In all cases the phosphine acts as a monodentate ligand. In the solid state compounds 11 - 13 feature an unprecedented cyclic trinuclear aggregation pattern, in which the Au(I) atoms are linearly coordinated by the bridging phosphine ligands forming a cyclic (P-Au-N)3 arrangement. The resulting twelvemembered ring is further stabilized by Au · · · Au interactions. Due to the presence of these Au · · · Au contacts, 11 - 13 are emissive in the solid state but not in solution

Synthesis, Characterization and Luminescence of Silver(I) and Gold(I) Complexes Bearing a Diethyl Acetal Functionalized N-Heterocyclic Carbene

1-(2,2ʹ-Diethoxyethyl)-3-methyl-imidazolium bromide, 1, has been prepared and used as a precursor for the synthesis of the corresponding silver bromide complex [(NHC)2Ag][AgBr2], 2. Transmetallation of 2 with (tht)AuBr (tht = tetrahydrothiophene) yields (NHC)AuBr, 3. The solid-state structures of 2 and 3 have been determined by single-crystal X-ray diffraction revealing a loose aggregation of the complexes by weak metal-metal interactions. Due to the presence of these contacts, both complexes are emissive in the solid state.

Synthesis and Characterization of Novel Re(BIAN)(CO)3Cl Derivatives Including the First Example of a Water-soluble Tricarbonyl Rhenium(I) Complex with Bis(imino)acenaphthene Ligands

A series of rhenium(I) carbonyl chloride complexes carrying bis(imino)acenaphthene (BIAN) molecules as p-acceptor ligands was prepared and characterized by various spectroscopic techniques. Among the novel compounds described, the remarkable example of a deeply colored water-soluble rhenium carbonyl derivative is presented. The crystal structures of this family of BIAN compounds are also reported, which confirm the position of the chloro ligand at the tricarbonyl rhenium(I) center. In the case of BIAN ligands carrying bulky substituents in the ortho-position of the arylimino subunits, evidence has been found for an exchange of the halide ligand in solution, which is considered to be of major relevance for catalytic applications. Implications of our results for the fields of photocatalytic CO2 reduction and the controlled release of the gasotransmitter CO in aqueous solution are briefly discussed.