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Two copper(II) complexes, [Cu(bipy)(5-Br-2-hap)(ClO4)]2 (1) and [Cu(bipy)(2-hap)(ClO4)] (2) (where bipy = 2,2′-bipyridine, 5-Br-2-hap = 5-bromo-2-hydroxyacetophenone, 2-hap = 2-hydroxyacetophenone), were synthesized and characterized. The crystal structure of 1 was determined by single crystal X-ray diffraction while 2 was reported earlier. Structural characterization reveals that the presence of bromine in 5-Br-2-hap plays a structure-determining role in dimeric 1 in comparison with the mononuclear 2 where 2-hap was used. Studies of the catalytic potential toward styrene epoxidation in homogeneous system using H2O2 as oxidant reveal that 1 is more efficient than 2 with respect to epoxide selectivity.

The 1,2-bis[(diarylphosphino)ethynyl]benzene derivatives 1a (R=Ph) and 1b (R=o-tolyl) undergo 1,1-carboboration at one of their acetylene units upon treatment with (C6F5)3B at elevated temperature to give the products 5a and 5b, respectively. At room temperature, we observed the formation of the corresponding phosphireniumborate zwitterions, 7a and 7b, respectively, which may be intermediates of the 1,1-carboboration reactions. The reaction of the more bulky 1,2-bis[(dimesitylphosphino)ethynyl]benzene 1c with (C6F5)3B takes a different course. At 110°, we observed the complete conversion to the benzopentafulvene derivative 8 which is probably formed in a typical carbocation rearrangement sequence after the initial (C6F5)3B Lewis acid-addition step. The compounds 5a, 5b, 7b, and 8 were characterized by X-ray crystal-structure analyses.

A series of Ni(II) double stranded binuclear complexes were synthesized upon treating the Ni(II) salts with series of diamino-bis-pyridine ligands, L1H2–L4H2 in 1:1 stiochiometric ratio. The Ni(II) centers existing in octahedral geometry, four of the coordination sites are occupied by two ligand strands, while the remaining two sites are occupied by solvent molecules in each metal centers. The Ni(II) complexes 1a–4a and 1b–4b are binuclear in nature with ClO4 and PF6 counter ions. The crystal structure obtained for complex 1b ascertains the solvent coordination. Solvatochromism though a well established phenomena, such observation is reported first time in the present manuscript in the area of helicate chemistry. Thus the manuscript elicits the solvatochromic property of geometrically unsaturated helicates, by appropriately tuning the d-d transition, adapting suitable solvents.

Phenanthroline-based hexadentate ligands L(1) and L(2) bearing two achiral semicarbazone or two chiral imine moieties as well as the respective mononuclear complexes incorporating various lanthanide ions, such as La(III), Eu(III), Tb(III), Lu(III), and Y(III) metal ions, were synthesized, and the crystal structures of [ML(1)Cl(3)] (M=La(III), Eu(III), Tb(III), Lu(III), or Y(III)) complexes were determined. Solvent or water molecules act as coligands for the rare-earth metals in addition to halide anions. The big Ln(III) ion exhibits a coordination number (CN) of 10, whereas the corresponding Eu(III), Tb(III), Lu(III), and Y(III) centers with smaller ionic radii show CN=9. Complexes of L(2), namely [ML(2)Cl(3)] (M=Eu(III), Tb(III), Lu(III), or Y(III)) ions could also be prepared. Only the complex of Eu(III) showed red luminescence, whereas all the others were nonluminescent. The emission properties of the Eu derivative can be applied as a photophysical signal for sensing various anions. The addition of phosphate anions leads to a unique change in the luminescence behavior. As a case study, the quenching behavior of adenosine-5'-triphosphate (ATP) was investigated at physiological pH value in an aqueous solvent. A specificity of the sensor for ATP relative to adenosine-5'-diphosphate (ADP) and adenosine-5'-monophosphate (AMP) was found. (31)P NMR spectroscopic studies revealed the formation of a [EuL(2)(ATP)] coordination species.

In a chiral-pool synthesis starting from D-mannono-1,4-lactone 1a, the four diastereomeric C-aryl furanosides (1S,4R)-4a, (1S,4S)-4b, (1R,4R)-4c, and (1R,4S)-4d were obtained in a stereocontrolled manner. The key steps of the synthetic pathway comprise a stereoselective reduction of the diastereomeric hemiketals (4R)-2a and (4S)-2b as well as a stereospecific cycloetherification of the resulting diols (1R,4R)-5a, (1S,4R)-5c, and (1S,4S)-5d. This ring closure which led to the desired C-glycosides was achieved by a Mitsunobu reaction or by preparing the 1-O-benzoyl-4-O-methylsulfonyl derivative 7 which was then treated with sodium methoxide. Final hydrolysis of the 5,6-O-isopropylidene protecting group led to the diastereomeric diols (1S,4R)-4a, (1S,4S)-4b, (1R,4R)-4c, and (1R,4S)-4d, representing versatile building blocks for further synthetic transformations.

In the last few years, Rh(III)-catalyzed C H functionalizations have made tremendous progress and, consequently, have recently received increasing attention. These C H activation reactions, generally involving a chelate assisting directing group, have been utilized to form valuable heterocycles and to run useful coupling reactions. In this paper, three different transformations are presented and discussed. In order to unequivocally determine the stereochemistry of some of these transformations, crystal structural analysis data are provided.

A diamine-bridged bis-N-heterocyclic carbene ligand was synthesized as imidazolium salts with chloride or triflate counteranions. Deprotonation of the chloride salt by an iron bis-amide complex or addition of the free diamine-bis-carbene ligand to FeCl2 led to the formation of an Fe(II) dichloride complex having a diamine-bis-carbene ligand, in which the iron atom is in a highly distorted octahedral geometry with weak Fe-N interactions. This iron complex was found to catalyze the hydrosilylation of acetophenone.

D-(+)-Camphor forms the enamine 2 with piperidine. Compound 2 adds HB(C(6)F(5))(2) at the enamine carbon atom C3 to form a Lewis acid/Lewis base adduct (exo-/endo-isomers of 3). Exposure of 3 to dihydrogen (2.5 bar, room temperature) leads to heterolytic splitting of H(2) to form the H(+)/H(-) addition products (4, two diastereoisomers) of the "invisible" frustrated Lewis pairs (5, two diastereoisomers) that were apparently generated in situ by enamine hydroboration under equilibrium conditions.

The intramolecular frustrated P/B Lewis pair Mes2PCH2CH2B(C6F5)2 (7) reacts readily with phenylsilane by heterolytic cleavage of the Si-H bond to give the zwitterion [Mes2(PhH2Si)P+CH2CH2B-H(C6F5)2] (8a), which has been fully characterized and its structure confirmed by X-ray crystal structure analysis. Variable-temperature NMR studies revealed that the reaction is reversible. Adduct 8a is the predominant species (ca. 98%) in CD2Cl2 solution at low temperature (193 K), whereas at ambient temperature (299 K) it exists in a ca. 7 : 3 equilibrium with unreacted 7 and PhSiH3. Diphenylsilane reacted similarly with the frustrated Lewis pair 7, however, the equilibrium was found to favor the starting materials in the investigated temperature range.

Nickel and copper nitrate complexes with 2,2′-bipyridine (bipy) as a N donor and nitrate and water as oxygen donor ligands of the general formula [M(NO 3 )(C 10 H 8 N 2 )(H 2 O) 3 ](NO 3 ), where M = Ni and Cu, have been obtained from the corresponding metal nitrate salts. These complexes were characterized by X-ray crystallography, FT-IR, and CHN analysis. Both the complexes have been found to be six coordinated. Their thermal decomposition behaviour was investigated by TG, DTA, and ignition delay measurements. TG–DTA examinations of these complexes revealed multistep thermal decomposition. The corresponding metal oxide residues obtained after thermolysis were identified from their X-ray diffraction patterns (XRD). Kinetics of isothermal decomposition of the complexes was established from both the model-fitting as well as isoconversional methods.

We prepared the 2-hydroxy-5-trimethylsilylferrocenecarbaldimine systems 13 enantioselectively by a short synthetic route starting from the chiral ferrocene carbaldehyde acetal 5. The imines 13a–c were used to synthesize the zwitterionic (“ferrocene-salaldiminato”)2ZrCl4 complexes 14a–c. Activation with MAO gave homogeneous Ziegler–Natta catalysts, which showed only a moderate ethylene polymerization activity, similar to the unsubstituted parent “ferrocene-salaldiminato” zirconium systems. Consequently, a synthetic route was devised and carried out to make the corresponding 2-hydroxy-3,5-bis(trimethylsilyl)ferrocenecarbaldimines (21) available. The enantiomerically highly enriched ligands (pS)-21a and -d derived from the aldehyde and aniline or cyclohexylamine, respectively, were used to synthesize the corresponding (“ferrocene-salaldiminato”)2ZrCl4 complexes 22a,d. Both gave highly active homogeneous Ziegler–Natta catalysts upon activation with MAO for the formation of linear low molecular weight polyethy...

A new strategy for the synthesis of tetrahydro-3-benzazepinones 6 by reductive amination of keto acid 3 and subsequent carbonyl diimidazole (CDI) mediated cyclization was developed. Use of enantiomerically pure (R)-1-phenylethylamine led to the formation of diastereomeric lactams (Rα-R)-6d and (Rα-S)-6e in a 80:20 ratio. Diastereoselective alkylation of (Rα-R)-6d, BH3-mediated reduction and exchange of the N-phenylethyl substituent provided enantiomerically pure tetrahydro-3-benzazepines with various substituents in the 1-, 3-, and 4-positions. High σ1 affinity was achieved with a benzyl, cyclohexylmethyl, or 1-phenylethyl moiety at the N-atom. Whereas (R)-configuration of the N-substituent is crucial for high σ1 affinity, the configuration of the 3-benzazepine ring system does not influence the σ1 affinity considerably. Introduction of additional substituents in the 1-position led to almost complete loss of σ1 affinity. Potent σ1 ligands show high selectivity against the σ2 subtype and the NMDA receptor.

A flexible synthesis of bifunctional thiourea derivatives based on the TADDOL framework is described. Hydroxy as well as primary, secondary, and tertiary amino-substituted bifunctional hydrogen­-bond donors were synthesized.

Herein we provide an overview on the unique properties of the sterically demanding IBiox-[(−)-menthyl]∙HOTf ligand (such as flexibility and sterics) and an application of this ligand in Pd-catalyzed asymmetric intra- and intermolecular α-arylation reactions. Furthermore we demonstrate the synthesis of novel NHC–metal complexes and a new bifunctional NHC ligand whilst insight into the mechanistic mode of action of IBiox-[(−)-menthyl]∙HOTf in catalysis is provided.

A series of alkenylboranes were prepared by 1,1-carboboration routes and used as Lewis acid components for the generation of frustrated Lewis pairs (FLPs). The reactions of 1-alkynes with B(C6F5)3 gave the RCH═C(C6F5)B(C6F5)2 systems 4a(R = n-C3H7), 4b (R = n-C4H9), 4c (R = Ph), and 4d (R = t-C4H9), respectively. The alkenylborane/tBu3P FLPs derived from compounds 4a–d reacted rapidly with dihydrogen (2.5 bar) at ambient temperature. The bulky system 4d left the C═C double bond of the alkenylborane unsaturated and gave the dihydrogen cleavage product [tBu3PH][tBuCH═C(C6F5)BH(C6F5)2] (10d). In contrast, the less bulky systems 4a/tBu3P and 4b/tBu3P split dihydrogen under these conditions and had their C═C double bonds cleanly reduced to yield the corresponding 1-pentafluorophenylalkyl hydridoborate salts [tBu3PH][RCH2CH(C6F5)BH(C6F5)2] 9a (R = n-C3H7) and 9b (R = n-C4H9), respectively. The 4c/tBu3P FLP gave a mixture of both product types (9c/10c). 1,1-Carboboration of symmetrical internal alkynes gave the ...

The reactive intramolecular frustrated Lewis pair (FLP) Mes2PCH2CH2B(C6F5)2 reacts rapidly with thionyl chloride to yield the zwitterionic chlorination product [Mes2PCl+]CH2–CH2[BCl(C6F5)2–]. Analogous zwitterionic products were obtained by the reaction of the FLP with chlorine or bromine. Compounds [Mes2PX+]CH2CH2[BX(C6F5)2–] (X = Cl, Br) were characterized by X-ray crystal structure analyses.

Give and take: The introduction of NHC-borane moieties to thiophene-based π skeletons endows a zwitterionic character, which makes the π system electron-donating, while the NHC ring acts as an electron-accepting moiety. The NHC-borane-substituted thiophene underwent a clean photoisomerization with a drastic color change, however, the expanded bithiophene derivatives were inert to this photoreaction, showed low oxidation potentials, and formed a slipped π-stacked array in the crystal.

Based on our recent finding that 2,6-dimethoxyphenyl-substituted NHCs show superior reactivity in the hydroacylation reactions of electron-neutral olefins compared with known NHCs, we now report the syntheses and crystal structures of four highly electron-rich 2,6-dimethoxyphenyl-substituted NHCs and show the increase in efficiency caused by the electron-rich aryl substituent in hydroacylation reactions.

The intramolecular cyclohexylene-bridged P/B frustrated Lewis pair [Mes(2)P-C(6)H(10)-B(C(6)F(5))(2)] 1b reacts rapidly with NO to give the persistent FLP-NO aminoxyl radical 2b formed by P/B addition to the nitrogen atom of NO. This species was fully characterized by X-ray diffraction, EPR and UV/vis spectroscopies, C,H,N elemental analysis, and DFT calculations. The reactive oxygen-centered radical 2b undergoes a H-atom abstraction (HAA) reaction with 1,4-cyclohexadiene to give the diamagnetic FLP-NOH product 3b. FLP-NO 2b reacts with toluene at 70 °C in an HAA/radical capture sequence to give a 1:1 mixture of FLP-NOH 3b and FLP-NO-CH(2)Ph 4b, both characterized by X-ray diffraction. Structurally related FLPs [Mes(2)P-CHR(1)-CHR(2)-B(C(6)F(5))(2)] 1c, 1d, and 1e react analogously with NO to give the respective persistent FLP-NO radicals 2c, 2d, and 2e, respectively, which show similar HAA and O-functionalization reactions. The FLP-NO-CHMePh 6b derived from 1-bromoethylbenzene undergoes NO-C bond cleavage at 120 °C with an activation energy of E(a) = 35(2) kcal/mol. Species 6b induces the controlled nitroxide-mediated radical polymerization (NMP) of styrene at 130 °C to give polystyrene with a polydispersity index of 1.3. The FLP-NO systems represent a new family of aminoxyl radicals that are easily available by N,N-cycloaddition of C(2)-bridged intramolecular P/B frustrated Lewis pairs to nitric oxide.

Treatment of aminoalkynes (ynamines), Me3Si-C≡C-NR2 [NR2 = N(CH2CH2)2NMe, N(CHMe-CH2)2CH2], with dialkylaluminum hydrides, H-AlR′2 (R′ = CH2tBu, iBu, tBu), afforded by hydroalumination the correspo...

2,3-Dihydroboroles are readily formed by treatment of dicyclopropylacetylene with the strongly electrophilic borane B(C6F5)3. The reaction involves a sequence of 1,1-carboboration reactions and pro...

Reactions of N,N-dimethylaniline, N-isopropylaniline, 1,4-C6H4(CH2NHtBu)2, and benzyldimethylamine with the Lewis acid B(C6F5)3 have been studied. In the case of N,N-dimethylaniline the combination of the Lewis acid and base forms an almost completely noninteracting frustrated Lewis pair, while the corresponding reactions of N-isopropylaniline and benzyldimethylamine with B(C6F5)3 afford the adducts (PhNHiPr)B(C6F5)3 (1) and PhCH2NMe2B(C6F5)3 (2), respectively. 1,4-C6H4(CH2NHtBu)2 reacts with 2 equiv of B(C6F5)3 to give rise to an inseparable mixture of the mono- and bis-amine–borane adducts as well as an iminium salt derived from hydride abstraction from a benzylic carbon of the diamine. Subsequent selected reactions of the Lewis acid/base combinations with H2 afforded [PhNMe2H][HB(C6F5)3] (3), [PhCH2NMe2H][HB(C6F5)3] (4), and [1,4-C6H4(CH2NH2tBu)2][HB(C6F5)3]2 (5). Reactions with CO2 gave PhCH2NMe2CO2B(C6F5)3 (6), [PhNiPrH2][PhNiPrCO2B(C6F5)3] (8), [1,4-C6H4(CH2NH2tBu)(CH2NtBuCO2B(C6F5)3] (9), and [C5H6...

Microwave assisted condensation of primary amines with keto acids 1a–c provided directly 3,4-disubstituted 1,3-dihydro-3-benzazepin-2-ones 2. Whereas small amine size, such as NH3 afforded high yields of secondary lactams 2a, 2d, and 2g, primary amines with larger substituents in α-position led to lower yields of 2 or even to regioisomeric indanone derivatives 4. However, subsequent alkylation of 2a, 2d, and 2g with various alkyl halides provided the corresponding N-substituted 3-benzazepin-2-ones 2 in good yields. Hydrogenation of 2 followed by BH3 reduction led to 3-benzazepines 9. 3-Benzyl-2-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine (9c) reveals high σ1 affinity and selectivity over σ2 and NMDA receptors.

1,2-Bis(alkynyl)benzene derivatives react with strongly electrophilic boranes to yield in boryl-functionalized bulky naphthalene derivatives by means of a sequence of 1,1-carboboration reactions. These substrates can be functionalized by transition metal catalyzed cross-coupling reactions.

Covalent bonding interactions between the Lewis acid and Lewis base functionalities have been probed in a series of "frustrated Lewis pairs" (FLPs) (mainly substituted vinylene linked intramolecular phosphane-borane adducts), using solid-state nuclear magnetic resonance techniques and accompanying DFT calculations. Both the (11)B NMR isotropic chemical shifts and nuclear electric quadrupolar coupling parameters turn out to be extremely sensitive experimental probes for such interactions, revealing linear correlations with boron-phosphorus internuclear distances. The principal component V(zz) of the (11)B electric field gradient tensor is tilted slightly away (~20°) from the boron-phosphorus internuclear vector, leading to an improved understanding of the remarkable reactivity of the FLPs. Complementary (31)P{(1)H}-CPMAS experiments reveal significant (31)P-(11)B scalar spin-spin interactions ((1)J ≈ 50 Hz), evidencing covalent bonding interactions between the reaction centers. Finally, (11)B{(31)P} rotational echo double resonance (REDOR) experiments show systematic deviations from calculated curves based on the internuclear distances from X-ray crystallography. These deviations suggest non-zero contributions from anisotropic indirect spin-spin (J anisotropy) interactions, thereby offering additional evidence for covalent bonding.

Dimethyl acetylenedicarboxylate reacts with 2 mol-equiv. B(C6F5)3 by C6F5 transfer to the central acetylenic C≡C bond with formation of a tail-to-tail coupled bis(boron ester enolate) system. The central hexasubstituted butadiene unit of this unique system reacts with dimethyl maleate in a Diels–Alder reaction to give a hydroquinone derivative.

Novel N-aryl-substituted 2-borylbenzaldimines 6 and related systems with extended π-framework 7 based on two borylbenzaldimine units linked by a spacer moiety were synthesized by condensation reactions of 2-(dimesitylboryl)benzaldehyde 3 with various amines 4 and diamines 5. All compounds were completely characterized including X-ray diffraction, especially in view of Lewis acid-base B-O and B-N interactions. The electronic as well as the photophysical properties of bisimines 7 were determined using cyclic voltammetry, UV/vis, and fluorescence spectroscopy and quantum chemistry. These compounds feature large Stokes shifts and reversible reduction waves. Interestingly, UV irradiation experiments unfold enhanced photostability for compounds 7 with an extended π-skeleton. By use of 1,8-diaminonaphthalene we observed the formation of a hitherto unknown BN-heterocyclic compound 9 fused with a perimidine skeleton. Structural and energetic aspects were evaluated by high level quantum chemical methods (DFT and SCS-MP2-calculations).

Bis(N-acylamidines) 1, which contain various rigid or flexible spacer units with different spatial orientations, are potent bis(bidentate) ligands for the coordination of metal ions. Treatment of 1 with NiII or CuII salts gave two 2:2 (3) and four 3:3 (4) metallomacrocycles by self-assembly. The structures of the hitherto unknown products were determined by the geometry of the ligands that incorporate either linear or bent spacers between the two binding sites. Complex 3b is especially interesting due to its two vinyl subunits orientated perpendicular to the plane of the molecule. Complexes 3 and 4 crystallize in planar layers with intercalated solvent molecules (N,N-dimethylformamide, dimethyl sulfoxide). The molecular structures of five coordination compounds in the solid state have been elucidated by X-ray diffraction.

1-Azapenta-1,4-diene-3-ols 4a-m are easily accessible from 1-azapenta-1,4-dien-3-ones 3a-i and organolithium compounds. Treatment of the compounds 4a-m with strong acid (triflic acid) generates 1-azapentadienyl cations in situ upon protonation at the hydroxyl oxygen atom and subsequent water elimination. The intermediate cations undergo facile 4π-electrocyclization under ambient condition to give diversely substituted pyrroles 6a-m in moderate to good yield. The product pyrrole 6k could be characterized by X-ray diffraction. Quantum chemical calculations were performed to elucidate the mechanism of this reaction with respect to starting compounds, transition states, and products. They support the proposed mechanism of a 4π-conrotatory Möbius-type electrocyclic ring-closure reaction.

The development of planar-chiral hydrogen-bond donors based on the [2.2]paracyclophane scaffold is discussed. General strategies to access functionalized enantiopure [2.2]paracyclophane derivatives are briefly reviewed, with the focus on suitable precursors for the synthesis of planar-chiral thiourea derivatives. The synthesis of fourteen hydrogen-bond donors is described. The interaction of four thiourea derivatives with hydrogen-bond acceptors (DMSO and tetramethylammonium chloride) was investigated by 1H NMR spectroscopy and X-ray crystallography. A selection of enantiomerically pure planar-chiral derivatives was applied in asymmetric hydrogen-bond catalysis.

A straightforward synthesis method for mixed phosphane dipyrido-annelated N-heterocyclic carbene (dipiy) palladium(II) complexes is presented. The key step is the oxidative addition of 6-bromodipyridoimidazolium bromides that can be prepared easily from dipyridine in a two step reaction. This new procedure avoids any generation of the free carbene as well as any transmetallation step.

In this contribution, we discuss the reactivity of different phosphanes (XPhos (1a), tBuXPhos (1b), and Mes2PEt (1c)) and tris(pentafluorophenyl)borane (and in one case, EtB(C6F5)2) against small molecules. 1a/B(C6F5)3, 1b/B(C6F5)3, and 1c/B(C6F5)3 split dihydrogen heterolytically to yield the phosphonium borate salts 2a, 2b, and 2c, respectively. Control experiments with D2 gave the respective deuterated phosphonium borates 2a-D2, 2b-D2, and 2c-D2. The FLP systems 1b/B(C6F5)3 and 1c/B(C6F5)3 underwent 1,2-addition reactions with ethene, resulting in the generation of the ethylene-bridged phosphonium borates 3b and 3c. As well, the Lewis pair EtB(C6F5)2 and Mes2PEt reacted with ethene to yield the corresponding 1,2-addition product 3d. At low temperature, the FLP systems 1a/B(C6F5)3 and 1c/B(C6F5)3 coordinated carbon dioxide (4a, 4c). The new compounds 2a, 2b, 3b, 3c, 3d, 4a, and 4c were characterized by X-ray crystal structure analyses.

The frustrated Lewis pair Mes(2)PCH(2)CH(2)B(C(6)F(5))(2) reacts readily with 6-dimethylamino-6-methylfulvene at room temperature to yield the trans-1-[B(C(6)F(5))(2)]-2-[CH(2)CH(2)PMes(2)] disubstituted fulvene derivative 9 that features an internal N-B contact. Thermolysis (80 °C in toluene) results in a complete isomerization to the respective 1-[B(C(6)F(5))(2)]-3-[CH(2)CH(2)PMes(2)] isomer 10. Both compounds were characterized by using X-ray diffraction. A reaction scheme is formulated to rationalize the specific formation of these compounds, involving a retro-hydroboration/hydroboration sequence. The reaction of the 6-dimethylaminofulvene with HB(C(6)F(5))(2) yielded the corresponding parent compound 13 that was also characterized by X-ray diffraction.

The fabrication of thin organic films covalently grafted onto silicon substrates is of significant interest, as they are expected to give access to a broad range of new materials for integration into microelectronic applications. Covalent layer-by-layer (LbL) assembly offers a high degree of freedom when designing such thin films. In this work an approach for the preparation of covalent redox active molecular multilayers on silicon (100) surfaces is presented using a highly branched decaallylferrocene and thiol-ene click chemistry. The multilayers are analyzed by ellipsometry, X-ray photoelectron sprectroscopy, and cyclic voltammetry. The results indicate that the multilayer growth is linear for at least sixteen layers and the density of ferrocenes per layer is in the range of 6 × 10⁻¹¹ mol cm⁻². Moreover, this method for LbL assembly is extended to surfaces which have been locally passivated by microcontact printing. By atomic force microscopy measurements it is possible to show that the covalent LbL deposition proceeds exclusively in the nonpassivated areas.

Oxiranecarbaldimines 1, which are easily accessible in a two-step procedure, were converted into [1,4]dithiepino[2,3-b]furans 5 by the addition of lithiated 1,3-dithiane and subsequent aqueous workup under acidic conditions. In case of bis(imine) 6, the isolation of the intermediate bis(aziridinyl alcohol) 7 was possible and resulted from an aza-Payne rearrangement. Acid treatment of 7 led to the bis(furan) 8. According to quantum chemical calculations, the key step of the acid-catalyzed step is the ring expansion of the 1,3-dithiane with simultaneous ring opening of the aziridine. Several [1,4]dithiepino[2,3-b]furan derivatives 5 and 8 were characterized by X-ray diffraction.

The potassium salt of 1 was transmetalated by reaction with (Cp-allyl)ZrCl3(dme), yielding the complex (NC-nacnac)Cp-allylZrCl2 (2). Addition of 1 molar equiv of B(C6F5)3 gave [(C6F5)3B-NC-nacnac]C...

The preparation of tetraberyllium-μ4-oxo-hexa[η2-(ortho-fluorobenzoate)] [Be4O(o-C6H4FCOO) 6, 2] and tetraberyllium-μ4-oxo-μ2-hydroxo-penta[η2-(ortho-fluorobenzoate)] [Be4(o-C6H4F-COO)5(OH), 3] from silver ortho-fluorobenzoate and BeCl2 in Et2O/thf solution containing varying amounts of water is reported. The single-crystal structures of 2·tetrahydrofuran and 3·Et2O·2 hexane are discussed in comparison with the structure of the known basic beryllium and zinc carboxylates [M4O(RCOO)6, M = Be, Zn]. DFT calculations show that lower symmetry has to be expected for Be-based M4O-framework-type compounds as compared to the corresponding Zn compounds. Compound 2 is a potential precursor for new compounds with MOF substructure motifs

A series of coumarin linked thiourea and urea molecules 1–5 have been designed and synthesized. Thiourea-based monotopic receptors 1–4 showed selective sensing of F− and C6H5COO− by exhibiting significant change in emission as well as change in color. The ditopic receptor 5, on the other hand, fluorometrically distinguished isomeric aromatic dicarboxylates in polar solvent DMSO. Theoretical calculations have been carried out on systems 1–4 and their complexes with C6H5COO− and F− anions in the presence of CH3CN solvent. Calculations have been carried out to determine the geometry and bonding of the complexes in the ground electronic state as well as on the excited electronic states relevant to the absorption spectra and emission spectra in an effort to obtain information on the spectral changes accompanying complexation of the receptors 1–4 with the two anions.