Characterization of a Robust CoII Fluorescent Complex Deposited Intact On HOPG

The new diimine fluorescent ligand ACRI‐1 based on a central acridine yellow core is reported along with its coordination complex [Co₂( ACRI‐1 )₂] ( 1 ), a fluorescent weak ferromagnet. Due to the strong fluorescence of the acridine yellow fluorophore, it is not completely quenched when the ligand is coordinated to Co^II. The magnetic properties of bulk complex 1 and its stability in solution have been studied. Complex 1 has been deposited on highly ordered pyrolitic graphite (HOGP) from solution. The thin films prepared have been characterized by AFM, time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS), grazing incidence X‐ray diffraction (GIXRD), X‐ray absorption spectroscopy (XAS), X‐ray magnetic circular dichroism (XMCD) and theoretical calculations. The data show that the complex is robust and remains intact on the surface of graphite.     

α‐Halogenoacetanilides as Hydrogen‐Bonding Organocatalysts that Activate Carbonyl Bonds: Fluorine versus Chlorine and Bromine

α‐Halogenoacetanilides (X=F, Cl, Br) were examined as H‐bonding organocatalysts designed for the double activation of C?O bonds through NH and CH donor groups. Depending on the halide substituents, the double H‐bond involved a nonconventional C?H???O interaction with either a H?CX_n (n=1–2, X=Cl, Br) or a H?C_Ar bond (X=F), as shown in the solid‐state crystal structures and by molecular modeling. In addition, the catalytic properties of α‐halogenoacetanilides were evaluated in the ring‐opening polymerization of lactide, in the presence of a tertiary amine as cocatalyst. The α‐dichloro‐ and α‐dibromoacetanilides containing electron‐deficient aromatic groups afforded the most attractive double H‐bonding properties towards C?O bonds, with a N?H???O???H?CX₂ interaction.     

Synthesis of Soluble,Alkyne‐Substituted Trideca‐ and Hexadeca‐Starphenes

Two literature‐known TIPS‐ethynyl‐dibromoacenes were prepared and employed to synthesize cyclotrimers by using Yamamoto coupling conditions. Two large, well‐soluble starphenes were isolated in good yields. Crystallographic characterization verifies the triangular shape and shows significant differences in crystal packing.     

Synthesis and Photophysical Properties of Multichromophoric Carbonyl‐Bridged Triarylamines

The synthesis and photophysical properties of two novel multichromophoric compounds is presented. Their molecular design comprises a carbonyl‐bridged triarylamine core and either naphthalimides or 4‐(5‐hexyl‐2,2′‐bithiophene)naphthalimides as second chromophore in the periphery. The lateral chromophores are attached to the core via an amide linkage and a short alkyl spacer. The synthetic approach demonstrates a straightforward functionalization strategy for carbonyl‐bridged triarylamines. Steady‐state and time‐resolved spectroscopic investigations of these compounds, in combination with three reference compounds, provide clear evidence for energy transfer in both multichromophoric compounds. The direction of the energy transfer depends on the lateral chromophore used. Furthermore, the compound bearing the lateral 4‐(bithiophene)naphthaimides is capable of forming fluorescent gels at very low concentrations in the sub‐millimolar regime whilst retaining its energy transfer properties.     

Copper–Boxmi Complexes as Highly Enantioselective Catalysts for Electrophilic Trifluoromethylthiolations

The enantioselective trifluoromethylthiolation of β‐ketoesters using chiral copper–boxmi complexes as catalysts is reported. A number of α‐SCF₃‐substituted β‐ketoesters have been obtained with up to >99 % enantiomeric excess (ee), and the trifluoromethylthiolated products were then transformed diastereoselectively to α‐SCF₃‐β‐hydroxyesters with two adjacent quaternary stereocenters.     

Synthesis of Rhenabenzenes from the Reactions of Rhenacyclobutadienes with Ethoxyethyne

Treatment of Na[Re(CO)₅] with RC?CCO₂Et (R=phenyl, naphthalen‐1‐yl, phenanthren‐9‐yl and pyren‐1‐yl) followed by reaction with acetyl chloride and ethanol afforded the rhenacyclobutadienes Re{‐C(R)?C(CO₂Et)C(OEt)?}(CO)₄. Reactions of these rhenacyclobutadienes with HC?COEt produced rhenabenzenes Re{‐C(R)?C(CO₂Et)C(OEt)?CHC(OEt)?}(CO)₄. Except for R=Ph, new rhenacyclobutadienes with pendant alkenyl substituents Re{‐C(R)?C(C(OEt)?CH(CO₂Et))C(OEt)?}(CO)₄ were also isolated from these reactions. The NMR spectroscopic and X‐ray structural data, as well as the aromatic stabilization energy (ASE) values suggest that the rhenabenzenes are aromatic, with extensive delocalized π character.     

Pyranoside‐into‐Furanoside Rearrangement: New Reaction in Carbohydrate Chemistry and Its Application in Oligosaccharide Synthesis

Great interest in natural furanoside‐containing compounds has challenged the development of preparative methods for their synthesis. Herein a novel reaction in carbohydrate chemistry, namely a pyranoside‐into‐furanoside (PIF) rearrangement permitting the transformation of selectively O‐substituted pyranosides into the corresponding furanosides is reported. The discovered process includes acid‐promoted sulfation accompanied by rearrangement of the pyranoside ring into a furanoside ring followed by solvolytic O‐desulfation. This process, which has no analogy in organic chemistry, was shown to be a very useful tool for the synthesis of furanoside‐containing complex oligosaccharides, which was demonstrated by synthesizing disaccharide derivatives α‐D ‐Galp‐(1→3)‐β‐D ‐ Galf ‐OPr, 3‐O‐s ‐lactyl‐β‐D ‐ Galf ‐(1→3)‐β‐D ‐Glcp‐OPr, and α‐L ‐ Fucf ‐(1→4)‐β‐D ‐GlcpA‐OPr related to polysaccharides from the bacteria Klebsiella pneumoniae and Enterococcus faecalis and the brown seaweed Chordaria flagelliformis.     

Supramolecular Water Oxidation with Ru–bda‐Based Catalysts

Extremely slow and extremely fast new water oxidation catalysts based on the Ru–bda (bda=2,2′‐bipyridine‐6,6′‐dicarboxylate) systems are reported with turnover frequencies in the range of 1 and 900 cycles s^?1, respectively. Detailed analyses of the main factors involved in the water oxidation reaction have been carried out and are based on a combination of reactivity tests, electrochemical experiments, and DFT calculations. These analyses give a convergent interpretation that generates a solid understanding of the main factors involved in the water oxidation reaction, which in turn allows the design of catalysts with very low energy barriers in all the steps involved in the water oxidation catalytic cycle. We show that for this type of system π‐stacking interactions are the key factors that influence reactivity and by adequately controlling them we can generate exceptionally fast water oxidation catalysts.     

Freezing Capture of Polymorphic Aggregates of Bolaamphiphilic L‐Valine‐Based Molecular Hydrogelators

Nanostructured xerogels have been prepared by the freeze‐drying of hydrogels and aggregates formed by bolaamphiphilic L ‐valine derivatives after aging under different environmental conditions. A wide variety of shapes and sizes has been achieved by a simple methodology. These nanostructures have been studied by SEM and WAXD and a dramatic influence of structural flexibility on the kinetics of aggregation has been observed. Such flexibility and a modulation of the hydrophobic effect have shown a profound influence in the packing of these compounds and revealed a high degree of polymorphism.     

Predicting New Ugi–Smiles Couplings: A Combined Experimental and Theoretical Study

Following our previous mechanistic studies of multicomponent Ugi‐type reactions, theoretical calculations have been performed to predict the efficiency of new substrates in Ugi–Smiles couplings. First, as predicted, 2,4,6‐trichlorophenol experimentally gave the corresponding aryl‐imidate. Theoretical predictions of nitrosophenols as good acidic partners were then successfully confirmed by experiments. In the latter case, the reaction offers a new access to benzimidazoles.