Luminescent Di‐ and Trinuclear Boron Complexes Based on Aromatic Iminopyrrolyl Spacer Ligands: Synthesis,Characterization, and Application in OLEDs

New bis‐ and tris(iminopyrrole)‐functionalized linear (1,2‐(HNC₄H₃‐C(H)?N)₂‐C₆H₄ ( 2 ), 1,3‐(HNC₄H₃‐C(H)?N)₂‐C₆H₄ ( 3 ), 1,4‐(HNC₄H₃‐C(H)?N)₂‐C₆H₄ ( 4 ), 4,4′‐(HNC₄H₃‐C(H)?N)₂‐(C₆H₄‐C₆H₄) ( 5 ), 1,5‐(HNC₄H₃C‐(H)?N)₂‐C₁₀H₆ ( 6 ), 2,6‐(HNC₄H₃C‐(H)?N)₂‐C₁₀H₆ ( 7 ), 2,6‐(HNC₄H₃C‐(H)?N)₂‐C₁₄H₈ ( 8 )) and star‐shaped (1,3,5‐(HNC₄H₃‐C(H)?N‐1,4‐C₆H₄)₃‐C₆H₃ ( 9 )) π‐conjugated molecules were synthesized by the condensation reactions of 2‐formylpyrrole ( 1 ) with several aromatic di‐ and triamines. The corresponding linear diboron chelate complexes (Ph₂B[1,3‐bis(iminopyrrolyl)‐phenyl]BPh₂ ( 10 ), Ph₂B[1,4‐bis(iminopyrrolyl)‐phenyl]BPh₂ ( 11 ), Ph₂B[4,4′‐bis(iminopyrrolyl)‐biphenyl]BPh₂ ( 12 ), Ph₂B[1,5‐bis(iminopyrrolyl)‐naphthyl]BPh₂ ( 13 ), Ph₂B[2,6‐bis(iminopyrrolyl)‐naphthyl]BPh₂ ( 14 ), Ph₂B[2,6‐bis(iminopyrrolyl)‐anthracenyl]BPh₂ ( 15 )) and the star‐shaped triboron complex ([4′,4′′,4′′′‐tris(iminopyrrolyl)‐1,3,5‐triphenylbenzene](BPh₂)₃ ( 16 )) were obtained in moderate to good yields, by the treatment of 3 – 9 with B(C₆H₅)₃. The ligand precursors are non‐emissive, whereas most of their boron complexes are highly fluorescent; their emission color depends on the π‐conjugation length. The photophysical properties of the luminescent polyboron compounds were measured, showing good solution fluorescence quantum yields ranging from 0.15 to 0.69. DFT and time‐dependent DFT calculations confirmed that molecules 10 and 16 are blue emitters, because only one of the iminopyrrolyl groups becomes planar in the singlet excited state, whereas the second (and third) keeps the same geometry. Compound 13 , in which planarity is not achieved in any of the groups, is poorly emissive. In the other examples ( 11 , 12 , 14 , and 15 ), the LUMO is stabilized, narrowing the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO–LUMO), and the two iminopyrrolyl groups become planar, extending the size of the π‐system, to afford green to yellow emissions. Organic light‐emitting diodes (OLEDs) were fabricated by using the new polyboron complexes and their luminance was found to be in the order of 2400 cd m^?2, for single layer devices, increasing to 4400 cd m^?2 when a hole‐transporting layer is used.     

Azido‐Substituted BODIPY Dyes for the Production of Fluorescent Carbon Nanotubes

A series of azido‐dyes were synthesized through Knoevenagel reactions of an azido‐BODIPY with aromatic aldehydes. The nature of the substituents allowed the fine tuning of their spectroscopic properties. The dyes were used to decorate oxidized multiwalled carbon nanotubes (ox‐MWCNTs), bearing terminal triple bond groups, by CuAAC reactions, affording fluorescent materials. This decoration allowed the efficient determination of the internalization of the ox‐MWCNT derivatives by different model cancer cells, such as MCF7.     

A crystalline sponge based on dispersive forces suitable for X-ray structure determination of included molecular guests

A crystalline porous material showing one-dimensional (1-D) rectangular micropores (12 × 9 Ų) has been assembled from a semirigid macrocyclic tetraimine and EtOAc as the templating agent. The 1-D nature of the material is intrinsic to the conformationally rigid structure of a macrocyclic sub-unit bearing four cyclohexylidene residues. The multiple dispersive forces established among the aliphatic residues glutted the 1-D channels and provided thermal stability to the material at temperatures below 160 °C. Upon removal of the template, the structure of the empty solid exhibited permanent microporosity (S _BET = 342 m² g^–1). Being a true molecular sponge, the channel framework of this material allowed the inclusion of a variety of molecular sample guests without compromising its crystalline nature. Remarkably, this crystalline material enabled the structure determination by X-ray diffraction of the included molecules. Theoretical studies demonstrated the vital role played by the dispersive forces in the overall stabilization of the crystal packing.     

The design and synthesis of novel IBiox N-heterocyclic carbene ligands derived from substituted amino-indanols

A synthetic route towards a number of novel IBiox N-heterocyclic carbene (NHC) ligands has been developed. The resulting ligands have restricted flexibility and high steric demand. Preliminary studies have shown these ligands to give high levels of asymmetric induction in the copper-free allylic alkylation of cinnamyl bromide.     

Top-down patterning of zeolitic imidazolate framework composite thin films by deep X-ray lithography

For the first time a top-down process was used to control the spatial location of Metal-Organic Frameworks on a surface. Deep X-ray lithography was utilised to micropattern a Zeolitic Imidazolate Framework layer on a sol-gel surface, with exposure hardening the sol-gel by inducing crosslinking while leaving the frameworks intact.     

Preparation and characterization of aryl or heteroaryl(3-indolyl)methylium o-benzenedisulfonimides

An initial study has been accomplished into the synthetic feasibility of the preparation of diarylcarbenium salt via the direct coupling of aryl (or heteroaryl) aldehydes and arenes (or heteroaryl analogues) in the presence of a strong organic Br?nsted acid. A number of stabilized aryl or heteroaryl(3-indolyl)carbenium ions, never previously prepared in the solid state, have been isolated in excellent yields as highly stable o-benzenedisulfonimide salts and have been fully characterized. Their purity has been proven by spectroscopic methods and chemical reduction with NaBH(4). An X-ray crystal structure analysis has been performed on one of the products: an azafulvenium species was shown to be the exclusive structure in the solid state.     

Shapes and noncovalent interactions of oligomers: the rotational spectrum of the difluoromethane trimer

The trimer of difluoromethane, (CH2F2)3, has been characterized by supersonic jet Fourier transform microwave spectroscopy. The rotational spectrum displays all types (mu(a), mu(b), and mu(c)) of transitions, showing that the adduct does not possess any element of molecular symmetry. The investigation of the three 13C species in natural abundance indicates that the three carbon atoms form a triangle where the C-C distances are 3.648(2), 3.825(8), and 3.942(6) A, respectively. The three subunits are held together by nine CH...F weak hydrogen bonds.     

Photodynamics of a PV Trimer in High‐Viscosity Solvents and in PMMA Films: A New Insight into Energy Transfer versus Conformational Relaxation in Conjugated Polymers

Non‐Stokes–Einstein relaxation : The rate constant of conformational relaxation of a phenylenevinylene trimer (see picture) in different solvents is proportional to η^?α, with α values decreasing from close to unity (low viscosity) to zero at sufficiently high solvent viscosity. This behaviour is attributed to the flexible methylbutyl side chains of the trimer, which partially screen the solvent friction.

     

Evaluation of propolis polyphenols absorption in humans by liquid chromatography/tandem mass spectrometry

Propolis has various biological activities such as antibacterial, antiviral, antioxidant, immunostimulating and antiinflammatory, which are generally ascribed to the polyphenolic fraction. The aim of this study was to evaluate the absorption of the main polyphenols [caffeic acid (CA), pinobanksin-5methyl ether (P-5ME), pinobanksin (Pb), chrysin (C), pinocembrin (P), galangin (G), pinobanksin-3-acetate, pinobanksin esters and caffeic acid phenylethyl ester (CAPE)] from a dewaxed and standardized extract of propolis (EPID). Fifteen healthy volunteers consumed 5 mL EPID in water, corresponding to 125 mg of flavonoids. Blood samples were collected before, each hour for 8 h and 24 h after EPID intake. After deconjugation by beta-glucuronidase/sulfatase the plasma samples were analyzed by a selective liquid chromatography/tandem mass spectrometry (LC/MS/MS) method using morin as internal standard (I.S.). A kinetic profile characterized by two t(max), respectively at 1 h and about 5 h post-ingestion, was observed in all the subjects. The two peaks may be due to enterohepatic cycling. Among the various polyphenols ingested, only P-5ME, Pb, C, P and G were detected in plasma and C(max)t(1h) were 65.7 +/- 13.3, 46.5 +/- 12.7, 79.5 +/- 18.6, 168.1 +/- 16.3 and 113.7 +/- 16.8 ng/mL, respectively. These levels decreased significantly after 8 h and were no longer detectable 24 h after EPID intake. The recovery of the extraction for CA, Pb, C, P, G and I.S. from spiked plasma was 95.2 +/- 3.1, 93.1 +/- 3.6, 91 +/- 2.5, 96.4 +/- 4.2, 93.4 +/- 2.4 and 85.5 +/- 2.4%, respectively. The results of this study evidence that flavonoids from EPID are absorbed, metabolized and Pb-5ME and G seem to have apparent absorption, measured as (AUC/dose), higher than C, P and Pb.