Comprehensive Look at the Photochemistry of Tolane

Diphenylacetylene (tolane) exhibits a rich photochemistry that depends on the relative orientation of the phenyl rings and the external conditions. Here, state-of-the-art quantum chemical methods based on the algebraic diagrammatic construction scheme for a polarization propagator of second order are employed to investigate the luminescence properties of tolane and its derivatives. It is explained why different derivatives of tolane exhibit different absorption but practically identical fluorescence spectra, why the fluorescence quantum yield and the population of a “dark” state are temperature-dependent, and why initially twisted tolanophanes phosphoresce in glassy media at 77 K while planar ones do not

2‑Bromotetraazapentacene and Its Functionalization by Pd(0)-Chemistry

We have synthesized a brominated <i>N,N</i>′-dihydrotetra­azapentacene using a condensation route. Sonogashira reactions replace the Br-substituent by an alkynyl group, placed on the azaacene core. Sonogashira coupling of brominated dihydro tetraazapentacene <b>1H</b>_<b>2</b> with alkynes and subsequent oxidation afford several functionalized TIPS-tetraazapentacene derivatives with energetically stabilized FMOs. These TIPS-TAPs are either crystalline or amorphous, depending upon their substitution pattern

Halogen Bonding in Diaza-Triisopropylsilyl-Tetracene Crystals?

Four halogenated triisopropylsilylethynyl (TIPS)-tetracene derivatives were synthesized, their single crystal structures and optical and electronic properties were examined. Both, diiodo-TIPS-diazatetracene and dibromo-TIPS-diazatetracene showed herringbone arrangements, in which the halogen atoms are directed toward the nitrogen atoms of a neighboring molecule with slightly lower distances than the van der Waals radii between halogen and nitrogen atoms. Computations of the electrostatic potentials showed the availability and the strength of σ holes, so that we assume a weak halogen–nitrogen bonding. Tribromo-TIPS-diazatetracene delivered a 2D-brick wall structure with no sign of a halogen bonding. Dibromo-TIPS-tetracene crystallized neither in a herringbone nor in a brick wall motif. These results show that for halogenated azaacenes at least weak halogen–nitrogen interactions exist

Aggregation, Acidochromicity, and Metallochromicity of a Pyridine-Based Poly(aryleneethynylene)

A pyridine-containing poly­(aryleneethynylene) (PAE) is investigated, showing surprisingly versatile changes of its photophysical properties in response to external stimuli. Because of agglomeration-induced planarization of the backbone, this PAE exhibits a significant red-shift in absorption and emission, when moving from good to poor solvents. The basic lone pair on the pyridine unit makes this PAE pH-sensitive and imparts metallochromic properties, useful for the potential detection of a wide range of metal cations, resulting in color responses that range from quenching to red-shifted emission

Amine Detection with Distyrylbenzenedialdehyde-Based Knoevenagel Adducts

Eight acceptor-substituted distyrylbenzene (DSB) derivatives were obtained by postfunctionalization of dialdehyde precursor <b>1</b> using Knoevenagel condensation. Solubility in a water/THF 9:1 mixture was achieved through the addition of branched oligoethylene glycol side chains. The acceptor compounds discriminate primary and secondary amines in aqueous solution. The fluorescence responses were analyzed by the multivariate analysis of variance (MANOVA) protocol, a statistical tool. In contrast to <b>1</b>, the adducts show reactivity toward secondary and aromatic amines. Nitroolefin <b>2f</b> is the most active dosimeter molecule. Reaction with amines is completed after less than 3 min, and the limit of detection (LOD) is improved by a factor of 10. Propylenediamine can be detected at 75 μM. This is a 10-fold improvement for the detection limit when compared to the detection limit of the starting dialdehyde

[2.2.2]Paracyclophane-TrienesAttractive Monomers for ROMP

Three derivatives of 4,7-substituted [2.2.2]­paracyclophane-trienes were synthesized and used in ring-opening metathesis polymerization (ROMP), resulting in well-soluble poly­(<i>para</i>-phenylenevinylene)­s (PPV). The paracyclophane-trienes were prepared using an iterative buildup of a phenylene–ethynylene backbone, followed by a cis selective Grignard reduction and an intramolecular McMurry reaction. The monomers were applied in ROMP to result in well-soluble PPV derivatives with an unusual substituent pattern. The PPVs were spin-coated into amorphous, highly fluorescent films. To the best of our knowledge, we are the first to synthesize 4,7-substituted [2.2.2]­paracyclophane-trienes and use them as ROMP monomers

Tetraazaacenes Containing Four-Membered Rings in Different Oxidation States. Are They Aromatic? A Computational Study

A symmetrical tetraazaacene incorporating a central cyclobutadiene ring was calculated in different oxidation (hydrogenation) states, displaying different tautomers and conformers. Geometries, thermodynamics, and electronic properties were computed, and the aromaticity of all these species was calculated on a per ring basis by NICS-scans and NICS-X-scans. The results unveil unexpected and fascinating insights into the complex aromaticity of those compounds, including a formally aromatic (!) cyclobutadiene ring

Interpenetrated Frameworks with Anisotropic Pore Structures from a Tetrahedral Pyridine Ligand

Herein we investigate metal–organic frameworks (MOFs) employing the tetrahedral building block tetrakis­(4-(pyridin-4-ylethynyl)­phenyl)­silane (<b>1</b>) as a structure-generating feature. Combining <b>1</b> with a series of different metal ions gives wildly different MOF topologies, porosities, and properties. The frameworks discussed deviate from the common construction principles of MOFs as both the ligand and the metal center impose their coordination geometry on the overall network. The resulting networks show attractive and unusual void distributions, yet with properly controlled transition metal ion geometries, these MOFs show a rational structural grammar with respect to their structures

Development of Thermally Activated Delayed Fluorescence Materials with Shortened Emissive Lifetimes

We have prepared a thermally activated delayed fluorescence (TADF) capable molecular system carrying halogen substituents at the carbazole units. The attachment of the halogen atoms considerably decreases the half-life of the delayed fluorescence. The effect is significant. The heavier the halogen, the greater the effect. Our materials have the shortest reported emissive lifetimes for TADF achieved to date. Intersystem crossing (ISC) is improved through the heavy atom effect, yet high quantum yields are achieved both in solution as well as in thin doped films. The simple and efficient synthesis of our targets uses inexpensive and easily obtained starting materials

Synthesis of Substituted Trinaphthylenes

A short synthesis of six trinaphthylenes is reported. The cyclotrinaphthylenes carry six alkoxy groups, and derivatives featuring OHex, OBu, OiPr, OPr, OEt, and OMe substituents can be obtained by an ordinary Ni­(COD)₂-promoted, Yamamoto-type coupling reaction. Cyclotrimerization yields range from 38% to 65%. Dependent upon their structure, the cyclotrinaphthylenes assume different packing patterns, according to single-crystal X-ray structure determination. The crystal structures of such trinaphthylenes were hitherto undescribed