Palladium End-Capped Polyynes via Oxidative Addition of 1‑Haloalkynes to Pd(PPh₃)₄

Reported here is the use of 1-haloacetylenes and 1-halopolyynes as synthons for the preparation of new palladium­(II) end-capped polyynes. The 1-haloalkynes were obtained in a series of transformations from <i>para</i>-substituted bromoarenes that included Sonogashira coupling followed by halogenation and chain elongation via Cadiot–Chodkiewicz protocol. The key step for the synthesis of metal complexes was oxidative addition of 1-haloalkynes to Pd­(PPh₃)₄, which allowed obtaining a series of metal compounds <b>1</b>–<b>5</b>-C_<i>n</i>X with carbon chains up to hexatriyne in 75–100% yield. All the compounds were characterized by NMR and HRMS or elemental analysis. The ¹³C spectra of the 1-haloalkynes showed interesting, although expected, shifts of the carbon chain atoms close to the halogen termini. X-ray crystal structures were obtained for three polyynestwo butadiynes (<b>2</b>-C₄[Pd]Br and <b>3</b>-C₄[Pd]­Br) and one hexatriyne (<b>1</b>-C₆[Pd]­Br)and the latter is the first reported X-ray crystal structure of palladium end-capped hexatriyne

Porous Silsesquioxane–Imine Frameworks as Highly Efficient Adsorbents for Cooperative Iodine Capture

The efficient capture and storage of radioactive iodine (¹²⁹I or ¹³¹I), which can be formed during nuclear energy generation or nuclear waste storage, is of paramount importance. Herein, we present highly efficient aerogels for reversible iodine capture, namely, porous silsesquioxane–imine frameworks (PSIFs), constructed by condensation of octa­(3-aminopropyl)­silsesquioxane cage compound and selected multitopic aldehydes. The resulting PSIFs are permanently porous (Brunauer–Emmet–Teller surface areas up to 574 m²/g), thermally stable, and present a combination of micro-, meso-, and macropores in their structures. The presence of a large number of imine functional groups in combination with silsesquioxane cores results in extremely high I₂ affinity with uptake capacities up to 485 wt %, which is the highest reported to date. Porous properties can be controlled by the strut length and rigidity of linkers. In addition, <b>PSIF-1a</b> could be recycled at least four times while maintaining 94% I₂ uptake capacity. Kinetic studies of I₂ desorption show two strong binding sites with apparent activation energies of 77.0 and 89.0 kJ/mol. These energies are considerably higher than the enthalpy of sublimation of bulk I₂

Polyynes as Precursors of Photoluminescent Solvent Polarity Probes

A simple and convenient synthesis of substituted thiophenes from pyrrole end-capped polyynes is being reported. The method allows one to obtain a variety of different fluorescent oligo­(hetero)­aryles from polyyne precursors. The resulting thiophenes exhibit strong emission solvatochromism in a wide scope of different solvents which makes them promising candidates for fluorescent solvent polarity probes

Palladium End-Capped Polyynes via Oxidative Addition of 1‑Haloalkynes to Pd(PPh₃)₄

Reported here is the use of 1-haloacetylenes and 1-halopolyynes as synthons for the preparation of new palladium­(II) end-capped polyynes. The 1-haloalkynes were obtained in a series of transformations from <i>para</i>-substituted bromoarenes that included Sonogashira coupling followed by halogenation and chain elongation via Cadiot–Chodkiewicz protocol. The key step for the synthesis of metal complexes was oxidative addition of 1-haloalkynes to Pd­(PPh₃)₄, which allowed obtaining a series of metal compounds <b>1</b>–<b>5</b>-C_<i>n</i>X with carbon chains up to hexatriyne in 75–100% yield. All the compounds were characterized by NMR and HRMS or elemental analysis. The ¹³C spectra of the 1-haloalkynes showed interesting, although expected, shifts of the carbon chain atoms close to the halogen termini. X-ray crystal structures were obtained for three polyynestwo butadiynes (<b>2</b>-C₄[Pd]Br and <b>3</b>-C₄[Pd]­Br) and one hexatriyne (<b>1</b>-C₆[Pd]­Br)and the latter is the first reported X-ray crystal structure of palladium end-capped hexatriyne

Use of Stable Amine-Capped Polyynes in the Regioselective Synthesis of Push–Pull Thiophenes

The reactions of a series of 1-halopolyynes with secondary amines led to novel amine end-capped polyynes exhibiting surprisingly high stability toward moisture. The new compounds were characterized by NMR spectroscopy, ESI-MS spectrometry, and X-ray single-crystal diffractometry. The use of amine end-capped polyynes as precursors to substituted push–pull thiophenes was next presented. The results show the firstto the best of our knowledgetransformation of ynamine to thiophene and the first regioselective transformation of a longer polyynes to butadiyne-substituted thiophene. Photophysical studies of the resulting compounds show that some of the substituted thiophenes have high quantum yield photoluminescence upon UV light irradiation

Use of Stable Amine-Capped Polyynes in the Regioselective Synthesis of Push–Pull Thiophenes

The reactions of a series of 1-halopolyynes with secondary amines led to novel amine end-capped polyynes exhibiting surprisingly high stability toward moisture. The new compounds were characterized by NMR spectroscopy, ESI-MS spectrometry, and X-ray single-crystal diffractometry. The use of amine end-capped polyynes as precursors to substituted push–pull thiophenes was next presented. The results show the firstto the best of our knowledgetransformation of ynamine to thiophene and the first regioselective transformation of a longer polyynes to butadiyne-substituted thiophene. Photophysical studies of the resulting compounds show that some of the substituted thiophenes have high quantum yield photoluminescence upon UV light irradiation

Transition-Metal Free Mechanochemical Approach to Polyyne Substituted Pyrroles

In this contribution, the synthesis of long chain hexatriynyl- and octatetraynyl-substituted pyrroles in one step from 1-halopolyyne precursors is reported. The products were obtained via a mechanochemical approach by simple grinding of 1-haloalkynes with <i>N</i>-substituted pyrroles and potassium carbonate which played a role of heterogeneous catalyst and this solvent- and transition metal-free approach is unprecedent in the synthesis of new, organic, long chain polyynes. Additionally, an extensive X-ray single crystal study of pyrrole end-capped polyynes is presented. Such compounds are possible substrates for different oligoheterocycles and have a significant application potential such as for instance molecular wires

Transition-Metal Free Mechanochemical Approach to Polyyne Substituted Pyrroles

In this contribution, the synthesis of long chain hexatriynyl- and octatetraynyl-substituted pyrroles in one step from 1-halopolyyne precursors is reported. The products were obtained via a mechanochemical approach by simple grinding of 1-haloalkynes with <i>N</i>-substituted pyrroles and potassium carbonate which played a role of heterogeneous catalyst and this solvent- and transition metal-free approach is unprecedent in the synthesis of new, organic, long chain polyynes. Additionally, an extensive X-ray single crystal study of pyrrole end-capped polyynes is presented. Such compounds are possible substrates for different oligoheterocycles and have a significant application potential such as for instance molecular wires