Polyynes and Acetylenes
The synthesis of long 1-halopolyynes nad their use as precursors of organometallic polyynes
The synthesis of a unique series of long, asymmetric 1-iodopolyynes (1-CnI and 2-CnI) with the sp-hybridized carbon chain up to a decapentayne was reported.
Figure 1. The synthesis of long-chain 1-iodopolyynes.
These compounds were then used as substrates in reactions with Pd(PPh3)4 leading to another series of palladium end-capped polyynes, which were unstable in solution. Organometallic octatetraynes 1-C8[Pd]I, 2-C8[Pd]I, and decapentayne 1-C10[Pd]I are palladium end-capped polyyne compounds with the longest carbon chains reported so far. The synthetic approach for palladium species is envisioned as a general route for the synthesis of labile organometallic polyynes.
Figure 2. The synthesis of long-chain palladium end-capped polyynes.
For more information see: Organometallics 2015, 34, 673-682; Chem. Eur. J. 2015, 21, 17769-17778.
Mechanochemical synthesis of new polyynes
The synthesis of long chain hexatriynyl- and octatetraynyl-substituted pyrroles in one step from 1-halopolyyne precursors was reported. The products were obtained via a mechanochemical approach by simple grinding of 1-haloalkynes with N-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.
Figure 3. The mechanochemical synthesis of polyynes substituted pyrroles.
For more information see: J. Org. Chem. 2016, 81, 9188–9198; RSC Adv. 2015, 5, 73241-73248.
Chlorination of protected and terminal alkynes and butadiynes
A highly efficient one-pot procedure for the preparation of 1-chloroalkynes and 1-chlorobutadiynes from terminal and trialkylsilyl-protected precursors is reported. This convenient reaction, proceeding under mild conditions, utilizes N-chlorosuccinimide as the chlorinating agent and tolerates a range of functional groups.
Figure 4. Chlorination of TMS-protected alkynes and butadiynes.
For more information see: Chem. Eur. J. 2014, 20, 2746-2749.
NLO properties of new polyynes
We investigated three newly synthesized aryl end-capped octatetraynes, exhibiting strong nonlinear absorption and nonlinear refraction properties, which can be attributed to the presence of aryl end-groups with electron-withdrawing functional groups suitable for further extending the conjugation. Nonlinear optical measurements were performed using a f-scan (modified Z-scan) technique with a femtosecond laser system at various wavelengths in the visible and near-infrared range (540–1600 nm), revealing strong negative third-order nonlinear refraction (3NR) and two-photon absorption (2PA) below 600 nm and a noticeable three-photon absorption (3PA) at longer wavelengths.
Figure 5. NLO properties of octatetraynes.
For more information see: Phys. Chem. Chem. Phys., 2015,17, 13680-13688.