Conjugated poly-ynes and poly(metalla-ynes) constitute an important class of new materials with potential application in various domains of science. The key factors responsible for the diverse usage of these materials is their intriguing and tunable chemical and photophysical properties. This review highlights fascinating advances made in the field of conjugated organic poly-ynes and poly(metalla-ynes) incorporating group 4–11 metals. This includes several important aspects of conjugated poly-ynes viz. synthetic protocols, bonding, electronic structure, nature of luminescence, structure–property relationships, diverse applications, and concluding remarks. Furthermore, we delineated the future directions and challenges in this particular area of research.

Rise of Conjugated Poly-ynes and Poly(Metalla-ynes): From Design Through Synthesis to Structure–Property Relationships and Applications

One-Pot Synthesis of 2,3,5-Trisubstituted Thiophenes through Three-Component Assembly of Arylacetaldehydes, Elemental Sulfur, and 1,3-Dicarbonyls

Synthesis of tetrasubstituted thiophenes via a [3+2] cascade cyclization reaction of pyridinium 1,4-zwitterionic thiolates and activated allenes

The one-dimensional carbon allotrope carbyne, a linear chain of sp-hybridized carbon atoms, is predicted to exist in a polyynic and a cumulenic structure. While molecular forms of carbyne have been...

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Three Distinct Torsion Profiles of Electronic Transmission through Linear Carbon Wires

Reactivity of Polyynes: Complex Molecules from Simple Carbon Rods

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

Serendipitous Formation of Various Selenium Heterocycles Hidden in the Classical Synthesis of Selenophene.

The vibrational properties of a series of push-pull polyynes have been studied by infrared and Raman spectroscopy. The simultaneous activation of a strong infrared and Raman mode, i.e. the collective vibration of CC bonds of the sp carbon chain, highlights the effectiveness of a polyyne bridge in promoting charge transfer between the electron donor (D) and acceptor (A) ends, thus suggesting that ad-hoc functionalized polyynes are worth being explored as building blocks of organic materials with attractive first-order optical nonlinearity. The optical, electronic, and vibrational properties of these molecules have been investigated with the support of density functional theory calculations, as well as the electronic and vibrational first hyperpolarizabilities (β). The mid-low region of the IR spectra (800-1600 cm−1) has been analyzed in detail, searching for marker bands of the specific terminations of the different sp carbon chains thus achieving a complete vibrational characterization of sp hybridized push-pull systems.

Vibrational and nonlinear optical properties of amine-capped push-pull polyynes by infrared and Raman spectroscopy

Polyynes are compounds with two or more conjugated carbon–carbon triple bonds. Such molecules are usually regarded as models of carbyne—a hypothetical one-dimensional allotropic form of carbon. 1-Halopolyynes are rare representatives of such species, but few interesting crystal-to-crystal reactions have been recently reported for them. Herein, we present 11 new X-ray structures of 1-halopolyynes, nearly doubling the number of such compounds characterized with the use of single-crystal X-ray diffraction. The influence of an end-group on packing motifs in crystal structures of the 1-halopolyynes were thoroughly examined. Especially the strength of halogen bond as a function of polyyne chain length was analyzed with the support of theoretical calculations. Moreover, the compound CNC8I is the longest 1-halopolyyne characterized to date with the use of rentgenostructural analysis. In addition to that, the compounds NO2C6Br and MeC(O)C6Br are the first 1-bromohexatriynes characterized by means of X-ray single-c...

Crystal Engineering of 1-Halopolyynes by End-Group Manipulation

The vibrational properties of a series of push-pull polyynes have been studied by infrared and Raman spectroscopy. The simultaneous activation of a strong infrared and Raman mode, i.e. the collective vibration of CC bonds of the sp carbon chain, suggests the occurrence of attractive nonlinear optical properties. The optical, electronic, and vibrational properties of these molecules have been investigated with the support of density functional theory calculations, as well as the electronic and vibrational first hyperpolarizabilities (\b{eta}). The mid-low region of the IR spectra (800-1600 cm-1) has been analyzed in detail, searching for marker bands of the specific terminations of the different sp carbon chains. We achieved a complete vibrational characterization of sp hybridized push-pull systems that represent appealing candidates for NLO applications in optics and optoelectronic devices.

Patrycja Męcik

Papers

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

Serendipitous Formation of Various Selenium Heterocycles Hidden in the Classical Synthesis of Selenophene.

Vibrational and nonlinear optical properties of amine-capped push-pull polyynes by infrared and Raman spectroscopy

Crystal Engineering of 1-Halopolyynes by End-Group Manipulation

Vibrational and nonlinear optical properties of amine-capped push-pull polyynes by infrared and Raman spectroscopy