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.
Polyynes
are compounds with two or more conjugated carbon–carbon
triple bonds. Such molecules are usually regarded as models of carbynea
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 CNC
8
I is the longest 1-halopolyyne characterized to date with the use
of rentgenostructural analysis. In addition to that, the compounds NO
2
C
6
Br and MeC(O)C
6
Br are the first 1-bromohexatriynes characterized
by means of X-ray single-crystal diffraction.
Synthesis of complex
di(selenophen-3-yl)diselenides and 3-methylene-3
H
-1,2-diselenoles directly from 1-bromobutadiynes is described.
The transformation is performed under conditions used before for the
synthesis of simple selenophenes from butadiynes. The reaction is
operationally straightforward, and complex products were obtained
in high yields. Structures of the final products were unambiguously
confirmed by the means of
77
Se NMR and single-crystal X-ray
diffraction.
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