Synthesis and optical characterisation of platinum(ii) poly-yne polymers incorporating substituted 1,4-diethynylbenzene derivatives and an investigation of the intermolecular interactions in the diethynylbenzene molecular precursors

Abstract

A series of 1,4-diethynylbenzene (1) derivatives, H–CC–R–CC–H with R = C₆H₃NH₂ (2), C₆H₃F (3), C₆H₂F₂-2,5 (4), C₆F₄ (5), C₆H₂(OCH₃)₂-2,5 (6) and C₆H₂(OⁿC₈H₁₇)₂-2,5 (7) has been synthesised and their crystal structures determined by single crystal (2–5) or powder (6, 7) X-ray diffraction. The CCH⋯π_CC hydrogen bonds dominating structure 1 are gradually replaced by CC–H⋯F ones with the increase of fluorination (3 → 5), or completely replaced by CCH⋯N and NH⋯π_CC bonds in 2, and CCH⋯O in 6 and 7. The related platinum-based polymers, trans-[–Pt(PⁿBu₃)₂–CC–R–CC–]_n (R = as above and C₆H₄,) have been prepared and characterised by spectroscopic methods and thermogravimetry, which show that the amino- and methoxy-derivatives have lowest thermal stability while the fluorinated ones exhibit increasing thermal stability with increasing fluorination. Optical spectroscopic measurements reveal that substituents on the aromatic spacer group do not create strong donor–acceptor interactions along the rigid backbone of the organometallic polymers.