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

A series of 1,4-diethynylbenzene (1) derivatives, H-Cequivalent toC-R-Cequivalent toC-H with R=C6H3NH2 (2), C6H3F(3), C6H2F2-2,5 (4), C6F4 (5), C6H2(OCH3)(2)-2,5 (6) and C6H2 ((OC8H17)-C-n)(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 Cequivalent toCH...pi(Cequivalent toC) hydrogen bonds dominating structure 1 are gradually replaced by Cequivalent toC-H...F ones with the increase of fluorination (3-->5), or completely replaced by Cequivalent toCH...N and NH...pi(Cequivalent toC) bonds in 2, and Cequivalent toCH...O in 6 and 7. The related platinum-based polymers, trans-[Pt((PBu3)-Bu-n)(2)-Cequivalent toC-R-Cequivalent toC-](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.