Trimethylsilyl-protected di-alkynes incorporating azobenzene linker groups, Me3Si─C≡C─R─C≡C─SiMe3 (R = azobenzene-3,3’-diyl, azobenzene-4,4’-diyl, 2,5-bisoctylazobenzene-4,4’-diyl), and the corresponding terminal dialkynes, H─C≡C─R─C≡C─H, have been synthesised and characterized. The CuI-catalyzed dehydrohalogenation reaction between trans-[Ph(Et3P)2PtCl] and the deprotected dialkynes in a 2:1 ratio in iPr2NH/CH2Cl2 gives the Pt(II) di-ynes trans-[Ph(Et3P)2Pt─C≡C─R─C≡C─Pt(PEt3)2Ph], while the dehydrohalogenation polycondensation reaction between trans-[(nBu3P)2PtCl2] and the dialkynes in a 1:1 molar ratio under similar reaction conditions affords the Pt(II) poly-ynes, [─Pt(PnBu3)2─C≡C─R─C≡C─]n. The materials have been characterized spectroscopically, with the di-ynes also studied using single-crystal X-ray diffraction. The Pt(II) di-ynes and poly-ynes are all soluble in common organic solvents. Optical-absorption measurements show that the compounds incorporating the para-azobenzene spacer have a higher degree of electronic delocalisation than their meta-azobenzene counterparts. Reversible photoisomerization in solution was observed spectroscopically for the alkynyl-functionalised azobenzene ligands and, to a lesser extent, for the Pt(II) complexes. Complementary quantum-chemical modelling was also used to analyse the optical properties and the isomerisation energetics.
- Pt(II) acetylide complexes
- Time-dependent Density Functional Theory