Synthesis, spectroscopy, structures and photophysics of metal alkynyl complexes and polymers containing functionalized carbazole spacers

A new class of soluble and thermally stable group 10 platinum(II) poly-yne polymers functionalized with 9-arylcarbazole moiety trans--Pt(PBu₃)₂CCRCC-]_n (R = 9-arylcarbazole-3,6-diyl; aryl = p-methoxyphenyl, p-chlorophenyl) were prepared in good yields by the polycondensation polymerization of trans-PtCl₂(PBu₃)₂] with HCCRCCH under ambient conditions. The optical absorption and emission properties of these polymetallaynes were investigated and compared with their bimetallic molecular model complexes trans-Pt(Ph)(PEt₃)₂CCRCCPt(Ph)(PEt₃)₂] as well as their group 11 gold(I) and group 12 mercury(II) neighbors (PPh₃)AuCCRCCAu(PPh₃)] and MeHgCCRCCHgMe]. The structures of all the compounds were confirmed by spectroscopic methods and by X-ray crystallography for selected model complexes. The influence of the heavy metal atom and the 9-aryl substituent of carbazole on the evolution of lowest electronic singlet and triplet excited states is critically characterized. It was shown that the organic-localized phosphorescence emission can be triggered readily by the heavy-atom effect of group 10-12 transition metals (viz., Pt, Au, and Hg) with the emission efficiency generally in the order Pt > Au > Hg. These carbazole-based organometallic materials possess high-energy triplet states of 2.68 eV or higher which do not vary much with the substituent of 9-aryl group.