Chiroptical titanium complexes as catalytically active chiral dopants available for asymmetric acetylene polymerization

Chiroptical titanium complexes are expected not only to serve as a chiral dopant to nematic liquid crystals (LCs) to give an induced chiral nematic (N*) phase, but also to play a role of catalyst itself. Here, we synthesized some kinds of chiral titanium complexes that might be available for synthesis of helical (CH)(x). Axially chiral binaphthol derivatives, (R)- and (S)-6,6'-di-(4-(tranas-4-n-pentylcyclohexyl)phenoxy-l-hexyl)-2,2'-dihydroxy-1,1'-binaphtyl (6, 6'-PCH506-Binol) and chiral center-containing (R)- and (S)-2-octanol (HO-2-octyl) were adopted as coordination ligands of titanium complexes to yield (R)- and (S)-Ti(O-6, 6'-PCH506-Binaphtyl)(2) (1), and Ti(O-2-octyl)(4) (2). We found that these complexes induce the N* phase when dissolved in nematic LCs and they are catalytically active for acetylene polymerization. Positive or negative Cotton effect was observed in the region of pi --> pi* transition of polyene chain in circular dichroism(CD) spectra of the (CH)(x) thin films. It is evident that the main chain is helically screwed, taking account of no existence of chiroptical substituent in side chains.