A novel enantiopure bis-helicenic2,2′-bipyridine system was prepared using a Negishi coupling. Thanks to the bipyridine unit, the coordination with ZnII and protonation processes were studied, revealing efficient tuning of photophysical (UV/visible and emission) and chiroptical properties (electronic circular dichroism and circularly polarized emission) of the system. The coordination/decoordination
differently with either racemic or enantiopure 4‐aza[6]helicene, giving respectively cis (racemic) and trans (enantiopure) [PtIICl2(4‐aza[6]helicene)PPh3] complexes. This unexpected reactivity is explained through a dynamic process (crystallization‐induced diastereoselective transformation) and enables a new aspect of reactivity in chiral transition‐metal complexes to be addressed.
偶然发现,顺式[[PtCl 2(NCEt)PPh 3 ]与外消旋或对映纯4-氮杂[6]螺旋烯反应不同,分别产生顺式(外消旋)和反式(对映纯)[Pt II Cl 2(4氮杂[6] helicene)PPh 3 ]配合物。通过动态过程(结晶诱导的非对映选择性转化)解释了这种意外的反应性,并使手性过渡金属配合物的反应性有了新的方面。
Synthesis and Structural Properties of Aza[<i>n</i>]helicene Platinum Complexes: Control of Cis and Trans Stereochemistry
crystallographic analysis, we show that for both PtCl2(4H6)(PPh3) and PtCl2(5H6)(PPh3) there is chiralitycontrol of the cis/trans stereochemistry. Indeed, starting from a racemic mixture of aza[6]helicene, platinumcomplexes with a cis configuration are invariably obtained, and the more thermodynamically stable trans isomers are formed when using enantiopure ligands. We further corroborated these results by NMR
luminescence (CPL) from helicene racemates via supramolecular association with DNA in aqueous solution. Racemic cationic helicene derivatives are immobilized in the grooves of commercially available double-stranded right-handed DNA, and the discrimination of left- and right-handed helicenes by chiralDNA is monitored by singlemolecule force spectroscopy. This subsequently leads to the generation of prominent