Thia‐bridged triarylamine hetero[4]helicenes (TBTH[4]H) are a peculiar class of geometrically stable [4]helicenes that have shown promising applications as organic electronic materials. Their structure comprises a bis‐phenothiazine moiety, with a nitrogen atom and an aromatic ring in common, forced into a helix‐shaped arrangement by four carbon–sulfur bonds. We describe a detailed study on the scope and application of the electrophilic sulfur insertion path to TBTH[4]H, with particular emphasis on the regioselective preparation of asymmetric (not dissymmetric) derivatives.

species of helicenes 1-9 have been measured and calculated to afford a complete rationalization of the redox behaviour of these appealing chiral compounds.

In the past few years, the chirality and magnetism of molecules have received notable interest for the development of novel molecular devices. Chiral helicenes combine both these properties, and thus their nanostructuration is the first step toward developing new multifunctional devices. Here, we present a novel strategy to deposit a sub‐monolayer of enantiopure thia[4]helicene radical cations on a pre‐functionalized Au(111) substrate. This approach results in both the paramagnetic character and the chemical structure of these molecules being maintained at the nanoscale, as demonstrated by in‐house characterizations. Furthermore, synchrotron‐based X‐ray natural circular dichroism confirmed that the handedness of the thia[4]helicene is preserved on the surface.

The Chirality Induced Spin Selectivity (CISS) effect describes the capability of chiral molecules to act as spin filters discriminating flowing electrons according to their spin state. Within molecular spintronics, efforts are focused on developing chiral-molecule-based technologies to control the injection and coherence of spin-polarized currents. Herein, for this purpose, we study spin selectivity properties of a monolayer of a thioalkyl derivative of a thia-bridged triarylamine hetero[4]helicene chemisorbed on a gold surface. A stacked device assembled by embedding a monolayer of these molecules between ferromagnetic and diamagnetic electrodes exhibits asymmetric magnetoresistance with inversion of the signal according to the handedness of molecules, in line with the presence of the CISS effect. In addition, magnetically conductive atomic force microscopy reveals efficient electron spin filtering even at unusually low potentials. Our results demonstrate that thia[4]heterohelicenes represent key candidates for the development of chiral spintronic devices.

A series of thia-bridged triarylamine[4]helicene-functionalized polynorbornenes P1, P2, and P3 were synthesized via ring-opening metathesis polymerization (ROMP). The polymers obtained undergo a reversible one-electron oxidation, in both solution and solid state, responding to the pH changes in the surrounding medium showing a clear reversible electrochromic behavior.

In the past few years, the chirality and magnetism of molecules have received notable interest for the development of novel molecular devices. Chiral helicenes combine both these properties, and thus their nanostructuration is the first step toward developing new multifunctional devices. Here, we present a novel strategy to deposit a sub‐monolayer of enantiopure thia[4]helicene radical cations on a pre‐functionalized Au(111) substrate. This approach results in both the paramagnetic character and the chemical structure of these molecules being maintained at the nanoscale, as demonstrated by in‐house characterizations. Furthermore, synchrotron‐based X‐ray natural circular dichroism confirmed that the handedness of the thia[4]helicene is preserved on the surface.

We have developed an efficient chemical resolution of racemic hydroxy substituted dithia-aza[4]helicenes (DTA[4]H) 1(OH) using enantiopure acids as resolving agents. The better diastereomeric separation was achieved on esters prepared with (1S)-(−)-camphanic acid. Subsequent simple manipulations produced highly optically pure (≥ 99% enantiomeric excess) (P) and (M)-1(OH) in good yields. The role of the position where the chiral auxiliary is inserted (cape- vs bay-zone) and the structure of the enantiopure acid used on successful resolution are discussed.

N-thiophthalimido-arylphenothiazines 2 and triarylamines 3 can be converted to dithiabridged triarylamine hetero[4]helicenes 1 using catalytic amounts of chalcogen substituted Lewis Bases and hexafluoro isopropanol as hydrogen bond donor. The procedure occurs under mild reaction conditions and gives good yields avoiding the use of excesses of Lewis Acids as previously reported. A preliminary study about the possibility to control the M and P absolute stereochemistry of helicenes 1 using enantiopure sulfur containing LBs from the natural chiral pool is also reported.