Crystal and molecular structures of tetrathia[7]heterohelicene: racemate and enantiomer

Investigation of NLO properties of substituted (M)‐tetrathia‐[7]‐helicenes by semiempirical and DFT methods

“…In Table I, the optimized geometries of (M)-tetrathia- [7]-helicene (1) at the B3LYP/6-311G, B3LYP/6-31G**, and AM1 levels [25] are compared with the available X-ray structure [26]. The geometric parameters are in good agreement with the Xray diffraction data and only small deviations can be observed, the semiempirical AM1 optimized structure being the closest to the X-ray one.…”

Tetrathiaheterohelicene Phosphanes as Helical‐Shaped Chiral Ligands for Catalysis

“…The computed C2-C13 distance for 2c (4.435 Å) is only slightly greater than that observed in racemic tetrathiahelicene (4.171 Å), [23] indicating a minor influence of the phenylphosphane groups on the distortion of the 7-TH skeleton. As expected, both the C2-C13 distance and all the dihedral angles (except those between the inner rings C/D and CЈ/ DЈ) decrease significantly on going from 2c to 8 (see Table 1), as a consequence of the constraint imposed by coordination to the metal atom.…”

“…The values of such dihedral angles computed for 2c range from 9.0-11.5°for the adjacent rings and is equal to 50.2°f or the terminal thiophene rings, resembling those observed www.eurjoc.org in the crystal structure of the racemic tetrathiahelicene [23] [8.6(1)-11.3(1)°and 48.6(1)°, respectively]. The computed C2-C13 distance for 2c (4.435 Å) is only slightly greater than that observed in racemic tetrathiahelicene (4.171 Å), [23] indicating a minor influence of the phenylphosphane groups on the distortion of the 7-TH skeleton.…”

Silyl‐Substituted Tetrathia[7]helicenes: Synthesis, X‐ray Characterization and Reactivity

“…The obtained structural parameters were compared with those of the tetrathia [7]helicene, 1 (see Table 2). [15] A view of the molecule is shown in Figure 5, together with the atomic labelling scheme. The C-C outer core bonds of 4b are shorter and the C-C inner core bonds are longer than the expected 1.39 Å, as already observed in the unsubstituted helicene and in several carbo-and heterohelicenes [15] as well as in its precursor 3b.…”

“…[15] A view of the molecule is shown in Figure 5, together with the atomic labelling scheme. The C-C outer core bonds of 4b are shorter and the C-C inner core bonds are longer than the expected 1.39 Å, as already observed in the unsubstituted helicene and in several carbo-and heterohelicenes [15] as well as in its precursor 3b. All seven fused rings are deviated from planarity as evidenced in Table 3 and there is an increase in the deformation passing from the external A and AЈ rings to the central D ring (see Scheme 8 for nomenclature of fused rings).…”