Experimental and calculated vibrational and electronic circular dichroism spectra of 2-Br-hexahelicene.

The vibrational circular dichroism (VCD) and IR absorption spectra of the (-)-enantiomer of 2-Br-hexahelicene have been measured and interpreted by use of density functional theory (DFT) calculations. From time dependent DFT calculations we also interpret the electronic circular dichroism (ECD) spectra of 2-Br-hexahelicene. We compare the calculated IR, VCD and ECD spectra to the corresponding calculated data of hexahelicene and 2-aza-hexahelicene; for the last compound we also recorded the ECD spectra. Comparison with current literature allows an insight to be gained on the meaning and usefulness of some VCD features.

[1]  Benoît Champagne,et al.  Vibrational Raman optical activity of π‐conjugated helical systems: Hexahelicene and heterohelicenes , 2009, J. Comput. Chem..

[2]  J. Autschbach,et al.  Metal-bis(helicene) assemblies incorporating pi-conjugated phosphole-azahelicene ligands: impacting chiroptical properties by metal variation. , 2009, Journal of the American Chemical Society.

[3]  Ivo Starý,et al.  A straightforward route to helically chiral N-heteroaromatic compounds: practical synthesis of racemic 1,14-diaza[5]helicene and optically pure 1- and 2-aza[6]helicenes. , 2008, Angewandte Chemie.

[4]  E. Baerends,et al.  A vibrational circular dichroism implementation within a Slater-type-orbital based density functional framework and its application to hexa- and hepta-helicenes , 2008 .

[5]  B. Champagne,et al.  Circular dichroism of helical structures using semiempirical methods. , 2007, The Journal of chemical physics.

[6]  I. Lednev,et al.  Vibrational circular dichroism shows unusual sensitivity to protein fibril formation and development in solution. , 2007, Journal of the American Chemical Society.

[7]  T. Buffeteau,et al.  Vibrational circular dichroism and ab initio structure elucidation of an aromatic foldamer. , 2006, Chemical communications.

[8]  T. Daniel Crawford,et al.  Ab initio calculation of molecular chiroptical properties , 2006 .

[9]  Isabella Natali Sora,et al.  Monoaza[5]helicenes. Part 2: Synthesis, characterisation and theoretical calculations , 2006 .

[10]  A. Mele,et al.  Chiroptical Properties of Some Monoazapentahelicenes , 2004 .

[11]  J. Pendry.  A Chiral Route to Negative Refraction , 2004, Science.

[12]  A. Urakawa,et al.  The absolute configuration of heptahelicene: aVCD spectroscopy studyElectronic supplementary information (ESI) available: two calculated normal modes and CD spectra of the heptahelicene enantiomers. See http://www.rsc.org/suppdata/nj/b3/b312877f/ , 2004 .

[13]  A. Rajca,et al.  Determination of Absolute Configuration in Molecules with Chiral Axes by Vibrational Circular Dichroism: A C2-Symmetric Annelated Heptathiophene and a D2-Symmetric Dimer of 1,1‘-Binaphthyl , 2003 .

[14]  Stefan Grimme,et al.  Circular Dichroism of Helicenes Investigated by Time-Dependent Density Functional Theory , 2000 .

[15]  W. H. Laarhoven,et al.  A Hexahelicene, Racemization-resistant below 300°C. Synthesis, Conformation and Racemization Parameters of 1, 3-Di-tert-Butylhexahelicene , 1990 .

[16]  W. H. Laarhoven,et al.  Synthesis and spectroscopic properties of 1,4-diarylbutenynes , 1976 .

[17]  K. Trueblood,et al.  Hexahelicene. Absolute configuration , 1972 .

[18]  R. Chang.  Umbilical cord leucocytes transformed by lymphoid cell filtrates from healthy people. , 1971, Nature: New biology.

[19]  G. Zerbi,et al.  Dispersion Curves and Frequency Distribution of Polymers: Single Chain Model , 1968 .