Abstract
Minimum energy structures of neutral and radical cations of end
substituted thia[n]helicenes (n=1-10) in DCM solvent are reported.
For both neutral and radical cations of these helicenes, calculated
structures are non-planar for n=3-10. Helical structures are obtained
for higher helicenes and thia[8]helicene system has a helical
structure with one complete turn. Equilibrium geometries are predicted
applying B3LYP-D/6-311++G(d,p) method in conjunction with SMD solvent
model. Single point energy calculations are also performed at MP2 level
to improve certain energy parameters. Excited state calculations are
performed using Time-Dependent Density Functional Theory (TDDFT)
formalism to predict UV-Visible spectra of neutral and radical cations
of thia[n]helicenes in DCM solvent. Thia[n]helicenes radical
cation have strong absorption in the near IR region. Calculations also
suggest that dimerization is not a favourable process in DCM solvent for
the end substituted neutral and radical cation of thia[7]helicene.
The present theoretical study examines the molecular and electronic
properties of thia[n]helicenes in search of near infrared electronic
devices.