ORCA - Electronic and Spectroscopic Properties of Olefins

Although restricted in which excited energy levels are accessed during the computation, to get a rough idea of the UV-Vis spectrum it is possible to invoke ORCA with an *.inp file in which the default settings can be sufficient.  The particular settings contained within the ORCA *.inp file employed to obtain the spectra presented here are as follows:

!  ZINDO/S 
! PrintBasis
%cis
     nroots 8 # the number of excited states to be calculated.
     maxdim 30 # the maximum dimension of the expansion space in the Davidson procedure.
     # Triplets true : do triplets states
     # EWin -3,100  (orbital energy window in Eh)
 end #cis
%output
     print[p_mos] 1
 end #output

Once the geometry of the molecule has been optimised, many molecular modelling graphical user interfaces offer a functionality to produce ORCA input files.  Despite the settings being different, the generated ORCA files can be viewed and the .xyz section obtained, which contains the atomic coordinates, spin multiplicity and charge.  A new .inp file can be created using the code above followed by the section beginning * xyz.  See example input file for (s-trans)-buta-1,3-diene.

Effects of substitution on the UV-Vis spectra of olefins

(s-trans)-buta-1,3-diene
	231
(s-trans,E)-1-chlorobuta-1,3-diene
	117, 109, 115,
(s-trans,Z)-1-chlorobuta-1,3-diene
	233, 186, 164
(s-trans)-1,1-dichlorobuta-1,3-diene
	239, 186, 199
(s-cis)-buta-1,3-diene
(s-cis,E)-1-chlorobuta-1,3-diene
	244, 160, 187 167
(s-cis,Z)-1-chlorobuta-1,3-diene
(s-cis)-1,1-dichlorobuta-1,3-diene
	249, 370, 411, 400,
	241