[shenanigans]

I have created some unsymmetrical cyanine dyes. cyanine dyes consist of 2 nitrogen containing heterocycles connected by a polymethine bridge and have 2 resonance forms. In a symmetrical cyanine dye the 2 resonance forms are the same (the heterocycles are the same on both sides), but in an unsymmetrical dye the heterocycles are different.

I would like to find a program that will map the electron density to show which heterocycle contains the positive charged nitrogen more often. I've been recommended Gaussian, but am still in the process of learning it. Does anyone else have any recommendations?

[curiouscat]

Gaussian's great but you'll need to pay for a license. VASP, QuantumEspresso, Wein2k, Siesta etc. are other options.

[amid]

if you are concerned by density (charges) of the average system, any ab initio program would indeed do it.
As a freeware, I would also recommend to download GAMESS and its freeware builder/visualizer MacMolplot. It might save time some times learning how to use it. Be sure you use some reasonnable ab initio level (Hartree-Fock or DFT with a decent basis set (*at least* double zeta + polarization  - 6-31G(d) for instance for geometry optimization and density evaluation).

For resonance (mesomeric) forms, you can have some weight information using NBO/NRT approximation, but I beleive the NBO 5.0 version is required (usually NBO 3.0 is embedded in codes). Version 5.0 is not free. It also requires some learning.

Last, if you use planar (pi conjugated external part), you can search for Huckel freewares. They require no knowledge in quantum chemistry package. They can give you reasonnable charges, and some can give you the weights of the mesomeric forms.