Pi Orbital Electronegativity - JChem vs. Marvin?

trying to understand why PiOrbitalElectronegativity calculation in JChem vs Marvin are different?  Tested on few molecules so far:

example - Diclofenac:

(atom # 19 - Cl per Marvin atom numbering)

using excel: JCOrbitalElectronegativity("SMILES",19) =#VALUE

in Marvin: Orbital Electonegativity plugin = 5.40

 

(atom # 12 - C on ring per Marvin atom numbering)

using excel: JCOrbitalElectronegativity("SMILES",12) = 5.53

in Marvin: Orbital Electonegativity plugin = 5.77

 

thanks in advance for the clarification.

 

Hi,
 
The observed difference originates from the fact that atom numbering in case of SMILES starts from #0, while in MarvinSketch atom numbering starts from #1.
You should use the function "JCPiOrbitalElectronegativity("SMILES",18)" in excel if you want to see the pi orbital electronegativity value of the atom # 19 presented in MarvinSketch.
Also, JCPiOrbitalElectronegativity("SMILES",11) for piOEN value of atom # 12 presented in MarvinSketch.

Best Regards,

Viktoria