Dariusz W. Szczepanik1,2
1 Department of Theoretical Chemistry, Jagiellonian University
Faculty of Chemistry, Gronostajowa 2, 30-387 Krakow, Poland
2 Institute of Computational Chemistry and Catalysis, University of Girona
C/ Maria Aurèlia Capmany, 69, 17003 Girona, Catalonia, Spain
What is EDDB?
The Electron Density of Delocalized Bonds (EDDB) enables one to visualize and quantify chemical resonance, multicenter bonding and aromaticity in a wide range of chemical species. It relies on the following decomposition scheme:
The quantitative predictions of global and local aromaticity by EDDB are in excellent agreement with a wide range of descriptors based on structural, magnetic, and electronic-structure criteria of aromaticity. There are several important features, however, that set the EDDB method apart from other aromaticity descriptors:
- EDDB does not suffer from the ring-size extensivity issue and can be used to study electron delocalization in any type of aromatic system regardless of its size and topology (in contrast to e.g. NICS and PDI);
- EDDB does not depend upon parametrization to the reference model system (in contrast to e.g. HOMA and FLU);
- EDDB provides aromaticity predictions very similar to MCI but is much less computationally expensive and does not share the numerical-accuracy and method-dependence problems;
- EDDB enables one to quantify delocalization of electrons within the framework of the first-order population analysis (the number of electrons delocalized through the system of conjugated bonds), so the results are much easier to interpret than those from other approaches.
- EDDB provides a great deal of information on the atom/orbital contribution to electron delocalization and as such it can be used e.g. to investigate the role of the metal d-orbitals in organometallic aromatics ( in contrast to e.g. NICS and ACID).
The RunEDDB program is an R-based implementation of the EDDB method, and its current version works with Gaussian formatted checkpoint files for closed- and open-shell systems at the HF/DFT theory level.