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, aromaticity, hyper- and multicenter bonding 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.