Does DFTD estimate accurate energies for the binding of ligands to metal complexes?
(2011) In Dalton Transactions 40(Online 19 Aug 2011). p.1117611183 Abstract
 We have studied the homolytic dissociation of a methyl radical from a model of methyl cobalamin. For this reaction, density functional theory with an atompairwise dispersion correction (DFTD) gives a dispersion contribution to the bond dissociation energy (BDE) of 2251 kJ mol(1) depending on the functional, i.e. much more than common estimates for the total dispersion interaction energy of the methyl group in typical solvents. We show that this large energy correction results from many rather small (02 kJ mol(1)) interactions that arise between the ligand and the metal and the other ligands when a short metalligand bond is formed. The energy terms result mostly from atom pairs connected by two or three bonds, i.e. terms that... (More)
 We have studied the homolytic dissociation of a methyl radical from a model of methyl cobalamin. For this reaction, density functional theory with an atompairwise dispersion correction (DFTD) gives a dispersion contribution to the bond dissociation energy (BDE) of 2251 kJ mol(1) depending on the functional, i.e. much more than common estimates for the total dispersion interaction energy of the methyl group in typical solvents. We show that this large energy correction results from many rather small (02 kJ mol(1)) interactions that arise between the ligand and the metal and the other ligands when a short metalligand bond is formed. The energy terms result mostly from atom pairs connected by two or three bonds, i.e. terms that normally are ignored or scaled down at the molecular mechanics level, and have large contributions from r(8) terms. The added dispersion energy diminishes the variation in the calculated BDE observed among various generalisedgradient approximation (GGA) functionals, whereas a gap still persists between the results of GGA and hybrid functionals. Model calculations at the local MP2 and CCSD (secondorder perturbation theory and coupled cluster theory with single and double excitations) levels are in a similar range as the dispersion interactions estimated by DFTD (2329 kJ mol(1)). However, both the DFTD and the wavefunctionbased results include middlerange correlation effects that vary greatly between different DFT methods owing to their different densitybased description in the shortrange regime. Therefore, it is not meaningful to discuss which DFT method gives the most accurate estimate of the dispersion contribution to the BDE. Moreover, for a balanced treatment of dispersion during the binding reaction in solution, the dispersion energy of the ligand and the unbound complex with the surroundings needs also to be considered, which decreases the net dispersion contribution to binding by ~20 kJ mol(1). (Less)
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http://lup.lub.lu.se/record/2150854
 author
 Ryde, Ulf ^{LU} ; Mata, Ricardo A and Grimme, Stefan
 organization
 publishing date
 2011
 type
 Contribution to journal
 publication status
 published
 subject
 in
 Dalton Transactions
 volume
 40
 issue
 Online 19 Aug 2011
 pages
 11176  11183
 publisher
 Royal Society of Chemistry
 external identifiers

 wos:000296024000015
 pmid:21853206
 scopus:80055021247
 ISSN
 14779234
 DOI
 10.1039/c1dt10867k
 language
 English
 LU publication?
 yes
 id
 447ec855a93045feb096810776ecd5ff (old id 2150854)
 date added to LUP
 20110831 11:02:20
 date last changed
 20160920 05:34:15
@article{447ec855a93045feb096810776ecd5ff, abstract = {We have studied the homolytic dissociation of a methyl radical from a model of methyl cobalamin. For this reaction, density functional theory with an atompairwise dispersion correction (DFTD) gives a dispersion contribution to the bond dissociation energy (BDE) of 2251 kJ mol(1) depending on the functional, i.e. much more than common estimates for the total dispersion interaction energy of the methyl group in typical solvents. We show that this large energy correction results from many rather small (02 kJ mol(1)) interactions that arise between the ligand and the metal and the other ligands when a short metalligand bond is formed. The energy terms result mostly from atom pairs connected by two or three bonds, i.e. terms that normally are ignored or scaled down at the molecular mechanics level, and have large contributions from r(8) terms. The added dispersion energy diminishes the variation in the calculated BDE observed among various generalisedgradient approximation (GGA) functionals, whereas a gap still persists between the results of GGA and hybrid functionals. Model calculations at the local MP2 and CCSD (secondorder perturbation theory and coupled cluster theory with single and double excitations) levels are in a similar range as the dispersion interactions estimated by DFTD (2329 kJ mol(1)). However, both the DFTD and the wavefunctionbased results include middlerange correlation effects that vary greatly between different DFT methods owing to their different densitybased description in the shortrange regime. Therefore, it is not meaningful to discuss which DFT method gives the most accurate estimate of the dispersion contribution to the BDE. Moreover, for a balanced treatment of dispersion during the binding reaction in solution, the dispersion energy of the ligand and the unbound complex with the surroundings needs also to be considered, which decreases the net dispersion contribution to binding by ~20 kJ mol(1).}, author = {Ryde, Ulf and Mata, Ricardo A and Grimme, Stefan}, issn = {14779234}, language = {eng}, number = {Online 19 Aug 2011}, pages = {1117611183}, publisher = {Royal Society of Chemistry}, series = {Dalton Transactions}, title = {Does DFTD estimate accurate energies for the binding of ligands to metal complexes?}, url = {http://dx.doi.org/10.1039/c1dt10867k}, volume = {40}, year = {2011}, }