Nuclear quadrupole interactions in cadmium complexes : Semiempirical and ab initio calculations
(1999) In Zeitschrift fur Naturforschung  Section A Journal of Physical Sciences 54(67). p.422430 Abstract
Semiempirical calculations, based on the socalled angular overlap model, have been compared with ab initio methods (MP2) for the calculation of nuclear quadrupole interactions (NQI's) in cadmium complexes with biologically relevant ligands (H_{2}O, OH^{}, cysteinate, carboxylate, and imidazole). The assumptions on which the semiempirical model is based have been tested and the comparison indicates that: 1) A change in the Cdligand bond length by 0.1 Å may change the electric field gradient (EFG) by about 0.2 a. u.. A simple scheme to incorporate such effects in the semiempirical method is suggested. 2) The effect of ligandligand interactions is up to about 0.2 a. u. for the largest diagonal element of the EFG tensor... (More)
Semiempirical calculations, based on the socalled angular overlap model, have been compared with ab initio methods (MP2) for the calculation of nuclear quadrupole interactions (NQI's) in cadmium complexes with biologically relevant ligands (H_{2}O, OH^{}, cysteinate, carboxylate, and imidazole). The assumptions on which the semiempirical model is based have been tested and the comparison indicates that: 1) A change in the Cdligand bond length by 0.1 Å may change the electric field gradient (EFG) by about 0.2 a. u.. A simple scheme to incorporate such effects in the semiempirical method is suggested. 2) The effect of ligandligand interactions is up to about 0.2 a. u. for the largest diagonal element of the EFG tensor for the tested complexes, and such effects can significantly influence the socalled asymmetry parameter. 3) The position of noncoordinating atoms on the ligands can in some cases (e. g. the hydrogen atoms of water) significantly influence the EFG. The combined effect of noncoordinating atoms and ligandligand interactions may cause deviations of up to 0.35 a. u. between ab initio and the semiempirical calculations. 4) In the semiempirical model each ligand is characterised by one parameter, the socalled partial nuclear quadrupole interaction. This parameter has been evaluated by ab initio calculations, and agreement was found within about 0.2 a. u. (≈ 40 Mrad/s) for all ligands except imidazole. 5) A change in the coordination number from 2 to 6 may change the partial NQI by about 0.3 a. u.
(Less)
 author
 Hemmingsen, Lars; Ryde, Ulf ^{LU} and Bauer, Rogert
 organization
 publishing date
 199906
 type
 Contribution to journal
 publication status
 published
 subject
 keywords
 Angular Overlap Model, Electric Field Gradient, Ligand Additivity
 in
 Zeitschrift fur Naturforschung  Section A Journal of Physical Sciences
 volume
 54
 issue
 67
 pages
 9 pages
 publisher
 De Gruyter
 external identifiers

 scopus:0040122450
 ISSN
 09320784
 DOI
 10.1515/zna19996713
 language
 English
 LU publication?
 yes
 id
 e4cb55e46a024a6283d25fe0db351678
 date added to LUP
 20170204 11:41:03
 date last changed
 20190106 12:55:15
@article{e4cb55e46a024a6283d25fe0db351678, abstract = {<p>Semiempirical calculations, based on the socalled angular overlap model, have been compared with ab initio methods (MP2) for the calculation of nuclear quadrupole interactions (NQI's) in cadmium complexes with biologically relevant ligands (H<sub>2</sub>O, OH<sup></sup>, cysteinate, carboxylate, and imidazole). The assumptions on which the semiempirical model is based have been tested and the comparison indicates that: 1) A change in the Cdligand bond length by 0.1 Å may change the electric field gradient (EFG) by about 0.2 a. u.. A simple scheme to incorporate such effects in the semiempirical method is suggested. 2) The effect of ligandligand interactions is up to about 0.2 a. u. for the largest diagonal element of the EFG tensor for the tested complexes, and such effects can significantly influence the socalled asymmetry parameter. 3) The position of noncoordinating atoms on the ligands can in some cases (e. g. the hydrogen atoms of water) significantly influence the EFG. The combined effect of noncoordinating atoms and ligandligand interactions may cause deviations of up to 0.35 a. u. between ab initio and the semiempirical calculations. 4) In the semiempirical model each ligand is characterised by one parameter, the socalled partial nuclear quadrupole interaction. This parameter has been evaluated by ab initio calculations, and agreement was found within about 0.2 a. u. (≈ 40 Mrad/s) for all ligands except imidazole. 5) A change in the coordination number from 2 to 6 may change the partial NQI by about 0.3 a. u.</p>}, author = {Hemmingsen, Lars and Ryde, Ulf and Bauer, Rogert}, issn = {09320784}, keyword = {Angular Overlap Model,Electric Field Gradient,Ligand Additivity}, language = {eng}, number = {67}, pages = {422430}, publisher = {De Gruyter}, series = {Zeitschrift fur Naturforschung  Section A Journal of Physical Sciences}, title = {Nuclear quadrupole interactions in cadmium complexes : Semiempirical and ab initio calculations}, url = {http://dx.doi.org/10.1515/zna19996713}, volume = {54}, year = {1999}, }