Thermally accessible triplet state of pi-nucleophiles does exist. Evidence from first principles study of ethylene interaction with copper species
2015 (English)In: RSC Advances, ISSN 2046-2069, Vol. 5, no 15, 11558-11569 p.Article in journal (Refereed) Published
Three different models of ethylene interaction with copper species, namely, the Cu(100) surface, odd-numbered copper clusters C2H4/Cu-n (where n = 3, 7, 11, 15, 17, 19, 21, 25 and 27) and atomic copper C2H4/Cu were studied theoretically. It was found that the ethylene molecule possesses three different types of bonding depending on the presence of the unpaired spin on the reacting copper atom. These bonding structures demonstrate different types of band gap (bulk) or SOMO-LUMO gaps (cluster/atom), where SOMO stands for the singly occupied and LUMO means the lowest unoccupied molecular orbitals of the copper species. The obtained results are in good agreement with the previous experimental and computational results on the structural, spectral and energetic properties of the studied species. The bulk copper and sub-nanosized clusters (n > 7) build up the mono-pi-bonded ground state complexes with ethylene where the latter species possesses the C-2v symmetry. The single-atom complex C2H4/Cu forms the CS-symmetrical ground state (X) over tilde (2)A' and the excited B-2(2) and B-4 state complexes of the C-2v and C-2 symmetry, respectively. The (X) over tilde (2)A' state complex is mono-sigma-bonded and involves the singlet ethylene moiety. The more tightly bound excited B-2(2) complex has the di-sigma-bonded structure and corresponds to the triplet ethylene. The adiabatic energy difference between the B-2(2) and (X) over tilde (2)A' states is equal to 10.8 kcal mol(-1) and can be ascribed to the singlet-triplet splitting of the ethylene moiety interacting with copper. The QTAIM analysis supports the coordination type of the Cu-C bonds in all the studied complexes. Formation of the C2H4/Cu(100), C2H4/Cu-n and C2H4/Cu species is in accord with the well-known Dewar-Chatt-Duncanson model, in such a way that the opposing sigma-donation step yields the ground state complex ((X) over tilde (2)A'), while the subsequent more expensive supporting pi*-back donation step provides the excited B-2(2) state complex. In the present paper we have developed a computational procedure to optimize the latter complex.
Place, publisher, year, edition, pages
2015. Vol. 5, no 15, 11558-11569 p.
IdentifiersURN: urn:nbn:se:kth:diva-161154DOI: 10.1039/c4ra12422gISI: 000348986900085ScopusID: 2-s2.0-84962418064OAI: oai:DiVA.org:kth-161154DiVA: diva2:796468
FunderSwedish National Infrastructure for Computing (SNIC), SNIC 020/11-23
QC 201503192015-03-192015-03-092015-03-19Bibliographically approved