Exotic isomers of dicyanoacetylene: A density functional theory and ab initio study
Abstract
Prospects for the existence and detection of yet unknown dicyanoacetylene (NCCCCN) isomers are discussed, based on quantum-chemical calculations for linear, hexagonal and branched C4N2 structural variants. It is concluded that apart from dicyanoacetylene itself and its two already discovered isomers, NCCCNC and CNCCNC, at least two other species are of importance: linear CCCNCN and Y-shaped CC(CN)CN (dicyanovinylidene). Combined CCSD(T) and MP4 calculations predict CC(CN)CN and CCCNCN to be 57 kcal/mol and 66 kcal/mol less stable than dicyanoacetylene, respectively. The height of the energy barrier for dicyanoacetylene←dicyanovinylidene isomerization is about 5 kcal/mol. Density functional theory calculations indicate that CCCNCN should give rise to prominent IR absorption bands, two orders of magnitude stronger than those of dicyanoacetylene.
- Publication:
-
Journal of Chemical Physics
- Pub Date:
- August 2002
- DOI:
- 10.1063/1.1489992
- Bibcode:
- 2002JChPh.117.2063K
- Keywords:
-
- organic compounds;
- isomerism;
- molecular configurations;
- density functional theory;
- ab initio calculations;
- coupled cluster calculations;
- perturbation theory;
- Isomers;
- Molecular Structure;
- Organic Compounds;
- Perturbation Theory;
- 31.15.Ew;
- 31.15.Ar;
- 33.15.Bh;
- 31.15.Dv;
- Atomic and Molecular Physics;
- Density-functional theory;
- Ab initio calculations;
- General molecular conformation and symmetry;
- stereochemistry;
- Coupled-cluster theory