What is it about?
Quantum chemical study of interactions in the van der Waals dimer, the singlet and triplet excimers, and the cation and the anion of ethylene dimer were studied using exchange perturbation theory. The study provides valuable information about the nature of the molecular interactions between two neutral molecules, between a neutral molecule and its excited partner, and between a neutral molecule and its ion.
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Why is it important?
The various sigma- and pi-electron interaction terms for different conformations of the dimeric species are determined by using the exchange perturbation method. The results predict that the singlet excimer and the dimer cation are stable primarily because of the large magnitude of the exciton-resonance and charge-resonance terms, respectively. The neutral dimer, the triplet excimer, and the dimer anion are weakly stable. The variations of the different energy terms with conformations suggest that these dimeric species cannot have identifical structure.
Perspectives
This investigation leads to the following major conclusions: (1) The lowest singlet excimer and the ground state of the dimer cation of ethylene are stable primarily because of the large magnitude of the exciton-resonance and charge-resonance terms, respectively. (2) Since the exciton-resonance and the charge-resonance terms are less important in the triplet excimer and the ground state of the dimer anion, respectively, the binding and the equilibrium conformations of these species are controlled by the weak van der Waal's dispersion forces as in the corresponding ground-state neutral dimer.
E.J. Padma Malar
University of Madras
Read the Original
This page is a summary of: Intermolecular potentials in the dimer, the excimers, and the dimer ions of ethylene, The Journal of Physical Chemistry, July 1981, American Chemical Society (ACS),
DOI: 10.1021/j150615a011.
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