Structure, energetics and bonding of diacetylene complexes with hydrogen fluoride. A theoretical investigation

Ab initio calculations have been carried out on diacetylene-HF complexes both at the SCF and second-order Møller-Plesset level using a 6–31 + + G(d, p) basis set to determine the structures and association energies of the various possible forms of the complexes. The non-symmetric π complex has been found to be the most stable but the energy difference between the symmetric π and the reverse σ complex is small. The hydrogen bond lengths at the MP2 level are shorter by about 0.3 to 0.7 bohr than the respective SCF ones. Molecular electrostatic potential and electron density based topographical analyses, and qualitative model studies, have been carried out to elucidate the nature and strength of the bonding involved.