Table 1. Weak Hydrogen Bonding Parameters for the T-Shaped Dimers.

T-shaped dimer	ΔHIPa (kcal/mol)	db (Å)
Ethyne Dimer
PM3	–1.04	2.5
ab initio(49)	–1.03c	2.695
Propyne Dimer
PM3	–1.14	2.5
ab initio(48)	–1.1	2.67

^aThe minimum weak interaction energy for the dimer.

^bThe C–H···π (M) distance for the corresponding energy, where M is the middle point of the C≡C bond.

^cOriginally calculated in kJ/mol and it was converted into kcal/mol in this paper.