Quantum chemical calculations have been performed to study the structure and properties of the pi hydrogen-bonded complex formed between acetylene and HArCCF at the MP2/6-311++G(2d,2p) level. The C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes were also studied for comparison with the C(2)H(2)...HArCCF complex. The basis set superposition errors (BSSE)-counterpoise corrected potential-energy surface (PES) has a larger influence on the structure and properties of the C(2)H(2)...HArCCF complex than those of the C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes. The C(2)H(2)...HArCCF complex exhibits a very large harmonic vibrational frequency blue shift of 574 cm(-1) for the H-Ar stretch, whereas the C(2)H(2)...HCCF and C(2)H(2)...HCCArF complexes exhibit a small red shift of 35 and 47 cm(-1) for the H-C stretch, respectively; upon complexation the IR intensity decreases in the former, whereas it increases in the latter. The origin of the frequency shift and nature of the hydrogen bond in these complexes have been unveiled with the natural bond orbital analysis and energy decomposition.