Interaction Types in C 6 H 5 (CH 2 ) n OH-CO 2 ( n = 0-4) Determined by the Length of the Side Alkyl Chain.

C 6 H 5 (CH 2 ) n OH-CO 2 complexes have been investigated using rotational spectroscopy ( n = 0-2) complemented by quantum chemical calculations ( n = 0-4), which implies that the side alkyl chain length can determine the types of intermolecular interactions. Unlike the in-plane C···O tetrel bond in phenol-CO 2 , the π* CO 2 ···π aromatic interaction has been shown to link CO 2 to phenylmethanol and 2-phenylethanol, which is, to the best of our knowledge, the first time it has been demonstrated by rotational spectroscopy. Further elongations of the side alkyl chain gradually increase the energies of intramolecular hydrogen bonds in 3-phenylpropanol and 4-phenylbutanol so that CO 2 cannot break it. CO 2 will be pushed farther from the monomers and link with the -OH group through a dominating C···O tetrel bond. Our observations would allow, with the choice of the proper length of the side alkyl chain, new strategies for engineering C···π aromatic -centered noncovalent bonding schemes for the capture, utilization, and storage of CO 2 .