A Cyclic Periodic Wave Function Approach for the Study of Infinitely Periodic Solid-State Systems. I. Application to the C–H···π(C≡C) Hydrogen Bonding Systems

[Image: see text] The cyclic periodic wave function (CPWF) approach is applied at the AM1 and PM3 semiempirical levels of approximation to infinitely periodic solid-state systems stabilized by weak CH–pi (C–H···π) interactions between repeat units. The reliability of the AM1 and PM3 methods for modeling C–H···π bonding is first demonstrated using two representative dimer systems: the T-shaped ethyne dimer and the T-shaped propyne dimer. The CPWF method is then applied to two different crystal systems that are stabilized by C–H···π interactions: (1) pent-4-ynoic acid solid and (2) a series of three infinite crystal systems—tetrakis(4-ethynylphenyl)methane solid, tetraethynylmethane solid, and tetrabutadiynylmethane solid. A comparison of our results with available data demonstrates that the use of the CPWF approach at the AM1 and PM3 levels of approximation provides a convenient and reliable method for the study of infinitely periodic systems containing very weak C–H···π bonding.