A theoretical exploration of different π-π stacking dimers of coronenes and its substituted analogues

Abstract

Quantum chemical calculations employing density functional theory have been performed to study the geometry, π-interactions and band gaps of coronene and its mono heteroatom substituted analogues. With the objective of systematic structural modification of coronene for the design of functional materials, the study focuses on the role of substitution of carbon in coronene with heteroatom boron or nitrogen on their interplanar π-interactions, band gaps and stabilization energies. The work intensively explores various π-π stacking interactions in dimers of coronenes, theoretically, paving the possible existence of different polymorphs arising from the dimers. The monomeric planes are stacked together through π-interactions with an interplanar distance of ∼ 3.3 Å to form dimers. A total of 36 dimers of substituted coronenes are formed in addition to their corresponding mirror images. Based on the geometries, the dimers are found to exist in five different types. The calculations show that the band gap of unsubstituted monomer coronene is 3.27 eV and upon substitution of a single carbon atom of coronene with heteroatom nitrogen or boron, the band gaps of monosubstituted coronenes are reduced to 0.81–1.16 eV and are dependent on the position of substitution. The band gaps of the dimers are further reduced compared to those of monomers attributing to π-π stacking interactions. The reduction is more in nitrogen-substituted coronene dimers. Also, the substituted coronene dimers are stabilized by as high as 115 times than those of unsubstituted coronene dimers.