title: Herringbone Pattern and CH-π Bonding in the Crystal Architecture of Linear Polycyclic Aromatic Hydrocarbons.
abstract: The herringbone pattern is a pervasive structural motive found in most molecular crystals involving aromatic compounds. A plot of the experimental sublimation enthalpies of members of increasing size of the acene, phenacene and p-phenyl families versus the number of carbons uncovers a linear relationship between the two magnitudes, suggesting a major role of CH-π bonding. In this work we undertake the task of evaluating the relevance of the edge-to-face interaction (or CH-π bond) in the overall reticular energy of the crystal, to quantitatively assess the importance of this structural element. Following a heuristic approach, we considered the series of acenes, phenacenes and p-phenyls and analyzed the edge-to-face interaction between the molecules as they occur in the experimental crystal network. Isolation of the relevant molecular dimers allows to incorporate some of the most sophisticated tools of quantum chemistry and get a reliable picture of the isolated bond. When compared to the experimental sublimation energy, our results are conclusive: this sole interaction is the largest contribution to the lattice energy, and definitively dictates the crystal architecture in all the studied cases. Elusive enough, the edge-to-face interaction is mainly dominated by correlation interactions, specifically in the form of dispersion and, to a less extent, of charge-transfer terms. A suggestive picture of the bond has been obtained by displaying the differences in local electron densities calculated by either correlated or non-correlated methods.
authors.affiliation: Departamento de Química Orgánica and Instituto Universitario de Síntesis Orgánica, Unidad Asociada del CSIC, Universidad de Alicante, San Vicente del Raspeig, 03690, Alicante, Spain.
authors.forename: Albert
authors.identifier: http://orcid.org/0000-0001-9196-8436
authors.initials: A
authors.lastname: Guijarro
authors.affiliation: Departamento de Teoría y Simulación de Materiales, Instituto de Ciencia de Materiales de Madrid (CSIC), Cantoblanco, 28049, Madrid, Spain.|Unidad Asociada del CSIC and Instituto Universitario de Materiales, Universidad de Alicante, San Vicente del Raspeig, 03690, Alicante, Spain.
authors.forename: José A
authors.identifier: http://orcid.org/0000-0002-2937-4802
authors.initials: JA
authors.lastname: Vergés
authors.affiliation: Unidad Asociada del CSIC and Instituto Universitario de Materiales, Universidad de Alicante, San Vicente del Raspeig, 03690, Alicante, Spain.|Departamento de Química Física, Universidad de Alicante, San Vicente del Raspeig, 03690, Alicante, Spain.
authors.forename: Emilio
authors.identifier: http://orcid.org/0000-0001-7688-4840
authors.initials: E
authors.lastname: San-Fabián
authors.affiliation: Unidad Asociada del CSIC and Instituto Universitario de Materiales, Universidad de Alicante, San Vicente del Raspeig, 03690, Alicante, Spain.|Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, 03690, Alicante, Spain.
authors.forename: Guillermo
authors.identifier: http://orcid.org/0000-0001-8077-1873
authors.initials: G
authors.lastname: Chiappe
authors.affiliation: Unidad Asociada del CSIC and Instituto Universitario de Materiales, Universidad de Alicante, San Vicente del Raspeig, 03690, Alicante, Spain.|Departamento de Física Aplicada, Universidad de Alicante, San Vicente del Raspeig, 03690, Alicante, Spain.
authors.forename: Enrique
authors.identifier: http://orcid.org/0000-0001-8631-0189
authors.initials: E
authors.lastname: Louis
keywords: CH-π bonding; aromatic hydrocarbons; herringbone pattern; molecular crystals; sublimation enthalpies