From Pyridine Adduct of Borabenzene to (In)finite Graphene Architectures Functionalized with N → B Dative Bonds. Prototype Systems of Strong One- and Two-Photon Quantum Transitions Triggering Large Nonlinear Optical Responses

The synthesis and optoelectronics properties of polyaromatic hydrocarbons (PAHs) doped with boron and nitrogen units (BN) monopolize the interest of increasing numbers of researchers the past few years. The key concept fueling these attempts lies on the prospect of engineering novel organic compounds of versatile physical and chemical properties using well-known all-carbon systems as scaffolds. Among the various BN-doped PAHs synthesized so far, one could distinguish two categories. The most common one comprises systems in which BN units replace aromatic CC bonds. The second one, which this study deals with, refers to systems wherein the BN unit replaces intercyclic CC bonds linking two independent aromatic sextets within the framework of a given PAH. In this work, starting from a reference molecule belonging to the latter category, namely, the pyridine-adduct of borazine, we open the subject of PAHs doped with intercyclic boron nitrogen bonds. Our results, based on state-of-the-art ab initio and density functional theory wavefunction methods, suggest that intercyclic BN bonds, referred in the literature as “N → B dative bonds”, if successfully incorporated to (in)­finite polyaromatic sections, may alter the optical absorption profiles of the parental systems in a greater extent than typical BN aromatic units. Specifically, we predict and comprehensively interpret the capacity of N → B dative bonds to switch-on extra-strong one- and two-photon quantum transitions followed by intense transfer of charge. The strong excited-states alternation triggered by the presence of N → B dative bonds may unleash exceptionally high nonlinear optical responses and could find a proper ground in organic optoelectronic technologies.