Theoretical Study of the Stacking Behavior of Selected Polycondensed Aromatic Hydrocarbons with Various Symmetries

Abstract

Stacked dimers of four polycondensed aromatic hydrocarbons, with structures varying from high to reduced symmetries, have been calculated with dispersion-corrected density functional theory. The configurations of the stacked dimers are readily classified by two in-plane displacements and a relative rotation. The potential energy surface in these three coordinates was calculated with rigid monomers and appears to be slightly flat. Full geometry optimization was performed for selected low-energy structures, resulting in an energy ranking of a series of conformations whose geometries were characterized in considerable detail. The dissociation energy values reveal a clear preference for the symmetrical disk-shaped and triangular structures to dimerize into two in-plane-displaced arrangements, whereas the less symmetrical trapezoidal structures show a tendency to stack in displaced antiparallel over parallel arrangements. According to methodical checks, the key computational results, namely, the shape of the potential energy surface and the geometrical structures and energy ranking of dimer conformations, are essentially insensitive to computational assumptions such as the atomic orbital basis set and density functional chosen. This is shown in particular for the basis set superposition error, which, for the selected level of theory [B97-D3(BJ)/ TZV(d,p)] was estimated by the counterpoise correction procedure to be in the narrow range between 7% and 8% of the uncorrected dissociation energies. ■ INTRODUCTIONThe significant stability and unrivaled noncovalent π−π stacking 1 bonding that confer self-assembled polycondensed aromatic hydrocarbons (PAHs) with superior physicochemical 2a−g and optoelectronic 3a−k properties have drawn considerable attention in the past two decades. To simplify their synthesis, experimental efforts have focused on making highly symmetrical PAHs with structures ranging from linear to diskshaped. 4a−i Nevertheless, the high symmetry of these structures complicates their uneven decoration with lateral groups (i.e., solubilizing aliphatic chains). A more convenient approach is to synthesize multisubstituted PAHs with analogous lateral groups, which hinders the stacking of the aromatic core by reducing the desired π−π noncovalent bonding. 5a,b We are interested in exploring the π−π stacking of PAH structures whose reduced symmetry allows a disproportionate decoration with lateral groups. Among others, the half-lunar tribenzo[fg,ij,rst]pentaphene (1, TBP; Figure 1 with R = H) is believed to be a potential candidate. Derivatives of this compound substituted by a wide variety of pending groups have been explored as materials for optoelectronic devices. 6a,b Furthermore, a TBP derivative substituted in all six positions by alkyl chains has also been reported but was not further investigated. 7 To minimize steric hindrance that reduces π−π stacking, we recently reported a versatile synthesis of TBP derivatives bearing pairs of alkyl side chains at the specific positions R 1 , R 2 , and R ...

High Stability and Properties of Adsorbed Polycyclic Aromatic Hydrocarbons (PAHs) onto Phosphorene: An atomistic DFT study

“…1a), which is in excellent agreement with the experimental reference (Ecoh525 meV/atom) [1]. meV/atom (force field, MMFF) [43][44][45]. In addition, the computed adsorption energies of benzene, naphthalene, coronene, and ovalene onto graphene are in excellent agreement with those from Redhead analyses (Table 1 in parenthesis) [1].…”

Impact of Systematic Structural Variation on the Energetics of π–π Stacking Interactions and Associated Computed Charge Transfer Integrals of Crystalline Diketopyrrolopyrroles

“…In effect, the XBDPP dimers in Figure 1C co-facial π-π dimer systems has been the focus of considerable attention in recent years 39,44,[47][48][49][50] and the often quoted π-π donor acceptor interaction description 51 has been shown to be inadequate 39,44 at least in simple benzene based π-π dimer systems. Instead, it would appear that co-facial π-π stacks are primarily stabilized by local bond dipole/bond dipole and bond dipole induced interactions leading to slipped co-facial monomers with greater dimer stability than eclipsed.…”

High Stability and Properties of Adsorbed Polycyclic Aromatic Hydrocarbons (PAHs) onto Phosphorene: An atomistic DFT study

“…For reference purposes, we computed the interlayer cohesive energy of graphite (Ecoh), where the total adsorption energies of PAHs onto graphene (Eads, meV/atom (force field, MMFF) [43][44][45]. In addition, the computed adsorption energies of benzene, naphthalene, coronene, and ovalene onto graphene are in excellent agreement with those from Redhead analyses (Table 1 in parenthesis) [1].…”