Computational Screening of Organic Semiconductors: Exploring Side-Group Functionalisation and Assembly to Optimise Charge Transport in Chiral Molecules

Abstract

<p>Molecular materials are challenging to design as their packing arrangement and hence properties are subject to subtle variations in the interplay of soft intermolecular interactions that are difficult to predict. The rational design of new molecular materials with tailored properties is currently hampered by the lack of knowledge of how a candidate molecule will pack in space and how we can control the polymorphs we can experimentally obtain. Here, we develop a simplified approach to aid the material design process, by the development of a screening process that is used to test 1344 helicene molecules that have potential as organic electronic materials. Our approach bridges the gap between single molecule design, molecular assembly, and the resulting charge-carrier mobilities. We find that fluorination significantly improves electron transport in the molecular material by up to 200%; the reference [6]helicene packing showed a mobility of 0.30 cm2 V-1 s-1, fluorination increased the mobility to up to 0.96 and 0.97 (13-fluoro[6]H and 4,13-difluoro[6]H), assuming an outer reorganisation energy of 0.30 eV. Side groups containing triple bonds largely lead to improved transfer integrals. We validate our screening approach through the use of crystal structure prediction to confirm the presence of favourable packing motifs to maximize charge mobility.</p>

hcga: Highly Comparative Graph Analysis for network phenotyping

“…Helicenes are graphene-type spiral molecules with promising optical and electronic applications due to their axial chirality [34]. We use a recently curated data set composed of 1344 helicene dimers (i.e., pairs of helicenes in the same translational-motif orientation) [6], see Figure 2B(i). For each helicene dimer, we create a simple molecular graph representing atoms and their van der Waals interactions: an edge is present if the separation between two atoms is lower than the sum of their Van der Waals radii (plus a buffer of 2Å), and the edge weight is given by the inverse distance (more details are given in STAR Methods A.2.4).…”

“…The organic semiconductors (helicenes) data set was taken from a recent computational screening for high charge-carrier mobility study [6]. In the original study, a total of 1344 potential [6]helicene molecules were screened for their suitability as potential organic semiconductors. Here, we focus on the electronic transfer integral J (J-coupling).…”

“…This integral is strongly dependent upon the frontier orbitals of molecules and the spatial arrangement and orientation of molecules A and B, and its prediction in new molecules is currently an open challenge. For further details on the data set, see [6].…”

“…Across many scientific disciplines there are increasing volumes of data that are naturally described as graphs (or networks) and can leverage the extensive results in graph theory to solve research problems. Among many others, examples include linking the structural motifs of proteins and their function [2,3,4], aiding the diagnosis of diseases using fMRI data [5], understanding structural properties of organic crystal structures for electron transport [6], or modelling network flows, e.g., city traffic [7], information (or misinformation) spread in a social network [8,9], or topic affinity in a citation network [10]. The growing importance of such network data has driven the development of a multitude of methods for investigating and revealing relevant topological, combinatorial, statistical and spectral properties of graphs, e.g., node centralities [11,12], assortativity [13,14], path-based properties [15], graph distance measures [16,17], connectivity [18], or community detection [19,20], to name but a few in the highly interdisciplinary area of network science.…”

Elucidation of Diverse Solid‐State Packing in a Family of Electron‐Deficient Expanded Helicenes via Microcrystal Electron Diffraction (MicroED)**

“…[5] The low symmetry and diverse geometries of chiral molecules have profound implications for the properties of their aggregates,b ut the complexities of such structures severely complicate efforts toward rational design. [6] As the prototypical chiral aromatic molecules,heliceneshelical arrays of fused aromatic rings-have been at the forefront of efforts to exploit chirality in organic (opto)electronic applications. [1d-f] Thes tructural diversity of these compounds has recently grown at ar apid rate,w ith ap articular surge of structures containing multiple helicenes embedded into larger polyaromatic frameworks.…”