# The Chemical Space of B, N-substituted Polycyclic Aromatic Hydrocarbons: Combinatorial Enumeration and High-Throughput First-Principles Modeling

## TL;DR

This study exhaustively enumerates and models a vast chemical space of B, N-substituted polycyclic aromatic hydrocarbons, revealing potential photovoltaic applications through high-throughput first-principles calculations and trend analysis.

## Contribution

It provides the first comprehensive enumeration and characterization of over 7.4 trillion B, N-substituted polycyclic hydrocarbons, combined with high-throughput DFT calculations for a subset of 33,000 molecules.

## Key findings

- Identified a large fraction of molecules active in the solar spectrum range.
- Discovered trends in structural stability and electronic properties.
- Analyzed symmetry-controlled selectivity in synthesis yields.

## Abstract

Combinatorial introduction of heteroatoms in the two-dimensional framework of aromatic hydrocarbons opens up possibilities to design compound libraries exhibiting desirable photovoltaic and photochemical properties. Exhaustive enumeration and first-principles characterization of this chemical space provide indispensable insights for rational compound design strategies. Here, for the smallest seventy-seven Kekulean-benzenoid polycyclic systems, we reveal combinatorial substitution of C atom pairs with the isosteric and isoelectronic B, N pairs to result in 7,453,041,547,842 (7.4 tera) unique molecules. We present comprehensive frequency distributions of this chemical space, analyze trends and discuss a symmetry-controlled selectivity manifestable in synthesis product-yield. Furthermore, by performing high-throughput ab initio density functional theory calculations of over thirty-three thousand (33k) representative molecules, we discuss quantitative trends in the structural stability and inter-property relationships across heteroarenes. Our results indicate a significant fraction of the 33k molecules to be electronically active in the 1.5-2.5 eV region, encompassing the most intense region of the solar spectrum, indicating their suitability as potential light-harvesting molecular components in photo-catalyzed solar cells.