Molecular Orbital Tuning of Pentacene-Based Organic Semiconductors through N-Ethynylation of Dihydrodiazapentacene

Abstract

This study explores the concept of molecular orbital tuning for organic semiconductors through the use of N,N′-diethynylated derivatives of 6,13-dihydro-6,13-diazapentacene (2a and 2b). These novel molecules maintain the same molecular geometry and π–π stacking as their parent pentacene derivatives (1a and 1b), as confirmed by X-ray crystallography. However, they exhibit altered frontier molecular orbitals in terms of the phase, nodal properties, and energy levels. Theoretical calculations based on crystal structures indicate that 2a and 2b could significantly enhance the hole mobilities of the parent compounds by improving the hole transfer integral. Organic field-effect transistors (OFETs) of 1a and 2a were fabricated by using dip-coating and bar-coating methods. Both types of devices for 2a demonstrated a hole mobility exceeding 1 cm2 V–1 s–1, more than twice that of the respective devices for 1a. Additionally, unlike its pentacene parent, 2a is transparent to visible light and exhibits significantly enhanced environmental stability against light and air, making it a promising candidate for broader applications in organic electronic devices.