Prediction of the Charge Transport and Electronic Properties of Two Pyrazole Derivatives in terms of Their Solid Molecular Arrangements and Reorganization Energy: The Effects of Nitro Groups on Structure-Property Relationship

Abstract

Pyrazole derivatives have noteworthy attention in optoelectronic field since they demonstrate distinctive properties in semiconducting devices such as organic light emitting diodes (OLEDs), nonlinear optical (NLO) and solar cells. organic field effect transistors (OFETs). Therefore, to establish the relationship between the structure and property of the molecules, we explored influence of nitro groups on the 3D molecular structures, reorganization energy, absorption spectra, frontier orbitals, ionization potential (IP), electronic affinity (EA), intra-molecular charge transfer (ICT) and charge transport behaviour of the two π-conjugated pyrazole compunds through single crystal x-ray crystallographic and quantum chemical calculations by considering Marcus Electron Transfer Theory and Density Functional Theory. Our experimental and theoretical results predicted that incorporation of the nitro groups to the molecule skeleton increased the rigidity of the conjugated system and improve the efficient charge injection in electronic devices by lowering the hole (λ_h) and electron (λ_e) reorganization energy from 0.48eV to 0.34 eV, 0.44 eV to 0.26 eV, respectively which can be effective way to design molecules with desired electronic properties via smart chemical structural modification. In addition, both molecules aggregate with the close preferred π⋯π stacking interactions (J and antiparallel H type) and multiple intermolecular interactions in their solid phases. Accordingly, both molecules are suggested to be quite suitable for p-type semiconducting materials with small reorganization energy and preferred stacking modes in solid phase. In addition, this study paves the way for the design and synthesis of new conjugated pyrazole molecules for high device performance.