Conclusion
In this work, we investigated the crystal structure, electronic structure and charge transport properties of two pyrazole derivatives through density functional theory and interpreted via Marcus Electron Theory. The optimized geometry structures, reorganization energy, absorption spectra, frontier orbitals, ionization potential (IP) and electronic affinity (EA) of both compounds were calculated to perform the relationship between the structure and property taking their crystal geometry, noncovalent interactions and aggregation modes in solid phase into account. According to SCXRD results the molecule AB1 andAB2 aggregate J type and antiparallel H type stacking modes in their solid phases which are favourable stacking modes to obtain high charge transfer rate due to high transfer integral. The incorporation of the NO2 group to the molecule skeleton result in different crystal structure and packing arrangement therefore different charge transport property in terms of their reorganization energy. The hole reorganization energies of the both molecules are smaller than that of electron indicating that they can be used as p -type semiconductors. Since AB2 exhibits lower hole reogranization energy than that of AB1 , the charge transfer rate can be predicted high for AB2 . In terms of its crystallographic data, it aggregates in strong antiparallel H type \(\pi\cdots\pi\) stacking type with the small perpendicular distance between the adjacent rings. Therefore, this result consolidated that the molecule AB2 can have high charge transport rate when it is used as an optoelectronic device. In addition, low-lying HOMOs, and high IPs of the AB2indicate the its better redox stability than AB1 . Although this is case, beside the AB2, AB1 shows prefferred stacking mode in solid phase and low reorganization energy which is benefical for device application. 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.