Solvent-assisted investigation of NLO responses of 3,5-dihydroxybenzoic acid and pyrazine-2-carboxamide cocrystal

Abstract

In recent years, there has been a growing interest in cocrystals as potential materials for nonlinear optical (NLO) applications due to their enhanced optical properties compared to their individual components. Understanding the influence of solvent interactions on the NLO responses of cocrystals is crucial for the development of efficient optoelectronic devices. In this study, we investigate the solvent-assisted fast-switching behavior and the enhanced NLO responses of a cocrystal formed by 3,5-dihydroxybenzoic acid and pyrazine-2-carboxamide. The NLO responses vary across solvents, with linear polarizability < α₀ > ranging from 4.36 electrostatic units (esu) in methanol to 11.98 in chloroform, and first hyperpolarizability (β₀) from 0.21 esu in methanol to 7.44 esu in chloroform. The second hyperpolarizability γ_tot values range from 1.21 esu in toluene, dichloromethane (DCM), and methanol to 2.34 esu in the gaseous phase. Our research aims to elucidate the influence of solvent interactions on the NLO properties of this cocrystal, providing insights for potential applications in optoelectronic devices. We found that the cocrystal produced the steeper NLO response upon changing the solvent polarity. The comparison of the values in different solvents shows that chloroform has the highest < α₀ > β₀ values, indicating a strong response to the applied electric field. Meanwhile, methanol has the lowest < α₀ > and β₀ values, indicating a weaker response. The γ_tot values for all solvents are relatively close, with the gaseous phase having the highest value at 2.34 and chloroform having the lowest value at 1.37.