Solubility of Organic Photoelectric Material Intermediate 9,9-Dimethylfluorene in 15 Single Solvents: Solvent Effect Analysis, Molecular Simulation, and Model Correlation

9,9-Dimethylfluorene is a core intermediate underpinning the development of modern organic electroluminescent (OLED) display technology. Its unique molecular structure and physicochemical properties make it a key basic raw material for the synthesis of OLED materials. These materials are widely applied in mainstream display devices such as smartphones and televisions. Therefore, the dissolution behavior of 9,9-dimethylfluorene in individual solvents holds certain research value. The solubility of 9,9-dimethylfluorene was measured using a static gravimetric method. The measurements were conducted in 15 individual solvents, which encompass ethanol, n-butanol, methanol, iso-propanol, iso-butanol, iso-pentanol, acetone, n-pentanol, acetonitrile, 2-butanone, n-propanol, methyl acetate, sec-butanol, propyl acetate, and ethyl acetate. The solubility increased with temperature in all 15 solvents. At 298.15 K, it was the lowest in methanol (0.009091 mol/mol) and the highest in 2-butanone (0.2575 mol/mol). A comprehensive analysis of cohesive energy density, hydrogen bonding, polarity, and Hansen solubility parameters was conducted. Dispersion forces were revealed to be the key factors governing the dissolution behavior of the substance. Additionally, among the four model fittings, the Apelblat model exhibited the highest degree of fitting. Molecular simulations were employed to systematically elucidate the internal interactions within 9,9-dimethylfluorene. The simulations included the analysis of molecular electrostatic potential (MEP) surfaces and the calculation of interaction energies.