Polarity-Induced Morphological Transformation with Tunable Optical Output of Terpyridine-Phenanthro[9,10-]imidazole-Based Ligand and Its Zn(II) Complexes with - Characteristics.

Self-assembled nanostructures obtained from various functional π-conjugated organic molecules have been able to draw substantial interest due to their inherent optical properties, which are imperative for developing optoelectronic devices, multiple-color-emitting devices with color-tunable displays, and optical sensors. These π-conjugated molecules have proven their potential employment in various organic electronic applications. Therefore, the stimuli-responsive fabrication of these π-conjugated systems into a well-ordered assembly is extremely crucial to tuning their inherent optical properties for improved performance in organic electronic applications. To this end, herein, we have designed and synthesized a functional π-conjugated molecule () having phenanthro[9,10-]imidazole with terpyridine substitution at the 2 position and its corresponding metal complexes ( and ). By varying the polarity of the self-assembly medium, , , and are fabricated into well-ordered superstructures with morphological individualities. However, this medium polarity-induced self-assembly can tune the inherent optical properties of , , and and generate multiple fluorescence colors. Particularly, this property makes them useful for organic electronic applications, which require adjustable luminescence output. More importantly, in 10% aqueous-THF medium, exhibited H-type aggregation-induced white light emission and behaved as a single-component white light emitter. The experimentally obtained results of the solvent polarity-induced variation in optical properties as well as self-assembly patterns were further confirmed by theoretical investigation using density functional theory calculations. Furthermore, we investigated the - characteristics, both vertical and horizontal, using ITO and glass surfaces coated with , , and , respectively, and displayed maximum current density for the -coated surface with the order of measured current density > > . This observed order of current density measurements was also supported by a direct band gap calculation associated with the frontier molecular orbitals using the Tauc plot. Hence, solvent polarity-induced self-assembly behavior with adjustable luminescence output and superior - characteristics of make it an exceptional candidate for organic electronic applications and electronic device fabrication.