Naphthalene Diimide-Based Soft Materials Exhibiting High-Performance, Tunable Electrical Properties Through Side-Chain Engineering and Strong Binding Interactions with Human Hemoglobin.

Abstract

Herein the design and synthesis of naphthalene diimide (NDI) derivatives aminated at the core with N1,N1-dimethylpropane-1,3-diamine, and 6-aminocoumarin are reported. Accommodating amine substituents on the electron-poor NDI scaffold yielded notable electronic characteristics of interest. These aminated NDIs exhibited two distinct absorption bands: one at a high-energy band (350-450 nm) associated with π-π* transitions and the other one (450-600 nm) due to intramolecular charge transfer absorption. The obtained bandgaps, ranging from 2.69 to 3.34 eV depending on side-chain modifications, demonstrated tunability, indicating varied semiconducting properties. Electrical studies revealed that all the side-chain-modified molecules exhibited high electrical conductivity and displayed characteristics of Schottky diodes. Notably, different Schottky parameters are found to vary systematically based on side-chain engineering, aligning well with their optical characteristics. Complementarily, AFM, and XRR investigations revealed unique crystalline morphologies associated with molecular architecture, highlighting the efficacy of molecular engineering in optimizing materials for electrical devices. Selective compounds underwent a series of biophysical analyses, including UV-vis absorption-, fluorescence-, and circular dichroism spectroscopy, all of which demonstrated a strong binding affinity, highlighting their potential interactions with human hemoglobin (Hb). In-depth computational studies like TDDFT and frontier molecular orbital analysis cemented the experimental observations.