Synthesis and characterization of octa(aminophenyl) silsesquioxane through amination of octa(nitrophenyl) silsesquioxane using B2(OH)4 at room temperature

Abstract

Octa(aminophenyl) silsesquioxane (OAPS), a promising polyhedral oligomeric silsesquioxane (POSS) derivative, exhibits exceptional structural and functional properties, making it highly suitable for advanced material applications. In this study, we developed an efficient and sustainable synthesis method for OAPS, utilizing tetrahydroxydiboron [B₂(OH)₄] as a reducing agent and 4,4′-bipyridine as a catalytic mediator. This strategy streamlines the synthetic procedure through a metal-free approach, operating under mild conditions while achieving high yields and demonstrating exceptional process stability. Initially, octa(nitrophenyl) silsesquioxane (ONPS) was synthesized as the precursor. Through a comprehensive investigation and evaluation of different reducing agents, catalysts, and their quantities, a novel reduction strategy was developed, enabling the complete and efficient conversion of nitro groups to amino groups. The obtained OAPS was characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR), while matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) confirmed its high purity and structural integrity through molecular weight analysis. A proposed mechanistic pathway for the reduction process, facilitated by the synergistic action of B₂(OH)₄ and 4,4′-bipyridine, is also proposed. The synthesized OAPS demonstrated remarkable thermal stability, with an initial decomposition temperature of 430.2 °C under nitrogen and 399.3 °C under air, highlighting its excellent performance. This study introduces a scalable and efficient method for OAPS synthesis, with significant potential for industrial applications in advanced materials and nanotechnology.