Real-Time Spectroscopic and Microscopic Investigations of Solid-State Reaction of Schiff Bases and Their Optical-Waveguiding Properties

The real-time investigation of single-crystal-to-single-crystal (SC–SC) transformations can provide crucial insights into the reaction mechanisms and material evolution. This report demonstrates the in situ spectroscopic and microscopic monitoring of the Schiff base reaction under aging conditions. UV–vis, Fourier transform infrared, fluorescence, and Raman spectroscopies collectively reveal dynamic chemical and structural modifications occurring at the macroscopic and microscopic scales. Notably, real-time optical imaging captures the SC–SC reaction, enabling a direct visualization of the reaction pathway. The resulting Schiff bases exhibit bright luminescence, which is harnessed for active optical-waveguiding applications. Self-assembled branched homostructures demonstrate multi-input/output optical-waveguiding behavior, expanding the potential of such materials in integrated photonic circuits. This work presents an ecofriendly, solvent-free approach for designing functional organic materials with tunable optical properties.