Synthesis and Photophysical Properties of Novel 1H-Indazole-3-carbohydrazides: Computational and Crystallographic Insights

Abstract A diverse series of novel indazole derivatives were successfully synthesized via acid–amine coupling reactions with various carboxylic acids. Their chemical structures were comprehensively validated using advanced spectroscopic techniques, including 1H, 13C, and DEPT-135 NMR, FT-IR, and HRMS analyses. Single-crystal X-ray diffraction data for representative compounds, combined with detailed Hirshfeld surface analysis, effectively mapped critical intermolecular interactions within crystal packing. Additionally, density functional theory (DFT) calculations elucidated the theoretical spectral profiles, frontier molecular orbital energy gaps, and electron density distributions. This integrated experimental and computational dataset establishes a highly robust foundation for future advanced structural and functional investigations of these systems.