Regulation of Dimensionality and Energetic Performance in Silver(I) Coordination Polymers via Steric Effects of Heteroatoms

Abstract

Energetic coordination compounds (ECCs) offer a new paradigm for designing high-energy and high-safety energetic materials by integrating the catalytic activity of metal centers with the structural tunability of ligands. Inspired by the regulation of coordination modes through electronic effects, oxazole-2-carbohydrazide (OZ-2-CA) and thiazole-2-carbohydrazide (SZ-2-CA) were selected as ligands in this study to synthesize two novel ECCs, [Ag(OZ-2-CA)ClO4]n (ECC-1) and Ag2(SZ-2-CA)2(ClO4)2 (ECC-2) through self-assembly. Single-crystal X-ray diffraction revealed that the planarity of the ligand framework dictates the differentiation in coordination dimensionality. The rigid OZ-2-CA enables the formation of a one-dimensional helical chain structure in ECC-1, whereas the twisted SZ-2-CA constrains ECC-2 to a zero-dimensional discrete dimer. By combining theoretical calculations and experimental characterization, the structure−property relationship between ligand geometry, caused by heteroatom size, and crystal packing as well as macroscopic performance was elucidated. Benefiting from a higher density (2.475 g cm−3) and favorable oxygen balance (−21.53%), ECC-1 exhibits outstanding detonation performance (D = 6.24 km s−1, P = 22.26 GPa) and moderate mechanical sensitivity (IS = 4.2 J). In contrast, ECC-2 shows considerably reduced performance due to a more negative enthalpy of formation (−504.0 kJ·mol−1) and poorer oxygen balance, attributed to the introduction of sulfur atoms.