Structural Modulation from 1D Chain to 3D Framework: Improved Thermostability, Insensitivity, and Energies of Two Nitrogen-Rich Energetic Coordination Polymers

Abstract

Two new energetic coordination polymers (CPs) [Pb(BT)(HO)] (1) and [Pb(DOBT)(HO)]·(4HO) (2) with 1D and 3D structures were synthesized by employing two rational designed ligands, 1H,1'H-5,5'-bitetrazole (HBT) and 1H,1'H-[5,5'-bitetrazole]-1,1'-diol ligands (DHBT), respectively. Thermal analyses and sensitivity tests show that the 3D architecture reinforces the network of 2 which has higher thermal stability and lower sensitivity than that of 1. Through oxygen-bomb combustion calorimetry the molar enthalpy of formation of 2 is derived to be much higher than that of 1 as well as the reported CPs. Herein, more importantly, the heats of detonation (ΔH) were calculated according to the decomposition products of TG-DSC-MS-FTIR simultaneous analyses for the first time. The calculated results show that ΔH of 2 is 23% higher than that of 1. This research demonstrates that 3D energetic CP with outstanding energetic properties can be obtained through efficient and reasonable design.

Coordination Polymerization of Metal Azides and Powerful Nitrogen-Rich Ligand toward Primary Explosives with Excellent Energetic Performances

“…However, as an emerging field, enormous challenges remain in the interpretation of relationships between structure and energetic performance. ,, Thus, rules for the rational design of EMs should be established. Most reported ECPs can function as the secondary explosives because of their low sensitivities. − Importing an energetic heterocycle ligand to extremely sensitive transition-metal azides by coordination polymerization can be used to effectively construct π-stacked coordination polymers. These polymers serve as a new class of primary explosives with enhanced energetic performance and reduction of mechanical sensitivities.…”

Fine-Tuning the Energetic Properties of Complexes through Ligand Modification

“…In contrast, employing this method to tune the properties of energetic complexes and energetic metal−organic frameworks has scarcely been reported. 28 Energetic complexes are an important class of energetic materials, which possess high densities and high thermal stabilities. These materials have exhibited promising applications as pyrotechnics and primary explosives 29−38 and have been constructed exclusively with strong coordination bonds between nitrogen-rich ligands and metal ions.…”

“…Modulation of properties (e.g., density, thermal stability, sensitivity, heat of detonation, detonation velocity, and detonation pressure) of energetic materials have attracted growing attention not only for gaining insight into the correlation between the structure and properties but also for various applications such as explosives, − propellants, − pyrotechnics, − carbon nitride precursors and their energetic analogues, − and gas-generating agents. , For example, gas-generating agents should ideally produce more gas and less heat when they are used for air bags and primary explosives should be sensitive enough to be initiated, whereas secondary explosives should possess considerably higher detonation heat and lower sensitivities. Over the past decade, a variety of protocols for tuning the properties of energetic materials have been developed. − Among them, the introduction of different energetic groups (e.g., nitro, − nitroamine, , azido, and amino) as substituents on an organic backbone is perhaps the most commonly used method for this purpose.…”

“…To date, this method is primarily used for energetic organic molecules or energetic salts. In contrast, employing this method to tune the properties of energetic complexes and energetic metal–organic frameworks has scarcely been reported …”

Synthesis and Properties of [Ba(CHZ)(BT)(H2O)2]n as a New Energetic Coordination Compound

“…Additionally, Klein's group studied the 5,5′‐bistetrazolate complexes with La 3+ , Ce 3+ , Nd 4+ , Sm 4+ , Eu 4+ , Tb 6+ , Er 6+ , and Th 4+ as central ions in 2007 and 2009,, whereas Nechaev's group reported its complexes with Pr 4+ , Gd 4+ , Y 6+ , Dy 6+ , Ho 6+ , Tm 6+ , Yb 6+ , and Lu 6+ as metal ions in 2018 . Besides, some transition metal complexes were also fully studied …”