Controlling the Energetic Properties of N-Methylene-C-Linked 4-Hydroxy-3,5-dinitropyrazole- and Tetrazole-Based Compounds via a Selective Mono- and Dicationic Salt Formation Strategy.

In the quest to synthesize high-performing insensitive high-energy density materials (HEDMs), the main challenge is establishing an equilibrium between energy and stability. For this purpose, we explored 4-hydroxy-3,5-dinitropyrazole- and tetrazole-based energetic scaffolds connected via a N-methylene-C bridge. The hydroxy functionality between nitro groups on the pyrazole ring promotes physical stability via inter- and intramolecular hydrogen bonding and contributes to oxygen balance, supporting better energetic performance. Due to two acidic sites (OH and NH) with different reactivities, a series of monocationic and dicationic salts were synthesized, and their overall performance was compared. All compounds synthesized in this study have high physical stability with impact sensitivity >40 J and friction sensitivity >360 N. Monocationic salts were generally found to have better thermal stability with respect to their corresponding dicationic energetic salts, which showed better energetic performance. The salt formation strategy effectively improved the thermal stability of 2 (Td = 168 °C), where most energetic salts have decomposition temperatures higher than 220 °C. All of the compounds were characterized through IR, multinuclear NMR spectroscopy, high-resolution mass spectrometry (HRMS), and elemental analysis. The structure-property relationship was studied using Hirshfeld surface analysis, noncovalent interaction (NCI) analysis, and electrostatic potential studies.

Polynitro-functionalized 4-phenyl-1H-pyrazoles as heat-resistant explosives.

A new class of heat-resistant explosives was synthesized by coupling N-methyl-3,5-dinitropyrazole with polynitrobenzene moieties through carbon-carbon bonds. Simple Pd(0)-based Suzuki cross-coupling reactions between N-methyl-4-bromo-3,5-dinitropyrazole and 4-chloro/3-hydroxy-phenylboronic acid followed by nitration, amination and oxidation lead to the formation of C-C connected penta-nitro energetic derivatives 6 and 10. Various other energetic derivatives, such as amino (5), azido (7), nitramino (8) and energetic salts (11-14), were also explored to fine-tune their properties. All the compounds were thoroughly characterized using IR, NMR [1H, 13C{1H}], differential scanning calorimetry (DSC), elemental analysis, and HRMS studies. Compounds 5, 10 and 13 were further characterized through 15N NMR, and the crystal structures of 6 and 14 were confirmed through single-crystal X-ray diffraction studies. The physicochemical and energetic properties of all the energetic compounds were explored. Most of the synthesized compounds demonstrated high thermal stability (decomposition temperature Tdec > 250 °C), among which compounds 5 and 6 showed excellent thermal stability, having decomposition temperatures above 300 °C. The excellent thermal stability, acceptable sensitivity and good energetic properties of compounds 5, 6, 10 and 13 make them promising heat-resistant explosives. Furthermore, these compounds were found to be more thermally stable than the known N-methyl-3,5-dinitropyrazole-based and C-N coupled 3,4,5-trinitrobenzene-azole-based energetic compounds.

Prosthetic Management of Flap-Related Complications Following Glossectomy in Locally Advanced Tongue Cancer.

Total glossectomy defects resulting from postoncologic resection are commonly reconstructed with locoregional or free flaps. However, effectively managing complications that may arise after reconstruction can be a significant challenge. We present a unique case series describing prosthetic management of flap-related complications following glossectomy in patients treated for locally advanced tongue cancer. Three patients underwent total glossectomy, neck dissection, reconstruction using free flap, and tracheostomy. Two patients developed an intraoral fistula located in the anterior region of the floor of the mouth. The third patient developed a flap failure requiring a second procedure using a pectoralis major myocutaneous flap for correction of the orocutaneous fistula that ultimately did not heal. Mandibular obturator prostheses lined with a soft liner were fabricated for all the patients, which helped reduce salivary incontinence and improve swallowing and speech. This case series highlights that a collaborative interdisciplinary team approach is crucial for optimizing postoperative function and outcomes when managing complications from reconstructive procedures.

Zwitterionic Energetic Materials: Synthesis, Structural Diversity and Energetic Properties.

Zwitterionic compounds are an emergent class of energetic materials and have gained synthetic interest of many in the recent years. Due to their better packing efficiencies and strong inter/intramolecular electrostatic interactions, they often ensue superior energetic properties than their salt analogues. A systematic review from the perspective of design, synthesis, and physicochemical properties evaluation of the zwitterionic energetic materials is presented. Depending on the parent ring(s) used for the synthesis and the type of moieties bearing positive and negative charges, different classes of energetic materials, such as primary explosives, secondary explosives, heat resistant explosives, oxidizers, etc., may result. The properties of some of the energetic zwitterionic compounds are also compared with analogous energetic salts. This review will encourage readers to explore the possibility of designing new zwitterionic energetic materials.

Pushing the Limit of Oxygen Balance on a Benzofuroxan Framework: K2DNDP as an Extremely Dense and Thermally Stable Material as a Substitute for Lead Azide.

Because of environmental and health impacts, there is an ongoing necessity to develop sustainable primary explosives to replace existing lead-based analogues. Now we describe a potential primary explosive, dipotassium 4,6-dinitro-5,7-dioxidobenzo[c][1,2,5]oxadiazole 1-oxide (K2DNDP), which exhibits an excellent thermal stability (Tdec = 281 °C), positive oxygen balance (+4.79%), and a calculated crystal density of ρ = 2.274 g cm-3 at 100 K. Its physicochemical properties concomitantly with its straightforward synthesis make it a potential replacement for lead-based initiators.

Bis(dinitropyrazolyl)methanes spruced up with hydroxyl groups: high performance energetic salts with reduced sensitivity.

With an aim to improve the overall physical stability of high-performing 3,5-dinitro-functionalised bispyrazolymethanes, a hydroxyl functionality was introduced at the fourth position to obtain 1,1'-methylenebis(3,5-dinitro-1H-pyrazol-4-ol) and its energetic salts. Superior oxygen balance and energy in comparison to the amino substituent at the 4th position and enhanced sensitivity with respect to the nitro and azido substituents helped in unlocking the potential of less explored N-alkylated-4-hydroxy-3,5-dinitropyrazoles. Fine-tuning of properties via dicationic salt formation, which is not feasible in any other reported symmetrically connected pyrazole-based energetic materials, resulted in improved physical and thermal stabilities, as well as energetic performance. Hirshfeld surface analysis, electrostatic potential analysis, the study of aromaticity and weakest Mayer-bond order analysis helped further in studying the structure-property relationship of the synthesized compounds with respect to different reported methylene-bridged symmetrical compounds.

Systematic spectroscopic investigation of structural changes and corona formation of bovine serum albumin over magneto-fluorescent nanoparticles.

Magneto-fluorescent nanoparticles have attracted great attention because of their dual nature as multimodal imaging probes in various biomedical applications. Particulary, it is desirable to understand how these nanoparticles interact with human serum proteins before they are used in biological systems. In this work, the physiological interactions between magneto-fluorescent nanoparticles (MFNPs) and bovine serum albumin (BSA) were systematically investigated. The present observations identified that the collision of MFNPs and BSA caused fluorescence quenching of BSA. Steady state fluorescence, lifetime and anisotropy measurements in the presence of MFNPs supported dynamic quenching of the BSA emission. Furthermore, in the presence of MFNPs, the conformation changes in the BSA structure indicate merely the secondary structural changes. The findings demonstrated that random interactions and hydrophobic forces play a major role in the dynamic quenching. Further, subsequent coating of BSA over MFNPs result in protein corona formation, as is evident through spectroscopic measurements. In light of the present work, MFNPs could serve a purpose in magnetic separation and optical detection of serum proteins from blood plasma in real-time disease diagnosis.