In silico investigations of high-energy density properties and effect of ring fusion on dinitropyrazole derivatives.

The molecular and high-energy density properties of isolated (3,4-dinitropyrazole, 34DNP) and fused pyrazole ring (1H,4H-3,6-dinitropyrazolo[4,3-c]pyrazole, DNPP) systems were studied by density functional theory (DFT) at the B3LYP/G D3BJ level of theory with def2-TZVP basis set. The theoretically optimized geometrical parameters of both molecules are similar to the corresponding experimental geometrical values. With this, atoms in molecules (AIM), electrostatic, intrinsic bond strength index (IBSI), and natural bond orbital (NBO) properties of the 34DNP and DNPP molecules were studied. These studies show that one of the nitro groups in 34DNP is less stable than other nitro groups present in 34DNP and DNPP molecules. The optimized geometry, AIM analysis, and NBO results confirmed that one of the C-NO2 groups in isolated dinitropyrazole 34DNP makes fewer orbital interactions with the pyrazole ring, and deviation in planarity leads to relatively less stability and acetic than the fused dinitropyrazole DNPP molecule. These studies reveal that the effect of ring fusion in dinitropyrazole derivatives may be used to design high-quality high-energy density materials. [ABSTRACT FROM AUTHOR]