Periodic density functional theory studies on trinitrophloroglucinol and its alkali metal salts

The banding and electronic structures of trinitrophloroglucinol (TNPG) and its alkali metal salts have been investigated at B3LYP level by a periodic density functional theory (DFT) method. The relationship between structure and property was discussed. The calculated lattice parameters are in good agreement with the experimental values. The results show that the conductivity of TNPG is between the semiconductor and insulator, however, its alkali metal salts are electrical semiconductors. The existence of metallic atoms results in the packing of anions and cations through coordinated bonds to form a network structure. And this is correlated with the semiconducting property of the alkali metal salts. The frontier orbitals of TNPG and its alkali metal salts all mainly consist of atomic orbitals of C-NO₂ groups, but the coordinated water molecules and metallic ions do not have any contributions to it. The values of band gaps of all the alkali metal salts are smaller than that of TNPG. Consequently, the alkali metal salts are more sensitive than TNPG, according to the "principle of the easiest transition", and this prediction is in good agreement with the experimental result. In addition, the existence of metallic atoms makes the phenol oxygen atoms more reactive which may be one of the reasons that alkali metal salts are more sensitive than TNPG.