X-ray diffraction and ab initio quantum-chemical study of the charge density in the crystals of Meisenheimer complexes - Derivaitives of 2,4,6-trinitrobenzene and 5,7-dinitroquinoline

The experimental charge density in the crystals of two Meisenheimer complexes (MC), hydrate of potassium 2',4',6'-trinitro-3',5'-dihydrospiro(1,3-dioxolane-2,8'-cyclohexadienide) 1 and potassium 5',7'-dinitro-5',8'dihydrospiro(1,3-dioxolane-2,8'-quinolinide) 2 has been studied using low-temperature, high-resolution X-ray diffraction data. A theoretical study of this charge density obtained from HF/6-311++G** and B3LYP/6311++G** calculations has been carried out as well for comparison. It was shown that potassium cations coordinated with sigma-complex in these crystals considerably affect the charge density distribution. Each anionic sigma-complex in both structures is surrounded by five cations, and the specific influence of the cation in each position on the charge density characteristics has been revealed.