STRUCTURES OF TRIS(DONOR)-TRIS(ACCEPTOR)-SUBSTITUTED BENZENES .2. POTASSIUM-SALTS OF TRINITROPHLOROGLUCINOL

The X-ray crystallographic analysis of the mono-, di-, and tripotassium salts 2b - d of trinitrophloroglucinol (2a) show their benzene rings to become considerably more distorted on successive deprotonation. A parallel increase in C - C, and a decrease in C - O and C - N bond lengths leading to a radialene-type structure is also observed. For 2b, two chemically different molecules are found in the crystal which differ in their hydrogen-bond pattern as well as in their average bond lengths and deviation of their benzene rings from planarity. AM1 calculations show that for 2b, d a multitude of structures, differing widely in the deviation of their benzene cores form planarity, can exist within a small energy range (< 3 kcal/mol). The experimental and computational results are discussed in terms of a model that emphasizes ''push-pull'' interactions as the main cause for the distortions of the benzene rings in compounds of type 1 and 2.