Konovalova I. Peculiarities of the molecular and crystal structure of diamino derivatives of aromatic and heteroaromatic compounds

Experimental and quantum-chemical methods have systematically studied the geometric characteristics of amino groups and factors affecting them. Results have shown that that the geometric characteristics of amino groups depend on the nature of the atom with which the amino group is connected, from the degree of conjugation of the lone electron pair of nitrogen with the π-system of the aromatic cycle and from the influence of the polar environment, which amplifies the conjugation. For model molecules of mono and diaminobenzenes, it was discovered that the role of hydrogen bonds N-H...N' in the formation of the crystalline structure depends on the number and relative position of the amino groups in the ring (ortho, meta or para). The hydrogen bond N-H...N' plays a major role in the ortho-diaminobenzene crystal, forming a building block of crystal packing and a basic structural motive. In crystals of nitro substituted diaminobenzene derivatives, it has been found that the para- or ortho- positions of the amino group relative to the nitro group results in a significant decrease in the acceptor properties of the amino group as a result of the push-pull effect or intramolecular hydrogen bundle. At the same time, the role of the hydrogen bonds N-H...N' in the organization of crystals becomes quite insignificant. An analysis of intermolecular interactions has shown that the weak hydrogen bonds X-H...N', with the participation of the amino group as an acceptor of proton, influence the formation of polymorphic modifications of diaminotriazole, aniline and ortho-diaminobenzene.