STERIC AND ELECTRONIC EFFECTS OF THE SUBSTITUENTS IN 10-YLIDENANTHRONES-9
A.Yu.
Kovalevsky, O.V. Shishkin, I.Yu. Antipin, I.A. Ronova, Z.N. Tarakhno
1A.N.
Nesmeyanov Institute of Organoelement Compounds, Russian
Academy of Sciences, 117813 Moscow, 28 Vavilov st.
2The Institute
for Single Crystals,National Academy of Sciences of the Ukraine,
310001 Kharkov,
60 Lenin ave. Kharkov State University,
310077, 4 Svobody sq.
Using X-ray structural analysis and calculations by semiempirical quantum-chemical method AM1, the influence of steric and electronic effects of the substituents upon the structure and conformational dinamics of 10-ylidenanthrones-9 has been studied.
The central six-membered partly hydrogenated cycle in methylidenanthrone (1) has an equilibrium conformation of a distorted boat, caused by non-valence interactions between hydrogen atoms at the exocyclic C=C bond and those being at the peri-positions of the benzene rings. When an H-atom at the C=C bond sustituted by phenyl group, it resulted in sharp disflattening of the dihydrocycle, the central ring conformation maintained.
In the nitro derivative due to the rotation of the aromatic cycle around C(Ar)-C(sp2) bond of 68 the conjugation between aryl group and C=C bond in question is almost absent. When acceptor nitro group replaced by donor one (NMe2) or OMe, this causes a substantial decrease of rotation angle of the aryl cycle. The changes of the conformation of 9,10-dihydroantracene fragment have an opposite tend, it connected to non-valence ineractions features between the groups examined.
Using calculations by AM1 method, conformational flexibility of the dihydrocycle and the influence of the substituents effects upon the former has been investigated.
Using Monte-Carlo method, the values of Kuhn segment of polymers contained in their structural unit anthranylidene moiety have been calculated, rigidity of which depended on the conformational flexibility of the central dihydrocycle.
R'=H, Ph, C6H4-p-Cl, C6H4-p-N(Me)2, C6H4-p-OMe, C6H4-p-NO2
The model polymers obtained can be attributed to the class of flexible ones (segment Kuhn magnitude about 100 A). As to the calculation the most flexible is a polymer with R'=Ph, the most rigid one with R'=C6H4-p-NO2.