Investigation of intramolecular hydrogen bond in anthra [2,3-b]thiophene-5,10-dione derivatives

Anthracene 9, 10-diones such as ametantrone and mitoxantrone are among the antitumor drugs. Synthesized derivatives of anthra [2, 3-b] thiophene -5,10-dione, demonstrated high therapeutic and antitumor potency. The aim of this research is investigating the geometry and intramolecular hydrogen bond of anthra [2,3-b] thiophene -5,10-dione derivatives. We also considered a derivative of 4, 11-diamino naphtho [2, 3-f] indole -5, 10- diones. Theoretical calculations of these compounds have been analyzed by means of DFT calculations at B3LYP level by using 6-311++ G** basis set. All of these calculations were carried out with Gaussian 09 software program. Our results revealed that the structure of distal amino groups and the kind of heteroatom in the structure of these compounds have wide effects on the intramolecular hydrogen bonds that have been analyzed by natural bond orbital (NBO) analysis. By NBO method, the effect of substitution on hydrogen bond strength, steric effects and energies of interactions in the studied compounds were considered. 1H NMR for studied compounds have been calculated at the B3LYP/6-311++G** theoretical level. The calculated chemical shifts of the chelated proton for all molecules, using GIAO method, are well correlate with the calculated geometrical parameters results.