ИСТИНА

The structure and stability of complexes of silver atom with cholesterol (Ch) and tiocholesterol (TCh) molecules are studied at the MP2 level of theory. Stuttgart group ECP with Def2 parameterization and def2-SVP basis set is used. Computational procedure is chosen to reproduce experimental bond length (2.5310 A[1]) and vibrational frequency (192.4 cm-1[2]) of silver dimer (Ag2). MP2 calculations give more accurate values (2.552 A and 192.15 cm-1) than the conventional DFT calculation with B3LYP, PBE and PW91 parameterizations. Similarly, calculated vibrational frequencies of Ag2O are in the reasonably agreement with observable value (443.3 cm-1). Calculated structure of the Ag‑Ch system is presented at figure below. The structure of Ag-TCh is analogous. Equilibrium distances of Ag-O and Ag-S are 2.034 and 2.353 A respectively. Transition from cholesterol to tiocholesterol systems leads to changes of bond angle from 1190 (Ag-O-C) to 1030 (Ag-S-C). For the evaluation of the stability of Ag‑containing complexes, the energies of simplest reactions with Ag2O are estimated. These calculations are carried out for the precise modeling of Ag-containing nanoparticles with some cholesterol molecules. This work was supported by the Russian Foundation for Basic Research, project number № 13-03-00792. The authors thank the Research Computing Center of MSU for providing computational resources. References [1] The bond length of silver dimer //B. Simard et al. Chem. Phys. Lett. V. 186, P.415 (1991). [2] NIST Chemistry Webbook(http://webbook.nist.gov/chemistry/)