При этом, координационный полиэдр MnO6 имеет форму вытянутого октаэдра. <...> Высокоспиновое состояние 5A соответствует седловой точке на ППЭ, при этом координационный полиэдр приобретает форму сжатого октаэдра. <...> Оптимизация структуры симметрии С2 для электронного состояния 1B привела к структурным параметрам молекулы, близким к параметрам, полученным для электронного состояния 3A2. <...> Электронные состояния 3A2 и 1B лежат выше, чем высокоспиновое состояние на 5,2 и 17,3 ккал/моль, соответственно. <...> N 4 UDC: 544.18,539.27 MOLECULAR STRUCTURE OF MANGANESE TRIS-ACETYLACETONATE IN DIFFERENT SPIN STATES R.J.F. Berger, G.V. Girichev, N.I. Giricheva, A.A. Petrova, V.V. Sliznev, N.V. Tverdova Raphael Johann Friedrich Berger Department of Materials Research and Physics; Chemistry of Materials, Paris Lodron University of Salzburg, Jakob-Haringerstr. 2A, Salzburg, 5020, Austria E-mail: raphael.berger@sbg.ac.at Georgiy V. Girichev *, Angelika A. Petrova, Valery V. Sliznev, Nataliya V. Tverdova Department of Physics, Ivanovo State University of Chemistry and Technology, Sheremetievskiy ave., 7, Ivanovo, 153000, Russia E-mail: girichev@isuct.ru *, paa-1@mail.ru, sliznev@isuct.ru, tverdova@isuct.ru Nina I. Giricheva Department of Organic and Physical Chemistry, Ivanovo State University, Ermak st., 39, Ivanovo, 153025, Russia E-mail: n.i.giricheva@mail.ru Quantum chemical calculations of the geometric structure, force fields and harmonic vibration frequencies of the molecule Mn(acac)3 for electronic states with multiplicities M = 1, 3 and 5 were performed using the GAUSSIAN 09 program in the framework of density functional theory (DFT/UB3LYP) with correlation-consistent valence three-exponential basis functions cc-pVTZ. <...> The structure with high-spin state S=2 (symmetry of electronic state 5B) possesses the lowest energy and it is characterized by C2 symmetry. <...> The coordination polyhedron MnO6 possesses the shape of “elongated octahedron”. <...> The high-spin state 5A is characterized by structure of compressed octahedron. <...> The distortion of octahedral structure of coordination polyhedron in the states 5A and 5B is significant, and this fact testifies to the strong Jahn-Teller effect, or vibronic effect, in 5E electronic state. <...> The optimization resulted in C2 symmetry of molecule having the symmetry <...>