[Zurück]

C. Knoll, D. Müller, M. Seifried, P. Weinberger:
"Elucidating structural features of rigid spin crossover coordination polymers using HPC";
Vortrag: AHPC16, Grundlsee; 22.02.2016 - 24.02.2016; in: "Austrian HPC Meeting 2016 - AHPC16", VSC - Vienna Scientifc Cluster (Hrg.); (2016), S. 50.

Spin crossover compounds might play an important role for future technological applications, such as memory,
sensing or switching devices. An essential feature of such compounds for a potential use in devices is
cooperativity between the metal centers to enable an abrupt spin transition [1].
Gaussian 09 Rev.D implemented on VSC-3 was used for quantum chemical structural investigations of
iron(II) tetrazole based spin crossover polymers. The aim of this work is a modeling of structural features,
so far inaccessible to elucidate with available experimental techniques.
From di erent measurements it is known, that solvent molecules are located inside the cavities formed
by the benzene rings. Due to crystal quality it was not possible to assign unambiguously residual electron
density, found on single crystal X-ray analysis, to a de ned solvent position. Therefore, a theoretical attempt
was chosen to investigate possible preferred solvent positions. This was done by placing a pre-optimized
molecule of propylene carbonate into the center of the void of the prior calculated low spin structure. After
optimization to a minimum, proven by vibrational analysis, which showed no imaginary frequencies, only
one preferred position, as depicted in Figure 1 was obtained. This was even true, if the calculation was
started from di erent starting positions of the solvent guest. The ve membered carbonate ring aligns nearly
parallel to one of the benzene rings with a centroid distance of 4.14 A. The carbonyl oxygen has a distance
of 3.15 A towards the N3 of the nearest tetrazole ring. The methyl group of the solvent molecule has a
minimum distance of about 2.9 A towards the N2 of the opposite tetrazole ring, the oxygen is facing to. The
central carbon atom lies on the virtual axis connecting the iron(II) centers. The attempt to force a second
molecule of propylene carbonate into the void results in convergence failure, as one of the molecules is forced
to leave the cavity. These results were reproducible for other solvents as acetonitrile and nitromethane.

http://publik.tuwien.ac.at/files/PubDat_248266.pdf