Spin state relaxation of iron complexes: The case for OPBE and S12g

The structures of nine iron complexes that show a diversity of experimentally observed spin ground states are optimized and analyzed with Density Functional Theory (DFT). An extensive validation study of the new S12g functional is performed, with the discussion concerning the influence of the environment, geometry and its overall performance based on the comparison with the well proven OPBE functional. The OPBE and S12g functionals give the correct spin ground state for all investigated iron complexes. Since S12g performs remarkably well it can be considered a reliable tool for studying spin state energetics in complicated transition metal systems. [Ministerio de Ciencia e Innovación (MICINN, project CTQ2011-25086/BQU), the Ministerio de Economia y Competitividad (MINECO, project CTQ2014-59212/BQU) and the DIUE of the Generalitat de Catalunya (project 2014SGR1202, and Xarxa de Referència en Química Teòrica i Computacional); MICINN and the FEDER fund (European Fund for Regional Development) under grant UNGI10-4E-801, and the Serbian Ministry of Education and Science (Grant No. 172035). This work was performed in the framework of the COST action CM1305 "Explicit Control Over Spin-states in Technology and Biochemistry (ECOSTBio)" (STSM reference: ECOST-STSM-CM1305-27360).]