Theoretical study of the Fe(phen)(2)(NCS)(2) spin-crossover complex with reparametrized density functionals

Area of Science:

• Computational chemistry
• Materials science
• Solid-state physics

Background:

• Theoretical studies of spin-crossover (SCO) compounds face challenges in accurately reproducing experimental electronic structures.
• Standard density functional methods often inaccurately predict the energy splitting between low-spin and high-spin states.

Purpose of the Study:

• To investigate the electronic and vibrational contributions to spin-crossover energy splitting in transition metal compounds.
• To evaluate the effectiveness of reparametrized density functionals for SCO phenomena.
• To classify SCO compounds based on hybrid density functional theory calculations.

Main Methods:

• Hybrid density functional theory (DFT) calculations were employed.
• A classification scheme for transition metal compounds was developed.
• The spin-crossover compound Fe(phen)(2)(NCS)(2) was studied.
• Electronic energy splitting and vibrational effects (harmonic force-field approximation) were calculated.

Main Results:

• A method for calculating the electronic contribution to energy splitting was established.
• Exact-exchange reduction in hybrid density functionals is necessary for accurate electronic energy splittings.
• Reparametrized density functionals provide improved results compared to standard functionals for SCO molecules.
• Vibrational effects on spin-flip were investigated.

Conclusions:

• Standard density functionals fail to accurately reproduce the electronic contribution to low-spin/high-spin splitting.
• Reparametrized density functionals show promise for predicting spin-crossover effects.
• Accurate theoretical predictions of SCO phenomena are vital for understanding and designing materials for applications such as transition metal catalysis.