Abstract
Without self-interaction corrections or the use of hybrid functionals, approximations to the density-functional theory (DFT) often favor intermediate spin systems over high-spin systems. In this paper, we apply the recently proposed Fermi–Löwdin-orbital self-interaction corrected density functional formalism to a simple tetra-coordinated Fe(II)-porphyrin molecule and show that the energetic orderings of the S = 1 and S = 2 spin states are changed qualitatively relative to the results of Generalized Gradient Approximation (developed by Perdew, Burke, and Ernzerhof, PBE-GGA) and Local Density Approximation (developed by Perdew and Wang, PW92-LDA). Because the energetics, associated with changes in total spin, are small, we have also calculated the second-order spin–orbit energies and the zero-point vibrational energies to determine whether such corrections could be important in metal-substituted porphins. Our results find that the size of the spin–orbit and vibrational corrections to the energy orderings are small compared to the changes due to the self-interaction correction. Spin dependencies in the Infrared (IR)/Raman spectra and the zero-field splittings are provided as a possible means for identifying the spin in porphyrins containing Fe(II).
Highlights
Because transition-metal atoms can exist in multiple spin and charge states and because of their large naturally occurring terrestrial abundance, nature has chosen such systems to form the basis of many life-maintaining molecular systems
The chemical functions are impacted by varying spin states and/or charge states of the transition-metal system, and this is important for the mammalian oxygen-transporting mechanisms that are accomplished by Heme-like molecules [1,2,3,4,5,6,7,8]
Some evidence of energetic ambivalence in such systems may be deduced by noting the similarities and minor deviations in structure associated with the Mn centers that are predominantly undercoordinated in photosystem II but predominantly six-fold coordinated in the Mn12-Acetate molecular magnet [9,10]
Summary
Because transition-metal atoms can exist in multiple spin and charge states and because of their large naturally occurring terrestrial abundance, nature has chosen such systems to form the basis of many life-maintaining molecular systems. The chemical functions are impacted by varying spin states and/or charge states of the transition-metal system, and this is important for the mammalian oxygen-transporting mechanisms that are accomplished by Heme-like molecules [1,2,3,4,5,6,7,8]. Some evidence of energetic ambivalence in such systems may be deduced by noting the similarities and minor deviations in structure associated with the Mn centers that are predominantly undercoordinated in photosystem II but predominantly six-fold coordinated in the Mn12-Acetate molecular magnet [9,10]. Synthesis of molecular magnets with six-fold coordination, accomplished by Lis et al [11] and Christou et al [12], suggests an energetic preference associated with six-fold coordinated centers. More recent work reinforces the suggestion that the six-fold coordination of transition metal centers [13,14] is favored over the lower-coordination systems
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
