The electronic structures of a triazole-bridged Fe(II) chain of (MX3)n type are examined employing the extended Hückel approximation. Several aspects of the spin transition in the one-dimensional system are presented using a regular chain model with all Fe-N bonds of 2.166 Å, a contracted chain model with all Fe-N bonds of 2.031 Å, and a bond-length-alternant chain model with long and short Fe-N bonds of 2.176 and 2.031 Å. The relative stability among the high-spin (HS), intermediate-spin (IS), and low-spin (LS) states is compared taking one-electron energies and qualitative electron-electron interactions into account. In the regular chain model, "six-below-four" d-block bands appear, and this chain structure is appropriate for the HS state above the observed transition temperature (Tc). On the other hand, in the alternant chain model, one pair of the eg-block bands is significantly destabilized as a result of geometry perturbation. Below Tc, the LS diamagnetic state in a sufficiently long chain is likely to be more stable than the IS state, which has an -(S = 2)-(S = 0)-(S = 2)-(S = 0)- structure.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry