Theoretical study on high-spin to low-spin transition of {Fe(pyrazine)[Pt(CN) 4]}: Guest-induced entropy decrease

• Published in: Chemical physics letters Vol. 511; no. 4; pp. 399 - 404
• Main Authors: Ando, Hideo, Nakao, Yoshihide, Sato, Hirofumi, Ohba, Masaaki, Kitagawa, Susumu, Sakaki, Shigeyoshi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-08-2011
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2011.06.084

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►First study on the mechanism of guest-induced spin transition. ► Large entropy difference in the porous coordination polymer between low and high spin states. ► Decrease in the entropy difference in CS
2 clathrate induces high to low spin transition.
A porous coordination polymer (PCP), {Fe
II(pyrazine)[Pt
II(CN)
4]}, adsorbs CS
2 molecules to induce spin transition from high-spin (HS) to low-spin (LS) state. To elucidate this mechanism, we investigated flexibility of the PCP framework, namely rotation of pyrazine ligands, with DFT method and evaluated the rotational entropy difference
(
Δ
S
rot
HS
–
LS
)
between the HS and LS states with Fourier grid Hamiltonian method. The
Δ
S
rot
HS
–
LS
value is considerably large in the absence of CS
2. The CS
2 adsorption occurs between two pyrazine ligands to suppress the pyrazine rotation in both states, which decreases
Δ
S
rot
HS
–
LS
to induce the HS
→
LS transition at room temperature.