Many laboratories have performed extensive studies on the spin-crossover (SCO) phenomenon. Herein, we synthesized novel “Soma–Iwamoto type” complexes containing a 4-methoxypyrimidine (4-MeOPmd) ligand, i.e., {Fe(4-MeOPmd)2[Ag(CN)2]2} (1Ag), {Fe(4-MeOPmd)2[Au(CN)2]2} (1Au), and {Fe(4-MeOPmd)2[Ag(CN)2]2·0.25(4-MeOPmd)} (1Ag·0.25G). Moreover, we synthesized a 4,6-dimethoxypyrimidine (4,6-diMeOPmd) clathrate complex, i.e., {Fe(4-MeOPmd)2[Ag(CN)2]2·0.25(4,6-diMeOPmd)} (2Ag·0.25G) and {Fe(4-MeOPmd)2[Au(CN)2]2·0.25(4,6-diMeOPmd)} (2Au·0.25G). Some of these complexes, i.e., 1Ag·0.25G, 2Ag·0.25G, and 2Au·0.25G, demonstrated penetrated structures, which are very interesting given that they have rarely been reported to date. 1Au and 1Ag did not show the SCO phenomenon, 1Ag·0.25G showed a gradual multi-step SCO phenomenon, and 2Au·0.25G and 2Ag·0.25G showed an abrupt half SCO phenomenon.
![Graphical abstract: Guest-triggered “Soma–Iwamoto-type” penetration complex {Fe(4-methoxypyrimidine)2[M(CN)2]2}·Guest (M = Ag, Au)](http://hg.y866.cn/compound/lib/scimg/usr/1/D2DT03716E.jpg)
