In this paper, we discuss the origin of magnetic chirality of chiral magnets made by chromium (III) and manganese (II) ions. Structurally characterized yellow needles: K0.4[Cr(CN)6][Mn(S)-pn](S)-pnH0.6 ((S)-pn = (S)-1,2-diaminopropane) and green needles: [Cr(CN)6][Mn(S or R)-pnH(H2O)]H2O were obtained by the reaction among K3[Cr(CN)6], Mn(ClO4)2 , (R or S)-pn·2HCl and KOH.The space groups of green needle and yellow needle are P 212121 and P 61, respectively. From the X-ray crystallographic analysis of them, the yellow needle has three-dimensional and green needle has two-dimensional magnetic connectivity. These ferrimagnets are good candidates for chiral spin order at low temperature. We present some theoretical supports, within classical phenomenologies, to understand characteristic features of the chiral magnetic materials and their magnetic properties.) Dedicated to Prof. MichinoriŌki on occasion of his 77th birthday.

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We observed a giant nonlinear magnetic response in a molecule-based magnet, ͓Cr͑CN͒ 6 ͔͓Mn͑R͒-pnH͑H 2 O͔͒͑H 2 O͒, in which single chiral ligands ͓͑R͒-pn's͔ construct intermolecular network. The giant nonlinear magnetic response occurs at slightly higher temperature side of the magnetic ordering temperature. The existence of giant nonlinear response yields quite strange shape of the superconducting quantum interference device response against ac magnetic field. This response does not appear in the racemic system involving two kinds of chiral ligands ͓͑R͒-pn and ͑S͒-pn͔, suggesting that the crystallographic chirality plays a crucial role in the occurrence of the giant nonlinear response.

We present a case of a concerted sequence of several characteristic biological reactions such as electron transfer, mixed valency, proton or ion motion, and dehydration−rehydration occurring in a single crystal and its associated phase transformations. It provided a unique opportunity to look for accurate pictures of sequence mimicking biological function using crystallography. Here, we report the observation of a reversible musclelike action associated with proton motion between ammonium and coordinated and uncoordinated water molecules in unison in which the whole X-ray diffraction study (including eight structure determinations as a function of temperature and cycling through two phase transformations) was performed in situ on a single crystal of the chiral molecular magnetIn addition, the reversible structural change in dimensionality from two-to three-dimensional is observed with an increase in the ferrimagnetic Curie temperature from 38 to 73 K upon dehydration.