AbstractMagnetic crystals were formed using supramolecular cation structures that consist of (S)‐AIH+(dibenzo[18]crown‐6), (R)‐AIH+(dibenzo[18]crown‐6), or (RS)‐AIH+(dibenzo[18]crown‐6) (AIH+ = indan‐1‐aminium) as the counter cation to [Ni(dmit)2]– ions (dmit2– = 2‐thioxo‐1,3‐dithiole‐4,5‐dithiolate), which bear one S = 1/2 spin. The resulting salts, (S)‐AIH+(dibenzo[18]crown‐6)[Ni(dmit)2] (1), (R)‐AIH+(dibenzo[18]crown‐6)[Ni(dmit)2] (2), and (RS)‐AIH+(dibenzo[18]crown‐6)[Ni(dmit)2] (3), feature supramolecular cations that are formed through the inclusion of the ammonium moiety of AIH+ into the cavity of dibenzo[18]crown‐6 through N–H···O hydrogen bonds. Salts 1, 2, and 3 possess space groups of P21, P21, and P2/m, respectively, and possess similar molecular packings. Chiral cations (S)‐AIH+ (salt 1) and (R)‐AIH+ (salt 2) yielded chiral crystals, whereas racemic (RS)‐AIH+ (salt 3) afforded a racemic crystal with a mirror plane. Within the crystals, alternating layers of [Ni(dmit)2]– ions and(AIH+)(dibenzo[18]crown‐6) cations formed a layered structure along the b axis. Since the 21 axis of salts 1 and 2 were observed along the b axis, effective chiral magnetic interactions between the [Ni(dmit)2]– ions were not observed. In the ac plane, weak interactions among the [Ni(dmit)2]– ions formed a two‐dimensional layer. Temperature‐dependent magnetic susceptibilities of salts 1, 2, and 3 exhibited aCurie–Weiss‐type behavior, which shows weak antiferromagnetic interactions between the [Ni(dmit)2]– ions, with Weiss temperatures of –2.9, –2.9, and –4.2 K, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)