Transition Metal Halide Salts of 2-Amino-5-Substituted-Pyridines: Synthesis, Crystal Structure and Magnetic Properties of Two Polymorphs of (5-IAP)₂CuCl₄[5-IAP = 2-Amino-5-Iodopyridinium]

Abstract

The reaction of anhydrous CuCl 2 with HCl and 2-amino-5-iodopyridine in 1-propanol resulted in two polymorphs of (5-IAP) 2 [CuCl 4 ] [5-IAP ¼ 2-amino-5-iodopyridinium], one as red rods (1) and one as orange prisms (2). The two polymorphs have been characterized by single crystal x-ray diffraction and variable temperature magnetic susceptibility. Crystal data: triclinic, P-1, F(000) ¼ 606, MoK ( ¼ 0.71073 Å ): for (1): a ¼ 9.248 (6), b ¼ 10.202(7), c ¼ 10.368(7) Å , ¼ 102.451(9), ¼ 96.662(8), ¼ 96.725(8) , V ¼ 938.4(11) Å 3 , Z ¼ 2, D calc ¼ 2.291 Mg/m 3 , ¼ 5.020 mm À1 , R ¼ 0.0392 for [|I| ! 2 (I)]. For (2): a ¼ 8.966(2), b ¼ 10.755(2), c ¼ 11.359(2) Å , ¼ 89.63(3), ¼ 68.04(3), ¼ 69.07(3) , V ¼ 938.6(3) Å 3 , Z ¼ 2, D calc ¼ 2.291 Mg/m 3 , ¼ 5.019 mm À1 , R ¼ 0.0217 for [|I| ! 2 (I)]. The crystal packing for both polymorphs suggests that their magnetic behavior should be that of weakly interacting alternating linear chains. Temperature dependent susceptibility measurements yield: for 1, C ¼ 0.43, g ¼ 2.14, ¼ À 1.98; for 2, C ¼ 0.45, g ¼ 2.19, ¼ À 4.15.

Effects of halogen and hydrogen bonding on defect disorder: the ladder that wasn't there

“…4c, 14,15 The C-I … Cl halogen bonding is of comparable strength to the corresponding N(pyridinic)-H … Cl hydrogen 13 bonding interactions, if not stronger. Halogen and hydrogen bonding are controlled mainly by electrostatics, 12 which agrees with the observation that N(H) … Cl4 and I … Cl4 distances are shorter than the corresponding N(H) … Cl1 and I(or Br) … Cl1 distances in 3 and 4. In 1 and 2, the occupancy disorder is 50 : 50, hence C-I … Cl halogen bonding and N(pyridinic)-H … Cl hydrogen bonding interactions will be comparable in these two structures.…”

“…2-Amino-5-iodopyridine was synthesized according to the literature procedure. 12 Copper(II) chloride dihydrate was purchased from Mallinckrodt. All chemicals were used as received.…”

2-Amino-5-iodopyridinium bromide hemihydrate and 2-amino-5-iodopyridinium chloride monohydrate

“…5. As observed for (1), the bond lengths and angles within the pyridinium ring are the same as those reported in the literature (Landee et al, 2001;Giantsidis et al, 2002). Water molecule O1 serves as a hydrogen-bond acceptor to the amino N atom, while anion Cl1 serves as an acceptor for the pyridinium N atom (Table 3).…”

“…literature, within experimental error (Landee et al, 2001;Giantsidis et al, 2002). The bromide anions are linked by hydrogen bonding to both amino and pyridinium H atoms (Fig.…”

“…The hydrogen-and halogen-bonding interactions seen in both (1) and (2) provide structural motifs that can stabilize the positions of metal ions in the crystal structure, as demonstrated successfully in the previously reported copper(II) complexes (Landee et al, 2001;Giantsidis et al, 2002). Efforts to exploit this phenomenon with other metal ions are in progress.…”