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Nicotine (C10H14N2, nic) is one of the alkaloids well recognized for it's toxin activity, and it's chemistry is an important topic because of its health implications. Nicotine possesses the methylated pyrrolidine nitrogen (pKb1 = 6.16) and the less basic pyridine nitrogen (pKb2 = 10.96), thus it forms a chelate complex resulting in a CuN2X2 chromophore when it reacts with the copper(II) halides. The complex shows a distorted tetrahedral geometry around the copper(II) site (C2v) due to the steric hindrance of the nicotine ligand in the resulting chelate complex. Double protonation of nicotine gives a nicotinium cation, nicH2, which is expected to form easily into crystalline salts with tetrahalometallate(II) anions of the general formula [C10H16N2][MX4]. Recently we reported on the single crystal structure of (nicH2)CuCl4. The crystal exhibited two crystallographically non-equivalent pseudotetrahedral [CuCl4] anions, each of which was linked to two doubly protonated nicotinium cations via hydrogen bonds. The pseudotetrahedral (D2d) geometry around the Cu(II) site in (nicH2)CuCl4 arose from the packing effect caused from the large nicH cation size as well as the strong hydrogen bonding networks between the protonated nicotinium cation and the chloride atoms in [CuCl4]. The pseudotetrahedral copper(II) complexes were interesting in that they were proposed as a mimic compound of active sites in copper proteins. Herein, we investigate the optical and magnetic properties of (nicH2)CuX4 (X=Cl, Br) complexes, and elucidate the observed properties in accordance with the corresponding pseudotetrahedral geometry of the Cu(II) site in the prepared complexes. Furthermore, we synthesize a nicotinium tetrahalocobaltate(II), (nicH2)CoX4 complex. We report on the single crystal structure of the nicotinium tetrachlorocobaltate(II) complex and compare it to that of (nicH2)CuCl4 complex. The optical and magnetic properties of (nicH2)CoCl4 were examined and explained as a symmetric [CoCl4] unit.

bulletin of the korean chemical society

Preparation and Characterization of Nicotinium Tetrahalocuprate(II) and Tetrahalocobaltate(II) Complexes : Structure of Nicotinium Tetrachlorocobaltate(II)