New solid state Ni(II)-famotidine square-planar complex: powder diffraction and spectroscopic studies Malgorzata Baranska a, * , Wiesław Łasocha a , Henryk Kozłowski b , Leonard M. Proniewicz a,c, * a Faculty of Chemistry, Jagiellonian University, 3 Ingardena Str., 30-060 Krak ow, Poland b Faculty of Chemistry, University of Wroclaw, 14 F. Joliot-Curie Str., 50-383 Wroclaw, Poland c Laser Raman Laboratory, Regional Laboratory of Physicochemical Analysis and Structural Research, Jagiellonian University, 3 Ingardena Str., 30-060 Krak ow, Poland Received 13 August 2003; received in revised form 11 February 2004; accepted 17 February 2004 Available online 19 March 2004 Abstract Recent potentiometric studies have claimed that Ni(II) forms three pH-dependent complexes with famotidine. We isolated two of them from the solution; namely the paramagnetic complex NiL with octahedral geometry and the diamagnetic complex NiH 2 L with square-planar geometry. The latter compound constitutes the subject of this work. The crystal structure of nickel (II) famotidine complex NiC 8 N 7 O 2 S 3 H 13 discussed here, determined with the powder diffraction method, has shown that it belongs to a Pbcn space group (60) with a, b, c ¼ 24:328(4), 14.747(2), 7.786(1), V ¼ 2793:6(5)  A 3 . R F and R wp are 16.1% and 15.5%, respectively. Additionally, the UV–VIS, FT-FIR and Raman spectroscopic methods were employed to discuss and support the structure of the NiH 2 L complex suggested by X-ray data. The structure presented in this work is the second example of the complex of a famotidine ligand with a transition metal ion in the solid state. The other one, reported from a single crystal X-ray structure of famotidine complex with Cu(II), is quite different. Ó 2004 Elsevier Inc. All rights reserved. Keywords: Ni(II)-famotidine complex; Powder diffraction method; Rietveld method; UV–visible; FT-FIR; Raman spectroscopy 1. Introduction Famotidine (fam), 3-[[[2-[(aminoiminomethyl)amino]- 4-thiazolyl]methyl]thio]-N -(aminosulfonyl) (Fig. 1), is a histamine H 2 -receptor antagonist that is a high potent inhibitor of gastric and acid secretion in humans [1,2]. It has been used mainly for the treatment of peptic ulcers and the Zollinger–Ellison syndrome. Due to the presence of amino, amido and thioether groups in its structure, this drug possesses chelating properties and may interact very effectively with the essential metal ions present in blood plasma and different tissues. Transition metal fa- motidine complexes have been recently investigated in view of their potent biological activity involving such metal ions as Cu(II), Ni(II), Pt(II) and Pd(II) [3–8]. The Cu(II)-famotidine complex was obtained and its crystal structure determined using the single crystal X-ray method [4]. The data show that Cu(II) coordinate to a fam molecule through guanidine N(3), thiazole N(9) nitrogen atoms, tioether sulfur S(11) from the aliphatic chain and a terminal amidine nitrogen N(16) atom. Recently, a new complex, NiH 2 L, consisting of famotidine with the Ni(II) ion has been reported in the solid state obtained at pH 8. This complex appeared to be diamagnetic [5]. Un- fortunately, due to the lack of suitable single crystals, its molecular structure was proposed mainly based on IR and RS spectra in the solid state and on the 15 N, 13 C, 1 H NMR measurements in the DMSO (dimethyl sulfoxide) solution. These data confirmed square-planar geometry of the discussed complex, in which two protons were re- leased from a ligand to form NiH 2 L without the anion * Corresponding authors. Tel.: +48-12-633-6377; fax: +48-12-634- 0515 (M. Baranska). E-mail addresses: baranska@chemia.uj.edu.pl (M. Baranska), proniewi@chemia.uj.edu.pl (L.M. Proniewicz). 0162-0134/$ - see front matter Ó 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jinorgbio.2004.02.016 Journal of Inorganic Biochemistry 98 (2004) 995–1001 www.elsevier.com/locate/jinorgbio JOURNAL OF Inorganic Biochemistry