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Научни трудове на Съюза на учените в България-Пловдив. Серия В. Техника и технологии, естествен ии хуманитарни науки, том XVI., Съюз на учените сесия "Международна конференция на младите учени" 13-15 юни 2013. Scientific research of the Union of Scientists in Bulgaria-Plovdiv, series C. Natural Sciences and Humanities, Vol. XVI, ISSN 1311-9192, Union of Scientists, International Conference of Young Scientists, 13 - 15 June 2013, Plovdiv.
SYNTHESIS AND CHARACTERIZATION OF PLATINUM (II) COMPLEx OF CYCLOPENTANESPIRO-5-(2-THIOHYDANTOIN)
Petja marinova*, marin marinov1, Elena Trendafilova, Plamen Penchev,
Neyko Stoyanov2
Faculty of Chemistry, University of Plovdiv, 24, Tzar Assen Street, 4000 Plovdiv,
marinova@uni-plovdiv. bg Agricultural University - Plovdiv, Department of General Chemistry, Faculty of Plant protection and Agroecology, 12 "Mendeleev" Blvd, 4000 Plovdiv, m_n_
marinov@abv. bg
2 University of Ruse- Branch Razgrad, 3, Aprilsko Vastanie Avenue, 7200
Razgrad
Abstract: Synthesis and structural characterization of new platinum(II) complex of cyclopentanespiro-5-(2-thiohydantoin) is reported. The compounds were study by elemental analysis, IR for Pt(II) complex and UV-Vis, IR, ATR and Raman spectroscopy for free ligand. Based on the experimental data the most probable structure is suggested.
Key words: cyclopentanespiro-5-(2-thiohydantoin), metal complexes
Introduction: Research studies on different hydantoin derivatives have been a long-standing activity due to their physiological action as anticonvulsants and well-established application as antiepileptic drugs [1,2]. The antitumor activity of different thioanalogues of hydantoins is also well documented [3-5]. Thiohydantoin is a good example of a ligand displaying four potential coordination sites, namely the exocyclic oxygen and sulphur atoms and the two ring nitrogens. Beloglazkina et al. synthesized Co(II) complex with 3-phenyl-5-(2-pyridylmethylene)-2-thiohydantoin that was employed as a catalyst for the epoxidation of alkenes [6]. Complexes of thiohydantoin with Co(II), Ni(II) [7] and Sn(IV), Ti(IV) [8] have already been described by Singh et al. On the basis of IR data Singh showed that the ligand actually coordinates as a monodentate through oxygen in Sn(IV) and Ti(IV) and through sulfur in the Co(II) and Ni(II) complexes. Recently Kandyl et al. obtained Co(II), Ni(II) and Cu(II) complexes of 5-(phenylazo)-2-thiohydantoin and 5-(2-hydroxyphenylazo)-2-thiohydantoin [9]. The complexes are characterized by elemental analysis, conductivity, magnetic susceptibility, UV-Vis, IR, ESR, and TG studies. Arrizabalaga et al. prepared and characterized Pt(II) and Pd(II) complexes with thiohydantoin by elemental analysis, NMR and IR spectroscopy [10]. Complexes of Pt(II) and Pd(II) involve thiohydantoin as bidentate ligand. The X-ray structure of Tl(I) complex of 5-benzylidene-2-thiohydantoin [11] and 5-(4'-dimethylaminobenzylidene)-2-thiohydantoin [12] were reported. Ahmedova et al. established the X-ray structure of cyclopentanespiro-5-(2-thiohydantoin) and cyclohexanespiro-5-(2-thiohydantoin) [13]. Cyclopentanespiro-5-(2-thiohydantoin) crystallize
with two molecules in the asymmetric unit in monoclinic crystal system and P 2/c space group. The X-ray structure of Cs(I) complex of 5,5-dimethyl-2-thiohydantoin is known [14]. The crystal structure of Tl(III) complex of 5-(2-pyridinylmethylene)-2-thiohydantoin is determined by X-ray diffraction [15]. The complex crystallize in triclinic crystal system and P1 space group. Solid state IR and solution phase 'H, 13C and 205Tl NMR properties of the complex is also discussed.
Considering the physiological activities and complexation properties of hydantoin and spirohydantoin derivatives and their thioanalogues, the purpose of the present work is to examine the complexation properties of cyclopentanespiro-5-(2-thiohydantoin) (L see Fig.1) with platinum(II) and characterization of the metal complex obtained.
H o
r -NH O
L
Fig.1. Structural formula of cyclopentanespiro-5-(2-thiohydantoin) (L)
I. Experimental part: A metal salt ((NH4)2[PtCl4] - Sigma Aldrich) and solvents used for synthesis of the complexes are with a p.a. qualification. Electronic spectra are registered on UV-Vis Perkin-Elmer Lambda 9 spectrophotometer. The IR spectra were recorded with on a VERTEX 70 FT-IR spectrometer (Bruker Optics): the samples were prepared as KBr pellets. The Raman spectrum of free ligand (the stirred crystals placed in aluminium disc) was measured on RAM II (Bruker Optics) with a focused laser beam of 50 mW power of Nd:YAG laser (1064 nm) from 4000 cm-1 to 51 cm-1 at resolution 2 cm-1 with 25 scans. Attenuated Total Reflection FTIR (ATR) spectra are registered on VERTEX 70 FT-IR spectrometer (Bruker Optics), - MIRacle accessory with one-reflection ZnSe element (Pike); resolution 2 cm-1; 16 scans.
The spectral data of the compounds obtained are as follows:
UV-Vis (CHOH) L : I = 268 nm, 225 nm, 198 nm
v 2 5 7 max ' '
Elemental analysis for Pt(II)L: Calc. [C14H18N4S2O2Pt] (%):C, 31.52; H, 3.38; N, 10.51; Found: C, 31.00; H, 2.95; N, 10.86.
IR (pellet, KBr, cm-1) L: v(NH) - 3305, v(NH) - 3100, 2963-2873 (CH2), v(C=O) - 1738, v(C=S) - 1520, S(NH) - 1452, S(NH) - 1377, 1070 cm-1
IR (pellet, KBr, cm-1) Pt(II)L: v(NH) - 3443, v(NH) - 3252, 2997-2872 (CH2), v(C=O) -1713, v(C=S) - 1495, S(NH) - 1407, S(NH) - 1326, 1024 cm-1
Attenuated Total Reflection FTIR, v : L: 3295, 3088, 2961, 2872, 2788, 2269, 1732,
max
1576, 1559, 1513, 1451, 1436, 1404, 1374, 1316, 1290, 1264, 1232, 1195, 1144, 1068, 1004, 948, 906, 874, 853, 752, 669, 635, 619 cm-1
Relative Raman intensity, vmax,L: 2973, 2920, 2877, 2595, 1746, 1726, 1515, 1453, 1440, 1404, 1323, 1196, 1157, 1077, 1013, 948, 905, 750, 613, 503, 373, 322 cm-1
II. Synthesis of Pt(II) complex of cyclopentanespiro-5-(2-thiohydantoin) (L)
Relevant solutions for Pt(II)L complex:
> A solution of spirohyndatoin L: 0,1 mmol (0,0170 g) in 3 cm3 DMSO and 2 cm3 H2O.
> A solution of (NH4)2[PtCl4] (M): 0,1 mmol (0,0373 g) in 5 cm3 H2O .
> A solution of NaOH: 0,1 M aqueous solution of NaOH - in a 100 cm3 volumetric flask.
Experimental procedure: 5 drops of 0,1 M NaOH were added slowly to a L solution while
stirring at pH=8,3. The solution of metal salt was added in drops from a burette during stirring with an electromagnetic stirrer, until precipitation of the formed complex started for 24 h. A neutral
complex was formed as yellow amorphous precipitate. The precipitate was filtered and washed with ~10-20 cm3 H2O. The complex was dried over CaCl2 for 2 weeks.
III. Results and discussion
Complexation with Pt(II) was conducted under alkaline conditions using a metal salt namely (NH4)2[PtCl4] at molar ratio M:L= 1:1 for PtL. Neutral complex was synthesized and isolated as a precipitate. The PtL complex is yellow in color. The PtL complex was investigated with IR spectroscopy and elemental analysis. Elemental analyses data was found to be in good agreement (±0.5%) with the calculated values. It was found that molar ratio metal:ligand is 1:2. IR spectra of the free ligand and its complex in KBr pellets were recorded in order to clarify the structure of the formed metal complexes and to determine the coordination modes of the ligand. In the IR spectrum of the free ligand L bands at 3305 cm-1 and 3100 cm-1 were observed which we may refer to the stretching vibrations of the two N-H groups of the hydantoin ring (see Table 1). In the spectrum of the PtL complex the same bands are observed at 3443 and 3252 cm-1 which shift to higher frequency by 138 and 152 cm-1 compared to the free ligand spectrum. In the spectrum of free ligand L the bands at 1738 cm-1 (there is a shoulder at it) and 1520 cm-1 can be attributed to stretching vibration of C=O and C=S groups of the hydantoin ring. The band resulting from the oscillation of the C=O group in the IR spectrum of PtL complex is shifted to lower frequencies by 25 cm-1 as compared to that of the free ligand. The same shift of 25 cm-1 to lower frequencies is observed in the band resulting from the oscillation of the C=S group.
Table 1: IR bands (cm-1) in KBr for the free ligand LI and it Pt(II) complex
L Pt(II)L
3305 3443
3100 3252
2963-2873 2997-2872
1738 1713
1520 1495
1452 1407
1377 1326
1070 1024
IR is excellent for carbonyl species while Raman is quite variable [17]. The carbonyl C=O stretching vibration results in strong characteristic IR bands. Raman bands for this vibration are typically moderate to weak with some structures resulting in a strong C=O stretch. This band is easily identified in the IR spectrum because of its intensity and its lack of interference from most other group frequencies.
It was impossible to measure Raman spectrum of the complex - the sample burned even at 1 mW laser power. Only the Raman spectrum of the free ligand was measured and discussed here (see Table 2). The C=O stretching vibration of L appears as a split band at 1746 cm-1 and 1726 cm-1; that split reflects the shoulder structure in the IR spectrum. The C=S stretching vibration appears as a weak band at 1515 cm-1 in the Raman spectrum. Several bands in the Raman spectrum (2973, 2920 and 2877 cm-1) and in the IR spectrum (2963, 2873 and 2791 cm-1) are for stretching vibrations of CH2 in cyclopentane ring. Of the two vibrational bands in the Raman spectrum for n(N1-H) and n(N3-H) there appears only lower frequency band at 3100 cm-1 with a very low intensity.
Table2: ATR and Raman spectral data of free ligand cyclopentanespiro-5-(2-thiohydantoin)
(L)
compound
ATR spectral bands, Raman spectral bands, cm-1 cm-1
3295, 3088, 2961, 2872, S 2788, 2269, 1732, 1576,
2973, 2920, 2877, 2595, 1746, 1726, 1515, 1453, 1440, 1404, 1323, 1196, 1157, 1077, 1013, 948, 905, 750, 613, 503, 373,
o
1559, 1513, 1451, 1436, 1404, 1374, 1316, 1290, 1264, 1232, 1195, 1144, 1068, 1004, 948, 906, 874, 853, 752, 669, 635,
322
L
619
IV. Conclusions: One new metal complex was obtained with Pt(II). This was characterized by elemental analysis and vibrational IR spectroscopy. Cyclopentanespiro-5-(2-thiohydantoin) (L) was study by UV-Vis, IR, ATR and Raman spectroscopy.
Acknowledgements: This work has been supported by the Scientific research Department (NPD) at Plovdiv University contract № NI13HF006/19.03.2013 is gratefully acknowledged.
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