Formation of a new complex in the Zn(HCOO)2-CS(NH2)2-H2O system at 25 °C was established by the solubility method. Its composition was determined to be Zn(HCOO)2 * 2CS(NH2)2.
The bisthiourea zinc formate (BTZF) is an incongruently soluble salt at 25 °C. It has been characterized by X-ray powder diffraction, IR spectroscopy and thermal analysis. The infrared spectra reveal that thiourea forms a zinc-sulfur bond. Thermal decomposition at a temperature of 400 °C yields ZnS.Ustanovljeno je da metodom topljivosti u sustavu Zn(HCOO)2-CS(NH2)2-H2O pri 25 °C nastaje novi kompleksnispoj. Određivanje sastava pokazalo je da se radi o Zn(HCOO)2 * 2CS(NH2)2. Pri 25 °C bistiourea cinkov format (BTZF) neprimjereno je topljiva sol. Spoj je opisan rentgenskom difrakcijom na prahu, IR spektroskopijom i termičkom analizom. U infracrvenom spektru otkrivena je vrpca koja odgovara vezi cink-sumpor. Termički raspad spoja završava kod temperature 400 °C pri čemu zaostaje cinkov sulfid

Petranka P. Petrova

Violeta Z. Vassileva

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Formation and Characterization of Bisthiourea Zinc FormateVioleta Z. Vassilevaa,* and Petranka P. PetrovabaInstitute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. bl. 11,Sofia 1113, BulgariabDepartment of Chemistry, South-West University »Neofit Rilski«, Iv. Mihailov Str. 66, Blagoevgrad 2700, BulgariaRECEIVED MARCH 3, 2004; REVISED NOVEMBER 10, 2004; ACCEPTED DECEMBER 8, 2004Formation of a new complex in the Zn(HCOO)2-CS(NH2)2-H2O system at 25 °C was estab-lished by the solubility method. Its composition was determined to be Zn(HCOO)2  2CS(NH2)2.The bisthiourea zinc formate (BTZF) is an incongruently soluble salt at 25 °C. It has been cha-racterized by X-ray powder diffraction, IR spectroscopy and thermal analysis. The infraredspectra reveal that thiourea forms a zinc-sulfur bond. Thermal decomposition at a temperatureof 400 °C yields ZnS.Keywordsbisthiourea zinc formatesolubility diagramX-rayIR spectroscopyDTA* Author to whom correspondence should be addressed. (E-mail: vzvass@svr.igic.bas.bg)INTRODUCTIONA number of studies on metal coordination compoundsof thiourea with inorganic salts have been reported re-cently. The great interest in these compounds is due totheir non-linear optical properties.1–5 However, papersdealing with the thiourea complexes of metal formatesare comparatively scarce. The existence of a complex salt,Zn(HCOO)2 CS(NH2)2 (1:1), has been reported by Gyory-ova et al.6 It was obtained by a preparative method at hightemperature. The complex salt Cd(HCOO)2  2CS(NH2)2(1:2) is also known, its crystal structure being determin-ed by Nardelli et al.7,8 The latter complex salt was foundin the Cd(HCOO)2-CS(NH2)2-CH3OH system as well.9It was of interest to study the Zn(HCOO)2-CS(NH2)2-H2O system, since a thorough investigation would givemore information on the solid phases formed in this sys-tem at an appropriate temperature.The present paper aims to study the solubility dia-gram of the Zn(HCOO)2-CS(NH2)2-H2O system at 25 °Cand to characterize the new solid phase obtained usingX-ray powder diffraction, IR spectroscopy and thermalanalysis. There are no literature data on solubility in thesystem.EXPERIMENTALMaterialsThe zinc formate was prepared by neutralizing dilute for-mic acid (1:1) with zinc hydroxy carbonate at 70–80 °C. Thesolution was filtered and concentrated. The crystals wereobtained after cooling the solutions to room temperature, thenrecrystallized from distilled water and dried in air. Chemicaland X-ray powder analyses showed that Zn(HCOO)2  2H2O10was obtained. The thiourea and other reagents used were ofanalytical grade.Solubility MethodThe solubility in the Zn(HCOO)2-CS(NH2)2-H2O systemwas studied by the Khlopin method of isothermal decreaseof supersaturation;11 aqueous solutions containing both saltsCROATICA CHEMICA ACTACCACAA 78 (2) 295¿299 (2005)ISSN-0011-1643CCA-3011Original Scientific Papertaken, in different ratios, were prepared at 60–70 °C, thenthey were cooled in a thermostat at 25 °C and stirred untilconstant concentration of the saturated solution, i.e., equi-librium, was achieved. Preliminary experiments showed thatthe equilibrium in the system was attained in about 15–20 h.The suspension was then filtered and the liquid and wet solidphases were analyzed. The concentration of zinc ions inboth phases were determined complexometrically at pH = 10using Eriochrome Black T as indicator.12 The amount ofthiourea was evaluated after oxidation with hydrogen per-oxide to sulfate ions and determination of the latter by thestandard gravimetric analysis.13 The solid phase compositionwas determined by the graphic method of Schreinemakersfor wet residues.14ApparatusX-Ray diffraction analysis was carried out with a DRON-3powder diffractometer using Cu-K radiation with a nickelfilter at a scanning speed of 1 ° min–1 in a 2 diffraction in-terval of 10–60 °. The infrared spectra were recorded on aBruker model IFS 25 Fourier transform interferometer (reso-lution < 2 cm–1) using KBr discs as matrices. Ion exchangeor other reactions with KBr were not observed. Thermal in-vestigations were performed on a Paulik-Paulik Erday MOMOD-102 derivatograph. DTA and TG curves were obtainedin a static air atmosphere with a sample mass of 125 mg, ata heating rate of 10 °C min–1 from ambient temperature to700 °C using a standard corundum crucible. The referencesubstance was pure -Al2O3.RESULTS AND DISCUSSIONSolubility DiagramSolubility data for the Zn(HCOO)2-CS(NH2)2-H2O sys-tem at 25 °C are listed in Table I, and the solubility phasediagram is shown in Figure 1. They are expressed in massfraction, w/%. Three crystallization fields are distinguish-ed in this diagram: wide fields of Zn(HCOO)2  2H2Oand CS(NH2)2, and a narrow crystallization field of thecomplex salt Zn(HCOO)2  2CS(NH2)2 (1:2). The complexcompound crystallizes from solutions containing 15.90 %zinc formate and 25.55 % thiourea up to solutions con-taining 18.32 % zinc formate and 36.08 % thiourea. Thesolubility diagram data show unambiguously that at 25 °Ca complex salt (composition 1:2) was obtained. The com-pound reported by Gyoryova et al. was synthesized bythe reaction in water solutions at 40–80 °C using zincformate and thiourea in stoichiometric ratios.6296 V. Z. VASSILEVA AND P. P. PETROVACroat. Chem. Acta 78 (2) 295–299 (2005)TABLE I. Solubility in the Zn(HCOO)2-CS(NH2)2-H2O system at 25 °CLiquid phase, w / % Wet solid phase, w / % Solid phaseZn(HCOO)2 CS(NH2)2 Zn(HCOO)2 CS(NH2)25.38 – – – Zn(HCOO)2  2H2O8.23 9.85 60.92 2.83 Zn(HCOO)2  2H2O12.01 19.07 65.07 4.74 Zn(HCOO)2  2H2O15.32 25.45 63.12 7.11 Zn(HCOO)2  2H2O15.90 25.55 51.93 24.45 eutonics15.82 25.92 38.95 42.25 Zn(HCOO)2  2CS(NH2)216.07 30.18 37.03 41.78 Zn(HCOO)2  2CS(NH2)217.09 33.22 39.87 44.79 Zn(HCOO)2  2CS(NH2)218.51 36.00 38.01 44.62 Zn(HCOO)2  2CS(NH2)218.32 36.08 23.27 66.93 eutonics18.07 35.82 6.15 78.53 CS(NH2)215.09 32.12 5.24 76.20 CS(NH2)210.93 28.00 4.75 71.32 CS(NH2)25.29 20.67 2.63 67.05 CS(NH2)2– 13.39 – – CS(NH2)20 25 50 75 100Zn(HCOO)2H O2CS(NH )2 2Zn(HCOO) . 2H O2 2Zn(HCOO) . 2CS(NH )2 2 2255075Figure 1. Solubility diagram of the Zn(HCOO)2-CS(NH2)2-H2Osystem at 25 °C (w/%).The solid phases were isolated from the system byfiltering, washing with alcohol and drying in air, and thenidentified by chemical analysis, X-ray powder diffraction,IR spectroscopy and DTA.Zn(HCOO)22CS(NH2)2 forms colorless crystals. Che-mical analysis shows 50.67 % Zn(HCOO)2 and 49.68 %CS(NH2)2, (theoretical composition: 50.51 % and 49.49 %,respectively).X-Ray and IR SpectroscopyX-ray powder diffraction analysis confirms the results ofthe solubility diagram data, indicating the formation ofthree solid phases in the system. The diffraction patternof BTZF differs from those of Zn(HCOO)2  2H2O10 andCS(NH2)2.15 The d-spacings and relative intensities of 50reflections are given in Table II.Frequencies, assignment and relative intensities ofthe bands of the formate groups and thiourea in the in-frared spectra of BTZF in the region 4000–400 cm–1 aresummarized in Table III and are shown in Figure 2. Theassignments of the bands of HCOO– were done by anal-ogy to the studies on metal formate (simple and doublesalts)16–20 and those of CS(NH2)2 – to the studies on me-tal thiourea complexes.1,2,21–23Crystal structures of a number of metal thioureacomplexes have been determined by X-ray diffraction:in all the cases, only sulfur-metal bonds were found tobe present.24–30 In the crystal structure of Cd(HCOO)2 2CS(NH2)2 (1:2), a Cd-S bond was established as well.8According to literature data,1,2,21–23 differences betweenthe thiourea itself and all its metal complexes are con-fined to two bands only. Upon complex formation, theband of thiourea at 1412 cm–1 is split and that at 730cm–1 is both split and shifted to a lower frequency. Thesebands corresponds to the antisymmetric and symmetricC-S stretching vibrations and they split because of theformation of a metal-sulfur bond.22It can be seen from Table III and Figure 2 that theantisymmetric C-S stretching vibrations are split into twobands at 1431 and 1402 cm–1 and the symmetric C-Sstretching vibrations are split into two bands at 715 and707 cm–1 (shoulder) and shifted to lower frequencies.BISTHIOUREA ZINC FORMATE 297Croat. Chem. Acta 78 (2) 295–299 (2005)TABLE II. X-ray diffraction data of Zn(HCOO)2  2CS(NH2)2dobs /Å I/Io dobs /Å I/Io6.177 100 2.239 296.054 84 2.172 35.744 60 2.131 105.594 90 2.083 124.910 19 2.060 54.492 60 2.044 104.303 10 2.008 74.161 15 1.967 143.615 90 1.948 53.522 11 1.907 113.475 15 1.883 113.395 45 1.845 43.193 7 1.802 83.091 84 1.748 83.060 57 1.718 133.015 75 1.709 152.873 33 1.686 62.782 60 1.672 42.736 7 1.645 82.670 17 1.622 32.602 10 1.591 42.458 14 1.597 32.385 5 1.565 32.348 13 1.543 92.310 9 1.525 3TABLE III. Infrared spectral data (cm–1) and band assignments forZn(HCOO)2  2CS(NH2)2Wavenumber / cm–1 Assignment3428 s as N-H stretch3360 sh3317 m3270 sh s N-H stretch3127 s2925 w2846 m1 C-H stretch2745 w2703 sh25 HCOO–1671 s1638 vs NH21620 vvs1602 vs4 as COO stretch1522 m as C-N1431 w1402 mas C-S1384 m 5 in-plane C-H bend1327 s 2 sym COO stretch1115 w s C-N1075 vw 6 out of plane C-H bend781 m 3 sym O-C-O deformation715 m707 shs C-S640 m t NH2581 m487 m414 was N-C-N defs S-C-N defs N-C-N defThese spectral data are an indication of the existence ofthe zinc-sulfur bond in bisthiourea zinc formate.The high frequency N-H absorption bands in the re-gion 3100–3400 cm–1 in the thiourea spectrum were notshifted to a lower frequency upon formation of the metal--thiourea complex, indicating that nitrogen to zinc bondsare not present and that the bonding must be betweensulfur and zinc atoms.23 The bands of BTZF in this re-gion were not shifted to a lower frequency according tothe literature data of metal thiourea complexes.1,2,21–23Thermal AnalysisThe thermal behavior of BTZF has been studied by TGand DTA and the derivatogram is presented in Figure 3.The results coincide with those of analogous compoundsof thiourea with inorganic salts:1,6,9,31–33 the melting takesplace at the beginning, followed by complicated proces-ses of thermal decomposition.Under our experimental conditions, the BTZF is sta-ble up to about 100 °C. Melting of the compound is ob-served at 120–140 °C. Melting is registered on the DTAcurve with an endothermal effect at about 130 °C (thereis no mass loss on the TG curve).Thermal decomposition of the melting salt begins atabout 150–160 °C. The two processes, decomposition ofthe complex salt and decomposition of thiourea and zincformate, occur simultaneously. For this reason, the ther-mal decomposition of BTZF is complicated and producesendo- and exothermal effects.The X-ray diffraction of the sample obtained afterheating at 400 °C for several hours shows ZnS.34 TheZnS is unstable in the air at a higher temperature and ox-idized by oxygen from the air to ZnO. According to theX-ray diffraction, the sample obtained after heating at650 °C is ZnO.35298 V. Z. VASSILEVA AND P. P. PETROVACroat. Chem. Acta 78 (2) 295–299 (2005)Figure 2. IR spectra of Zn(HCOO)2  2CS(NH2)2in the 4000–400cm–1 region.Figure 3. TG, DTA and DTG curves of Zn(HCOO)2  2CS(NH2)2.CONCLUSIONThe solubility diagram of the Zn(HCOO)2-CS(NH2)2-H2Osystem at 25 °C has been investigated, showing the exis-tence of a complex salt of the composition Zn(HCOO)2 2CS(NH2)2, which is incongruently soluble at this tem-perature.The X-ray diffraction data show that three solid pha-ses were obtained in the system. The functional groupspresent in the BTZF were confirmed by IR spectral anal-ysis. It is also evident from the IR studies that thiourea isbonded to zinc formate through sulfur. The DTA and TGdata were in agreement with those of similar metal thio-urea complexes, including melting and complicated pro-cesses of thermal decomposition. ZnS was obtained at atemperature of 400 °C.REFERENCES1. P. A. Angeli Mary and S. Dhanuskodi, Cryst. Res. Technol.36 (2001) 1231–1237.2. M. Oussaid, P. Becker, and C. Carabatos-Nedelec, Phys.Stat. Sol.(b), 207 (1998) 499–507.3. H. O. Marcy, L. F. Warren, M. S. Webb, C. A. Ebbers, S. P.Velsko, G. C. Kennedy, and G. C. Catella, Appl. Opt. 31(1992) 5051–5060.4. V. Venkataramanan, C. K. Subramanian, and H. L. J. Bhat,App. Phys. 77 (1995) 6049–6051.5. G. Xing, M. Jiang, Z. Shao, and D. Xu, Chin. Phys. Lasers14 (1987) 302–308.6. K. Gyeryova, V. Balek, and V. Zelenak, Thermochim. Acta234 (1994) 221–232.7. M. Nardelli, G. G. Fava, and P. Boldrini, Gazz. Chim. Ital.92 (1962) 1392–1400.8. M. Nardelli, G. G. Fava, and P. Boldrini, Acta Crystallogr.18 (1965) 618–623.9. M. Stoev, S. Ruseva, and B. Keremidchieva, Monatsh. Chem.125 (1994) 1215–1221.10. N. Burger and H. Fuess, Z. Krist. 145 (1977) 346–355.11. V. G. Khlopin, Izbrannye Trudy (Selected Works), Vol. 1.,Izd. Akad. Nauk SSSR, Moscow, Leningrad 1957, p. 162.12. G. Schwarzenbah and G. Flascka, KomplexometricheskoeTitrovanie, Khimia, Moskwa, 1970, p.161.13. I. Lysyj and J. E. Zarembo, Anal. Chem. 30 (1958) 428–430.14. a) F. A. H. Schreinemakers, Z. Phys. Chem. 11 (1893) 76–81; b) F. A. H. Schreinemakers, Z. Phys. Chem. 55 (1906)73–79.15. JSPDS, Powder Diffraction File, Vol. 31, Card 1934.16. J. D. Donaldson, J. F. Knifton, and S. D. Ross, Spectrochim.Acta 20 (1964) 847–851.17. G. D. Tewari, V. P. Tayal, D. P. Khandelwal, and. H. D. Bist,Appl. Spectrosc. 36 (1982) 441–445.18. P. Baraldi, Spectrochim. Acta A35 (1979) 1003–1007.19. A. M. Heyns, J. Mol. Struct. 127 (1985) 9–20.20. S. Abraham, G. Aruldhas, and G. Keresztury, J. Solid StateChem. 95 (1991) 443–446.21. A. Yamaguchi, R. B. Penland, S. Mizushima, T. G. Lane,Columba Curran, and T. J. Quagliano, J. Am. Chem. Soc. 80(1958) 527–529.22. K. Swaminathan and H. M. N. H Irving, J. Inorg. Nucl. Chem.26 (1964) 1291–1294.23. K. Nakamoto, Infrared and Raman Spectra of Inorganic andCoordination Compounds, Fourth Edn. J. Wiley and Sons,New York, 1986, p. 269.24. N. R. Kunchur and M. R. Truter, J. Chem. Soc. (1958)3478–3484.25. A. Lopez-Castro and M. R. Truter, J. Chem. Soc. (1963)1309–1317.26. C. B. Knobler, Y. Okaya, and R. Pepinski, Z. Krist. 111(1959) 385–397.27. M. Nardelli and G. Fava, Acta Crystallogr. 12 (1959) 727–730.28. G. V. Romanenko, L. I. Miachina, and S. V. Larionov, Zh.Struct. Chim. 42 (2001) 387–391.29. R. Vega, A. Lopez-Castro, and R. Marquez, Acta Crystal-logr. 34B (1978) 2297–2299.30. R. Petrova, S. Bakarrdjieva, and T. Todorov, Z. Krist. 215(2000) 118–121.31. P. L. Procenko, A. G. Glinina, and G. P. Procenko, Zh. Neorg.Chim. 16 (1971) 3305–3311.32. M. P. B. Attard, J. O. Hill, R. J. Magee, S. Prakash, and M.N. Sastri, J. Thermal Anal. 31 (1986) 407–420.33. G. Liptay, Atlas of Thermoanalytical Curves, Vol. 1, N 43,Akademiai Kiodo, Budapest, 1977.34. JSPDS, Powder Diffraction File, Vol. 5, Card 566.35. JSPDS, Powder Diffraction File, Vol. 36, Card 1451.SA@ETAKNastajanje i karakterizacija bistiourea cinkovoga formataVioleta Z. Vassileva i Petranka P. PetrovaUstanovljeno je da metodom topljivosti u sustavu Zn(HCOO)2-CS(NH2)2-H2O pri 25 °C nastaje novi kom-pleksni spoj. Odre|ivanje sastava pokazalo je da se radi o Zn(HCOO)2  2CS(NH2)2. Pri 25 °C bistiourea cinkovformat (BTZF) neprimjereno je topljiva sol. Spoj je opisan rentgenskom difrakcijom na prahu, IR spektroskopi-jom i termi~kom analizom. U infracrvenom spektru otkrivena je vrpca koja odgovara vezi cink-sumpor. Termi-~ki raspad spoja zavr{ava kod temperature 400 °C pri ~emu zaostaje cinkov sulfid.BISTHIOUREA ZINC FORMATE 299Croat. Chem. Acta 78 (2) 295–299 (2005)

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Nastajanje i karakterizacija bistiourea cinkovoga formata

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Formation and Characterization of Bisthiourea Zinc FormateVioleta Z. Vassilevaa,* and Petranka P. PetrovabaInstitute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. bl. 11,Sofia 1113, BulgariabDepartment of Chemistry, South-West University »Neofit Rilski«, Iv. Mihailov Str. 66, Blagoevgrad 2700, BulgariaRECEIVED MARCH 3, 2004; REVISED NOVEMBER 10, 2004; ACCEPTED DECEMBER 8, 2004Formation of a new complex in the Zn(HCOO)2-CS(NH2)2-H2O system at 25 °C was estab-lished by the solubility method. Its composition was determined to be Zn(HCOO)2  2CS(NH2)2.The bisthiourea zinc formate (BTZF) is an incongruently soluble salt at 25 °C. It has been cha-racterized by X-ray powder diffraction, IR spectroscopy and thermal analysis. The infraredspectra reveal that thiourea forms a zinc-sulfur bond. Thermal decomposition at a temperatureof 400 °C yields ZnS.Keywordsbisthiourea zinc formatesolubility diagramX-rayIR spectroscopyDTA* Author to whom correspondence should be addressed. (E-mail: vzvass@svr.igic.bas.bg)INTRODUCTIONA number of studies on metal coordination compoundsof thiourea with inorganic salts have been reported re-cently. The great interest in these compounds is due totheir non-linear optical properties.1–5 However, papersdealing with the thiourea complexes of metal formatesare comparatively scarce. The existence of a complex salt,Zn(HCOO)2 CS(NH2)2 (1:1), has been reported by Gyory-ova et al.6 It was obtained by a preparative method at hightemperature. The complex salt Cd(HCOO)2  2CS(NH2)2(1:2) is also known, its crystal structure being determin-ed by Nardelli et al.7,8 The latter complex salt was foundin the Cd(HCOO)2-CS(NH2)2-CH3OH system as well.9It was of interest to study the Zn(HCOO)2-CS(NH2)2-H2O system, since a thorough investigation would givemore information on the solid phases formed in this sys-tem at an appropriate temperature.The present paper aims to study the solubility dia-gram of the Zn(HCOO)2-CS(NH2)2-H2O system at 25 °Cand to characterize the new solid phase obtained usingX-ray powder diffraction, IR spectroscopy and thermalanalysis. There are no literature data on solubility in thesystem.EXPERIMENTALMaterialsThe zinc formate was prepared by neutralizing dilute for-mic acid (1:1) with zinc hydroxy carbonate at 70–80 °C. Thesolution was filtered and concentrated. The crystals wereobtained after cooling the solutions to room temperature, thenrecrystallized from distilled water and dried in air. Chemicaland X-ray powder analyses showed that Zn(HCOO)2 2H2O10was obtained. The thiourea and other reagents used were ofanalytical grade.Solubility MethodThe solubility in the Zn(HCOO)2-CS(NH2)2-H2O systemwas studied by the Khlopin method of isothermal decreaseof supersaturation;11 aqueous solutions containing both saltsCROATICA CHEMICA ACTACCACAA 78 (2) 295¿299 (2005)ISSN-0011-1643CCA-3011Original Scientific Papertaken, in different ratios, were prepared at 60–70 °C, thenthey were cooled in a thermostat at 25 °C and stirred untilconstant concentration of the saturated solution, i.e., equi-librium, was achieved. Preliminary experiments showed thatthe equilibrium in the system was attained in about 15–20 h.The suspension was then filtered and the liquid and wet solidphases were analyzed. The concentration of zinc ions inboth phases were determined complexometrically at pH = 10using Eriochrome Black T as indicator.12 The amount ofthiourea was evaluated after oxidation with hydrogen per-oxide to sulfate ions and determination of the latter by thestandard gravimetric analysis.13 The solid phase compositionwas determined by the graphic method of Schreinemakersfor wet residues.14ApparatusX-Ray diffraction analysis was carried out with a DRON-3powder diffractometer using Cu-K radiation with a nickelfilter at a scanning speed of 1 ° min–1 in a 2 diffraction in-terval of 10–60 °. The infrared spectra were recorded on aBruker model IFS 25 Fourier transform interferometer (reso-lution < 2 cm–1) using KBr discs as matrices. Ion exchangeor other reactions with KBr were not observed. Thermal in-vestigations were performed on a Paulik-Paulik Erday MOMOD-102 derivatograph. DTA and TG curves were obtainedin a static air atmosphere with a sample mass of 125 mg, ata heating rate of 10 °C min–1 from ambient temperature to700 °C using a standard corundum crucible. The referencesubstance was pure -Al2O3.RESULTS AND DISCUSSIONSolubility DiagramSolubility data for the Zn(HCOO)2-CS(NH2)2-H2O sys-tem at 25 °C are listed in Table I, and the solubility phasediagram is shown in Figure 1. They are expressed in massfraction, w/%. Three crystallization fields are distinguish-ed in this diagram: wide fields of Zn(HCOO)2  2H2Oand CS(NH2)2, and a narrow crystallization field of thecomplex salt Zn(HCOO)2 2CS(NH2)2 (1:2). The complexcompound crystallizes from solutions containing 15.90 %zinc formate and 25.55 % thiourea up to solutions con-taining 18.32 % zinc formate and 36.08 % thiourea. Thesolubility diagram data show unambiguously that at 25 °Ca complex salt (composition 1:2) was obtained. The com-pound reported by Gyoryova et al. was synthesized bythe reaction in water solutions at 40–80 °C using zincformate and thiourea in stoichiometric ratios.6296 V. Z. VASSILEVA AND P. P. PETROVACroat. Chem. Acta 78 (2) 295–299 (2005)TABLE I. Solubility in the Zn(HCOO)2-CS(NH2)2-H2O system at 25 °CLiquid phase, w / % Wet solid phase, w / % Solid phaseZn(HCOO)2 CS(NH2)2 Zn(HCOO)2 CS(NH2)25.38 – – – Zn(HCOO)2  2H2O8.23 9.85 60.92 2.83 Zn(HCOO)2  2H2O12.01 19.07 65.07 4.74 Zn(HCOO)2  2H2O15.32 25.45 63.12 7.11 Zn(HCOO)2  2H2O15.90 25.55 51.93 24.45 eutonics15.82 25.92 38.95 42.25 Zn(HCOO)2  2CS(NH2)216.07 30.18 37.03 41.78 Zn(HCOO)2  2CS(NH2)217.09 33.22 39.87 44.79 Zn(HCOO)2  2CS(NH2)218.51 36.00 38.01 44.62 Zn(HCOO)2  2CS(NH2)218.32 36.08 23.27 66.93 eutonics18.07 35.82 6.15 78.53 CS(NH2)215.09 32.12 5.24 76.20 CS(NH2)210.93 28.00 4.75 71.32 CS(NH2)25.29 20.67 2.63 67.05 CS(NH2)2– 13.39 – – CS(NH2)20 25 50 75 100Zn(HCOO)2H O2 CS(NH )2 2Zn(HCOO) . 2H O2 2Zn(HCOO) . 2CS(NH )2 2 2255075Figure 1. Solubility diagram of the Zn(HCOO)2-CS(NH2)2-H2Osystem at 25 °C (w/%).The solid phases were isolated from the system byfiltering, washing with alcohol and drying in air, and thenidentified by chemical analysis, X-ray powder diffraction,IR spectroscopy and DTA.Zn(HCOO)22CS(NH2)2 forms colorless crystals. Che-mical analysis shows 50.67 % Zn(HCOO)2 and 49.68 %CS(NH2)2, (theoretical composition: 50.51 % and 49.49 %,respectively).X-Ray and IR SpectroscopyX-ray powder diffraction analysis confirms the results ofthe solubility diagram data, indicating the formation ofthree solid phases in the system. The diffraction patternof BTZF differs from those of Zn(HCOO)2  2H2O10 andCS(NH2)2.15 The d-spacings and relative intensities of 50reflections are given in Table II.Frequencies, assignment and relative intensities ofthe bands of the formate groups and thiourea in the in-frared spectra of BTZF in the region 4000–400 cm–1 aresummarized in Table III and are shown in Figure 2. Theassignments of the bands of HCOO– were done by anal-ogy to the studies on metal formate (simple and doublesalts)16–20 and those of CS(NH2)2 – to the studies on me-tal thiourea complexes.1,2,21–23Crystal structures of a number of metal thioureacomplexes have been determined by X-ray diffraction:in all the cases, only sulfur-metal bonds were found tobe present.24–30 In the crystal structure of Cd(HCOO)2 2CS(NH2)2 (1:2), a Cd-S bond was established as well.8According to literature data,1,2,21–23 differences betweenthe thiourea itself and all its metal complexes are con-fined to two bands only. Upon complex formation, theband of thiourea at 1412 cm–1 is split and that at 730cm–1 is both split and shifted to a lower frequency. Thesebands corresponds to the antisymmetric and symmetricC-S stretching vibrations and they split because of theformation of a metal-sulfur bond.22It can be seen from Table III and Figure 2 that theantisymmetric C-S stretching vibrations are split into twobands at 1431 and 1402 cm–1 and the symmetric C-Sstretching vibrations are split into two bands at 715 and707 cm–1 (shoulder) and shifted to lower frequencies.BISTHIOUREA ZINC FORMATE 297Croat. Chem. Acta 78 (2) 295–299 (2005)TABLE II. X-ray diffraction data of Zn(HCOO)2  2CS(NH2)2dobs /Å I/Io dobs /Å I/Io6.177 100 2.239 296.054 84 2.172 35.744 60 2.131 105.594 90 2.083 124.910 19 2.060 54.492 60 2.044 104.303 10 2.008 74.161 15 1.967 143.615 90 1.948 53.522 11 1.907 113.475 15 1.883 113.395 45 1.845 43.193 7 1.802 83.091 84 1.748 83.060 57 1.718 133.015 75 1.709 152.873 33 1.686 62.782 60 1.672 42.736 7 1.645 82.670 17 1.622 32.602 10 1.591 42.458 14 1.597 32.385 5 1.565 32.348 13 1.543 92.310 9 1.525 3TABLE III. Infrared spectral data (cm–1) and band assignments forZn(HCOO)2  2CS(NH2)2Wavenumber / cm–1 Assignment3428 s as N-H stretch3360 sh3317 m3270 sh s N-H stretch3127 s2925 w2846 m1 C-H stretch2745 w2703 sh25 HCOO–1671 s1638 vs NH21620 vvs1602 vs4 as COO stretch1522 m as C-N1431 w1402 mas C-S1384 m 5 in-plane C-H bend1327 s 2 sym COO stretch1115 w s C-N1075 vw 6 out of plane C-H bend781 m 3 sym O-C-O deformation715 m707 shs C-S640 m t NH2581 m487 m414 was N-C-N defs S-C-N defs N-C-N defThese spectral data are an indication of the existence ofthe zinc-sulfur bond in bisthiourea zinc formate.The high frequency N-H absorption bands in the re-gion 3100–3400 cm–1 in the thiourea spectrum were notshifted to a lower frequency upon formation of the metal--thiourea complex, indicating that nitrogen to zinc bondsare not present and that the bonding must be betweensulfur and zinc atoms.23 The bands of BTZF in this re-gion were not shifted to a lower frequency according tothe literature data of metal thiourea complexes.1,2,21–23Thermal AnalysisThe thermal behavior of BTZF has been studied by TGand DTA and the derivatogram is presented in Figure 3.The results coincide with those of analogous compoundsof thiourea with inorganic salts:1,6,9,31–33 the melting takesplace at the beginning, followed by complicated proces-ses of thermal decomposition.Under our experimental conditions, the BTZF is sta-ble up to about 100 °C. Melting of the compound is ob-served at 120–140 °C. Melting is registered on the DTAcurve with an endothermal effect at about 130 °C (thereis no mass loss on the TG curve).Thermal decomposition of the melting salt begins atabout 150–160 °C. The two processes, decomposition ofthe complex salt and decomposition of thiourea and zincformate, occur simultaneously. For this reason, the ther-mal decomposition of BTZF is complicated and producesendo- and exothermal effects.The X-ray diffraction of the sample obtained afterheating at 400 °C for several hours shows ZnS.34 TheZnS is unstable in the air at a higher temperature and ox-idized by oxygen from the air to ZnO. According to theX-ray diffraction, the sample obtained after heating at650 °C is ZnO.35298 V. Z. VASSILEVA AND P. P. PETROVACroat. Chem. Acta 78 (2) 295–299 (2005)Figure 2. IR spectra of Zn(HCOO)2  2CS(NH2)2in the 4000–400cm–1 region.Figure 3. TG, DTA and DTG curves of Zn(HCOO)2  2CS(NH2)2.CONCLUSIONThe solubility diagram of the Zn(HCOO)2-CS(NH2)2-H2Osystem at 25 °C has been investigated, showing the exis-tence of a complex salt of the composition Zn(HCOO)2 2CS(NH2)2, which is incongruently soluble at this tem-perature.The X-ray diffraction data show that three solid pha-ses were obtained in the system. The functional groupspresent in the BTZF were confirmed by IR spectral anal-ysis. It is also evident from the IR studies that thiourea isbonded to zinc formate through sulfur. The DTA and TGdata were in agreement with those of similar metal thio-urea complexes, including melting and complicated pro-cesses of thermal decomposition. ZnS was obtained at atemperature of 400 °C.REFERENCES1. P. A. Angeli Mary and S. Dhanuskodi, Cryst. Res. Technol.36 (2001) 1231–1237.2. M. Oussaid, P. Becker, and C. Carabatos-Nedelec, Phys.Stat. Sol.(b), 207 (1998) 499–507.3. H. O. Marcy, L. F. Warren, M. S. Webb, C. A. Ebbers, S. P.Velsko, G. C. Kennedy, and G. C. Catella, Appl. Opt. 31(1992) 5051–5060.4. V. Venkataramanan, C. K. Subramanian, and H. L. J. Bhat,App. Phys. 77 (1995) 6049–6051.5. G. Xing, M. Jiang, Z. Shao, and D. Xu, Chin. Phys. Lasers14 (1987) 302–308.6. K. Gyeryova, V. Balek, and V. Zelenak, Thermochim. Acta234 (1994) 221–232.7. M. Nardelli, G. G. Fava, and P. Boldrini, Gazz. Chim. Ital.92 (1962) 1392–1400.8. M. Nardelli, G. G. Fava, and P. Boldrini, Acta Crystallogr.18 (1965) 618–623.9. M. Stoev, S. Ruseva, and B. Keremidchieva,Monatsh. Chem.125 (1994) 1215–1221.10. N. Burger and H. Fuess, Z. Krist. 145 (1977) 346–355.11. V. G. Khlopin, Izbrannye Trudy (Selected Works), Vol. 1.,Izd. Akad. Nauk SSSR, Moscow, Leningrad 1957, p. 162.12. G. Schwarzenbah and G. Flascka, KomplexometricheskoeTitrovanie, Khimia, Moskwa, 1970, p.161.13. I. Lysyj and J. E. Zarembo, Anal. Chem. 30 (1958) 428–430.14. a) F. A. H. Schreinemakers, Z. Phys. Chem. 11 (1893) 76–81; b) F. A. H. Schreinemakers, Z. Phys. Chem. 55 (1906)73–79.15. JSPDS, Powder Diffraction File, Vol. 31, Card 1934.16. J. D. Donaldson, J. F. Knifton, and S. D. Ross, Spectrochim.Acta 20 (1964) 847–851.17. G. D. Tewari, V. P. Tayal, D. P. Khandelwal, and. H. D. Bist,Appl. Spectrosc. 36 (1982) 441–445.18. P. Baraldi, Spectrochim. Acta A35 (1979) 1003–1007.19. A. M. Heyns, J. Mol. Struct. 127 (1985) 9–20.20. S. Abraham, G. Aruldhas, and G. Keresztury, J. Solid StateChem. 95 (1991) 443–446.21. A. Yamaguchi, R. B. Penland, S. Mizushima, T. G. Lane,Columba Curran, and T. J. Quagliano, J. Am. Chem. Soc. 80(1958) 527–529.22. K. Swaminathan and H.M. N. H Irving, J. Inorg. Nucl. Chem.26 (1964) 1291–1294.23. K. Nakamoto, Infrared and Raman Spectra of Inorganic andCoordination Compounds, Fourth Edn. J. Wiley and Sons,New York, 1986, p. 269.24. N. R. Kunchur and M. R. Truter, J. Chem. Soc. (1958)3478–3484.25. A. Lopez-Castro and M. R. Truter, J. Chem. Soc. (1963)1309–1317.26. C. B. Knobler, Y. Okaya, and R. Pepinski, Z. Krist. 111(1959) 385–397.27. M. Nardelli and G. Fava, Acta Crystallogr. 12 (1959) 727–730.28. G. V. Romanenko, L. I. Miachina, and S. V. Larionov, Zh.Struct. Chim. 42 (2001) 387–391.29. R. Vega, A. Lopez-Castro, and R. Marquez, Acta Crystal-logr. 34B (1978) 2297–2299.30. R. Petrova, S. Bakarrdjieva, and T. Todorov, Z. Krist. 215(2000) 118–121.31. P. L. Procenko, A. G. Glinina, and G. P. Procenko, Zh. Neorg.Chim. 16 (1971) 3305–3311.32. M. P. B. Attard, J. O. Hill, R. J. Magee, S. Prakash, and M.N. Sastri, J. Thermal Anal. 31 (1986) 407–420.33. G. Liptay, Atlas of Thermoanalytical Curves, Vol. 1, N 43,Akademiai Kiodo, Budapest, 1977.34. JSPDS, Powder Diffraction File, Vol. 5, Card 566.35. JSPDS, Powder Diffraction File, Vol. 36, Card 1451.SA@ETAKNastajanje i karakterizacija bistiourea cinkovoga formataVioleta Z. Vassileva i Petranka P. PetrovaUstanovljeno je da metodom topljivosti u sustavu Zn(HCOO)2-CS(NH2)2-H2O pri 25 °C nastaje novi kom-pleksni spoj. Odre|ivanje sastava pokazalo je da se radi o Zn(HCOO)2  2CS(NH2)2. Pri 25 °C bistiourea cinkovformat (BTZF) neprimjereno je topljiva sol. Spoj je opisan rentgenskom difrakcijom na prahu, IR spektroskopi-jom i termi~kom analizom. U infracrvenom spektru otkrivena je vrpca koja odgovara vezi cink-sumpor. Termi-~ki raspad spoja zavr{ava kod temperature 400 °C pri ~emu zaostaje cinkov sulfid.BISTHIOUREA ZINC FORMATE 299Croat. Chem. Acta 78 (2) 295–299 (2005)

Nastajanje i karakterizacija bistiourea cinkovoga formata

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