Research Journal of Chemical Sciences ______________________________________________ ISSN 2231-606X Vol. 4(2), 42-48, February (2014) Res. J. Chem. Sci. International Science Congress Association 42 Synthesis and Characterization of caffeine Complexes [M (caf) 4X2] M = Ni(II), Cu(II), Zn(II), Cd(II) X = SCN, CN; caf : caffeine EL Amane Mohamed* and EL Hamdani Hicham Equipe Métallation, complexes moléculaires et applications, Université Moulay Ismail, faculté des sciences, Meknès, BP 11201 Zitoune, 50000 MOROCCO Available online at: www.isca.in, www.isca.me Received 29th December 2013, revised 10th January 2014, accepted 17th February 2014Abstract A series of complexes [M(caf)] where X = cyano,thiocyanato , caf=caffeine ,and M = Ni (II), Cu (II), Zn (II) and Cd (II) were prepared. The prepared complexes were characterized by elemental analysis, conductance measurement, UV-Visible and FT-IR spectral analysis. The conductivity measurements reveal that the complexes are nonelectrolyte. The elemental analysis showed the formation of 1,4,2 (metal, caffeine, cyano or thiocyanato) complexes. The infrared and UV-visible data indicating a monodentate coordination of the four caffeine by N9 nitrogen atom and two cyano or thiocyanato in trans and cis octahedral geometry. Keywords: Cyano, thiocyanato, caffeine, cis, trans-complexes, analysis, infrared spectroscopy , UV-Visible, molar conductivity. Introduction The transition metal ions and their complexes take part for of all the fundamental biologic process oxygen, nitrogen fixation and transformation, coordination of all metabolic reactions, catalysis and bio-photocatalysis, solar energy, molecular electronic etc. Caffeine, theophylline, theobromine they are naturally occurring drugs, Its side-effects include toxicity in excess of consumption, high adrenal simulation, are present in different ratios in the different plant sources for example caffeine is found in coffee, tea, cola muts, mate and guarana. Caffeine is a planar aromatic molecule which leads to the hypothesis that it could very easily form complexes with other planar aromatic molecules such as nucleobases in DNA and several types of anticancer drugs known to intercalate DNA based on their planar structures4,5. This caffeine have the ability to form complexes with metal ions from nd series.Caffeine contains some nitrogen, oxygen atoms involved in coordinative bonds. Some caffeine complexes were found biologically active such as the complexes [PPhMe] [PtCl(caffeine)]; [AcZn(caf)]HO; [Mg(SCN)(caf))], [Cu(pyridine)(caf)] have anticancer, antifungal and antimicrobial effect, a few metal-theophylline complexes [M(TP)(OCN)] have shown significant antitumor activity ,the complex has a formula [M(Th)(caf)(X)(Y)]; [M(Th)2 (Ad)(X)]; [M(Th)(Ad)(X)]; [M(Th)(Y)]; [M(caf)(Y)]; where Ad: adenine and Th: theophylline M2+ = Vo(II); Co(II); Ni(II), Cu(II) and X = SCN- ;Y = OCN- already prepared. In this paper, we prepared and characterized a serie of new complexes [M(caf)] where X=CN, SCN, M= Zn(II), Cd(II), Cu(II), Ni(II) and caf = caffeine. Material and Methods All reageants were purchased commercially and used without further purification, caffeine was purchased from Riedl-deHaen. A.G. the chloride of the appropriate metallic ion MCl,2HO M = Cd(II), Ni(II), Cu (II), Zn (II), KCN and KSCN were obtained from BDH. Instrumental analysis: The IR spectra of the complexes were recorded on a Jasco FT IR-4100 spectrometer in the (4000-400) cm-1 range with KBr pellet technique. UV-Visible spectra were recorded on Shimadzu UV-1800. The elemental analysis of the complexes was carried out by (flash EA 112 Thermo). The molar conductance measurements were conducted using at in DMSO with Hach HQ430d flexi at 25°C. Synthesis of the complexes: An ethanolic solution of 4.10-3mol caffeine (caf) and 2.10-3 mol an aqueous solution of KCN or KSCN were respectively added to an aqueous solution of 1.10-3 mol the metal salts. After constant stirring using appropriate amounts of materials needed as decided by the molar ratio (1:4:2) (M:caf:X), the resulting precipitates were filtered off, washed several times and recrystallized with 1:3 ethanol: water. Then, it dried in an oven at 60°C, similar method was followed to prepare all complexes. Results and Discussion Elemental analysis C, H and metal determination were in good agreement with general formula given for the complexes [M(caf)] as shown in table-1. Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(2), 42-48, February (2014) Res. J. Chem. Sci. International Science Congress Association 43 The prepared complexes were found to be solids, insoluble in water but they were soluble in some organic solvents such as dimethylsulfoxide. The molar conductance values in DMSO obtained from 5-33 cm2 ohm-1 mol-1 indicates the nature of complexes is nonelectrolyte. Infrared spectra: The IR spectral data of the complexes and the free caffeine are given in table- 2-3. Caffeine and theobromine are shown in figure-1, They have a centrosymetric Cs point group. For the caffeine the numbers of vibrations modes are as follows vib = 45A’ +21A’’. Thus the vibrations of the A’ species will be in plane and those the A’’ species will be out of plane. It is known from the literature, that the coordination of metal ions occurs the N9 nitrogen and oxygen carbonyl atoms. In coordination with the N9 nitrogen atom8,12,13 which is accompanied by the elimination of the mirroir plane and by a wole series of changes in the infrared spectrum. The changes in the spectrum of caffeine is observed in the (1700-400) cm-1region corresponding of the stretching and binding vibrations of the carbonyl, imidazole, pyrimidine and methyl fragements in the caffeine9,10. Caffeine theophylline Figure-1 Structure of caffeine and theophylline Table 2-3 summarised the vibrational spectral frequencies of free caffeine ,free thiocyanato , free cyano and their complexes [M(caf)] X = CN,SCN , M = Zn(II), Cd(II), Cu(II), Ni(II). It my be noted that the spectra of the complexes. We can raise a band and medium intensity at the (3500-3400) cm-1 range which can be corresponding to stretching vibration (OH) of hydration water,and two less intense bands at 3100 cm-1 and 2950 cm-1which can be corresponding to (CH) and (CH) respectively9,10,11. In the all complexes (SCN) stretching frequencies are seen between 2162 cm-1 and 2090 cm-1 cprresponding the coordination of thiocyanatothrough S-atom .The frequencies of the (CN) are localized in both spectra in the range 2200 cm-1and 2124 cm-1 , these values indicate the coordination of the cyano ligand7, 12,13. The presence of a single and two strong (CN) and (SCN) for the complexes indicate the existence of inequivalent thiocyanato and cyano in two isomers (cis + trans) in octahedral geometry. A strong absorption bands (CO) for the carbonyl group in the caffeine and their complexes [M(caf)] X=CN-,SCN- for M = Zn(II),Cd(II),Cu(II),Ni(II) are observed in the region (1700-1650) cm-1.This region is a characteristic of aromatic lactones for one and two carbonyl as in the quinone9,10. Caffeine contain two carbonyl vibration in the meta position. The very strong bands observed at 1702 cm-1 and 1662 cm-1 are considered to be due to (CO) asymmetric and (CO) symmetric stretching vibration in caffeine 9,10.The infrared spectra of the complexes [M(caf)] X = CN-,SCN- for Zn(II), Cd(II), Cu(II), Ni(II) are characterized by insignificant schift frequencie for asymmetric (CO) but (CO) symmetric is shifted to lower frequencies by 10 cm-1. The band noticed in the caffeine spectrum at 1548 cm-1 conferring to the vibrations (imidazol) + (pyrimidine) + (HCN) and appeared for the caffeine complexes at 1540 cm-1 table-2,36,7. Table-1 Elemental analysis and molar conductivity of the prepared complexes Complexes [M (caf) 4 (X) 2 ] X = CN- ,SCN Colour Molecular weight °/° Metal °/ C °/° H (ohm - 1 cm 2 mol-1) [Cu (caf)(SCN)] Brown 956.306 (6.64) 6.62 (41.4) 41.6 (4.1) 4.3 10,4 [Zn (caf)(SCN)] white 958.169 (6.82) 6.84 (41.32) 41.41 (4.17) 4.21 14,3 [Ni (caf)(SCN)] green 951.453 (6.16) 6.21 (41.62) 41.73 (4.2) 4.35 12,8 [Cd (caf)(SCN)] white 1005.17 (11.18) 11.3 (39.39) 39.57 (3.97) 4.13 19,1 [Cu (caf)(CN)] bleu 892.306 (7.12) 7.15 (44.37) 44.46 (4.48) 4.57 8.4 [Zn (caf)(CN)] white 894.169 (7.31) 7.53 (44.28) 44.35 (4.47) 4.53 33 [Ni (caf)(CN)] green 887.453 (6.61) 6.7 (44.62) 44.75 (4.5) 4.71 16.2 [Cd (caf) 4 (CN) 2 ] white 941.17 (11.9) 12.1 (42.07)42.14 (4.25) 4.38 5.13 The theoretical values are in parenthesis Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(2), 42-48, February (2014) Res. J. Chem. Sci. International Science Congress Association 44 The band observed in the range (1480-1400) cm-1 for the complexes [M(caf)] belong to the deformation vibrations (CH3) + (HCN) and (CH3) + (CH3) are shifted to lower frequencies see table-2-39,10. Their frequencies noticed in (1445-1400) cm-1 in the complexes binding vibrations and stretching vibrations are due to the connection from the methyl fragment. The deformation and rotation vibrations of fragment pyrimidine and imididazol are usually found at lower frequencies in non affected.The newly vibrations appeared in the spectra of these complexes compared to the caffeine free spectrum are those due to the metal caffeine band (M-N) at 520 cm-1 9,10,11. It should be noted that in the spectra of complexes that no contain direct ocygen-carbonyl binding, were observed spectrum changes in the region corresponding for stretching and bending vibrations fragments (CO), (HCN), (pyrimidine), imidazole, (HCN), (CH) attribued for authors by coordination on the nitrogen N9 atoms of caffeine. Figure-2 IR spectrum of the complex [Zn(caf)(SCN)] Figure-3 IR spectrum of the complex [Cd(caf)(SCN)] Figure-4 IR spectrum of the complex [Cu(caf)(SCN)] Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(2), 42-48, February (2014) Res. J. Chem. Sci. International Science Congress Association 45 Table-2 IR spectral data of the ligand and its complexes (cm-1) [ M(caf)(X)] X = SCN- ; M = Cu(II) , Cd(II) , Ni(II) , Zn(II) and caf = caffeine Free ligands [Cd(caf)4 (X) 2 ] [Ni(caf)4 (X) 2 ] [Zn(caf)4 (X) 2 ] [Cu(caf)4 (X) 2 ] Assigment KSCN Caféine 3400 vs 3400 vs 3465 vs (OH) H2O 3110 m 3100 vs 3111 vs 3109 vs 3111 vs (CH=) 2954 m 2950 vs 2952 vs 2948 vs 2952 vs (CH 3 ) 2160 s 2162 s 2160 s 2158 s (SCN) 2051 s 2100 m 2110 vs 2090 s 2111 vs (SCN) 1700 vs 1695 vs 1700 vs 1694 vs 1695 vs s(CO) 1660 vs 1654 vs 1650 vs 1653 s 1650 vs a(CO) 1600 m 1590 vs 1597 s 1596 s 1608 s (C=C)+(HCN) 1548 s 1542 vs 1540 s 1542 s 1550 s (HCN)+(imidazol)+(pyrimidine) 1470 m 1480 vs 1480 s 1480 s 1500 m (HCN)+(CH3) 1466 m 1446 vs 1448 s 1452 s 1450 m (CH3)+(CH3) 1432 m 1422 vs 1418 s 1428 s 1430 m 1400 vs 1386 s 1388 s 1360 s 1360 vs 1360 s 1360 m 1365 m (HCN)+(imidazol)+(CH3) 1326 w 1325 s 1325 m 1326 m 1330 m (imidazol) + (pyrimidine) 1285 s 1288 vs 1288 m 1284 m 1286 m (pyri) 1237vs 1242 vs 1242 s 1240 s 1237 m (CN) +r(CH3) 1210 w 1216 vs 1212 m 1216 m 1218 w (CH) + r(CH3) 1188 m 1187 s 1187 m 1188 m 1183 m (CH) + r(CH3) 1130 w 1130 m 1138 m 1124 w 1130 w r(CH3) out of plan 1071 s 1070 m 1078 w 1075 w 1074 w (CH3) + (CH) 1025 s 1024 vs 1024 m 1024 w 1038 w (CH3) + (CH) 973 s 976 vs 970 w 973 w 982 w (N-CH3)+r(CH3) +(imidazol) 923 w 924 m 924 w 928 w 930 w (CH) 862 m 860 m 857 s 858 w 857 w (CH3)+(N-CH3)+(C=O) 800 s 797 m 797 w 797 w (pyrimidine) + (C=O) 748 m 760 s 760 w 759 w 761 w (C-S) 700 m 700 w 698 w 698 w 690 w (pyrimidine)+(imidazol) 642 s 642 w 642 w 642 w 654 w (pyrimidine)+(imidazol) 611 s 610 vs 612 w 611 m 610 vs (imidazol) 549 w 549 w 551 w 549 w (M-N) 481 vs 482 s 482 w 478 w 494 w (caffeine) 443 s 443 w 440 w 440 w (M-SCN) 420 vs 425 s 421 w 420 w 424 w r(C=O) vs: very strong, s: strong, m: medium, w: weak Figure-5 IR spectrum of the complex [Cu(caf)(CN)] Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(2), 42-48, February (2014) Res. J. Chem. Sci. International Science Congress Association 46 Table-3 IR spectral data of the ligand and its complexes (cm-1) [M(caf)(X)] X = CN- ; M = Cu+2,cd+2, Ni+2,Zn+2and caf = caffeine Free ligands[Cd(caf)4 (X) 2 ] [Ni(caf)4 (X) 2 ] [Zn(caf)4 (X) 2 ] [Cu(caf)4 (X) 2 ] Assigment KCN caféine 3500 s 3400 s 3500 s 3450 s (OH)H2O 3110 m 3102 s 3100 m 3105 s 3104 s (CH=) 2955 m 2950 s 2952 m 2950 s 2951 m (CH 2137 s (CN) 2088 s* 2200 m 2175 s 2217 m 2124 m (CN) 1700 vs 1693 vs 1694 vs 1695 vs 1695 vs as(CO) 1660 vs 1647 vs 1646 vs 1650 vs 1650 vs a(CO) 1600 m 1594 s 1595 m 1598 s 1604 s (C=C)+(HCN) 1548 1540 vs 1540 s 1540 vs 1540 vs (HCN)+(imidazol) + (primidine) 1478 vs 1478 m 1476 vs 1490 s (HCN)+(CH3) 1466 m 1446 s 1446 m 1446 s 1450 s (CH3)+(CH3) 1432 m 1426 s 1425 s 1428 s 1405 m 1403 s 1400 w 1403 s 1402 s 1360 s 1358 vs 1364 m 1357 s 1360 m (HCN)+(imidazole)+(CH3) 1326 w 1325 s 1327 w 1320 m 1324 w (imidazol) +(pyrimidine) 1285 s 1282 s 1254 w 1280 m 1280 w (pyrimidine) 1237 vs 1234 vs 1240 m 1235 s 1230 w (CN) +r(CH3) 1188 m 1184 s 1185 w 1184 m 1180 w (CH) + r(CH3) 1130 w 1125 w 1130 w 1127 w 1133 w r(CH3) out of plan 1071 s 1070 m 1080 w 1067 w 1074 w (CH3) + (CH) 973 s 968 s 978 m 968 s 978 m (N-CH3)+r(CH3)+(imda) 923 m 924 w 930 w 922 w 924 w (CH) 862 m 858 m 870 w 864 w 840 w (CH3)+(N-CH3)+(C=O) 800 s 798 w 800 w 798 w 800 w (pyrimid) + (C=O) 743 vs 740 vs 747 vs 740 vs 740 vs (pyrimidine) + (imidazol) 642 s 643 w 643 w 643 w 648 w 611 s 610 m 612 m 609 m 610 m (imidazole) 550 w 558 w 548 w 551 w (M-N) 481vs 480 m 480 m 478 s 481 m (caffeine) 438 w 440 s 454 s 440 m ring(pyrimidine) 420 vs 420 m 425 w 420 m 426 m r(C=O) vs: very strong, s: strong, m: medium, w: weak UV-Visible electronic absorption spectra : The electronic absorption spectral of the complexes [Zn(caf)(SCN)] and [Cd(caf)(CN)] have (d10) electronic configuration, which is confirmed absence of d-d transition15. The electronic spectra of these complexes show metal to ligand charge transfer transition (ML) at 272 nm and 271 nm respectively and the values are shown in figure-5, table-4. The electronic spectrum of [Cu(caf)(SCN)] complexe shows band at 621nm and 864 nm which is attributed of the electronic transitions (D)(D) and g(D) g(D) (3)respectively (see figure-5). Therefore, these transitions confirmed that the [Cu(caf)(SCN)] complex has a cis-trans octahedral stereochemistry14. The electronic spectra of [Ni(caf)(CN)] complexe shows electronic transition (F) 1 (F) and (F) (F) at 865 nm and 942 nm (figure-5). Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(2), 42-48, February (2014) Res. J. Chem. Sci. International Science Congress Association 47 Figure-5 UV-visible spectra of the complexes [M(caf)(X)] (M = Ni2+,Cu2+, Cd2+, Zn2+) X=SCN,CN in DMSO Table-4 U.V-visible spectra of free ligand and their complexes 10-3M in DMSO. Compound max (nm) Transitions Cafféine 274  * CN - 426 * SCN - 235 360  * * [Cu(caf)(SCN)] 273 317 369 621 864 Charge transfere M (D) (D) 2 g (D) 1 g (D) [Ni(caf)(CN)] 271 865 942 Charge transfere M L (F) (F) 2 g (F) 2 g (F) [Cd(caf) 4 (CN) 2 ] 271 Charge transfere M L [Zn(caf) 4 (SCN) 2 ] 272 Charge transfere M L Conclusion We have been able to synthesis and characterize complexes [M(caf)(X)] containing caffeine , cyano or thiocyanato ion coordinated with Ni(II), Cu(II), Zn(II) and Cd(II).From the results obtained by elemental analysis , conductance measurement, UV-Visible and infrared spectral indicate the structures of complexes are cis and trans octahedral symmetry. 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