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Formation of Novel Amino Vic-dioxime Complexes of Cu(II), Ni(II), Co(II) and Cd(II) of 1,3- Dioxalane Groups Containing the Oxime Moiety: Thermal, Magnetic and Spectral Studies.

Byline: SIBEL DUMAN AND MEMET SEKERCI

Summary:

A novel substituted vic-dioxime ligand containing the amino group, N,N'-[2,2'-{ethane-1,2-di-yl-bis(oxy)bis(2,1-phenylene)}bis(N'-hydroxy)-2-(hydroxyimino)acetimidamide] (L1) has been prepared from 1,2-bis(o-aminophenoxy)ethane, anti-chloroglyoxime. The new complexes derived from L1 with Cu(II), Ni(II), Co(II) and Cd(II) complexes of 6,7-O-Cyclopentlydine-1- amino-4-azaheptane (L2) have been reacted at 60-65 oC temperature. The ligand1:metal:ligand2 ratio of these complexes have been found to be 1:2:2. The new Cu(II), Ni(II), Co(II) and Cd(II) complexes of these ligands are proposed to be octahedral. These new complexes have been characterized by elemental analyses, molar conductivity, magnetic susceptibility, IR, 1H-NMR, UV- Vis spectra and TGA techniques.

Keywords: Vic-dioxime, Transition metal complexes, amine.

Introduction

Vic-dioximes and their complexes constitute an important class of compounds having versatile reactivities [1]. Oxime metal chelates are biologically active and are reported to posses semiconducting properties [2,3]. The substitution of the vic-dioxime moiety affects the structure and stability of the complex [4]. Compounds containing the 1,3- dioxalane groups are used as solvents, additive compounds, and corrosion retardants, while polymers containing 1,3-dioxalane groups exhibit semicond- ucting behavior [5,6].

In the present study, new amino vic-dioxime complexes derived from N,N'-[2,2'-{ethane-1,2-di-yl- bis(oxy)bis(2,1-phenylene)}bis(N'-hydroxy)-2- (hydroxyimino)acetimidamide] (L1) with Cu(II), Ni(II), Co(II) and Cd(II) complexes of 6,7-O- cyclopentilydine-1-amino-4-azaheptane (L2) used as metal salts have been prepared and characterized by electronic, infrared, molar conductivity, magnetic and 1H-NMR spectral measurements in addition to elemental and thermo gravimetrical analyses. The data revealed same geometries around the metal ions, depending on both the ligand and metal ions.

Results and Discussion

The ligand used for this work, L1 contains amino and vic-dioximes groups. Its synthesis was accomplished in 82.77% yield by the reaction of 1,2- bis(o-aminophenoxy)ethane and anti-chloroglyoxime in ethanol. The impurities were checked by L1 gives dinuclear complexes [L1Cu2L2 (OH) ]*3H O, [L1Ni2L2 (OH) ]*3H O, [L1Co L2 (OH) ]*3H O and [L1Cd2L2 (OH) ]*5H O with Cu(II), Ni(II), Co(II) and Cd(II) complexes of L2, respectively. The analytical data of these complexes indicate 1:2:2 ligand1:metal:ligand2 stoichiometry. Additional analyticcal data are given in Table-1, 2. Attempt to crystallize the ligand complexes from different solvents were failure. The structure of the L1 and L2 ligands were confirmed by a combination of elemental analyses, 1H-NMR, IR and UV-Vis spectral data.

All of the newly synthesized complexes are stable in air. The results of elemental analyses of the ligands and complexes are in agreement with the chemical formulas.

Conductance Measurements

These new complexes are non-electrolytes as shown by their molar conductivity (LM) measurements in DMSO, which are in the range for Cu(II), Ni(II), Co(II) and Cd(II) complexes at 7.78, 13.45, 15.57 and 11.13 -1cm2mol-1 [7,8], respectively (Table 1).

IR Spectra

The infrared spectra of the vic-dioxime ligand (L1), 1,3-dioxolane containing amine ligand (L2) and their metal complexes have been studied in order to characterize their structures. The relevant IR bands and their assignment are listed in Table 2. Generally, oximes are characterized by three IR absorption bands at 3423-3445 cm-1 (O-Hstr.), 1615-1574 cm-1 (C=Nstr) and 1064-1053 cm-1 (N-Ostr.) [9].

In order to study the bridging of the dioxime ligand to the metal in the complexes, the IR spectrum of the free oxime ligand was compared with the spectra of the metal complexes. In the IR spectrum of L2, the characteristic peaks are at 3361-3292 cm which are assigned to n(N-H) and n(-NH2) and 1111 cm that is assigned to the n(C-O-C) group [6,10]. These values are in harmony with previously reported diamino- glyoxime derivatives [15].

Table-1: Analytical and Physical Data of the Ligands and Their Complexes

###Formula###Elemental analyses

Compounds###Color###Yield(%) ueff/atom(B.M.) AM

###(F.W.) g/mole###Cale. (found), %

###C###H###N

###20.18

L1###C18H20N606###Dark###51.92###4.84

###(416.39)###yellow###82.77###-###-###(19.84)

###(51.81)###(5.18)

###C11H22N2O2###61.68###10.28###13.08

L2###Colorless###46.73###-###-

###(214.0)###(61.38)###(10.42)###(13.23)

###Cu2C40H74N10O17###43.91###6.82###12.80

[L1Cu2 L22 (OH)4]*3H2O###Brown###62.53###1.57###7.78

###(1094.16)###(43.96)###(6.72)###(13.11)

###Ni2C40H74N10O17###44.30###6.88###12.92

[L1Ni2L22(OH)4]*3H2O###Dark###78.42###2.90###13.45

###(1084.46)###brick red###(44.24)###(6.61)###(12.69)

###Co2C40H74N10O17###44.28###6.87###12.91

[L1Co2 L22(OH)4]*3H2O###bordeaux###74.57###4.25###15.57

###(1084.94)###(44.62)###(6.61)###(13.20)

###Co2C40H78N10O19###39.13###6.40###11.41

[L1Cd2L22(OH)4]*5H2O###Light yellow 56.95###Dia###11.13

###(1227.92)###(39.24)###(6.72)###(11.07)

LM =(-1 cm2 mol-1)

In the new complexes of amine and vic- dioxime, the oxime C=N stretching vibrations are shifted to 1598-1574 cm-1. These observations indicate the involvement of the nitrogen atom of the azomethine C=N group. In the IR spectra of the binuclear complexes weak O-H***O deformation vibrations are observed at ca. 1662-1681 cm-1 [4,11]. The disappearance of the OH stretching band and the shift of the C=N band to lower frequency in the IR spectra of binuclear complexes may be attributed to N,N-chelation. N-H stretching vibrations are positioned at near 3340 cm-1. Aromatic C-H stretching vibrations in the L1 are 3219-3060 cm-1, whereas, aliphatic C-H stretching vibrations in the L1 and L2 are 2923-2857 and 2934-2873 cm-1, respectively.

At the same time, the infrared bands observed near 3361 and 3247 cm-1, which are assigned to the -NH-and-NH2 frequency is shifted to lower frequency after complexation with respect to the free L2, whereas, the -NH- and -NH2 frequency is shifted to higher frequency after complexation with respect to the free L1H4. The strong absorption at 3356-3337 cm-1 in the complexes can be assigned to n(-NH2) of the intramolecular hydrogen bonded 1,3- diaminopropane moiety [12]. In the spectra of the Cu(II), Ni(II), Co(II) and Cd(II) complexes a few new bands occur at lower regions 455, 463, 459 and 458 cm-1, and 518, 516, 520 and 524 cm-1 which are attributed to the n(M-O) and n(M-N) vibrations, respectively [13,14].

1H-NMR Spectra

In order to identify structures of the amino and vic-dioxime ligands in solution, the 1H-NMR spectra was recorded in DMSO-d6 or CDCl3. The 1H-NMR assignments are also given in Experimental.

The 1H-NMR spectrum of vic-dioxime ligand (L1) in DMSO-d6 resulted in peak corresponding to the aromatic protons at 7.21-6.67 ppm as multiplet. In the spectrum of L1, the N-H protons in the neighbored of oxime groups as multiplet at 6.44-6.19 ppm were exhibited. The singlets at 12.08, 11.36, 10.82 and 10.14 ppm are assigned to the hydroxyl protons of vic-dioxime, which disappeared upon addition of D2O. The singlets for the oxime groups showed that the L1 was anti-configuration [15,16]. The spectrum also shows singlets at 4.72-1.12 ppm -CH2 protons. In the 1H- NMR spectrum of the ligand, the resonance observed at 8.54 and 8.13 ppm as two singlets were assigned to the azomethine protons of the oxime groups(HC=N-).

In the 1H-NMR spectrum of L2, there are two characteristic peaks, 1.75 and 2.40-3.20 ppm, which are attributable to the -NH- and -NH2 groups, which were also identified by D2O exchange [17] and -CH2 groups, respectively. There is another -O-CH2- peaks at 4.03 ppm as multiplet. These are in good agreement with literature.

1H-NMR spectra of the Cu(II), Ni(II) and Co(II) complexes could not be taken because of their paramagnetic character. At this time, since Cd(II) complex could not be soluble from DMSO and DMF, 1H-NMR spectra of the Cd(II) complex could not be taken clearly.

Magnetic Data and Electronic Spectra

Magnetic susceptibility measurements provided sufficient data to characterize the structures. The copper(II), nickel(II) and cobalt(II) complexes are paramagnetic. Their magnetic susceptibilities are 1.57 B.M. for [L1Cu2L2 (OH) ]*3H O, 2.90 B.M. for [L1Ni2L2 (OH) ]*3H O and 4.25 B.M. for [L1Ni2L2 (OH) ]*3H O and 4.25 B.M. for 2 2(OH)4]*3H2O. The alternative chemical environments will give four (O-H*O) bridge protons between hydroxyl ions with -OH groups in the anti- form of L1.The complex of Cd(II) ion, [L1Cd2L2 4 2 2(OH) ]*5H O is diamagnetic. All of the complexes are proposed to be octahedral.

Table-2: Characteristic IR Bands (cm-1) of the Ligands and Their Complexes in KBr Pellets.

Compounds###H2O/OH###N-H###C-Harom.###CHaliph.###C=N###N-O###O-H . . .O Caliph.-O-C###Carom.-O-C M-O###M-N

L1###3423###3247###3087###2923-2857###1615###1053###_###_###1248###_###_

L2###_###3361###_###2934-2873###_###_###_###1111###_###_###_

[L1 Cu2 L2 2(OH) 4]*3H2O###3456###3348###3060###2926-2873###1599###1062###1681###1116###1282###455###518

[L1Ni 2 L2 2(OH) 4]*3H2O###3445###3347###3065###2926-2873###1596###1062###1675###1100###1281###463###516

[L1Co2L2 2(OH) 4]*3H2O###3421###3342###3060###2936-2873###1574###1045###1668###1103###1260###459###520

[L1 Cd2L2 2(OH)4]*5H2O###3410###3365###3065###2934-2868###1598###1064###1662###1111###1256###458###524

The UV-Vis spectra of the ligands and their complexes were recorded in DMSO-DMF mixture solution in the wavelength range from 200 to 1100 nm. The spectra showed a sharp and intense two bands observed at 270-320 and 350-400 nm for free L1 [18] and 216-290 and 320-400 nm for free L2 ligand [19] are reasonably accounted for p-p and n-p transitions.

The electronic spectrum of the [L1Cu2L2 (OH) ]*3H O complex shows a shoulder at 650-725 nm, assignable to 2B1g-2Eg transition of the metal ion, suggesting a octahedral geometry [20].

The electronic spectrum of the [L1Ni2L2 (OH) ]*3H O complex has absorption bands at 425 and 730-765 nm assigned to the 3A2g-3T2g(P) and 3A2g-3T1g(F) transition, indicating a high-spin octahedral configuration [12,21].

The electronic spectrum of the [L1Co2L2 (OH) ]*3H O complex has absorption bands at 520 and 745-780 nm attributable to the 4T1g(F)-4A2g(F) and 4T1g(F)-4T2g(F) transitions, suggesting a high-spin octahedral geometry around the Co(II) ions [22].

A presumably octahedral structure is suggested for the diamagnetic [L1Cd2L2 (OH) ]*5H O complexes [18]. The electronic spectra of this complex shows absorption bands at 390 and 415 nm, which are attributed to the charge transfer transitions from the ligand to metal ions and from the metal ions to ligand [23]. The suggested general structure of all the complexes is shown in Fig. 3.

Thermal Studies

The decomposition temperature and the weight losses of the complexes and the ligands were taken from the TGA data. The TGA curves showed that the thermal decomposition of the complexes takes place in three steps. Thermogravimetric studies of all the complexes showed weight loss up to 32.56 oC, indicating existence of water molecules in the complexes. The inflation of the TGA curves of all the complexes at a temperature below 625 oC, indicates the decomposition of the fully organic part of the chelate, leaving metallic oxide at the final temperature [24].

Experimental

A new amino vic-dioxime ligand, (L1), derived from reaction of 1,2-bis(oamino- phenoxy)ethane [11,25] and anti-chloroglyoxime [11,25] were synthesized and characterized as described in the literature [26]. All the reagents used were purchased from Merck, Across or Labkim Company and chemically pure.

Elemental analyses (C, H, N) were performed on a LECO-932 CHNS-O elemental analyses apparatus. IR spectra were recorded on a Perkin Elmer Precisely Spectrum One Spectrometer as KBr pellets. 1H-NMR spectra were recorded on a Bruker GmbH DPX-300 MHz High Performance Digital FT-NMR spectrometers (in DMSO-d6). Electronic spectra were obtained on a Shimadzu UV- 1700 spectrometer. Magnetic susceptibilities were determined on a Sherwood Scientific Magnetic Susceptibility balance (Model MK1) at room temperature using Hg[Co(SCN)4] as a calibrate; diamagnetic corrections were calculated from Pascal's constants [7]. Molar conductances were measured on a CMD 750WPA conductometer [10]. Melting points were determined on a Gallenkamp melting points apparatus. TGA curve was recorded on a Shimadzu DTG-60AH thermobalance.

Synthesis of L1and L2

A solution 1,2-bis(o-aminophenoxy)ethane (2.44 g, 0.01 mol) was added to a solution of anti- chloroglyoxime (2.46 g, 0.02 mol) in ethanol (50 mL). Then a solution of Na2CO3 (2.65 g, 0.03 mol) in ethanol (50 mL) was added dropwise to this mixture at 60 oC over 12 h., the mixture filtred, and ethanol was removed by evaporation. The solid product was filtred off, washed with H2O several times, dried in vacuum, and crystallized from aqueous diethyl ether (1:3). Characteristic 1H-NMR peaks (DMSO-d6; d, ppm; 300 MHz): 4.72-4.24 (m, 4H, O-CH2), 8.54, 8.13 (s, 2H, H-C=N), 12.08, 11.36, 10.82, 10.14 (s, 4H, N-OH), 6.44, 6.19 (s, 2H, N-H), 7.21-6.67 (m, 8H, C-H(Ar.)) [4].

L2 was synthesized and characterized as described in the literature [6,27-31].

Cu(II), Ni(II), Co(II) and Cd(II) complexes of L2 was synthesized and characterized as described in the literature [6,27].

equation

The solution of [ML2(AcO)2]*nH2O where M is Cu(II) and Cd(II), n is 0 and 2, respectively, (0.40 g for Cu(II), 0.48 g for Cd(II), 1.0 mmol) and the solution of [M2L2(AcO)4*4H2O]*nH2O where M is Ni(II) and Co(II), n is 1 and 0, respectively, (0.66 g for Ni(II), 0.64 g Co(II), 1.0 mmol) in hot EtOH (15 cm3) were slowly added with stirring to a solution of L, (0.21 g, 0.5 mmol) in EtOH (50 cm ) at 60-65 degC temperature. The pH of the mixtures was ca. 4-5.

NaOH was added to the mixture to adjust the pH of the mixture and to complete the precipitation after the mixture had been heated on a water-bath 5 h. Finally, the mixtures were centrifuged several times with water and ethanol and the product dried in vacuum to yields a different color powder. These compounds are little soluble in DMF and DMSO, and insoluble water and ethanol.

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1Department of Chemistry, Faculty of Faculty of Arts and Sciences, Bingol University, Bingol, Turkey., 2Department of Chemistry, Faculty of Faculty of Arts and Sciences, Firat University, Elazig, Turkey., sibelduman23@hotmail.com
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Author:Duman, Sibel; Sekerci, Memet
Publication:Journal of the Chemical Society of Pakistan
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Date:Jun 30, 2012
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