- Email: [email protected]
Structural characterization and antioxidant properties of Cu(II) and Ni(II) complexes derived from dicyandiamide
Journal of Molecular Structure 1152 (2018) 29e36
Contents lists available at ScienceDirect
Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc
Structural characterization and antioxidant properties of Cu(II) and Ni(II) complexes derived from dicyandiamide Seda Nur Kertmen a, Ilyas Gonul b, Muhammet Kose a, * a b
Chemistry Department, Kahramanmaras Sutcu Imam University, Kahramanmaras, Turkey Chemistry Department, Cukurova University, Adana, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history: Received 3 August 2017 Received in revised form 19 September 2017 Accepted 19 September 2017 Available online 20 September 2017
New Cu(II) and Ni(II) complexes derived from dicyandiamide were synthesized and characterised by spectroscopic and analytical methods. Molecular structures of the complexes were determined by single crystal X-ray diffraction studies. In the complexes, the Cu(II) or Ni(II) ions are four-coordinate with a slight distorted square planar geometry. The ligands (L-nPen and L-iPen) derived from dicyandiamide formed via nucleophilic addition of alcohol solvent molecule in the presence Cu(II) or Ni(II) ions. Complexes were stabilised by intricate array of hydrogen bonding interactions. Antioxidant activity of the complexes was evaluated by DPPH radical scavenging and CUPRAC methods. The complexes exhibit antioxidant activity, however, their activities were much lower than standard antioxidants (Vitamin C and trolox). © 2017 Elsevier B.V. All rights reserved.
Keywords: Dicyandiamide Cu(II) Ni(II) X-ray diffraction studies Antioxidant activity
1. Introduction Dicyandiamide (DCDA) or cyanoguanidine is an interesting molecule and has found medicinal and industrial applications [1,2]. In industry, DCDA is used for melamine production and the basic ingredient of amino plastics and resins [3]. It is also widely used in the synthesis of several organic compounds such as fertilizers, fire retardant agents, epoxy laminates, powder coatings and adhesives, leather, rubber and explosive industries [3]. DCDA and its derivatives are also of biological interest [4e6]. DCDA and cyanamide, monomer of DCDA, have been reported that they interact with aldehyde dehydrogenases in the livers [7]. The DCDA derivatives have been show to exhibit a wide range of biological activities including antihypertensive, anticancer, antihistaminic and antimicrobial [3e5,8]. The DCDA is susceptible to the acid and base. In the presence of dilute acid, for example, it forms guanylurea while in the presence of a base (ammonia or amines) it forms biguanide [9]. The reaction of DCDA with alcohols in the presence of Cu(II), Ni(II) and Pd(II) ions results in the formation of 1-amidino-O-alkylureas [1,6,10e12]. The DCDA and its derivatives have also been used to prepare supramolecular structures via hydrogen bonding
* Corresponding author. E-mail addresses: [email protected], muhammetkose@ksu. edu (M. Kose). https://doi.org/10.1016/j.molstruc.2017.09.067 0022-2860/© 2017 Elsevier B.V. All rights reserved.
interactions [13e15]. In the biological systems, free radicals are formed due to the metabolic processes and the oxidative degradation of nutrients [16]. The most of the free radicals, which are generated from molecular oxygen (O2) during the energy production in mitochondria, are called reactive oxygen species (ROS) [17,18]. The ROS's are mainly superoxide (O 2 ), hydrogen peroxide (H2O2) and hydroxyl radicals. Normally, in a healthy organism, there is a balance between oxidants (free radicals) and antioxidant levels [19,20]. Free radicals or reactive oxygen species (ROS) start to give damage(oxidative stress) to the cell components if the balance between oxidants (free radicals) and antioxidants are broken [19e21]. The aging and diseases including diabetes, cancer, inflammation, neurological disorders and diuretic are usually associated with free radicals [21]. In our previous work, we have reported the synthesis and anticancer properties of the Cu(II) complexes derived from DCDA [3,8]. In this work, we prepared mononuclear Cu(II) and Ni(II) complexes derived from DCDA (Scheme 1). The synthesized complexes were characterised by spectroscopic and analytical methods. Solid state structures of the complexes were determined by single crystal X-ray diffraction studies. Finally, the antioxidant capacity of the complexes was investigated.
30
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
Scheme 1. Synthesis of the complexes.
2. Experimental 2.1. Materials Dicyandiamide (DCDA) and metal salts were purchased from Aldrich Chemical Company and used as received. All other reagents used in this study were purchased from commercial sources. Neocuproine, Trolox, DPPH (2,2-Diphenyl-1-picrylhydrazyl), Vitamin C, EtOH and MetOH (%99.9) were purchased from Sigma Aldrich and used without further purification. Perkin-Elmer Lamda 25 spectrometer was used for the UVevis absorption studies. Caution: Salts of perchlorate and their metal complexes are potentially explosive and should be handled with great care and in small quantities.
2.2. Physical measurements X-ray crystallographic data collection and cell refinement for the complexes were carried out using a Bruker D8 QUEST
diffractometer and data reduction was performed using Bruker SAINT. X-ray diffraction data were collected at 293(2) K using MoKa (l ¼ 0.71073 Å) radiation with a Bruker ApexII diffractometer [22]. SHELX-2014/6 was used to solve and refine the structures [23,24]. The structures were solved by direct methods and refined by full-matrix least squares against F2 using all data. All the nonhydrogen atoms were refined anisotropically. H atoms bonded to nitrogen atoms in complexes were located from difference fourier maps. Details of the crystal data and refinement are given in Table 1. The perchlorate disorder present in structure complexes [Cu(L-nPen)2](ClO4)2$2DMF (1), [Ni(L-nPen)2](ClO4)2$2DMF (3) and [Ni(L-iPen)2](ClO4)2$2(CH3)2CO (4). The perchlorate disorders were modelled over two orientations and refined with geometric and displacement parameter restraints (see supplementray and cif files). In the structure of complex [Cu(L-iPen)2](ClO4)2$2MeOH (2), [Ni(L-nPen)2] (5), [Ni(L-iPen)2] (6), the alkyl chains are disordered and were modelled over two orientations and refined with geometric and displacement parameter restraints (see supplementray and cif files).
Table 1 Crystallographic data for the complexes. Identification code
(1) 2DMF.
(2) 2MeOH
(3) 2DMF
(4) 2(CH3)2CO.
(5)
(6)
Empirical formula Formula weight (g/mol) Temperature (K) Wavelength (Å) Crystal system Space group Unit cell dimensions a (Å) b (Å) c (Å) a ( ) b ( ) g ( ) Volume (Å3) Z Crystal size (mm3) Ind.reflections [R(int)] Final R indices (R1, WR2) R indices (all data) (R1, WR2) CCDC
C20H46Cl2CuN10O12 753.11 293(2) 0.71073 Triclinic P-1 8.1859(15) 10.310(2) 12.150(3) 65.308(8) 72.683(7) 79.274(8) 887.2(3) 1 0.19 0.14 0.12 4393 [0.0340] 0.0548, 0.1320 0.0685, 0.1468 1544411
C16H40Cl2CuN8O12 671 293(2) 0.71073 Triclinic P-1 5.2081(13) 8.919(3) 17.146(5) 91.322(11) 96.112(10) 104.941(10) 764.1(4) 1 0.20 0.17 0.15 3791 [0.0380] 0.0451, 0.1122 0.0531, 0.1191 1544413
C20H46Cl2NiN10O12 748.24 293(2) 0.71073 Triclinic P-1 8.1014(12) 10.3820(16) 12.131(2) 65.324(6) 72.151(6) 78.971(6) 880.2(2) 1 0.17 0.12 0.11 4378 [0.0328] 0.070, 0.1195 0.0590, 0.1333 1544412
C20H44Cl2NiN8O12 718.24 293(2) 0.71073 Monoclinic P21/c 9.5117(12) 18.365(3) 10.0979(14) 90 104.236(4) 90 1709.7(4) 2 0.11 0.08 0.06 4271 [0.0536] 0.0475, 0.1142 0.0821, 0.1322 1544414
C14H30NiN8O2 401.17 293(2) 0.71073 Monoclinic P21/c 13.787(4) 8.015(2) 9.870(2) 90 109.527(9) 90 1027.9(5) 2 0.19 0.15 0.14 2465 [0.0498] 0.0454, 0.1085 0.0614, 0.1241 1544415
C14H30NiN8O2 401.17 293(2) 0.71073 Monoclinic P21/c 14.9243(16) Å 7.6071(8) Å 9.7301(9) Å 90 108.255(4) 90 1049.07(19) 2 0.15 0.11 0.10 2479 [0.0557] 0.0900, 0.1658 0.1147, 0.1761 1544416
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
2.3. Synthesis of Cu(II) complexes The complexes were prepared according to the reported method [8,11]. To a stirring solution of dicyandiamide (1 g, 12 mmol) in n pentanol or ipentanol (20 mL), Cu(ClO4)2$6H2O (2.2 g, 6 mmol) was added. The reaction mixture was refluxed for 8 h. The purple colour precipitation was filtered, washed with diethyl ether and dried in air. 2.3.1. [Cu(L-nPen)2](ClO4)2 (1) Yield: 3.39 g, 75%. Colour: Purple. M.p. ¼ 228e230 C (decomp.). Characterization: Anal. Calc. for C14H32Cl2N8CuO10 (606.90 g/mol): C, 27.71; H, 5.31; N, 18.46. Found: C, 27.12; H, 5.05; N, 17.98%. IR (cm1): 626, 736, 792, 1087, 1221, 1273, 1395, 1468, 1488, 1559, 1675, 2873, 1933, 1960, 3351, 3452. 2.3.2. [Cu(L-iPen)2](ClO4)2 (2) Yield: 3.01 g, 75%. Colour: Purple. M.p. ¼ 248e250 C (decomp.). Characterization: Anal. Calc. for C14H32Cl2N8CuO10 (606.90 g/mol): C, 27.71; H, 5.31; N, 18.46. Found: C, 26.98; H, 5.12; N, 18.12%. IR(cm1): 667, 734, 752, 778, 816, 853, 939, 961, 994, 1002, 1047, 1140, 1184, 1214, 1233, 1266, 1304, 1386, 1430, 1460, 1505, 1553, 1587, 1665, 2865, 2955, 3230, 3342, 3394, 3439, 3558. 2.4. Synthesis of [Ni(L-nPen)2](ClO4)2 and [Ni(L-iPen)2](ClO4)2 Ni(ClO4)2$6H2O (2.18 g, 5.95 mmol) and dicyandiamide were dissolved in npentanol or ipentanol (20 mL) followed by addition of NaOH (0.08 g, 2 mmol) [3]. The reaction mixture was refluxed for three days and then left to cool. The orange coloured precipitate was filtered, washed with diethyl ether (20 mL) and dried in air. 2.4.1. [Ni(L-nPen)2](ClO4)2 (3) Yield: 1.56 g, 39%. Colour: Orange. M.p. ¼ 248e250 C (decomp.). Characterization: Anal. Calc. for C14H32Cl2N8NiO10 (602.05 g/mol): C, 27.93; H, 5.36; N, 18.61. Found: C, 27.22; H, 5.05; N, 18.13%. IR(cm1): 626, 730, 779, 1088, 1249, 1300, 1401, 1468, 1512, 1563, 1674, 2874, 2937, 2959, 3229, 3346, 3430. 2.4.2. [Ni(L-iPen)2](ClO4)2 (4) Yield: 1.86 g, 47%. Colour: Orange. M.p. ¼ 258e260 C (decomp.). Characterization: Anal. Calc. for C14H32Cl2N8NiO10 (602.05 g/mol): C, 27.93; H, 5.36; N, 18.61. Found: C, 27.29; H, 4.96; N, 18.37%. IR(cm1): 678, 734, 745, 771, 853, 931, 961, 1050, 1188, 1244, 1259, 1296, 1319, 1397, 1412, 1460, 1475, 1505, 1520, 1553, 1576, 1661, 2869, 2955, 3223, 3342, 3387, 3450, 3584. 2.5. Synthesis of [Ni(L-nPen)2] and [Ni(L-iPen)2] NiCl2$6H2O (1.41 g, 5.95 mmol) was added to a refluxing solution of dicyandiamide in npentanol or ipentanol (20 mL). NaOH (0.08 g, 2 mmol) was added to the reaction mixture and refluxed for two days. The orange coloured precipitate was then filtered and washed with diethyl ether (20 mL) and dried in air. 2.5.1. [Ni(L-nPen)2] (5) Yield: 1.10 g, 28%. Colour: Orange. M.p. ¼ 258e260 C (decomp.). Characterization: Anal. Calc. for C14H30N8NiO2 (401.13 g/mol): C, 41.92; H, 7.54; N, 27.93. Found: C, 41.65; H, 7.41; N, 27.45%. IR(cm1): 648, 1084, 1229, 1285, 1457, 1542, 1617, 2854, 2932, 3186, 3443, 3577. 2.5.2. [Ni(L-iPen)2] (6) Yield: 1.10 g, 28%. Colour: Orange. M.p. ¼ 258e260 C (decomp.). Characterization: Anal. Calc. for C14H30N8NiO2 (401.13 g/mol): C,
31
41.92; H, 7.54; N, 27.93. Found: C, 41.38; H, 7.17; N, 27.09%. IR(cm1): 643, 1081, 1232, 1285, 1453, 1540, 1619, 2857, 2938, 3192, 3447, 3571. 2.6. Antioxidant activity of the complexes 2.6.1. DPPH radical scavenging activity Radical scavenging assay of the complexes were carried out using the slightly modified DPPH method reported by Miliauskas et al. [25]. According to this procedure, the complexes were prepared in MeOH at 0.06 mM DPPH concentration and vitamin C was used as standard. To a light-tight test tube, 100 mL from vitamin C or all the complexes solution at 0.02, 0.04, 0.06, 0.08, 0.10 mg/mL concentrations (in MeOH), and 3.9 mL of 0.06 mM DPPH solution were placed in each well. The solution was mixed vigorously and allowed to stand at room temperature for 20 min. Then, The sample absorbance (AS) was measured at 517 nm on a spectrophotometer. In addition, the control absorbance (AC) is measured at 517 nm by adding pure water (100 mL) instead of the compound solutions (100 mL). The percentage of radical scavenging activity (RSA%) was calculated according to the following equation [26]: %Inhibition ¼ {[(Control Absorbance (AC) - Sample Absorbance (AS)]/Control Absorbance} x 100.
2.6.2. The Cupric ion reducing antioxidant activity study CUPRAC antioxidant capacity experiment of synthesized transition metal complexes were determined according to the reported method [27]. To a test tube, 1 mL each of CuCl2$2H2O (102 M, in distilled water), neocuproine (7.5 103 M, in EtOH), and ammonium acetate (NH4CH3COO) buffer solution (1 M, pH: 7.0) and trolox (100 mL) as standard and all complexes at 20, 40, 60, 80, 100 mg/mL concentrations (in EtOH), and also 1 mL water were added to the initial mixture, so as to make the final volume 4.1 mL. The absorbance was recorded at 450 nm against the reagent blank after 1 h. Standard curve was prepared using different concentration of trolox. The results were expressed as mg TE (trolox equivalent) per g of sample [28]. 3. Results and discussion In this work, new Cu(II) and Ni(II) complexes derived from dicyandiamide were prepared and their molecular structures were determined by single crystal X-ray diffraction studies. The reaction of dicyandiamide with Cu(ClO4)2$6H2O salt in npentanol or ipentanol resulted in mononuclear complexes [Cu(L-nPen)2](ClO4)2 (1) and [Cu(L-iPen)2](ClO4)2 (2) with high yields and purity. In the complexes, the ligands L-nPen and L-iPen formed insitu in the presence of Cu(II) by the nucleophilic addition of npentanol or i pentanol resulting in bidentade chelating ligands [11,29]. The same reaction except using Ni(ClO4)2$6H2O in place of Cu(ClO4)2$6H2O required a base (NaOH excess amount) and longer reaction times [2] and gave complexes [Ni(L-nPen)2](ClO4)2 (3) and [Ni(L-iPen)2](ClO4)2 (4). In the complexes (1e4), two in situ formed ligands coordinates to the metal centers forming cationic complexes. The charge of the metal ions in each complex are balanced by two perchlorate ions and the presence of perchlorate anions were confirmed by FT-IR spectral measurements. On the other hand, the reaction of dicyandiamide with CuCl2$2H2O or NiCl2$6H2O in the presence of excess amount of NaOH gave neutral complexes [Ni(L-nPen)2] (5) and [Ni(L-iPen)2] (6). The neutral nature of the complexes were confirmed by conductivity measurements as well as elemental analysis and X-ray diffraction studies. The same
32
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
reactions except using Cu(ClO4)2$6H2O and Ni(ClO4)2$6H2O gave complexes (1e4). The reason why perchlorate ions lead to formation of cationic complexes may be due to stable supramolecular structure formation via hydrogen bonding interactions which does not allow the deprotonation of eNH groups in those complexes. The general preparation of the complexes are summarized in Scheme 1. The synthesized complexes are soluble in common organic solvents such as ethanol, methanol, acetone, DMF and DMSO and not soluble in diethyl ether and water. FT-IR spectra of the complexes were recorded in the range of 4000e450 cm1 and the data are given in experimental section. In the FT-IR spectra of the synthesized complexes, the stretching peaks observed at 3100-3400 cm1 are due to asymmetric and symmetric n(NeH) vibrations. The stretching vibrations of the nitrile group (C^N) observed in the FT-IR spectrum of the starting DCDA molecule completely disappeared in the spectra of the complexes [8]. The disappearance of the band due to nitrile group confirms the nucleophilic addition of an alcohol molecule to the nitrile group. In the spectra of the complexes, In the complexes, the characteristic ns(CeOeC) and na(CeOeC) vibrations were observed at 1121 and 955 cm1, respectively [3,8]. The CeH (aliphatic) stretching's were observed at 2800-2970 cm1. The characteristic n(C ¼ N) vibration bands were observed in the range of 1660e1675 cm1. In the spectra of the complexes 1e4, the two sharp bands at around 626 and 1088 cm1 are due to the perchlorate vibrations.
3.1. Crystal structures of [Cu(L-nPen)2](ClO4)2 and [Cu(L-iPen)2](ClO4)2 n
The single crystals of complexes [Cu(L- Pen)2](ClO4)2 and [Cu(L-iPen)2](ClO4)2 were grown DMF-ether and MeOH-ether diffusions, respectively. X-ray diffraction data revealed that the complexes crystallised as [Cu(L-nPen)2](ClO4)2$2DMF and i [Cu(L- Pen)2](ClO4)2$2MeOH. In the structure of the complexes, there are disorders in perchlorate ion and alky groups which were modelled and details are given in the supplementary file. The structures of the complexes are shown in Fig. 1. In both complexes, the Cu(II) ion sits on an inversion centre and the asymmetric unit, therefore, contains half of the complex cation, a perchlorate ion and a DMF/MeOH molecule. Bond lengths within the common [Cu(Ln Pen)2]2þ and [Cu(L-iPen)2]2þ cores are similar to each other (Table 2). The Cu(II) ion in each complex has slightly distorted
square planar geometry, coordinated to the imine nitrogen atoms of two ligands L-nPen or L-iPen. In both complexes, the C1eN2 and C2eN4 imine bond distances are within the range of typical C]N bond distances. In the structure complex [Cu(L-nPen)2](ClO4)2$2DMF, the DMF solvent molecules and perchlorate anions interact with the complex cations via hydrogen bonding (see supplementary file). DMF solvent molecules in the complexes involve in a bifurcated hydrogen bonding (as acceptor) with the terminal NH2 group and non-coordinated NH group. An oxygen atom of perchlorate oxygens makes a bifurcated hydrogen bonding with a pair of coordinated NH groups forming a pseudo-macrocycle. In the structure of the complex, the complex cations are linked by perchlorate ions via hydrogen bonds. One of the hydrogen atoms of the terminal nitrogen atom (N1eH1A) makes bifurcated hydrogen bonding with two perchlorate ions forming a 1D hydrogen bond chain (Fig. S1). In [Cu(L-iPen)2](ClO4)2$2MeOH, all NH groups involved in hydrogen bonding with either perchlorate ion and MeOH solvent molecules. The MeOH solvent molecules are linked to one complex cation [Cu(L-iPen)2]2þ via hydrogen bonding (as acceptor with the terminal NH2 group). The MeOH solvent molecules also makes a second hydrogen bond (as donor) with the one of the oxygen atom of a perchlorate anion contributing to overall stability of the structure. Coordinated NH groups (N2 and N4) make hydrogen bonds to an oxygen atom of perchlorate oxygens (bifurcated). The complex cations [Cu(L-iPen)2]2þ are linked by NH$$$$OClO3 hydrogen bonds forming a 1D hydrogen bond network. Hydrogen bonds within the crystal packing are shown in Fig. 2.
3.2. Crystal structures of [Ni(L-nPen)2](ClO4)2 and [Ni(L-iPen)2](ClO4)2 The X-ray quality crystals of [Ni(L-nPen)2](ClO4)2 were grown from slow diffusion of diethyl ether into a DMF solution of the complex. The complex was found to crystallise as [Ni(L-nPen)2](ClO4)2$2DMF. The crystals of [Ni(L-iPen)2](ClO4)2 were obtained from slow evaporation of [Ni(L-iPen)2](ClO4)2 in acetone and the complex cristallises as [Ni(L-iPen)2](ClO4)2$2(CH3)2CO. The structures of the complexes are shown in Fig. 3. The Ni(II) ion in both complex cations are located on an inversion centre, so asymmetric units consist of a half of the complex cation, a perchlorate ion and an DMF/acetone solvent molecule. In both complexes, perchlorate ions are highly disorder and the disorder was modelled over two
Fig. 1. Molecular structures of [Cu(L-nPen)2](ClO4)2$2DMF (left) and [Cu(L-iPen)2](ClO4)2$2MeOH (right). The isopentyl group disorder in [Cu(L-iPen)2](ClO4)2$2MeOH is shown. Hydrogen atoms are not shown for clarity, hydrogen bonds are shown as dashed lines.
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
33
Table 2 Selected bond lengths [Å] and angles [ ] for complexes.
M(1)-N(2) M(1)-N(4) N(2)eC(1) N(4)eC(2) N(3)eC(1) N(3)eC(2) N(2)-M(1)-N(4) N(2)i-M(1)-N(4) C(1)-N(3)-C(2)
(1) 2DMF
(2) 2MeOH
(3) 2DMF
(4) 2(CH3)2CO
(5)
(6)
1.930(2) 1.962(2) 1.298(3) 1.283(3) 1.360(3) 1.355(3) 88.96(9) 91.04(9) 127.3(2)
1.934 (2) 1.962(2) 1.291(3) 1.283(3) 1.370(3) 1.362(3) 88.89(8) 91.11(8) 126.74(18)
1.865(2) 1.876(2) 1.297(3) 1.285(3) 1.362(3) 1.352(3) 90.27(8) 89.73(8) 125.61(19)
1.866(2) 1.878(2) 1.295(3) 1.283(3) 1.359(3) 1.354(3) 90.13(9) 89.88(9) 125.8(2)
1.858(2) 1.859(2) 1.314(3) 1.309(3) 1.351(3) 1.325(3) 89.37(10) 90.63(10) 118.8(2)
1.863(4) 1.856(4) 1.314(6) 1.303(6) 1.342(6) 1.326(6) 89.35(18) 90.64(18) 118.2(4)
M: Cu for (1) and (2), M: Ni for (3e6).
Fig. 2. Packing diagram of [Cu(L-iPen)2](ClO4)2$2MeOH showing hydrogen bond interactions within the structure.
Fig. 3. Molecular structures of [Ni(L-nPen)2](ClO4)2$2DMF (left) and [Ni(L-iPen)2](ClO4)2$2(CH3)2CO (right), hydrogen bonds are shown as dashed lines.
positions. In the complex, each Ni(II) ion is four coordinated with approximate square planar geometry. The Ni(II) binds to the four imine nitrogen atoms of two ligands (L-nPen) with approximate square planar and there is no significant coordination interactions at the axial positions. The coordinated nitrogen donor atoms (N2 and N4) shows imine bond (C]N) character. Each L-nPen/L-iPen
ligand behaves as a bidentate chelating ligand binding to the Ni(II) through the imine nitrogen atoms (N2 and N4). In both structures, both the C1eN2 and C2eN4 distances show the characteristic C]N bond distances (Table 2). In the structure of [Ni(L-nPen)2](ClO4)2$2DMF, two DMF solvent molecules are linked to one complex cation [Ni(L-nPen)2]2þ via
34
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
Fig. 4. Molecular structures of [Ni(L-nPen)2] (left) and [Ni(L-iPen)2] (right). Hyrodgen atoms are not shown for clarity. The alkyl group disorders are shown in the structures.
hydrogen bonding (as acceptor with the terminal NH2 group and non-coordinated NH group). Coordinated NH groups (N2 and N4) makes hydrogen bond to an oxygen atom of perchlorate oxygens (bifurcated). In the structure of the complex, the complex cations [Ni(L-nPen)2]2þ are linked by perchlorate ions via hydrogen bonds producing a 1D hydrogen bond network (Fig. S2). In the structure of [Ni(L-iPen)2](ClO4)2$2(CH3)2CO, there are two acetone solvent molecules per complex cations and they make hydrogen bonds (as acceptor) with the terminal nitrogen (eNH2) and non-coordinated NH group of the ligand (eNH2$$$$OC(CH3)2 and eNH$$$$OC(CH3)2). The coordinated imine groups involved in hydrogen bonding with one of the perchlorate oxygen atom (¼NH$$$$OClO3) forming a pseudo-macrocycle. The structure of the complex was stabilised by strong eNH$$$$OClO3 hydrogen bond interactions. The complex cations are linked by eNH2$$$$OClO3 hydrogen bonds. These intermolecular hydrogen bond contacts are extended to their respective planes producing a 1D hydrogen bond chain with no hydrogen bonding interactions with above or below the planes. Packing diagram of the complex emphasizing the
hydrogen bond contacts is shown in Fig. S3. 3.3. Crystal structure of [Ni(L-nPen)2] and [Ni(L-iPen)2] Neutral analogues of the complexes [Ni(L-nPen)2](ClO4)2 and [Ni(L-iPen)2](ClO4)2 were obtained and their structures were confirmed by single crystal X-ray diffraction studies. The orange coloured crystals of the complexes [Ni(L-nPen)2] and [Ni(L-iPen)2] were obtained from slow evaporation of an acetone solution of the complexes. For both complexes, X-ray data revealed that the noncoordinated NH group of the each ligand is deprotonated forming a neutral complex molecules. In the structures, the Ni(II) ion sits on an inversion centre and asymmetric units contain one half of the complex molecule. In both complexes, the alky groups are disordered and this was modelled to obtained better refinement values (see supplementary file). Molecular structures of complexes are shown in Fig. 4. In both complexes, the longer C1¼N2 and C2¼N4 imine bond and the shorter C1eN3 and C2eN3 distances than the same bond distances in the perchlorate analogues of the complexes
Fig. 5. Packing diagram of [Ni(L-nPen)2] showing hydrogen bond interactions. Hydrogen bonds are shown as dashed lines.
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
Fig. 6. DPPH radical scavenging activity of the complexes.
suggest the p-electro delocalization in the chelate ring (N2eC1eN3eC2eN4eNi1) (Table 2). In the structure of both complexes [Ni(L-nPen)2] and [Ni(L-iPen)2], the deprotonated nitrogen atom (N3) links molecules via hydrogen bonding. The complexes show similar packing interactions. The N3 atom makes a bifurcated hydrogen bond (as acceptor) with coordinated imine groups (N3$$$$HN2 and N3$$$$HN4) and the hydrogen bond interactions form 2D hydrogen bond network. The terminal NH2 group also involves in intermolecular hydrogen bonding with etheric oxygen (O1) atom which further stabilise the crystal structure of the complexes. Packing diagram of complexes [Ni(L-nPen)2] and [Ni(L-iPen)2] are shown in Fig. S4 and Fig. 5, respectively. 3.4. Antioxidant activity of all compounds All antioxidant analysis methods are based on electron transfer (ET) of molecule [30]. The antioxidant properties of the metal complexes have been attracted a lot of attentions and examined mainly in the “in vitro” systems. The antioxidant activities of the Ni(II) and Cu(II) complexes were evaluated by DPPH and CUPRAC methods. 3.4.1. DPPH radical scavenging activity According to the DPPH method, percentage radical scavenging activity of the Ni(II) and Cu(II) complexes were studied at different concentrations. Antioxidant activity results of complexes [Cu(L-nPen)2](ClO4)2 and [Ni(L-nPen)2](ClO4)2 complexes are given in Fig. 6 and rest of the data are given in Fig. S5. The antioxidant activity results indicated that the synthesized complexes exhibited much lower activity than that of standard (Vitamin C). [Cu(L-nPen)2](ClO4)2 and [Ni(L-nPen)2](ClO4)2 complexes showed considerable DPPH activity compared to the standard antioxidant (Vitamin C). DPPH inhibition values of the compounds in different concentrations were compared to the vitamin C. The % inhibition values of
Table 3 IC50 (mg/mL) values with DPPH method of the complexes. Compounds
IC50 (mg/mL)±SD*
[Cu(L-nPen)2](ClO4)2 [Ni(L-nPen)2](ClO4)2 [Cu(L-iPen)2](ClO4)2 [Ni(L-iPen)2](ClO4)2 [Ni(L-nPen)2] Vitamin C
0.480 0.460 0.748 0.652 1.020 0.012
SD* of three experiments (n: 3).
± ± ± ± ± ±
0.01700 0.00410 0.03400 0.01250 0.00430 0.00014
35
Fig. 7. Cupric ion reducing activity of the complexes.
Table 4 TEACCUPRAC values of metal complexes. Compounds
TEACCUPRAC±SD
[Cu(L-nPen)2](ClO4)2 [Ni(L-nPen)2](ClO4)2 [Cu(L-iPen)2](ClO4)2 [Ni(L-iPen)2](ClO4)2 [Ni(L-nPen)2] Trolox (standard)
0.205 0.207 0.278 0.269 0.430 1.000
± ± ± ± ± ±
0.0021 0.0120 0.0141 0.0036 0.0031 0.0210
SD* of three experiments (n: 3).
metal complexes with standard [31] are in the following order; vitamin C > [Cu(L-nPen)2](ClO4)2 > [Ni(L-nPen)2](ClO4)2 > [Ni(L-iPen)](ClO4)2 > [Cu(L-iPen)](ClO4)2 > [Ni(L-nPen)2]. The structure of the complexes are similar differing principally in the alkoxy group. The complexes having perchlorate counter ions shows slightly better antioxidant activity than the neutral complex [Ni(L-nPen)2]. Increase in the concentration of the complexes resulted in slightly higher activities. Concentration corresponding to 50% radical scavenging activity (50% inhibition concentration) is expressed as IC50 and given in Table 3. The mechanism depends on the hydrogen atom in the molecular structure of the primary and secondary amines in the ligands, which is influenced by both the allylic double bond and inductive effects. This properties of ammines group in the ligands coordinated to metal was recorded in the theoretical and empirical literature to their impact on the proton transfer of the primary and secondary amines [32]. 3.4.2. Cupric ion reducing antioxidant activity study According to the CUPRAC method, working total antioxidant capacity (TAC) of synthesized metal complexes, was analyzed in 20, 40, 60, 80, 100 mg/mL concentrations of the compounds (included in trolox as the standard compound) and incubated for 1 h at room temperature [33,34]. The structurally characterised complexes show cupric ion reducing antioxidant activity, however, their antioxidant capacity much lower than trolox (as reference). Cupric Ion Reducing Antioxidant Capacity (CUPRAC) of [Cu(L-nPen)2](ClO4)2 and [Ni(L-nPen)2](ClO4)2 complexes are shown Fig. 7 and trolox equivalent antioxidant capacities are given Table 4. The neutral complex [Ni(L-nPen)2] showed considerably higher activity than the complexes with perchlorate counter ions. This is possibly due to the deprotonation of the non-coordinated eNHe group which allows the coordination and reduction of Cu(II) ion. 4. Conclusion In this work, new Cu(II) and Ni(II) complexes derived from
36
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
dicyandiamide were prepared and characterised. Solid state structures of the complexes were studied by single crystal X-ray diffraction method. The nucleophilic addition of npentanol and i pentanol lead to the formation of bidentate dimine ligands. Hydrogen bond interactions were observed in all complexes. Finally, antioxidant capacity of the complexes were studied by DPPH radical scavenging and CUPRAC methods. The antioxidant activity of the complexes were found be much lower than standard antioxidants. Acknowledgments The authors are grateful to the Kahramanmaras Sutcu Imam Unıversity for financial support (project number: 2016/6-16 YLS). The authors acknowledge Scientific and Technological Research Application and Research Centre, Sinop University, Turkey, for the use of the Bruker D8 QUEST diffractometer. Appendix A. Supplementary data Supplementary data related to this article can be found at https://doi.org/10.1016/j.molstruc.2017.09.067. References sko, R. Matya s, M. Holc, M. Novotna , L. Miskov [1] Z. Jalovy, Z. Padelkova, R. Jira a, Syntheses, crystal structures and properties of copper(II) complexes of 1amidinoisourea and biguanide nitrates, Polyhedron 44 (2012) 88e100. [2] P.A.M. Williams, E.G. Ferrer, N. Baeza, O.E. Piro, E.E. Castellano, E.J. Baran, Transition metal promoted addition of methanol to cyanoguanidine. Molecular structure and properties of the generated copper(ii) and nickel(ii) complexes, Z. Anorg. Allg. Chem. 631 (2005) 1502e1506. [3] M. Kose, S.E. Duman, V. Mckee, I. Akyol, M. Kurtoglu, $Hydrogen bond directed 1D to 3D structures of square-planar Ni(II) complexes and their antimicrobial studies, Inorg. Chim. Acta. 462 (2017) 281e288. [4] R. Olar, M. Badea, D. Marinescu, C. Chi, C. Bleotu, M. Nicoleta, E. Elena, M. Bucur, V. Lazar, A. Finaru, Prospects for new antimicrobials based on N,Ndimethylbiguanide complexes as effective agents on both planktonic and adhered microbial strains, Eur. J. Med. Chem. 45 (2010) 2868e2875. [5] F. Bentefrit, G. Morgant, B. Viossat, S. Leouce, N. Guilbaud, A. Pierre, G. Atassi, N.H. Dung, Synthesis and antitumor activity of the metformin platinum (IV) complex. Crystal structure of the tetrachloro(metformin)platinum (IV) dimethylsulfoxide solvate, J. Inorg. Biochem. 2 (1997) 53e59. [6] S.P. Devi, R.K.B. Devi, N.S. Devi, L.J. Singh, R.K.H. Singh, Structural and spectroscopic investigations on bis(1-amidino-O-2-alkoxyethylurea) copper(II) perchlorate complexes (alkoxy ¼ methoxy, ethoxy or butoxy), Polyhedron 47 (2012) 1e8. [7] E.G. Demaster, B. Redfern, H.T. Nagasawa, Mechanisms of inhibition of aldehyde dehydrogenase by nitroxyl, the active metabolite of the alcohol deterrent agent cyanamide, Biochem. Pharmacol. 55 (2015) 2007e2015. [8] M. Kose, C. Hepokur, D. Karakas, V. McKee, M. Kurtoglu, Structural, computational and cytotoxic studies of square planar copper(II) complexes derived from dicyandiamide, Polyhedron 117 (2016) 652e660. [9] C.H.M. Moore, Coordination Chemistry of Guanidine Derivatives, University of Nottingham, 1987. [10] S.P. Devi, R.K.H. Singh, R.M. Kadam, Synthesis and spectroscopic studies on copper(ii) binuclear complexes of 1-Phenylamidino-O-alkylurea (alkyl ¼ npropyl, n- and iso-butyl) with 1,3-diaminopropane or ethylenediamine, Inorg.
Chem. 45 (2006) 2193e2198. [11] R.K. Ray, M.K. Bandyopadhyay, George B. Kauffman, Metal-mediated addition of alcohols to dicyandiamide, Polyhedron 8 (1989) 757e762. [12] A. Meenongwa, U. Chaveerach, A.J. Blake, Bis(1-carbamimidoyl-2-ethyl-isourea)copper(II) bis-(perchlorate), Acta Crystallogr. Sect. E. 65 (2009) m1171. [13] P. Hubberstey, U. Suksangpanya, C.L. Wilson, Bis(N-methylamidino-O-methylurea)copper(II) cation: a planar building block for the construction of hydrogen-bonded rhombic (4, 4) grids, Cryst. Eng. Comm. 2 (2000) 141e144. [14] M.M. Bishop, L.F. Lindoy, P. Turner, Towards a system for the systematic structural study of intermolecular interactions in crystals of transition metal complexes, DaltonTrans. 39 (2010) 2563e2571, 10. [15] A. Moghimi, H.R. Khavassi, F. Dashtestani, D. Kordestani, A.E. Jafari, B. Maddah, S.M. Moosavi, A ternary tetracoordinated PdII complex with metformin and dipicolinate: synthesis, characterization and crystal structure, J. Mol. Struct. 996 (2011) 38e41. [16] M. Ikram, S. Rehman, A. Khan, R.J. Baker, T.S. Hofer, F. Subhan, M. Qayum, C. Schulzke, Synthesis, characterization, antioxidant and selective xanthine oxidase inhibitory studies of transition metal complexes of novel amino acid bearing Schiff base ligand, Inorg. Chim. Acta. 428 (2015) 117e126. [17] I. Gonul, M. Kose, G. Ceyhan, S. Serin, Methoxy group containing bidentate Schiff base ligands and their transition metal complexes: synthesis, structural characterisation, photoluminescence, antioxidant capacity and superoxide dismutase activity studies, Inorg. Chim. Acta. 453 (2016) 522e530. [18] A.A. Starkov, The role of mitochondria in reactive oxygen species metabolism and signaling, Ann. N. Y. Acad. Sci. 1147 (2008) 37e52. [19] I. Fridovich, Fundamental aspects of reactive oxygen species, or what's the matter with oxygen? Ann. N. Y. Acad. Sci. 893 (1999) 8e13. [20] I. Fridovich, Superoxide radical and superoxide dismutases, Ann. Rev. Biochem. 64 (1995) 97e112. [21] D.P. Riley, Functional mimics of superoxide dismutase enzymes as therapeutic agents, Chem. Rev. 99 (1999) 2573e2588. [22] Bruker, APEX2 and SAINT Bruker, AXS Inc, 1998. [23] G.M. Sheldrick, A short history of SHELX, Acta Crystallogr. Sect. A 64 (2008) 112e122. [24] G.M. Sheldrick, Crystal structure refinement with SHELXL, Acta Crystallogr. Sect. C Struct. Chem. 71 (2015) 3e8. [25] G. Miliauskas, P.R. Venskutonis, T.A. Van Beek, Screening of radical scavenging activity of some medicinal and aromatic plant extracts, Food Chem. 85 (2004) 231e237. [26] I.N. Booysen, A. Adebisi, M.P. Akerman, Formation, electrochemical and radical scavenging properties of novel ruthenium compounds with N, X-donor (X ¼ O, N) heterocyclic chelators, Inorg. Chim. Acta. 433 (2015) 13e20. [27] R. Apak, K. Guclu, M. Orek, S.E. Celik, Mechanism of antioxidant capacity assays and the CUPRAC (cupric ion reducing antioxidant capacity) assay, Microchim. Acta 160 (2008) 413e419. [28] Y. Kaya, A. Ercag, A. Koca, Synthesis, structures, electrochemical studies and antioxidant activities of cis-dioxomolybdenum(VI) complexes of the new bisthiocarbohydrazones, J. Mol. Struct. J. 1102 (2015) 117e126. [29] R. Virginia, W.A. Baker, Metal complexes of O-alkyl-1-amidinoureas. Part I. Nickel(II),, J. Chem. Soc.A (1967) 580e582. € I. _ DenIz, _ Antioksidan analiz yo €ntemleri ve DoGu [30] O.T. Okan, H. Varlibas¸, M. Oz, olarak kullanılabilecek odun € lgesinde antioksidan KaynaGı karadeniz bo dıs¸ı bazı bitkisel ürünler, J. For. Fac. 13 (2013) 48e64. [31] T.C. Shekhar, G. Anju, Antioxidant activity by DPPH radical scavenging method of Ageratum conyzoides Linn. leaves, Am. J. Ethnomed. 1 (4) (2014) 244e249. [32] A.A. Al-amiery, A.A.H. Kadhum, A.B. Mohamad, Antifungal and antioxidant activities of pyrrolidone thiosemicarbazone complexes, Hindawi Publ. Corp. Bioinorg. Chem. Appl. (2012) 1e6. [33] S.D. Çekiç, K.S. Bas, E. Tütem, Modified cupric reducing antioxidant capacity (CUPRAC) assay for measuring the antioxidant capacities of thiol-containing proteins in admixture with polyphenols, Talanta 79 (2009) 344e351. [34] M. Luis, B. Luisa, M.A. Maia, S. Reis, M.A. Segundo, Rapid assessment of endpoint antioxidant capacity of red wines through microchemical methods using a kinetic matching approach, Talanta 97 (2012) 473e483.
Contents lists available at ScienceDirect
Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc
Structural characterization and antioxidant properties of Cu(II) and Ni(II) complexes derived from dicyandiamide Seda Nur Kertmen a, Ilyas Gonul b, Muhammet Kose a, * a b
Chemistry Department, Kahramanmaras Sutcu Imam University, Kahramanmaras, Turkey Chemistry Department, Cukurova University, Adana, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history: Received 3 August 2017 Received in revised form 19 September 2017 Accepted 19 September 2017 Available online 20 September 2017
New Cu(II) and Ni(II) complexes derived from dicyandiamide were synthesized and characterised by spectroscopic and analytical methods. Molecular structures of the complexes were determined by single crystal X-ray diffraction studies. In the complexes, the Cu(II) or Ni(II) ions are four-coordinate with a slight distorted square planar geometry. The ligands (L-nPen and L-iPen) derived from dicyandiamide formed via nucleophilic addition of alcohol solvent molecule in the presence Cu(II) or Ni(II) ions. Complexes were stabilised by intricate array of hydrogen bonding interactions. Antioxidant activity of the complexes was evaluated by DPPH radical scavenging and CUPRAC methods. The complexes exhibit antioxidant activity, however, their activities were much lower than standard antioxidants (Vitamin C and trolox). © 2017 Elsevier B.V. All rights reserved.
Keywords: Dicyandiamide Cu(II) Ni(II) X-ray diffraction studies Antioxidant activity
1. Introduction Dicyandiamide (DCDA) or cyanoguanidine is an interesting molecule and has found medicinal and industrial applications [1,2]. In industry, DCDA is used for melamine production and the basic ingredient of amino plastics and resins [3]. It is also widely used in the synthesis of several organic compounds such as fertilizers, fire retardant agents, epoxy laminates, powder coatings and adhesives, leather, rubber and explosive industries [3]. DCDA and its derivatives are also of biological interest [4e6]. DCDA and cyanamide, monomer of DCDA, have been reported that they interact with aldehyde dehydrogenases in the livers [7]. The DCDA derivatives have been show to exhibit a wide range of biological activities including antihypertensive, anticancer, antihistaminic and antimicrobial [3e5,8]. The DCDA is susceptible to the acid and base. In the presence of dilute acid, for example, it forms guanylurea while in the presence of a base (ammonia or amines) it forms biguanide [9]. The reaction of DCDA with alcohols in the presence of Cu(II), Ni(II) and Pd(II) ions results in the formation of 1-amidino-O-alkylureas [1,6,10e12]. The DCDA and its derivatives have also been used to prepare supramolecular structures via hydrogen bonding
* Corresponding author. E-mail addresses: [email protected], muhammetkose@ksu. edu (M. Kose). https://doi.org/10.1016/j.molstruc.2017.09.067 0022-2860/© 2017 Elsevier B.V. All rights reserved.
interactions [13e15]. In the biological systems, free radicals are formed due to the metabolic processes and the oxidative degradation of nutrients [16]. The most of the free radicals, which are generated from molecular oxygen (O2) during the energy production in mitochondria, are called reactive oxygen species (ROS) [17,18]. The ROS's are mainly superoxide (O 2 ), hydrogen peroxide (H2O2) and hydroxyl radicals. Normally, in a healthy organism, there is a balance between oxidants (free radicals) and antioxidant levels [19,20]. Free radicals or reactive oxygen species (ROS) start to give damage(oxidative stress) to the cell components if the balance between oxidants (free radicals) and antioxidants are broken [19e21]. The aging and diseases including diabetes, cancer, inflammation, neurological disorders and diuretic are usually associated with free radicals [21]. In our previous work, we have reported the synthesis and anticancer properties of the Cu(II) complexes derived from DCDA [3,8]. In this work, we prepared mononuclear Cu(II) and Ni(II) complexes derived from DCDA (Scheme 1). The synthesized complexes were characterised by spectroscopic and analytical methods. Solid state structures of the complexes were determined by single crystal X-ray diffraction studies. Finally, the antioxidant capacity of the complexes was investigated.
30
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
Scheme 1. Synthesis of the complexes.
2. Experimental 2.1. Materials Dicyandiamide (DCDA) and metal salts were purchased from Aldrich Chemical Company and used as received. All other reagents used in this study were purchased from commercial sources. Neocuproine, Trolox, DPPH (2,2-Diphenyl-1-picrylhydrazyl), Vitamin C, EtOH and MetOH (%99.9) were purchased from Sigma Aldrich and used without further purification. Perkin-Elmer Lamda 25 spectrometer was used for the UVevis absorption studies. Caution: Salts of perchlorate and their metal complexes are potentially explosive and should be handled with great care and in small quantities.
2.2. Physical measurements X-ray crystallographic data collection and cell refinement for the complexes were carried out using a Bruker D8 QUEST
diffractometer and data reduction was performed using Bruker SAINT. X-ray diffraction data were collected at 293(2) K using MoKa (l ¼ 0.71073 Å) radiation with a Bruker ApexII diffractometer [22]. SHELX-2014/6 was used to solve and refine the structures [23,24]. The structures were solved by direct methods and refined by full-matrix least squares against F2 using all data. All the nonhydrogen atoms were refined anisotropically. H atoms bonded to nitrogen atoms in complexes were located from difference fourier maps. Details of the crystal data and refinement are given in Table 1. The perchlorate disorder present in structure complexes [Cu(L-nPen)2](ClO4)2$2DMF (1), [Ni(L-nPen)2](ClO4)2$2DMF (3) and [Ni(L-iPen)2](ClO4)2$2(CH3)2CO (4). The perchlorate disorders were modelled over two orientations and refined with geometric and displacement parameter restraints (see supplementray and cif files). In the structure of complex [Cu(L-iPen)2](ClO4)2$2MeOH (2), [Ni(L-nPen)2] (5), [Ni(L-iPen)2] (6), the alkyl chains are disordered and were modelled over two orientations and refined with geometric and displacement parameter restraints (see supplementray and cif files).
Table 1 Crystallographic data for the complexes. Identification code
(1) 2DMF.
(2) 2MeOH
(3) 2DMF
(4) 2(CH3)2CO.
(5)
(6)
Empirical formula Formula weight (g/mol) Temperature (K) Wavelength (Å) Crystal system Space group Unit cell dimensions a (Å) b (Å) c (Å) a ( ) b ( ) g ( ) Volume (Å3) Z Crystal size (mm3) Ind.reflections [R(int)] Final R indices (R1, WR2) R indices (all data) (R1, WR2) CCDC
C20H46Cl2CuN10O12 753.11 293(2) 0.71073 Triclinic P-1 8.1859(15) 10.310(2) 12.150(3) 65.308(8) 72.683(7) 79.274(8) 887.2(3) 1 0.19 0.14 0.12 4393 [0.0340] 0.0548, 0.1320 0.0685, 0.1468 1544411
C16H40Cl2CuN8O12 671 293(2) 0.71073 Triclinic P-1 5.2081(13) 8.919(3) 17.146(5) 91.322(11) 96.112(10) 104.941(10) 764.1(4) 1 0.20 0.17 0.15 3791 [0.0380] 0.0451, 0.1122 0.0531, 0.1191 1544413
C20H46Cl2NiN10O12 748.24 293(2) 0.71073 Triclinic P-1 8.1014(12) 10.3820(16) 12.131(2) 65.324(6) 72.151(6) 78.971(6) 880.2(2) 1 0.17 0.12 0.11 4378 [0.0328] 0.070, 0.1195 0.0590, 0.1333 1544412
C20H44Cl2NiN8O12 718.24 293(2) 0.71073 Monoclinic P21/c 9.5117(12) 18.365(3) 10.0979(14) 90 104.236(4) 90 1709.7(4) 2 0.11 0.08 0.06 4271 [0.0536] 0.0475, 0.1142 0.0821, 0.1322 1544414
C14H30NiN8O2 401.17 293(2) 0.71073 Monoclinic P21/c 13.787(4) 8.015(2) 9.870(2) 90 109.527(9) 90 1027.9(5) 2 0.19 0.15 0.14 2465 [0.0498] 0.0454, 0.1085 0.0614, 0.1241 1544415
C14H30NiN8O2 401.17 293(2) 0.71073 Monoclinic P21/c 14.9243(16) Å 7.6071(8) Å 9.7301(9) Å 90 108.255(4) 90 1049.07(19) 2 0.15 0.11 0.10 2479 [0.0557] 0.0900, 0.1658 0.1147, 0.1761 1544416
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
2.3. Synthesis of Cu(II) complexes The complexes were prepared according to the reported method [8,11]. To a stirring solution of dicyandiamide (1 g, 12 mmol) in n pentanol or ipentanol (20 mL), Cu(ClO4)2$6H2O (2.2 g, 6 mmol) was added. The reaction mixture was refluxed for 8 h. The purple colour precipitation was filtered, washed with diethyl ether and dried in air. 2.3.1. [Cu(L-nPen)2](ClO4)2 (1) Yield: 3.39 g, 75%. Colour: Purple. M.p. ¼ 228e230 C (decomp.). Characterization: Anal. Calc. for C14H32Cl2N8CuO10 (606.90 g/mol): C, 27.71; H, 5.31; N, 18.46. Found: C, 27.12; H, 5.05; N, 17.98%. IR (cm1): 626, 736, 792, 1087, 1221, 1273, 1395, 1468, 1488, 1559, 1675, 2873, 1933, 1960, 3351, 3452. 2.3.2. [Cu(L-iPen)2](ClO4)2 (2) Yield: 3.01 g, 75%. Colour: Purple. M.p. ¼ 248e250 C (decomp.). Characterization: Anal. Calc. for C14H32Cl2N8CuO10 (606.90 g/mol): C, 27.71; H, 5.31; N, 18.46. Found: C, 26.98; H, 5.12; N, 18.12%. IR(cm1): 667, 734, 752, 778, 816, 853, 939, 961, 994, 1002, 1047, 1140, 1184, 1214, 1233, 1266, 1304, 1386, 1430, 1460, 1505, 1553, 1587, 1665, 2865, 2955, 3230, 3342, 3394, 3439, 3558. 2.4. Synthesis of [Ni(L-nPen)2](ClO4)2 and [Ni(L-iPen)2](ClO4)2 Ni(ClO4)2$6H2O (2.18 g, 5.95 mmol) and dicyandiamide were dissolved in npentanol or ipentanol (20 mL) followed by addition of NaOH (0.08 g, 2 mmol) [3]. The reaction mixture was refluxed for three days and then left to cool. The orange coloured precipitate was filtered, washed with diethyl ether (20 mL) and dried in air. 2.4.1. [Ni(L-nPen)2](ClO4)2 (3) Yield: 1.56 g, 39%. Colour: Orange. M.p. ¼ 248e250 C (decomp.). Characterization: Anal. Calc. for C14H32Cl2N8NiO10 (602.05 g/mol): C, 27.93; H, 5.36; N, 18.61. Found: C, 27.22; H, 5.05; N, 18.13%. IR(cm1): 626, 730, 779, 1088, 1249, 1300, 1401, 1468, 1512, 1563, 1674, 2874, 2937, 2959, 3229, 3346, 3430. 2.4.2. [Ni(L-iPen)2](ClO4)2 (4) Yield: 1.86 g, 47%. Colour: Orange. M.p. ¼ 258e260 C (decomp.). Characterization: Anal. Calc. for C14H32Cl2N8NiO10 (602.05 g/mol): C, 27.93; H, 5.36; N, 18.61. Found: C, 27.29; H, 4.96; N, 18.37%. IR(cm1): 678, 734, 745, 771, 853, 931, 961, 1050, 1188, 1244, 1259, 1296, 1319, 1397, 1412, 1460, 1475, 1505, 1520, 1553, 1576, 1661, 2869, 2955, 3223, 3342, 3387, 3450, 3584. 2.5. Synthesis of [Ni(L-nPen)2] and [Ni(L-iPen)2] NiCl2$6H2O (1.41 g, 5.95 mmol) was added to a refluxing solution of dicyandiamide in npentanol or ipentanol (20 mL). NaOH (0.08 g, 2 mmol) was added to the reaction mixture and refluxed for two days. The orange coloured precipitate was then filtered and washed with diethyl ether (20 mL) and dried in air. 2.5.1. [Ni(L-nPen)2] (5) Yield: 1.10 g, 28%. Colour: Orange. M.p. ¼ 258e260 C (decomp.). Characterization: Anal. Calc. for C14H30N8NiO2 (401.13 g/mol): C, 41.92; H, 7.54; N, 27.93. Found: C, 41.65; H, 7.41; N, 27.45%. IR(cm1): 648, 1084, 1229, 1285, 1457, 1542, 1617, 2854, 2932, 3186, 3443, 3577. 2.5.2. [Ni(L-iPen)2] (6) Yield: 1.10 g, 28%. Colour: Orange. M.p. ¼ 258e260 C (decomp.). Characterization: Anal. Calc. for C14H30N8NiO2 (401.13 g/mol): C,
31
41.92; H, 7.54; N, 27.93. Found: C, 41.38; H, 7.17; N, 27.09%. IR(cm1): 643, 1081, 1232, 1285, 1453, 1540, 1619, 2857, 2938, 3192, 3447, 3571. 2.6. Antioxidant activity of the complexes 2.6.1. DPPH radical scavenging activity Radical scavenging assay of the complexes were carried out using the slightly modified DPPH method reported by Miliauskas et al. [25]. According to this procedure, the complexes were prepared in MeOH at 0.06 mM DPPH concentration and vitamin C was used as standard. To a light-tight test tube, 100 mL from vitamin C or all the complexes solution at 0.02, 0.04, 0.06, 0.08, 0.10 mg/mL concentrations (in MeOH), and 3.9 mL of 0.06 mM DPPH solution were placed in each well. The solution was mixed vigorously and allowed to stand at room temperature for 20 min. Then, The sample absorbance (AS) was measured at 517 nm on a spectrophotometer. In addition, the control absorbance (AC) is measured at 517 nm by adding pure water (100 mL) instead of the compound solutions (100 mL). The percentage of radical scavenging activity (RSA%) was calculated according to the following equation [26]: %Inhibition ¼ {[(Control Absorbance (AC) - Sample Absorbance (AS)]/Control Absorbance} x 100.
2.6.2. The Cupric ion reducing antioxidant activity study CUPRAC antioxidant capacity experiment of synthesized transition metal complexes were determined according to the reported method [27]. To a test tube, 1 mL each of CuCl2$2H2O (102 M, in distilled water), neocuproine (7.5 103 M, in EtOH), and ammonium acetate (NH4CH3COO) buffer solution (1 M, pH: 7.0) and trolox (100 mL) as standard and all complexes at 20, 40, 60, 80, 100 mg/mL concentrations (in EtOH), and also 1 mL water were added to the initial mixture, so as to make the final volume 4.1 mL. The absorbance was recorded at 450 nm against the reagent blank after 1 h. Standard curve was prepared using different concentration of trolox. The results were expressed as mg TE (trolox equivalent) per g of sample [28]. 3. Results and discussion In this work, new Cu(II) and Ni(II) complexes derived from dicyandiamide were prepared and their molecular structures were determined by single crystal X-ray diffraction studies. The reaction of dicyandiamide with Cu(ClO4)2$6H2O salt in npentanol or ipentanol resulted in mononuclear complexes [Cu(L-nPen)2](ClO4)2 (1) and [Cu(L-iPen)2](ClO4)2 (2) with high yields and purity. In the complexes, the ligands L-nPen and L-iPen formed insitu in the presence of Cu(II) by the nucleophilic addition of npentanol or i pentanol resulting in bidentade chelating ligands [11,29]. The same reaction except using Ni(ClO4)2$6H2O in place of Cu(ClO4)2$6H2O required a base (NaOH excess amount) and longer reaction times [2] and gave complexes [Ni(L-nPen)2](ClO4)2 (3) and [Ni(L-iPen)2](ClO4)2 (4). In the complexes (1e4), two in situ formed ligands coordinates to the metal centers forming cationic complexes. The charge of the metal ions in each complex are balanced by two perchlorate ions and the presence of perchlorate anions were confirmed by FT-IR spectral measurements. On the other hand, the reaction of dicyandiamide with CuCl2$2H2O or NiCl2$6H2O in the presence of excess amount of NaOH gave neutral complexes [Ni(L-nPen)2] (5) and [Ni(L-iPen)2] (6). The neutral nature of the complexes were confirmed by conductivity measurements as well as elemental analysis and X-ray diffraction studies. The same
32
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
reactions except using Cu(ClO4)2$6H2O and Ni(ClO4)2$6H2O gave complexes (1e4). The reason why perchlorate ions lead to formation of cationic complexes may be due to stable supramolecular structure formation via hydrogen bonding interactions which does not allow the deprotonation of eNH groups in those complexes. The general preparation of the complexes are summarized in Scheme 1. The synthesized complexes are soluble in common organic solvents such as ethanol, methanol, acetone, DMF and DMSO and not soluble in diethyl ether and water. FT-IR spectra of the complexes were recorded in the range of 4000e450 cm1 and the data are given in experimental section. In the FT-IR spectra of the synthesized complexes, the stretching peaks observed at 3100-3400 cm1 are due to asymmetric and symmetric n(NeH) vibrations. The stretching vibrations of the nitrile group (C^N) observed in the FT-IR spectrum of the starting DCDA molecule completely disappeared in the spectra of the complexes [8]. The disappearance of the band due to nitrile group confirms the nucleophilic addition of an alcohol molecule to the nitrile group. In the spectra of the complexes, In the complexes, the characteristic ns(CeOeC) and na(CeOeC) vibrations were observed at 1121 and 955 cm1, respectively [3,8]. The CeH (aliphatic) stretching's were observed at 2800-2970 cm1. The characteristic n(C ¼ N) vibration bands were observed in the range of 1660e1675 cm1. In the spectra of the complexes 1e4, the two sharp bands at around 626 and 1088 cm1 are due to the perchlorate vibrations.
3.1. Crystal structures of [Cu(L-nPen)2](ClO4)2 and [Cu(L-iPen)2](ClO4)2 n
The single crystals of complexes [Cu(L- Pen)2](ClO4)2 and [Cu(L-iPen)2](ClO4)2 were grown DMF-ether and MeOH-ether diffusions, respectively. X-ray diffraction data revealed that the complexes crystallised as [Cu(L-nPen)2](ClO4)2$2DMF and i [Cu(L- Pen)2](ClO4)2$2MeOH. In the structure of the complexes, there are disorders in perchlorate ion and alky groups which were modelled and details are given in the supplementary file. The structures of the complexes are shown in Fig. 1. In both complexes, the Cu(II) ion sits on an inversion centre and the asymmetric unit, therefore, contains half of the complex cation, a perchlorate ion and a DMF/MeOH molecule. Bond lengths within the common [Cu(Ln Pen)2]2þ and [Cu(L-iPen)2]2þ cores are similar to each other (Table 2). The Cu(II) ion in each complex has slightly distorted
square planar geometry, coordinated to the imine nitrogen atoms of two ligands L-nPen or L-iPen. In both complexes, the C1eN2 and C2eN4 imine bond distances are within the range of typical C]N bond distances. In the structure complex [Cu(L-nPen)2](ClO4)2$2DMF, the DMF solvent molecules and perchlorate anions interact with the complex cations via hydrogen bonding (see supplementary file). DMF solvent molecules in the complexes involve in a bifurcated hydrogen bonding (as acceptor) with the terminal NH2 group and non-coordinated NH group. An oxygen atom of perchlorate oxygens makes a bifurcated hydrogen bonding with a pair of coordinated NH groups forming a pseudo-macrocycle. In the structure of the complex, the complex cations are linked by perchlorate ions via hydrogen bonds. One of the hydrogen atoms of the terminal nitrogen atom (N1eH1A) makes bifurcated hydrogen bonding with two perchlorate ions forming a 1D hydrogen bond chain (Fig. S1). In [Cu(L-iPen)2](ClO4)2$2MeOH, all NH groups involved in hydrogen bonding with either perchlorate ion and MeOH solvent molecules. The MeOH solvent molecules are linked to one complex cation [Cu(L-iPen)2]2þ via hydrogen bonding (as acceptor with the terminal NH2 group). The MeOH solvent molecules also makes a second hydrogen bond (as donor) with the one of the oxygen atom of a perchlorate anion contributing to overall stability of the structure. Coordinated NH groups (N2 and N4) make hydrogen bonds to an oxygen atom of perchlorate oxygens (bifurcated). The complex cations [Cu(L-iPen)2]2þ are linked by NH$$$$OClO3 hydrogen bonds forming a 1D hydrogen bond network. Hydrogen bonds within the crystal packing are shown in Fig. 2.
3.2. Crystal structures of [Ni(L-nPen)2](ClO4)2 and [Ni(L-iPen)2](ClO4)2 The X-ray quality crystals of [Ni(L-nPen)2](ClO4)2 were grown from slow diffusion of diethyl ether into a DMF solution of the complex. The complex was found to crystallise as [Ni(L-nPen)2](ClO4)2$2DMF. The crystals of [Ni(L-iPen)2](ClO4)2 were obtained from slow evaporation of [Ni(L-iPen)2](ClO4)2 in acetone and the complex cristallises as [Ni(L-iPen)2](ClO4)2$2(CH3)2CO. The structures of the complexes are shown in Fig. 3. The Ni(II) ion in both complex cations are located on an inversion centre, so asymmetric units consist of a half of the complex cation, a perchlorate ion and an DMF/acetone solvent molecule. In both complexes, perchlorate ions are highly disorder and the disorder was modelled over two
Fig. 1. Molecular structures of [Cu(L-nPen)2](ClO4)2$2DMF (left) and [Cu(L-iPen)2](ClO4)2$2MeOH (right). The isopentyl group disorder in [Cu(L-iPen)2](ClO4)2$2MeOH is shown. Hydrogen atoms are not shown for clarity, hydrogen bonds are shown as dashed lines.
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
33
Table 2 Selected bond lengths [Å] and angles [ ] for complexes.
M(1)-N(2) M(1)-N(4) N(2)eC(1) N(4)eC(2) N(3)eC(1) N(3)eC(2) N(2)-M(1)-N(4) N(2)i-M(1)-N(4) C(1)-N(3)-C(2)
(1) 2DMF
(2) 2MeOH
(3) 2DMF
(4) 2(CH3)2CO
(5)
(6)
1.930(2) 1.962(2) 1.298(3) 1.283(3) 1.360(3) 1.355(3) 88.96(9) 91.04(9) 127.3(2)
1.934 (2) 1.962(2) 1.291(3) 1.283(3) 1.370(3) 1.362(3) 88.89(8) 91.11(8) 126.74(18)
1.865(2) 1.876(2) 1.297(3) 1.285(3) 1.362(3) 1.352(3) 90.27(8) 89.73(8) 125.61(19)
1.866(2) 1.878(2) 1.295(3) 1.283(3) 1.359(3) 1.354(3) 90.13(9) 89.88(9) 125.8(2)
1.858(2) 1.859(2) 1.314(3) 1.309(3) 1.351(3) 1.325(3) 89.37(10) 90.63(10) 118.8(2)
1.863(4) 1.856(4) 1.314(6) 1.303(6) 1.342(6) 1.326(6) 89.35(18) 90.64(18) 118.2(4)
M: Cu for (1) and (2), M: Ni for (3e6).
Fig. 2. Packing diagram of [Cu(L-iPen)2](ClO4)2$2MeOH showing hydrogen bond interactions within the structure.
Fig. 3. Molecular structures of [Ni(L-nPen)2](ClO4)2$2DMF (left) and [Ni(L-iPen)2](ClO4)2$2(CH3)2CO (right), hydrogen bonds are shown as dashed lines.
positions. In the complex, each Ni(II) ion is four coordinated with approximate square planar geometry. The Ni(II) binds to the four imine nitrogen atoms of two ligands (L-nPen) with approximate square planar and there is no significant coordination interactions at the axial positions. The coordinated nitrogen donor atoms (N2 and N4) shows imine bond (C]N) character. Each L-nPen/L-iPen
ligand behaves as a bidentate chelating ligand binding to the Ni(II) through the imine nitrogen atoms (N2 and N4). In both structures, both the C1eN2 and C2eN4 distances show the characteristic C]N bond distances (Table 2). In the structure of [Ni(L-nPen)2](ClO4)2$2DMF, two DMF solvent molecules are linked to one complex cation [Ni(L-nPen)2]2þ via
34
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
Fig. 4. Molecular structures of [Ni(L-nPen)2] (left) and [Ni(L-iPen)2] (right). Hyrodgen atoms are not shown for clarity. The alkyl group disorders are shown in the structures.
hydrogen bonding (as acceptor with the terminal NH2 group and non-coordinated NH group). Coordinated NH groups (N2 and N4) makes hydrogen bond to an oxygen atom of perchlorate oxygens (bifurcated). In the structure of the complex, the complex cations [Ni(L-nPen)2]2þ are linked by perchlorate ions via hydrogen bonds producing a 1D hydrogen bond network (Fig. S2). In the structure of [Ni(L-iPen)2](ClO4)2$2(CH3)2CO, there are two acetone solvent molecules per complex cations and they make hydrogen bonds (as acceptor) with the terminal nitrogen (eNH2) and non-coordinated NH group of the ligand (eNH2$$$$OC(CH3)2 and eNH$$$$OC(CH3)2). The coordinated imine groups involved in hydrogen bonding with one of the perchlorate oxygen atom (¼NH$$$$OClO3) forming a pseudo-macrocycle. The structure of the complex was stabilised by strong eNH$$$$OClO3 hydrogen bond interactions. The complex cations are linked by eNH2$$$$OClO3 hydrogen bonds. These intermolecular hydrogen bond contacts are extended to their respective planes producing a 1D hydrogen bond chain with no hydrogen bonding interactions with above or below the planes. Packing diagram of the complex emphasizing the
hydrogen bond contacts is shown in Fig. S3. 3.3. Crystal structure of [Ni(L-nPen)2] and [Ni(L-iPen)2] Neutral analogues of the complexes [Ni(L-nPen)2](ClO4)2 and [Ni(L-iPen)2](ClO4)2 were obtained and their structures were confirmed by single crystal X-ray diffraction studies. The orange coloured crystals of the complexes [Ni(L-nPen)2] and [Ni(L-iPen)2] were obtained from slow evaporation of an acetone solution of the complexes. For both complexes, X-ray data revealed that the noncoordinated NH group of the each ligand is deprotonated forming a neutral complex molecules. In the structures, the Ni(II) ion sits on an inversion centre and asymmetric units contain one half of the complex molecule. In both complexes, the alky groups are disordered and this was modelled to obtained better refinement values (see supplementary file). Molecular structures of complexes are shown in Fig. 4. In both complexes, the longer C1¼N2 and C2¼N4 imine bond and the shorter C1eN3 and C2eN3 distances than the same bond distances in the perchlorate analogues of the complexes
Fig. 5. Packing diagram of [Ni(L-nPen)2] showing hydrogen bond interactions. Hydrogen bonds are shown as dashed lines.
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
Fig. 6. DPPH radical scavenging activity of the complexes.
suggest the p-electro delocalization in the chelate ring (N2eC1eN3eC2eN4eNi1) (Table 2). In the structure of both complexes [Ni(L-nPen)2] and [Ni(L-iPen)2], the deprotonated nitrogen atom (N3) links molecules via hydrogen bonding. The complexes show similar packing interactions. The N3 atom makes a bifurcated hydrogen bond (as acceptor) with coordinated imine groups (N3$$$$HN2 and N3$$$$HN4) and the hydrogen bond interactions form 2D hydrogen bond network. The terminal NH2 group also involves in intermolecular hydrogen bonding with etheric oxygen (O1) atom which further stabilise the crystal structure of the complexes. Packing diagram of complexes [Ni(L-nPen)2] and [Ni(L-iPen)2] are shown in Fig. S4 and Fig. 5, respectively. 3.4. Antioxidant activity of all compounds All antioxidant analysis methods are based on electron transfer (ET) of molecule [30]. The antioxidant properties of the metal complexes have been attracted a lot of attentions and examined mainly in the “in vitro” systems. The antioxidant activities of the Ni(II) and Cu(II) complexes were evaluated by DPPH and CUPRAC methods. 3.4.1. DPPH radical scavenging activity According to the DPPH method, percentage radical scavenging activity of the Ni(II) and Cu(II) complexes were studied at different concentrations. Antioxidant activity results of complexes [Cu(L-nPen)2](ClO4)2 and [Ni(L-nPen)2](ClO4)2 complexes are given in Fig. 6 and rest of the data are given in Fig. S5. The antioxidant activity results indicated that the synthesized complexes exhibited much lower activity than that of standard (Vitamin C). [Cu(L-nPen)2](ClO4)2 and [Ni(L-nPen)2](ClO4)2 complexes showed considerable DPPH activity compared to the standard antioxidant (Vitamin C). DPPH inhibition values of the compounds in different concentrations were compared to the vitamin C. The % inhibition values of
Table 3 IC50 (mg/mL) values with DPPH method of the complexes. Compounds
IC50 (mg/mL)±SD*
[Cu(L-nPen)2](ClO4)2 [Ni(L-nPen)2](ClO4)2 [Cu(L-iPen)2](ClO4)2 [Ni(L-iPen)2](ClO4)2 [Ni(L-nPen)2] Vitamin C
0.480 0.460 0.748 0.652 1.020 0.012
SD* of three experiments (n: 3).
± ± ± ± ± ±
0.01700 0.00410 0.03400 0.01250 0.00430 0.00014
35
Fig. 7. Cupric ion reducing activity of the complexes.
Table 4 TEACCUPRAC values of metal complexes. Compounds
TEACCUPRAC±SD
[Cu(L-nPen)2](ClO4)2 [Ni(L-nPen)2](ClO4)2 [Cu(L-iPen)2](ClO4)2 [Ni(L-iPen)2](ClO4)2 [Ni(L-nPen)2] Trolox (standard)
0.205 0.207 0.278 0.269 0.430 1.000
± ± ± ± ± ±
0.0021 0.0120 0.0141 0.0036 0.0031 0.0210
SD* of three experiments (n: 3).
metal complexes with standard [31] are in the following order; vitamin C > [Cu(L-nPen)2](ClO4)2 > [Ni(L-nPen)2](ClO4)2 > [Ni(L-iPen)](ClO4)2 > [Cu(L-iPen)](ClO4)2 > [Ni(L-nPen)2]. The structure of the complexes are similar differing principally in the alkoxy group. The complexes having perchlorate counter ions shows slightly better antioxidant activity than the neutral complex [Ni(L-nPen)2]. Increase in the concentration of the complexes resulted in slightly higher activities. Concentration corresponding to 50% radical scavenging activity (50% inhibition concentration) is expressed as IC50 and given in Table 3. The mechanism depends on the hydrogen atom in the molecular structure of the primary and secondary amines in the ligands, which is influenced by both the allylic double bond and inductive effects. This properties of ammines group in the ligands coordinated to metal was recorded in the theoretical and empirical literature to their impact on the proton transfer of the primary and secondary amines [32]. 3.4.2. Cupric ion reducing antioxidant activity study According to the CUPRAC method, working total antioxidant capacity (TAC) of synthesized metal complexes, was analyzed in 20, 40, 60, 80, 100 mg/mL concentrations of the compounds (included in trolox as the standard compound) and incubated for 1 h at room temperature [33,34]. The structurally characterised complexes show cupric ion reducing antioxidant activity, however, their antioxidant capacity much lower than trolox (as reference). Cupric Ion Reducing Antioxidant Capacity (CUPRAC) of [Cu(L-nPen)2](ClO4)2 and [Ni(L-nPen)2](ClO4)2 complexes are shown Fig. 7 and trolox equivalent antioxidant capacities are given Table 4. The neutral complex [Ni(L-nPen)2] showed considerably higher activity than the complexes with perchlorate counter ions. This is possibly due to the deprotonation of the non-coordinated eNHe group which allows the coordination and reduction of Cu(II) ion. 4. Conclusion In this work, new Cu(II) and Ni(II) complexes derived from
36
S.N. Kertmen et al. / Journal of Molecular Structure 1152 (2018) 29e36
dicyandiamide were prepared and characterised. Solid state structures of the complexes were studied by single crystal X-ray diffraction method. The nucleophilic addition of npentanol and i pentanol lead to the formation of bidentate dimine ligands. Hydrogen bond interactions were observed in all complexes. Finally, antioxidant capacity of the complexes were studied by DPPH radical scavenging and CUPRAC methods. The antioxidant activity of the complexes were found be much lower than standard antioxidants. Acknowledgments The authors are grateful to the Kahramanmaras Sutcu Imam Unıversity for financial support (project number: 2016/6-16 YLS). The authors acknowledge Scientific and Technological Research Application and Research Centre, Sinop University, Turkey, for the use of the Bruker D8 QUEST diffractometer. Appendix A. Supplementary data Supplementary data related to this article can be found at https://doi.org/10.1016/j.molstruc.2017.09.067. References sko, R. Matya s, M. Holc, M. Novotna , L. Miskov [1] Z. Jalovy, Z. Padelkova, R. Jira a, Syntheses, crystal structures and properties of copper(II) complexes of 1amidinoisourea and biguanide nitrates, Polyhedron 44 (2012) 88e100. [2] P.A.M. Williams, E.G. Ferrer, N. Baeza, O.E. Piro, E.E. Castellano, E.J. Baran, Transition metal promoted addition of methanol to cyanoguanidine. Molecular structure and properties of the generated copper(ii) and nickel(ii) complexes, Z. Anorg. Allg. Chem. 631 (2005) 1502e1506. [3] M. Kose, S.E. Duman, V. Mckee, I. Akyol, M. Kurtoglu, $Hydrogen bond directed 1D to 3D structures of square-planar Ni(II) complexes and their antimicrobial studies, Inorg. Chim. Acta. 462 (2017) 281e288. [4] R. Olar, M. Badea, D. Marinescu, C. Chi, C. Bleotu, M. Nicoleta, E. Elena, M. Bucur, V. Lazar, A. Finaru, Prospects for new antimicrobials based on N,Ndimethylbiguanide complexes as effective agents on both planktonic and adhered microbial strains, Eur. J. Med. Chem. 45 (2010) 2868e2875. [5] F. Bentefrit, G. Morgant, B. Viossat, S. Leouce, N. Guilbaud, A. Pierre, G. Atassi, N.H. Dung, Synthesis and antitumor activity of the metformin platinum (IV) complex. Crystal structure of the tetrachloro(metformin)platinum (IV) dimethylsulfoxide solvate, J. Inorg. Biochem. 2 (1997) 53e59. [6] S.P. Devi, R.K.B. Devi, N.S. Devi, L.J. Singh, R.K.H. Singh, Structural and spectroscopic investigations on bis(1-amidino-O-2-alkoxyethylurea) copper(II) perchlorate complexes (alkoxy ¼ methoxy, ethoxy or butoxy), Polyhedron 47 (2012) 1e8. [7] E.G. Demaster, B. Redfern, H.T. Nagasawa, Mechanisms of inhibition of aldehyde dehydrogenase by nitroxyl, the active metabolite of the alcohol deterrent agent cyanamide, Biochem. Pharmacol. 55 (2015) 2007e2015. [8] M. Kose, C. Hepokur, D. Karakas, V. McKee, M. Kurtoglu, Structural, computational and cytotoxic studies of square planar copper(II) complexes derived from dicyandiamide, Polyhedron 117 (2016) 652e660. [9] C.H.M. Moore, Coordination Chemistry of Guanidine Derivatives, University of Nottingham, 1987. [10] S.P. Devi, R.K.H. Singh, R.M. Kadam, Synthesis and spectroscopic studies on copper(ii) binuclear complexes of 1-Phenylamidino-O-alkylurea (alkyl ¼ npropyl, n- and iso-butyl) with 1,3-diaminopropane or ethylenediamine, Inorg.
Chem. 45 (2006) 2193e2198. [11] R.K. Ray, M.K. Bandyopadhyay, George B. Kauffman, Metal-mediated addition of alcohols to dicyandiamide, Polyhedron 8 (1989) 757e762. [12] A. Meenongwa, U. Chaveerach, A.J. Blake, Bis(1-carbamimidoyl-2-ethyl-isourea)copper(II) bis-(perchlorate), Acta Crystallogr. Sect. E. 65 (2009) m1171. [13] P. Hubberstey, U. Suksangpanya, C.L. Wilson, Bis(N-methylamidino-O-methylurea)copper(II) cation: a planar building block for the construction of hydrogen-bonded rhombic (4, 4) grids, Cryst. Eng. Comm. 2 (2000) 141e144. [14] M.M. Bishop, L.F. Lindoy, P. Turner, Towards a system for the systematic structural study of intermolecular interactions in crystals of transition metal complexes, DaltonTrans. 39 (2010) 2563e2571, 10. [15] A. Moghimi, H.R. Khavassi, F. Dashtestani, D. Kordestani, A.E. Jafari, B. Maddah, S.M. Moosavi, A ternary tetracoordinated PdII complex with metformin and dipicolinate: synthesis, characterization and crystal structure, J. Mol. Struct. 996 (2011) 38e41. [16] M. Ikram, S. Rehman, A. Khan, R.J. Baker, T.S. Hofer, F. Subhan, M. Qayum, C. Schulzke, Synthesis, characterization, antioxidant and selective xanthine oxidase inhibitory studies of transition metal complexes of novel amino acid bearing Schiff base ligand, Inorg. Chim. Acta. 428 (2015) 117e126. [17] I. Gonul, M. Kose, G. Ceyhan, S. Serin, Methoxy group containing bidentate Schiff base ligands and their transition metal complexes: synthesis, structural characterisation, photoluminescence, antioxidant capacity and superoxide dismutase activity studies, Inorg. Chim. Acta. 453 (2016) 522e530. [18] A.A. Starkov, The role of mitochondria in reactive oxygen species metabolism and signaling, Ann. N. Y. Acad. Sci. 1147 (2008) 37e52. [19] I. Fridovich, Fundamental aspects of reactive oxygen species, or what's the matter with oxygen? Ann. N. Y. Acad. Sci. 893 (1999) 8e13. [20] I. Fridovich, Superoxide radical and superoxide dismutases, Ann. Rev. Biochem. 64 (1995) 97e112. [21] D.P. Riley, Functional mimics of superoxide dismutase enzymes as therapeutic agents, Chem. Rev. 99 (1999) 2573e2588. [22] Bruker, APEX2 and SAINT Bruker, AXS Inc, 1998. [23] G.M. Sheldrick, A short history of SHELX, Acta Crystallogr. Sect. A 64 (2008) 112e122. [24] G.M. Sheldrick, Crystal structure refinement with SHELXL, Acta Crystallogr. Sect. C Struct. Chem. 71 (2015) 3e8. [25] G. Miliauskas, P.R. Venskutonis, T.A. Van Beek, Screening of radical scavenging activity of some medicinal and aromatic plant extracts, Food Chem. 85 (2004) 231e237. [26] I.N. Booysen, A. Adebisi, M.P. Akerman, Formation, electrochemical and radical scavenging properties of novel ruthenium compounds with N, X-donor (X ¼ O, N) heterocyclic chelators, Inorg. Chim. Acta. 433 (2015) 13e20. [27] R. Apak, K. Guclu, M. Orek, S.E. Celik, Mechanism of antioxidant capacity assays and the CUPRAC (cupric ion reducing antioxidant capacity) assay, Microchim. Acta 160 (2008) 413e419. [28] Y. Kaya, A. Ercag, A. Koca, Synthesis, structures, electrochemical studies and antioxidant activities of cis-dioxomolybdenum(VI) complexes of the new bisthiocarbohydrazones, J. Mol. Struct. J. 1102 (2015) 117e126. [29] R. Virginia, W.A. Baker, Metal complexes of O-alkyl-1-amidinoureas. Part I. Nickel(II),, J. Chem. Soc.A (1967) 580e582. € I. _ DenIz, _ Antioksidan analiz yo €ntemleri ve DoGu [30] O.T. Okan, H. Varlibas¸, M. Oz, olarak kullanılabilecek odun € lgesinde antioksidan KaynaGı karadeniz bo dıs¸ı bazı bitkisel ürünler, J. For. Fac. 13 (2013) 48e64. [31] T.C. Shekhar, G. Anju, Antioxidant activity by DPPH radical scavenging method of Ageratum conyzoides Linn. leaves, Am. J. Ethnomed. 1 (4) (2014) 244e249. [32] A.A. Al-amiery, A.A.H. Kadhum, A.B. Mohamad, Antifungal and antioxidant activities of pyrrolidone thiosemicarbazone complexes, Hindawi Publ. Corp. Bioinorg. Chem. Appl. (2012) 1e6. [33] S.D. Çekiç, K.S. Bas, E. Tütem, Modified cupric reducing antioxidant capacity (CUPRAC) assay for measuring the antioxidant capacities of thiol-containing proteins in admixture with polyphenols, Talanta 79 (2009) 344e351. [34] M. Luis, B. Luisa, M.A. Maia, S. Reis, M.A. Segundo, Rapid assessment of endpoint antioxidant capacity of red wines through microchemical methods using a kinetic matching approach, Talanta 97 (2012) 473e483.