Hydrothermal synthesis of copper (II) and Nickel (II) nano complexes with unsymmetric tetradentate Schiff base ligand. New precursors for preparation of copper (II) and nickel (II) oxides nano-particles

Document Type: Research Paper


1 Department of Chemistry, Firoozabad Branch, Islamic Azad University, Fars, Iran

2 Department of Chemistry, Darab Branch, Islamic Azad University, Fars, Iran


Two new nano particles of copper (II) and nickel (II) complexes, [Cu(cd5Clsalen)] (1) and [Ni(cd5Clsalen)] (2) with unsymmetrical tetradentate Schiff base ligand cd5Clsalen={methyl-2-[N-[2-(2-hydroxy-5-choloro-2phenyl) methylidynetrilo]ethyl}amino-1-cyclopentenedithiocarboxylate, were synthesized by hydrothermal method. These compounds were characterized by a variety of physic-chemical techniques via. scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (IR) and elemental analysis. The complexes (in bulk) have a NNOS coordination sphere, with the two nitrogens coordinated in a cis configuration. The coordination around nickel center is essentially square-planar with a small tetrahedral distortion and the geometry around the copper center is square planar. Nano-particles of Copper (II) and Nickel (II) oxides have been prepared by calcination of two different Copper (II) and Nickel (II) complexes at 450 ºC that were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and IR spectroscopy. The average size of the particles was estimated from the Sherrer formula. This study demonstrates the Schiff base complexes may be suitable precursors for the preparation of nanoscale materials with different and interesting morphologies.



Schiff bases are important ligands in coordination chemistry with extensive applications in different fields. Schiff bases are derived from aromatic carbonyl compounds and have been widely studied in connection with metalloprotien models and asymmetric catalysis, due to versatility of their steric and electronic properties [1]. Nanometer-sized particles of metal coordination supramolecules are fascinating to explore, since their unique properties are controlled by the large number of surface molecules, which experience an entirely different environment than those in a bulk crystal. Controlling the growth of materials at the submicrometer scale is of centeral importance in the emerging field of nanotechnology [2-10]. Although considerable effort has been dedicated to the controlled synthesis of nanoscale particles of metals, oxides, sulfides, and ceramic materials, little attention has been focused to date on nanoparticles of supramolecular compounds such as Schiff base complexes. Hydrothermal method is a promising synthetic method because of the low process temperature and very easy control of the particle size. The hydrothermal process has several advantages over other growth processes such as use of simple equipment, catalyst-free growth, low cost, large areauniform production, environmental friendliness and less hazard [11]. In the present work, two copper (II) and nickel (II) supramolecules with ligand {methyl-2-[N-[2-(5-choloro-2phenolate) methylidynetrilo] ethyl} aminato (-1)-1-cyclo pentenedithiocarboxylate, were synthesized by hydrothermal method. Copper (II) oxide nanoparticles has wide different applications according to the physical and chemical properties, such as superconductivity, photovoltaic properties, relative stability, and the antimicrobial activity [12]. Nowadays, application of CuO nanoparticles is of particular importance for antioxidant [13], antibacterial [14], thermal conductivity [15], battery [16], and solar cell applications [17]. CuO-NPs has been prepared via several methods such as sonochemical [18], alcohothermal and colloid-thermal synthesis [19-21], electrochemical method [22-24], and microwave radiation method [2]. Nickel oxide has a wide range of application in the manufacture of ceramic composite parts, magnetic materials, alkaline battery cathods, anti-feromagnetic layers and p-type transparent conducting films, electrochromic films, hetrogenous catalytic materials and gas sensors [26-32]. NiO nano-powder has been prepared using several methods such as ultrasonic radiation, carbonyl method, laser chemical processing, microwave pyrolysis, sol-gel technique and mechanochemical processing [33-41]. The use of coordination complexes as precursors for the preparation of inorganic nanomaterials such as copper (II) and nickel (II) oxide has not yet been investigated thoroughly. In this paper, copper (II) and nickel (II) oxide nanoparticles were obtained by direct thermal decomposition of compounds 1 and 2 at 450 ºC. The preparation of metal oxide nanostructures through thermal decomposition of complexes opens a new window for chemists to overcome challenges such as control of process condition, particle size, particle crystal structure and purity.


Materials and Physical Techniques

All reagents and solvents for the synthesis and analysis were commercially available from Merck Company and used as received. Doubly distilled water was used to prepare aqueous solutions. A 30 ml Teflon-lined stainless-steel autoclave was used to do the reactions. The vessels were filled approximately to 40% capacity and heated for 4 h at 180 °C. IR spectra were recorded using Perkin-Elmer 597 and Nicolet 510P spectrophotometers. Micro analyses were carried out using a Heraeus CHN-O- Rapid analyzer. Melting points were measured on an Electrothermal 9100 apparatus. X-ray powder diffraction (XRD) measurements were performed using an X’pert diffractometer of Philips company with monochromated Cukα radiation (λ = 1.54056 Å). Simulated XRD powder pattern based on single crystal data were prepared using Mercury software [42]. The crystallite sizes of the selected samples were estimated using the Sherrer method. The samples were characterized with a scanning electron microscope (SEM) (Philips XL 30) with gold coating.

Synthesis of ligand cd5Clsalen, [Cu(cd5Clsalen)] (1) and [Ni(cd5Clsalen)] (2)

Methyl-2-{N-(2׳-aminoethane)}-amino-1-cyclopentenedithiocarboxylate (Hcden) was prepared by published methods [43-46]. The ligand was prepared by addition of the equimolar amount of the 5-chlorosalicylaldehyde, to a methanolic solution of Hcden. The yellow product was recrystallized from methanol/chloroform 1:1 (V:V). To a solution of an appropriate amount of ligand (0.1 mmol) in 10 mL of chloroform/methanol 2:1 (V:V), a solution of metal (II) acetate (0.1 mmol) in 10 mL of methanol was added. The solution was stirred for 15 min and then allowed to stand at room temperature for 24 h. After filtering, the crude product was recrystallized from acetonitrile/methanol 1:1 (V:V).

Compound 1: White crystals, d.p. 260 °C. Found C: 45.98, H: 4.39, N: 6.68, S: 15.12 %; calculated for C16H17 N2ClOS2Cu; C: 46.15, H: 4.11, N: 6.73, S: 15.40 %. IR (cm-1) selected bands: ν = 710(vs), 1166(s), 1260(vs), 1455(vs), 1629(s).

Compound 2: White crystals, m.p. 250 °C. (Found C: 46.42, H: 4.21, N: 6.83, S: 15.43 %; calculated for C16H17 N2ClOS2Ni; C: 46.69, H: 4.31, N: 6.66, S: 15.24 %). IR (cm-1) selected bands: ν = 712(vs), 1150(s), 1260(vs), 1460(vs), 1629(s).

Synthesis of [Cu(cd5Clsalen)] (1) and [Ni(cd5Clsalen)] (2) nano-particles using hydrothermal method

To prepare nano-scale compounds 1 and 2, to a solution of an appropriate amount of ligand (0.1 mmol) in 10 mL of chloroform/methanol 2:1 (V:V), a solution of metal (II) acetate (0.1 mmol) in 10 mL of methanol was added. The solution was charged into a Teflon-lined stainless steel autoclave and heated at 450 °C for 24 h, then the autoclave was cooled to room temperature. The product was filtered, dried and characterized.

Compound 1: d.p. 253 °C. Found C: 45.49, H: 4.14, N: 7.04, S: 15.93 %; IR (cm-1) selected bands: ν =710(vs), 1164(s), 1260(s), 1455(vs), 1629(s).

Compound 2: m.p. 244 °C. (Found C: 46.27, H: 4.13, N: 6.35, S: 15.19 %; IR (cm-1) selected bands: ν = 715(vs), 1150(s), 1260(s), 1460(vs), 1629(s).

Synthesis of CuO and NiO nanoparticles

For preparation of CuO and NiO nano-particles calcinations of bulk powder compounds 1 and 2 were done at 450 ºC in static atmosphere of air for 4 h. IR spectrum and powder XRD diffraction shows that calcination was completed and the entire compounds decomposed.


Reaction between tetradentate Schiff base ligand cd5Clsalen and copper (II) or nickel (II) acetate yielded crystalline materials formulated as [Cu(cd5Clsalen)] (1) and [Ni(cd5Clsalen)] (2), respectively. Nano-particles of compounds 1-2 were obtained by hydrothermal method while the bulk powder of compounds 1-2 were obtained using reflux method. Scheme 1 gives an overview of the methods used for the synthesis of compounds 1-2 using the two different routes. The elemental analysis of the nanoparticles and single crystalline materials of compounds 1 and 2 are indistinguishable. The FT-IR spectra of two complexes 1-2 compared with those of the corresponding ligand indicates that the ν (C=N) band around 1600 cm–1ν (C-O) bands at 1220-1286 cm–1ν (C=C) band in the region of 1456-1496 cm–1 , ν (C-S) band at 700-790 cm–1 and ν (C-S) + ν (C-N) cm–1 bands between 1099 and 1180 cm–1 are shifted to lower energies. These results showed that the Cu (II) and Ni (II) ions are coordinated through the nitrogen atoms of the amine group, oxygen atom of the phenolic group and sulfur of the C=S group for two complexes. Figs. 1 and 2 show the comparison of XRD patterns, simulated from single crystal X-ray data against the nano powder of compounds 1-2 prepared by the hydrothermal method, respectively. The comparison between these XRD patterns indicates acceptable matches with slight differences in 2θ. Estimated from the Sherrer formula for the calculation of particle sizes from the broadening of the XRD peaks (D = 0.891λ/βcosθ, where D is the average grain size, λ is the X-ray wavelength (0.15405 nm), and θ and β are the diffraction angle and full-width at half maximum of an observed peak, respectively), the average size of the particles was found to be around 92.4 for compound 1 and 76.3 for compound 2. Figs. 3 and 4 show the SEM images of the compounds 1 and 2. The structures of compounds [Cu(cd5Clsalen)] (1) and [Ni(cd5Clsalen)] (2) were previously analyzed and reported [47-48]. In compound 1, the Cu (II) atom is coordinated by S, O and two N atoms in a nearly planar environment. The coordination geometry around Cu center is nearly planar with the dihedral angle of 7.65(3)° between planes of NCuO and NCuS (. The x-ray structure of compound 2 revealed that the complex has a N2OS coordination sphere, with the two nitrogen atoms coordinated in a cis configuration (Figs. 5 and 6). The coordination around nickel is essentially square-planar with a small tetrahedral distortion. (Dihedral angle of 5.43(3)° between coordination planes NNiO and SNiN (Figs. 7 and 8).

Nano-particles of CuO and NiO have been generated by calcination of compounds 1 and 2. The final product upon calcination of compounds 1-2 at 400°C, based on their IR and XRD patterns are CuO and NiO. The IR spectrum of CuO and NiO nanoparticles after calcinations of compounds 1-2 shows absorption bands at about 500 cm-1 that can be attributed to the stretching modes of M-O (M=Cu and Ni) and the weak bands in the range of 1380-3425 cm-1 are probably attributed to the presence of water in the KBr matrix. Figs. 9 and 10 show X-ray powder diffraction pattern of CuO and NiO nanoparticles after calcination of compounds 1 and 2. The XRD patterns of CuO and NiO nanoparticles after calcinations of compounds 1 and 2 are in agreement with the typical CuO diffraction (monoclinic phase, space group C2/c, with lattice constants a = 4.5850 Å, b=.4230 Å and c = 5.2000 Å, Z = 4, ICSD No. 00-041-0254) and NiO diffraction (cubic phase, space group Fm3m, with lattice constant a,b,c=4.1771 and z=4, ICSD No. 00-047-1049). No characteristic peaks of impurities are detected in XRD patterns. Figs. 11 and 12 show the SEM images and the corresponding particle size distribution histogram of CuO and NiO nanoparticles obtained from calcinations of nano compounds 1-2 at 450 ºC.


Nano particles of copper (II) and nockel (II) complexes with a tetredentate sciff base ligand, [[Cu(cd5Clsalen)] (1) and [Ni(cd5Clsalen)] (2), have been synthesized by hydrothermal method. Compounds 1-2 were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), elemental analyses and IR spectroscopy. Nano-particles of copper (II) and nickel (II) oxide have been prepared by calcinations of two different Schiff base complexes, compounds 1-2. The nano oxides were characterized by scanning electron microscopy (SEM) images, X-ray powder diffraction (XRD) and IR spectroscopy. This study demonstrates that the Schiff base complexes may be suitable precursors for the preparation of nanoscale materials with interesting morphologies.


This work was supported by the Islamic Azad University of Firoozabad.


The author declare that there is no conflict of interests regarding the publication of this manuscript.

1. Habibi MH, Montazerozohori M, Lalegani A, Harrington RW, Clegg W. Synthesis, structural and spectroscopic properties of a new Schiff base ligand N,N′-bis(trifluoromethylbenzylidene)ethylenediamine. Journal of Fluorine Chemistry. 2006;127(6):769-73.

2. Shi H, Qi L, Ma J, Cheng H. Polymer-Directed Synthesis of Penniform BaWO4Nanostructures in Reverse Micelles. Journal of the American Chemical Society. 2003;125(12):3450-1.

3. Masoomi MY, Morsali A. Applications of metal–organic coordination polymers as precursors for preparation of nano-materials. Coordination Chemistry Reviews. 2012;256(23-24):2921-43.

4. Masoomi MY, Bagheri M, Morsali A, Junk PC. High photodegradation efficiency of phenol by mixed-metal–organic frameworks. Inorganic Chemistry Frontiers. 2016;3(7):944-51.

5. Masoomi MY, Bagheri M, Morsali A. High efficiency of mechanosynthesized Zn-based metal–organic frameworks in photodegradation of congo red under UV and visible light. RSC Advances. 2016;6(16):13272-7.

6. Masoomi MY, Bagheri M, Morsali A. Porosity and dye adsorption enhancement by ultrasonic synthesized Cd(II) based metal-organic framework. Ultrasonics Sonochemistry. 2017;37:244-50.

7. Masoomi MY, Morsali A. Sonochemical synthesis of nanoplates of two Cd(II) based metal–organic frameworks and their applications as precursors for preparation of nano-materials. Ultrasonics Sonochemistry. 2016;28:240-9.

8. Zhang H, Yang D, Li D, Ma X, Li S, Que D. Controllable Growth of ZnO Microcrystals by a Capping-Molecule-Assisted Hydrothermal Process. Crystal Growth & Design. 2005;5(2):547-50.

9. Kuang D, Xu A, Fang Y, Liu H, Frommen C, Fenske D. Surfactant-Assisted Growth of Novel PbS Dendritic Nanostructures via Facile Hydrothermal Process. Advanced Materials. 2003;15(20):1747-50.

10. Kim F, Connor S, Song H, Kuykendall T, Yang P. Platonic Gold Nanocrystals. Angewandte Chemie International Edition. 2004;43(28):3673-7.

11. Aneesh PM, Vanaja KA, Jayaraj MK. Synthesis of ZnO nanoparticles by hydrothermal method. Nanophotonic Materials IV; 2007/09/13: SPIE; 2007.

12. Rai V, Jamuna B. Science Against Microbial Pathogens: Communicating Current Research and Technological Advances, Mendez-Vilas 2011.

13. Das D, Nath BC, Phukon P, Dolui SK. Synthesis and evaluation of antioxidant and antibacterial behavior of CuO nanoparticles. Colloids and Surfaces B: Biointerfaces. 2013;101:430-3.

14. Zhao J, Wang Z, Dai Y, Xing B. Mitigation of CuO nanoparticle-induced bacterial membrane damage by dissolved organic matter. Water Research. 2013;47(12):4169-78.

15. Jammi S, Sakthivel S, Rout L, Mukherjee T, Mandal S, Mitra R, et al. CuO Nanoparticles Catalyzed C−N, C−O, and C−S Cross-Coupling Reactions: Scope and Mechanism. The Journal of Organic Chemistry. 2009;74(5):1971-6.

16. Roger-Estrade J. Le sol, patrimoine vivant. Pour. 2013;220(4):53.

17. Ko JW, Kim S-W, Hong J, Ryu J, Kang K, Park CB. Synthesis of graphene-wrapped CuO hybrid materials by CO2 mineralization. Green Chemistry. 2012;14(9):2391.

18. Borgohain K, Singh JB, Rama Rao MV, Shripathi T, Mahamuni S. Quantum size effects in CuO nanoparticles. Physical Review B. 2000;61(16):11093-6.

19. El-Trass A, ElShamy H, El-Mehasseb I, El-Kemary M. CuO nanoparticles: Synthesis, characterization, optical properties and interaction with amino acids. Applied Surface Science. 2012;258(7):2997-3001.

20. Kumar RV, Diamant Y, Gedanken A. Sonochemical Synthesis and Characterization of Nanometer-Size Transition Metal Oxides from Metal Acetates. Chemistry of Materials. 2000;12(8):2301-5.

21. Lim Y-F, Choi JJ, Hanrath T. Facile Synthesis of Colloidal CuO Nanocrystals for Light-Harvesting Applications. Journal of Nanomaterials. 2012;2012:1-6.

22. Yuan G-Q, Jiang H-F, Lin C, Liao S-J. Shape- and size-controlled electrochemical synthesis of cupric oxide nanocrystals. Journal of Crystal Growth. 2007;303(2):400-6.

23. Poizot P, Hung C-J, Nikiforov MP, Bohannan EW, Switzer JA. An Electrochemical Method for CuO Thin Film Deposition from Aqueous Solution. Electrochemical and Solid-State Letters. 2003;6(2):C21.

24. Son DI, You CH, Kim TW. Structural, optical, and electronic properties of colloidal CuO nanoparticles formed by using a colloid-thermal synthesis process. Applied Surface Science. 2009;255(21):8794-7.

25. Wang H, Xu J-Z, Zhu J-J, Chen H-Y. Preparation of CuO nanoparticles by microwave irradiation. Journal of Crystal Growth. 2002;244(1):88-94.

26. Fukui T, Ohara S, Okawa H, Hotta T, Naito M. Properties of NiO cathode coated with lithiated Co and Ni solid solution oxide for MCFCs. Journal of Power Sources. 2000;86(1-2):340-6.

27. Izaki Y, Mugikura Y, Watanabe T, Kawase M, Selman JR. Direct observation of the oxidation nickel in molten carbonate. Journal of Power Sources. 1998;75(2):236-43.

28. Hotovy I, Huran J, Spiess L, Hascik S, Rehacek V. Preparation of nickel oxide thin films for gas sensors applications. Sensors and Actuators B: Chemical. 1999;57(1-3):147-52.

29. Bi H, Li S, Zhang Y, Du Y. Ferromagnetic-like behavior of ultrafine NiO nanocrystallites. Journal of Magnetism and Magnetic Materials. 2004;277(3):363-7.

30. Ichiyanagi Y. Magnetic properties of NiO nanoparticles. Physica B: Condensed Matter. 2003;329-333:862-3.

31. Biju V, Abdul Khadar M. Fourier transform infrared spectroscopy study of nanostructured nickel oxide. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 2003;59(1):121-34.

32. Wang Guo-Zhong ZL-D, Mou Ji-Mei. Preparation and Optical Absorption of Nanometr-sized NiO Powder. Acta Phys -Chim Sin. 1997; 13(05): 445-8.

33. Chen C-T, Cha I, Hsieh SJ. Thermal Stability of Robust Unsymmetrical Copperporphyrins with Multiple Diphenylamino and Nitro Substituents. Journal of the Chinese Chemical Society. 1998;45(6):741-8.

34. Srivastava PC, Singh UP. Hydrogen in semiconductors. Bulletin of Materials Science. 1996;19(1):51-60.

35. Che SL, Takada K, Takashima K, Sakurai O, Shinozaki K, Mizutani N. Journal of Materials Science. 1999;34(6):1313-8.

36. Katz JL, Miquel PF. Syntheses and applications of oxides and mixed oxides produced by a flame process. Nanostructured Materials. 1994;4(5):551-7.

37. Link J. Normalistische Kollektivsymbolik und der High-Tech-Vehikel-Körper. Versuch über den Normalismus: VS Verlag für Sozialwissenschaften; 1997. p. 346-67.

38. Wang W, Liu Y, Xu C, Zheng C, Wang G. Synthesis of NiO nanorods by a novel simple precursor thermal decomposition approach. Chemical Physics Letters. 2002;362(1-2):119-22.

39. Xiang L, Deng XY, Jin Y. Experimental study on synthesis of NiO nano-particles. Scripta Materialia. 2002;47(4):219-24.

40. Wei Z, Qiao H, Yang H, Zhang C, Yan X. Characterization of NiO nanoparticles by anodic arc plasma method. Journal of Alloys and Compounds. 2009;479(1-2):855-8.

41. Deng X. Preparation of nano-NiO by ammonia precipitation and reaction in solution and competitive balance. Materials Letters. 2004;58(3-4):276-80.

42. Mercury 1.4.1, Copyright Cambridge Crystallographic Data Centre. 12 Union Road, Cambridge, CB2 1EZ, UK2001-2005.

43. Bordas B, Sohar P, Matolcsy G, Berencsi P. Synthesis and antifungal properties of dithiocarboxylic acid derivatives. II. Novel preparation of 2-alkylamino-1-cyclopentene-1-dithiocarboxylic acids and some of their derivatives. The Journal of Organic Chemistry. 1972;37(11):1727-30.

44. Nag K, Joardar DS. Metal complexes of sulphur-nitrogen chelating Agents. I. 2-aminocyclo-pentene-l-dithiocarboxylic acid complexes of Ni(II), Pd(II) and Pt(II). Inorganica Chimica Acta. 1975;14:133-41.

45. Pereira E, Gomes L, de Castro B. Synthesis, spectroscopic and electrochemical study of nickel(II) complexes with tetradentate asymmetric Schiff bases derived from salicylaldehyde and methyl-2-amino-1-cyclopentenedithiocarboxylate. Inorganica Chimica Acta. 1998;271(1-2):83-92.

46. Mondal SK, Paul P, Roy R, Nag K. Metal complexes of sulphur-nitrogen chelating agents. Part 14. Nickel(II), palladium(II), copper(II), cobalt(II), and cobalt(III) complexes of the tetradentate schiff bases having ONNS donor sites. Transition Metal Chemistry. 1984;9(7):247-50.

47. Asadi M, Mohammadi K, Esmaielzadeh S, Etemadi B, Fun H-K. Synthesis, characterization and thermodynamic study of copper(II) complexes with unsymmetric tetradentate Schiff base ligands and X-ray structure of {methyl-2-[N-[2-(5-chloro-2-phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylatecopper(II). Inorganica Chimica Acta. 2009;362(14):4913-20.

48. Asadi M, Mohammadi K, Esmaielzadeh S, Etemadi B, Fun HK. Some new Schiff base ligands giving a NNOS coordination sphere and their nickel(II) complexes: Synthesis, characterization and complex formation. Polyhedron. 2009;28(8):1409-18.