The Schiff bases, L1, L2, and L3, are synthesized from the condensation of 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one (L) with 2-aminopyridine (1), p-phenylenediamine (2), and o-phenylenediamine (3). The prepared Schiff bases react with lanthanum (III), neodymium (III), and erbium (III) nitrate to give complexes with stoichiometric ratio (1？:？1) (ligand？:？metal). The binuclear complexes of Er(III) with L3 and the three metal ions with L2 are separated. The complexes have been characterized by elemental analysis, molar conductance, electronic absorption, and infrared, 1H-NMR spectral studies. The presence of hydrated and coordinated water molecules is inferred from thermogravimetric analysis. Thermal degradation studies show that the final product is the metal oxide. The luminescence properties of the Nd(III) and Er(III) complexes in dimethylformamide (DMF) solutions were investigated. 1. Introduction The coordination chemistry of lanthanide (III) ions is rapidly increasing, owing to the relevance of these compounds in basic and applied research in different scientific areas ranging from chemistry to material science to the life science [1–8]. Lanthanide coordination compounds are the subject of intense research efforts owing to their unique structures and their potential applications in advanced materials such as Ln-doped semiconductors [9], magnetic [10, 11], catalytic [12], fluorescent [13, 14], and nonlinear optical materials [15, 16]. It has been shown that ligands containing both nitrogen and oxygen donor atoms are good building blocks for the formation of various lanthanide coordination compounds [17–24]. Schiff bases continue to occupy an important position as ligands in metal coordination chemistry [25], even almost a century since their discovery. Schiff base metal complexes have played a key role in the development of coordination chemistry, resulting in an enormous number of publications, ranging from pure synthetic work to modern physicochemical and biochemically relevant studies of metal complexes [26]. The lanthanide cations can promote Schiff base condensation and can give access to complexes of otherwise inaccessible ligands. It is essential to design appropriate ligands to optimize the luminescence properties of lanthanide ions by facilitating the well-known light conversion process, which show to be efficient ligand-to-metal energy transfer process [27]. In view of this, we have designed a series of Schiff bases, which can enhance the luminescence properties of lanthanide ions. In the present work, the complexes of rare earth
References
[1]
N. Sabbatini, M. Guardigli, and J. M. Lehn, “Luminescent lanthanide complexes as photochemical supramolecular devices,” Coordination Chemistry Reviews, vol. 123, no. 1-2, pp. 201–228, 1993.
[2]
P. A. Vigato and S. Tamburini, “The challenge of cyclic and acyclic schiff bases and related derivatives,” Coordination Chemistry Reviews, vol. 248, no. 17-20, pp. 1717–2128, 2004.
[3]
V. Alexander, “Design and synthesis of macrocyclic ligands and their complexes of lanthanides and actinides,” Chemical Reviews, vol. 95, no. 2, pp. 273–342, 1995.
[4]
C. Benelli and D. Gatteschi, “Magnetism of lanthanides in molecular materials with transition-metal ions and organic radicals,” Chemical Reviews, vol. 102, no. 6, pp. 2369–2387, 2002.
[5]
A. D？ssing, “Luminescence from lanthanide(3+) ions in solution,” European Journal of Inorganic Chemistry, no. 8, pp. 1425–1434, 2005.
[6]
J. C. G. Bünzli and C. Piguet, “Lanthanide-containing molecular and supramolecular polymetallic functional assemblies,” Chemical Reviews, vol. 102, no. 6, pp. 1897–1928, 2002.
[7]
A. D. Sherry and C. F. G. C. Geraldes, “Lanthanide probes in life: chemical and earth sciences,” in Theory and Practice, G. R. Choppin, Ed., vol. 93, Elsevier, Amsterdam, The Netherlands, 1989.
[8]
D. Parker, R. S. Dickins, H. Puschmann, C. Crossland, and J. A. K. Howard, “Being excited by lanthanide coordination complexes: aqua species, chirality, excited-state chemistry, and exchange dynamics,” Chemical Reviews, vol. 102, no. 6, pp. 1977–2010, 2002.
[9]
M. Taniguchi and K. Takahei, “Optical properties of the dominant Nd center in GaP,” Journal of Applied Physics, vol. 73, no. 2, pp. 943–947, 1993.
[10]
J. P. Costes, F. Dahan, A. Dupuis, and J. P. Laurent, “A general route to strictly dinuclear Cu(II)/Ln(III) complexes. Structural determination and magnetic behavior of two Cu(II)/Gd(III) complexes,” Inorganic Chemistry, vol. 36, no. 16, pp. 3429–3433, 1997.
[11]
A. Bencini, C. Benelli, A. Caneschi, R. L. Carlin, A. Dei, and D. Gatteschi, “Crystal and molecular structure of and magnetic coupling in two complexes containing gadolinium(III) and copper(II) ions,” Journal of the American Chemical Society, vol. 107, no. 26, pp. 8128–8136, 1985.
[12]
J. Lisowski and P. Starynowicz, “Heterodinuclear macrocyclic complexes containing both nickel(II) and lanthanide(III) ions,” Inorganic Chemistry, vol. 38, no. 6, pp. 1351–1355, 1999.
[13]
V. Alexander, “Design and synthesis of macrocyclic ligands and their complexes of lanthanides and actinides,” Chemical Reviews, vol. 95, no. 2, pp. 273–342, 1995.
[14]
V. De Zea Bermudez, R. A. Sá Ferreira, L. D. Carlos, C. Molina, K. Dahmouche, and S. J. L. Ribeiro, “Coordination of Eu3+ ions in siliceous nanohybrids containing short polyether chains and bridging urea cross-links,” Journal of Physical Chemistry B, vol. 105, no. 17, pp. 3378–3386, 2001.
[15]
C. Reinhard and H. U. Güdel, “High-resolution optical spectroscopy of Na3[Ln(dpa)3]·13H2O with Ln = Er3+, Tm3+, Yb3+,” Inorganic Chemistry, vol. 41, no. 5, pp. 1048–1055, 2002.
[16]
C. V. K. Sharma and R. D. Rogers, “Molecular chiness blinds': Self-organization of tetranitrato lanthanide complexes into open, chiral hydrogen-bomded networks,” Chemical Communications, no. 1, pp. 83–84, 1999.
[17]
Y. Liang, R. Cao, W. Su, M. Hong, and W. Zhang, “Syntheses, structures, and magnetic properties of two gadolinium (III)—Copper (II) coordination polymers by a hydrothermal reaction,” Angewandte Chemie—International Edition, vol. 39, no. 18, pp. 3304–3307, 2000.
[18]
Y. Liang, M. Hong, W. Su, R. Cao, and W. Zhang, “Preparations, structures, and magnetic properties of a series of novel copper(II)-lanthanide(III) coordination polymers via hydrothermal reaction,” Inorganic Chemistry, vol. 40, no. 18, pp. 4574–4582, 2001.
[19]
R. Cao, D. Sun, Y. Liang, M. Hong, K. Tatsumi, and Q. Shi, “Syntheses and characterizations of three-dimensional channel-like polymeric lanthanide complexes constructed by 1,2,4,5-benzenetetracarboxylic acid,” Inorganic Chemistry, vol. 41, no. 8, pp. 2087–2094, 2002.
[20]
Z. Wang, C.-M. Jin, T. Shao et al., “Syntheses, structures, and luminescence properties of a new family of three-dimensional open-framework lanthanide coordination polymers,” Inorganic Chemistry Communications, vol. 5, no. 9, pp. 642–648, 2002.
[21]
L. Pan, X. Huang, J. Li, Y. Wu, and N. Zheng, “Novel single- and double-layer and three-dimensional structures of rare- Earth metal coordination polymers: the effect of lanthanide contraction and acidity control in crystal structure formation,” Angewandte Chemie—International Edition, vol. 39, no. 3, pp. 527–530, 2000.
[22]
J. P. Costes, J. M. Clemente, F. Dahan, F. Nicodème, and M. Verelst, “Unprecedented ferromagnetic interaction in homobinuclear erbium and gadolinium complexes: structural and magnetic studies,” Angewandte Chemie—International Edition, vol. 41, no. 2, pp. 323–325, 2002.
[23]
A. Ouchi, Y. Suzuki, Y. Ohki, and Y. Koizumi, “Structure of rare earth carboxylates in dimeric and polymeric forms,” Coordination Chemistry Reviews, vol. 92, pp. 29–43, 1988.
[24]
A. Panagiotopoulos, T. F. Zafiropoulos, S. P. Perlepes et al., “Molecular structure and magnetic properties of acetato-bridged lanthanide(III) dimers,” Inorganic Chemistry, vol. 34, no. 19, pp. 4918–4920, 1995.
[25]
F. Aydogan, N. ？cal, Z. Turgut, and C. Yolacan, “Transformations of aldimines derived from pyrrole-2-carbaldehyde. Synthesis of thiazolidino-fused compounds,” Bulletin of the Korean Chemical Society, vol. 22, no. 5, pp. 476–480, 2001.
[26]
M. A. V. Ribeiro Da Silva, M. D. M. C. Ribeiro Da Silva, M. J. S. Monte, J. M. Gon？alves, and E. M. R. Fernandes, “Energetics of metal-ligand binding in copper(II) and nickel(II) complexes of two Schiff bases,” Journal of the Chemical Society—Dalton Transactions, no. 7, pp. 1257–1262, 1997.
[27]
B.-D. Wang, Z.-Y. Yang, D.-W. Zhang, and Y. Wang, “Synthesis, structure, infrared and fluorescence spectra of new rare earth complexes with 6-hydroxy chromone-3-carbaldehyde benzoyl hydrazone,” Spectrochimica Acta A, vol. 63, no. 1, pp. 213–219, 2006.
[28]
M. T. El-Haty, F. A. Adam, A. E. Mohamed, and A. A. Gabr, “Electronic spectra of some heterocyclic schiff bases derived from 3-amino-1,2,4-triazole,” Journal of the Indian Chemical Society, vol. 67, no. 9, pp. 743–747, 1990.
[29]
A. L. El-Ansary, H. M. Abdel-Fattah, and N. S. Abdel-Kader, “Synthesis and characterization of tetradentate bis-Schiff base complexes of di- and tri-valent transition metals,” Journal of Coordination Chemistry, vol. 61, no. 18, pp. 2950–2960, 2008.
[30]
A. I. Vogel, Practical Organic Chemistry Including Quantitative Organic Analysis, Longmans, London, UK, 5th edition, 1991.
[31]
W. J. Geary, “The use of conductivity measurements in organic solvents for the characterisation of coordination compounds,” Coordination Chemistry Reviews, vol. 7, no. 1, pp. 81–122, 1971.
[32]
F. B. Tamboura, M. Diop, M. Gaye, A. S. Sall, A. H. Barry, and T. Jouini, “X-ray structure and spectroscopic properties of some lanthanides(III) complexes derived from 2,6-diacetylpyridine-bis(benzoylhydrazone),” Inorganic Chemistry Communications, vol. 6, no. 8, pp. 1004–1010, 2003.
[33]
L. J. Bellamy, The Infrared Spectra of Complex Molecules, Chapman and Hall, London, UK, 1975.
[34]
B. S. Saraswat, G. Srivastava, and R. C. Mehrotra, “Schiff base complexes of organotin(IV). Reactions of trialkyltin(IV) chlorides and alkoxides with N-substituted salicylideneimines,” Journal of Organometallic Chemistry, vol. 129, no. 2, pp. 155–161, 1977.
[35]
S. J. Gruber, C. M. Harris, and E. Sinn, “Metal complexes as ligands-IV [1,2,3]. Bi- and Tri- nuclear complexes derived from metal complexes of tetradentate salicylaldimines,” Journal of Inorganic and Nuclear Chemistry, vol. 30, no. 7, pp. 1805–1830, 1968.
[36]
R. C. Mourya, R. Varma, and P. Shukla, “Synthesis of nitrato complexes of lanthanum(III) with schiff bases derived from 4-antipyrinecarboxaldehyde and aromatic amines,” Journals of the Indian Chemical Society, vol. 74, no. 9, pp. 789–790, 1997.
[37]
A. M. Donia and H. A. El-Boraey, “Preparation of highly insulating dimeric and polymeric metal complexes with higher thermal stability in the solid state,” Journal of Analytical and Applied Pyrolysis, vol. 63, no. 1, pp. 69–84, 2002.
[38]
S. K. Sengupta, O. P. Pandey, B. K. Srivastava, and V. K. Sharma, “Synthesis, structural and biochemical aspects of titanocene and zirconocene chelates of acetylferrocenyl thiosemicarbazones,” Transition Metal Chemistry, vol. 23, no. 4, pp. 349–353, 1998.
[39]
B.-D. Wang, Z.-Y. Yang, and T.-R. Li, “Synthesis, characterization, and DNA-binding properties of the Ln(III) complexes with 6-hydroxy chromone-3-carbaldehyde-(2′-hydroxy) benzoyl hydrazone,” Bioorganic and Medicinal Chemistry, vol. 14, no. 17, pp. 6012–6021, 2006.
[40]
S. P. Sinha, Complexes of the Rare Earths, Pergamon Press, Oxford, UK, 1966.
[41]
U. K. Pandey, O. P. Pandey, S. K. Sengupta, and S. C. Tripathi, “Syntheses and spectroscopic studies on tetraaza macrocyclic complexes of praseodymium(III),” Polyhedron, vol. 6, no. 7, pp. 1611–1617, 1987.
[42]
C. N. R. Rao, Chemical Application of Infrared Spectroscopy, Academic Press, New York, NY, USA, 1963.
[43]
G. F. Liu, Y. N. Zhao, and X. X. Liu, “Preparation and characterization of coordination compounds on rare earth nitrate with Schiff base derived from o-vanillin and 1-naphthylamine,” Acta Chimica Sinica, vol. 50, no. 5, pp. 473–478, 1992.
[44]
Z. A. Tahaa, A. M. Ajlounia, K. A. Al-Hassan, A. K. Hijazi, and A. B. Faiq, “Syntheses, characterization, biological activity and fluorescence properties of bis-(salicylaldehyde)-1,3-propylenediimine schiff base ligand and its lanthanide complexes,” Spectrochimica Acta Part A, vol. 81, no. 1, pp. 317–323, 2011.
[45]
X. M. He and C. H. Song, Chinese Journal of Synthetic Chemistry, vol. 10, p. 245, 2002.
[46]
R. Yang, S.-Y. He, W.-T. Wu, Q.-Z. Shi, and D.-Q. Wang, “Crystal structure, fluorescence properties and thermal stability of supra-molecule complex [Eu(C10H9N2O4)·(C10H8N2O4)·(H2O)3]2·phen·4H2O,” Chemical Journal of Chinese Universities, vol. 26, no. 3, pp. 401–406, 2005.
[47]
Y. Hirashima, K. Kanetsuki, I. Yonezu, k. Kamakura, and J. Shiokawa, “Lanthanoid nitrate complexes with some polyethylene glycols and glymes,” Bulletin of the Chemical Society of Japan, vol. 56, no. 3, pp. 738–743, 1983.
[48]
E. Katsoulakou, V. Bekiari, C. P. Raptopoulouc et al., “Dinuclear versus tetranuclear cluster formation in zinc(II) nitrate/di-2-pyridyl ketone chemistry: synthetic, structural and spectroscopic studies,” Spectrochimica Acta A, vol. 61, no. 7, pp. 1627–1638, 2005.
[49]
Y.-L. Zhang, W.-S. Liu, W. Dou, and W.-W. Qin, “Synthesis and infrared and fluorescence spectra of new europium and terbium polynuclear complexes with an amide-based 1,10-phenanthroline derivative,” Spectrochimica Acta A, vol. 60, no. 8-9, pp. 1707–1711, 2004.
[50]
K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, Wiley Intersciences, New York, NY, USA, 3rd edition, 1978.
[51]
A. P. Hunter, A. M. J. Lees, and A. W. G. Platt, “Synthesis, structures and mass spectrometry of lanthanide nitrate complexes with tricyclohexylphosphine oxide,” Polyhedron, vol. 26, no. 17, pp. 4865–4876, 2007.
[52]
Y. M. Issa, A. L. El-Ansary, O. E. Sherif, and M. M. El-Ajily, “Separation and spectroscopic characterization of new metal chelates of 8-arylazo-6-formyl-7-hydroxy-5-methoxy-2-methyl chromones,” Transition Metal Chemistry, vol. 22, no. 5, pp. 441–446, 1997.
[53]
A. M. El-Roudi, Bulletin of the Faculty of Science, vol. 18, p. 77, 1989.
[54]
F. A. Aly, S. M. Abu-El-Wafa, R. M. Issa, and F. A. El-Sayed, “On the formation of mononuclear and binuclear complexes of pentadentate N4O2 schiff base ligands with Co(II), Ni(II) and Cu(II) ions: TGA, spectral and conductance studies,” Thermochimica Acta, vol. 126, pp. 235–244, 1988.
[55]
G. Rijulal and P. Indrasenan, “Synthesis and characterization of some lanthanide(III) complexes with 4-[N-(2-methoxybenzylimine)formyl]-2, 3-dimethyl-1-phenyl-3-pyazolin-5-one,” Journal of Rare Earths, vol. 25, no. 6, pp. 670–673, 2007.
[56]
G. Zhao, Y. Feng, and Y. Wen, “Syntheses, crystal structures and kinetic mechanisms of thermal decomposition of rare earth complexes with Schiff base derived from o-vanillin and p-toluidine,” Journal of Rare Earths, vol. 24, no. 3, pp. 268–275, 2006.
[57]
R. D. Archer, H. Chen, and L. C. Thompson, “Synthesis, characterization, and luminescence of europium(III) Schiff base complexes,” Inorganic Chemistry, vol. 37, no. 8, pp. 2089–2095, 1998.
