Table of Contents Author Guidelines Submit a Manuscript
Journal of Chemistry
Volume 2013 (2013), Article ID 159125, 5 pages
http://dx.doi.org/10.1155/2013/159125
Research Article

Synthesis, Crystal Structure and Thermal Properties of Lead(II) Complex with Bathophenanthroline and Benzoyltrifluoroacetonate Ligands

1Department of Chemistry, Islamic Azad University, Karaj Branch, Karaj, Iran
2Department of Chemistry, Payame Noor University, Tehran 19395-3697, Iran
3Department of Chemistry, Atatürk University, 25240 Erzurum, Turkey
4Department of Chemistry, Shahid Beheshti Technical Faculty, Technical and Vocational University, Urmia, Iran

Received 13 April 2012; Accepted 15 May 2012

Academic Editor: Jorge Barros-Velazquez

Copyright © 2013 Saeideh Hosseini et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A new Pb(II) complex, [ P b ( b p ) 2 ( b t f a ) 2 ]   1, has been synthesized with bathophenanthroline (bp) and benzoyltrifluoroacetone (Hbtfa) and characterized by elemental analysis IR and 1 H NMR spectroscopy as well as by thermal properties and X-ray crystallography. The coordination number of the Pb(II) ions in 1 is eight, with the P b N 4 O 4 coordination polyhedron containing a stereochemically “inactive” electron lone pair with holodirected coordination spheres. In solid state, there are π⋯π, C–HF, C–HO, and FF interactions between adjacent units to generate 3D supramolecular structure.

1. Introduction

The Pb2+ cation has a [Xe]4f145d106s2 electronic configuration and exhibits an especially versatile character with respect to the HSAB theory [1] for which it appears as a borderline acid, able to bind to wide families of ligands [2] within very flexible coordination modes [3, 4]. The coordination chemistry of Pb(II) is mainly determined by two factors: (i) its large size (ionic radius 1.32 Å [5], covalent radius 1.54 Å [5] and van der Waals radius 2.00 Å [6]), which permits coordination numbers that range from quasione [7] to twelve [8] and (ii) its 6s electron pair, which may or may not play a role in the stereochemistry of lead(II) complexes [9]. The lone-pair activity can depend on (1) hard or soft ligands, (2) attractive or repulsive interactions among ligands, and (3) the number of electrons (charge) transferred from the ligands to the metal atom [3]. It has been proposed that holodirected structures do not necessarily exclude an inactive lone-pair [10].

The design and synthesis of new materials with desired chemical and physical properties have been of interest, and this involves the generation and study of structural motifs in crystals, which is essentially guided by precise topological control through the manipulation of weak intermolecular interactions [11]. There is a rich variety of intermolecular interactions that serve as tools in engineering such molecular assemblies [12]. Recently, in an effort to explore the role of weak intermolecular interactions among ligands in the stereochemical activity of valence shell electron lone pairs, the lead(II) complexes with fluorinated β-diketonate and neutral aromatic diamine-chelating ligands have been synthesized and characterized by X-ray crystal structure determination [1325]. Fluorinated β-diketonate ligands are very good probes because of their ability for forming intermolecular C–HF, FF, and π⋯π interactions. In this paper we report the synthesis and crystal structures of [Pb(bp)2(btfa)2] 1, where bp and btfa are the abbreviations of bathophenanthroline and benzoyltrifluoroacetonate ligands, respectively.

2. Experimental

2.1. Material and Measurements

All chemicals were reagent grade and used without further purification. FT-IR spectra were collected on a Mattson 1000 spectrophotometer using KBr pellets in the range of 4000–450 cm−1. Elemental analyses (CHN) were performed using a Carlo ERBA model EA 1108 analyzer and 1H NMR spectra were obtained with a Bruker spectrometer at 250 MHz in [D6]DMSO. Thermal analyses were carried out on a Perkin-Elmer instrument (Seiko Instruments).

2.2. Crystallography

For the crystal structure determination, the single crystal of compound 1 was used for data collection on a four-circle Rigaku R-AXIS RAPID-S diffractometer equipped with a two-dimensional area IP detector. The graphitemonochromatized Mo-Ka radiation ( 𝜆 = 0 . 7 1 0 7 3  Å) and oscillation scans technique with Δ 𝜔 = 5 ° for one image were used for data collection. The lattice parameters were determined by the least-squares methods on the basis of all reflections with 𝐹 2 > 2 𝜎 ( 𝐹 2 ) . Integration of the intensities, correction for Lorentz, polarization effects, and cell refinement was performed using CrystalClear (Rigaku/MSC Inc., 2005) software [26]. The structures were solved by direct methods using SHELXS-97 [27] and refined by a full-matrix least-squares procedure using the SHELXL-97 program [27]. The final difference Fourier maps showed no peaks of chemical significance. Details of crystal data, data collection, structure solutions, and refinements are given in Table 1.

tab1
Table 1: Crystal data and structure refinement for (1).
2.3. Preparation of [Pb(bp)2(btfa)2] (1)

Bathophenanthroline (0.184 g, 1 mmol) was placed in one arm of a branched tube [28] and lead(II) acetate (0.190 g, 0.5 mmol), and “Hbtfa” (0.206 g, 1 mmol) in the other. Methanol and ethanol ratio (2 : 3) was carefully added to fill arms, the tube sealed, and the ligand containing arm immersed in a bath at 60°C while the other was at ambient temperature. After 3 days, crystals had been deposited in the cooler arm which were filtered off, washed with acetone and ether, and dried in air, yield: 56%. M.p. 250°C Analysis: found: C: 62.54, H: 3.20, N: 4.51%. Calculated for C68H44F6N4O6Pb: C: 62.66, H: 3.38, N, 4.30%. IR (cm−1) selected bands: 680 (versus), 845 (versus) (C–H), 956 (m), 1032 (s), 1156 (s), 1224 (versus, C–F), 1400, 1480, 1585 (s, aromatic ring), 1629 (versus, C=O), 3062 (w, C–H aromatic). 1H NMR (DMSO, δ): 9.00–9.20 (m, 4H), 7.00-8.00 (m, 18H), 5.86 (s, 2H, =CH–) ppm. 13C NMR (DMSO, δ): 97.33 (=CH–), 117.60 (–CF3), 124.52–138.11 (aromatic carbons), 137.57–153.10 ((hetero)aromatic C-atoms), 168.50 (C=O), 179.90 (C=O) ppm.

3. Result and Discussion

3.1. Preparation and Thermal Behavior

The reaction conditions always have great effect on the single-crystal growth. Interestingly, the molar ratio of solvents is important for the growth of single crystals.

In order to examine the thermal stability of the compound, thermal gravimetric (TG) and differential thermal analyses (DTA) were carried out for complex 1 between 30 and 800°C in the static atmosphere of air (Figure 1). The TG curve of compound 1 indicates that this compound decomposes at 300°C (1 has good thermal stability related to reported structures of Pb(II) with β-diketonates [1325]). The ligands bp and btfa decompose at 300–800°C with exothermic effect. The solid residue formed is suggested to be PbO (observed 19.50%, calcd. 17.12%).

159125.fig.001
Figure 1: Thermal behavior of [Pb(bp)2(btfa)2] (1).
3.2. Structural Description

The solid-state structure of compound 1 was determined by single-crystal X-ray diffraction. The Pb(II) complex crystallizes in the monoclinic space group C2/c (Table 1). The asymmetric unit contains half of the molecule and it has the 𝐶 2 symmetry (Figure 2). Selected bond lengths, and angles are listed in Table 2. The molecule contains one Pb(II), two “Bathophenanthroline” ligands and two benzoyltrifluoroacetonates anions (Figure 2(a)). The coordination number of Pb(II) in this complex is eight and each lead atom is chelated by four nitrogens of “bp” ligands with Pb-N distances of 2.779 (3), 2.871 (3) Å, and four oxygens of two ‘‘btfa’’ anions with Pb-O distances of 2.482 (4) and 2.506 (4) Å (Figure 2(b)).

tab2
Table 2: Selected bond lengths (Å) and angles (°) for (1).
fig2
Figure 2: (a) Ortep diagram of complex 1. (b) Representation of the hole in the coordination sphere of 1. The coordination geometry is as holodirected [symmetry code ( 𝑖 ): 𝑥 , 𝑦 , 1 / 2 𝑧 ].

The arrangement of bathophenanthrolines and benzoyltrifluoroacetonates does not suggest any gap or hole in coordination geometry around the metal ion (Figure 1(b)), indicating that the lone pair of electrons on lead(II) is inactive and the geometry around Pb(II) sphere is holodirected [29]. According to suggestions of Shimoni-Livny et al. [3, 4] the hemidirected geometry is present in all lead(II) compounds with low coordination numbers (2–5) and also quite common for coordination numbers of 6 to 8, while holodirected geometry becomes dominant at high coordination numbers of 9 and 10. Since the presence of four bulk ligands increases steric crowding around lead(II) and results in strong interligand repulsions. This may be the reason of the disappearance of the gap in the coordination polyhedron, thereby resulting in less common holodirected geometry.

A search was generally made for intermolecular approaches in the complex [Pb(bp)2(btfa)2] (1). The interesting feature is that there are FF interactions, the weak hydrogen bonding, between the flourine atoms of btfa with the distances of F2F2( 1 𝑥 , 𝑦 , 1 / 2 𝑧 ) = 2.868 Å and FH–C, OH–C interactions (Table 3) values suggest strong interactions within this class of weak noncovalent contacts [30]. There are ππ stacking interactions between the aromatic rings that belong to adjacent chains in 1. The interplanar distances range between aromatic rings in this compound is the normal ππ stacking interaction (Table 3) [31, 32]. Consequently, FF, C–HO [33], C–HF [3437], and ππ interactions allow the mononuclear complexes to form a hybrid three-dimensional network (Figure 3).

tab3
Table 3: Inter- and intramolecular interactions for 1.
159125.fig.003
Figure 3: Perspective view of the complex down the a-axis, packing of mononuclear complex 1 forms 3D networks via ππ interactions.

In spite of the recent structural study of fluorine β-diketonates complexes of Pb(II) with heteroaromatic ligands (1,10-phenanthroline,2,9-dimethyl-1,10-phenanthroline) and other Pb(II) compounds using N-donor ligands and diketonates [1325], this complex is as discrete mononuclear complex, and coordination geometry of 1 is holodirected. In recent structural study of dinuclear complexes, fluorine β-diketonates anion has a role of bridging ligand [1325].

The obvious question then is whether the weak interactions have stretched coordinate bonds to result in ligand stacking or whether it is the stacking interaction which has imposed a positioning of the donor atoms for forming the weak interactions in the packing. In conclusion, a subtle interplay among lone-pair activity and strong and weak interactions appears to control the packing motifs in the crystal structure of 1. Our current results suggest that while interactions involving “organic fluorine” have a significant influence in generating supramolecular assemblies in inorganic solids, the general use of these interactions for the a priori prediction of packing motifs is yet to be fully understood and harnessed.

Disclosure

Crystallographic data for the structure reported in the paper have been deposited in the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-864329 for the complex 1. Copies of this information can be obtained for free from The Director, CCDC, 12 Union Road, Cambridge, CB2 IEZ, UK (fax: þ44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk/).

Acknowledgment

Support of this investigation by Payame Noor University is gratefully acknowledged by F. Marandi.

References

  1. R. G. Pearson, “Absolute electronegativity and hardness: application to inorganic chemistry,” Inorganic Chemistry, vol. 27, pp. 734–740, 1998. View at Google Scholar
  2. M. Kaupp and P. V. R. Schleyer, “Ab Initio study of structures and stabilities of substituted lead compounds. Why is inorganic lead chemistry dominated by PbII but organolead chemistry by PbIV?” Journal of the American Chemical Society, vol. 115, no. 3, pp. 1061–1073, 1993. View at Google Scholar · View at Scopus
  3. L. Shimoni-Livny, J. P. Glusker, and C. W. Brock, “Lone pair functionality in divalent lead compounds,” Inorganic Chemistry, vol. 37, pp. 1853–1867, 1998. View at Google Scholar
  4. L. Puskar, P. E. Barran, B. J. Duncombe, D. Chapman, and A. J. Stace, “Gas phase study of the chemistry and coordination of Pb(II) in the presence of oxygen-, nitrogen-, sulphur-, and phosphorous-donating ligands,” Journal of Physical Chemistry A, vol. 109, no. 1, pp. 273–282, 2005. View at Google Scholar
  5. J. Emsley, The Elements, Oxford University Press, New York, NY, USA, 1988.
  6. J. E. Huheey, E. A. Keiter, and R. L. Keiter, Inorganic Chemistry, Harper Collins College Publishers, New York, NY, USA, 4th edition, 1993.
  7. S. Hino, M. Brynda, A. D. Phillips, and P. P. Power, “Synthesis and characterization of a quasi-one-coordinate lead cation,” Angewandte Chemie, vol. 43, no. 20, pp. 2655–2658, 2004. View at Publisher · View at Google Scholar · View at Scopus
  8. C. E. Holloway and M. Melnik, “Lead coordination and organometallic compounds: classification and analysis of crystallographic and structural data,” Main Group Metal Chemistry, vol. 20, no. 7, pp. 399–495, 1997. View at Google Scholar · View at Scopus
  9. R. D. Hancock, A. F. Williams, C. Floriani, and A. E. Merbach, Eds., Perspectives in Coordination Chemistry, VCHA, VCH, Basle, Switzerland, 1992.
  10. C. Janiak, S. Temizdemir, T. G. Scharmann, A. Schmalstieg, and J. Demtschuk, “Hydrotris(1,2,4-triazolyl)borato complexes with the main group elements Ca, Sr, and Pb - Unexpectedly bent ML2 structures and a stereochemically inactive lone pair at lead(II),” Zeitschrift fur Anorganische und Allgemeine Chemie, vol. 626, no. 10, pp. 2053–2062, 2000. View at Google Scholar · View at Scopus
  11. K. Müller-Dethlefs and P. Hobza, “Noncovalent interactions: a challenge for experiment and theory,” Chemical Reviews, vol. 100, no. 1, pp. 143–167, 2000. View at Google Scholar · View at Scopus
  12. J. M. Lehn, “Supramolecular chemistry,” Science, vol. 260, no. 5115, pp. 1762–1763, 1993. View at Google Scholar · View at Scopus
  13. F. Marandi, Z. Nikpey, M. Khosravi, H.-K. Fun, and M. Hemamalini, “Synthesis and characterization of lead(II) complexes with substituted 2,2-bipyridines, trifluoroacetate, and furoyltrifluoroacetonate,” Journal of Coordination Chemistry, vol. 64, pp. 3012–3021, 2011. View at Google Scholar
  14. F. Marandi and A. Morsali, “Sonochemical syntheses and characterization of a new nano-structured one-dimensional lead(II) coordination polymer with 4,4,4-trifluoro-1-phenyl-1,3-butandione,” Inorganica Chimica Acta, vol. 370, no. 1, pp. 526–530, 2011. View at Google Scholar
  15. F. Marandi, R. Rutvand, M. Rafiee, J. H. Goh, and H.-K. Fun, “Synthesis, properties and crystal structures of new binuclear lead(II) complexes based on phenyl, naphthyl-containing fluorine beta-diketones and substituted 2,2-bipyridines,” Inorganica Chimica Acta, vol. 363, no. 14, pp. 4000–4007, 2010. View at Google Scholar
  16. F. Marandi, Z. Nikpey, J. H. Goh, and H.-K. Fun, “Synthesis and crystal structure of lead(II) thenoyltrifluoroacetonate complexes with substituted 2,2-bipyridines: interplay of intermolecular interactions in crystals,” Zeitschrift Fur Naturforschung, vol. 65, pp. 128–134, 2010. View at Google Scholar
  17. F. Marandi and H. Krautscheid, “Synthesis and characterization of lead(II) complexes with the 4-methoxybenzoyltrifluoroacetonate ligand,” Zeitschrift fur Naturforschung, vol. 64, no. 9, pp. 1027–1031, 2009. View at Google Scholar
  18. F. Marandi, S. Chantrapromma, and H.-K. Fun, “Synthesis and spectroscopic studies of mixed-ligand complexes of lead(II) hexafluoroacetylacetonate including the crystal structure of [Pb2(phen)4(hfa)2(-NO3)2],” Journal of Coordination Chemistry, vol. 62, no. 2, pp. 249–256, 2009. View at Google Scholar
  19. H. Ahmadzadi, F. Marandi, and A. Morsali, “Structural and X-ray powder diffraction studies of nano-structured lead(II) coordination polymer with eta(2) Pb center dot center dot center dot C interactions,” Journal of Organometallic Chemistry, vol. 694, pp. 3565–3569, 2009. View at Google Scholar
  20. F. Marandi, M. Khosravi, and H.-K. Fun, “Spectroscopic, thermal and structural studies of Aza-aromatic base adducts of cadmium furoyltrifluoroacetonate,” Zeitschrift fur Anorganische und Allgemeine Chemie, vol. 634, pp. 2617–2622, 2008. View at Google Scholar
  21. F. Marandi and H.-K. Fun, “Supramolecular structure formed by directed intermolecular interactions in a lead(II) complex,” Zeitschrift fur Anorganische und Allgemeine Chemie, vol. 634, no. 6-7, pp. 1123–1126, 2008. View at Google Scholar
  22. F. Marandi, A. Aslani, and A. Morsali, “Fluorine-substituted beta-diketonate Pb-II complexes, [Pb(phen)(TFPB)2] and [Pb(2,2-bipy)(TFPB)2],” Journal of Coordination Chemistry, vol. 61, no. 6, pp. 882–890, 2008. View at Google Scholar
  23. F. Marandi, A. Morsali, and A. A. Soudi, “Labile interactions in aza-aromatic base adducts of lead(II) thenoyltrifluoroacetonate,” Zeitschrift fur Anorganische und Allgemeine Chemie, vol. 633, no. 4, pp. 661–665, 2007. View at Google Scholar
  24. F. Marandi, N. Asghari, M. Gorbanloo, A. A. Soudi, and P. Mayer, “Synthesis and crystal structure of [Pb(trz)(tfpb)(H2O)]: a lead(II) complex containing 2,4,6-tris(2-pyridyl)-1,3,5-triazine and 4,4,4- trifluoro-1-phenyl-1,3-butandionate,” Zeitschrift fur Anorganische und Allgemeine Chemie, vol. 633, no. 4, pp. 536–538, 2007. View at Google Scholar
  25. J. M. Harrowfield, F. Marandi, and A. A. Soudi, “Fluorous interactions in complexes of lead(II)hexafluoroacetylacetonate,” Inorganica Chimica Acta, vol. 358, pp. 4099–4103, 2005. View at Google Scholar
  26. Rigaku, CrystalClear, Version 1.3.6, Rigaku American Corporation, The Woodlands, Tex, USA, 2005.
  27. G. M. Sheldrick, SHELXS97 and SHELXL97, University of Gottingen, Berlin, Germany, 1997.
  28. F. Marandi, F. Amoopour, I. Pantenburg, and G. Meyer, “Synthesis and crystal structure of two new lead(II) coordination polymers with substituted 2,2′-bipyridine ligands with dicyanamide and nitrate as co-ligands,” Journal of Molecular Structure, vol. 973, no. 1– 3, pp. 124–129, 2010. View at Publisher · View at Google Scholar · View at Scopus
  29. A. Ramazani, S. Hamidi, and A. Morsali, “A novel mixed-ligands holodirected two-dimensional lead(II) coordination polymer as precursor for preparation lead(II) oxide nanoparticles,” Journal of Molecular Liquids, vol. 157, no. 1, pp. 73–77, 2010. View at Publisher · View at Google Scholar · View at Scopus
  30. A. R. Choudhury, U. K. Urs, T. N. Guru Row, and K. Nagarajan, “Weak interactions involving organic fluorine: a comparative study of the crystal packing in substituted isoquinolines,” Journal of Molecular Structure, vol. 605, no. 1, pp. 71–77, 2002. View at Publisher · View at Google Scholar · View at Scopus
  31. C. Janiak, “A critical account on ΠΠ stacking in metal complexes with aromatic nitrogen-containing ligands,” Journal of the Chemical Society, Dalton Transactions, pp. 3885–3896, 2000. View at Google Scholar
  32. Z.-H. Liu, C.-Y. Duan, J.-H. Li, Y.-J. Liu, Y.-H. Mei, and X.-Z. You, “Structural dependence of ΠΠ interactions in dithiocarbazato and thiosemicarbazato nickel complexes,” New Journal of Chemistry, vol. 24, pp. 1057–1062, 2000. View at Google Scholar
  33. G. R. Desiraju and T. Steiner, “The weak hydrogen bond,” in IUCr Monograph on Crystallography, vol. 9, Oxford Science, Oxford, UK, 1999. View at Google Scholar
  34. E. D'Oria and J. J. Novoa, “On the hydrogen bond nature of the C–HF interactions in molecular crystals. An exhaustive investigation combining a crystallographic database search and ab initio theoretical calculations,” CrystEngComm, vol. 10, pp. 423–436, 2008. View at Google Scholar
  35. S. Takahashi, T. Jukurogi, T. Katagiri, and K. Uneyama, “Isomorphic supramolecular structures via one-dimensional hydrogen bonding motifs in crystals of chiral difluorolactates, trichlorolactates and trifluorolactates,” CrystEngComm, vol. 8, no. 4, pp. 320–326, 2006. View at Publisher · View at Google Scholar · View at Scopus
  36. A. R. Choudhury and T. N. G. Row, “Organic fluorine as crystal engineering tool: evidences from packing features in fluorine substituted isoquinolines,” CrystEngComm, vol. 8, no. 265, pp. 274–2006.
  37. J. Ruiz, V. Rodríguez, C. Haro, A. Espinosa, J. Pérez, and C. Janiak, “New 7-azaindole palladium and platinum complexes: crystal structures and theoretical calculations. In vitro anticancer activity of the platinum compounds,” Dalton Transactions, vol. 39, pp. 3290–3301, 2010. View at Google Scholar