Hydrothermal synthesis, crystal structure and fluorescence quenching of hexanuclear Ni5IILnIII complexes (Ln = La, Nd) containing macrocyclic oxamide ligands

Journal of Molecular Structure 842 (2007) 55–59 www.elsevier.com/locate/molstruc

Hydrothermal synthesis, crystal structure and fluorescence quenching III complexes (Ln = La, Nd) containing of hexanuclear NiII 5 Ln macrocyclic oxamide ligands Yaqiu Sun a, Guangming Yang b,*, Daizheng Liao b,*, Zonghui Jiang b, Shiping Yan b, Peng Cheng b a

Department of Chemistry, Tianjin Normal University, Tianjin 300074, PR China b Department of Chemistry, Nankai University, Tianjin 300071, PR China

Received 9 October 2006; received in revised form 8 December 2006; accepted 8 December 2006 Available online 21 December 2006

Abstract Two novel macrocyclic oxamidato-bridged complex [La(NiL)5] (ClO4)3ÆDMFÆ1Æ5H2O (1) and [Nd(NiL)5](ClO4)3ÆH2O (2) (NiL, H2L = 2,3-dioxo-5, 6, 14, 15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien), have been hydrothermally synthesized and structural˚ , b = 18.626(6) A ˚ , c = 18.726(6) A ˚, ly determined. Compound 1 crystallizes in the triclinic space group P1 with a = 17.534(6) A a = 97.115(6), b = 114.253(5), c = 108.449(5) and Z = 2; whereas 2 crystallizes in the monoclinic system, P2(1)/n group, ˚ , b = 24.073(7) A ˚ , c = 23.570(6) A ˚ , a = c = 90, b = 102.950(6) and Z = 4. The fluorescences of NdIII are almost coma = 17.805(5) A pletely quenched in 2.  2006 Elsevier B.V. All rights reserved. Keywords: Macrocyclic oxamide complex; Hydrothermal synthesis; Fluorescence quenching

1. Introduction Recently, an increasing interest has been given to the design mononuclear oxamidato-bridged complex ligand containing macrocyclic, because these precursors are particularly suitable for designing heterometallic complexes and played an important role in the development of molecular magnetism and macrocyclic compounds [1–10]. However, most of the studies were focused on the mononuclear oxamidato-bridged copper complex ligands, by comparison, the mononuclear oxamidato-bridged nickel complex ligand has been poorly investigated. Especially, those used to designing heterometallic complexes containing 3d–4f metals have been made rarely, although metal complexes of macrocyclic ligands have been of great interest to coor-

*

Corresponding authors. E-mail address: [email protected] (Y. Guangming).

0022-2860/$ - see front matter  2006 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2006.12.015

dination chemists for their special structure, properties, and/or functionalities [6–14]. On the other hand, many complexes containing rare earth ions have been prepared, and their fluorescent proprieties have been studied, but heterometallic complexes of this kind, especially, those containing 3d–4f metals have been investigated rarely [15–18]. Thus herein, we focus on the synthesis, structures of [La(NiL)5](ClO4)3ÆDMFÆ1.5H2O and [Nd(NiL)5](ClO4)3Æ H2O and the fluorescent properties of 2. 2. Experimental 2.1. Materials and methods All the starting reagents were of A.R. grade and were used as purchased. The complex ligand CuIIL was prepared as described else where [19]. Analyses of C, H and N were determined on a Perkin-Elmer 240 Elemental analyzer. IR

56

S. Yaqiu et al. / Journal of Molecular Structure 842 (2007) 55–59

spectrum was recorded as KBr discs on a Shimadzu IR-408 infrared spectrophotometer in the 4000–600 cm1 range. Electronic spectra in DMF were recorded on a Shimadzu UV-2101 PC scanning spectrophotometer. 2.2. Synthesis of [La(NiL)5](ClO4)3ÆDMFÆ 1.5H2O (1) The complex was prepared by a hydrothermal reaction. A mixture of CuIIL, La(ClO4)3Æ6H2O, DMF and H2O in the mole ratio 4.0:1.0:20:300 was sealed in an 18 cm3 Teflon-lined reactor which was kept at 160 C for 72 h. Deep brown green crystals were obtained (yield 92.4% based on La) Found: C, 47.26; H, 3.71; N, 11.78%. Calcd for C98H90Cl3N21O24.50 LaNi5: C, 47.22; H, 3.64; N, 11.80%. Main IR bands (KBr, cm1): 3415s (br), 1639vs, 1604vs, 1481m, 1342vs (br), 765.w. 622w. 2.3. Synthesis of [Nd(NiL)5](ClO4)3ÆH2O (2) The complex was prepared in the same way as 1, using Nd(ClO4)3Æ6H2O instead of La(ClO4)3Æ6H2O. Deep brown-red crystals were obtained (yield 89.01% based on Nd). Anal. found: C, 48.28; H, 3.51; N, 11.82%. Calcd. for C95H82Cl3N20O23NbNi5: C 48.25, H 3.50, N 11.85%. Main IR bands (KBr, cm1): 3417s (br), 1638vs, 1617vs, 1447 m, 1090vs (br), 777w, 623w. Caution! Perchlorate salts of metal complexes with organic ligand are potentially explosive and should be handled in small quantities with care. 2.4. X-ray crystallographic data The data were collected on a Bruker Smart-1000-CCD area detector, all using graphite-monochromated Mo Ka ˚ ) at 293(2) K. A total of 20927 radiation (k = 0.71073 A [1.21 6 h 6 25.00] independent reflections for 1 were collected, of which 16405 [R(int) = 0.0636] reflections were used and a total of 39680 [1.62 6 h 6 25.03] independent reflections for 2 were collected, of which 17039 [R(int) = 0.1334] reflections were used in the subsequent structure determination and refinement. The structure of two complexes were solved by direct method and subsequent Fourier difference techniques and refined using full-matrix least-squares procedure on F2 with anisotropic thermal parameters for all non-hydrogen atoms (SHELXS-97 and SHELXL-97) [20]. Hydrogen atoms were added geometrically and refined with riding model position parameters and fixed isotropic thermal parameters. Crystal data collection and refinement parameters are given in Table 1. The key distances and angles are reported in Table 2. 3. Results and discussion 3.1. Synthesis In this paper, we used complex ligand NiL to prepare heteropolynuclear complexes. The choice of the macrocyclic

Table 1 Summary of crystallographic data for complexes 1 and 2 Complexes

1

2

formula C98H90Cl3N21O24.50LaNi5 fw 2492.72 Crystal system Triclinic Space group P1 a 17.534(6) b 18.626(6) c 18.726(6) a() 97.115(6) b() 114.253(5) c() 108.449(5) ˚ 3) V(A 5057(3) Z 2 qcalcd(g/cm3) 1.637 l(Mo Ka) mm1 0.71073 Crystal size (mm) 0.30 · 0.24 · 0.20 T (K) 293(2) Goodness-of-fit 1.062 on F2 0.0665 R1a [I > 2r(I)] wR2b [I > 2r(I)] 0.1395 P P a R1 = iFojjFci/ jFoj. P P b wR2 ¼ f ½wðF 2o  F 2c Þ2 = ½wðF o Þ2 g1=2 .

C95H82Cl3N20O23NbNi5 2364.62 Monoclinic P2(1)/n 17.805(5) 24.073(7) 23.570(6) 90 102.950(6) 90 9845(5) 4 1.595 0.71073 0.30 · 0.25 · 0.20 293(2) 1.046 0.0916 0.2041

Table 2 ˚ ) and angles (deg) for 1–2 Selected bond distances (A Complex 1 La(1)-O(1) La(1)-O(2) La(1)-O(3) La(1)-O(4) O(6)-La(1)-O(9) O(6)-La(1)-O(3) O(9)-La(1)-O(3) O(6)-La(1)-O(8) O(9)-La(1)-O(8) O(3)-La(1)-O(8) O(6)-La(1)-O(1) O(9)-La(1)-O(1) O(3)-La(1)-O(1) O(8)-La(1)-O(1) O(6)-La(1)-O(4) O(9)-La(1)-O(4) O(3)-La(1)-O(4) O(8)-La(1)-O(4)

Complex 2 2.598(8) 2.693(8) 2.572(8) 2.605(8) 66.9(3) 143.4(3) 80.5(3) 137.3(3) 131.3(3) 77.1(3) 112.6(3) 66.7(3) 65.3(3) 64.6(3) 134.5(3) 133.9(3) 61.2(3) 66.5(3)

Nb(1)-O(1) Nb(1)-O(2) Nb(1)-O(5) Nb(1)-O(6) O(7)-Nb(1)-O(2) O(7)-Nb(1)-O(5) O(2)-Nb(1)-O(5) O(7)-Nb(1)-O(3) O(2)-Nb(1)-O(3) O(5)-Nb(1)-O(3) O(7)-Nb(1)-O(6) O(2)-Nb(1)-O(6) O(5)-Nb(1)-O(6) O(3)-Nb(1)-O(6) O(7)-Nb(1)-O(10) O(2)-Nb(1)-O(10) O(5)-Nb(1)-O(10) O(3)-Nb(1)-O(10)

2.564(8) 2.497(8) 2.501(8) 2.542(8) 134.4(3) 67.3(3) 134.7(3) 104.9(3) 119.3(3) 72.8(3) 98.8(3) 72.8(3) 63.7(3) 116.3(3) 79.7(3) 71.4(3) 146.9(3) 116.0(3)

oxamide as bridging ligand is directed by following considerations: as far as the synthesis and structure are concerned, the macrocyclic oxamide complexes as ligands presents a number of useful singularities: it is well known to bridge 4f metal atoms due to oxamide containing two oxygen bridge; the macrocyclic oxamide precursors are more stable than others oxamide groups; Furthermore, heterometallic complexes of the macrocyclic oxamide, especially for those containing 3d–4f metals, have been made rarely [6–14]. The complexes 1 and 2 were prepared by hydrothermal method in order to obtain good quality crystals. Because the hydrothermal technique not only provides a pathway

S. Yaqiu et al. / Journal of Molecular Structure 842 (2007) 55–59

to stable structures utilizing inorganic molecular units of a desired geometry or composition but also allows the introduction of a variety of inorganic cations to act as tem-

57

plates in directing the organization of the complexes. In these reactions the Ln(III) ions were used as templating reagents. Under appropriate condition larger single crystals were obtained in high yield. 3.2. Structures description

Fig. 1. Perspective view of the pentanuclear complex cation of 1.

Fig. 2. The view of the coordination geometry around the La(III) ion.

III The complexes NiII (Ln = La, Nd) have been char5 Ln acterized by single-crystal X-ray diffraction. In all cases, the hexanuclear [La(NiL)5]3+ are well defined, without disorder on the oxamide ligand. The final R1 of the complex 2 is slightly high due to the crystals quality, but the element analyses, IR, electronic spectra and the power X-ray diffractions demonstrated that the structure of [Nd(NiL)5]3+ is similar to that of [La(NiL)5]3+. The crystallographic structure of 1 indicated that the complex consists of hexanuclear [La(NiL)5]3+cations, monovalent anions ClO 4 , DMF and water. A perspective view of the hexanuclear cation is depicted in Fig. 1. The central lanthanum (III) ion and external nickel(II) ions are bridged by macrocyclic oxamide groups. The coordination environments of the five nickel(II) ions are all slightly distorted square-planar, with two deprotonated oxamide nitrogen atoms and two imino nitrogen atoms as ligand atoms. The deviations of the four donor atoms (N1, N2, N3 and N4) from their mean plane are +0.2618, ˚ , respectively, and Ni1 0.2561, +0.2609 and 0.2490 A ˚ is 0.0175 A out of the plane. The central lanthanum (III) ion resides in a distorted dicapped square antiprism surrounded by ten oxygen atoms of five oxamide groups (see Fig. 2). The O1 and O5 atoms are located on cap, while the square antiprism is composed of O2, O3, O4, O6, O7, O8, O9 and O10 atoms, with one basal plane constructed by O4, O6, O7 and O10 atoms and the other basal plane constructed by O2, O3, O8 and O9. As depicted in Fig. 3, there are p–p interactions between benzene rings of NiL of different cations in the cell, which are parallel to each other and the distance between carbon atoms is ˚ . In addition, there are others O– about 3.32–3.470A

Fig. 3. View of the self-assembly 1-D superamolecular architecture through p–p and hydrogen bond interactions hydrogen bond interactions.

58

S. Yaqiu et al. / Journal of Molecular Structure 842 (2007) 55–59

H  O interactions between DMF and free water and free perchlorate, respectively. The element analyses, IR, electronic spectra and the single X-ray diffractions demonstrated that the structure of [Nd(NiL)5]3+ is similar to that of [La(NiL)5]3+ (Fig. 4). The central neodymium (III) ion and external nickel(II) ions are bridged by macrocyclic oxamide groups. Each nickel ion is coordinated by four nitrogen atoms of the macrocyclic ligand, with the [NiN4] portion exhibiting near planarity. The central lanthanum (III) ion resides in a distorted dicapped square antiprism surrounded by ten oxygen atoms of five oxamide groups. As depicted in Fig. 5, the cations are alternately bridged by perchlorate to give infinite chains in which C–H  O interactions between

˚ , \C–H  O = 112, NiL and perchlorate (dC. . .O = 3.331A ˚ dC. . .O = 3.321A, \C–H  O = 162). 3.3. IR and electronic spectra The IR spectra of hexanuclear species 1 and 2, showing three strong bands around 1639, 1610 and 1448 cm1, attributed to the t(N-C-O) stretching bands, are characteristic of the bridging oxamide group [21]. The broad band of 1 and 2 around 1090 and 622, 623 cm1 is attributed to the ClO 4 [22]. The electronic absorption spectra of the three complexes 1 and 2 were measured in DMF solution. In these complexes, a broad strong band centered at 564 nm is observed and can be attributed to the d–d transitions of nickel atoms with four coordination. All complexes exhibit very intense bands below 450 nm, assignable to charge-transfer transitions in the [NiIIL] chromophores and/ or intraligand p– p* interaction [21]. The hypersensitive transition bands of the rare earth metal ions were not observed [23]. 3.4. Fluorescence properties

Fig. 4. Perspective view of the hexanuclear complex cation [(NiL)5Nd]3+.

III The fluorescence spectra of NiII complex were giv5 Nd en in Fig. 6. The fluorescence spectra of Nd(ClO4)3Æ6H2O, which included in Fig. 6, were also measured for comparison. Nd(ClO4)3Æ6H2O exhibits the fluorescent bands attributable to the 2G9/2 fi 4I9/2 transitions in the 470 nm region, 2 G9/2 fi 4I11/2 transitions in the 550 nm region and 2G9/ 4 2 fi I15/2 in the 660 nm region, respectively. These fluorescent bands disappear almost completely in the complex 2. In order to check the drastic decrease in intensities, the fluorescent spectra of the mixture of Nd(ClO4)3Æ6H2O and CuL were measured using the exciting wavelength of 278 nm under room temperature. The result shows that the fluorescent spectra of the mixture of Nd(ClO4)3Æ6H2O and CuL are similar to that of Nd(ClO4)3Æ6H2O, and the intensities decrease relatively less comparing with that of

Fig. 5. View of the self-assembly 1-D superamolecular architecture through C–H  O hydrogen bond interactions.

S. Yaqiu et al. / Journal of Molecular Structure 842 (2007) 55–59

a 10

b

em

ex

59

100

9 8

80

7 6

60

5 4

40

3 2

20

a

1

b

0

0

-1 200

300

400

500

600

700

450

500

550

600

650

700

nm

nm

Fig. 6. (a) Excitation and emission spectra of complex 2; (b) The fluorescence spectra of NdClO4)3Æ6H2O (a) and 2 (b).

Nd(ClO4)3Æ6H2O. Thus, the present study clearly demonstrates that fluorescence of Nd (III) is effectively quenched in the complex. According to the most probable quenching mechanism, we have presumed that the energy transfer occurs from the excited Nd(III) to the Ni(II) center through the oxamidic oxygen bridges [15–18]. The mechanistic studies on the fluorescence quenching of Nd (III) by neighboring others d-transition in complexes are in progress in our laboratories. 4. Conclusion The macrocyclic oxamido-nickel(II) complex was used as a ligand to synthesize new heteropolynuclear complexes. III The result is that two novel hexanuclear NiII complex5 Ln es (Ln = La, Nd) have been isolated and structurally characterized. The fluorescent properties are also characterized in complexes 2. 5. Supplementary materials Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Center as supplementary publication number CCDC 617753 for 1 and CCDC 617752 for 2. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK. Fax: +44 1233/336 033; e-mail: [email protected]. Acknowledgments This work was supported by the National Natural Science Foundation of China (No. 20471031, No. 20571045 and 20631030), Natural Science Key Foundation of Tianjin, the University Science Foundation of Tianjin (No. 20050611) and (52LX05).

References [1] R. Ruiz, J. Faus, F. Loret, M. Julve, Y. Journaux, Coord. Chem. Rev. 193–195 (1999) 1069. [2] H. Ojima, K. Nonoyama, Coord. Chem. Rev. 92 (1980) 85. [3] K. Nakatain, J.Y. Carriat, Y. Journaux, O. Kahn, F. Loret, J.P. Renard, Y. Pei, J. Sletten, M. Verdaguer, J. Am. Chem. Soc. 111 (1998) 5739. [4] F. Loret, M. Julve, R. Ruiz, Y. Journaux, K. Nakatain, O. Kahn, J. Sletten, Inorg. Chem. 32 (1993) 27. [5] J.C. Colin, T. Mallah, Y. Journaux, F. Loret, M. Julve, C. Bois, Inorg. Chem. 35 (1996) 4170. [6] J.K. Tang, Y.Z. Li, Q.L. Wang, E.Q. Gao, D.Z. Liao, Z.H. Jiang, Inorg. Chem. 41 (2002) 2188. [7] J.K. Tang, L.Y. Wang, L. Zhang, E.Q. Gao, D.Z. Liao, Z.H. Jiang, S.P. Yan, P. Cheng, J. Chem. Soc. Dalton Trans. 8 (2002) 1607. [8] E.Q. Gao, W.M. Bu, G.M. Yang, D.Z. Liao, Z.H. Jiang, S.P. Yan, G.L. Wang, J. Chem. Soc. Dalton Trans. 7 (2002) 1432. [9] E.Q. Gao, J.K. Tang, D.Z. Liao, Z.H. Jiang, S.P. Yan, G.L. Wang, Helv. Chim. Acta 84 (2001) 908. [10] J.K. Tang, Q.L. Wang, E.Q. Gao, J.T. Chen, D.Z. Liao, Z.H. Jiang, Helv. Chim. Acta 85 (2002) 175. [11] G.A. Melson, Coordination Chemistry of Macrocyclic Compounds, Plenum, New York, 1979. [12] A. Bencini, C. Benelli, A. Caneschi, A. Dei, D. Gatteschi, Inorg. Chem. 25 (1986) 572. [13] M. Andruh, I. Ramade, E. Codjovi, O. Guillou, O. Kahn, J.C. Trombe, J. Am. Chem. Soc. 115 (1993) 1822. [14] C. Benelli, A.J. Blake, P.E.Y. Milne, J.M. Rawson, R.E.P. Winpenny, Chem. Eur. J. 1 (1995) 614. [15] V.G. Berner, D.W. Darnall, E.R. Birnbaum, Biochem. Biophys. Res. Commun. 66 (1975) 763. [16] N. Higashiyama, G. Adachi, Chem. Lett. (1990) 2029. [17] M. Sakamoto, M. Hashimura, K. Marsuki, A. Matsumoto, H. Okawa, Chem. Lett. (1991) 1007. [18] M. Saksmoto, M. Hashimura, Y. Nakayama, A. Matsumoto, H. Okawa, Bull. Chem. Soc. Jpn. 65 (1992) 1162. [19] D.S.C. Black, H. Corrie, Inorg. Nucl. Chem. Lett. 12 (1976) 657. [20] G.M. Sheldrick, SHELXS-97 and SHELXL-97, Software for Crystal Structure, Analysis, Siemens Analytical X-ray Instruments. Inc.Madision, WI, 1997. [21] F. Lloret, Y. Journaux, M. Julve, Inorg. Chem. 29 (1990) 3967. [22] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, fifth ed., John Wiley, New York, 1997, Part B. [23] A.T. Baker, A.M. Hamer, S.E. Livingstore, Transition Met. Chem. 9 (1984) 423.