Trinitrato [N,N′,N″-tris(2,3-dimethoxybenzamido)triethylamine]-neodymium(III ). Synthesis, crystal structure and luminescence of a Nd complex containing tripodal amide ligands

Article abstract of DOI:10.1039/b006976k

A neodymium complex containing tripodal amide ligands has been synthesised and X-ray analysis has revealed the polymeric nature of the complex in the solid state.

Full text of DOI:10.1039/b006976k

View Article Online / Journal Homepage / Table of Contents for this issue
Trinitrato[N,Nº,N/-tris(2,3-dimethoxybenzamido)triethylamine]-
neodymium(III). Synthesis, crystal structure and luminescence of a
Nd complex containing tripodal amide ligands
Winnie Po-Wan Laia and Wing-Tak Wong*a,b
L e t t e r
a Department of Chemistry, T he University of Hong Kong, Pokfulam Road, Hong Kong,
P. R. China. E-mail: wtwong=hkucc.hku.hk; Fax ]852 2547 2933
b PKU-HKU Joint L aboratory on Rare Earth Materials and Bioinorganic Chemistry,
Peking University, Beijing, 100871, P. R. China
Received (in Montpellier, France) 28th August 2000, Accepted 4th October 2000
First published as an Advance Article on the web 15th No¿ember 2000
A neodymium complex containing tripodal amide ligands has
been synthesised and X-ray analysis has revealed the polymeric
nature of the complex in the solid state.
excited by means of an argon laser with the 512 nm line and
recorded on a double grating monochromator with a cooled
photomultiplier tube. Complex 1 shows structured emission
peaks at 880, 1060 and 1350 nm, which are assigned as
Lanthanide(III) cations have found wide application as poten-
tial luminescent biomedical diagnostic and therapeutic agents
(Eu, Tb),1 contrast agents for magnetic resonance imaging
(Gd),2 catalysts in RNA hydrolysis3 and in Ñuorescence
imaging.4 The application of lanthanide complexes depends
on both the metal ion and type of ligand. The luminescence
properties of Nd3` complexes have been intensively investi-
gated as they o†er opportunities to develop new materials
suitable for optical ampliÐers operating at 1.3 lm.5 This
window is important for telecommunications systems. It has
been shown that e†ective sensitization of the Nd3` emission
can be achieved by incorporation of organic ligands like deu-
terated hexaÑuoroacetylacetonate anion,6 Ñuorescein-bearing
calix[4]arene cages,7 and phenolic cryptand.8 In this context,
we were interested in using multidentate tripodal ligands con-
taining the amide functionality to complex with Nd3` and
investigate their luminescence behaviour.
4F ] 4I , 4I
and 4I
, respectively. The narrow
3@2
9@2
11@2 13@2
structure is rather similar to that observed for the lumines-
cence of Nd : YAG. Further investigations into this type of
polymeric lanthanide-based materials are in progress.
Experimental
Synthesis
Nd(NO ) É 6H O (47 mmol) and N,N@,NA-tris(2,3-dimethoxy-
3 3
2
benzamido)triethylamine (47 mmol) were dissolved in acetoni-
trile (25 ml). The mixture was allowed to reÑux for 2 days and
the product of 1 : 1 metal-to-ligand ratio as evidenced from
elemental analysis was obtained. (Yield 30%). Crystals were
obtained by slow evaporation of an acetonitrile solution.
Anal. 1: Found: C, 41.8; H, 4.8; N, 11.4. Calc for
C
H
N O Nd: C, 41.6; H, 4.5; N, 11.1%. IR (KBr, cm~1):
35 45
8
18
The reaction of hydrated neodymium nitrate with N,N@,NA-
tris(2,3-dimethoxybenzamido)triethylamine,9 L, in a 1 : 1, ratio
in acetonitrile a†orded complex 1 in satisfactory yield. Single
crystals of 1 suitable for X-ray analysis were obtained from
the slow evaporation of an acetonitrile solution at room tem-
perature for a few days. The coordination geometry of the
metal centre in 1 can be described as a tri-capped trigonal
prism and its perspective drawing, together with some selected
bond parameters, is shown in Fig. 1. This analysis also
revealed the polymeric nature of 1 in the solid state. Each
Nd3` is coordinated by three amide carbonyl groups from
three di†erent tripodal ligands and doubly coordinated to
three nitrate ions. This coordination leads to considerable
weakening of the CÈO bond strength (l , 1599 cm~1) as
CO
evident from the solid state (KBr disc) IR spectroscopic mea-
surement. The central amino N atom of the tripod ligand is
found to coincide with the crystallographic three-fold rotation
symmetry axis. This novel structural arrangement has never
before been observed for lanthanide complexes with tripodal
ligands. Normally, all three arms tend to wrap around a single
metal centre to give
a thermodynamically favourable
product.10 This salient observation may be attributed to the
acetonitrile solvent molecule that is situated on the three-fold
crystallographic axis in such a way as to interact with all three
NH groups of the tripodal ligand.
The photophysical properties of complex 1 have been
studied at low (10 K) and room (290 K) temperature; the photo-
luminescence spectrum is shown in Fig. 2. Nd3` ions were
Fig. 1 Perspective view of complex 1 in the solid state. Selected bond
lengths (A): NdÈO(1) 2.40(1), NdÉ É ÉNd* 10.991(1).
DOI: 10.1039/b006976k
New J. Chem., 2000, 24, 943È944
943
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2000

View Article Online
and a goodness-of-Ðt 1.24. The absolute conÐguration of the
structure has been determined by reÐning the Flack parameter
[0.007(1)].
CCDC reference number 440/228. See http://www.rsc.org/
suppdata/nj/b0/b006976k/ for crystallographic Ðles in .cif
format.
Acknowledgements
We gratefully acknowledge Ðnancial support from the Hong
Kong Research Grants Council and the University of Hong
Kong. W. P.-W. L. acknowledges the receipt of a postgraduate
studentship administered by the University of Hong Kong.
Notes and references
1
2
L. Thunus and R. Lejeune, Coord. Chem. Rev., 1999, 184, 125.
C. F. G. C. Geraldes, A. D. Sherry, E. Lazar, A. Miseta, P.
Boguer, E. Berenyi, B. Sumegi, G. E. Kiefer, K. McMillan, F.
Maton and R. N. Muller, Magn. Reson. Med., 1993, 30, 696; V.
Alexander, Chem. Rev., 1995, 95, 273; M. Botta, Eur. J. Inorg.
Chem., 2000, 399.
Fig. 2 Photoluminescence spectra of complex 1 at 10 K (È È È) and
290 K (ÈÈ) in the solid state.
3
4
5
T. Bruice, A. Tsubouchi, R. Dempey and L. Olson, J. Am. Chem.
Soc., 1996, 118, 9867.
I. Hemmila, Applications of Fluorescence in Immunoassays, Wiley,
New York, 1991.
R. J. Mears and S. R. Bater, Opt. Quantum Electron, 1992, 24,
517; A. Beeloy and S. Faulkner, Chem. Phys. L ett., 1997, 266,
116; M. H. V. Werbs, J. W. Hofsbraat, F. A. J. Geurts and J. W.
Verhoeven, Chem. Phys. L ett., 1997, 276, 196; M. P. O. Wolbers,
F. C. J. M. van Veggel, B. H. M. Snellink-Ruel, J. W. Hofsbraat,
F. A. J. Geurts and D. N. Reinhoudt, J. Chem. Soc., Perkin T rans.
2, 1998, 2141; S. Yangida, Y. Hasegawa, K. Murakoshi, Y. Wada,
N. Nakashima and T. Yamanaka, Coord. Chem. Rev., 1998, 171,
461; Y. Wada, T. Okubo, M. Ryo, T. Nalcazawa and S. Yana-
gida, J. Am. Chem. Soc., 2000, 122, 8583.
Y. Hasegawa, K. Murakoshi, Y. Wada, S. Yanagida, J.-H. Kim,
N. Nakashima and T. Yamanaka, Chem. Phys. L ett., 1996, 248, 8.
M. P. O. Wolbers, F. C. J. M. van Veggel, F. G. A. Peters, E. S. E.
van Beelen, J. W. Hofstraat, F. A. J. Geurts and D. N. Reinhoudt,
Chem. Eur. J., 1998, 4, 772.
3358, 1599, 1576, 1475, 1458, 1385, 1304, 1265, 1070, 995, 752.
FAB MS: m/z 907 [M [ NO ]`, 844 [M [ 2 NO ]`, 781
3
3
[M [ 3 NO ]`.
3
Crystallography
Single crystals of complex 1 suitable for X-ray crystallo-
graphic studies were mounted in glass capillaries. Di†raction
data were collected at room temperature on a Bruker AXS
SMART CCD di†ractometer equipped with graphite-
monochromated Mo-Ka radiation (j \ 0.710 73 A). Crystal
6
7
data for C
H
N O Nd, 1: M \ 1010.02, primitive tri-
8
C. Platas, F. Avecilla, A. de Blas, T. Rodriguez-Blas, C. F. G. C.
Geraldes, E. Toth, A. E. Merbach and J.-C. G. Bunzli, J. Chem.
Soc., Dalton T rans., 2000, 611.
S. J. Rodgers, C. W. Lee, C. Y. Ng and K. N. Raymond, Inorg.
Chem., 1987, 26, 1622.
35 45
8
18
gonal, a \ 10.993(1), c \ 21.554(2) A, U \ 2255.7(3) AŽ 3, T \
298 K, space group P3c1 (no. 158), Z \ 2, k(Mo-Ka) \ 12.29
9
cm~1, 6553 reÑections measured, 1965 unique (R \ 0.056),
int
1158 observed reÑections [I [ 1.5p(I)] were used in all calcu-
10 P. Caravan, T. Hedlund, S. Liu, S. Sjoberg and C. Orvig, J. Am.
Chem. Soc., 1995, 117, 11230; C. D. Sun and W. T. Wong, Inorg.
Chim. Acta, 1997, 255, 355; C. Y. Su, B. S. Kang, Q. C. Yang and
T. C. W. Mak, J. Chem. Soc., Dalton T rans., 2000, 1857.
lations. The structure was solved by direct methods (SIR92)
and expanded using Fourier techniques, it was reÐned by full-
matrix least-squares analysis on F to R \ 0.042, R \ 0.044
w
944
New J. Chem., 2000, 24, 943È944