DOTP-manganese and -nickel complexes: From a tetrahedral network with 12-membered rings to an ionic phosphonate

Article abstract of DOI:10.1021/ic040076m

DOTP (1,4,7,10-tetrakis(methylenephosphonic acid)-1,4,7,10- tetraazacyclododecane) was reacted hydrothermally with MnCl₂· 2H₂O and Ni(NO₃)₂·6H₂O resulting in two structurally different compounds. Mn[C₃NH ₇(PO₃H_0.5)]₄ crystallizes in the tetragonal space group P4/ncc, with a = 12.349(2) A, b = 12.349(2) A, c = 14.066(4) A, V = 2144.9(8) A³, and Z = 4. Manganese atoms are tetrahedrally bonded by four phosphonate oxygen atoms from four equivalent ligands. All 12-membered macrocycles are connected in a zigzag manner by sharing manganese atoms and forming 22-membered cavities between each pair of two adjacent macrocycles. Ni[C₃NH ₆(PO₃H)]₄[Ni(H₂O)₆] crystallizes as an ion pair complex. Ni(1) is octahedrally coordinated to two pendent phosphonate oxygen atoms and four nitrogen atoms from the macrocyclic backbone. Ni(2) is surrounded by six coordinatedly bonded water molecules to form a hexaqua cation. The manganese complex shows ion exchange capability for Cs⁺.

Full text of DOI:10.1021/ic040076m

Inorg. Chem. 2004, 43, 7308−7314
DOTP−Manganese and −Nickel Complexes: from a Tetrahedral Network
with 12-Membered Rings to an Ionic Phosphonate
Deyuan Kong, Dmitri G. Medvedev, and Abraham Clearfield*
Department of Chemistry, Texas A&M UniVersity, College Station, Texas 77842-30012
Received June 7, 2004
DOTP (1,4,7,10-tetrakis(methylenephosphonic acid)-1,4,7,10-tetraazacyclododecane) was reacted hydrothermally
with MnCl2 2H2O and Ni(NO3)2 6H2O resulting in two structurally different compounds. Mn[C3NH7(PO3H0.5)]4 crystallizes
in the tetragonal space group P4/ncc, with a 12.349(2) Å, b 12.349(2) Å, c 14.066(4) Å, V 2144.9(8)
Å3, and Z
4. Manganese atoms are tetrahedrally bonded by four phosphonate oxygen atoms from four equivalent
‚
‚
)
)
)
)
)
ligands. All 12-membered macrocycles are connected in a “zigzag” manner by sharing manganese atoms and
forming 22-membered cavities between each pair of two adjacent macrocycles. Ni[C3NH6(PO3H)]4[Ni(H2O)6] crystallizes
as an ion pair complex. Ni(1) is octahedrally coordinated to two pendent phosphonate oxygen atoms and four
nitrogen atoms from the macrocyclic backbone. Ni(2) is surrounded by six coordinatedly bonded water molecules
to form a hexaqua cation. The manganese complex shows ion exchange capability for Cs+.
Introduction
metal complexes with H4PMIDA under different pH condi-
tions.4 A number of metal phosphonocarboxylates have been
reported; their structures normally feature either a 2D layer
or a 3D network with an open framework.5
The chemistry of the metal phosphonates has been a
research field of rapid expansion in recent years, mainly due
to their potential application in the areas of catalysis, ion
exchange, proton conductivity, intercalation chemistry,
photochemistry, and materials chemistry.1 Most of the metal
phosphonates have a layered structure in which the metal
centers are bridged by the phosphonate group, although a
variety of 1D chains and porous 3D networks have also been
reported. The main obstacle in metal phosphonate chemistry
is the fact that many metal phosphonates of tetravalent metals
normally form poorly crystalline compounds, making their
structural studies a rather difficult task. Phosphonic acids
with additional functional groups such as aza-crown ethers,
amines, and carboxylic groups have been found to be better
ligands since they can provide more coordination sites that
may not only increase the solubility of the metal phos-
phonates in water and improve the crystallinity of their metal
complexes, but also form many complexes with novel
structures.2-4 The reaction of metal(II) salts with an aza-
crown ether resulted in a number of “macrocyclic leaflets”
with a 1D chain structures as well as other structural
moieties.2 Several types of structures have been reported for
DOTP, 1,4,7,10-tetrakis(methylenephosphonic acid)-1,4,7,-
10-tetraazacyclododecane, has proved to be a particularly
favorable NMR shift reagent for the 23Na+ NMR spectro-
scopic study of isolated cells, perfused tissues, and intact
animals.6 (See Scheme 1 for the ligand structure information.)
It is also useful as an extracellular in vivo marker of tissues.7
The relaxation properties of the Gd3+ complex, a potential
MRI contrast agent, have also been reported.8 The structures
of the Ln3+ complexes of this ligand in solution have been
thoroughly investigated using multinuclear NMR spectro-
(2) (a) Sharma, C. V. K.; Clearfield, A. J. Am. Chem. Soc. 2000, 122,
1558. (b) Clearfield, A.; Sharma, C. V. K.; Zhang, B. Chem. Mater.
2001, 13, 3099. (c) Mao, J. G.; Wang, Z.; Clearfield, A. Inorg. Chem.
2002, 41, 3713. (d) Clearfield, A. Curr. Opin. Solid State Mater. Sci.
2002, 6, 495.
(3) (a) Sharma, C. V. K.; Clearfield, A.; Cabeza, A.; Aranda, M. A. G.;
Bruque, S. J. Am. Chem. Soc. 2001, 123, 2885. (b) Mao, J. G.; Wang,
Z.; Clearfield, A. Inorg. Chem. 2002, 41, 2334. (c) Mao, J. G.; Wang,
Z.; Clearfield, A. New. J. Chem. 2002, 26, 1010.
(4) (a) Poojary, D. M.; Zhang, B.; Clearfield, A. Angew. Chem., Int. Ed.
Engl. 1994, 33, 2324. (b) Zhang, B.; Poojary, D. M.; Clearfield, A.
Inorg. Chem. 1998, 37, 249. (c) Mao, J. G.; Clearfield, A. Inorg. Chem.
2002, 41, 2319. (d) Gutschke, S. O. H.; Price, D. J.; Powell, A. K.;
Wood, P. T. Angew. Chem., Int. Ed. 1999, 38, 1088.
(5) (a) Stock, N.; Stucky, G. D.; Cheetham, A. K. Chem. Commun. 2000,
2277. (b) Zhu, J.; Bu, X.; Feng, P.; Stucky, G. D. J. Am. Chem. Soc.
2000, 122, 11563 and references therein. (c) Zhang, B.; Clearfield,
A. J. Am. Chem. Soc. 1997, 119, 2751.
* To whom correspondence should be addressed. E-mail: clearfield@
mail.chem.tamu.edu.
(1) Clearfield, A. Metal Phosphonate Chemistry. In Progress in Inorganic
Chemistry; Karlin, K. D.; Ed.; John Wiley & Sons: New York, 1998;
Vol. 47, pp 371-510 and references therein.
7308 Inorganic Chemistry, Vol. 43, No. 23, 2004
10.1021/ic040076m CCC: $27.50
© 2004 American Chemical Society
Published on Web 10/20/2004

DOTP-Manganese and -Nickel Complexes
Scheme 1. Synthetic Route for Compounds 1 and 2
crystal structures of metal complexes have recently become
of general interest in this area. To develop new inorganic-
organic hybrid ion exchangers with immobilized crown ethers
having novel properties, DOTP was hydrothermally treated
with Mn2+ and Ni2+ ions. Two different types of structures
were obtained: the Mn compound formed a 2D infinite sheet
and the Ni crystallized as ion pair single molecules.
Preliminary experiments showed that the Mn compound has
the ability to ion exchange Cs+.
Experimental Methods
The chemicals were purchased from commercial sources and used
as received.
The IR spectra were recorded in KBr pellets on a Nicolet Nexus
470 FTIR spectrometer with spectral resolution of 2.00 cm-1
.
Thermogravimetric studies were carried out with a TA instruments
TGA Q-500 unit at a heating rate 10 °C/min under argon. SEM
images were acquired at the Texas A&M University Microscopy
and Imaging Center. The elemental analysis data were obtained
from Robertson Microlit Laboratories, Madison, NJ. The DOTP
ligand was synthesized and purified using procedures reported
previously.15 Magnetic susceptibility and magnetization measure-
ments were carried out on a Quantum Design SQUID magnetometer
MPMS-XL. Direct current magnetic measurements were performed
with an applied field of 1000 G in the 2-300 K temperature range.
Data were corrected for diamagnetic contributions calculated from
the Pascal constants.
Synthesis of 1 and 2. Complex 1 was synthesized by a
hydrothermal reaction. A total of 0.2 mmol of 1,4,7,10-tetrakis-
(methylenephosphonic acid)-1,4,7,10-tetraazacyclododecane and 0.2
mmol of manganese chloride bishydrate (Aldrich) with 10.0 mL
of deionized water was sealed into a Teflon pressure vessel, and
heated at 150 °C for 24 h. Colorless needlelike crystals were
recovered for 1 in ca. 77.6% (0.093 g) yield. Elemental analysis
for 1, C12H32N4O12P4Mn: C, 23.81%; H, 4.64%; N, 9.07%. Calcd:
C, 23.89%; H, 5.35%; N, 9.29%.
A similar synthesis was carried out for 2, except that the ligand
solution was neutralized with Et3N and the pH adjusted to 6 before
adding the nickel salt. The final product was obtained as green
crystals ca. 48.7% (0.075 g) yield. C12H40N4O18P4Ni2: C, 19.51%;
H, 4.99%; N, 7.03%. Calcd: C, 18.72%; H, 5.24%; N, 7.28%.
Crystallography. X-ray Structural Analyses. Data (3.3° < θ
< 23.26°, 2.18° < θ < 28.31°) were collected at 110 K on a Bruker
Smart CCD-1000 platform diffractometer equipped with mono-
chromated (Mo KR, λ ) 0.71073 Å) and OXFORD cool stream
low-temperature control unit. Data collection and reduction were
performed with a Bruker CCD Smart 5.4 and SAINT +6.0 from
Bruker AXS.16 Crystallographic computation was carried out using
the SHELXTL 5.10 package.17 The cell constants were indexed
from reflections obtained from 60 frames with an exposure of 10
s/frame. A hemisphere of data (1271 frames at 5 cm detector
distances) was collected by the narrow-frame method with frame
widths of 0.03° in ω and exposure time of 40 s/frame. The first 50
frames were recorded at the end of data collection to assess the
stability of the crystals, and the decay in intensity was found to be
scopic techniques9 and utilizing the structural information
derived from the paramagnetic effects of these ions.10
However, only a preliminary X-ray crystal structure of the
[(NH4)5Tm(DOTP)] complex has been reported.11 Also, two
recent single crystal structures of [{Na13(OH)3(H2O)29}{Gd-
(DOTP)}][Gd(DOTP)]‚7H2O‚2CH3CH2OH12 and [Bi(H4-
DOTP)(Na(H2O)4)] together with one powder structure of
[Bi(H4DOTP)(H5O2)] were reported.13 Transition metal phos-
phonates with this ligand are relatively rare. Most literature
focuses on synthesis, thermodynamic stability, dissociation
kinetics, metal selectivity, and coordination behavior.14 The
(6) (a) Sherry, A. D.; Malloy, C. R.; Geraldes, F. G. C. C.; Cacheris, C.
F. G. J. Magn. Reson. 1988, 76, 528. (b) Buster, D. C.; Castro, M. M.
C. A.; Geraldes, F. G. C. C.; Malloy, C. R.; Sherry, A. D. Magn.
Reson. Med. 1990, 15, 25. (c) Malloy, C. R.; Buster, D. C.; Castro,
M. M. C. A.; Geraldes, F. G. C. C.; Geraldes, F. G. C. C.; Sherry, A.
D. Magn. Reson. Med. 1990, 15, 33. (d) Butwell, N. B.; Ramasamy,
R.; Sherry, A. D. InVest. Radiol. 1991, 26, 1079. (e) Butwell, N. B.;
Ramasamy, R.; Lazar, I.; Malloy, C. R.; Sherry, A. D. Am. J. Physiol.
1993, 264, H1884. (f) Pike, M. M.; Luo, C. S.; Clark, M. D.; Kirk, K.
A.; Kitakaze, M.; Madden, M. C.; Cragoe, E. J., Jr.; Pohost, G. M.
Am. J. Physiol. 1993, 265, H2017. (g) Bansal, N.; Germann, M. J.;
Lazar, I.; Sherry, A. D. J. Magn. Reson. Imaging 1992, 2, 385. (h)
Bansal, N.; Germann, M. J.; Seshan, V.; Shires, G. T., III; Malloy, C.
R.; Sherry, A. D. Biochemistry 1993, 32, 5638. (i) Xia, Z. F.; Horton,
J. W.; Zhao, P. Y.; Bansal, B.; Babcock, E. E.; Sherry, A. D.; Malloy,
C. R. J. Appl. Physiol. 1994, 76, 1507. (l) Seshan, V.; Germann, M.
J.; Preising, P.; Malloy, C. R.; Sherry, A. D.; Bansal, B. Magn. Reson.
Med. 1995, 34, 25.
(7) (a) Makos, J. D.; Malloy, C. R.; Sherry, A. D. J. Appl. Physiol. 1998,
85, 1800. (b) Geraldes, C. F. G. C.; Brown, R. D., III; Cacheris, W.
P.; Koenig, S.; Sherry, A. D. Magn. Reson. Med. 1989, 9, 94.
(8) Aime, S.; Botta, M.; Terreno, E.; Anelli, P. L.; Uggeri, F. Magn. Reson.
Med. 1993, 30, 583.
(9) (a) Aime, S.; Botta, M.; Terreno, P. D.; Williams, J. A. G. J. Chem.
Soc., Dalton Trans. 1996, 17. (b) Geraldes, C. F. G. C.; Sherry, A.
D.; Kiefer, G. E. J. Magn. Reson. 1992, 97, 290. (c) Ren, J.; Sherry,
A. D. J. Magn. Reson. 1996, B111, 178. (d) Aime, S.; Botta, M.;
Garino, E.; Crich, S. G.; Giovenzana, G. B.; Pagliarin, R.; Palmisano,
G.; Sisti, M. Chem. Eur. J. 2000, 6, 2609. (e) Sherry, A. D.; Geraldes,
C. F. G. C.; Cacheris, W. P. Inorg. Chim. Acta 1987, 139, 137.
(10) (a) Peters, J. A.; Huskens, J.; Raber, D. Prog. Nucl. Magn. Reson.
Spectrosc. 1996, 28, 283. (b) Peters, J. A.; Zitha-Bovens, E.; Corsi,
D. M.; Geraldes, F. G. C. C. In The Chemistry of Contrast Agents in
Medical Magnetic Resonance Imaging; Merbach, A. E., To´th, EÄ ., Eds.;
John Wiley & Sons: Chichester, 2001; Chapter 8.
(11) Paulus, E. F.; Juretschke, P.; Lang, J. 3. Jahrestag Der Deutschen
Gesellschaft fu¨r Kristallographie, Darmstadt, 1995.
(12) Avecill, F.; Peters, J. A.; Geraldes, F. G. C. C. Eur. J. Inorg. Chem.
2003, 4179.
(13) Hassfjell, S.; Kongshaug, K. O.; Rømming, C. J. Chem. Soc., Dalton
Trans. 2003, 1433.
(15) Lazar, I.; Hrncir, D.; Kim, W. D.; Kiefer, G. E.; Sherry, A. D. Inorg.
Chem. 1992, 31, 4422.
(16) SMART Version 5.0 and SAINT+ Version 6.01 area detector instrument
control, data acquisition, and detector data integration software;
Bruker AXS, Inc.: Madison, WI, 2000.
(17) Sheldrick, G. M. SHELXTL (SADABS, XS, XL) Crystallographic
software Package, Version 6.10; Bruker, AXS, Inc., Madison, WI,
2000.
(14) Lukes, I.; Kotek, J.; Vojtisek, P.; Hermann, P. Coord. Chem. ReV.
2001, 216-217, 287.
Inorganic Chemistry, Vol. 43, No. 23, 2004 7309

Kong et al.
Table 1. Crystal Data and Structure Refinement for Compounds 1 and
2
Table 2. Selected Bond Lengths (Å) and Angles (deg) for Compounds
1 and 2
molecular formula
Mn[C3NH7(PO3H0.5)]4
Ni[C3NH6(PO3H)]4-
[Ni(H2O)6]
769.78
green, block
0.17 × 0.12 × 0.11
monoclinic
21.5524(14)
6.7015(5)
18.6491(12)
90
Complex 1 Bond Lengths
Mn(1)-O(3)
P(1)-O(3)
P(1)-O(1)
2.020(3) 4×
P(1)-O(2)
P(1)-C(3)
1.517(3)
1.820(4)
fw
601.24
1.496(3)
cryst color, habit
dimensions, mm3
cryst syst
a, Å
b, Å
c, Å
colorless, needle
0.32 × 0.14 × 0.03
tetragonal
12.349(2)
12.349(2)
14.066(4)
90
90
90
2144.9(8)
P4/ncc
4
1.538(3)
Complex 1 Bond Anglesa
O(3)#1-Mn(1)-O(3)#2 122.12(15) O(3)-Mn(1)-O(3)#3 122.12(15)
O(3)#1-Mn(1)-O(3) 97.82(18) O(3)#1-Mn(1)-O(3)#3 109.40(18)
O(3)#2-Mn(1)-O(3) 109.40(18) O(3)#2-Mn(1)-O(3)#3 97.82(18)
R, deg
â, deg
90.3660(10)
90
2693.5(3)
C2/c
Complex 2 Bond Lengths
γ, deg
Ni(1)-O(1)
Ni(1)-N(1) 2×
Ni(1)-N(2) 2×
P(1)-O(1)
2.0684(2) 2x
2.1844(2)
2.1527(2)
1.5060(2)
1.5784(2)
Ni(2)-O(7)
Ni(2)-O(8) 2×
Ni(2)-O(9) 2×
P(1)-O(2)
2.0580(2) 2x
2.0611(2)
2.0517(2)
1.5063(2)
1.815(2)
V, Å3
space group
Z
4
F(calcd), c/g cm-3
F(000)
1.868
1252
1.898
1600
P(1)-O(3)
P(1)-C(1)
θ range, deg
coeff, µ, mm-1
T, K
3.30-23.26
2.18-28.31
Complex 2 Bond Anglesb
0.986
1.724
O(1)#1-Ni(1)-O(1)
85.59(9) O(9)#2-Ni(2)-O(9)
180.10(1)
88.40(7)
91.60(7)
180.00(9)
90.72(7)
96.38(7)
83.62(7)
180.00(1)
83.43(7)
110(2)
0.71073
8412 (Rint ) 0.0211)
776/0/82
full-matrix least
squares on F2
R1 ) 0.0433
wR2 ) 0.1257
R1 ) 0.0437
wR2 ) 0.1262
1.143
110(2)
0.71073
O(1)#1-Ni(1)-N(2) 101.28(7) O(9)#2-Ni(2)-O(7)
λ, Å
O(1)-Ni(1)-N(2)
96.17(7) O(9)-Ni(2)-O(7)
no. reflns measured
data/restrains/params
refinement method
8135 (Rint ) 0.018)
3109/0/185
full-matrix least
squares on F2
R1 ) 0.0371
wR2 ) 0.0934
R1 ) 0.0397
wR2 ) 0.0957
1.115
N(1)-Ni(1)-N(1)#1 107.60(1) O(7)#2-Ni(2)-O(7)
N(2)-Ni(1)-N(2)#1 156.16(1) O(9)#2-Ni(2)-O(8)#2
O(1)#1-Ni(1)-N(1) 168.53(7) O(7)-Ni(2)-O(8)#2
O(1)-Ni(1)-N(1)
N(2)-Ni(1)-N(1)
N(2)#1-Ni(1)-N(1)
83.50(7) O(7)#2-Ni(2)-O(8)#2
83.43(7) O(8)#2-Ni(2)-O(8)
82.56(7) N(2)#1-Ni(1)-N(1)#1
final R indices
(I > 2.0σ(I))
R indices (all data)
a Symmetry transformations used to generate equivalent atoms: #1, -1/2
GOF on F2
- x, 1/2 - y, z; #2, y - 1/2, x + 1/2, 1/2 - z; #3, -y, -x, 1/2 - z. b Symmetry
1
2.243; -0.460
1.313; -0.576
transformations used to generate equivalent atoms: #1, 1 - x, y, /2 - z;
1
3
#2, /2 - x, /2 - y, -z.
less than 1%. The structures were solved using direct methods
(SHELXTL) and refined with full-matrix least-squares with atomic
coordinates and anisotropic thermal parameters for all non-hydrogen
atoms giving a final R1 value of 0.0443 for 82 parameters and 776
unique reflections with (I > 2σ (I)) and wR2 of 0.1267 for all 8412
reflections for 1 and a final R1 value of 0.0371 for 185 parameters
and 3109 unique reflections with (I > 2σ (I)) and wR2 of 0.0957
for all 8135 reflections for 2. An absorption correction was
performed with SADABS. All hydrogen atoms were generated
geometrically, assigned fixed isotropic thermal parameters, and
included in the structure factor calculation. Refinement of complex
2 was satisfactory, and all atoms were ordered. However, there was
a residual peak of 2.24 e Å-3 (2.68 Å from O1) for complex 1 in
the final difference Fourier map, which was located in the suitable
hydrogen bonding distance within this peak and O1. When this
peak was assigned as a disordered water molecule, it can be
stabilized with the refinement of occupancy (50%). However, no
water molecule was observed from TGA analysis clearly. We
believe it was trace water which was trapped during the low-
temperature data collection process. Also, this residue is located
Figure 1. SEM image of compound 1.
1
in the special position (1/4, /4, 0.06). Some of the data collection
four different 1,4,7,10-tetrakis(methylenephosphonic acid)-
1,4,7,10-tetraazacyclododecane ligands which are connected
together to form a manganese infinite network along the ab
plane as shown in Figure 2a. The bond distance between
Mn and oxygen atoms is 2.020(3) Å. A Mn atom is located
in the special position of 3/4, 1/4, 1/4 which is shared by four
different equivalent DOTP ligands. There are 22-membered
rings positioned along the c-axis which are composed of
2Mn, 4N, 4P, 4O, and 8C atoms to form a porous material.
The channels can be observed in the cell packing diagram
in Figure 2b. The complexes are perfectly ordered with a
4-fold axis of symmetry. The P-O bond lengths 1.496(3),
1.517(3), and 1.538(3) Å, respectively, are all short. The
and refinement parameters are summarized in Table 1. Important
bond distances and angles for the two complexes are listed in Table
2.
Results and Discussion
Crystal Structure of Mn[C3NH7(PO3H0.5)]4, 1. 1,4,7,-
10-Tetrakis(methylenephosphonic acid)-1,4,7,10-tetraazacy-
clododecane, DOTP, was reacted with MnCl2‚2H2O hydro-
thermally at 150 °C in 1:1 molar ratio and yielded needlelike
crystalline products which are clearly depicted in an SEM
(scanning electron microscopy) reported as Figure 1. The
single crystal diffraction result shows the manganese atom
is tetrahedrally coordinated with four oxygen atoms from
7310 Inorganic Chemistry, Vol. 43, No. 23, 2004

DOTP-Manganese and -Nickel Complexes
Figure 2. (a) Polyhedral diagram of compound 1 viewed down the c-axis (purple tetrahedron CPO3 and cyan tetrahedron MnO4). (b) Unit cell packing
diagram of compound 1 in the ab-plane viewed down the c-axis.
shortest bond distance, P(1)-O(3), is involved in the
coordination of the manganese atom, which is assumed to
be an unprotonated PdO double bond or with a delocalized
minus charge P-˙ -˙ -˙O bond. It seems that the proton H(1C)
which is located on O(1) is disordered between O(1) and
O(2)#4 (symmetry code: y, 1/2 - x, z), because a very strong
hydrogen bond 2.498(4) Å is formed between those two
oxygen atoms with an ideal angle (160.5°). Also, for a
hydrogen bonded to oxygen of a phosphonate group, the ideal
P-OH bond is in the range 1.56-1.58 Å (see for example
compound 2). This bond length is slightly shorter in
compound 1 at 1.538(3) Å again indicative of a disordered
proton. The 12-membered macrocyclic cavity is empty with
two protons pointed toward the cavity which forms a
hydrophilic pocket. Scheme 1 also gives the schematic
structure of compound 1. The dotted lines circle the
disordered hydrogen atoms. The 12-membered rings are
connected by MnO4 tetrahedra in an up and down notchlike
fashion forming crenulated chains along the ac-plane as
shown in Figure 3. The distance between two crown rings
is 12 Å. On the basis of the bond valence calculation
bv ) exp(1.76 - 2.02)/0.37 ) 0.495
(bv represents bond valence) (1)
∑bv ) 1.98, which indicated that the central manganese atom
should be doubly charged.18 The magnetic measurement
confirmed that the compound is paramagnetic which is
characteristic for compound 1. The Mn(II) ions are isolated
paramagnets. The data were fit to the Curie law, with C )
4.65 emu‚K‚mol-1, in good agreement with the expected
(18) Brown, I. D.; Altermatt, D. Acta Crystallogr. 1985, B41, 244.
Inorganic Chemistry, Vol. 43, No. 23, 2004 7311

Kong et al.
Figure 3. Polyhedral diagram of a single crystal of compound 1 viewed down the b-axis (purple tetrahedron CPO3 and cyan tetrahedron MnO4).
Figure 4. Polyhedral representation of the crystal structure of compound 2 along the b-axis (purple tetrahedron CPO3 and cyan octahedron NiN4O2 and
Ni(H2O)6).
5
value for isolated high spin Mn(II) ions (S ) /2 and g )
2.06) in a magnetically dilute sample. From the above
information, the double positive charge was assigned to the
central Mn. (See Supporting Information.)
N(1A), O(1), and O(1A) atoms are coplanar with a deviation
0.0585 Å, and the nickel atoms fit perfectly inside the
equatorial plane. Two apical positions are filled with the other
nitrogen atoms, N(2) and N(2A) of the aza-ring. A similar
coordination environment was found for cis-O,O-[Ni(H2L)]-
Cl‚H2O, cis-O,O-[Ni(H2L)]‚2H2O (L ) 1,4,8,11-tetraaza-
cyclotetradecane-1,8-bis(methylphosphonic acid)).19 Bond
distances of P(1)-O(3) and P(2)-O(6) are 1.578(2) and
1.5705(2) Å, respectively, and are significantly longer than
the coordinated P(1)-O(1) bonds and uncoordinated P(1)-
O(2) (1.506(2) Å), P(2)-O(5) (1.5057(2) Å), P(2)-O(4)
(1.5112(2) Å) bonds. Therefore, they have been designated
as P-OH groups. As a result, each of the four phosphonate
groups bonded to the aza-ring nitrogen has a single negative
charge accounting for the anion double negative charge. The
Crystal Structure of Ni[C3NH6(PO3H)]4[Ni(H2O)6], 2.
The chemical formula of compound 2 in the crystal form,
as obtained from the X-ray diffraction crystal structural
analysis, is Ni[C3NH6(PO3H)]4[Ni(H2O)6]. The overall struc-
ture of the crystal is shown in Figure 4, where the asymmetric
unit contains two different nickel centered moieties. Figure
5 shows the SEM image of the single crystal morphology
for compound 2. Compound 2 crystallized as an ion pair.
The anion part is composed of [Ni(1)(H4DOTP)]2- with
octahedrally coordinated nickel. The ligand was deprotonated
at the synthetic pH conditions (pH 6). Two methylene
phosphonic acid pendent groups bend over and coordinate
with the center nickel atoms in cis conformation. The N(1),
(19) Kotek, J.; Vojtisek, P.; Cisarova, I.; Hermann, P.; Lukes, I. Collect.
Czech. Chem. Commun. 2001, 66, 363
7312 Inorganic Chemistry, Vol. 43, No. 23, 2004

DOTP-Manganese and -Nickel Complexes
Figure 6. TGA curves for compounds 1 and 2.
The adsorption of cesium occurred most likely only on the
surface of the crystalline material. It is difficult to tell whether
the Cs exchanged with the protons on the 12-membered ring
or with the P-OH groups attached to the ring. In this
experiment, crystals were used for ion exchange which may
reduce the capability of the material to exchange of Cs+
because of difficulty in diffusion into the lattice. More
confirmative experiments will be reported in the future.
Thermogravimetric Study. The thermogravimetric stud-
ies of compound 1 demonstrated a number of weight losses
indicating a complexity of the decomposition process (Figure
6). According to the structural data, no water molecules were
found in the compound. The TGA diagram shows that there
is no weight loss till 358 °C confirming that the residual
peak in the final Fourier map can be assigned to surface water
in the X-ray analysis data collection. The burning of the
organic part and phosphonic acid hydroxyl group condensa-
tion start at 358 °C and continue until 1000 °C.21 The total
weight loss of 51.4% corresponds to the final residue being
Mn2P2O7 (52.6%). The TGA curve of compound 2 has two
weight loss regions. Compound 2 starts losing the coordi-
nated water at 170 °C indicating a high temperature of
dehydration because of the strong bonding of water mol-
ecules to the metal atom. The observed weight loss at 275
°C (14.1%) is in agreement with the calculated value of
14.0% for all six coordinated water molecules. There are
two small regions of weight loss (9.7%) in the temperature
range 275-450 °C which could be assigned to a condensa-
tion of the hydroxyl groups in DOTP ligand with a theoretical
weight loss value of 9.35%. The burning of the organic ligand
and transformation of phosphonic moieties occur at 450-
900 °C. The process is complete with a total weight loss
value of 43.4%, in a good agreement with the calculated
final residue Ni3(PO4)2 + NiO (42.7%).22-24
Figure 5. SEM image of compound 2.
Ni cation octahedron [Ni(H2O)6]2+ is composed of six
coordinated water molecules with bond distances 2.052(2)-
2.061(2) Å. All water molecules act as hydrogen donors and
are hydrogen bonded with the phosphonate oxygen atoms.
The hydrogen bonding network as shown in Figure 4 is
viewed down the b-axis direction which runs through the
ac-plane and forms infinite chains. Each phosphonate group
connects to one proton, and two phosphonate moieties of
neighboring complex molecules form a pair of intermolecular
hydrogen bonds. The hydrogen bonds between the uncoor-
dinated phosphonate oxygen groups O(6)-H‚‚‚O(4)#
2.457(2) Å and the coordinated phosphonate oxygen groups
O(3)-H‚‚‚O(2)# 2.607(2) Å which result in an eight-
membered ring (P-O-H‚‚‚O-P)2 are shorter than those
formed by water molecules (2.656(2)-2.751(2) Å). The
complex molecules, connected through the hydrogen bonds,
form infinite chains very similar to those found in the
structure of cis-O,O-[Ni(H2L)]Cl‚H2O, cis-O,O-[Ni(H2L)]‚
2H2O, trans-O,O-[Co(HL)]‚3H2O, trans-O,O-[Co(HL)]‚
3H2O (L ) 1,4,8,11-tetraazacyclotetradecane-1,8-bis(meth-
ylphosphonic acid)),20 and Cu(H2L1) (L1
bisphosphonomethyl-1,10-diaza-18-crown-6).2c
) N,N′-
Ion Exchange. Compound 1 was tested for ion exchange
for the Cs+. The hydrophilic pocket with exchangeable
protons on the ring and P-OH groups as shown in the
structure may accommodate large ions such as Cs. A total
of 50 mg of the sample (crystals) was shaken with 8.55
mmol/L CsCl solution for 48 h. The initial pH of the solution
was 5.22 and changes to 3.76. The result of AA analysis
showed that compound 1 picked up 0.182 mmol/g Cs+ from
the solution. Protons were released to the solution after ion
exchange as evidenced by the pH measurements. About 11%
of the protons were exchanged by Cs+ ions. Single crystal
data on the exchanged crystal were collected after ion
exchange. The result showed that the cell had the same unit
cell parameters: a ) 12.3390(11) Å, b ) 12.3390(11) Å, c
) 14.0406(2) Å, V ) 2137.7(5) Å3, Z ) 4. No peaks
associated with Cs+ scattering were observed. The structure
was resolved, and no Cs was found in the resolved structure.
IR Study. IR spectra were recorded between 4000 and
400 cm-1 and are shown in Figure 7. The region between
4000 and 1400 cm-1 can be selected to study the coordinated
water and the P-O-H groups. Two bands observed at 2760
and 2340 cm-1 which are likely due to the ν(PO-H) and
2δ(POH), respectively, are characteristic of hydrogen phos-
phonate groups and more intense for compound 2 in
agreement with its stoichiometry. Compound 2 showed an
intense and broad band in the O-H stretching vibration
(21) Zhang, B.; Poojary, D. M.; Clearfield, A. Inorg. Chem. 1998, 37, 1844.
(22) Poojary, D. M.; Zhang, B.; Bellinghausen, P.; Clearfield, A. Inorg.
Chem. 1996, 35, 4942.
(23) Poojary, D. M.; Zhang, B.; Bellinghausen, P.; Clearfield, A. Inorg.
Chem. 1996, 35, 5254.
(24) Menaa, B.; Shannon, I. J. J. Mater. Chem. 2002, 12, 350.
(20) Kotek, J.; Lubal, P.; Hermann, P.; Cisarova, I.; Lukes, I.; Godula, T.;
Sovbodova, I.; Taborsky, P.; Havel, J. Chem. Eur. J. 2003, 9, 233.
Inorganic Chemistry, Vol. 43, No. 23, 2004 7313

Kong et al.
Conclusions
Two new different types of metal phosphonates have been
synthesized and characterized by X-ray diffraction, magnetic
measurements, IR spectroscopy, and TGA measurements.
Both structures have been solved from X-ray single crystal
data. It has been demonstrated that the tetrahedrally coor-
dinated Mn centers are shared by four oxygen atoms from
neighboring pendent phosphonic acid groups which are
associated with the 12-membered aza-ring. The nitrogen
atoms are not involved in the coordination at compound 1.
It forms a 2D array along the c-axis. The hydrophilic cavity
of the aza-crown is empty and accessible by other cations.
Preliminary ion exchange studies showed that compound 1
picked up Cs+ from the solution. Its powder form will further
be screened for exchange of other cations. Compound 2
contains two different octahedrally coordinated Ni centers
with hydrogen bonding extended to form 2D infinite chains
in the ac-plane, in which a six-water-coordinated nickel ion
is clathrated and acts as counterion to the negatively charged
[Ni(H4DOTP)]2- motif. Both compounds show the typical
paramagnetic properties. In the case of the manganese
compound, the pH was kept acidic (pH ∼ 2); as a result,
four protons of the initial eight on the phosphonate groups
are donated to the four aza nitrogens and two are displaced
by the Mn2+ ions. The two remaining protons are shared
equally by the four phosphonate groups in accordance with
the symmetry requirements. Because the aza groups are
protonated, the Mn2+ reacted with the phosphonate groups
rather than with the aza crown ring. In the case of the nickel
compound, the protons were essentially removed from the
aza nitrogens leaving just one proton on each of the four
phosphonic acid groups. Thus, two Ni2+ ions were required
to neutralize the ligand, one being coordinated by the ring
and phosphonate groups and the other forming a hexahydrate.
The compound is essentially ionic with an extensive system
of hydrogen bonding. These reactions should be general for
aminophosphonate ligands. We have prepared a series of aza
crown ethers with appended phosphonic acid groups in a
variety of ring sizes.27 By careful control of the proton
removal, families of new compounds with metals or amine
linkers should be achieved. Furthermore, compounds that
retain protons may be manipulated to exchange and coor-
dinate or selectively separate ions or neutral species.
Figure 7. IR spectra of compounds 1 and 2.
region at 3410-3250 cm-1, which is consistent with the
presence of coordinated water interacting by H-bonding. The
corresponding bending H-O-H (δHOH) vibration of the
coordinated water is located at ca. 1684 cm-1, which is also
broadened by hydrogen bonding. In fact, the band at 1680
cm-1 is close to the maximum 1690 cm-1 which is usually
assigned to the bending vibrations of species containing
highly mobile protons, and is typical of good protonic
conductors.25 A sharp band was observed at 3135 cm-1 for
compound 1 which is due to the stretching vibration of the
N-H group in the macrocyclic ligand and a bending
vibration band at 1635 cm-1 indicating the existence of
protonated NH+ and is in agreement with the X-ray structural
analysis. As we have pointed out, compound 1 is anhydrous,
so the band of 1635 cm-1 is not due to hydration water. Also,
two kinds of νas of PO3 were observed in compound 1 at
1097 and 1054 cm-1, respectively. The peak that occurs at
982 cm-1 was assigned to νs(PO3).26 The bands centered at
2330 and 1075 cm-1 are attributed to (PO-H) and (POH)
vibrations, respectively, due to unprotonated POH groups
in both compounds. Asymmetric vibrating stretching bands
of POH (ν(P-OH)) groups are situated at 980 cm-1. Both
compounds showed typical C-H stretching vibrations and
bending vibrations of low intensities of CH2 both inside the
ring and/or attached to nitrogen atoms, near 2850 and 1478
cm-1, respectively. The νP-C vibration bands of compound
1 are located at 1382 cm-1; otherwise, the similar bands for
compound 2 are split into two bands and are separately
situated at 1360 and 1316 cm-1, respectively, due to two
different kinds of phosphonic pendent groups involved. One
is coordinated with the nickel atom and the other is not.
Acknowledgment. The authors acknowledge with thanks
the financial support from the Department of Energy, Basic
Sciences Division, through Grant DE-FG03-00ER 15806.
Thanks to Dr. Naima Bestaoui for assistance in obtaining
SEM pictures and Drs. Yang Li and Andrey Prosvirin for
magnetic measurements.
Supporting Information Available: Crystallographic data,
including CIF files, and magnetic measurements. This material is
available free of charge via the Internet at http://pubs.acs.org.
(25) Martinez-Tapia, H. S.; Cabeza, A.; Bruque, S.; Pertierra, P.; Garcia-
Granda, S.; Aranda, M. A. G. J. Solid State Chem. 2000, 151, 122.
(26) (a) Barja, B. C.; Herszage, J.; Santos Alfons, M. Polyhedron 2001,
20, 1821. (b) Cabeza, A.; Aranda, M. A. G.; Bruque, S. J. Mater.
Chem. 1999, 9, 571. (c) Gomez-Alcantara, M. M.; Cabeza, A.; Aranda,
M. A. G.; Guagliardi, A.; Mao, J. G.; Clearfield, A. Solid State Sci.
2004, 6, 479.
IC040076M
(27) Kong, D. Y.; McBee, J.; Clearfield, A. Unpublished work.
7314 Inorganic Chemistry, Vol. 43, No. 23, 2004