W-dimensional copper(II) complexes with the trinucleating ligand 2,4,6-Tris(di-2-pyridylamine)-1,3,5-triazine: Synthesis, crystal structures, and magnetic properties

Article abstract of DOI:10.1021/ic900599g

The preparation and structural characterization of three new copper(II) complexes of formula [Cu₃(dipyatriz)₂(H₂0) ₃] (CIO₄)₆·2H₂O (1), {[Cu₄(dipyatrlz)₂(H<

Full text of DOI:10.1021/ic900599g

6630 Inorg. Chem. 2009, 48, 6630–6640
DOI: 10.1021/ic900599g
Low-Dimensional Copper(II) Complexes with the Trinucleating Ligand 2,4,
6-Tris(di-2-pyridylamine)-1,3,5-triazine: Synthesis, Crystal Structures, and
Magnetic Properties†
†
‡
§
§
‡
~
ꢀ
Consuelo Yuste, Laura Canadillas-Delgado, Ana Labrador, Fernando S. Delgado, Catalina Ruiz-Perez,
Francesc Lloret,† and Miguel Julve*,†
†
´
ꢁ
ꢁ
Departament de Quımica Inorganica/Instituto de Ciencia Molecular (ICMol), Universitat de Valencia,
‡
´
ꢁ
Polıgono La Coma s/n, E-46980 Paterna (Valencia), Spain, Laboratorio de Rayos X y Materiales
´
´
Moleculares, Departamento de Fısica Fundamental II, Facultad de Fısica, Universidad de La Laguna, Avenida
§
´
ꢀ
Astrofısico Francisco Sanchez s/n, E-38071 La Laguna (Tenerife), Spain, and BM16-LLS European
Synchrotron Radiation Facility, 6 Rue Jules Horowitz-BP 2208043 Grenoble CEDEX 9, France
Received March 28, 2009
The preparation and structural characterization of three new copper(II) complexes of formula [Cu3(dipyatriz)2(H2O)3]
(ClO4)6 2H2O (1), {[Cu4(dipyatriz)2(H2O)2(NO3)2(ox)2](NO3)2 2H2O}n (2), and [Cu6(dipyatriz)2(H2O)9(NO3)3(ox)3]
3
3
(NO3)3 4H2O (3) [dipyatriz = 2,4,6-tris(di-2-pyridylamine)-1,3,5-triazine and ox = oxalate] are reported. The structure
3
of 1 consists of trinuclear units [Cu3(dipyatriz)2(H2O)3]6+ and uncoordinated perchlorate anions. The two dipyatriz
molecules in 1 act as tris-bidentate ligands with the triazine cores being in a quasi eclipsed conformation. Each copper
atom in 1 exhibits a distorted square pyramidal geometry CuN4O with four pyridyl-nitrogen atoms from two dipyatriz
ligands building the basal plane and a water molecule occupying the axial position. The values of the intratrimer
˚
copper-copper separation are 8.0755(6) and 8.3598(8) A. Compound 2 exhibits a layered structure of copper(II) ions
which are connected through bis-bidentate dipyatriz ligands and bidentate/outer monodentate oxalato groups. The
copper atoms in 2 exhibit six- [Cu(1)N4O2] and five-coordination [Cu(2)N2O3]. A water molecule and three pyridyl-
nitrogen atoms [Cu(1)] and two pyridyl-nitrogen plus two oxalate-oxygen atoms [Cu(2)] define the equatorial plane
whereas either an oxalate-oxygen and a pyridyl-nitrogen [Cu(1)] or a nitrate-oxygen [Cu(2)] fill the axial positions. The
˚
copper-copper separation through the bridging oxalato is 5.6091(6) A whereas those across dipyatriz vary in the range
˚
7.801(1)-9.079(1) A. The structure of compound 3 contains discrete cage-like hexacopper(II) units [Cu6(dipyatriz)2-
(H2O)9(NO3)3(ox)3]3+ where two trinuclear [Cu3(dipyatriz)]6+ fragments are connected by three bis-bidentate oxalate
ligands, the charge beingbalanced by three non-coordinatednitrate anions. Thevaluesof theintracage copper-copper
˚
˚
distance are 5.112(3)-5.149(2) A (acrossoxalato) and 7.476(2)-8.098(2) A (through dipyatriz). Magneticsusceptibility
measurements of polycrystalline samples of 1-3 in the temperature range 1.9-295 K show the occurrence of a
weak antiferro∧magnetic interaction∧across dipyatriz in 1 [J = -0.08(1) cm-1, the Hamiltonian being defined as
∧
∧
∧
∧
∧
H = -J ( S1 S2 + S1 S3 + S2 S3)] and weak ferro- (2) and strong antiferromagnetic (3) interactions through the
3
3
3
oxalato bridge in 2 [J = +0.45(2) cm-1] and 3 [J = -390(1) cm-1]. The use of the dipyatriz-containing copper(II) species
as a building block to design homo- and heterometallic magnetic compounds is analyzed and discussed.
Introduction
temperatures above 150 ꢀC.3 The first studies with these
organic molecules focused on their use as analytical reagents
for different metalions,4 and further investigations illustrated
their capability as ligands for metal assembling because of the
1,3,5-Triazine-containing ligands such as 2,4,6-tris(2-pyr-
idyl)-1,3,5-triazine (tpyt) and 2,4,6-tris(2-pyrimidyl)-1,3,5-
triazine (tpymt) (see Scheme 1), whose synthesis was reported
half a century ago,1,2 are stable molecules which only undergo
hydrolysis in the presence of concentrated mineral acids and
(3) Smolin, E. M.; Rapoport, L. S-Triazines and Derivatives; Interscience:
New York, 1959; p 163.
(4) (a) Collins, P.; Diehl, H.; Smith, G. F. Anal. Chem. 1959, 31, 1862. (b)
Collins, P.; Diehl, H. Anal. Chim. Acta 1960, 22, 125. (c) Diehl, H.;
Buchanan, E. B.Jr.; Smith, G. F. Anal. Chem. 1960, 33, 1117. (d) Tsen, C.
C. Anal. Chem. 1961, 33, 849. (e) Embry, W. A.; Ayres, G. H. Anal. Chem.
1968, 40, 1499. (f) Janmohamed, M. J.; Ayres, G. H. Anal. Chem. 1972, 44,
2263.
*To whom correspondence should be addressed. E-mail: miguel.
julve@uv.es.
(1) Case, H. F.; Koft, E. J. Am. Chem. Soc. 1959, 81, 905.
(2) (a) Lerner, E. I.; Lippard, S. J. J. Am. Chem. Soc. 1976, 98, 5397.
(b) Lerner, E. I.; Lippard, S. J. Inorg. Chem. 1977, 16, 1537.
r
pubs.acs.org/IC
Published on Web 06/18/2009
2009 American Chemical Society

Article
Inorganic Chemistry, Vol. 48, No. 14, 2009 6631
tridentate terpyridine- and bidentate bipyridine-like binding
sites that they possess.2b,5-9
Scheme 1
Surprisingly, these 2,4,6-triaryl-substituted triazines
undergo a copper(II)-promoted hydrolysis in mild con-
ditions resulting in the highly stable [Cu(bpca)]+ (tpyt)
and [Cu(bpcam)]+ (tpymt) species [bpca = bis(2-pyri-
dylcarbonyl)amidate and bpcam = bis(2-pyrimidylcar-
bonyl)amidate],2a,10,11 This hydrolytic reaction that has
been proved to be also assisted by other cations such
as ruthenium(II) and rhodium(III)5b,5c,12 is the source
(5) (a) Barclay, G. A.; Vagg, R. S.; Watton, E. C. Acta Crystallogr. 1977,
B33, 3487. (b) Paul, P.; Tyagi, B.; Bhadbhade, M. M.; Suresh, E. J. Chem.
Soc., Dalton Trans. 1997, 2273. (c) Paul, P.; Tyagi, B.; Bilakhiya, A. K.;
Bhadbhade, M. M.; Suresh, E.; Ramachandraiah, G. Inorg. Chem. 1998, 37,
of the building blocks [M(bpca)x](m-x)+ and [M-
(bpcam)x](m-x)+ (M = di- or trivalent transition metal
ion and x = 1 or 2).2a,5b,10,11c,12,13 Their use as Lewis
acid and base respectively has provided a plethora of
homo-11a,11d,14 and heterometallic13f,15-17 polynuclear
species with interesting magnetic properties, two of the
most exciting results being the design of honeycomb
layered heterobimetallic materials16c,16d and an unpre-
cedented homometallic single chain magnet with regular
alternating low-spin iron(III)/high-spin iron(II) ions.14k,14l
At first sight, although tptz and tpymt offer the
possibility to bind three metal ions in a trigonal array,
there is no structural report to support this coordination
mode in the case of tptz, and it was only observed in two
structures with lead(II) for tpymt.9 This apparent diffi-
culty of tpyt and tpymt ligands to coordinate three metal
ions together with the metal-promoted hydrolysis that
they undergo limit their extensive use to develop supra-
molecular systems. In the search for more stable 1,3,5-
triazine based ligands which were able to form tridirec-
tional tricopper(II) complexes to be used as precursors
of multifunctional metallo-supramolecular structures,
we focused on the 2,4,6-tris(di-2-pyridylamine)-1,3,
5-triazine molecule (hereafter noted dipyatriz; see
Scheme 2). This polypyridyl ligand is prepared in a
one-pot synthesis by reacting 2,4,6-trichloro-1,3,5-tria-
zine with di-2-pyridylamine in toluene in basic medium,
and it has been shown that it is able to function as a blue
emitter in electroluminescent devices.18 Its X-ray struc-
ture shows the expected star-shape where the six
2-pyridyl rings are not coplanar with the central triazine
ring because of intramolecular steric interactions.18a The
availability of these three potentially bidentate dipyridy-
lamino moieties together with the supramolecular effects
caused by s-triazine ring (for instance, π-stacking,
~
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6632 Inorganic Chemistry, Vol. 48, No. 14, 2009
Yuste et al.
Scheme 2
Dipyatriz was prepared as previously reported.18 Slow evapora-
tion of solvent under ambient conditions, slow diffusion in an
H-shape tube, and hydrothermal methods23 were used to grow
X-ray quality crystals of 1, 2, and 3, respectively. Elemental
analysis (C, H, N) was conducted by the Microanalytical Service
ꢁ
of the Universitat de Valencia.
Caution! Perchlorate salts are potentially explosive, especially
in the presence of organic ligands. We worked at the mmol scale
and heating was avoided.
Synthesis of the Complexes. [Cu3(dipyatriz)2(H2O)3](ClO4)6
3
2H2O (1). This compound was obtained by reacting copper(II)
perchlorate hexahydrate (0.370 g, 1 mmol) and dipyatriz (0.196 g,
1/3 mmol) in a H2O-CH3CN 1:1 (v/v) mixture. Crystals of 1 as
dark blue prisms were grown from the resulting dark blue
solution by slow evaporation at room temperature in a hood.
The yield is practically quantitative. Anal. Calcd for
C66H58Cl6Cu3N24O29 (1): C, 38.59; H, 2.82; N, 16.36. Found:
C, 39.45; H, 2.75; N, 16.25%. Main IR peaks (KBr, cm-1):
3440s,br (O-H); 3105w, 3035w, and 3010w (C-H aromatic);
1605s (CdN); 1550s (CdC); 1482s, 1467s, 1385s (C-C +
C-N); 1145s, 113s, 1085s, and 945w (Cl-O, uncoordinated
perchlorate).24
hydrogen bonding and anion-π interactions)19 have at-
tracted the attention to this ligand by different research
groups.20,21 In fact, a survey of the structural reports
of dipyatriz-containing metal complexes shows that this
polypyridyl ligand usually exhibits the expected tris-
or bis-bidentate coordination modes by using its three
or two dipyridylamino fragments as donors.19-22 Sur-
prisingly, it can also adopt the rather unexpected bi-
{[Cu4(dipyatriz)2(H2O)2(NO3)2(ox)2](NO3)2 2H2O}n (2). Sin-
3
gle crystals of 2 were grown by slow diffusion in an H-shaped
tube containing concentrated aqueous solutions of sodium
oxalate in one arm (0.034 g, 0.25 mmol) and a mixture of
copper(II) nitrate trihydrate (0.121 g, 1/2 mmol) and dipyatriz
(0.098 g, 1/6 mmol) in the other one. The two arms were carefully
filled by dropwise addition of water untilthe H-tube was full (total
volume ca. 40 cm3). It was covered with parafilm to avoid any
evaporation of the solvent and allowed to diffuse at room
temperature. The diffusion was finished after 2 months. Blue
(through
a dipyridylamino moiety) and tridentate
(across one triazine-nitrogen and two nonadjacent pyr-
idyl rings) binding modes simultaneously.20d These fea-
tures support the versatility and richness of the dipyatriz
molecule as a ligand.
In the present work we report the preparation and X-ray
characterization of the trinuclear [Cu3(dipyatriz)2(H2O)3]
plate-like crystals of 2 together with a small amount of Cu(ox) 1/
3
3H2O as a pale green solid were obtained separately. The yield
based on dipyatriz is about 90%. Anal. Calcd for C70H58Cu4-
N28O25 (2): C, 43.23; H, 2.98; N, 20.16. Found: C, 43.05; H, 2.92;
N, 20.05%. Main IR peaks (KBr, cm-1): 3420s,br (O-H), 3110w,
3085w and 3015w (C-H aromatic); 1710w and 1675s (νasCO);
1605s (CdN) and 1550s (CdC); 1485s, 1470s and 1380s, (C-C +
C-N); 2430w, 1390s, and 830w (N-O uncoordinated nitrate).24b
(ClO4)6 2H2O (1), 2D {[Cu4(dipyatriz)2(H2O)2(NO3)2(ox)2]
3
3
(NO3)2 2H2O}n (2), and cage-like [Cu6(dipyatriz)2(H2O)9-
(NO3)3(ox)3](NO3)3 4H2O (3) copper(II) complexes (ox =
3
oxalate) together with the investigation of their magnetic
properties as a function of the temperature.
[Cu6(dipyatriz)2(H2O)9(NO3)3(ox)3](NO3)3 4H2O (3). A mix-
3
ture of copper(II) nitrate trihydrate (0.241 g, 1 mmol), dpyatriz
(0.196 g, 1/3 mmol), sodium oxalate (0.111 g, 0.83 mmol), and
30 cm3 of water were sealed ina 45 mL stainless-steel reactor with a
Teflon linear, and heated at 150 ꢀC during 48 h. After cooling, a
few X-ray quality dark blue prisms of 3 were collected from the
Teflon liner and air-dried. The formula of 3 was determined by
X-ray diffraction. IR (KBr, cm-1): 3422s,br (O-H), 3115w,
3080w, 3050w, and 3010w (C-H aromatic); 1677s (νasCO),
1360m and 1320m (νsCO) and 805m (δOCO); 1608s (CdN) and
1550s (CdC); 1483s and 1470s (C-C + C-N); 2430w, 1390s, and
830w (N-O uncoordinated nitrate).
Experimental Section
Materials and Methods. Reagents (except dipyatriz) and
solvents used in the synthesis of 1-3 were purchased from
commercial sources and used without further purification.
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Eur. J. Inorg. Chem. 2006, 29.
Physical Measurements. IR spectra of 1-3 as KBr pellets were
registered on a Bruker IF S55 spectrometer. Magnetic susceptibility
measurements on polycrystalline samples of 1-3were carried out in
the temperature range 1.9-295 K with a SQUID magnetometer
under applied magnetic fields of 1 T (T g 100 K) and 1000 G (T <
100 K). Diamagnetic corrections of the constituent atoms were
estimated from Pascal constants25 and found to be as -998 ꢀ
10-6 (1), -471 ꢀ 10-6 (2), and -1090 ꢀ 10-6 cm3 mol-1 (3) per
three (1), two (2), and six (3) copper(II) ions. Magnetic data were
also corrected for the temperature-independent paramagnetism
[60 cm3 mol-1 K per copper(II) ion] and the sample holder.
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´
Roubeau, O.; Aromı, G.; Donnadieu, B.; Massera, C.; Lutz, M.; Spek, A. L.;
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Teat, S. J.; Masciocchi, N.; Galli, S.; Sironi, A.; Gamez, P.; Reedijk, J. Inorg.
~
Chem. 2007, 46, 4583. (f) Barrios, L. A.; Aromı, G.; Frontera, A.; Quinonero,
´
ꢁ
D.; Deya, P. M.; Gamez, P.; Roubeau, O.; Shotton, E. J.; Teat, S. J. Inorg.
Chem. 2008, 47, 5873.
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London, 1968.
(23) Birappa, K.; Yoshimura, M. Handbook of Hydrothermal Techno-
logy: Technology for Crystal Growth and Materials Processing; William
Andrew Inc.: Norwich, NY, 2001.

Article
Inorganic Chemistry, Vol. 48, No. 14, 2009 6633
Table 1. Crystal Data and Details of the Structure Determination for the Complexes [Cu3(dipyatriz)2(H2O)3](ClO4)6 2H2O (1), {[Cu4(dipyatriz)2(H2O)2(NO3)2(ox)2]
3
(NO3)2 2H2O}n (2), and [Cu6(dipyatriz)2(H2O)9(NO3)3(ox)3](NO3)3 4H2O (3)
3
3
compound
1
2
3
formula
M
C66H58Cl6Cu3N24O29
2054.68
C70H58Cu4N28O25
1945.60
C144H148Cu12N60O86
4857.70
crystal system
space group
a, A
orthorhombic
C2cb
15.793(3)
19.766(3)
27.921(4)
8716(2)
4
293(2)
1.566
0.71073
1.001
orthorhombic
Pcab
tetragonal
P42bc
30.383(4)
30.383(4)
22.292(5)
20578(6)
4
100(2)
1.568
0.75130
1.319
15.1193(11)
21.965(2)
24.3216(8)
8077.1(10)
4
293(2)
1.600
0.71073
1.135
b, A
c, A
V, A3
Z
T, K
F
calc (Mg m-3
λ(Mo KR, A)
)
μ(Mo KR, mm-1
)
R1, I > 2σ(I) (all)
wR2, I > 2σ(I) (all)
measured reflections (Rint
independent reflections
[I > 2σ(I)]
0.0695 (0.1494)
0.1056 (0.1305)
25020 (0.1130)
6074 (3506)
0.0708 (0.0909)
0.2038 (0.2323)
30711 (0.0725)
9854 (7812)
0.0896 (0.0899)
0.2698 (0.2714)
574924 (0.1750)
20831 (20642)
)
goodness-of-fit on F2
1.052
1.108
1.369
Crystal Structure Determination and Refinement. X-ray dif-
fraction data on single crystals of 1-3 of dimensions 0.10 ꢀ
0.10 ꢀ 0.30 (1), 0.04 ꢀ 0.30 ꢀ 0.30 (2), and 0.30 ꢀ 0.30 ꢀ
0.60 mm (3) were collected on a Nonius Kappa CCD
diffractometer with graphite-monochromated Mo KR radiation
(λ = 0.71073 A) at 293 K (1 and 2) and at the ESRF synchrotron
BM16 beamline (Grenoble, France) using λ = 0.75130 A at
100 K (3). Data were indexed, integrated, and scaled using the
EVALCCD (1 and 2) and HKL2000 programs.26 The values of
the minimum and maximum transmission factors were 0.7533/
0.9065 (1), 0.7260/0.9560 (2), and 0.5049/0.6930 (3).
The structures of 1-3 were solved by direct methods
through the SHELX97 computational program.27 All non-
hydrogen atoms of 1-3 (except the nitrate groups from 3)
were refined anisotropically by full-matrix least-squares tech-
niques based on F2 using SHELX97. The hydrogen atoms of
the dipyatriz molecule in 1-3 were positioned geometrically
and refined with a riding model. The hydrogen atoms of all
water molecules from 1-3 were neither found nor considered
in the refinement. In 2, the O4NA, O5NA, and O6NA oxygen
atoms present an occupancy factor of 0.74 while O4NB,
O5NB, and O6NB show an occupancy factor of 0.26, indicat-
ing an alternation of the absolute position of the nitrate group
between the cells of the nitrate coordinated to one copper(II)
atom. Also two crystallization water molecules in 2 share their
occupancy factor, O2W (0.51) and O3W (0.49), while O4W
present an occupation of 0.50. The crystallization water
molecules [O11W to O17W] in 3 present an occupancy factor
of 0.5.
Table 2. Selected Bond Lengths (A), Angles (deg) and Hydrogen Bonds in 1a
Copper Environment
Cu(1)-N(7)
Cu(1)-N(8)
Cu(1)-N(9a)
Cu(1)-N(10a)
Cu(1)-O(1W)
1.978(11) Cu(2)-N(11)
2.010(10) Cu(2)-N(12)
2.032(9) Cu(2)-O(2W)
2.041(9)
2.039(8)
2.000(8)
2.181(8)
2.154(6)
N(7)-Cu(1)-N(8)
N(7)-Cu(1)-N(10a)
N(7)-Cu(1)-N(9a)
N(7)-Cu(1)-O(1w)
N(8)-Cu(1)-N(10a)
N(8)-Cu(1)-N(9a)
N(8)-Cu(1)-O(1W)
85.5(4)
N(11)-Cu(2)-N(12)
86.0(3)
160.5(4) N(11)-Cu(2)-N(11a) 165.0(5)
94.6(4) N(11)-Cu(2)-N(12a) 92.0(3)
102.6(4) N(11)-Cu(2)-O(2W) 97.5(3)
89.4(3) N(12)-Cu(2)-N(12a) 164.6(5)
167.9(4) N(12)-Cu(2)-O(2W) 97.7(2)
94.7(4) N(12a)-Cu(2)-O(2W) 97.7(2)
N(10a)-Cu(1)-N(9a) 86.6(4)
N(10a)-Cu(1)-O(1W) 96.5(4)
N(9a)-Cu(1)-O(1W) 97.1(4)
Intermolecular O O Distances (A)
3 3 3
O(1W) O(3 Wb)
O(1W) O(10c)
O(2W) O(5)
2.612(18) O(2W) O(5a)
2.930(15) O(3W) O(11)
2.845(8) O(3W) O(3d)
2.845(8)
3.08(2)
3.10(2)
3 3 3
3 3 3
3 3 3
3 3 3
3 3 3
3 3 3
a Symmetry code: (a) = x, -y, 1-z; (b) = 1+x, -y+1/2, 1/2+z;
(c) 1+x, -y, 1-z; (d) -1/2+x, -y+1/2, 1-z.
Results and Discussion
Description of the Structures. [Cu3(dipyatriz)2(H2O)3]-
A summary of the cell parameters and refinement conditions
for 1-3 are listed in Table 1, whereas main bond lengths and
bond angles together with the hydrogen bonds are given in
Tables 2 (1), 3 (2), and 4 (3). The final geometrical calculations
and the graphical manipulations were carried out with the
PARST,28 PLATON,29 and DIAMOND30 programs.
Crystallographic data for the structures 1-3 have been
deposited at the Cambridge Crystallographic Data Centre with
CCDC reference nos. 722374 (1), 722375 (2), and 722376 (3).
(ClO4)6 2H2O (1). The structure of 1 consists of alterna-
3
ting [Cu3(dipyatriz)2(H2O)3]6+ cations and perchlorate an-
ions leading to an ionic three-dimensional (3D)-network
(Figure 1). The tricopper(II) units of formula [Cu3(dipya-
triz)2(H2O)3]6+ can be described as the face-to-face assembly
of two dipatriz molecules acting as tris-bidentate ligands
though their dipyridylamino moieties toward three copper
(II) ions (Figure 2, panels a and b). The distance between the
mean planes of the two triazine rings is 3.9809(6) A and
although this value is somewhat greater than the distance
usually found for aromatic stacking (3.5 A), such lengthening
is often observed for aromatic nitrogen-containing ligands.31
It deserves to be noted that this triazine centroid-to-centroid
distance in 1 remains within the range of previously reported
(26) EVALCCD; Duisenberg, A. J. M.; Kroon-Batenburg, L. M. J.;
Schreurs, A. M. M. J. Appl. Crystallogr. 2003, 36, 220.
(27) Sheldrick, G. M. SHELX97, Programs for Crystal Structure Analysis
::
::
(Release 97-2); Institut for Anorganische Chemie der Universitat
::
::
Gottingen: Gottingen, Germany, 1998.
(28) Nardelli, M. J. Appl. Crystallogr. 1995, 28, 659.
(29) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.
(30) DIAMOND 2.1d; Crystal Impact GbR, K. Branderburg & H. Putz
GbR: Bonn, Germany, 2000.
(31) Janiak, C. J. J. Chem. Soc., Dalton Trans. 2000, 3885.

6634 Inorganic Chemistry, Vol. 48, No. 14, 2009
Yuste et al.
Table 3. Selected Bond Lengths (A), Angles (deg), and Hydrogen Bonds in 2a,b
Table 4. Selected Bond Lengths (A), Angles (deg), and Hydrogen Bonds in 3 a
Cu(1)-N(7)
Cu(1)-N(8)
Cu(1)-O(1)
Cu(1)-O(3)
Cu(1)-O(1W)
Cu(1)-O(2W)
2.006(5)
2.013(5)
1.976(5)
2.016(4)
2.430(7)
2.385(6)
Cu(4)-N(21)
Cu(4)-N(22)
Cu(4)-O(6)
Cu(4)-O(8)
Cu(4)-O(6W)
Cu(4)-O(18N)
1.987(6)
1.998(6)
1.983(6)
1.989(5)
2.255(6)
2.7443(11)
Copper Environment
Cu(1)-N(7)
Cu(1)-N(8)
Cu(1)-O(1)
Cu(1)-O(2)
Cu(1)-O(5NA)
1.983(3)
1.996(3)
1.939(3)
1.934(3)
2.420(5)
Cu(2)-N(9b)
Cu(2)-N(10b)
Cu(2)-N(12)
Cu(2)-O(1W)
Cu(2)-N(11)
Cu(2)-O(4c)
2.066(3)
2.008(3)
2.009(3)
2.110(3)
2.271(3)
2.336(3)
Cu(2)-N(19)
Cu(2)-N(20)
Cu(2)-O(2)
Cu(2)-O(4)
Cu(2)-O(3W)
Cu(2)-O(4W)
1.978(6)
2.011(5)
2.000(5)
1.990(4)
2.395(7)
2.366(9)
Cu(5)-N(11)
Cu(5)-N(12)
Cu(5)-O(9)
Cu(5)-O(11)
Cu(5)-O(7W)
Cu(5)-O(8W)
2.007(6)
1.976(6)
2.005(6)
2.012(7)
2.442(10)
2.309(5)
N(7)-Cu(1)-N(8)
N(7)-Cu(1)-O(1)
N(7)-Cu(1)-O(2)
90.85(13) N(9b)-Cu(2)-N(10b) 88.14(12)
172.96(14) N(9b)-Cu(2)-O(1W) 172.70(12)
90.55(13) N(9b)-Cu(2)-N(12) 91.49(12)
Cu(3)-N(9)
Cu(3)-N(10)
Cu(3)-O(5)
Cu(3)-O(7)
Cu(3)-O(5W)
Cu(3)-O(13N)
2.015(5)
1.983(5)
1.971(6)
1.999(5)
2.353(7)
2.477(7)
Cu(6)-N(23)
Cu(6)-N(24)
Cu(6)-O(10)
Cu(6)-O(12)
Cu(6)-O(9W)
Cu(6)-O(1N)
2.019(6)
1.951(7)
1.981(7)
1.973(7)
2.421(14)
2.347(2)
(7)-Cu(1)-O(5NA) 103.07(18) N(9b)-Cu(2)-N(11) 102.34(11)
N(8)-Cu(1)-O(1)
N(8)-Cu(1)-O(2)
92.91(13) N(9b)-Cu(2)-O(4c)
89.02(11)
171.69(15) N(10b)-Cu(2)-O(1W) 91.24(13)
N(8)-Cu(1)-O(5NA) 83.49(18) N(10b)-Cu(2)-N(12) 178.14(11)
O(1)-Cu(1)-O(2) 84.89(13) N(10b)-Cu(2)-N(11) 92.29(11)
N(7)-Cu(1)-N(8)
N(7)-Cu(1)-O(3)
N(7)-Cu(1)-O(1)
N(7)-Cu(1)-O(1W)
N(7)-Cu(1)-O(2W)
N(8)-Cu(1)-O(3)
N(8)-Cu(1)-O(1)
N(8)-Cu(1)-O(1W)
N(8)-Cu(1)-O(2W)
O(1)-Cu(1)-O(3)
O(1)-Cu(1)-O(1W)
O(1)-Cu(1)-O(2W)
O(3)-Cu(1)-O(1W)
O(3)-Cu(1)-O(2W)
O(1W)-Cu(1)-O(2W)
89.8(2)
174.5(2)
90.6(2)
94.9(2)
91.0(2)
95.61(19)
177.4(3)
91.7(2)
87.6(2)
83.91(19)
90.8(3)
89.9(3)
86.2(3)
88.0(2)
174.0(3)
N(21)-Cu(4)-N(22)
N(21)-Cu(4)-O(8)
N(21)-Cu(4)-O(6)
N(21)-Cu(4)-O(6W)
N(21)-Cu(4)-O(18N)
N(22)-Cu(4)-O(8)
N(22)-Cu(4)-O(6)
N(22)-Cu(4)-O(6W)
N(22)-Cu(4)-O(18N)
O(6)-Cu(4)-O(8)
O(6)-Cu(4)-O(6W)
O(6)-Cu(4)-O(18N)
O(8)-Cu(4)-O(6W)
O(8)-Cu(4)-O(18N)
O(6W)-Cu(4)-O(18N)
90.3(2)
O(1)-Cu(1)-O(5NA) 83.28(18) N(10b)-Cu(2)-O(4c) 88.48(11)
O(2)-Cu(1)-O(5NA) 104.16(19) O(1W)-Cu(2)-N(12) 88.90(13)
O(1W)-Cu(2)-N(11) 84.95(12)
169.3(2)
88.3(3)
91.8(3)
O(1W)-Cu(2)-O(4c) 83.69(12)
103.0(2)
94.5(2)
N(12)-Cu(2)-N(11)
N(12)-Cu(2)-O(4c)
N(11)-Cu(2)-O(4c)
89.58(11)
89.69(11)
168.63(11)
170.6(3)
93.6(3)
103.02(16)
85.3(2)
Oxalate Ligand
95.7(4)
O(1)-C(34)
O(3)-C(34)
C(34)-C(35)
1.270(5)
1.214(6)
1.552(6)
O(2)-C(35)
O(4)-C(35)
1.255(5)
1.231(5)
68.0(2)
97.4(3)
70.05(17)
159.67(16)
O(1)-C(34)-O(3)
O(1)-C(34)-C(35)
O(3)-C(34)-C(35)
C(34)-C(35)-O(2)
C(34)-C(35)-O(4)
125.0(4)
114.8(4)
120.2(4)
115.0(4)
120.0(4)
O(2)-C(35)-O(4)
Cu(1)-O(1)-C(34)
Cu(1)-O(2)-C(35)
Cu(2d)-O(4)-C(35)
125.0(4)
112.3(3)
113.0(3)
131.1(3)
N(19)-Cu(2)-N(20)
N(19)-Cu(2)-O(4)
N(19)-Cu(2)-O(2)
N(19)-Cu(2)-O(3W)
N(19)-Cu(2)-O(4W)
N(20)-Cu(2)-O(4)
N(20)-Cu(2)-O(2)
N(20)-Cu(2)-O(3W)
N(20)-Cu(1)-O(4W)
O(2)-Cu(2)-O(4)
O(2)-Cu(2)-O(3W)
O(2)-Cu(2)-O(4W)
O(4)-Cu(2)-O(3W)
O(4)-Cu(2)-O(4W)
O(3W)-Cu(2)-O(4W)
88.8(2)
176.4(2)
93.5(2)
93.2(29
87.5(3)
93.4(29
177.0(2)
94.1(2)
88.9(2)
84.2(29
83.9(3)
93.1(3)
83.8(2)
95.4(3)
177.0(3)
N(11)-Cu(5)-N(12)
N(11)-Cu(5)-O(9)
N(11)-Cu(5)-O(11)
N(11)-Cu(5)-O(7W)
N(11)-Cu(5)-O(8W)
N(12)-Cu(5)-O(9)
N(12)-Cu(5)-O(11)
N(12)-Cu(5)-O(7W)
N(12)-Cu(5)-O(8W)
O(9)-Cu(5)-O(11)
O(9)-Cu(5)-O(7W)
O(9)-Cu(5)-O(8W)
O(11)-Cu(5)-O(7W)
O(11)-Cu(5)-O(8W)
O(7W)-Cu(5)-O(8W)
92.1(3)
175.1(2)
93.9(3)
90.9(3)
92.3(2)
89.7(3)
173.6(2)
93.9(3)
93.0(2)
84.1(3)
84.4(3)
92.1(2)
83.8(3)
88.9(2)
172.2(3)
Intermolecular O O Distances (A)
3 3 3
O(1W) O(6NAe)
O(1W) O(2Ne)
2.831(8)
2.847(7)
2.917(15) O(4W) O(6NAg)
O(3W) O(1N)
2.70(2)
3.18(4)
3.05(2)
3 3 3
3 3 3
O(3W) O(4W)
3 3 3
3 3 3
O(2W)
O(3)
3 3 3
3 3 3
O(2W)-O(1Nf)
3.179(16)
a Symmetry code: (b) = -x+2, -y, -z; (c) = x-1/2, -y, -z+1/2;
(d) = x+1/2, -y, -z+1/2; (e) x-1/2, -y+1/2, z; (f) = -x+5/2, -1/2
+y, -z; (g) = -x+5/2, y, -1/2+z. b Only components with greater
occupancy factors [O(5NAa), O(4NA) and O(3NA)] of the coordinated
nitrate anion are given.
N(9)-Cu(3)-N(10)
N(9)-Cu(3)-O(7)
N(9)-Cu(3)-O(5)
91.2(2)
175.1(2)
91.2(2)
94.5(2)
91.8(1)
92.7(2)
177.5(3)
91.7(3)
92.8(2)
84.8(2)
88.5(3)
86.7(3)
88.3(2)
85.1(2)
172.2(2)
N(23)-Cu(6)-N(24)
N(23)-Cu(6)-O(10)
N(23)-Cu(6)-O(12)
N(23)-Cu(6)-O(9W)
N(23)-Cu(6)-O(1N)
N(24)-Cu(6)-O(10)
N(24)-Cu(6)-O(12)
N(24)-Cu(6)-O(9W)
N(24)-Cu(6)-O(1N)
O(10)-Cu(6)-O(12)
O(10)-Cu(6)-O(9W)
O(10)-Cu(6)-O(1N)
O(12)-Cu(6)-O(9W)
O(12)-Cu(6)-O(1N)
O(9W)-Cu(6)-O(1N)
91.2(3)
176.4(4)
92.1(3)
94.2(3)
105.2(2)
92.4(3)
176.7(3)
94.2(6)
99.9(2)
84.4(3)
84.9(4)
74.9(3)
85.2(7)
79.6(4)
155.7(5)
N(9)-Cu(3)-O(5W)
N(9)-Cu(3)-O(13N)
N(10)-Cu(3)-O(7)
N(10)-Cu(3)-O(5)
N(10)-Cu(3)-O(5W)
N(10)-Cu(3)-O(13N)
O(5)-Cu(3)-O(7)
O(5)-Cu(3)-O(5W)
O(5)-Cu(3)-O(13N)
O(7)-Cu(3)-O(5W)
O(7)-Cu(3)-O(13N)
O(5W)-Cu(3)-O(13N)
values in analogous dipyatriz-containing copper(II) com-
plexes (from 3.67 to 4.125 A).20f,21,22 The positive charge
of the trinuclear entity in 1 is compensated by six non-
coordinated perchlorate anions. Two of them are located
very close to each triazine ring evidencing the occurrence of
anion-π interactions with a centroid O(6) distance of
3.097(12) A and an angle of the centroid O(6) axis to the
3 3 3
3 3 3
plane of 78.5ꢀ (Figure 2c). This type of noncovalent triazine
centroid-anion interaction have been studied by means of
high level ab initio calculations,20f and it has been proposed
as a new anion recognition module in cyclophane chemis-
try.32 Hydrogen bonds involving some of the perchlorate-
oxygen atoms and the coordinated and free water molecules
further stabilize the structure of 1 (see end of Table 2).
The copper(II) ions in 1 are in square-pyramidal
coordination geometry [τ = 0.012 and 0.003 for Cu-
(1) and Cu(2), respectively],33 with the basal positions
Intermolecular O O Distancesa (A)
3 3 3
O(1W) O(17N)
2.810(8)
2.836(6)
2.911(6)
2.676(17)
2.713(10)
2.903(18)
2.743(18)
2.747(7)
2.823(5)
2.966(6)
2.708(4)
O(9W) O(15W)*
2.490(23)
3.122(13)
2.943(11)
2.802(20)
2.9305(3)
2.851(24)
3.100(3)
3 3 3
3 3 3
O(2W) O(7Na)
O(11W) O(5N)
3 3 3
3 3 3
O(3W)...O(16N)
O(3W) O(15W)*
O(13W) O(11d)
O(13W) O(12We)*
3 3 3
3 3 3
3 3 3
O(4W) O(12N)
O(4W) O(12W)*
O(14W)* O(12We)*
3 3 3
3 3 3
O(14W)* O(18Nd)
3 3 3
3 3 3
O(6W) O(16W)*
O(16W)* O(15Nc)
3 3 3
3 3 3
O(6W) O(7Nb)
O(16W)* O(2f)
2.880(2)
3 3 3
3 3 3
O(8W) O(4Nc)
O(17W)* O(13W)*
2.716(33)
2.971(3)
3 3 3
3 3 3
O(8W) O(9Nc)
O(9W) O(14Wc)*
O(17W)* O(8 g)
3 3 3
3 3 3
3 3 3
a Symmetry codes: (a)= 1/2-x, 1/2-y, 1/2+z; (b) = x, 1-y, 1/2+z;
(c) = x, y, 1+z ; (d) = x, y, -1+z; (e) = x, 1-y, -1/2+z; (f) = 1/2+x,
1/2-y, z; (g) = -1/2+x, 1/2+y, -1/2+z. * These atoms have an
occupancy factor of 50%.
(32) Mascal, M.; Armstrong, A.; Bartberger, M. D. J. Am. Chem. Soc.
2002, 124, 6274.
(33) Addison, A. W.; Rao, T. N.; Reedijk, J.; Vanrijn, J.; Verschoor, G. C.
J. Chem. Soc., Dalton Trans. 1984, 1349.

Article
Inorganic Chemistry, Vol. 48, No. 14, 2009 6635
Figure 1. View along the c-axisofthe crystal packing of1. The hydrogen
atoms were omitted for clarity.
occupied by the pyridyl-nitrogen donors of the dipya-
triz molecule and the axial sites pointing outward in a
radial manner, being filled by water molecules. A
crystallographic 2-fold axis going through the Cu(2)-
O(2W) bond relates half of the molecule to the other.
The basal Cu-N distances range from 1.978(11) to
2.041(9) A, values which are somewhat shorter than
the apical Cu-O(w) coordination bonds [2.154(6) and
2.181(8) A for Cu(1)-O(1W) and Cu(2)-O(W2), re-
spectively]. The Cu-N distances compare well with
those observed in other structurally characterized di-
pyatriz-containing copper(II) complexes.20a,20c,20f,21,22
The values of the dihedral angles between the mean
basal planes of adjacent copper(II) ions are 51.48ꢀ
[Cu(1)/Cu(2)] and 64.26ꢀ [Cu(1)/Cu(1a); (a) = x, -y,
-z+1].
The triazine ring of the dipyatriz ligand is planar within
the experimental error [largest deviation from the mean
plane 0.026(10) A for C(1)]. The values of the dihedral
angle between the triazine ring and each of its pyridyl vary
in the range 43.71-64.49ꢀ. Average values for the C-
C [1.368 A] and C-N [1.348 A] bond lengths and C-N
inter-ring bonds [1.426 A] of the dipyatriz ligand in 1
compare well with those observed in the free molecule.18a
The dipyatriz ligand adopts the tris-bidentate coordina-
tion mode through its six pyridyl nitrogen atoms toward
three copper(II) ions, the values of the copper-copper
separation within the resulting tricopper(II) core being
8.057(2) [Cu(1) Cu(2)] and 8.351(2) A [Cu(1) Cu
3 3 3
3 3 3
(1a)]. These values are somewhat shorter than the shortest
intermolecular copper-copper distance [9.686(2) A for
Cu(1) Cu(1e); (e) = x+1/2, y, -z+3/2].
{[Cu4(dipyatriz)2(H2O)2(NO3)2(ox)2](NO3)2 2H2O}n
3 3 3
3
(2). The structure of 2 consists of an unprecedented two-
dimensional (2D) arrangement of copper(II) ions where
centrosymmetric tetranuclear [Cu4(dipyatriz)2(H2O)2-
(NO3)2] units [Figure 3 (left)] are connected by oxalate
ligands exhibiting the bidentate/monodentate bridging
mode [Figure 3 (right)] leading to cationic bilayers which
grow in the ac plane (Figure 4). Non-coordinated nitrate
groups and crystallization water molecules are also pre-
sent in the crystal structure. One of these water molecules
[O(4W)] has an occupancy factor of 0.5 whereas the other
one occupies two regular alternating crystallographic
sites with occupancy factors 0.51532 [O(2W)] and
0.48468 [O(3W)]. They are involved in an extensive net-
work of hydrogen bonds together with the non-coordi-
nated oxalate-oxygen [O(3)] and the coordinated water
molecule [O(1W)] (see end of Table 3), the whole resulting
in a 3D supramolecular structure (see Supporting Infor-
mation, Figure S1).
Figure 2. (a) Asymmetric unit of compound 1. (b) Perspective view
along the b-axis of of the trinuclear [Cu3(dipyatriz)2(H2O)3]6+ cation in 1
showing the quasi face-to-face conformation of the s-triazine rings. (c)
Side view of the tricopper(II) unit of 1 showing the anion-π interaction
between one perchlorate-oxygen atom and the electron-deficient s-tria-
zine ring. The hydrogen atoms and the pyridyl rings of the two dipyatriz
ligands were omitted for the sake of clarity. Symmetry code: (a) = x, -y,
-z+1.
Two crystallographically independent copper(II) ions
[Cu(1) and Cu(2)] occur in 2. Cu(1) is five-coordinate in
a distorted square pyramidal surrounding with one biden-
tate dipyridylamine unit from a dipyatriz ligand [N(7) and
N(8)] and two oxalate-oxygens [O(1) and O(2)] in the basal
positions and an oxygen atom from a disordered unidentate
nitrate [O(5NA)] in the apical site. Because of this disorder,
the inclusion of the O(4NB) atom [occupancy factors for

6636 Inorganic Chemistry, Vol. 48, No. 14, 2009
Yuste et al.
O(5NA) and O(4NB) are 0.742(13) and 0.258(13), respec-
tively] in the coordination sphere of Cu(1) could be con-
sidered, but we have kept the oxygen atom with the greater
occupancy factor for a better clarity of the drawings. In such
a case, the parameter τ for Cu(1) is 0.017. The equatorial Cu
(1)-N [1.983(3) and 1.996(3) A] and Cu(1)-O bonds
[1.934(3) and 1.939(3) A] can be considered as normal. The
axially coordinated nitrate is at a somewhat larger distance
[Cu(1)-O(N5A) = 2.420(5) A and Cu(1)-O(N4B) =
2.39(2) A]. Cu(2) is located in an elongated octahedral
environment formed by two pairs of N-coordinating 2-
pyridyl groups belonging to two different dipyatriz ligands
[N(9b), N(10b), N(11) and N(12); (b) = -x+2, -y, -z],
a water molecule [O(1W)] and an oxalate-oxygen atom
[O(4c); (c) = x-1/2, -y, -z+1/2]. The bonds at Cu(2) in
the equatorial plane vary in the range 2.009(3)-2.110(3) A
whereas the axial bond distances are 2.271(3) [Cu(2)-
N(11)] and 2.336(3) A [Cu(2)-O(4c)].
Figure 3. (Left) Perspective view of the tetranuclear fragment of 2
showing the copper assembling through the bridging dipyatriz ligands
(the coordinated nitrate is disordered over two positions O5NA:O4NB
with occupancy 74:26% and the hydrogen atoms were omitted for
clarity. (Right) Bridging mode of the oxalate ligand in 2. Symmetry
code: (b) = -x+2, -y, -z; (c) = x-1/2, -y, -z+1/2; (d) = -x+1/2,
-y, -z+1/2.
The two centrosymmetrically related dipyatriz li-
gands in 2 adopt the tris-bidentate coordination mode
through the dipyridylamino fragments, as observed in
1. However, here they are mutually shifted in contrast
to the superimposed situation of the triazine rings
occurring in 1. This feature precludes any π-π stacking
between the s-triazine rings of the dipyatriz molecules
in 2. In addition, no anion
tions occur in 2. The copper-copper separation
through the dipyatriz bridge are 8.011(1), 7.801(1),
aromatic ring interac-
3 3 3
and 9.079(1) A for Cu(1)
and Cu(2)
values being very close to those observed in 1.
Cu(2), Cu(1)
Cu(2b), respectively, the two former
Cu(2b),
3 3 3
3 3 3
3 3 3
The oxalate ligand in 2 is practically planar [largest
deviation from the mean plane is 0.038(6) A at O(3)]
and it adopts the asymmetric bidentate/monodentate
(outer) bridging mode, the resulting copper-copper
separation being 5.609(1) A [Cu(1) Cu(2d); (d) = x+
3 3 3
1/2, -y, -z+1/2]. This asymmetric bridging mode of
the oxalate ligand has been observed in a red-
uced number of homo-34-37 and heterometallic38,39
(34) Scott, K. L.; Wieghardt, K.; Sykes, A. G. Inorg. Chem. 1973, 12, 655.
(35) Michaelides, M.; Skoulika, S.; Aubry, A. Mater. Res. Bull. 1988, 23,
579.
(36) Sheng-Hua, H.; Ru-Ji, W.; Mak, T. C. W. J. Cryst. Spectrosc. Res.
1990, 20, 99.
(37) (a) Kansikas, J.; Pajunen, A. Acta Crystallogr. 1980, B36, 2423. (b)
Geiser, U.; Ramakrishna, B. L.; Willett, R. D.; Hulsbergen, F. B.; Reedijk, J.
Inorg. Chem. 1987, 26, 3750. (c) Oshio, H.; Nagashima, U. Inorg. Chem.
ꢀ~
ꢀ
1992, 31, 3295. (d) Nunez, H.; Timor, J. J.; Server-Carrion, J.; Soto, J.;
ꢀ
Escriva, E. Inorg. Chim. Acta 2001, 318, 8. (e) Carranza, J.; Brennan, C.;
Sletten, J.; Vangdal, B.; Rillema, P.; Lloret, F.; Julve, M. New J. Chem. 2003,
27, 1775. (f) Li, Y.; Yang, P.; Huang, Z.; Xie, F. Acta Crystallogr. 2004, E60,
m1710.
ꢀ
(38) (a) Chiozzone, R.; Gonzalez, R.; Kremer, C.; De Munno, G.; Cano,
J.; Lloret, F.; Julve, M.; Faus, J. Inorg. Chem. 1999, 38, 4745. (b) Chiozzone,
ꢀ
R.; Gonzalez, R.; Kremer, C.; De Munno, G.; Armentano, D.; Cano, J;
Lloret, F.; Julve, M; Faus, J. Inorg. Chem. 2001, 40, 4242.
(39) (a) Shen, H.-Y.; Bu, W.-M.; Liao, D.-Z.; Jing, Z.-H-; Yan, S.-P.;
Wang, G.-L. Inorg. Chem. 2000, 39, 2239. (b) Marinescu, G.; Andruh, M.;
::
~
Lescouezec, R.; Munoz, M. C.; Cano, J.; Lloret, F.; Julve, M. New J. Chem.
ꢀ
2000, 24, 527. (c) Ballester, G.; Coronado, E.; Gimenez-Saiz, Romero, F. M.
Angew. Chem. 2001, 113, 814. (d) Costisor, O.; Mereiter, K.; Julve, M.;
Lloret, F.; Journauz, Y.; Linert, W.; Andruh, M. Inorg. Chim. Acta 2001,
::
324, 352. (e) Lescouezec, R.; Marinescu, G.; Vaissermann, J.; Lloret, F.;
Figure 4. Views along the b- (a) and c-axes (b) of the cationic bilayer
built by the [Cu4(dipyatriz)2(H2O)2(NO3)2(ox)2]2+ units. Counterions,
crystallization water molecules, and hydrogen atoms have been omitted
for clarity.
Faus, J.; Andruh, M.; Julve, M. Inorg. Chim. Acta 2003, 350, 131. (f)
ꢀ
Visinescu, D.; Sutter, P.; Ruiz-Perez, C.; Andruh, M. Inorg. Chim. Acta 2006,
359, 433. (g) Nastase, S.; Maxim, C.; Tuna, F.; Duhayon, C.; Sutter, J. P.;
Andruh, M. Polyhedron 2009, 28, 1688.

Article
Inorganic Chemistry, Vol. 48, No. 14, 2009 6637
Figure 6. Projection along the a-axis of the packing of the hexanuclear
units in 3. The non-coordinated nitrate anions and the crystallization
water molecules were omitted for clarity.
independent, and all of them are six-coordinated in
elongated octahedral surroundings. Two oxalate-oxygen
and two pyridyl-nitrogen atoms occupy the equatorial
positions at all copper atoms whereas two water mole-
cules [at Cu(1), Cu(2), and Cu(5)] or a nitrate-oxygen
atom and a water molecule [at Cu(3), Cu(4), and Cu(6)]
fill the axial sites. The equatorial Cu-N and Cu-O
bond lengths vary in the ranges 1.951(7)-2.019(6) and
1.972(6)-2.017(6) A, respectively. These values are shorter
than the axial Cu-Ow [2.255(6)-2.442(10) A] and Cu-
Onitrate [2.347(2)-2.744(1) A]. The short bite of the bis-
chelating oxalato [values spanning in the range 83.9(2)-
85.3(2)ꢀ] is one of the main factors accounting for the
distortion of the ideal octahedron around each copper
atom. The set of donor atoms in the equatorial positions
at each copper atom are practically planar, the largest
deviation from the mean plane being 0.046(9) A for O(5)
around Cu(3). The copper atoms do not exhibit signifi-
cant deviations from the respective mean equa-
torial planes except Cu(4) which is shifted by 0.160(9) A
toward the axial O(6W) water molecule.
Figure 5. (a) Perspective view of the hexanuclear cage-like unit of
3 showing the atom numberingofthe copper chomophores. (b) Schematic
representationofthe cage. Part ofthe pyridyl rings ofthe dipyatriz ligands
and the hydrogen atoms were omitted for simplicity.
complexes, and it is not as common as the more
frequently found bis-bidentate one. The value of the
dihedral angle between the oxalate plane and the equa-
torial mean planes around Cu(1) and Cu(2) are 4.1(1) and
50.1(1)ꢀ, respectively. The carbon-carbon bond length of
the oxalate ligand [C(34)-C(35) = 1.558(1) A] is as
expected for a single C-C bond, and it is very close
to the carbon-carbon bond distance of 1.574(2) A in
uncoordinated oxalate.40
[Cu6(dipyatriz)2(H2O)9(NO3)3(ox)3](NO3)3 4H2O (3).
3
The structure of 3 is made up of hexanuclear [Cu6-
(dipyatriz)2(H2O)9(NO3)2(ox)3]4+ cations (Figure 5a)
and nitrate counterions which are interlinked by elec-
trostatic interactions and hydrogen bonds (see end of
Table 4). The cationic unit can be viewed as two
[Cu3(dipyatriz)]6+ trinuclear fragments which are pil-
lared by three bis-bidentate oxalate ligands, the whole
resulting in a cylinder-like cage motif which is unpre-
cedented in the extensive coordination chemistry of the
oxalate ligand (Figure 5b). Extensive hydrogen bonds
involving crystallization and coordinated water mole-
cules, and counterions link together the cationic moi-
eties given a 3D supramolecular network. A view of the
packing of the hexanuclear cage-like units is shown in
Figure 6.
The two dipyatriz ligands in 3 adopt the tris-biden-
tate coordination mode observed in 1 and 2. The values
of copper-copper separation within the [Cu3(dipya-
triz] trinuclear fragment are 7.728(4) [Cu(1)
Cu(5)],
Cu(5)],
Cu(6)],
3 3 3
3 3 3
3 3 3
7.476(2) [Cu(1)
8.098(2) [Cu(2)
and 7.886(2) A [Cu(4)
Cu(3)], 7.673(2) [Cu(3)
Cu(4)], 7.835(4) [Cu(2)
3 3 3
3 3 3
Cu(6)]. The two triazine rings
3 3 3
from the cationic cage are somewhat shifted with
respect to each other [the value of the angle between
the normal to the triazine rings and the vector passing
through the centroids of these rings being about 7.0ꢀ
The six copper(II) ions from the cage [Cu(1), Cu(2),
Cu(3), Cu(4), Cu(5), and Cu(6] are crystallographically
with a centroid
centroid distance of 9.963(1) A]. The
3 3 3
oxalate groups in 3 adopt the bis-bidentate coordina-
tion mode, and they are all planar. The bond lengths
and angles within each oxalate in 3 agree with those
(40) Hodgson, D. J.; Ibers, J. A. Acta Crystallogr., Sect B 1969, 25, 469.

6638 Inorganic Chemistry, Vol. 48, No. 14, 2009
Yuste et al.
Figure 7. χMT versus
T plot for complex 1: (O) experimental
data; (solid line) best-fit curve through eq 1 (see text).
Figure 8. χMT versus T plot at T e 100 K for complex 2: (O) experi-
mental data; (solid line) best-fit curve through eqs (3)-(5) (see text).
observed for other oxalato-bridged dicopper(II) complexes
where the oxalate adopts the same coordination mode.41
The values of the copper-copper separation across the
doublets [eq 2]
∧
∧
∧
∧
∧
∧
∧
oxalate bridge are 5.149(2) [Cu(1) Cu(2)], 5.136(2)
3 3 3
H ¼ -J12S1 S2 -J13S1 S3 -J23S2 S3
ð2Þ
3
3
3
[Cu(3) Cu(4)], and 5.112(3) A [Cu(5) Cu(6)].
3 3 3
3 3 3
Magnetic Properties of 1-3. The thermal dependence
of the χMT product for 1 [χM is the magnetic susceptibility
per three copper(II) ions] is shown in Figure 7. χMT at
290 K is equal to about 1.20 cm3 mol-1 K, a value which
in agreement with the presence of three magnetically
isolated copper(II) ions (1.21 cm3 mol-1 K with g =
2.08) Upon cooling, this value remains constant until T =
40 K, and it decreases slightly at lower temperatures to
reach 1.16 cm3 mol-1 K at 1.9 K. This plot is as expected
for a very weak antiferromagnetic coupling within the
trinuclear units.
with J12 = J13 = J23 = J and all the other parameters
having their usual meaning. Best-fit parameters through
eq (1) are J = -0.08(1) cm-1 and g = 2.07(1). The weak
antiferromagnetic interaction between copper(II) ions
through the extended tris-bidentate dipyatriz ligand in 1
is of the same order than those obtained for the analogous
tricopper(II) compounds [Cu3(dipyatriz)2Cl3][CuCl4]Cl
(J = -0.42 cm-1 21a
(dmso = dimethylsulfoxide; J = -1.42 cm-1 21a
the same exchange pathway occurs.
)
and [Cu3(dipyatriz)2Cl6(dmso)3]
where
)
The very weak intramolecular magnetic interaction in
this family of complexes can be easily understood by
considering the poor overlap between the magnetic orbi-
tals through the triazine ring. The unpaired electron on
each copper(II) ion is mainly delocalized in the basal
plane (defined by the four pyridyl-nitrogen atom) which is
practically perpendicular to the triazine ring. This feature
together with the fact that the pyridyl rings are signifi-
cantly tilted with respect to each other and also with
respect to the triazine ring, preclude any significant spin
density on the amino- and triazine nitrogen atoms, ren-
dering practically inefficient the through-bond contribu-
tion to the magnetic coupling. However, a better ability of
the dipyatriz molecule to mediate significant magnetic
interactions and even of different nature can be envisaged
if the triazine ring is directly bound to the spin carrier.
Such a situation has been illustrated by a recent magneto-
structural report on the dipyatriz-bridged diiron(II)
complex [Fe2(dipyatriz)2Cl2](CF3SO3)2 where a ferro-
magnetic coupling (J=+0.46 cm-1) occurs between two
high-spin iron(II) ions.20d
Considering the trinuclear structure of 1, its magnetic
data were analyzed by means of eq (1)
χM ¼ Nβ2g2=4kT½ð1 þ 5e3J=2kT Þ=ð1 þ e3J=2kT Þꢁ ð1Þ
which was derived through the isotropic Heisenberg-
Dirac Hamiltonian for an equilateral triangle of spin
(41) (a) Sletten, J. Acta Chem. Scand. 1983, A37, 569. (b) Julve, M.;
Verdaguer, M.; Kahn, O.; Gleizes, A.; Philoche-Levisalles, M. Inorg. Chem.
1983, 22, 368. (c) Julve, M.; Verdaguer, M.; Gleizes, A.; Philoche-Levisalles,
M.; Kahn, O. Inorg. Chem. 1984, 23, 3808. (d) Julve, M.; Faus, J.; Verdaguer,
M.; Gleizes, A. J. Am. Chem. Soc. 1984, 106, 8306. (e) Bencini, A.; Fabretti,
A. C.; Zanchini, C.; Zannini, P. Inorg. Chem. 1987, 26, 1445. (f) Soto, L.;
ꢀ
´
a, J.; Escriva, E.; Legros, J.-P.; Tuchagues, J.-P.; Dahan, F.; Fuertes,
Garcı
A. Inorg. Chem. 1989, 28, 3378. (g) Castro, I.; Julve, M.; Munoz, M. C.; Dı
W.; Solans, X. Inorg. Chim. Acta 1991, 179, 59. (h) Soto-Tuero, L.; Garcı
~
´
az,
a-
´
ꢀ
ꢀ
ꢀ
Lozano, L.; Escriva-Molto, E.; Beneto-Borja, M.; Dahan, F.; Tuchagues, J.-
P.; Legros, J.-P. J. Chem. Soc., Dalton Trans. 1991, 2619. (i) Gleizes, A.;
Julve, M.; Verdaguer, M.; Real, J. A.; Faus, J.; Solans, X. J. Chem. Soc.,
Dalton Trans. 1992, 3209. (j) Glerup, J.; Goodson, P. A.; Hodgson, D. J.;
Michelsen, K. Inorg. Chem. 1995, 34, 6255. (k) Vicente, R.; Escuer, A.;
´
Ferretjans, J.; Stoeckli-Evans, H.; Solans, X.; Font-Bardıa, M. J. Chem.
The temperature dependence of the χMT product for 2
[χM is the magnetic susceptibility per two copper(II) ions]
is shown in Figure 8. χMT at room temperature is equal to
0.82 cm3 mol-1 K, a value which is as expected for two
uncoupled copper(II) ions (0.81 cm3 mol-1 K with g =
2.08). Upon cooling, χMT smoothly increases to reach a
value of 0.864 cm3 mol-1 K at 1.9 K. This plot is as
expected for a weak overall ferromagnetic interaction.
ꢀ
Soc., Dalton Trans. 1997, 167. (l) Castillo, O.; Muga, I.; Luque, A.; Gutierez-
ꢀ
Zorrilla, J. M.; Sertucha, J.; Vitoria, P.; Roman, P. Polyhedron 1999, 18,
1235. (m) Du, M.; Guo, Y.-M.; Chen, S.-T.; Bu, X.-H.; Ribas, J. Inorg. Chim.
Acta 2003, 346, 207. (n) Youngme, S.; van Albada, G. A.; Chyaichit, N.;
Gunnasoot, P.; Kongsaeree, P.; Multikainen, I.; Roubeau, O.; Reedijk, J.;
Turpeinen, U. Inorg. Chim. Acta 2003, 353, 119. (o) Carranza, J.; Grove, H.;
Sletten, J.; Lloret, F.; Julve, M.; Kruger, P. E.; Eller, C.; Rillema, D. P. Eur.
J. Inorg. Chem. 2004, 4836. (p) Manna, S. H.; Ribas, J.; Zangrando, E.;
Chaudhuri, N. R. Inorg. Chim. Acta 2007, 360, 2589.

Article
Inorganic Chemistry, Vol. 48, No. 14, 2009 6639
Although there are two possible exchange pathways in 2,
the tris-bidentate dipyatriz and the bidentate/monoden-
tate (outer) oxalate, the former one can be discarded
having in mind the very weak antiferromagnetic coupling
which is observed in 1. Then, assuming that the oxalate
bridge is responsible for the ferromagnetic interaction
occurring in 2, we have analyzed the magnetic data of this
compound by means of the expression for two magneti-
cally interacting spin doublets [eqs (3)-(5)]42
χM ¼ ðχ þ 2χ^ Þ=3
ð3Þ
2
2
χ ¼ 2Ng β =kTf½expð -D=3kTÞꢁ=½expð2D=3kT þ
2expð -D=3kTÞ þ expð -J=kTÞꢁg
ð4Þ
Figure 9. χMT (4) and χM (O) versus T plots for complex 3. The solid
line is the best-fit curve for three dicopper(II) units (see text).
χ^ ¼ 2Ng^ 2β2=Df½expð2D=3kT -expð -D=3kTÞꢁ=
½expð2D=3kT þ 2expð -D=3kTÞ þ expð -J=kTÞꢁg ð5Þ
which was derived through the Hamitonian [eq 6]
interactions were reported for the copper(II) compounds
of formula [Cu(2-MeIm)(ox)] (2-MeIm = 2-methylimi-
dazole, J = +0.63 cm-1 37b
and [Cu(en)2][Cu(ox)2]
)
(en = ethylenediamine, J = -3.0 cm-1),37c where the
oxalate exhibits the same coordination mode observed
in 2.
∧
∧
∧
∧
∧
∧
∧
H ¼ -JSA SB þ SADSB þ βHðgASA þ gBSBÞ ð6Þ
3
The temperature dependence of the χMT product for 3
[χM is the magnetic susceptibility per six copper(II) ions] is
shown in Figure 9. χMT at room temperature is equal to
1.05 cm3 mol-1 K, a value which is much smaller than that
expected for six uncoupled copper(II) ions (ca. 2.43 cm3
mol-1 K with g=2.08). Upon cooling, this value de-
creases very quickly, and it practically vanishes at
50 K. This plot is indicative of a strong antiferromagnetic
coupling leading to a low-lying singlet spin state. The
where J is the magnetic coupling, D is the axial zero-field
splitting within the triplet state, and g = g^ = g is the
ꢀ
Lande factor (which is assumed to be isotropic for simpli-
city). Least-squares fitting leads to the following values:
J=+0.45(2) cm-1, g = 2.09(1), and |D|= 1.0(2) cm-1. As
shown in Figure 8, the calculated curve reproduces well the
magnetic data in the whole temperature range investigated.
The lack local anisotropy of the copper(II) ion and the large
copper-copper separation through the oxalato bridge
(ca. 5.6 A) cannot account for the relatively large value of
D which has to be considered as the upper limit given that
the antiferromagnetic interdimer interactions were not
considered.
The weak magnitude of the magnetic coupling between
the copper(II) ions across the oxalate bridge (Figure 3b)
can be understood by considering the symmetry and
relative orientation of the magnetic orbitals involved.
The unpaired electron on each copper(II) ion in 2 is of
the dx2-y2 type with the x and y axis being roughly defined
by the equatorial bonds to the copper atom. As the
oxalate bridge occupy two equatorial positions at
Cu(1) [O(1) and O(2) atoms] and an axial one at Cu(2d)
[O(4)], it is clear that the spin density at the axial O(4)
atom has to be very weak. Consequently, the overlap
between the adjacent magnetic orbitals through this out-
of-plane pathway has to be very small and a very weak
antiferro- or even ferromagnetic coupling is predicted.43
The weak ferromagnetic coupling observed in 2 is most
likely due to the accidental orthogonality between the
magnetic orbitals, a situation which depends on subtle
structural parameters such as the axial copper to oxalate-
oxygen bond length, angle at the apical oxygen,
and dihedral angle between the mean basal planes. In
that respect, either weak ferro- or antiferromagnetic
χ
M curve (see inset of Figure 9) is also typical for a strong
antiferromagnetic coupling because of the occurrence of a
rounded maximum about 300 K, the increase of the
magnetic susceptibility χM in the low temperature range
being due to a small amount of mononuclear copper(II)
impurities.
Given the poor ability of the tris-bidentate dipatryz
ligand to mediate magnetic interactions as shown by
compound 1 (see above) and the well documented ability
of the oxalate group to transmit strong antiferromagnetic
interactions between copper(II) ions when adopting the
symmetrical bis-bidentate bridging mode,41b-41d,41f,41h-41p
the magnetic behavior of compound 3 would correspond to
that of three oxalato-bridged dicopper(II) units with a
strong antiferromagnetic coupling within each unit. As-
suming the magnetic coupling for the three units is iden-
tical, the magnetic data of 3 [per diccoper(II) unit] have
been analyzed through a Bleaney-Bowers express∧ion ∧for
∧
two spin doublets (the Hamiltonian being H = -J S1 S2).
3
The best fit led to the following values: J = -390(2) cm -1
,
g = 2.09(1), and F = 0.3% (F is the mass proportion
of paramagnetic impurity).41c As shown in Figure 9, the
calculated curve reproduces well the magnetic data in the
whole temperature range. The strong antiferromagnetic
coupling observed in 3 is in the upper range of those reported
in other oxalato-bridged dicopper(II) complexes where the
bis-bidentate oxalate links equatorial positions of the two
copper(II) ions (see Table 5). The σ in-plane exchange path-
way of the oxalate bridge which is responsible for this strong
(42) Kahn O. Molecular Magnetism; VCH: Weinheim, 1993; p 136.
(43) Cervera, B.; Ruiz, R.; Lloret, F.; Julve, M.; Cano, J.; Faus, J.; Bois,
C.; Mrozinski, J. J. Chem. Soc., Dalton Trans 1997, 395.

6640 Inorganic Chemistry, Vol. 48, No. 14, 2009
Yuste et al.
Table 5. Selected Magneto-Structural Data for Oxalate-Bridged Dicopper(II) Complexes of the Type [(NN)Cu(μ-ox)Cu(NN)]Xn Exhibiting the σ In-Plane Exchange
Pathway
NNa
X
donor set
dihedral angleb
hCu
0.27
0.24
0.16
0.18
0.16
0.11
0.19
0.08
dCu
Je
ref.
41e
c
d
Cu
3 3 3
phen
NO3
NO3
NO3
ClO4
BF4
NO3
ClO4
NO3
ClO4
ClO4
PF6
N2O2/O0
N2O2/Ow
N2O2/OwO0
N2O2/OwO0
N2O2/OwF
N2O2/OwO0
N2O2/N0
N2O2/O0O00
N2O2/Ow
N2O2/OwO0
N2O2/Ow
N2O2/OwO0
N2O2/OwO0
N2O2/OwCl
N2O2/OwO0
16.9
22.7
3.2
12.0
10.4
4.6
14.5
7.0
8.4
3.9
5.158(1)
5.144(1)
5.154(1)
5.150(1)
5.144(1)
5.143
-330
-288
-386
-376
-378
-382
-382
-305
-385
-300
-402
-284
-312
-345
-390
phen
bipy
bipy
bipy
bipy
dpyam
dpyam
tmen
deen
mpym
mpym
dpp
41p
41d,41i
41i
41i
41l
41m
41n
41b,41c
41k
41f
41h
41o
5.194
5.220(2)
5.147/5.167
0.18
f
f
13.9
0.24
0.12/0.07
0.16
0.10/0.09
0.16h
5.175
5.217
f
NO3
NO3
Cl
7.3
4.9
5.171(1)
5.1345(16)
5.132i
bpz
dipyatriz
41o
this work
NO3
1.6/17.5g
a Abbreviations: phen = 1,10-phenanthroline; bipy = 2,20-bipyridine; dpyam = 2,20-diyridylamine; tmen = N,N,N0,N0-tetramethylethylenediamine;
deen = N,N-diethylethane-1,2-diamine; mpym = meripirizole; dpp = 2,3-bis(2-pyridyl)pyrazine, bpz = 2,20bipyrazine; dipyatriz = 2,4,6-tris
(dipyridylamine)-1,3,5-triazine. b Dihedral angle (deg) between the mean oxalate and equatorial planes. c Out-of-equatorial plane displacement (A) of
the copper atom. d Copper-copper distance through the oxalate bridge (A). e Magnetic coupling (cm-1). f Value not reported. g Minimum and maximum
values. h Value for Cu(4) (the other five copper atoms remaining practically in their respective equatorial planes). i Average value.
magnetic coupling in this family of complexes and the
influence that the structural factors exert on J has been
subject of several theoretical studies some years ago,44-47
and further details are available therein for the interested
readers.
resulting when dipyatriz acts as a tris-bidentate ligand
is particularly aesthetic and appealing. In such a case, pre-
vious reports have shown the occurrence discrete
tri-20f,21,22 and tetranuclear20b,20e,20f species, as well as one-
dimensional compounds.20a,20c,21a Interestingly, the electron
deficient triazine ring of the dipyatriz ligand in its coordina-
tion compounds can be involved in anion-π and π-π
interactions that regulate the self-assembly of the anion-
triazine-triazine complexes. These supramolecular interac-
tions, the variety of coordination modes, and the luminescent
character of dipyatriz, as well as the possibility it offers as a
bridge to mediate elecyronic effects, enhance the interest in
the dipyatriz-containing metal complexes as potential multi-
functional materials. Finally, the great number and different
topologies and charge of the potential polyatomic bridges to
be used as coligands toward the highly versatile [Mx(dipya-
triz)y]xm+ unit opens new perspectives concerning the design
of multifunctional metallo-supramolecular assemblies.
Conclusions
In the present work, we have focused on three polynuclear
dipyatriz-containing copper(II) complexes (compounds 1-3)
from a magneto-structural point of view. Complex 1 is a
trinuclear species (1) having the [Cu3(dipyatriz)2]6+ core with
a weak intramolecular antiferromagnetic interaction. Re-
markably, the triazine rings of this unit exhibit a practically
eclipsed conformation, and they act as anion (perchlorate)
hosts. In the presence of oxalate as coligand, a layered
compound (2) and a unprecedented cage-like complex (3)
resulted depending on the preparative conditions [slow diffu-
sion of the aqueous solutions of the reactants at room
temperature (2) and hydrothermal conditions (3)]. Both
structures have in common the presence of the tris-bidentate
dipytriz ligand leading to tetra- [Cu4(dipyatriz)2]8+ (2) and
trinuclear [Cu3(dipyatriz)]6+ (3) units which are interlinked
through bidentate/monodentate (2) and bis-bidentate (3)
oxalate groups. Weak ferro- (2) and strong antiferromagnetic
(3) interactions occur between the copper(II) ions across the
oxalate bridges. The triangular array of the metal ions
Acknowledgment. Funding of this work is provided
~
by the Ministerio Espanol de Ciencia e Innovacion
through projects CTQ2007-61690, MAT2007-60660 and
ꢀ
ꢀ
´
“Factorıa de Crystalizacion” (Consolider-Ingenio2010,
CSD2006-00015). Two of the authors (C.Y. and L.C.-D.)
~
are grateful to the Ministerio Espanol de Ciencia
ꢀ
ꢀ
e Innovacion (C.Y.) and the Gobierno Autonomo de
Canarias (L.C.-D.) for predoctoral fellowships.
(44) Charlot, M. F.; Verdaguer, M.; Journaux, Y.; de Loth, P.; Daudey, J.
P. Inorg. Chem. 1984, 23, 3802.
(45) Alvarez, S.; Julve, M.; Verdaguer, M. Inorg. Chem. 1990, 29, 4500.
Supporting Information Available: Further details are given
in Figure S1, and crystallographic information as a CIF file.
This material is available free of charge via the Internet at
http://pubs.acs.org.
ꢀ
ꢀ
(46) Roman, P.; Guzman-Miralles, C.; Luque, A.; Beitia, J. L.; Cano, J.;
Lloret, F.; Julve, M.; Alvarez, S. Inorg. Chem. 1996, 35, 3741.
(47) Cano, J.; Alemany, P.; Alvarez, S.; Verdaguer, M; Ruiz, E. Chem.;
Eur. J. 1998, 4, 476.