Directed supramolecular assembly of infinite 1-D M(II)-containing chains (M = Cu, Co, Ni) using structurally bifunctional ligands

Article abstract of DOI:10.1021/ic048405y

The directed assembly of six different M(II) complexes (M = Cu, Co, and Ni) into infinite chains has been achieved by combining anionic chelating ligands (for controlling the coordination geometry) with bifunctional ligands containing a metal-coordinating pyridyl moiety and a self-complementary hydrogen-bonding moiety. Six crystal structures are presented, and in each case, the chelating acac ligand occupies the four equatorial coordination sites leaving room for the bifunctional ligand to coordinate in the axial positions. The supramolecular chemistry, which organizes the coordination complexes into the desired infinite 1-D chains, is driven by a combination of N-H...N and N-H...O hydrogen bonds.

Full text of DOI:10.1021/ic048405y

Inorg. Chem. 2005, 44, 4983−4991
Directed Supramolecular Assembly of Infinite 1-D M(II)-Containing
Chains (M Cu, Co, Ni) Using Structurally Bifunctional Ligands
)
Christer B. Aakero1y,* Nate Schultheiss, and John Desper
Department of Chemistry, Kansas State UniVersity, Manhattan, Kansas 66506
Received November 12, 2004
The directed assembly of six different M(II) complexes (M
) Cu, Co, and Ni) into infinite chains has been achieved
by combining anionic chelating ligands (for controlling the coordination geometry) with bifunctional ligands containing
a metal-coordinating pyridyl moiety and a self-complementary hydrogen-bonding moiety. Six crystal structures are
presented, and in each case, the chelating acac ligand occupies the four equatorial coordination sites leaving room
for the bifunctional ligand to coordinate in the axial positions. The supramolecular chemistry, which organizes the
coordination complexes into the desired infinite 1-D chains, is driven by a combination of N
hydrogen bonds.
−H‚‚‚N and N−H‚‚‚O
Introduction
extended metal-containing motifs where the assembly and
organization of neighboring complex ions is driven by
weaker noncovalent interactions such as hydrogen bonds,
π-π interactions, etc.8 Since the physical properties of any
solid are strongly influenced by the communication and
interactions between molecules or complex ions, it is
important, from the point of view of tuning the properties,
to be able to alter specific metrics (e.g. distance between
metal ions) without inducing dramatic changes to the overall
crystal structure. Thus, the design of versatile bifunctional
ligands that are capable of coordinating to a metal ion while
providing the means for organizing such complex ions into
extended networks in a predictable manner is an important
aspect of current structural inorganic chemistry.
The directed assembly of coordination complexes into
discrete entities or extended networks with predictable
connectivity and dimensionality remains a particularly chal-
lenging task.1 However, using assembly strategies based upon
coordinate-covalent bonds, a multitude of metal ions in a
variety of oxidation states and with different coordination
environments have been incorporated into coordination
polymers2 or metallacycles3 that may become useful as
catalysts4 or in magnetic,5 optical,6 or electronic7 devices.
Considerably less attention has been focused on producing
* Author to whom correspondence should be addressed. E-mail: aakeroy@
ksu.edu.
(1) Braga, D.; Desiraju, G. R.; Miller, J. S.; Orpen, A. J.; Price, S. L.
CrystEngComm 2002, 500-509. (b) Tashiro, S.; Tominaga, M.;
Kusukawa, T.; Kawano, M.; Sakamoto, S.; Yamaguchi, K.; Fujita,
M. Angew. Chem., Int. Ed. 2003, 42, 3267-3270. (c) Natarajan, R.;
Savitha, G.; Moorthy, J. N. Cryst. Growth Des. 2004, ASAP.
(2) (a) Berry, J. F.; Cotton, F. A.; Murillo, C. A. Inorg. Chim. Acta 2004,
357, 3847-3853. (b) Berry, J. F.; Cotton, F. A.; Fewox, C. S.; Lu,
T.; Murillo, C. A.; Wang, X. Dalton Trans. 2004, 15, 2297-2302.
(c) McManus, G. J.; Wang, Z.; Zaworotko, M. J. Cryst. Growth Des.
2004, 4, 11-13.
(3) (a) Chatterjee, B.; Noveron, J. C.; Resendiz, M.; Liu, J.; Yamamoto,
T.; Parker, D.; Cinke, M.; Nguyen, C. V.; Arif, A. M.; Stang, P. J. J.
Am. Chem. Soc. 2004, 126, 10645-10656. (b) Mukherjee, P. S.; Das,
N.; Kryschenko, Y. K.; Arif, A. M.; Stang, P. J. J. Am. Chem. Soc.
2004, 126, 2464-2473. (c) Berry, J. F.; Cotton, F. A.; Murillo, C. A.
Inorg. Chem. Acta 2004, 357, 3847-3853.
(4) (a) Walker, S. D.; Barder, T. E.; Martinelli, J. R.; Buchwald, S. L.
Angew. Chem., Int. Ed. 2004, 43, 1871-1876. (b) Strieter, E. R.;
Blackmond, D. G.; Buchwald, S. L. J. Am. Chem. Soc. 2003, 125,
13978-13980. (c) Ohmori, O.; Fujita, M. Chem. Commun. 2004, 14,
1586-1587.
(5) (a) Kahn, O. Acc. Chem. Res. 2000, 33, 1-11. (b) Chapman, M. E.;
Ayyappan, P.; Foxman, B. M.; Yee, G. T.; Lin, W. Cryst. Growth
Des. 2001, 2, 159-163. (c) Berry, J. F.; Cotton, F. A.; Lei, P.; Murillo,
C. A. Inorg. Chem. 2003, 42, 377-382.
We are specifically interested in developing reliable and
versatile supramolecular routes for the directed assembly of
metal ions into infinite 1-D chains to gain some control over
metal-metal distances within extended chains. To reach this
specific supramolecular goal it is important that the synthetic
(6) (a) Cariati, F.; Caruso, U.; Centore, R.; Marcolli, W.; Maria, A. D.;
Panunzi, B.; Roviello, A.; Tuzi, A. Inorg. Chem. 2002, 41, 6597-
6603. (b) Noveron, J. C.; Arif, A. M.; Stang, P. J. Chem. Mater. 2003,
15, 372-374. (c) Hou, H.; Song, Y.; Xu, H.; Wei, Y.; Fan, Y.; Zhu,
Y.; Li, L.; Du, C. Macromolecules 2003, 36, 999-1008.
(7) (a) Laitar, D. S.; Mathison, C. J. N.; Davis, W. M.; Sadighi, J. P.
Inorg. Chem. 2003, 42, 7354-7356. (b) Gumienna-Kontecka, E.; Rio,
Y.; Bourgogne, C.; Elhabiri, M.; Louis, R.; Albrecht-Gary, A.-M.;
Nierengarten, J.-F. Inorg. Chem. 2004, 43, 3200-3209.
(8) (a) Aakero¨y, C. B.; Beatty, A. M.; Lorimer, K. R. J. Chem. Soc., Dalton
Trans. 2000, 3869-3872. (b) Aakero¨y, C. B.; Beatty, A. M.; Leinen,
D. S.; Lorimer, K. R. J. Chem. Commun. 2000, 935-936. (c) Aakero¨y,
C. B.; Beatty, A. M.; Desper, J.; O’Shea, M.; Valde´s-Mart´ınez, J.
Dalton Trans. 2003, 3956-3962. (d) Bose, D.; Banerjee, J.; Rahaman,
S. H.; Mostafa, G.; Fun, H.-K.; Bailey Walsh, R. D.; Zaworotko, M.
J.; Ghosh, B. K. Polyhedron 2004, 23, 2045-2053.
10.1021/ic048405y CCC: $30.25
Published on Web 06/16/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 14, 2005 4983

Aakero1y et al.
Figure 1. Substituted acac complex with the arrows showing the two axial
coordination sites.
process is designed such that the number of potentially
structurally interfering components present, or introduced,
during the assembly process is kept to a minimum. In
essence, the reaction conditions need to be optimized in the
same way that reaction conditions for covalent synthesis are
selected for maximum yield.
Figure 2. Bifunctional ligands, 3-(2-amino-4-methoxypyrimidin-6-yl)-
pyridine, 1, 3-(2-amino-4-methylpyrimidin-6-yl)pyridine, 2, and 1-(2-amino-
4-methylpyrimidin-6-yl)-2-(3-methoxypyridin-5-yl)ethyne, 6.
structures that were obtained when they were allowed to react
with [(hfac)2CuII], [(DBM)2CoII], or [(DBM)2NiII] resulting
in infinite inorganic:organic networks. The structures are
analyzed and discussed in the context of the relevant
supramolecular design strategies and structural targets.
The yield (i.e. frequency of occurrence of a desired
structural motif) for a set of supramolecular reactions
involving coordination complexes can be improved by
ensuring that the coordination number/geometry for the metal
ion is strictly controlled and that the need for potentially
disruptive counterions is eliminated. With this in mind, we
decided to employ copper(II) 1,1,1,5,5,5-hexafluoro-2,4-
pentanedione [(hfac)2CuII], cobalt(II) 1,3-diphenyl-1,3-pro-
panedione [(DBM)2CoII], and nickel(II) 1,3-diphenyl-1,3-
propanedione [(DBM)2NiII] complexes as starting points for
this study.9 Complexes of this type are attractive due to the
fact that two dione anions occupy four equatorial sites around
the M(II) ion thereby producing an overall neutral metal-
containing building block. In addition, the two remaining
axial sites can be utilized for constructing extended linear
supramolecular architectures with an appropriate bifunctional
ligand, Figure 1.
A suitable bifunctional ligand would contain a chemical
functionality with the capability of binding to metal ions,
e.g. a pyridyl moiety, coupled with a functional group that
can interact with a neighboring ligand through self-
complementary hydrogen bonds. With these requirements in
mind, we decided to target the coordination chemistry of
three new ligands, 1, 2, and 6, Figure 2. 1 and 2 have slightly
different sterics and electronics in the vicinity of the
hydrogen-bonding functionality, whereas 6 incorporates an
ethynyl linker between the pyridyl and the aminopyrimidine
units. This ethynyl bridge elongates the ligand allowing for
even further extension between metal centers, and it is
important to establish if hydrogen-bond interactions can
maintain sufficient structural influence even to the point of
organizing larger coordination complexes into desired ex-
tended motifs.
Experimental Section
Synthesis. All chemicals were purchased from Aldrich and
used without further purification.
3-(2-Amino-4-methoxypyrimidin-6-yl)pyridine, 1. A
mixture of 2-amino-4-chloro-6-methoxypyrimidine (1.50 g,
9.38 mmol), 3-pyridylboronic acid10 (1.58 g, 10.33 mmol),
sodium carbonate (0.700 g, 6.6 mmol), and bis(triph-
enylphosphine)palladium(II) dichloride (180 mg, 0.256 mmol,
2.7 mol %) was added to a round-bottom flask. Acetonitrile
(35 mL) and water (35 mL) were added, and dinitrogen was
bubbled through the resultant mixture for 10 min. A
condenser was attached and the mixture heated at 75 °C
under a dinitrogen atmosphere. The reaction was monitored
by TLC and allowed to cool to room temperature on
completion (12 h). The solution was then diluted with 150
mL of ethyl acetate, washed with water (3 × 100 mL), and
then washed with saturated aqueous sodium chloride (2 ×
100 mL). The organic layer was separated and dried over
magnesium sulfate. The solvent was removed on a rotary
evaporator and the residue chromatographed on silica with
a hexanes/ethyl acetate mixture (1:1) as the eluant. The
product was isolated as a white solid. The product 1 was
then recrystallized from ethanol (200 proof) as colorless hair-
shaped crystals (1.44 g, 76%). Mp: 138-140 °C. 1H NMR
(δH; 400 MHz, CDCl3): 9.15 (d, J ) 2.4 Hz, 1H), 8.68 (dd,
J ) 4 Hz, J ) 1 Hz, 1H), 8.25 (dt, J ) 8.8 Hz, J ) 2.4 Hz,
1H), 7.38 (dd, J ) 8 Hz, J ) 4.8 Hz, 1H), 6.52 (s, 1H), 5.09
(s, 2H), 3.95 (s, 3H). 13C NMR (δC; 400 MHz, CDCl3):
171.61, 163.34, 163.21, 150.87, 148.38, 134.28, 133.15,
123.37, 94.387, 53.51. IR (KBr): 3451, 3354, 1582, 1362
cm-1.
In this paper we present the design and synthesis of three
new bifunctional ligands, Figure 2, and the six crystal
(9) (a) Panthou, F. L.; Luneau, D.; Musin, R.; O¨ hrstro¨m, L.; Grand, A.;
Turek, P.; Rey, P. Inorg. Chem. 1996, 35, 3484-3491. (b) Sano, Y.;
Tanaka, M.; Koga, N.; Matsuda, K.; Iwamura, H.; Rabu, P.; Drillon,
M. J. Am. Chem. Soc. 1997, 119, 8246-8252.
(10) Li, W.; Nelson, D. P.; Jensen, M. S.; Hoerrner, R. S.; Cai, D.; Larsen,
R. D.; Reider, P. J. J. Org. Chem. 2002, 67, 5394-5397.
4984 Inorganic Chemistry, Vol. 44, No. 14, 2005

Infinite 1-D M(II)-Containing Chains
3-(2-Amino-4-methylpyrimidin-6-yl)pyridine, 2. A simi-
lar procedure was followed for the methyl derivative. Column
chromatography was carried out with a hexanes/ethyl acetate
mixture (1:4) as the eluant and the product 2 recrystallized
from ethanol/chloroform as colorless block-shaped crystals
1H), 8.21 (d, J ) 5.2 Hz, 1H), 7.20 (dd, J ) 6 Hz, J ) 2.8,
1H), 3.81 (s, 3H), 0.24 (s, 9H).
3-Methoxy-5-ethynylpyridine, 5. A mixture of 3-meth-
oxy-5-((trimethylsilanyl)ethynyl)pyridine (4.25 g, 14.9 mmol)
and potassium carbonate (3.00 g, 21.7 mmol) was stirred in
methanol (80 mL) at room temperature for 1 h. The solution
was then diluted with ethyl ether (100 mL) and washed with
water (4 × 100 mL). The solvent was removed on a rotary
evaporator and the residue chromatographed on silica with
a n-pentane/ethyl acetate (10:1) as eluant. The product 5 was
1
yielding 74%. Mp: 192-194 °C. H NMR (δH; 400 MHz,
DMSO-d6): 9.18 (d, J ) 2 Hz, 1H), 8.63 (dd, J ) 4.8 Hz,
J ) 1.6 Hz, 1H), 8.33 (dt, J ) 8 Hz, J ) 1.6 Hz, 1H), 7.48
(dd, J ) 8 Hz, J ) 4.8 Hz, J ) 0.8 Hz, 1H), 7.09 (s, 1H),
6.65 (s, 2H), 2.28 (s, 3H). 13C NMR (δC; 400 MHz, DMSO-
d6): 168.52, 163.61, 161.43, 150.88, 147.89, 134.05, 132.66,
123.64, 105.41, 23.66. IR (KBr): 3324, 3154, 1576, 1345
cm-1.
1
isolated as a white solid (1.72 g, 87%). H NMR (δH; 200
MHz, CDCl3): 8.21 (d, J ) 2.8 Hz, 1H), 8.16 (d, J ) 4 Hz,
1H), 7.15 (dd, J ) 5.8 Hz, J ) 3 Hz, 1H), 3.72 (s, 3H), 3.17
(s, 1H).
3-Methoxy-5-bromopyridine, 3. A solution of sodium
methoxide in 25% methanol (6.83 mL, 31.6 mmol) was
combined with DMF (anhydrous 20 mL) under an inert N2
atmosphere in a round-bottom flask. 3,5-Dibromopyridine
(5.00 g, 21.1 mmol) was then added and stirred at 65 °C for
24 h. An additional 1 equiv of sodium methoxide in 25%
methanol (2.33 mL) was added after 4 h. The reaction was
monitored by TLC and allowed to cool to room temperature
upon completion. The reaction was then diluted with water
(50 mL) and extracted with diethyl ether (3 × 50 mL). The
organic extractions were combined and washed with brine
and then dried over magnesium sulfate. The solvent was
removed on a rotary evaporator and the residue chromato-
graphed on silica with a hexanes/ethyl acetate mixture (1:1)
as the eluant. The product, 5-bromo-3-methoxypyridine,11
was isolated as a yellow oil. Hexanes (20 mL) was then
added to the product, and the solution was placed in the
refrigerator. Colorless crystals precipitated from the mother
liquor, which were isolated and dried (2.82 g, 71%). Mp:
1-(2-Amino-4-methylpyrimidin-6-yl)-2-(3-methoxypy-
ridin-5-yl)ethyne, 6. 2-Amino-4-chloro-6-methylpyrimidine
(360 mg, 2.50 mmol), 3-methoxy-5-ethynylpyridine (400 mg,
3.01 mmol), copper(I) iodide (12.0 mg, 0.0710 mmol),
triphenylphosphine (50.0 mg, 0.191 mmol), and bis(triph-
enylphosphine)palladium(II) dichloride (50.0 mg, 0.071
mmol) were added to a round-bottom flask. Tetrahydrofuran
(12 mL) and triethylamine (12 mL) were added, and
dinitrogen was bubbled through the resultant mixture for 10
min. A condenser was attached and the mixture heated at
70 °C under a dinitrogen atmosphere. The reaction was
monitored by TLC and allowed to cool to room temperature
upon completion (48 h). The solution was then diluted with
50 mL of ethyl acetate, and the new solution was washed
with water (3 × 100 mL) and then washed with saturated
aqueous sodium chloride (1 × 100 mL). The organic layer
was separated and dried over magnesium sulfate. The solvent
was removed on a rotary evaporator and the residue
chromatographed on silica with a hexanes/ethyl acetate
mixture (1:1) as the eluant. The product 6 was isolated as a
light brown solid. The product was recrystallized from
chloroform producing colorless block-shaped crystals (426
1
27-29 °C. H NMR (δH; 400 MHz, CDCl3): 8.29 (d, J )
1.6 Hz, 1H), 8.25 (d, J ) 2.4 Hz, 1H), 7.36 (dd, J ) 2.6 Hz,
J ) 1.8 Hz, 1H), 3.86 (s, 3H). 13C NMR (δC; 400 MHz,
CDCl3): 155.83, 142.70, 136.01, 123.01, 120.18, 55.61.
3-Methoxy-5-((trimethylsilanyl)ethynyl)pyridine, 4.
3-Methoxy-5-bromopyridine (3.26 g, 17.31 mmol), (trim-
ethylsilyl)acetylene (2.05 g, 20.9 mmol), copper(I) iodide
(0.100 g, 0.590 mmol), triphenylphosphine (0.420 g, 1.60
mmol), and bis(triphenylphosphine)palladium(II) dichloride
(0.360 g, 0.510 mmol) were added to a round-bottom flask.
Tetrahydrofuran (75 mL) and triethylamine (75 mL) were
added, and dinitrogen was bubbled through the resultant
mixture for 10 min. A condenser was attached and the
mixture heated at 65 °C under a dinitrogen atmosphere. The
reaction was monitored by TLC and allowed to cool to room
temperature on completion (26 h). The solution was then
diluted with 100 mL of ethyl acetate, and the new solution
was washed with water (3 × 100 mL) and then washed with
saturated aqueous sodium chloride (1 × 100 mL). The
organic layer was separated and dried over magnesium
sulfate. The solvent was removed on a rotary evaporator and
the residue chromatographed on silica with n-pentane as the
eluant. The product 4 was isolated as a light yellow oil (4.25
g, 86%). 1H NMR (δH; 200 MHz, CDCl3): 8.27 (d, 1.6 Hz,
1
mg, 72%). Mp: 171-173 °C. H NMR (δH; 400 MHz,
CDCl3): 8.39 (d, J ) 2 Hz, 1H), 8.30 (d, J ) 2.8 Hz, 1H),
7.36 (dd, J ) 3 Hz, J ) 1.4 Hz, 1H), 6.70 (s, 1H), 5.43 (s,
2H), 3.85 (s, 3H), 2.35 (s, 3H). 13C NMR (δC; 400 MHz,
CDCl3): 168.88, 162.83, 154.99, 150.37, 144.92, 138.72,
122.61, 118.80, 113.48, 89.78, 87.66, 55.60, 23.81. IR
(KBr): 3326, 3171, 2229, 1652, 1558, 1423 cm-1.
2:1 Complex of 3-(2-Amino-4-methoxypyrimidin-6-yl)-
pyridine with Copper(II) 1,1,1,5,5,5-Hexafluoro-2,4-pen-
tanedione, 7. 3-(2-Amino-4-methoxypyrimidin-6-yl)pyridine
(13 mg, 0.060 mmol) and copper(II) 1,1,1,5,5,5-hexafluoro-
2,4-pentanedione (17 mg, 0.040 mmol) were added to a
screw cap vial along with chloroform (3 mL). The mixture
was heated gently until a clear homogeneous solution
resulted. Green prism-shaped crystals were harvested after
3 days (13 mg, 46%). Mp: 143-145 °C.
2:1 Complex of 3-(2-Amino-4-methoxypyrimidin-6-yl)-
pyridine with Cobalt(II) 1,3-Diphenyl-1,3-propanedione,
8. 3-(2-Amino-4-methoxypyrimidin-6-yl)pyridine (12 mg,
0.060 mmol) and cobalt(II) 1,3-diphenyl-1,3-propanedione
(16 mg, 0.030 mmol) were added to a screw cap vial along
with a mixture of 1,2-dichloroethane/chloroform (7:3 mL).
(11) Comins, D. L.; Killpack, M. O. J. Org. Chem. 1990, 55, 69-73.
Inorganic Chemistry, Vol. 44, No. 14, 2005 4985

Aakero1y et al.
Table 1. Crystallographic Data for Compounds 7-12
7
8
9
systematic name
bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)- bis(1,3-diphenyl-1,3-propanedionato)-
bis(1,1,1,5,5,5-hexafluoro-2,4-pentane-
bis[3-(2-amino-6-methoxypyrimidin-4-yl)-
bis[3-(2-amino-6-methoxypyrimidin-4-yl)- dionato)-bis[3-(2-amino-6-methyl-
pyridyl]copper(II)-2-chloroform
pyridyl]cobalt(II)
pyrimidin-4-yl)-pyridine]copper(II)-
1,2-di-chloroethane
(C5HF6O2)2(C10H10N4)2Cu·C2H4Cl2
C32H26Cl2CuF12N8O4
949.05
formula moiety
empirical formula
Mr
color, habit
space group, Z
a, Å
(C5HF6O2)2(C10H10N4O)2Cu·2CHCl3
C32H24Cl6CuF12N8O6
1120.83
(C15H11O2)2(C10H10N4O)2Co
C50H42CoN8O6
909.85
green prism
P1h, 2
yellow prism
P1h, 1
blue-green block
P1h, 1
10.4149(6)
9.3368(7)
10.3686(8)
11.0609(8)
85.536(2)
79.677(2)
83.026(2)
1043.95(14)
1.447
8.2843(4)
b, Å
c, Å
12.1682(7)
10.8750(5)
11.7573(6)
113.0810(10)
94.4120(10)
103.8330(10)
928.75(8)
18.2488(10)
105.6980(10)
105.8970(10)
93.1160(10)
2120.6(2)
1.755
100(2)
R, deg
â, deg
γ, deg
V, Å3
density, g/cm3
temp, K
1.697
100(2)
100(2)
X-ray wavelength, Å 0.710 73
0.710 73
0.475
1.87
30.00
0.710 73
0.843
2.13
30.03
µ, mm-1
1.000
1.76
30.00
θ
min, deg
max, deg
θ
reflcns
collcd
24 652
12 133
9791
12 145
5980
5233
10 734
5322
4874
indpndnt
obsd
threshold expression >2σ(I)
>2σ(I)
0.0462
0.1121
0.79
>2σ(I)
0.0376
0.1077
0.816
1.6
R1(obsd)
wR2(all)
Tmin
0.0459
0.1263
0.834
2.57
Rmerge, %
2.28
10
11
12
systematic name
bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)- bis(1,3-diphenyl-1,3-propanedionato)-
bis(1,3-diphenyl-1,3-propanedionato)-
bis[1-(2-amino-4-methylpyrimidin-
[1-(2-amino-4-methylpyrimidin-6-yl)-2-
(3-methoxypyridin-5-yl)ethyne]copper(II)
bis[1-(2-amino-4-methylpyrimidin-6-yl)-
2-(3-methoxypyridin-5-yl)ethyne]cobalt(II) 6-yl)-2-(3-methoxypyridin-5-yl)-
ethyne]nickel(II)
formula moiety
empirical formula
Mr
color, habit
space group, Z
a, Å
(C5HF6O2)2(C13H12N4O)Cu
C23H14CuF12N4O5
717.92
green block
P1h, 2
9.6243(11)
10.4481(12)
13.8822(15)
85.905(2)
86.300(2)
74.690(2)
1341.4(3)
1.777
(C13H12N4O)2(C15H11O2)2 Co
C56H46CoN8O6
985.94
orange block
P1h, 1
10.5076(5)
10.7568(6)
11.9544(6)
68.9160(10)
82.6200(10)
69.1900(10)
1178.48(10)
1.389
(C15H11O2)2(C13H12N4O)2Ni
C56H46N8NiO6
985.72
green plate
P1h, 1
10.4666(7)
10.6669(7)
11.9828(8)
68.678(4)
82.626(4)
69.230(3)
1165.27(13)
1.405
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
density, g/cm3
temp, K
100(2)
100(2)
173(2)
X-ray wavelength, Å 0.710 73
0.710 73
0.427
2.07
30.02
0.710 73
0.480
1.82
27.84
µ, mm-1
0.941
2.02
30.08
θ
min, deg
max, deg
θ
reflcns
collcd
15 237
7644
13 759
6762
6106
11 668
5170
3767
indpndnt
obsd
6241
threshold expression >2σ(I)
>2σ(I)
0.0429
0.1111
0.823
2.38
>2σ(I)
0.0570
0.1470
no abs corr
12.4
R1(obsd)
wR2(all)
Tmin
0.0467
0.1333
0.698
2.60
Rmerge, %
The mixture was heated gently until a clear homogeneous
solution resulted. Orange prism-shaped crystals formed after
1 day (19 mg, 70%). Mp: 219 °C (dec).
2:1 Complex of 3-(2-Amino-4-methylpyrimidin-6-yl)-
pyridine with Copper(II) 1,1,1,5,5,5-Hexafluoro-2,4-pen-
tanedione, 9. 3-(2-Amino-4-methylpyrimidin-6-yl)pyridine
(14 mg, 0.080 mmol) and copper(II) 1,1,1,5,5,5-hexafluoro-
2,4-pentanedione (18 mg, 0.040 mmol) were added to a
screw cap vial along with 1,2-dichloroethane (4 mL). The
mixture was heated gently until a clear homogeneous solution
resulted. Green block-shaped crystals were collected after 2
days (18 mg, 56%). Mp: 156-158 °C.
1:1 Complex of 1-(2-Amino-4-methylpyrimidin-6-yl)-
2-(3-methoxypyridin-5-yl)ethynewithCopper(II)1,1,1,5,5,5-
Hexafluoro-2,4-pentanedione, 10. 1-(2-Amino-4-methylpy-
rimidin-6-yl)-2-(3-methoxypyridin-5-yl)ethyne (9.0 mg, 0.040
4986 Inorganic Chemistry, Vol. 44, No. 14, 2005

Infinite 1-D M(II)-Containing Chains
Scheme 1
Table 2. Selected Hydrogen Bond Lengths, Å, and Angles, deg, for
Compounds 7-12
7
8
9
N(27)-H(27B)···O(34)#3 a 0.88
N(57)-H(57B)···O(62)#4 a 0.88
2.25
2.19
3.112(2)
3.040(2)
165.5
162.7
164(2)
N(52)-H(52A)···N(51)#2 b 0.86(2) 2.37(2) 3.203(2)
N(52)-H(52B)···O(13)#3 b 0.88(2) 2.16(2) 3.0337(18) 171(2)
N(22)-H(22A)···N(21)#3 c 0.80(3) 2.28(3) 3.0847(19) 174(2)
10 N(12)-H(12A)···N(11)#1 d 0.88
N(12)-H(12B)···O(42)#2 d 0.88
2.12
2.27
3.002(3)
3.044(2)
175.0
147.5
11 N(12)-H(12A)···O(31)#2 e 0.87(2) 2.18(2) 3.0365(16) 169.1(18)
N(12)-H(12B)···N(11)#3 e 0.81(2) 2.26(2) 3.0656(17) 173.1(18)
12 N(22)-H(22A)···O(31)
0.78(3) 2.29(3) 3.058(3)
168(3)
173(3)
N(22)-H(22B)···N(21)#2 f 0.82(3) 2.24(3) 3.058(3)
Scheme 2
a (#3) x, y - 1, z; (#4) x, y + 1, z. b (#2) -x + 1, -y, -z; (#3) x, y, z
- 1. c (#3) -x + 2, -y + 1, -z + 1. d (#1) -x + 1, -y, -z + 2; (#2) -x
+ 1, -y + 1, -z + 1. e (#2) -x + 1, -y + 2, -z + 1; (#3) -x, -y + 3,
-z. f (#2) -x, -y, -z′.
mmol) and copper(II) 1,1,1,5,5,5-hexafluoro-2,4-pentanedi-
one (10 mg, 0.020 mmol) were added to a screw cap vial
along with chloroform (2 mL). Green block-shaped crystals
were collected after 1 day (14 mg, 52%). Mp: 164-166 °C.
2:1 Complex of 1-(2-Amino-4-methylpyrimidin-6-yl)-
2-(3-methoxypyridin-5-yl)ethyne with Cobalt(II) 1,3-Di-
phenyl-1,3-propanedione, 11. 1-(2-Amino-4-methylpyrimidin-
6-yl)-2-(3-methoxypyridin-5-yl)ethyne (10 mg, 0.040 mmol)
and cobalt(II) 1,3-diphenyl-1,3-propanedione (11 mg, 0.020
mmol) were added to a screw cap vial along with chloroform
(2 mL). Orange block-shaped crystals were grown over a
period of 1 day (13 mg, 65%). Mp: 215 °C (dec).
2:1 Complex of 1-(2-Amino-4-methylpyrimidin-6-yl)-
2-(3-methoxypyridin-5-yl)ethyne with Nickel(II) 1,3-Di-
phenyl-1,3-propanedione, 12. 1-(2-Amino-4-methylpyrimidin-
6-yl)-2-(3-methoxypyridin-5-yl)ethyne (10 mg, 0.04 mmol)
and nickel(II) 1,3-diphenyl-1,3-propanedione (11 mg, 0.02
mmol) were added to a screw cap vial along with a mixture
of nitromethane/dichloromethane (2:2 mL). Green plate-
shaped crystals were grown over a period of 2 days (12 mg,
36%). Mp: 205 °C (dec).
X-ray Crystallography. Unless otherwise noted, X-ray
data were collected on a Bruker SMART APEX three-circle
CCD diffractometer using Mo KR radiation. Data were
collected using SMART.12 Initial cell constants were found
by small widely separated “matrix” runs. An entire hemi-
sphere of reciprocal space was collected. All compounds in
this study crystallized in the triclinic P1h space group. Scan
speed and scan width were chosen on the basis of scattering
power and peak rocking curves. Unless otherwise noted, data
were collected at -173 °C, using a 0.3° scan width.
Unit cell dimensions and the orientation matrix were
improved by least-squares refinement of reflections “thresh-
olded” from the entire dataset. Integration was performed
with SAINT,13 using this improved unit cell as a starting
point. Precise unit cell dimensions were calculated in SAINT
from the final merged dataset. Lorenz and polarization
corrections were applied, and data were corrected for
absorption. Data were reduced with SAINT.
The structure was solved and refined with SHELXTL.14
The structures were solved in all cases by direct methods
without incident. In general, hydrogen atoms were assigned
to idealized positions and were allowed to ride. Where possi-
ble, the coordinates of hydrogen-bonding hydrogen atoms
were allowed to refine. Heavy atoms, other than those of
the guests, were refined with anisotropic thermal parameters.
Crystallographic details for each individual structure follows.
7. Two disordered chloroform sites were identified in the
difference Fourier map. Two conformers were included for
each site, with occupancy for each site set to sum to 1, with
the minor conformer constrained to approximate the geom-
etry of the major conformer, and with thermal parameters
for similarly located atoms tied to each other. The lattice
contains two complexes, each located on a crystallographic
inversion center. Amine hydrogen atoms H27A, H27B,
H57A, and H57B were included at calculated positions.
Although the placement of these two species on special
positions suggested the possibility of a sublattice, the
chloroform molecules were not similarly positioned.
8. The cobalt complex sits on a crystallographic inversion
center. Coordinates for the amine hydrogen atoms, H52A
and H52B, were allowed to refine.
9. The asymmetric unit contains a copper complex, located
on an inversion center, and a disordered 1,2-dichloroethane
species. The latter species contained two conformers (in an
approximately 85:15 mixture), both of which straddled an
inversion center. The unique carbon on both species was
refined isotropically. For purposes of connectivity tables, two
chlorine atoms, sharing atomic coordinates and thermal
(12) SMART, v5.060; Bruker Analytical X-ray Systems: Madison, WI,
1997-1999.
(13) SAINT, v6.02; Bruker Analytical X-ray Systems: Madison, WI, 1997-
(14) SHELXTL, v5.10; Bruker Analytical X-ray Systems: Madison, WI,
1999.
1997.
Inorganic Chemistry, Vol. 44, No. 14, 2005 4987

Aakero1y et al.
bit of -CF3 disorder was modeled with two conformers (90:
10 ratio). Geometry of the minor species was constrained to
that of the major species, the isotropic thermal parameters
of the two carbons were tied, and a free variable was
employed to model isotropic thermal motion for the fluorine
atoms on the minor conformer. Amine hydrogen atoms H12A
and H12B were included in calculated positions.
11. The cobalt complex sits on a crystallographic inversion
center. Amine hydrogen atoms H12A and H12B were
allowed to refine.
12. Data were collected on a SMART 1000 CCD diffrac-
tometer at -100 °C, using a 0.2° scan width. The nickel
complex sits on a crystallographic inversion center. Amine
Figure 3. Labeled thermal ellipsoids (50% probability level) of the two
asymmetric complex ions in the crystal structure of 7. Two molecules of
chloroform are omitted for clarity.
Figure 4. Adjacent complex ions in 7 organized into an extended chain held together by head-to-tail N-H‚‚‚O hydrogen bonds.
hydrogen atoms H22A and H22B were allowed to refine.
Crystallographic data are presented in Table 1, and relevant
hydrogen-bond data are shown in Table 2.
Results
Ligands 1 and 2 were prepared in good yields via Pd-
catalyzed Suzuki-Miyaura cross-coupling reactions, Scheme
1. Ligand 6 was prepared in good yields by means of the
palladium-catalyzed Sonogashira coupling of 3-methoxy-5-
ethynylpyridine with 2-amino-4-chloro-6-methylpyrimidine,
Scheme 2. 3-Methoxy-5-ethynylpyridine was synthesized in
excellent yields by means of Sonogashira coupling conditions
of 3-methoxy-5-bromopyridine and (trimethylsilyl)acetylene
followed by base-promoted deprotection.
The crystal structure of 7 contains two crystallographically
unique complexes (A and B), Figure 3. The two py-pym
ligands 1 reside perpendicular to the [(hfac)2CuII] complex
resulting in an octahedral coordination geometry around the
Figure 5. Labeled thermal ellipsoids in the crystal structure of 8 drawn
at 50% probability level (hydrogen atoms, apart from -NH2, omitted for
clarity).
Figure 6. Infinite chain in the crystal structure of 8 produced from N-H‚‚‚O and N-H‚‚‚N hydrogen bonds. Acac phenyl rings have been omitted for
clarity.
parameters, were included in the atom list. Atomic coordi-
nates for the two amine hydrogen atoms, H22A and H22B,
were allowed to refine.
copper center. The ligands are coordinated through the
pyridyl nitrogen atoms with Cu-N distances of 2.0227(16)
and 2.0049(15) Å, respectively. Due to the close similarities
of the supramolecular assembly of A and B, only one will
10. The copper complex sits on a general position. A slight
4988 Inorganic Chemistry, Vol. 44, No. 14, 2005

Infinite 1-D M(II)-Containing Chains
described in detail. Neighboring complex ions are held
together in a head-to-tail motif by which the syn-amino
proton forms a N-H‚‚‚O hydrogen bond with an oxygen
atom from an adjacent acac complex, producing an infinite
ribbon, Figure 4. The anti-amino proton and the pyrimidine
nitrogen atoms are participating in extending the networks.
In addition, two molecules of chloroform are incorporated
into the crystal lattice.
The metal complex in the crystal structure of 8 is
composed of two py-pym ligands 1 bound at the axial
positions of the [(DBM)2CoII] complex, Figure 5. The Co-
(II) ion displays an octahedral coordination geometry with
a Co-N distance of 2.1514(14) Å. The extended network
exhibits the same connectivity as that of 7, in which head-
to-tail N-H‚‚‚O hydrogen bonds are formed between the
Figure 7. Numbered thermal ellipsoids in the crystal structure of 9 drawn
at 50% probability level. One molecule of 1,2-dichloroethane and the
hydrogen atoms (apart from -NH2) have been omitted for clarity.
Figure 8. Infinite ribbon held together by self-complementary N-H‚‚‚N aminopyrimidine interactions in the crystal structure of 9.
anti-amino proton and an oxygen atom from a neighboring
acac complex. Additionally this structure displays self-
complementary N-H‚‚‚N hydrogen bonds, between the syn-
amino proton and a pyrimidine nitrogen atom, Figure 6.
The metal complex in 9 is composed of two py-pym
ligands 2 bound to a [(hfac)2CuII] complex. The orientation
and arrangement of the py-pym ligands 2 with respect to
the [(hfac)2Cu(II)] complex are similar to those shown in
the structure of 7, where coordination to the axial positions
of the metal ion takes place via the pyridyl moieties thus
creating an octahedral metal environment with a Cu-N
distance of 2.0044(12) Å, Figure 7. Within this arrangement
the aminopyrimidine functionality is suitable for self-
complementary hydrogen bonds with neighboring complexes.
Thus the syn-amino protons form self-complementary
N-H‚‚‚N hydrogen bonds with pyrimidine nitrogen atoms
resulting in a one-dimensional infinite ribbon, Figure 8. The
Figure 9. Labeled thermal ellipsoids (drawn at 50% probability level) of
crystal structure 10 with the hydrogen atoms (apart from -NH2) omitted
for clarity.
Figure 10. Extended network in the crystal structure of 10 showing the N-H‚‚‚N and N-H‚‚‚O hydrogen bonds.
Inorganic Chemistry, Vol. 44, No. 14, 2005 4989

Aakero1y et al.
extended structures of 7 and 9 are possibly different due to
a subtle change of the substituents on the organic counterpart.
Ligand 1 has a methoxy substituent ortho to the pyrimidine
nitrogen atom sterically congesting that binding site, thus
blocking the interactions to the neighboring amino protons.
The second pyrimidine nitrogen atom and anti-amino proton
are not involved in extending the network. Furthermore a
solvent molecule of 1,2-dichloroethane is incorporated in the
crystal lattice, but disruption of the self-complementary
hydrogen bonds does not occur.
The crystal structure of 10 includes only one py-pym
ligand 6 coordinated to a [(hfac)2CuII] complex in the axial
position, Figure 9. Coordination occurs through the pyridyl
nitrogen atom of the ligand to the copper center with a Cu-N
distance of 2.2751(18) Å, resulting in a square pyramidal
metal coordination geometry. The ligand:metal complexes
form head-to-tail N-H‚‚‚O hydrogen bonded dimers through
Figure 11. Labeled thermal ellipsoids of structure 11 drawn at 50%
probability level with the hydrogen atoms (apart from -NH2) omitted for
clarity.
Figure 12. Extended network in the crystal structure of 11 with the phenyl rings omitted from the metal acac complex for clarity.
the anti-amino proton to the oxygen atom of an adjacent
metal acac complex. Further extension of the network is
fashioned by self-complementary N-H‚‚‚N hydrogen bonds
from the syn-amino proton to a nitrogen atom of the
pyrimidine ring, Figure 10. The second pyrimidine nitrogen
atom is aligned to coordinate at the axial position of a
neighboring acac complex, although the Cu-N distance is
approximately 2.70 Å.
The metal complex in 11 contains two symmetry-related
py-pym ligands 6 bound axially to a [(DBM)2CoII] complex
with a Co-N bond distances of 2.2083(11) Å creating an
octahedral cobalt coordination geometry, Figure 11. The
network forms an infinite sheet by self-complementary N-H‚
‚‚N hydrogen bonds from the syn-amino protons to a nitrogen
atom of the pyrimidine ring and by N-H‚‚‚O hydrogen
bonds from the anti-amino protons to an oxygen atom of
the adjacent acac complex, Figure 12.
Figure 13. Labeled thermal ellipsoids for the crystal structure of 12 drawn
at 50% probability level with the hydrogen atoms (apart from -NH2) omitted
for clarity.
Figure 14. Extended network in the crystal structure of 12 with the phenyl rings omitted from the metal acac complex for clarity.
4990 Inorganic Chemistry, Vol. 44, No. 14, 2005

Infinite 1-D M(II)-Containing Chains
Figure 15. Pictorial explanation of diverging vs converging structural motifs.
The crystal structure of 12 is isostructural with the crystal
structure of 11. Two py-pym ligands 6 are coordinate axially
to the [(DBM)2NiII] complex with Ni-N bond distances of
2.142(2) Å creating an octahedral coordination geometry
around the nickel center, Figure 13. The overall structure is
extended through self-complementary N-H‚‚‚N hydrogen
bonds from the syn-amino protons to a nitrogen atom of the
pyrimidine ring and by N-H‚‚‚O hydrogen bonds from the
anti-amino protons to an oxygen atom of an adjacent acac
complex, Figure 14.
placed the methoxy substituent with a less intrusive -CH3
group (resulting in ligand 2). The crystal structure determi-
nation of 9 shows that a relatively minor molecular modi-
fication was needed to achieve the desired supramolecular
assembly process; neighboring py-pym ligands are intercon-
nected in a linear manner through the intended N-H‚‚‚N/
N‚‚‚H-N motif, Figure 8.
Another way of minimizing steric crowding (that could
prevent or disrupt intended supramolecular assembly) would
be to increase the separation between the two different
binding sites on the bifunctional ligand. Consequently, an
ethynyl bridge was incorporated into 6 in an attempt to
facilitate access to the hydrogen-bonding site and this strategy
worked very well as exemplified by the crystal structure
determinations of 10-12. Despite the fact that the coordina-
tion chemistry is different, square-pyramidal vs octahedral,
respectively, both contain the self-complementary hydrogen
bonds between adjacent aminopyrimidine sites that act as
the principle driving forces for the supramolecular assembly.
This study provides an outline for how a supramolecular
strategy geared toward a very specific target can be refined
and developed through a systematic structural study. The
structural information provides direct feedback and thus
guides the covalent modifications of the ligands that are
required to optimize the supramolecular assembly process.
The result is a structurally bifunctional supramolecular
reagent, ligand 6, that produces the desired supramolecular
motif, infinite 1-D chains, in high yields. This study also
serves to underscore some of the similarities between the
development of noncovalent and covalent synthetic meth-
odologies. In each case, the driving force is a specific goal,
an individual molecule, or an assembly of molecules,
respectively. The efficiency of the synthesis can be improved
by systematically altering reaction conditions or by making
deliberate changes to the supramolecular reagent.
Discussion
The decision to employ chelating ligands to control the
coordination chemistry especially around the often unpredict-
able Cu(II) ion resulted in each case in complex ions with
well-defined coordination geometry due to two acetylonate
ligands bound in the equatorial positions. This configuration
provides an open approach along the axial positions, which
essentially creates a linear metal-containing building block,
the geometry of which can be extended into an infinite 1-D
assembly with the help of a suitable bifunctional ligand. The
pyridyl moiety of the ligands 1, 2, and 6 coordinates in each
case to the metal ion, which typically generates an octahedral
complex. The one exception is 10 where only one of the
two axial positions is occupied by a pyridyl moiety resulting
in a square-pyramidal Cu(II) geometry. The supramolecular
chemistry in 7 and 8 does not work exactly as intended. In
the former, the desired self-complementary N-H‚‚‚N/N‚‚‚
H-N motif does not form, and in the latter, it does appear
as intended but the interaction takes place on the side of the
ligand that gives rise to a converging instead of a diverging
motif, Figure 15.
The drawback with ligand 1, at this stage, seemed to be
that the methoxy substituent showed a propensity to orient
itself in such a way as to limit intermolecular access to N(2).
In fact, a search of the CSD showed that a methoxy
substituent ortho to a pyridine nitrogen atom is very likely
to reside coplanar with the ring and face the adjacent nitrogen
atom, which does limit its availability as a potential
hydrogen-bond acceptor.15 To improve opportunities for the
desired self-complementary N-H‚‚‚N interaction, we re-
Acknowledgment. Financial support from the NSF
(Grant CHE-0316479) and Kansas State University is grate-
fully acknowledged.
Supporting Information Available: X-ray crystallographic data
in CIF format and 1H and 13C NMR specta of ligands 1-3 (PDF).
This material is available free of charge via the Internet at
http://pubs.acs.org.
(15) A CSD search resulted in 30 crystal structures showing a methoxy
substituent ortho to the pyridine nitrogen. In all 30 structures the
methoxy substituent is bent toward the nitrogen atom.
IC048405Y
Inorganic Chemistry, Vol. 44, No. 14, 2005 4991