Assembly of heteroleptic copper complexes with silver salts: from discrete trinuclear complexes to infinite networks

Article abstract of DOI:10.1021/ic902057d

The use of heteroleptic copper complexes functionalized with two differentiated coordinating groups for the elaboration of heterometallic extended networks is presented. Two novel 5-phenyl-dipyrrin (dpm) ligands appended with an imidazole or a pyrazole fu

Full text of DOI:10.1021/ic902057d

Inorg. Chem. 2010, 49, 331–338 331
DOI: 10.1021/ic902057d
Assembly of Heteroleptic Copper Complexes with Silver Salts: From Discrete
Trinuclear Complexes to Infinite Networks
ꢀ
Dmitry Pogozhev, Stephane A. Baudron,* and Mir Wais Hosseini*
ꢀ
Laboratoire de Chimie de Coordination Organique, UMR CNRS 7140, Universite de Strasbourg, F-67000,
Strasbourg, France
Received October 16, 2009
The use of heteroleptic copper complexes functionalized with two differentiated coordinating groups for the elaboration
of heterometallic extended networks is presented. Two novel 5-phenyl-dipyrrin (dpm) ligands appended with an
imidazole or a pyrazole function, dpm-imid and dpm-pz, have been prepared and used as ligands for the synthesis of a
series of heteroleptic (acacR)Cu(dpm) complexes (acacH = acetylacetonate; acacCN = 3-cyanoacetylacetonate).
The X-ray crystal structures of these complexes revealed that, albeit no particular association mode is observed for the
acac capping ligand, one-dimensional networks are formed with the acacCN capping ligand. Whereas the imidazole
peripheral ligand is coordinated to the copper center of a neighboring complex in the structure of (acacCN)Cu(dpm-
imid), such an interaction is absent for the pyrazole appended derivative, (acacCN)Cu(dpm-pz), leading to an
association mode involving the peripheral nitrile group of the acacCN ligand. Upon reaction of the imidazole
functionalized complexes, (acac)Cu(dpm-imid) and (acacCN)Cu(dpm-imid), with silver salts, trinuclear species,
{[(acacR)Cu(dpm-imid)]2Ag}þ, are formed as a result of the coordination of the azole nitrogen atom of two copper
complexes to the silver ion. As expected, in the case of (acac)Cu(dpm-imid), these species do not self-assemble into
an extended network owing to the absence of a peripheral coordinating group. However, for the (acacCN)Cu(dpm-
imid) complex, the trinuclear species are equipped with peripheral nitrile groups, thus allowing the binding of metal
centers. Consequently, these species self-assemble into one-dimensional polymers with association modes varying
with the nature of the anion present in the silver salt.
Introduction
homo- and heterometallic architectures. To circumvent this
synthetic issue, a sequential strategy can be envisioned.2-8
Coordination polymers (CPs) have attracted considerable
interest over the past decade, as they hold promise in the
fields of gas storage and catalysis.1 While the vast majority of
these compounds are homometallic, the synthesis of their
heterometallic counterpart remains challenging. Indeed, a
one-pot synthetic approach can lead to a statistical mixture of
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*To whom correspondence should be addressed. Tel: 33 368851323. Fax:
33 368851325. E-mail: sbaudron@unistra.fr (S.A.B.), hosseini@unistra.fr
(M.W.H.).
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r
2009 American Chemical Society
Published on Web 12/02/2009
pubs.acs.org/IC

332 Inorganic Chemistry, Vol. 49, No. 1, 2010
Pogozhev et al.
capping ligand should allow the self-assembly by coordina-
tion processes of the heterometallic discrete complexes.
It is worth noting that at least two modes of self-assembly
can be foreseen for these species. The silver ion can feature
coordination numbers higher than 2 and is therefore capable
of interaction with the additional peripheral coordinating
group (Figure 1c). It has also been demonstrated that
(acac)Cu(dpm) complexes self-assemble upon coordination
of the peripheral group on the dpm to a metal center of
another complex leading to a penta-coordinated Cu ion.11 In
the case of discrete heterometallic complexes bearing periph-
eral coordinating sites, such a self-assembly mode should
also lead to extended architectures (Figure 1b). Recently,
several homoleptic complexes with the acacPy or acacCN
ligands (acacPy = 3-(4-pyridyl)acetylacetonate; acacCN =
3-cyanoacetylacetonate) have been prepared and used for the
elaboration of heterometallic CPs.5,6 Interestingly, no (acacCN)-
Cu(dpm) or (acacPy)Cu(dpm) complexes have, to our knowl-
edge, been reported. Such species would be suitable candidates
for the application of the sequential construction strategy
illustrated in Figure 1b and c. To illustrate this approach, we
report herein on the synthesis of (acacCN)Cu(dpm), with the
novel dipyrrins 5 and 6 (Scheme 1) bearing peripheral imidazole
and pyrazole groups, respectively, and the study of their self-
assembly as well as their reaction with silver salts to afford
heterometallic CPs. The imidazole and pyrazole groups have
been chosen for their known ability to form complexes with
silver salts.12,13
Figure 1. Coordination of an (acac)Cu(dpm) complex with silver ions,
leading to a trinuclear complex (a). With the nitrile appended
(acacCN)Cu(dpm) complexes, coordination polymers can be obtained
(b and c).
The latter relies on the use of ligands bearing differentiated
coordination sites, hence allowing the stepwise elaboration of
heterometallic architectures. Reaction of such a ligand with a
first metal center leads to the formation of a metal complex, or
metallatecton,9 bearing peripheral coordinating sites available
for ligation to another metal center. Among the many poten-
tial differentiated ligands, the dipyrrins, dpm,10 represent a
particularly interesting class of compounds. Indeed, their
rather easy synthesis and functionalization as well as the
monoanionic and chelating nature of their conjugate base
have made them appealing candidates. In particular, the 5-
aryl-dipyrrin derivatives have been successfully used for the
elaboration of extended heterometallic architectures based, for
the major part, on the association of homoleptic metallatec-
tons with silver salts.7,8 Only a few examples have reported the
elaboration of extended heterometallic systems based on
heteroleptic metallatectons incorporating a dpm.8 These ex-
amples involve a Ag-π interaction between the silver ion and
the pyrrolic system of the dpm. In the absence of such inter-
action, heteroleptic metallatectons such as (acac)Cu(dpm)8,11
or (salen)Co(dpm)8 complexes (acac = acetylacetonate, salen =
N,N0-bis(salicylidene)ethylenediamine) incorporating a dpm
bearing a coordinating site in the para position should only
lead to discrete heterometallic complexes upon reaction with
a second metal center, as illustrated in Figure 1a. Two
approaches can be considered to obtain extended systems
with such species. The first one consists of using a dpm ligand
bearing more than one peripheral coordinating site. An
example of such a unit may be obtained by functionalizing
both meta positions on the aryl moiety. The second strategy
relies on the use of the capping ligand itself for further
coordination. For example, when considering the association
of a (acac)Cu(dpm) heteroleptic complex with silver salts
(Figure 1b and c), introduction of a coordinating group on the
Experimental Section
Synthesis. The starting Cu(acacCN)2 complex was prepared
as described.14 Aldehydes 1 and 2 were synthesized following
a modified version of the reported procedure.15 Pyrrole
was purified over an alumina column before use. All other
reagents were obtained commercially and used without further
purification. 1H and 13C NMR spectra were recorded at 25 ꢀC
on a Bruker AV 300 (300 MHz) with the deuterated solvent as
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Article
Inorganic Chemistry, Vol. 49, No. 1, 2010 333
Scheme 1. Synthesis of the Dipyrrins 5 and 6 and the Heteroleptic Copper Complexes 7-10
the lock and residual solvent as the internal reference. NMR
chemical shifts and J values are given in parts per million and in
hertz, respectively.
for C18H16N4: C, 74.98; N, 19.43; H, 5.59. Found: C, 74.32; N,
19.46; H, 5.56.
Dipyrromethane 4. Several drops of TFA were added to a
solution of 2 (1.25 g, 6.98 mmol) in an excess of degassed pyrrole
(40 mL). The mixture was heated at 75 ꢀC for 24 h under
nitrogen and protected from light. A few drops of Et3N were
added to the mixture, and pyrrole was removed under vacuum.
The resulting residue was dissolved in CHCl3 (300 mL) and
washed with 0.1 M NaOH (3 ꢀ 150 mL). The organic extracts
were dried over MgSO4 and concentrated. The crude product
was purified by flash chromatography on SiO2 (CHCl3) and
then on Al2O3 (CHCl3/pentane: 1/1, Rf(CHCl3) = 0.17) to
afford 4 as a yellow solid (1.61 g, 76.9%). 1H NMR (300 MHz,
CDCl3): δ 8.00 (s, 2H), 7.89 (d, J = 2.4 Hz, 1H), 7.71 (d, J = 1.6
Hz, 1H), 7.65-7.60 (m, 2H), 7.31-7.27 (m, 2H), 6.72 (dd, J1 =
4.2, J2 = 2.8 Hz, 2H), 6.46 (t, J = 2.1 Hz, 1H), 6.17 (dd, J1 = 6.0
Hz, J2 = 2.6 Hz, 2H), 5.93 (m, 2H), 5.51 (s. 1H). 13C NMR (75
MHz, CDCl3): δ 141.1, 140.5, 139.1, 132.2, 129.4, 126.8, 119.5,
117.4, 108.6, 107.6, 107.4, 43.5. Anal. Calcd for C18H16N4: C,
74.98; N, 19.43; H, 5.59. Found: C, 74.64; N, 19.59; H 5.45.
Dipyrrin 5. A benzene solution (100 mL) of DDQ (2.75 g,
12.09 mmol) was added dropwise over a period of 30 min to a
THF solution (300 mL) of 3 (2.63 g, 11.52 mmol). Thin-layer
chromatography (TLC) analysis indicated complete consump-
tion of the starting material after stirring for 1 h. The solvent was
removed under vacuum, and the resulting residue was dissolved
in CHCl3 (300 mL) and purified by mixing with activated
carbon. The CHCl3 solution was separated by filtration, and
the crude product was purified by flash chromatography (SiO2,
EtOAc with addition of Et3N, Rf = 0.45) to afford 5 as a yellow
solid (1.6 g, 61.4%). 1H NMR (300 MHz, acetone-d6): δ 8.21 (s,
1H), 7.78 (dt, J1 = 8.52 Hz, J2 = 2.1 Hz, 2H), 7.76 (t, J = 1.4,
2H), 7.71 (t, J = 1.4, 1H), 7.65 (dt, J1 = 8.5 Hz, J2 = 2.1 Hz,
2H), 7.17 (t, J = 1.1 Hz, 1H), 6.60 (dd, J1 = 4.2, J2 = 1.3 2H),
6.44 (dd, J1 = 4.2, J2 = 1.3 2H). 13C NMR (75 MHz, CDCl3): δ
0.144.1, 140.8, 140.1, 137.7, 136.5, 135.5, 132.3, 130.8, 128.5,
121.5, 120.4, 118.1, 118.0, 117.6, 108.5, 107.4. UV-vis
(CH2Cl2), λmax (nm)/ε (mol-1 L cm-1): 228 (30 000), 323
(11 000), 434 (26 000). Anal. Calcd for C18H14N4: C, 75.51; N,
19.57; H, 4.93. Found: C, 75.52; N, 19.86; H, 5.21.
Aldehyde 1. A DMSO solution (60 mL) of CuI (0.21 g, 1.1
mmol) and L-histidine (0.34 g, 2.2 mmol) was stirred in a
preheated oil bath (100 ꢀC) under nitrogen for 30 min. Then,
4-bromobenzaldehyde (2 g, 1.11 mmol), imidazole (0.9 g, 1.32
mmol), and potassium carbonate (3.06 g, 2.22 mmol) were
added. After 36 h, the reaction mixture was washed with
aqueous NaHCO3 (750 mL), and the product was extracted in
chloroform (3 ꢀ 500 mL). Organic extracts were dried over
MgSO4 and concentrated. The crude product was purified by
chromatography (SiO2, EtOAc Rf = 0.37) to afford compound
1 as a white solid (0.76 g, 40%). 1H NMR (300 MHz, CDCl3): δ
10.04 (s, 1H), 8.01 (d, J = 8.7 Hz, 2H), 7,96 (s, 1H), 7.57 (d, J =
8.7 Hz, 2H), 7.37 (t, J = 1.4 Hz, 1H), 7.24 (t, J = 1.1 Hz, 1H).
13C NMR (75 MHz, CDCl3): δ 190.6, 141.7, 135.4, 135.0, 131.6,
131.4, 121.1, 117.7. Anal. Calcd for C10H8N2O: C, 69.76; N,
16.27; H, 4.68. Found: C, 69.72; N, 16.55; H, 4.87.
Aldehyde 2. A DMSO solution (60 mL) of CuI (0.5 g, 2.6
mmol) and L-histidine (0.34 g, 2.2 mmol) was stirred in a
preheated oil bath (100 ꢀC) under nitrogen for 30 min. Then,
4-bromobenzaldehyde (5 g, 27.70 mmol), pyrazole (2.26 g, 33.2
mmol), and K2CO3 (7.65 g, 55.43 mmol) were added. After 36 h,
the reaction mixture was washed with aqueous K2CO3 (1.5 L),
and the product was extracted in chloroform (4 ꢀ 500 mL).
Organic extracts were dried over dry MgSO4 and concentrated.
The crude product was purified by flash chromatography (SiO2,
CHCl3, Rf = 0.34) in CHCl3/pentane (1/1) and then in CHCl3 to
afford product 2 as a white solid (1.25 g, 26.4%). 1H NMR (300
MHz, CDCl3): δ 10.01 (s, 1H), 8.03 (d, J = 2.6 Hz, 1H),
8.00-7.96 (m, 2H), 7.91-7.87(m, 2H), 7.78 (d, J = 1.8 Hz,
1H), 6.53 (dd, J1 = 2.6, J2 = 1.8 Hz, 1H). 13C NMR (75 MHz,
CDCl3): δ 191.0, 144.3, 142.3, 134.1, 131.3, 127.0, 118.8, 108.9.
Anal. Calcd for C10H8N2O: C, 69.76; N, 16.27; H, 4.68. Found:
C, 68.95; N, 16.07; H, 4.41.
Dipyrromethane 3. Several drops of trifluoroacetic acid
(TFA) were added to a solution of 1 (2.5 g, 15.52 mmol) in an
excess of degassed pyrrole (40 mL). The mixture was heated at
75 ꢀC for 24 h under nitrogen and protected from light. Pyrrole
was then removed under vacuum, and the resulting residue was
dissolved in CHCl3 (300 mL) and washed with a 0.1 M NaOH
(3 ꢀ 150 mL) solution. The organic extracts were dried over
MgSO4 and concentrated. The crude product was purified by
flash chromatography (SiO2, CHCl3, Rf(EtOAc) = 0.53). The
resulting solid was washed with EtOAc to afford 3 as a beige
solid (2.63 g, 69.1%). 1H NMR (300 MHz, acetone-d6): δ 9.81
(s, 1H), 7.97 (s, 1H), 7.53 (dt, J1 = 2.3 Hz, J2 = 8.7 Hz, 2H), 7.34
(dt, J1 = 2.3 Hz, J2 = 8.7 Hz, 2H), 7.08 (t, J = 1.1 Hz, 1H), 6.70
(m, 2H), 6.00 (dd, J1 = 2.8 Hz, J2 = 5.8 Hz 2H), 5.76 (m, 2H),
5.52 (s, 1H). 13C NMR (75 MHz, DMSO-d6): δ 143.1, 135.9,
135.5, 133.2, 130.2, 129.8, 120.3, 118.5, 106.6, 43.3. Anal. Calcd
Dipyrrin 6. A benzene solution (100 mL) of DDQ (1.3 g, 5.73
mmol) was added dropwise over a period of 30 min to a THF
solution (200 mL) of 4 (1.5 g, 6.57 mmol). TLC analysis
indicated complete consumption of the starting material after
stirring for 12 h. Then, the solvent was removed under vacuum,
and the resulting residue was dissolved in CHCl3 (300 mL) and
purified by mixing with activated carbon. The organic solution
was separated by filtration, and the crude product was purified
by flash chromatography (SiO2, CHCl3/pentane: 1:1 with addition
of Et3N, Rf(CHCl3) = 0.66) to afford 6 as a yellow solid (1.2 g,
80.1%). 1H NMR (300 MHz, CDCl3): δ 8.01 (d, J=2.5 Hz, 2H),
7.82-7.77 (m, 3H), 7.66 (t, J=1.2 Hz, 2H), 7.62-7.57 (m, 2H),

334 Inorganic Chemistry, Vol. 49, No. 1, 2010
Pogozhev et al.
Table 1. Crystallographic Data for Compounds 3, 4, and 7-10 (C4H8O2)
3
3
4
7
8
9
10 (C4H8O2)
3
formula
fw
C18H16N4
288.35
C18H16N4
288.35
C23H20CuN4O2
447.99
C23H20CuN4O2
447.97
C24H19CuN5O2
472.98
C28H27CuN5O4
561.10
cryst syst
space group
triclinic
P1
monoclinic
P21/n
9.2680(3)
17.7535(5)
9.3468(3)
triclinic
P1
monoclinic
P21/c
14.0618(6)
17.0890(8)
8.8153(4)
monoclinic
P21/c
9.0755(3)
21.5983(6)
21.3201(6)
triclinic
P1
˚
a, A
8.5724(10)
9.7289(10)
10.4170(11)
62.616(4)
80.140(4)
83.840(4)
759.63(14)
2
173(2)
0.078
6871
3260 (0.0395)
0.0758
0.1639
8.6097(2)
10.6165(3)
11.0140(3)
82.1660(10)
87.9790(10)
88.6640(10)
996.54(5)
2
173(2)
1.124
12188
4525 (0.0249)
0.0339
0.0914
7.7529(2)
11.9322(2)
14.8002(4)
84.4710(10)
74.8250(10)
72.3840(10)
1259.23(5)
2
173(2)
0.913
26130
7313 (0.0261)
0.0353
0.0857
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
109.2900(10)
107.739(2)
94.0810(10)
3
˚
V, A
Z
T, K
1451.58(8)
4
173(2)
0.081
15557
3298 (0.0255)
0.0415
0.0947
0.0508
0.1016
1.067
2017.62(16)
4
173(2)
1.110
13780
4593 (0.0309)
0.0403
0.0975
0.0528
0.1163
1.100
4168.5(2)
8
173(2)
1.081
39063
9592 (0.0398)
0.0385
0.0998
0.0623
0.1161
1.082
μ, mm-1
reflns collected
ind. reflns (Rint
R1 (I > 2σ(I))a
)
wR2 (I > 2σ(I))a
R1 (all data)a
wR2 (all data)a
GOF
0.1038
0.1774
1.146
0.0392
0.0970
1.072
0.0409
0.0897
1.085
P
P
P
P
4 1/2
]
a R1 =
Fo| - |Fc
/
|Fo|; wR2 = [ w(Fo2 - Fc2)2/ wFo
.
6.64 (dd, J1 = 4.2 Hz, J2 = 1.0 Hz, 2H), 6.52 (t, J = 2.2 Hz, 1H),
6.42 (dd, J1 = 4.2 Hz, J2 = 1.5 Hz, 2H). 13C NMR (75 MHz,
CDCl3): δ 143.8, 141.5, 140.8, 140.8, 140.6, 135.4, 132.0, 128.6,
126.8, 118.2, 117.8, 108.1. UV-vis (CH2Cl2) λmax(nm)/ε(mol-1
L cm-1): 227 (18 000), 258 (22 000), 338 (12 000), 437 (22 000),
461 (18 000). HRMS (ESI), m/z: [M þ H]þ calcd for C18H15N4,
287.129; found, 287.126.
for 20 min, before removal of the solvent under a vacuum. The
crude product was purified by flash chromatography (SiO2,
CHCl3, Rf = 0.42). The resulting solid was washed with n-
pentane (150 mL) to afford 10 as dochroic red-green crystals (53
mg, 58.1%). Green-red single crystals were grown either by slow
diffusion of n-pentane into a dioxane solution of the complex or
by slow diffusion of n-pentane into a CHCl3 solution of the
complex. UV-vis (CH2Cl2), λmax(nm)/ε (mol-1 L cm-1): 229
(69 000), 263 (30 000), 349 (12 000), 478 (23 000), 489 (27 000). IR
(ATR, cm-1): νCN 2197. Anal. Calcd for C28H27N5CuO4: C,
59.94; N, 12.48; H, 4.85. Found: C, 60.12; N, 12.73; H, 5.01.
Heterometallic Complex 11. A solution of 7 (34.5 mg, 0.076
mmol) in THF (20 mL) was slowly diffused into a benzene
solution (15 mL) of AgSbF6 (13.3 mg, 0.038 mmol) in a tube
(16 ꢀ 1 cm) protected from light. After two weeks, dichroic green-
orange crystals were grown (39 mg, 73.0%). UV-vis, (THF)
[(acac)Cu(5)], 7. A solution of 5 (25 mg, 0.087 mmol) in THF
(8 mL) was mixed with a THF (8 mL) solution of Cu(acac)2 (22.9
mg, 0.087 mmol). The reaction mixture was stirred for 20 min.
The solvent was then removed under vacuum. The crude
product was purified by flash chromatography (SiO2, EtOAc,
Rf = 0.47). The resulting solid was washed with n-pentane (50
mL) to afford 7 as a red solid (25.5 mg, 65%). Dichroic red-green
crystals were grown by slow diffusion of ether into a CHCl3
solution of the complex. UV-vis, (CH2Cl2) λmax(nm)/ε (mol-1
L cm-1): 229 (34 000), 297 (15 000), 329 (11 000), 479 (25 000),
493 (32 000). Anal. Calcd for C23H20N4O2Cu: C, 61.67; N,
12.51; H, 4.50. Found: C, 61.19; N, 12.16; H, 4.51.
λ
max(nm)/ε (mol-1 L cm-1): 237 (65000), 301 (40000), 475
(57000), 494 (98000). Anal. Calcd for C58H52AgCu2F6N8O4Sb:
C, 49.91; N, 8.03; H, 3.75. Found: C, 48.94; N, 7.70; H, 3.78.
Coordination Polymer 12. In a vial (L22.00 ꢀ 65 ꢀ 1 mm)
protected from light, a solution of 9 (10 mg, 0.021 mmol) in THF
(10 mL) was slowly diffused into an EtOH solution (5 mL)
of AgPF6 (2.67 mg, 0.0106 mmol). After two weeks, dichroic
green-orange crystals were obtained (7.7 mg, 51.2%) and ana-
lyzed by X-ray diffraction on a single crystal. IR (ATR, cm-1):
[(acac)Cu(6)], 8. A THF (8 mL) solution of 6 (25 mg, 0.087
mmol) was mixed with a THF (8 mL) solution of Cu(acac)2 (22.8
mg, 0.087 mmol). The reaction mixture was stirred for 20 min
and then was evaporated to dryness under vacuum. The crude
product was purified by chromatography (SiO2, CHCl3, Rf =
0.44). The resulting solid was washed with n-pentane (50 mL) to
afford 8 as a red solid (27.3 mg, 69.5%). Dichroic red-green
crystals were grown by slow evaporation of a CHCl3 solution of
the complex. UV-vis, (CH2Cl2) λmax(nm)/ε (mol-1 L cm-1):
227 (33 000), 294 (24 000), 342 (15 000), 482 (32 000), 493
(39 000). Anal. Calcd for C23H20N4O2Cu: C, 61.67; N, 12.51;
H, 4.50. Found: C, 61.62; N, 12.67; H, 4.82.
νCN 2196. Anal. Calcd for C52H46AgCu2F6N10O5P: C, 49.14; N,
11.02; H, 3.65. Found: C, 48.87; N, 11.35; H, 3.91.
Coordination Polymer 13. In a crystallization tube (L22.00 ꢀ
65 ꢀ 1 mm) protected from light, a solution of 9 (10 mg, 0.021
mmol) in CHCl3 (7 mL) was slowly diffused into a benzene
solution (7 mL) of AgBF4 (2.10 mg, 0.0106 mmol). After two
weeks, dichroic green-orange crystals were obtained (7.2 mg,
55.9%) and analyzed by X-ray diffraction on a single crystal. IR
(ATR, cm-1):νCN 2194. Anal. Calcd for C54H44AgBCu2F4N10O4:
C, 53.22; N, 11.49; H, 3.64. Found: C, 52.28; N, 11.62; H, 3.88
Coordination Polymer 14. A solution of 9 (9 mg, 0.019 mmol)
in o-xylene (4 mL) was mixed with an o-xylene (2 mL) solution of
AgOTf (4.8 mg, 0.0095 mmol) and stirred for 1 min. A red
precipitate appeared, which was dissolved upon the addition of
CH3CN (2.5 mL). Slow evaporation of CH3CN in the absence of
light afforded the product as dark-green crystals (7.8 mg,
62.7%). IR (ATR, cm-1): νCN 2251.
[(acacCN)Cu(5)], 9. A THF (30 mL) solution of Cu(acacCN)2
(109 mg, 0.349 mmol) was added to a THF (20 mL) solution of 5
(100 mg, 0.349 mmol). After stirring for 20 min, the resulting
precipitate was filtred off and washed with ether (3 ꢀ 75 mL) to
afford 9 as a green-red solid (136 mg, 82.4%). Dichroic red-
green crystals were grown by slow evaporation of a CHCl3
solution. UV-vis (CH2Cl2), λmax(nm)/ε (mol-1 L cm-1): 227
(28 000), 288 (12 000), 333 (9000), 479 (21 000), 491 (27 000). IR
(ATR, cm-1): νCN 2206. HRMS (ESI), m/z: [M þ H]þ calcd for
C24H20N5O2Cu, 473.091; found, 473.091.
[(acacCN)Cu(6)], 10. A THF solution (20 mL) of 6 (55 mg,
0.19 mmol) was mixed with a THF solution (30 mL) of Cu-
(acacCN)2 (60 mg, 0.19 mmol). The reaction mixture was stirred
X-Ray Crystallography. Data (Tables 1 and 2) were collec-
ted on a Bruker SMART CCD diffractometer with Mo KR

Article
Inorganic Chemistry, Vol. 49, No. 1, 2010 335
Table 2. Crystallographic Data for Compounds 10-14
10
11
12
13
14
formula
fw
C
472.98
monoclinic
P21
7.0712(3)
15.8916(7)
9.4970(4)
24H19CuN5O2
C58H52AgCu2F6N8O4Sb
1395.78
triclinic
C52H46AgCu2F6N10O5P
1270.91
triclinic
P1
6.8023(7)
8.5991(10)
22.727(3)
82.210(4)
81.502(4)
79.614(4)
1285.1(2)
1
C54H44AgBCu2F4N10O4
1218.78
triclinic
C57H48AgCu2F3N10O7S
1309.09
triclinic
cryst syst
space group
P1
P1
P1
˚
a, A
10.2596(2)
15.4490(3)
19.2748(4)
110.1590(10)
97.3400(10)
95.1390(10)
2814.97(10)
2
6.8931(3)
8.5345(4)
22.8014(10)
79.907(2)
83.993(2)
78.969(2)
1292.71(10)
1
11.9313(2)
12.1710(3)
21.7466(5)
74.9010(10)
82.2040(10)
64.6080(10)
2753.35(10)
2
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
105.4930(10)
3
˚
V, A
Z
T, K
1028.42(8)
2
173(2)
1.095
11992
173(2)
1.637
33360
173(2)
1.642
12020
173(2)
1.261
23641
173(2)
1.229
31895
μ, mm-1
reflns collected.
ind. reflns (Rint
R1 (I > 2σ(I))a
wR2 (I > 2σ(I))a
R1 (all data)a
wR2 (all data)a
GOF
)
4294 (0.0280)
0.0272
0.0661
0.0290
0.0678
1.096
12742 (0.0342)
0.0452
0.1070
0.0649
0.1332
1.129
5716 (0.0318)
0.0456
0.0991
0.0772
0.1099
1.016
5824 (0.0267)
0.0302
0.0723
0.0384
0.0755
1.033
12394 (0.0280)
0.0464
0.1131
0.0552
0.1191
1.172
P
P
P
P
4 1/2
]
a R1 =
Fo| - |Fc
/
|Fo|; wR2 = [ w(Fo2 - Fc2)2/ wFo
.
radiation. The structures were solved using SHELXS-97 and
refined by full matrix least-squares on F2 using SHELXL-97
with anisotropic thermal parameters for all non-hydrogen
atoms. The hydrogen atoms were introduced at calculated
positions and not refined (riding model).
CCDC 751566-751576 contain the supplementary crystallo-
graphic data for compounds 3, 4, 7-10 (C4H8O2), and 10-14.
3
These data can be obtained free of charge via www.ccdc.cam.ac.
uk/data_request/cif.
Results and Discussion
Synthesis. The aldehyde precursors 1 and 2 were pre-
pared by a Cu(I)-catalyzed reaction of p-bromobenzalde-
hyde with imidazole and pyrazole, respectively.15 Their
subsequent reaction in neat pyrrole in the presence of a
catalytic amount of TFA, as developed by Lindsey and
co-workers,16 leads to the formation of dipyrromethanes
3 and 4 in 69 and 77% yields, respectively. The latter are
readily oxidized with DDQ to afford dipyrrins 5 and 6 in
61 and 80% yields, respectively, after purification by
column chromatography (SiO2). Reaction of either di-
pyrrin 5 or 6 with 1 equiv of Cu(acacR)2 (R = H, CN)
affords the corresponding heteroleptic Cu(acacR)(dpm)
complexes 7-10, in 58-82% yield. All four complexes
feature two absorption bands between 470 and 495 nm in
CH2Cl2 solutions, which are in agreement with reported
data in the literature11 for (acac)Cu(dpm) complexes. The
CN vibration stretch is observed in the IR spectra of
complexes 9 and 10 at 2206 and 2197 cm-1, respectively,
again in agreement with values reported for other Cu-
(acacCN)2 derivatives.14,17
Figure 2. Hydrogen-bonded networks in 3 (a) and 4 (b). Only N-H
hydrogen atoms are shown for clarity. Selected bond distances (A) and
˚
angles (deg), for 3: N1 N4i, 3.051(6); N2 N4ii, 3.031(7);
3 3 3
3 3 3
N1-H1 N4i, 160.3; N2-H2 N4ii, 164.1. For 4: N1 N4iii,
3 3 3
3 3 3
3 3 3
3.036(2); N1-H1A N4iii, 153.4. i = 1 þ x, y, -1 þ z; ii = 1 - x,
3 3 3
1 - y, 2 - z; iii = 1/2 - x, -1/2 þ y, 3/2 - z.
In 3, one imidazole nitrogen atom forms hydrogen bonds
with the pyrrolic N-H of two neighboring molecules,
leading thus to the formation of one-dimensional chains
along c (Figure 2a). This type of arrangement is reminiscent
of the recently reported crystal structures of other R,β-
unsubstituted dipyrromethanes.7e,18 In 4, a single hydrogen
bond is identified between a pyrrolic N-H and a pyrazole
N atom leading again to a 1D chain (Figure 2b) analogous
to the organization of dpm-py.7e
Crystal Structure of the Ligands and the Mononuclear
Complexes. Both dipyrromethane derivatives 3 and 4
were crystallized by the slow diffusion of n-pentane in a
THF solution. The former crystallizes in the triclinic space
group P1, while the latter crystallizes in the monoclinic
space group P21/n with one molecule in a general position.
Crystals of 7 were obtained by slow diffusion of Et2O
vapors into a CHCl3 solution. Complex 7 crystallizes in
(18) (a) Heinze, K.; Reinhart, A. Z. Naturforsch. 2005, 60b, 758–762. (b)
Baudron, S. A.; Salazar-Mendoza, D.; Hosseini, M. W. CrystEngComm. 2009,
11, 1245–1254.
(16) Littler, B. J.; Miller, M. A.; Hung, C.-H.; Wagner, R. W.; O’Shea,
D. F.; Boyle, P. D.; Lindsey, J. S. J. Org. Chem. 1999, 64, 1391–1396.
(17) Fackler, J. P. J. Chem. Soc. 1962, 1957–1960.

336 Inorganic Chemistry, Vol. 49, No. 1, 2010
Pogozhev et al.
˚
Figure 3. Crystal structure of complexes 7 (a) and 8 (b). Hydrogen atoms have been omitted for clarity. Selected bond lengths (A), for 7: Cu1-O1,
1.9554(17); Cu1-O2, 1.9478(16); Cu1-N1, 1.9286(15); Cu1-N2, 1.9391(14). For 8: Cu1-O1, 1.9411(19); Cu1-O2, 1.9225(19); Cu1-N1, 1.942(2);
Cu1-N2, 1.961(2).
Figure 5. Crystal structure of the 10 C4H8O2 solvate showing the
3
axially coordinated dioxane molecule. Hydrogen atoms have been
˚
omitted for clarity. Selected bond lengths (A), for 7: Cu1-O1,
1.9573(11); Cu1-O2, 1.9470(12); Cu1-N1, 1.9534(12); Cu1-N2,
1.9628(13); Cu1-O3, 2.443(2).
Figure 4. Two independent 1D polymers in the crystal structure of
complex 9. Hydrogen atoms have been omitted for clarity. Selected bond
˚
lengths (A): Cu1-O1, 1.9732(18); Cu1-O2, 1.9931(19); Cu1-N1,
1.966(2); Cu1-N2, 1.948(2); Cu1-N4i, 2.245(2); Cu2-O3, 1.9694(19);
Figure 6. One-dimensional polymer in the crystal structure of complex
Cu2-O4, 1.9930(19); Cu2-N6, 1.968(2); Cu2-N7, 1.957(2); Cu2-N9,
10. Hydrogen atoms have been omitted for clarity. Selected bond lengths
2.302(2). i = 1 - x, 1/2 þ y, 3/2 - z; ii = -x, 1/2 þ y, 1/2 - z.
˚
(A) and angle (deg): Cu1-O1, 1.9706(16); Cu1-O2, 1.9465(16);
Cu1-N1, 1.9586(18); Cu1-N2, 1.9648(19); Cu1-N5i, 2.489(2);
C24i-N5i-Cu1, 114.4. i = 1 þ x, y, z.
the triclinic space group P1 with one molecule in a general
position. Complex 8, obtained upon slow evaporation
of CHCl3, crystallizes in the monoclinic space group
P21/c with one molecule in a general position. In both
compounds, the copper atom is in a square planar
environment with Cu-N and Cu-O distances close
to those reported for other analogous complexes
(Figure 3).8,11 Interestingly, unlike other reported
Figure 7. Complex [Ag(7)2]þ in 11. Hydrogen atoms, solvent molecules,
(acac)Cu(dpm) or (hfac)Cu(dpm) species,11 the periph-
eral coordinating group, the diazole here, does not co-
ordinate the Cu(II) center. A difference between the two
complexes lies in the angle between the diazole and the
phenyl ring, 30.9ꢀ for 7 and 13.9ꢀ for 8. The angle for the
latter might explain the absence of coordination to a
neighboring complex, as reported for the analog incor-
porating the 5-(2-pyridyl)dipyrrin.11a
as well as the SbF6- anion have been omitted for clarity. Selected bond
˚
lengths (A) and angle (deg): Ag1-N4, 2.079(3); Ag1-N8, 2.074(3);
N4-Ag1-N8, 171.89(14).
42.9ꢀ between the acacCN and the dpm chelates
(Figure 4a), the other is less distorted with an angle of
8.8ꢀ between the two groups. Such a concave arrange-
ment away from the additional coordinating atom has
been observed for other (acac)Cu(dpm) species.11 The
difference in the organizations of 7 and 9 is surprising but
might be due to packing effects preventing the formation
of a polymer with the earlier complex.
For compound 10, depending on the solvent of crystal-
lization used, two different crystal structures were ob-
tained. In both cases, the arrangement of the copper
complexes is quite different from the one observed for
9. Upon slow diffusion of n-pentane vapors into a dioxane
Crystals of 9 were obtained by slow evaporation of a
CHCl3 solution. Complex 9 crystallizes in the monoclinic
space group P21/c with two molecules in general posi-
tions. In both molecules, the Cu ion is coordinated to both
chelates, the dpm and the acacCN, and to the imidazole
group of a neighboring complex with Cu-Nimid distances
˚
of 2.245(2) and 2.302(2) A, leading to the formation of 1D
coordination polymers (Figure 4). This parallels the
crystal structure of other heteroleptic (acac)Cu(dpm)’s
where the dpm bears a coordinating peripheral nitrogen
atom, such as pyridine or quinoline.11 The main differ-
ence between the two independent complexes lies in the
coordination geometry around the copper atoms. While
one complex deviates from planarity with an angle of
solution of 10, dioxane solvate crystals 10 C4H8O2
3
were obtained (see Figure 5). The latter crystallizes in
the triclinic space group P1 with one copper complex
and one solvent molecule in a general position. The
copper center features a square pyramidal coordination

Article
Inorganic Chemistry, Vol. 49, No. 1, 2010 337
Figure 8. Coordination ribbon [Ag(9)2]þꢁ observed for 12 and 13. Hydrogen atoms, solvent molecules, as well as the anions have been omitted for clarity.
˚
Selected bond lengths (A) and angles (deg), for 12: Ag1-N4, 2.090(3); Cu1-N5ii, 2.631(4); N4-Ag1-N4i, 180.0(3); C24ii-N5ii-Cu1, 103.6. For 13:
Ag1-N4, 2.084(3); Cu1-N5ii, 2.620(4); N4-Ag1-N4i, 180.0(3); C24ii-N5ii-Cu1, 105.4. i = -2 - x, 2 - y, -z, ii = 1 þ x, y, z.
geometry, being coordinated to the acacCN and the dpm
chelates, as well as to an oxygen atom of the dioxane
molecule. Unlike in the case of 9, the azole nitrogen atom
is not coordinated to the copper center.
copper atoms is similar to the one observed in the
structure of 7. The Agþ cation is coordinated in a linear
fashion to two imidazole groups belonging to two copper
complexes (Figure 7) with a Ag-Nimid distance close to
the one previously observed for similar compounds.12 As
expected (Figure 1a), the absence of a further coordinat-
ing group in 7 prevents the self-assembly process through
coordination bonds to take place, and thus a discrete
species is formed. To investigate the role played by a
peripheral nitrile group on the copper complexes, 9 was
reacted with silver salts in a 2:1 stoichiometry.
Upon slow vapor diffusion of n-pentane in a CHCl3
solution of the complex, crystals of 10 (nonsolvated) were
obtained. Complex 10 crystallizes in the monoclinic space
group P21 with one molecule in a general position. The
copper ion is coordinated to the acacCN and dpm
chelates with bond distances as expected for such com-
plexes. Here again, the azole nitrogen atom is not co-
ordinated to the copper center, but a one-dimensional
chain is nonetheless formed owing to a weak interaction
of the metal center with the nitrogen atom of the CN
group of a neighboring complex (Figure 6). The
Interestingly, upon reacting complex 9 with either
AgPF6 or AgBF4 salts, isomorphous heterometallic sys-
tems were obtained. Orange crystals of [Ag(9)2]¥(PF6)
(THF), 12, were obtained upon slow diffusion of an
EtOH solution of AgPF6 into a THF solution of 9, while
crystals of [Ag(9)2]¥(BF4) (C6H6), 13, were obtained from
a CHCl3/benzene mixture (see Figure 8). Only the struc-
ture of 12 will be discussed hereafter. This compound
crystallizes in the triclinic space group P1 with a silver ion
on an inversion center, one copper complex 9 and one
˚
Cu-NacacCN distance of 2.489(2) A is rather long, and
the CNCu angle of 114.4ꢀ deviates largely from linearity.
These geometrical parameters are however similar to the
ones observed in the crystal structure of other reported
Cu(acacCN)2 complexes.14,19 This structure illustrates
the coordination, although weak, of the peripheral nitrile
group to the copper center, as depicted in Figure 1b.
Heterometallic Architectures. With these four com-
plexes in hand, the preparation of heteronuclear species
was attempted by their reaction with silver salts. Unfor-
tunately, the two pyrazole functionalized complexes 8
and 10 did not form crystalline heterometallic systems
upon reaction with silver salts either by slow evaporation
of benzene/MeCN mixtures or by slow liquid/liquid
diffusion in a tube. This is rather surprising given that
some phenyl-pyrazole derivatives have been reported to
coordinate silver ions.13 This might be related to the
position of the azole donor atom. We will illustrate here-
after the strategy presented in Figure 1 using complexes
7 and 9.
-
PF6 anion, both in general positions, and one THF
molecule on an inversion center. The silver ion is coordi-
nated linearly to the imidazole group of two molecules of
9, as in 11, hence forming a trinuclear species. Owing to
the interaction of the peripheral nitrile groups with
copper atoms of neighboring complexes, the trinuclear
complexes are interconnected (dCu-NacacCN = 2.631(4)
˚
A), affording 1D polymers along the c axis. Conse-
quently, the copper centers are in a square pyramidal
environment. As stated above, this type of coordination
mode has been also observed for complex 10. Although
the Cu-NacacCN distance observed for 12 is longer than
the one observed for 10, it is nevertheless in the same
range as those observed for other self-assembled hetero-
leptic complexes incorporating the [(acacCN)Cu]þ frag-
ment.14,19
To prepare a discrete heteronuclear complex such as
the one presented schematically in Figure 1a, complex 7
was reacted with silver salts. Upon slow diffusion of a
benzene solution of AgSbF6 into a THF solution of 7,
crystals of the heterometallic complex [Ag(7)2](SbF6)
(C6H6)2, 11, were obtained. This compound crystallizes
in the triclinic space group P1 with two complexes 7, one
silver ion, a SbF6- anion, and two benzene molecules in
general positions. The coordination geometry around the
Slow evaporation of a MeCN/o-xylene solution of 9
and AgOTf afforded orange crystals of [Ag(9)2(OTf)]¥
(C8H10), 14. It crystallizes in the triclinic space group P1
with two complexes 9, one Agþ cation, one triflate anion,
and an o-xylene molecule in a general position. The two
complexes 9 differ in the geometry around the copper
centers. While one shows a square planar arrangement,
the other is in a square pyramidal coordination environ-
ment owing to an interaction with an oxygen atom of the
(19) (a) Soldatov, D. V.; Ripmeester, J. A.; Shergina, S. I.; Sokolov, I. E.;
Zanina, A. S.; Gromilov, S. A.; Dyadin, Y. A. J. Am. Chem. Soc. 1999, 121,
4179–4188. (b) Ma, B.-Q.; Gao, S.; Yi, T.; Xu, G.-X. Polyhedron 2001, 20, 1255–
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˚
triflate anion (dCu-O = 2.405(3) A). As in the case of 11,
the Agþ center is coordinated to the two copper com-
plexes via the imidazole groups (Figure 9). The coordina-
tion geometry around the silver ion however deviates

338 Inorganic Chemistry, Vol. 49, No. 1, 2010
Pogozhev et al.
self-assemble into one-dimensional chains but with different
connectivity patterns. In the case of the imidazole appended
complex 9, the diazole is coordinated to the copper atom in a
square pyramidal coordination environment. Rather inter-
estingly, in the case of the pyrazole analogue, 10, the
peripheral nitrile group of the acacCN capping ligand is
weakly coordinated to a copper atom. Upon self-assembly of
the imidazole functionalized complexes 7 and 9 with silver
salts, trinuclear species are formed. While, in the case of 7, the
absence of peripheral coordinating nitrile groups prevents
any self-assembly based on coordination processes leading to
extended architectures, for 9, the trinuclear complexes form
one-dimensional polymers. In the presence of a weakly
-
coordinating anion such as BF4 or PF6-, the CN groups
Figure 9. Portions of 1-D polymers [Ag(9)2(OTf)]ꢁ in 14 showing the
interdigitation of consecutive polymers. Hydrogen atoms and solvent
weakly interact with the copper atoms of another trinuclear
unit. In the case of the coordinating OTf- anion, the axial
position on the copper center is occupied and thus not
available. Consequently, the interaction of the nitrile group
takes place with the silver ion of another trinuclear unit.
These results illustrate that proper functionalization of het-
eroleptic complexes can lead to the formation of extended
heterometallic architectures upon association with another
metal center. This approach seems promising for the devel-
opment of novel heteronuclear networks. Such work is
currently underway in our laboratory with the development
of new (acacCN)xM(dpm)y complexes and the study of their
self-assembly using other metal centers.
˚
molecules have been omitted for clarity. Selected bond lengths (A)
and angles (deg): Ag1-N4, 2.135(3); Ag1-N9, 2.141(3); Ag1-N10,
2.627(3); Cu2-O5, 2.405(3); N4-Ag1-N9, 154.93(10); N4-Ag1-N10,
109.79(10); N9-Ag1-N10, 93.94(10).
from linearity with a Nimid-Ag-Nimid angle of
154.93(10)ꢀ. This is due to an additional weak CN Ag
interaction (dNCN-Ag = 2.627(3) A) with the nitrile group
3 3 3
˚
of the acacCN capping ligand of a neighboring complex
(Figure 9). This leads to the formation of one-dimen-
sional chains of trinuclear species. Since only one of the
two complexes 9 interact with the silver ion, the resulting
chain possesses a comb shape. The consecutive comb
shape arrangements are interdigitated with a face-to-face
organization of the copper complexes. The space between
combs is occupied by o-xylene molecules.
ꢀ
Acknowledgment. We thank the Universite de Stras-
bourg, the Institut Universitaire de France, the Ministry
of Education and Research, the CNRS, and Marie Curie
Est Actions FUMASSEC Network (Contract No.
MEST-CET-2005-020992) for financial support.
Conclusion
Two novel imidazole and pyrazole 5-phenyl-dipyrrins
have been prepared and used as ligands for the formation
of a series of heteroleptic (acacR)Cu(dpm) complexes (R =
H, CN). The two (acacCN)Cu(dpm) complexes 9 and 10
Supporting Information Available: Crystallographic data in
CIF format. This material is available free of charge via the
Internet at http://pubs.acs.org.