Syntheses, structures, characterisation, and spectroscopic properties of CuI and AgI complexes with extended C- H···π and π···π interactions

Article abstract of DOI:10.1071/CH13566

Based on the ligands N,N′-bis(pyridin-2-ylmethylene)benzene-1,4- diamine (pmb) and N,N′-bis(pyridin-2-ylmethylene)biphenyl-4,4′- diamine (pmbb), the three compounds [Cu₂(pmb) (PPh₃) ₂(Cl)₂] (1), [Cu₂(pmbb)(CH₃CN) 2(PPh₃)2](BF4)2·2DMF (2), and [Ag2(pmbb)(PPh₃)2] (ClO₄)₂ (3) have been synthesised and characterised. Structural analysis reveals that all of these complexes contain 1D supramolecular arrays, with different variations in π-stacking patterns and intermolecular C-H···π interactions. Crystal structures of 1 and 2 contain 1D tape-like arrays formed by C-H···π and π···π interactions, and an ordered-layer-lattice of DMF and BF4-in 2 is located between the one-dimensional array. For 3, π-stacking interactions lead to the construction of 1D supramolecular arrays and a 2D network. The results indicate that C-H···π and π···π interactions play an important role in the construction of the supramolecular structure. In addition, the absorption peaks of complexes 1 and 3 in the solid state at room temperature show intraligand charge transfer and metal-to-ligand charge transfer absorptions. The optical and fluorescent properties of 2 were also studied in acetonitrile solution at room temperature. CSIRO 2014.

Full text of DOI:10.1071/CH13566

CSIRO PUBLISHING
Aust. J. Chem. 2014, 67, 887–894
Full Paper
http://dx.doi.org/10.1071/CH13566
Syntheses, Structures, Characterisation, and Spectroscopic
Properties of CuI and AgI Complexes with Extended
. . .
. . .
p Interactions
C H
]
p and p
A
A B
,
Ting-Hong Huang and Min-Hua Zhang
A
Key Laboratory for Green Chemical Technology (Ministry of Education of China), R&D
Center for Petrochemical Technology, Tianjin University, Tianjin 300072, China.
Corresponding author. Email: mhzhang@tju.edu.cn
B
Based on the ligands N,N0-bis(pyridin-2-ylmethylene)benzene-1,4-diamine (pmb) and N,N0-bis(pyridin-2-ylmethylene)
biphenyl-4,40-diamine (pmbb), the three compounds [Cu2(pmb) (PPh3)2(Cl)2] (1), [Cu2(pmbb)(CH3CN)2(PPh3)2]
(BF4)2 ꢀ 2DMF (2), and [Ag2(pmbb)(PPh3)2] (ClO4)2 (3) have been synthesised and characterised. Structural analysis
reveals that all of these complexes contain 1D supramolecular arrays, with different variations in p-stacking patterns and
intermolecular C–H ꢀ ꢀ ꢀ p interactions. Crystal structures of 1 and 2 contain 1D tape-like arrays formed by C–H ꢀ ꢀ ꢀ p and
p ꢀ ꢀ ꢀ p interactions, and an ordered-layer-lattice of DMF and BFꢁ4 in 2 is located between the one-dimensional array. For
3, p-stacking interactions lead to the construction of 1D supramolecular arrays and a 2D network. The results indicate that
C–H ꢀ ꢀ ꢀ p and p ꢀ ꢀ ꢀ p interactions play an important role in the construction of the supramolecular structure. In addition,
the absorption peaks of complexes 1 and 3 in the solid state at room temperature show intraligand charge transfer and
metal-to-ligand charge transfer absorptions. The optical and fluorescent properties of 2 were also studied in acetonitrile
solution at room temperature.
Manuscript received: 21 October 2013.
Manuscript accepted: 29 January 2014.
Published online: 28 February 2014.
Introduction
to the construction of 1D supramolecular arrays and a 2D
network. Moreover, the solid-state UV-vis absorption spectra
of complexes 1 and 3 have been investigated at room tempera-
ture. The photophysical properties of 2 were also observed in
acetonitrile solution.
In recent years, supramolecular self-assembly has gained
importance because of its potential application in biology,[1–6]
chemistry,[7–12] and materials science.[13–15] Considerable
attention has been paid to the construction of supramolecular
aggregates by monomeric metallo-subunits,[16,17] but predicting
and designing supramolecular structures is difficult because
of the weakness of the interactions involved. As such,
p ꢀ ꢀ ꢀ p[18–21] or C–H ꢀ ꢀ ꢀ p[22–26] interactions which lead to
aggregation into cyclic supramolecular structures are very
intriguing because they can provide a structural and functional
basis for potential applications.[27,28] In particular, the extent of
the p ꢀ ꢀ ꢀ p and C–H ꢀ ꢀ ꢀ p stacking of copper(I) complexes
containing a pyridyl ligand has led to the observation of inter-
esting structures[29–33] and spectroscopic properties,[34,35] but
supramolecular arrays of metal complexes made only by
p ꢀ ꢀ ꢀ p or C–H ꢀ ꢀ ꢀ p stacking are relatively difficult to
form.[36,37] It seems that the design, synthesis, and characteri-
sation of metal complexes with supramolecular structures are
challenging but important.
In the present study, we report the synthesis, structure,
and properties of three complexes [Cu2(pmb) (PPh3)2(Cl)2]
(1), [Cu2(pmbb)(CH3CN)2(PPh3)2](BF4)2 ꢀ 2DMF (2), and
[Ag2(pmbb)(PPh3)2] (ClO4)2 (3) (pmb ¼ N,N0-bis(pyridin-
2-ylmethylene)benzene-1,4-diamine, pmbb ¼ N,N0-bis(pyridin-
2-ylmethylene)biphenyl-4,40-diamine). It is interesting to find
that all the atoms of pmb and pmbb are almost in the same
plane, and C–H ꢀ ꢀ ꢀ p and p ꢀ ꢀ ꢀ p stacking interactions lead
Experimental
General Methods and Materials
All chemicals were of A. R. grade and were used as received
without further purification. The ligands pmb and pmbb were
prepared according to the literature.[38–40] IR spectra were
recorded as KBr pellets on a Nicolet 6700 spectrometer in the
1
range 4000–450 cmꢁ1. H and 31P{1H} spectra were recorded
on a Bruker 400 spectrometer at 400.15 and 161.98 MHz,
respectively. The solid UV-visible absorbance spectra of com-
plex 1 was measured with a PerkinElmer L750 spectrometer.
Absorption spectra of 3 and pmbb were measured with a U-3010
(solid) spectrophotometer. BaSO4 was used as an absorbance
standard in the UV-visible diffuse absorbance experiments.
Absorption spectra of 2 in acetonitrile solution were measured
with a Varian CARY-50UV spectrophotometer. The lumines-
cent spectra of 2 in acetonitrile solution were obtained at room
temperature on a Cary Eclipse fluorescence spectrophotometer.
[Cu2(pmb)(PPh3)2(Cl)2] (1)
A mixture of CuCl (0.0099 g, 0.1 mmol) and PPh3 (0.0262 g,
0.1 mmol) in 4 mL of DMF was stirred at room temperature for
Journal compilation Ó CSIRO 2014
www.publish.csiro.au/journals/ajc

888
T.-H. Huang and M.-H. Zhang
Table 1. Crystal data and structure refinement details of complexes 1 3
]
Parameter
1
2
3
Empirical formula
Formula weight
Crystal system
Space group
C54H44Cl2Cu2 N4P2
1008.85
C70H68B2Cu2F8N8 O2P2
1415.96
C60H48Ag2Cl2N4 O8P2
1301.60
Triclinic
Triclinic
Triclinic
P-1
P-1
P-1
˚
a [A]
8.4647(7)
8.4349(2)
8.5682(4)
˚
b [A]
˚
c [A]
9.1304(8)
10.9863(4)
19.3439(8)
106.408(2)
90.366(3)
11.1482(5)
14.9327(7)
97.140(3)
17.4659(15)
75.673(6)
a [deg]
b [deg]
g [deg]
84.209(6)
97.331(3)
66.318(5)
100.415(2)
1688.09(10),1
1.393
100.461(3)
1375.20(11), 1
1.572
3
˚
Volume [A ], Z
1197.75(18), 1
1.399
r
calc [g cmꢁ3
]
m [mmꢁ1
F(000)
]
1.107
0.751
0.927
518
730
658
y range [deg]
2.41–27.64
11270
1.96–27.67
16064
1.88–27.54
12792
Reflections collected
Independent reflections
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I . 2s (I)]
R indices (all data)
5375 [R(int) 0.0402]
5375/0/289
1.034
7673 [R(int) 0.0410]
7673/10/427
1.026
6117 [R(int) 0.0150]
6117/0/352
1.043
R1 0.0476, wR2 0.1016
R1 0.1103, wR20.1221
0.393 and ꢁ0.363
R1 0.0620, wR2 0.1559
R1 0.0999, wR2 0.1779
1.124 and ꢁ1.053
R1 0.0364, wR2 0.1020
R1 0.0437, wR2 0.1089
1.218 and ꢁ0.894
ꢁ3
˚
Largest difference peak and hole [e A
]
˚
Table 2. Selected bond lengths (A) and angles (deg) for complexes 1 3
]
1 h and then pmb (0.0143 g, 0.05 mmol) was added. The reaction
mixture was allowed to stir for 2 h at room temperature. The
vapour diffusion of diethyl ether into the solution gave red block
crystals. The complex was obtained by filtration, washed with
diethyl ether, and dried under vacuum. Yield: 0.0316 g (30 %).
nmax /cmꢁ1 3423 (br), 1584 (w), 1475 (m), 1434 (s), 1094
(m), 841 (m), 744 (s), 696 (s), 519(s). dH (CD3SOCD3, 258C,
TMS) 7.02–9.13 (44H, pmb þ PPh3). dP (CD3SOCD3, 258C,
TMS) 25.73.
Bond lengths
Bond angles
1
Cu(1)—N(1)
Cu(1)—N(2)
Cu(1)—P(1)
Cu(1)—Cl(1)
2.096(3)
N(1)—Cu(1)—N(2)
N(1)—Cu(1)—P(1)
N(2)—Cu(1)—P(1)
N(1)—Cu(1)—Cl(1)
N(2)—Cu(1)—Cl(1)
P(1)—Cu(1)—Cl(1)
2
78.73(10)
113.11(8)
118.83(8)
107.25(9)
118.16(8)
114.39(4)
2.133(3)
2.2053(10)
2.2812(12)
[Cu2(pmbb)(CH3CN)2(PPh3)2](BF4)2 ꢀ 2DMF (2)
Cu(1)—N(1)
Cu(1)—N(2)
Cu(1)—N(3)
Cu(1)—P(1)
2.078(3)
2.098(3)
1.969(4)
2.2019(10)
N(1)—Cu(1)—N(2)
N(1)—Cu(1)—N(3)
N(2)—Cu(1)—N(3)
N(1)—Cu(1)—P(1)
N(2)—Cu(1)—P(1)
N(3)—Cu(1)—P(1)
3
79.78(12)
112.05(14)
105.56(13)
113.37(9)
121.16(9)
118.63(11)
A mixture of [Cu(CH3CN)4]BF4 (0.0316 g, 0.1 mmol) and PPh3
(0.0262 g, 0.1 mmol) in 4 mL of DMF was stirred at room
temperature for 0.5 h and then pmbb (0.0181 g, 0.05 mmol) was
added. The reaction mixture was allowed to stir for 1 h at room
temperature. The vapour diffusion of diethyl ether into the
solution gave red block crystals. The complex was obtained by
filtration, washed with diethyl ether, and dried under vacuum.
Yield: 0.0525 g (75 %).
Ag(1)—N(1)
Ag(1)—N(2)
Ag(1)—P(1)
2.315(2)
2.282(2)
2.3496(6)
N(1)—Ag(1)—N(2)
N(1)—Ag(1)—P(1)
N(2)—Ag(1)—P(1)
73.89(7)
134.02(6)
151.94(5)
n
max /cmꢁ1 3059 (m), 1680 (v.), 1487 (m), 1435 (s), 1383 (s),
1056 (v.), 833 (m), 749 (s), 697 (s), 520(s). dH (400 MHz,
CDCl3) 2.04 (6H, CH3–Cꢂ), 2.65–3.19 (12H, CH3–N–),
6.98–9.50 (50H, –CH¼O þ pmbb þ PPh3). dP (CD3SOCD3,
258C, TMS) 1.44.
TMS) 7.13–9.23 (48H, pmbb þ PPh3). dP (CD3SOCD3, 258C,
TMS) 15.15.
X-Ray Crystallography
Crystals suitable for X-ray structure analysis were obtained
by vapour diffusion of diethyl ether into a solution of com-
plexes 1 3. Reflection intensity data were collected on a Bruker
[Ag2(pmbb)(PPh3)2](ClO4)2 (3)
A mixture of AgClO4 ꢀ H2O (0.0221 g, 0.1 mmol) and PPh3
(0.0262 g, 0.1 mmol) in 4 mL of DMF/CH3CN was stirred at
room temperature for 1 h and then pmbb (0.0181 g, 0.05 mmol)
was added. The reaction mixture was allowed to stir for 1 h at
room temperature. The vapour diffusion of diethyl ether into the
solution gave red block crystals. The complex was obtained by
filtration, washed with diethyl ether, and dried under vacuum.
Yield: 0.0594 g (45 %).
]
APEX CCD diffractometer with graphite monochromated
˚
MoKa radiation (l 0.71073 A) using the v technique at room
temperature. All structures were solved by direct methods and
refined by full-matrix least-squares on all F2 data using
SHELXTL.[41] All hydrogens were generated geometrically,
assigned fixed isotropic thermal parameters, and included in
structure factor calculations. Crystal and structure refinement
data are summarised in Table 1. Selected bond lengths and bond
angles are given in Table 2.
nmax /cmꢁ1 3454 (br), 1588 (w), 1483 (m), 1435 (s), 1088
(m), 825 (m), 747 (s), 695 (s), 522(s). dH (CD3SOCD3, 258C,

CuI/AgI Complexes
889
C5
C6
C4
(a)
(b)
C9
C8
C17
C3
C2
C18
C16
C15
C10
C1
P1
C7
C12
C13
C14
C11
Cu1
C26
N2
Cl1
C19
C20
N1
C25
C24
C27
C23
C22
C21
Fig. 1. (a) ORTEP view of the structure of 1. (b) p ꢀ ꢀ ꢀ p stacking interactions in the 1D tape-like arrays along the a-axis in 1. Hydrogen atoms are deleted for
clarity.
Results and Discussion
1D supramolecular arrays and a 2D network are formed by
C–H ꢀ ꢀ ꢀ p and p ꢀ ꢀ ꢀ p stacking interactions.
Syntheses
Reaction of a copper(I) salt with PPh3 and a pmbb or pmb ligand
in DMF solution gives a good yield of complexes 1 and 2, while
complex 3 is obtained by reaction of a silver(I) salt with PPh3 and
a pmbb ligand in DMF solution. With an equimolar amount of
CuI and PPh3 in the reaction solution, discrete complexes are
formed with a 1 : 1 stoichiometric ratio of CuI and PPh3; the
same crystal is also formed by the reaction of CuI and PPh3 in a
ratio of 1 : 2. At room temperature, complexes 2 and 3 are
soluble in DMF, DMSO, and CH3CN, slightly soluble in
CH2Cl2, and hardly soluble in toluene, methanol, and ethanol,
while complex 1 is soluble in DMF, DMSO, slightly soluble
in CH3CN, and hardly soluble in CH2Cl2 and CHCl3.
The IR spectra of complexes 1–3 display strong peaks
near 1433 cmꢁ1 that are assigned to the nPh(P–Ph) of PPh3. The
strong peaks at 1056 cmꢁ1 are assigned to ClꢁO stretches of
the ClOꢁ4 groups, while strong absorption peaks at 1088 cmꢁ1
are attributed to B–F stretches of BFꢁ4 groups. The absorption
peaks near 1485 cmꢁ1, in the range 850–690 cmꢁ1, and near
520 cmꢁ1 are dC–CH in the plane, dC–C in and out of the plane,
and nCu–P. The 1H NMR spectra of 1–3 display expected
resonances for the coordinated PPh3 and chelating ligand. The
31P NMR spectra of the complexes reveal one singlet each at
25.73, 1.44, and 15.15 ppm indicating the PPh3 ligands are trans,
which is in agreement with the structures of these com-
plexes.[42,43] The different chemical shifts of PPh3 1–3 in the
31P NMR spectra are attributable to their electronic environ-
ments being different: a shift to higher frequencies occurs
because of the deshielding effect of the chloride coordinated
to copper. To summarise, the singlet in the 31P{1H} NMR
spectrum is a result of both steric and electronic factors.
Crystal Structure of [Cu2(pmb)(PPh3)2(Cl)2] (1)
X-Ray diffraction analysis shows that the asymmetric unit of
1 contains half a pmb, one Cuþ, one PPh3, and one Clꢁ. The pmb
ligand bridges two copper atoms while each CuI ion is coordi-
nated by two N atoms from the pmb ligand, one P atom from the
PPh3 ligand, and one Cl atom, forming an S-shape conformation
˚
(Fig. 1a). The bond distances of Cu–Cl (2.2812(12) A), Cu–N
˚
˚
(2.096(3) and 2.133(3) A), and Cu–P 2.2053(10) A) are within
the normal ranges[47] and the metal ions are separated by a
˚
Cu ꢀ ꢀ ꢀ Cu distance of 8.874 A. Corresponding N–Cu–N and
P–Cu–Cl bond angles are 78.73(10)8 and 114.39(4)8, while the
N–Cu–P and N–Cu–Cl bond angles range from 107.25(9)8 to
118.83(8)8. S-shaped covalently prepared building blocks con-
taining p ꢀ ꢀ ꢀ p stacking interactions aggregate into 1D tape-
like arrays. The mean interplanar distances between pmb
˚
ligands are 3.817 and 3.826 A, with dihedral angles of 2.858
˚
and 08. The short distances between the atoms are 3.536 A for
˚
C–C and 3.577 A for C–N which are close to the sums of
the van der Waals radii,[48] showing typical p ꢀ ꢀ ꢀ p stacking
interactions (Fig. 1b). Moreover, intermolecular edge-face
(C–H ꢀ ꢀ ꢀ p) interactions (centroid ꢀ ꢀ ꢀ centroid distances:
˚
4.903 and 4.786 A, dihedral angle: 77.018 and 64.178,
˚
H ꢀ ꢀ ꢀ pcentroid: 2.84 and 2.65 A) are also observed which
make molecules arrange along the ab-plane (Fig. S1 in the
Supplementary Material). In all, there are two types of interac-
tions, C–H ꢀ ꢀ ꢀ p and p ꢀ ꢀ ꢀ p stacking interactions, to stabilise
the 1D arrays.
Crystal Structure of [Cu2(pmbb)(CH3CN)2(PPh3)2]
(BF4)2 ꢀ 2DMF (2)
Crystal Structures
Pmb being a large p-conjugated electron-deficient aromatic
ring is helpful for p-stacking. In order to explore further the
complementary influence of the aromatic systems on the forma-
tion of p-stacking metal complexes, we complexed bridging
pmbb instead of pmb.
Single crystal X-ray diffraction analysis of complex 2
revealed that the general structure is analogous to complex 1,
having an S-shape conformation with centrosymmetry. The
The molecular structures of complexes 1–3 were established
using X-ray diffraction. Crystallographic data for the three
compounds are shown in Table 1. Selected bond lengths
and bond angles are shown in Table 2. The structures of the
metal complexes of pmb or pmbb and related ligands are
different from those previously reported:[44–46] all atoms of
pmb and pmbb in these complexes are almost in the same plane;

890
T.-H. Huang and M.-H. Zhang
C22
C23
C21
C20
C15
C26
C24
C27
C28
C16
C14
N2
C19
C13
C25
C30
N1
C17
C18 C8
C7
C9
O1
Cu1
C29
P1
C1
C10
N3
C12
C11
C2
C3
C35
C31
C6
C5
F4
C32
N4
C34
F1
B
C33
F3
C4
F2
Fig. 2. ORTEP view of the structure of 2. Hydrogen atoms are deleted for clarity.
Fig. 3. (a) Intermolecular p ꢀ ꢀ ꢀ p interaction of 2. (b) Intermolecular C–H ꢀ ꢀ ꢀ p stacking interaction of 2. Hydrogen atoms are deleted for clarity.
˚
˚
structural analysis shows that 2 crystallises with triclinic sym-
metry with space group P-1 and the asymmetric unit contains
half a pmbb, one Cuþ, one PPh3, one CH3CN, one BFꢁ4 , and one
DMF molecule (Fig. 2). The pmbb ligand adopts a trans
coordination mode to bridge two copper atoms while each CuI
ion adopts a distorted tetrahedral geometry constructed by three
N atoms from pmbb and CH3CN, and one P atom from PPh3,
forming an S-shape conformation. The bond distances of Cu–N
3.213 A for C–C and 3.703 A for C–N which are close to the
sums of the van der Waals radii,[48] revealing typical p ꢀ ꢀ ꢀ p
stacking interactions (Fig. 3a). In tape-like arrays, neighbouring
cations contain intermolecular C–H ꢀ ꢀ ꢀ p interactions with
˚
centroid ꢀ ꢀ ꢀ centroid distances of 5.070 and 4.688 A, dihedral
angles of 91.48 and 66.68, and H ꢀ ꢀ ꢀ pcentroid distances of 2.78
˚
and 2.56 A (Fig. 3b). These suggest p ꢀ ꢀ ꢀ p and C–H ꢀ ꢀ ꢀ p
stacking interactions between pmbb ligands are the driving force
for supramolecular arrays, and are important in determining the
packing structure (Fig. 4a, b). Moreover, the supramolecular
arrays of [Cu2(pmbb)(CH3CN)2(PPh3)2]2þ are separated by an
ordered-layer-lattice of DMF and BFꢁ4 in compound 2 (Fig. 4c).
The structure also involves C–H ꢀ ꢀ ꢀ F hydrogen bonds
˚
˚
(1.969(4), 2.076(3), and 2.099(3) A) and Cu–P (2.2019(10) A)
are within the normal ranges[49–51] and the metal ions are
˚
separated by a Cu ꢀ ꢀ ꢀ Cu distance of 12.808 A. Corresponding
N–Cu–N bond angles range from 79.76(12)8 to 112.05(14) 8,
while the N–Cu–P bond angles range from 113.39(9)8 to 121.17
(9)8. In addition, intramolecular edge-face (C–H ꢀ ꢀ ꢀ p) interac-
tions are observed with centroid ꢀ ꢀ ꢀ centroid distances of
˚
˚
(H ꢀ ꢀ ꢀ F: 2.43 A, C ꢀ ꢀ ꢀ F: 3.27 A).
Crystal Structure of [Ag2(pmbb) (PPh3)2](ClO4)2 (3)
˚
˚
4.866 A, H ꢀ ꢀ ꢀ pcentroid distances of 2.76 A, and dihedral angles
of 66.898. Such weak C–H ꢀ ꢀ ꢀ p interactions would be a driving
force for all atoms of pmbb almost lying in the same plane and
play a stabilising role for the S-shape conformation.
Complex 3 was afforded when the starting materials of
AgClO4 ꢀ H2O and pmbb were treated in a mixed solvent of
CH3CN and DMF. X-ray diffraction analysis of a single crystal
shows that, in 3, p-stacking interactions induce aggregation
into 1D tape-like arrays consisting of a dinuclear building
block of [Ag2(pmbb)(PPh3)2](ClO4)2 in which the pmbb
ligand still adopts a trans coordination mode to link the two
Ag atoms while two PPh3 ligands coordinate to these two Ag
atoms, forming an S-shape conformation, as observed in the
In the packing structure of 2, S-shaped building blocks of
[Cu2(pmbb)(CH3CN)2(PPh3)2]2þ aggregate by p ꢀ ꢀ ꢀ p and
C–H ꢀ ꢀ ꢀ p stacking interactions into an ordered 1D tape-like
supramolecular array. The mean interplanar distances between
˚
pmbb ligands are 3.672 and 3.745 A, with dihedral angles of
12.058 and 16.248. The short distances between the atoms are

CuI/AgI Complexes
891
(a)
(c)
(b)
Fig. 4. (a) View of a 1D tape-like supramolecular array of [Cu2(pmbb)(CH3CN)2(PPh3)2]2þ along the a-axis (pmbb: N,N0-bis(pyridin-2-
ylmethylene)biphenyl-4,40-diamine). (b) Space filling diagram of [Cu2(pmbb)(CH3CN)2(PPh3)2]2þ in the packing structure. (c) The 1D tape-like
arrays of [Cu2(pmbb)(CH3CN)2(PPh3)2]2þ (green) complexes separated by the ordered-layer-lattice of DMF (red) and BFꢁ4 (blue) in 2.
C22
C21
C27
C24
N2
C23
Ag1
C26
C25
C20
C28
C19
N1
C2
C29
C30
C18
C13
C3
C4
C17
C16
C1
P1
C7
C5
C6
C8
C12
C15
C14
O2
C1
O4
C9
O1
C11
C10
O3
Fig. 5. ORTEP view of the structure of 3. Hydrogen atoms are deleted for clarity.
(a)
(b)
Fig. 6. 1D tape-like arrays formed by intermolecular p ꢀ ꢀ ꢀ p interactions along the (a) a- or (b) b-axis in 3. Hydrogen atoms are deleted for clarity.
above-mentioned discrete complexes (Fig. 5). The bond dis-
˚
corresponding N(2)–Ag(1)–N(1) bond angle is 73.89(7)8, while
the N–Ag–P bond angles range from 134.02(6)8 to 151.94(5)8.
The S-shaped building block is centrosymmetric with the
inversion centre at the centroid of the biphenyl ring.
tances of Ag–N (2.282(2) and 2.315(2) A) and Ag–P (2.3496
[52]
˚
(6) A) are within the normal ranges
and the metal ions
˚
are separated by a Ag ꢀ ꢀ ꢀ Ag distance of 13.042 A. The

892
T.-H. Huang and M.-H. Zhang
Fig. 7. 2D p-stacking network of complex 3. Hydrogen atoms and anions are deleted for clarity.
(b)
(a)
200
300
400
500
600
700
800
200
300
400
500
600
700
800
Wavelength [nm]
Wavelength [nm]
Fig. 8. (a) The solid-state UV-vis absorption spectra of complex 1, and (b) ligand N,N0-bis(pyridin-2-ylmethylene)biphenyl-4,40-diamine (pmbb) (__) and
complex 3 (y).
(a)
(b)
7
6
5
4
3
2
1
0
2.4
2.0
1.6
1.2
0.8
0.4
0
400
480
560
640
720
800
350 400 450 500 550 600 650 700 750 800
Wavelength [nm]
Wavelength [nm]
Fig. 9. (a) Absorption spectra of complex 2 in acetonitrile solution (5 ꢃ 10ꢁ4 M) at room temperature. (b) The excitation (y) and emission spectra (__) of 2 in
CH3CN solution (5 ꢃ 10ꢁ4 M) at room temperature.
In 3, intermolecular pmbb planes adopt offset displaced
p ꢀ ꢀ ꢀ p stacking interactions to link the cations into 1D tape-
like arrays along the a- or b-axis. The pmbb of one S-shaped
building block is parallel to another neighbouring pmbb from a
different S-shaped building block along the a-axis, with cen-
˚
troid–centroid distances of 3.604 and 4.044 A and dihedral
angles of 7.188 and 7.318(Fig. 6a). Similarly, the packing
structure involving p ꢀ ꢀ ꢀ p interactions along the b-axis is

CuI/AgI Complexes
893
˚
analogous to that of 2. But the interplanar distance of 3.63 A is
shorter than the corresponding values in complex 2 (Fig. 6b).
These indicate the presence of significant p ꢀ ꢀ ꢀ p stacking
interactions between the pmbb ligands. Moreover, each
S-shaped building block interacts with another four neigh-
bouring ones by this kind of p ꢀ ꢀ ꢀ p stacking interaction,
resulting in the stacking of the 1D tape-like supramolecular
arrays into a 2D stacking network along the ab-plane (Fig. 7).
The ordered-layer-lattice of ClOꢁ4 is located between these
networks. The packing structure also involves intermolecular
C–H ꢀ ꢀ ꢀ p interactions, with centroid–centroid distances of
network. All these show a structure variation from a 1D supra-
molecular array to a 2D stacking network. This structure vari-
ation may be related to the change of bridging ligands, anions,
and metal ions. In particular, all atoms of pmb and pmbb in 1–3
are almost in the same plane, which leads to the construction of
different p-stacking types. In the solid-state UV-vis absorption
spectra, complexes 1 and 3 show ILCT and MLCT absorptions.
In addition, photophysical property studies demonstrate that the
low energy absorption and the emission of 2 are assigned to
MLCT states.
˚
˚
4.881–5.001 A, H ꢀ ꢀ ꢀ pcentroid distances of 2.63–2.90 A, and
dihedral angles of 79.878–76.268, as shown in Fig. S2 in the
Supplementary Material, and C–H ꢀ ꢀ ꢀ O hydrogen bonds
Supplementary Material
CCDC 942992, 941587 and 942993 contain the supplementary
crystallographic data for compounds 1 3. These data can be
obtained free of charge at http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (þ44)
1223–336–033; or email: deposit@ccdc.cam.ac.uk
]
˚
˚
(H ꢀ ꢀ ꢀ O: 2.54 and 2.58 A, C ꢀ ꢀ ꢀ O: 3.33 and 3.31 A).
It is worth noting that the bridging ligand (pmb or pmbb)
adopts a trans coordination mode to link the two metal atoms
in all five compounds, forming an S-shaped building block,
and the pmb or pmbb of one S-shaped building block is parallel
to another neighbouring pmb or pmbb ligand from a different
S-shaped building block. In particular, complexes 1–3 are
organised into 1D tape-like arrays by intermolecular p ꢀ ꢀ ꢀ p
interactions, in which the ordered-layer-lattice anions in 2 and 3
are located between these arrays.
Intermolecular C–H ꢀ ꢀ ꢀ p interactions for compounds 1 and
3 are shown in Figs S1 and S2 on the Journal’s website.
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