Synthesis and structures of pyridinecarboxylate-containing zinc(II) complexes in dien and tren system

Article abstract of DOI:10.1016/j.ica.2010.09.035

Four new zinc(II) complexes [Zn(dien)(μ-nic)]₂(BPh ₄)₂·2CH₃OH (1), {[Zn(dien)(isonic)] BPh₄}_n (2), [Zn(tren)(nic)]BPh₄ (3) and [Zn(tren)(isonic)]BPh₄ (4) (dien/tren =

Full text of DOI:10.1016/j.ica.2010.09.035

Inorganica Chimica Acta 365 (2011) 325–332
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis and structures of pyridinecarboxylate-containing zinc(II) complexes in
dien and tren system
⇑
Feng-Mei Nie , Tao Fang, Shuang-Yan Wang, Hong-Yu Ge
Department of Chemistry, Capital Normal University, Beijing 100048, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Four new zinc(II) complexes [Zn(dien)(
l
-nic)]2(BPh4)2ꢀ2CH3OH (1), {[Zn(dien)(isonic)]BPh4}n (2),
Received 27 April 2010
Received in revised form 16 September
2010
Accepted 22 September 2010
Available online 29 September 2010
[Zn(tren)(nic)]BPh4 (3) and [Zn(tren)(isonic)]BPh4 (4) (dien/tren = diethylenetriamine/triethylenetri-
amine, nic/isonic = nicotinate/isonicotinate anion) were synthesized and structurally characterized by
IR, 1H NMR and single crystal X-ray diffraction. In the zinc(II) complexes of dien, both nicotinate and iso-
nicotinate connect the zinc(II) ions via N,O-bis-monodentate mode. Complex 1 contains a centrosymmet-
ric dinuclear unit bridged by two nicotinate anions in anti-parallel way. Complex 2 is characterized by an
infinite one-dimensional zigzag chain bridged by isonicotinate anion in an end-to-end mode. The ZnꢀꢀꢀZn
distance is 6.782 for 1 and 8.805 Å for 2. While in the complexes of tren, both 3 and 4 are mononuclear
complexes with nicotinate and isonicotinate coordinated to zinc(II) ion through only one oxygen atom of
their carboxylate groups. The zinc(II) ions in all of the four complexes are in a distorted trigonal bipyra-
midal geometry. Complex 3 forms a dinuclear unit and complex 4 forms an infinite 2D sheet structure
Keywords:
Zinc(II) complex
Nicotinic acid
Isonicotinic acid
Crystal structure
ꢁ
through intermolecular H-bonds. In all of the crystal lattices, the BPh4 counterions act to balance the
electronic charge at the same time to construct different 3D structures through noncovalent interactions
such as C–Hꢀꢀꢀ
p
, N–Hꢀꢀꢀ
p and van der Waals interactions.
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
carboxylate oxygen atoms can act as hydrogen acceptor to con-
struct 2D sheets [6,7] and 3D supramolecular networks [8]. The
bidentate coordination modes are reported in zinc complexes
through O,O-bis-monodentate (c and c0) and N,O-bis-monodentate
(d and d0) as bridges, in which nicotinic and isonicotinic acids link
the zinc atoms to yield 1D zigzag chain polymers [9–12], 2D bi-
layer [13], sandwich like structure [14], interpenetrating [15,16]
and 3D open framework [17]. In the tridentate coordination mode,
all of the two oxygen and one nitrogen atoms coordinate to zinc
Much effort has been devoted to the design and synthesis of
metal–organic coordination networks which show special network
topologies and potentially interesting properties [1–5]. Pyridine-
carboxylate ligands bearing both anionic and neutral donors have
been frequently employed to construct multidimensional coordi-
nation networks since they have rich coordination modes
(Scheme 1) and can take part in covalent bonds through the nitro-
gen atom of the pyridine ring and the oxygen atoms of the carbox-
ylate group, at the same time form extensive hydrogen bonding
interactions. As a good building block, complexes of anions of
nicotinic acid (3-pyridine carboxylic acid) and isonicotinic acid
(3-pyridine carboxylic acid) are able to form various lattice species,
through its coordination to metal ions. A number of zinc-pyridine-
carboxylate (nicotinate/isonicotinate) complexes with different
structures have been reported in the last twenty years.
atoms via
l
-O,O,N-tridentate (e and e0) or N-monodentate and
O,O0-chelate modes (f and f0) as seen in these polymers, displaying
2D bilayer structures [13], interpenetrating frameworks [15,16,18],
3D sandwich polymeric network [19,20] and open-framework
coordination polymer [21].
Till now, much of the work has focused mainly on the systems
containing only nicotinate or isonicotinate or both. Little attention
has been devoted to zinc-pyridinecarboxylate complexes in mixed
ligand system. Only a few of zinc(II) complexes containing ancil-
lary ligand such as tetrazolate [22], 1,4,7,10-tetraazacyclododecane
As monodentate ligand, nicotinic and isonicotinic acids coordi-
nate to zinc ion as anions via one of the pyridinecarboxylate oxy-
gen atoms (a and a0) or through the pyridine N atoms (b and b0).
Such coordination modes were often found in mononuclear com-
plexes. In this case the uncoordinated pyridine nitrogen atoms or
2ꢁ
(cyclen) [23], Schiff base macrocycle [14] and C2O4 [24] have
been reported.
We are interested in the preparation of zinc(II) nicotinate/iso-
nicotinate complexes containing dien and tren as main ligand for
the following reasons. First we would like to study how the struc-
tural change of the main ligands from linear tridentate dien to
⇑
Corresponding author. Tel./fax: +86 10 68902320.
E-mail address: niefm@mail.cnu.edu.cn (F.-M. Nie).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.09.035

326
F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 325–332
2.3. Preparation of complexes
2.3.1. Preparation of [Zn(dien)(
l
-nic)]2(BPh4)2ꢀ2CH3OH (1)
Zn(nic)2ꢀ4H2O (191 mg, 0.5 mmol) was added to a solution of
diethylenetriamine (51 mg, 0.5 mmol) in 10 ml MeOH. After
0.5 h, a methanol solution (10 ml) of sodium tetraphenylborate
(171 mg, 0.5 mmol) was added. Colorless crystals suitable for
X-ray structure determination were obtained after one week.
(Yield: 190 mg, 59%). Anal. Calc. for C70H82B2N8O6Zn2: C, 65.49;
H, 6.44; N, 8.73. Found: C, 65.57; H, 9.06; N, 6.23%. FT-IR (KBr,
cmꢁ1): 3436(m), 3299(s), 3255(vs), 3054(m), 3003(m), 2939(m),
2873(m), 1627(vs), 1580(m), 1479(m), 1455(w), 1427(m),
1368(vs), 1086(m), 738(vs), 712(vs), 605(m). 1HNMR (300 MHz,
DMSO-d6, d): 9.09, 8.65, 8.22, 7.47 (4H, pyridine), 7.16, 6.91, 6.77
(20H, benzolyl), 3.55–3.65, (5H, 1ꢂ NH, 2ꢂ NH2), 3.55, (1H, NH),
2.47–2.68, (8H, 4ꢂ CH2).
Scheme 1. The coordination modes of nicotinic and isonicotinic acid (upper-
bottom).
2.3.2. Preparation of {[Zn(dien)(isonic)]BPh4}n (2)
Complex 2 was prepared by the same way as 1, except that
Zn(isonic)2ꢀ4H2O (191 mg, 0.5 mmol) was used. (Yield: 155
mg, 51%). Anal. Calc. for C34H37N4O2ZnB: C, 66.96; H, 6.11; N,
9.19. Found: C, 66.89; H, 6.07; N, 9.30%. FT-IR(KBr, cmꢁ1):
3435(m), 3328(s), 3297(vs), 3258(vs), 3052(vs), 2998(s), 2863(m),
1625(vs), 1578(vs), 1556(vs), 1478(s), 1426(s), 1417(s), 1384(vs),
1057(m), 1032(m), 930(m), 746(s), 707(vs), 605(m). 1HNMR
(300 MHz, DMSO-d6, d): 8.68, 7.80 (4H, pyridine), 7.18, 6.93, 6.79
(20H, benzolyl), 3.57–3.67 (5H, 1ꢂ NH, 2ꢂ NH2), 2.48–2.69 (8H,
4ꢂ CH2).
tripodal tetradentate tren affect the coordination modes of nicotin-
ate/isonicotinate as coligands. Secondly, each dien or tren contains
two or three NH2 groups. When the complexes of dien and tren
were formed, the coordinated NH2 groups of dien or tren may act
as hydrogen donors, the uncoordinated oxygen atom or nitrogen
atom of the pyridine ring of nicotinate/isonicotinate and the coun-
ꢁ
ter anions BPh4 as hydrogen acceptor, noncovalent interactions
such as C–Hꢀꢀꢀ
p
, N–Hꢀꢀꢀ
p and van der Waals interactions may afford
interesting supramolecular coordination assembly. The third is
that the second ligand nicotinate and isonicotinate are positional
isomers with both N and O donor atoms. The different orientation
of the two bonding sites would affect the construction of the final
crystal structure. Herein we report the synthesis and crystal struc-
2.3.3. Preparation of [Zn(tren)(nic)]BPh4 (3)
Complex 3 was prepared by the same way as 1, except that
triethylenetriamine (73 mg, 0.5 mmol) was used (51 mg, 0.5 mmol).
(Yield: 212 mg, 65%). Anal. Calc. for C36H42N5O2ZnB: C, 66.22;
H, 6.48; N, 10.73. Found: C, 65.92; H, 6.46; N, 10.74%. FT-IR (KBr,
cmꢁ1): 3416(m), 3300(s), 3263(vs), 3129(m), 3055(s), 2996(m),
2952(m), 2863(w), 1621(vs), 1597(m), 1479(m), 1374(vs),
1061(m), 982(m), 843(m), 736(vs), 709(vs), 605(m), 523(w). 1HNMR
(300 MHz, DMSO-d6, d): 9.04, 8.60, 8.17, 7.41 (4H, pyridine), 7.17,
6.92, 6.78 (20H, benzolyl), 3.79 (6H, 3ꢂ NH2), 2.57–2.60 (12H, 6ꢂ
CH2).
tures of four zinc(II) complexes [Zn(dien)(
l
-nic)]2(BPh4)2ꢀ2CH3OH
(1), {[Zn(dien)(isonic)](BPh4)}n (2), [Zn(tren)(nic)]BPh4 (3) and
[Zn(tren)(isonic)]BPh4 (4) (Scheme 2), where [Zn(dien)]2+
,
[Zn(tren)] 2+ units are linked by nicotinate and isonicotinate. Inter-
estingly, these zinc complexes exhibit different structures from
dinuclear complex, 1D chain to mononuclear complexes.
2. Experimental
2.3.4. Preparation of [Zn(tren)(isonic)]BPh4 (4)
Complex 4 was prepared by the same way as complex 1. (Yield:
196 mg, 60%). Anal. Calc. for C36H42N5O2ZnB: C, 66.22; H, 6.48; N,
10.73. Found: C, 66.32; H, 6.28; N, 10.66%. FT-IR (KBr, cmꢁ1):
3299(vs), 3258(vs), 3144(s), 3057(vs), 2960(s), 2867(s), 1624(vs),
1597(vs), 1580(s), 1549(s), 1480(s), 1385(vs), 1314(m), 1269(m),
1077(vs), 1058(vs), 1001(s), 984(s), 882(m), 732(vs), 708(vs),
681(s), 613(s), 529(m). 1HNMR (300 MHz, DMSO-d6, d): 8.63, 7.75
(4H, pyridine), 7.17, 6.92, 6.83 (20H, benzolyl), 3.80 (6H, 3ꢂ
NH2), 2.57–2.60 (12H, 6ꢂ CH2).
2.1. Materials
All chemicals were of analytical grade and used without further
purification. Sodium nicotinate and sodium isonicotinate were
synthesized by reaction of nicotinic and isonicotinic acids with a
stoichiometric amount of NaOH in water. Zn(nic)2ꢀ4H2O and
Zn(isonic)2ꢀ4H2O were obtained as white precipitate by reaction
of ZnSO4ꢀ7H2O and sodium nicotinate and sodium isonicotinate,
respectively.
2.4. X-ray structural analysis
2.2. Physical measurements
All measurements were made on detectors using graphite-
IR spectra were recorded as KBr pellets on Bruker TENSOR 27
FT-IR spectrometer in the range of 4000–400 cmꢁ1. Elemental
analyses for C, H and N were performed on a Perkin-Elmer 240C
analyzer. 1H NMR spectra were recorded on a Varian Mercury-Plus
300 NMR spectrometer using DMSO-d6 solution.
monochromated Mo Ka radiation (k = 0.71073 Å) at 293(2) K with
NONIUS KappaCCD for 1 and 4, Rigaku R-AXIS RAPID IP Area for
complex 2 and Bruker P4 diffractometer for 3. The raw data for
the structures were processed using RAPID AUTO and absorption
corrections were applied using Kappa CCD and multi-scan for 1
Scheme 2. The reaction scheme for 1–4.

F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 325–332
327
Table 1
Summary of the crystal data and structure refinements for complexes 1–4.
1
2
3
4
Empirical formula
Formula weight
Crystal size (mm)
Crystal system
Space group
a (Å)
C
70H82N8O6Zn2B2
C34H37N4O2ZnB
609.88
C36H42N5O2ZnB
652.95
C36H42N5O2ZnB
652.95
1283.84
0.19 ꢂ 0.33 ꢂ 0.55
monoclinic
P21/c (no. 14)
14.3910(2)
10.5111(2)
22.1889(4)
90
98.3510(9)
90
3320.82(10)
1.284
0.26 ꢂ 0.35 ꢂ 0.51
monoclinic
P21 (no. 4)
9.9755(4)
10.2081(3)
15.5449(6)
90
102.0870(10)
90
1547.86(10)
1.309
0.30 ꢂ 0.40 ꢂ 0.40
monoclinic
P21/c (no. 14)
18.389(5)
10.2143(10)
19.962(4)
90
111.502(12)
90
3488.5(13)
1.243
0.10 ꢂ 0.20 ꢂ 0.50
triclinic
ꢀ
P1 (no. 2)
11.0459(2)
17.6189(3)
18.2271(3)
68.8638(9)
87.2782(9)
85.8057(7)
3298.94(10)
1.315
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
qcalc (gꢀcmꢁ3
)
Z
2
2
4
4
F(0 0 0)
l
1352
0.779
640
0.830
1376
0.742
1376
0.784
(mmꢁ1
)
Tmax /Tmin
0.879/0.715
0.8131/0.6769
0.800/0.733
0.927/0.857
hkl Range
ꢁ18 to 18
ꢁ13 to 13
ꢁ28 to 28
3.5–27.5
ꢁ12 to12
–13 to 13
–20 to 20
2.7–27.5
ꢁ1 to 21
ꢁ12 to 1
ꢁ23 to 22
2.1–25.0
ꢁ14 to 14
ꢁ22 to 22
ꢁ23 to 23
3.4–27.5
h Range (°)
Measured reflections
42378
6983
7581
64919
Unique reflections (Rint
Observed reflections I > 2r(I)
)
7557, 0.082
4578
6983, 0.000
5672
6142, 0.060
2998
14875, 0.088
7852
Data/restraints/parameters
7557/0/400
1.01
0.0431/0.0817
0.0995/0.0967
0.22/ꢁ0.42
6983/1/380
0.934
0.0313/0.0685
0.0410/0.0710
0.291/ꢁ0.285
6142/0/406
1.00
0.0610/0.0973
0.1458/0.1193
0.32/ꢁ0.39
14875/0/812
0.97
0.0431/0.0777
0.1292/0.0946
0.34/ꢁ0.32
Goodness-of-fit
b
R1a/wR2 (I > 2
r(I))
R1/wR2 (all data)
Resid. el. dens. (e Åꢁ3
)
R1
=
R
||F0| ꢁ |Fc||/
R
|F0|, wR2 = [
R
w(F20 ꢁ F2c )2/
R .
w(F20)2]1/2
Table 2
Selected bond lengths (Å) and angles (°) for complexes 1 and 2.
Complex 1
Complex 2
Distances (Å)
Zn1–N1
Zn1–N2
Zn1–N3
Zn1–N4
Zn1–O1ai
2.0508(17)
2.1923(17)
2.0812(18)
2.1820(17)
1.9835(15)
2.085(2)
2.177(2)
2.100(2)
2.151(2)
1.9776(19)
Angles (°)
N1–Zn1–N3
O1ai–Zn1–N3
O1ai–Zn1–N1
N2–Zn1–N4
N1–Zn1–N2
N1–Zn1–N4
N2–Zn1–N3
N3–Zn1–N4
O1ai–Zn1–N2
O1ai–Zn1–N4
122.87(8)
120.22(7)
115.45(7)
171.25(7)
82.12(7)
102.92(7)
80.69(7)
90.56(7)
95.81(7)
88.50(6)
120.80(10)
138.38(9)
99.27(10)
173.83(9)
82.51(9)
103.03(9)
80.74(10)
93.95(9)
Fig. 1. The cation structure of complex 1 with 30% thermal ellipsoids.
94.87(9)
86.99(10)
and 4,
W-scan for complex 2, XSCANS and W-scan for 3. All of the
Symmetry operation for used to generate equivalent atoms. For 1: i = 1 ꢁ x, 1 ꢁ y,
1 ꢁ z; for 2: i = 1 ꢁ x, ꢁ1/2 + y, 2 ꢁ z; ii = 1 ꢁ x, 1/2 + y, 2 ꢁ z.
structures were solved primarily by direct method and secondly by
Fourier difference technique and then refined using full-matrix
least-squares based on F2 using the SHELXL-97 [25,26]. Anisotropic
thermal parameters were applied to all non-hydrogen atoms.
Hydrogen atoms were located geometrically and refined using
the riding model (C–H = 0.96 Å, N–H = 0.86 Å). Graphics were com-
puted with Bruker SHELXL-97. Crystal data for the complexes are
summarized in Table 1.
ylborate anions and two methanol molecules. The cation structure
of complex 1 is shown in Fig. 1. Relevant bond distances and angles
are listed in Table 2. Selected hydrogen bond parameters for com-
plex 1, 3 and 4 are given in Table 3. The two zinc(II) ions are
bridged by two nicotinate anions in anti-parallel way through
N,O-bis-monodentate coordination mode (Scheme 1, mode d) with
ZnꢀꢀꢀZn distance of 6.782 Å. Each zinc(II) atom is five-coordinated
to three N atoms of dien and one carboxylate O atom of nicotinate
and one pyridine N atom of another nicotinate. The coordination
geometry of zinc(II) ion is best describted as distorted trigonal
3. Results and discussion
3.1. [Zn(dien)(
l
-nic)]2(BPh4)2ꢀ2CH3OH (1)
X-ray crystal structure analysis shows that complex 1 consists
bipyramidal geometry with = 0.81, according to the angular
s
of a centrosymmetric [Zn2(dien)2(
-nic)2]2+ cation, two tetraphen-
l
structural parameter = (b-a)/60) [27]. The trigonal plane is
s
(s

328
F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 325–332
Table 3
Selected hydrogen bond lengths (Å) and angles (°) of complexes 1, 3 and 4.
Compound
1
D–HꢀꢀꢀA
D–H
HꢀꢀꢀA
DꢀꢀꢀA
\D–HꢀꢀꢀA
Symmetry code
N2–H2ꢀꢀꢀO2
0.91
0.82
0.90
0.90
0.90
0.90
0.90
0.90
2.22
2.02
2.22
2.06
2.14
2.35
2.29
2.28
2.995(2)
2.840(3)
3.102(8)
2.954(3)
2.971(3)
2.882(3)
3.170(3)
3.146(3)
143
179
165
176
153
118
166
162
1 ꢁ x, 1 ꢁ y, 1 ꢁ z
1 ꢁ x, 1 ꢁ y, 1 ꢁ z
ꢁx, 2 ꢁ y, 2 ꢁ z
O3–H3ꢀꢀꢀO2
3
4
N4–H4BꢀꢀꢀN5
N1–H1AꢀꢀꢀN10
N1–H1BꢀꢀꢀO2
N2–H2AꢀꢀꢀO2
N7–H7AꢀꢀꢀN5
N7–H7BꢀꢀꢀO4
1 ꢁ x, ꢁy, 1 ꢁ z
1 + x, y, z
2 ꢁ x, ꢁy, 2 ꢁ z
defined by two primary amine N1, N3 atoms of dien and the car-
boxylate O1 atom of nicotinate, with the central zinc(II) ions lying
out of the trigonal plane toward N2 atom by 0.144 Å. The bond
distances in the trigonal plane are 2.0508(17) Å for Zn–N1,
2.0812(18) Å for Zn–N3 and 1.9835(15) Å for Zn–O1. The bond an-
gles in the trigonal plane are in the range of 115.45(7)–122.87(8)°.
The apical positions are occupied by the secondary amine N2 atom
of dien and pyridine N4 atom of nicotinate with bond distances to
be 2.1923(17) Å for Zn–N2 and 2.1820(17) Å for Zn–N4. The bond
angle of N2–Zn–N4 is 171.25(7)°.
uncoordinated carboxylate O2 atoms via intramolecular [N2–
H2ꢀꢀꢀO2 = 2.995(2) Å, \N2–H2ꢀꢀꢀO2 = 143°] and intermolecular
H-bonds [O3–H3ꢀꢀꢀO2 = 2.840(3) Å, \O3–H3ꢀꢀꢀO2 = 179°], forming
two six-membered rings besides the central dinuclear twelve-
membered ring (Fig. 2). The BPh4 counterions in the crystal lattice
act to balance the electronic charge, at the same time contribute to
form 3D structure through a lots of noncovalent interactions such
ꢁ
as C–Hꢀꢀꢀ
p
, N–Hꢀꢀꢀ
p and van der Waals interactions (Fig. 3).
3.2. {[Zn(dien)(isonic)]BPh4)}n (2)
It’s worth noting that the secondary amine N2 atom of dien and
O3 atom of methanol serve as H-donors and interact with the
X-ray crystallography shows that complex 2 is a one-dimen-
sional zigzag chain. Relevant bond distances and angles are listed
in Table 2. The coordination geometry of zinc(II) ion is distorted tri-
gonal bipyramid (s = 0.59), with the trigonal plane formed by two
primary N1, N3 atoms of dien and one carboxylate O1 atom of iso-
nicotinate, and the apical positions are occupied by the secondary
amine N2 atom of dien and the pyridine N4 atom of another isonic-
otinate (Fig. 4). The distortion from the idealized trigonal bipyra-
midal geometry of 2 is more severe than 1 which reflects on the
O–Zn–N angles of the trigonal plane 99.27(10)–138.38(9)° for 2
and 115.45(7)–120.22 (7)° for 1. As expected, the central Zn2+ lies
out of the trigonal plane toward N2 atom by 0.268 Å for 2, which is
almost two times longer than that of 1 (0.144 Å). The bond dis-
tances in the trigonal plane are 2.085(2) Å for Zn–N1, 2.100(2) Å
for Zn–N3 and 1.9776(19) Å for Zn–O1A. The bond distances in
the apical position are 2.177(2) Å for Zn–N2 and 2.151(2) Å for
Zn–N4. In complex 2, isonicotinate anion acts as bis-monodentate
ligand (mode d0) to connect the adjacent zinc (II) ions in an end-to-
end bridging mode, which generates a polymeric infinite 1D zigzag
covalently bonded chain with the ZnꢀꢀꢀZn distance of 8.805 Å
Fig. 2. Hydrogen bonds in [Zn2(dien)2(l
-nic)2]2+ of complex 1.
Fig. 3. Packing view of complex 1.

F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 325–332
329
Fig. 4. The molecular structure of complex 2 with 30% thermal ellipsoids.
Fig. 7. The cation structure of complex 3 with 30% thermal ellipsoids.
(Fig. 5). The chains propagate parallel to the crystallographic a-axis
while the chains are stacked one upon another parallel alone b-
axis. 3D supramolecular structure was formed by BPh4 anions
otinate and isonicotinate are different. Nicotinate and isonicotinate
are position isomers. Nicotinate is 3-pyridine carboxylic acid, it is
bent. Two nicotinates bridged the two [zinc(dien)]2+ units in anti-
parallel coordination mode to form a dinuclear zinc complex. Iso-
nicotinate is 4-pyridinecarboxylic acid, it is linear. The adjacent
[zinc(dien)]2+ units were connected by isonicotinate via end to
end mode to form zigzag chain structure. Distinct spatial structural
ꢁ
among the chains through C–Hꢀꢀꢀ
p, N–Hꢀꢀꢀ
p and van der Waals
interactions (Fig. 6).
It should be emphasized that complexes 1 and 2 are obtained
from similar reaction condition, except that the second ligands nic-
Fig. 5. 1D chain of complex 2 (BPh4ꢁ omitted for clarity).
Fig. 6. Packing view of complex 2.

330
F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 325–332
Table 4
Selected bond lengths (Å) and angles (°) for complex 3.
Distances (Å)
Zn1–N1
Zn1–O1
Zn1–N3
2.321(4)
1.999(3)
2.067(4)
Zn1–N2
Zn1–N4
2.041(4)
2.057(4)
Angles (°)
O1–Zn1–N1
O1–Zn1–N3
N1–Zn1–N2
N1–Zn1–N4
N2–Zn1–N4
169.21(15)
94.73(15)
80.00(15)
79.65(17)
118.49(18)
O1–Zn1–N2
O1-Zn1–N4
N1–Zn1-N3
N2–Zn1-N3
N3–Zn1–N4
110.65(15)
96.08(17)
79.61(15)
109.20(17)
122.92(19)
Fig. 10. The cation structure of complex 4 with 30% thermal ellipsoids.
Table 5
Selected bond lengths (Å) and angles (°) for complex 4.
Distances (Å)
Zn1–N1
Zn1–O1
Zn1–N2
Zn1–N3
Zn1–N4
2.034(2)
2.0539(15)
2.049(2)
2.053(2)
2.3018(18)
Zn2–N6
Zn2–O3
Zn2–N7
Zn2–N8
Zn2–N9
2.051(2)
2.0094(16)
2.049(2)
2.071(2)
2.2654(18)
Angles (°)
O1–Zn1–N3
N1–Zn1–N2
N1–Zn1–N4
N2–Zn1–N4
O1–Zn1–N2
O1–Zn1–N4
N1–Zn1–N3
N2–Zn1–N3
N3–Zn1–N4
O1–Zn1–N1
95.50(7)
113.95(8)
80.73(7)
80.27(8)
98.85(7)
173.60(7)
116.05(9)
121.52(9)
79.72(7)
105.32(7)
N8–Zn2–N9
O3–Zn2-N8
O3–Zn2–N7
N6–Zn2-N7
N6–Zn2–N8
O3–Zn2–N6
O3–Zn2–N9
N7–Zn2–N8
N7–Zn2-N9
N6–Zn2–N9
81.19(8)
97.30(8)
107.04(8)
121.06(9)
120.45(9)
93.40(7)
171.48(7)
111.08(9)
81.24(7)
80.31(7)
Fig. 8. A dinuclear sixteen-member ring unit constructed by hydrogen bonds.
atom of nicotinate. The coordination geometry of zinc(II) ion is
more close to trigonal bipyramid with = 0.77. Three primary
features in complexes 1 and 2 were resulted from the positional
isomers.
s
N2, N3, N4 atoms of tren make up the trigonal plane with Zn2+
ion deviated from the trigonal plane toward N1 by 0.375 Å. The
equatorial bond distances are 2.041(4) Å for Zn1–N2, 2.067(4) Å
for Zn1–N3 and 2.057(4) Å for Zn1–N4. The equatorial bond angles
are in the range of 109.20(17)–122.92(19)°. The axial positions are
occupied by the N1 atom of tren and the carboxylate O1 atom of
nicotinate with bond distances to be 2.321(4) Å for Zn1–N1 and
1.999(3) Å for Zn1–O1. The bond angle of N1–Zn1–O1 is
3.3. [Zn(tren)(nic)]BPh4 (3)
Complex 3 consists of one [Zn(tren)(nic)]+ cation and one tetra-
phenylborate anion. The cation structure of 3 is shown in Fig. 7,
relevant bond distances and angles are listed in Table 4. The zinc(II)
ion is coordinated with four N atoms of tren and one carboxylate O
Fig. 9. Packing view of complex 3.

F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 325–332
331
169.21(15)°. The axial bond distance of Zn1–N1 is significantly
longer than the equatorial Zn–N distances. This has also been ob-
served in other zinc complexes of tren [28]. In complex 3, nicotin-
ate coordinated to the central zinc(II) ion in a monodentate fashion
(mode a).
In complex 3, the uncoordinated pyridine N5 atom of nicotinate
accepts the hydrogen atom H5(N4) of the primary amine of tren by
intermolecular hydrogen bonds (N4–H4ꢀꢀꢀN5 = 3.102(8) Å, \N4-
H4ꢀꢀꢀN5 = 165°), which forms a dinuclear cation (Fig. 8). The ZnꢀꢀꢀZn
distance is 7.667 Å, which is about 1 Å longer than that of dinuclear
cation of 1. As the same as complexes 1 and 2, the weak interac-
formed by N1, N2 and N3 atoms of tren for Zn1, N6, N7 and N8
atoms of tren for Zn2. The axial positions are occupied by N4 atom
of tren and the carboxylate O1 atom for Zn1 and N9 atom of
tren and O3 atom of isonictinate for Zn2. The zinc(II) ions are
deviated from the trigonal planes toward N4, N9 by 0.350 and
0.333 Å. The bond distances [Zn1–N4 = 2.3018(18) Å and Zn2–
N9 = 2.2654(18) Å] in the axial positions are much longer than
those in the equatorial plane, which are in the range of 2.034(2)–
2.053(2) Å and 2.049(2)–2.071(2) Å for Zn1 and Zn2, respectively.
The most striking feature is that isonicotinate coordinated to zin-
c(II) ion through only one of its carboxylate oxygen atoms in
monodentate fashion (mode a0).
tions such as C–Hꢀꢀꢀ
p
, N–Hꢀꢀꢀ
p
interactions and van der Waals inter-
ꢁ
actions are observed between the cations and BPh4 anions. 3D
supramolecular structure (Fig. 9) is formed through these
interactions.
The two crystallographically independent Zn1 and Zn2 units
were connected to form a tetranuclear unit (Fig. 11) through inter-
molecular hydrogen bonds [N–HꢀꢀꢀO = 2.882(3)–3.146(3) Å, \N–
HꢀꢀꢀO = 118–162°) and N–HꢀꢀꢀN = 2.954(3)–3.170(3) Å, \N–HꢀꢀꢀN =
166–176°)], which are further connected through intermolecular
hydrogen bonds between the primary N7 atom of tren and the pyr-
idine N5 atom to generate an infinite 2D sheet structure (Fig. 12).
3.4. [Zn(tren)(isonic)]BPh4 (4)
As shown in Fig. 10, there are two crystallographically indepen-
dent but chemical identical cations in complex 4. Relevant bond
distances and angles are listed in Table 5. Each of the zinc(II) ions
is coordinated with four N atoms of tren and one carboxylate O
atom of isonicotinate in distorted trigonal bipyramidal geometry
ꢁ
BPh4 anions fill up the whole grids and stabilize the final 3D
structure through a serial C–Hꢀꢀꢀ
p, N–Hꢀꢀꢀ
p interactions and van
der Waals interactions.
4. Conclusion
with
s = 0.87 for Zn1 and 0.84 for Zn2. The equatorial plane is
In this work, four zinc(II) complexes containing nicotinate or
isonicotinate in mixed tren/dien ligand system were prepared
and characterized. In the above complexes, nicotinate and isonico-
tinate exhibit different coordination modes as seen in 1 and 2 via
N,O-bis-monodentate, while in 3 and 4 via O-monodentate. In the
zinc(II) complexes of dien, both nicotinate and isonicotinate con-
nect the zinc(II) ions via N,O-bis-monodentate mode to form a
dinuclear complex 1 and an infinite 1D chain structure 2. While
in the tren system, both 3 and 4 are mononuclear complexes with
nicotinate and isonicotinate coordinated to zinc(II) ion through
only one oxygen atom of their carboxylate groups. Multidentate
ligand dien/tren and methanol molecules could function as hydro-
gen bonding donors, extensive N–HꢀꢀꢀO, O–HꢀꢀꢀO hydrogen bonds
play dominant role in the construction of the final 3D supramole-
cules. These noncovalent interactions such as hydrogen bonds,
Fig. 11. An infinite 2D sheet based on intra- and inter-molecular hydrogen bonds.
C–Hꢀꢀꢀ
p, N–Hꢀꢀꢀ
p interactions and van der Waals interactions will
Fig. 12. Packing view of complex 4.

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F.-M. Nie et al. / Inorganica Chimica Acta 365 (2011) 325–332
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[10] G.-F. Chen, C.-Z. Cao, J. Coord. Chem. 61 (2008) 262.
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This study was supported by Beijing Natural Science Founda-
tion (Grant No. 2092010), Beijing Municipal Education Commission
Research Program (KM200810028009) and the Scientific Research
Foundation for Returned Overseas Chinese Scholars, Beijing Muni-
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CCDC 712888, 712891, 712890 and 712889 contain the supple-
mentary crystallographic data for complexes 1, 2, 3 and 4, respec-
tively. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.ica.2010.09.035.
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