Synthesis and structural characterization of organotin(IV) carboxylates based on different heterocyclic substituents

Article abstract of DOI:10.1016/j.poly.2011.10.032

Six novel organotin(IV) carboxylates have been successfully synthesized, namely, the polymer (C₆H₅)₃Sn(L1) _∞ (1) [HL1 = 4-imidazolyl benzoic acid], the mononuclear (C₆H₅)₃Sn(L2) (2) [HL2 = 4-pyrazolylbenzoic acid], (C₆H₅)₃Sn(L3)·CH₃OH (3) [HL3 = 4-triazolylbenzoic acid] and (C₆H₅) ₃Sn(L4) (4) [HL4 = 4-tetrazolyl benzoic acid] and the tetranuclear [(n-Bu₂Sn)₄(L2)₂O₂(OCH ₃)₂] (5) and [(n-Bu₂Sn)₄(L3) ₂O₂(OCH₃)₂] (6). X-ray diffraction analyses show 1D infinite chain of polymer 1, single molecular structures of isomorphous complexes 2 and 4, single molecule structures of complex 3 containing solvent CH₃OH molecule and similar ladder-type structures of complexes 5 and 6. The photoluminescence of ligands and 1-6 were also measured in the solid state at room temperature.

Full text of DOI:10.1016/j.poly.2011.10.032

Polyhedron 31 (2012) 738–747
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis and structural characterization of organotin(IV) carboxylates based on
different heterocyclic substituents
a
a
a
a
Wen-Qian Geng a,d, Hong-Ping Zhou a, , Long-Huai Cheng , Fu-Ying Hao , Guo-Yi Xu , Fei-Xia Zhou ,
⇑
Zhi-Peng Yu a, Zheng Zheng a, Jian-Qing Wang a, Jie-Ying Wu a, Yu-Peng Tian a,b,c,
⇑
a Department of Chemistry, Anhui University, Key Laboratory of Functional Inorganic Materials Chemistry of Anhui Province, 230039 Hefei, PR China
b State Key Laboratory of Coordination Chemistry, Nanjing University, 210093 Nanjing, PR China
c State Key Laboratory of Crystal Materials, Shandong University, 250100 Jinan, PR China
d College of Economy & Technology, Anhui Agricultural University, 230036 Hefei, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 14 July 2011
Accepted 30 October 2011
Available online 15 November 2011
Six novel organotin(IV) carboxylates have been successfully synthesized, namely, the polymer
(C6H5)3Sn(L1) (1) [HL1 = 4-imidazolyl benzoic acid], the mononuclear (C6H5)3Sn(L2) (2) [HL2 = 4-pyraz-
1
olylbenzoic acid], (C6H5)3Sn(L3)ꢀCH3OH (3) [HL3 = 4-triazolylbenzoic acid] and (C6H5)3Sn(L4) (4)
[HL4 = 4-tetrazolyl benzoic acid] and the tetranuclear [(n-Bu2Sn)4(L2)2O2(OCH3)2] (5) and [(n-Bu2Sn)4-
(L3)2O2(OCH3)2] (6). X-ray diffraction analyses show 1D infinite chain of polymer 1, single molecular
structures of isomorphous complexes 2 and 4, single molecule structures of complex 3 containing solvent
CH3OH molecule and similar ladder-type structures of complexes 5 and 6. The photoluminescence of
ligands and 1–6 were also measured in the solid state at room temperature.
Keywords:
Organotin(IV) carboxylates
Heterocyclic substituents
Crystal structure
Ó 2011 Published by Elsevier Ltd.
Photoluminescence
1. Introduction
synthetic variations from organotin compounds. Several novel
cluster types such as ladder, drum, O-capped, cube, butterfly,
The heterocyclic NO donor ligands play an important role in the
development of coordination chemistry as they readily form com-
plexes with most of metal ions [1–4]. The synthesis, structure and
properties of coordination complexes still arouse considerable re-
search interests because of their potential applications in material
science [5]. Carboxylic acid is often used group for constructing
new coordination compounds [6], in part because their various
interactions to a single metal center or bridging interactions with
multiple metal centers results in diverse topologies [7]. In addition,
carboxylic acid can be used to assemble supramolecular structures
through their ability to act as hydrogen bond acceptors and donors
[8]. Likewise, pyrazole, imidazole, triazole and tetrazole heterocy-
clic ligands are small and simple, yet effective as bridging organic
building blocks for coordination compounds [9]. A large number of
one-, two- and three-dimensional infinite frameworks with azoles
derivatives have been prepared and characterized because of the
interest in their novel topologies [10].
triply- and doubly bridged ladders, have been assembled and
structurally characterized [13]. Admittedly this field is quite
nascent, but the recent results in this area are quite exciting.
In this contribution, six novel organotin(IV) carboxylates 1–6 were
obtained by four carboxylic acids containing different azole groups and
organotin [14]. The X-ray diffraction analysis reveal that both O donor
atom and N donor atom take part in coordination with central metal Sn
atom, which forms polymer 1 as a 1D infinite chain. While in the other
five complexes, Sn only coordination with O donor atoms, which shows
discrete structures with their own character. This work also provides
useful information on the photoluminescence of these ligands and
organotin complexes in the solid state.
2. Results and discussion
2.1. Crystal structure analysis
Among main-group organometallic compounds, organotin has
been receiving considerable attention in recent years [11], for some
of them are biologically active or have been used as reagents or
catalysts in organic reactions [12]. Furthermore, a surprisingly
large structural diversity can be achieved by relatively simple
2.1.1. Polymer 1
The X-ray single crystal reveals that polymer 1 is a successive
and uninterrupted entity. It crystallizes in the monoclinic with
space group P2(1)/c. The unit consists of one Sn atom connecting
three C from different phenyl rings, one O(1) atom from HL1 and
one N(1) atom from next HL1 as shown in Fig. 1(a). HL1 in polymer
1 indicates a severe distortion with the dihedral angles between
imidazole ring and the central phenyl unit to be 53.35°, while this
⇑
Corresponding authors. Tel.: +86 5515108151; fax: +86 5515107342.
E-mail addresses: zhpzhp@263.net (H.-P. Zhou), yptian@ahu.edu.cn (Y.-P. Tian).
0277-5387/$ - see front matter Ó 2011 Published by Elsevier Ltd.
doi:10.1016/j.poly.2011.10.032

W.-Q. Geng et al. / Polyhedron 31 (2012) 738–747
739
Fig. 1. (a) ORTEP diagram showing the structures of polymer 1. (b) The 1D linear chain of polymer 1 along the c-axis. (c) The 2D network of polymer 1 showing the weak
C–Hꢀ ꢀ ꢀO interactions along the b-axis, respectively. Only H atoms that were from hydrogen bonds were saved.
is 13.67° in the free ligand [15]. Thus it can be seen that HL1 was
change its planarity due to meeting the coordination requirements
of steric hindrance. The influence of the Sn(1)–N(1) coordination
bond causes the concomitant contraction in the tetrahedral angles
around the central Sn(1) of polymer 1 (the angles are 90.23°,
94.04°, and 97.54°, respectively). O(2) atom approaches the Sn(1)
atom at a distance of 3.310 Å, which is less than the sum of their
van der Waals radii for Sn and O atoms (3.680 Å) [16]. The coordi-
nation environment of polymer 1 has quite distorted trigonal
bipyramidal geometry. Polymer 1 form a 1D infinite chain by the
metal-bound peripheral imidazole-N(1) and carboxyl-O(1) running
along the c-axis (Sn(1)–N(1) = 2.620 Å, Sn(1)–O(1) = 2.164 Å) as
shown in Fig. 1(b). And then, 2D network is generated by lots of
1D linear chains, which connect to each other via hydrogen bonds
along the b-axis as seen from Fig. 1(c). The hydrogen bond is
between the non-coordinating O(2) atom and the phenyl substitu-
ent on the tin atom in an adjacent chain [d(C(13)ꢀ ꢀ ꢀO(2)) = 3.354 Å,
d(H(13)ꢀ ꢀ ꢀO(2)) = 2.630 Å, \(C(13)–H (13)ꢀ ꢀ ꢀO(2)) = 135.16°]. It is
observed from the ab-plane that the three phenyls substituent on
the tin atom in each neighboring chain are arranged as ‘‘clover’’,
positive and inverted positions are alternate along the a-axis. There
2.1.2. Complex 2
Complex 2 crystallizes in the monoclinic with space group P2(1)/
c and shows a discrete structurein accordance with the preference of
such structures for triphenyltin arylcarboxylates. HL2 in complex 2
indicates a smaller distortion with the dihedral angles between pyr-
azole ring and the central phenyl unit to be 15.42°. As shown in
Fig. 2(a), there is four coordinated bonds around central Sn atom,
namely, three Sn–Cph bonds and one Sn–Ocarboxyl bond. The bond
lengths of Sn(1)–C(11), Sn(1)–C(17) and Sn(1)–C(23) are 2.134,
2.114 and 2.138 Å, respectively, which are not sensitive to changes
of coordination. Moreover, the tetrahedral angles around the central
Sn (97.76°, 108.12° and 110.70°) are all in normal range [17]. Two
types of Sn–O bond lengths are found: Sn(1)–O(1) 2.058 Å and
Sn(1)–O(2) 2.725 Å. Actually, 2.725 Å is considered long for primary
Sn–O bonding, but represents a type of secondary interaction [18].
Complex 2 can be referred to an idealized geometry in which
the Sn is involved in four covalent bonds having a distorted tetra-
hedral geometry about the tin center, while the carboxyl oxygen
atom is involved in a fifth weaker bonding interaction with tin in
which it approaches a tetrahedral face. The pyrazolylbenzoic sys-
tem and the Sn–Cph bond opposite the aforementioned tetrahedral
face tend toward coplanarity. Therefor, in this structural represen-
tation, complex 2 was described as distorted trigonal-bipyramidal
geometry with five-coordinated tin center (Scheme 1) [19].
Weak interactions play significant roles in forming the topolog-
ical structures. Adjacent molecules are interacted with each other
through hydrogen bonds forming a 1D chain structure along the
a-axis (Fig. 2(b)). The oxygen atom of the ligand is the H bonding
is some evidence of a weak C–Hꢀ ꢀ ꢀ
of imidazole ring and the phenyl of ligand in an adjacent chain to
interactions be-
p interaction between C(2)–H(2)
be 3.130 Å. Besides, an additional weak C–Hꢀ ꢀ ꢀ
p
tween phenyls substituent on the tin and imidazole ring is
3.209 Å along the b-axis. The molecules of adjacent layers are
stacked as sandwich. Both the weak C–Hꢀ ꢀ ꢀ
p interactions contrib-
ute to stabilizing 3D architecture along the a-axis and b-axis.

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W.-Q. Geng et al. / Polyhedron 31 (2012) 738–747
Fig. 2. (a) ORTEP diagram showing the structures of complex 2. (b) The 1D chain of complex 2 showing C–Hꢀ ꢀ ꢀO interactions along the a-axis. (c) The 2D (4,4)-network of
complex 2 showing the weak C–Hꢀ ꢀ ꢀO interactions along the c-axis. Only H atoms that were from hydrogen bonds were saved.
a C(22)ꢀ ꢀ ꢀO(2) distance of 3.743 Å, which is shorter than the most
forgiving contact distance of <4 Å, but beyond the widely accepted
range of distances between 3.1 and 3.5 Å [22]. So this rather weak
C–Hꢀ ꢀ ꢀO interaction may be simply consequences of other packing
interactions.
Scheme 1. Schematic representation of distortion in complex 2.
2.1.3. Complex 3
The X-ray structure of the resultant metal-complex reveals tri-
ꢀ
acceptor, and the H(C) donor is from the phenyl substituent on the
tin atom [d(C(20)ꢀ ꢀ ꢀO(1)) = 3.434 Å, d(H(20)ꢀ ꢀ ꢀO(1)) = 2.743 Å,
\(C(20)–H (20)ꢀ ꢀ ꢀO(1)) = 131.82°] [20]. As shown in Fig. 2(c), the
1D chains further link along the c-axis direction to form a 2D net-
like structure through rather weak C–Hꢀ ꢀ ꢀO interactions with the H
from the phenyl substituent on the Sn and the O from carboxyl
[d(C(22)ꢀ ꢀ ꢀO(2)) = 3.743 Å, d(H(22)ꢀ ꢀ ꢀO(2)) = 2.854 Å, \(C(22)–
H(22)ꢀ ꢀ ꢀO(2)) = 160.01°]. Finally, the extended 3D topological
clinic mononuclear structure with space group P1. Though complex
3 has a discrete structure, the coordination mode is different from
that of complex 2. The coordination mode of complex 3 has three
phenyl bonded on the Sn(IV), one ligand (HL3) and one methanol
as oxygen donors to the metal center, respectively. HL3 in complex
3 possesses perfect planarity with the dihedral angles between tria-
zole ring and the central phenyl unit to be 8.80°. Moreover, tetrahe-
dral angle around the Sn atom is in the range of 91.42–100.93°. The
distance of Sn(1)–O(1) bond is 2.098 Å, while O(2) atom approaches
the Sn(1) atom at a distance of 3.023 Å, which is longer than that of
complex 2 (2.725 Å). The secondary interaction of Sn(1)ꢀ ꢀ ꢀO(2) in
complex 3 may be impair by five-coordination bonds around tin
center. Solvent CH3OH molecule coordinates to the Sn atom with
the bond length of 2.532 Å and adopts opposite direction of HL3.
structures were formed via
p p stacking interactions between
ꢀ ꢀ ꢀ
the phenyl of the ligand and the pyrazole ring in neighboring
chains with distance of 3.701 Å and an angle of 15.45° [21]. The
p p stacking interactions between layer and layer are the most
ꢀ ꢀ ꢀ
important interactions, which contribute greatly to the supramo-
lecular topologies. While the rather weak C–Hꢀ ꢀ ꢀO interaction has

W.-Q. Geng et al. / Polyhedron 31 (2012) 738–747
741
Complex 3 indicates a little distorted trigonal bipyramidal geometry
as shown in Fig. 3(a). A 1D chain is formed through C–Hꢀ ꢀ ꢀO interac-
tions along the a-axis just like that in complex 2, as shown in
Fig. 3(b). The O(2)ꢀ ꢀ ꢀH(24) contact is 2.590 Å, and C(24)–
H(24)ꢀ ꢀ ꢀO(2) angle is 161.72°. Adjacent chains linked through
O–Hꢀ ꢀ ꢀN hydrogen bonds (H(100)ꢀ ꢀ ꢀN(3) = 1.829 Å and the angle
not form a coordinated bond with tin is found in the disparity in
the C(7)–O(1) and C(7)–O(2) bond distance of 1.219 and 1.315 Å,
respectively [25]. However, the significant interactions of Sn(1)–
O(1) cannot be neglected and complex 4 was described as distorted
trigonal-bipyramidal geometry. As shown in Fig. 4(b), the 1D chains
along the crystallographic a-axis connected through C–Hꢀ ꢀ ꢀO
(H(13)ꢀ ꢀ ꢀO(2) is 2.760 Å and the C(13)–H(13)ꢀ ꢀ ꢀO(2) angle is
131.84°) resemble that of complex 2. But in a further investigation,
the weak interactions which construct supramolecular structure
to be 171.67°) generate
a 2D framework along the c-axis
(Fig. 3(c)). Solvent CH3OH molecule plays an important role in form-
ing the 2D framework [23]. Moreover, the stacking manner was
given by evidence of C–Hꢀ ꢀ ꢀ
p
stacking interactions (3.141 Å) among
are different from complex 2. A pair of C–Hꢀ ꢀ ꢀ
(2.948 Å) exist in the two molecules which locate a position as ‘‘head
interactions (2.698 Å)
which connect two parallel compounds of adjacent chains. Conse-
quently, it forms a building block with the ligand unit in the middle
and the phenyls substituent on the tin in both sides. Then the adja-
p interactions
phenyl units to lead to the 3D architecture. In addition, C–Hꢀ ꢀ ꢀO
interactions (H(5)ꢀ ꢀ ꢀO(5) = 2.650 Å and the angle to be 117.62°) also
contribute greatly to the supramolecular topologies.
to head’’. And there are another C–Hꢀ ꢀ ꢀ
p
2.1.4. Complex 4
cent building block connect to each other with weak C–Hꢀ ꢀ ꢀ
p inter-
interaction
Complex 4 is isomorphous with complex 2. It crystallizes in the
monoclinic space group P2(1)/c with one molecule in the asymmet-
ric unit. To a first approximation, there are four coordinated bonds
around the Sn atom, namely, three ipso-C atoms of the phenyl
groups and the O atom (Sn(1)–O(2) 2.068 Å) of HL4 as shown in
Fig. 4(a). The dihedral angles between tetrazole ring and phenyl of
ligand is 2.24°, which shows a good planarity after coordination
[24]. Two types of Sn–O bond lengths are found: Sn(1)–O(2)
2.068 Å and Sn(1)–O(1) 2.749 Å. Although not considered to repre-
sent a significant bonding interaction, the influence of the O(1) atom
is such that it causes the expansion of the O(2)–Sn(1)–C(14) angle
109.10° and the concomitant contraction in the C(20)–Sn(1)–O(2)
angle 97.66°. Support for the conclusion that the O(2) atom does
actions (3.495 Å) in bc-plane (Fig. 4(c)). Weak C–Hꢀ ꢀ ꢀ
p
plays a vital role in determining the crystal packing and in the con-
struction of the extended 3D supramolecular network.
2.1.5. Complex 5
ꢀ
Complex 5 crystallizes in the triclinic with space group P1. The
centrosymmetric structure features a central Bu4Sn2O2 core to
which two Bu2Sn entities are linked with the result that the O(5)
and O(5A) atoms are three coordinate [26]. Each of the indepen-
dent tin atoms in the structure exhibits distorted trigonal bipyra-
midal geometry, with a C2O trigonal plane and axial positions
that are occupied by oxygen atoms. The formation of the dimeric
Fig. 3. (a) ORTEP diagram showing the structures of complex 3. (b) The 1D chain of complex 3 showing C–Hꢀ ꢀ ꢀO interactions along the a-axis. (c) The 2D network of complex 3
showing the weak O–Hꢀ ꢀ ꢀN interactions along the c-axis. Only H atoms that were from hydrogen bonds were saved.

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W.-Q. Geng et al. / Polyhedron 31 (2012) 738–747
Fig. 4. (a) ORTEP diagram showing the structures of complex 4. (b) The 1D chain of complex 4 showing C–Hꢀ ꢀ ꢀO interactions along the a-axis. (c) The 2D network of complex 4
showing the weak C–Hꢀ ꢀ ꢀ
p
interactions along the c-axis and the weak C–Hꢀ ꢀ ꢀ
p
interactions along the b-axis. Only H atoms that were from hydrogen bonds were saved.
distannoxanes 5 represents an example of ladder-type carboxyl-
ates in which the insertion of 2-OCH3 group occurs. This result
(Fig. 6(a)). The crystal structure of 6 also shows a ladder framework
and features a l2-coordination of –OCH3. Each methanol molecule
l
can be interpreted in terms of donor strength competition, in
which the –OCH3 groups show higher donor capacity than the car-
boxylato group of the ligand [27]. It is noteworthy that the com-
plex 5 crystal unit of the former containing two molecules and
the two molecules are approximately perpendicular distribution
to each other as shown in Fig. 5(a). Through three types of
C–Hꢀ ꢀ ꢀO hydrogen bonding (C(50)–H(50A)ꢀ ꢀ ꢀO(3) = 3.505 Å,
H(50A)ꢀ ꢀ ꢀO(3) = 2.564 Å, angle to be 163.68°; C(15)–H(12)ꢀ ꢀ ꢀO(2) =
3.235 Å, H(15)ꢀ ꢀ ꢀO(2) = 2.310 Å, angle to be 172.34°; C(12)–
H(12)ꢀ ꢀ ꢀO(2) = 3.440 Å, H(12) ꢀ ꢀ ꢀO(2) = 2.538 Å, angle to be
163.19°), the adjacent molecules formed into a 1D structure along
adopts anisobidentate chelating coordination modes (Sn(4)–O(7)
2.220 Å and Sn(3)–O(7) 2.132 Å), while the carboxylic groups of
4-triazolebenzoic acid ligand coordinate with Sn atom as a uniden-
tate bonding (Sn(4)–O(3) 2.153 Å); these values fall in the typical
Sn–O bond length range. Seen along the b-axis in Fig. 6(b), the mol-
ecules of complex 6 connect each other through C–Hꢀ ꢀ ꢀO weak
interactions with distance of 3.324 Å (the distance of H(2)ꢀ ꢀ ꢀO(4)
to be 2.400 Å, angle to be 172.32°), which leads to a 1D chain struc-
ture. Furthermore, C–Hꢀ ꢀ ꢀN weak interactions between adjacent
1D chains are involved in both C(4)–H(4)ꢀ ꢀ ꢀN(2) with the distance
of 3.598 Å (the distance of H(4)ꢀ ꢀ ꢀN(2) to be 2.712 Å, angle to be
159.39°) along b-axis as well as C(26)–H(26A)ꢀ ꢀ ꢀN(3) with the dis-
tance of 3.412 Å (the distance of H(26A)ꢀ ꢀ ꢀN(3) to be 2.561 Å, angle
to be 147.94°) along c-axis, which generates a 2D network struc-
the a-axis as seen from Fig. 5(b). Also contributed by C–Hꢀ ꢀ ꢀ
p weak
interactions between pyrazole ring and the primary C(H) of n-Bu in
neighboring chains with the distance of 2.733 Å, a 2D network
structure is produced along b-axis Fig. 5(c). And then, the 3D archi-
ture (Fig. 6(c)). An additional further C–Hꢀ ꢀ ꢀ
p interactions between
the phenyl of the ligand and the primary C(H) of n-Bu in neighbor-
tecture was formed by evident of C–Hꢀ ꢀ ꢀ
p weak interactions
(3.199 Å) between C(H) of pyrazole ring and the phenyl of ligand.
ing chains lead to a 3D layer frameworks; the C–Hꢀ ꢀ ꢀ
p distance is
3.065 Å.
Details of the relevant data collection and refinement are sum-
marized in Table 1. Selected bond lengths and bond angles for 1–6
are listed in Table 2.
2.1.6. Complex 6
Compared with complex 5, complex 6 is also in the triclinic
ꢀ
space group P1 and has the same coordination mode. The substitu-
tion of pyrazole for triazole brought about a little change of the
molecular stacking. The complex 6 crystal unit of the former con-
tain only one molecule, which is simpler than that of complex 5
Making a comparison among compounds 1–4, polymer 1 is the
special one. Notably, not only O atom but also N atom takes part in
coordination with central metal Sn atom, which forms a successive

W.-Q. Geng et al. / Polyhedron 31 (2012) 738–747
743
Fig. 5. (a) ORTEP diagram showing the structures of complex 5. (b) The 1D ladder of complex 5 showing C–Hꢀ ꢀ ꢀO interactions along the a-axis. (c) The 2D network of complex
5 showing the weak C–Hꢀ ꢀ ꢀ interactions along the b-axis. Only H atoms that were from hydrogen bonds were saved.
p
and uninterrupted line-type polymer. The formation of this unu-
sual geometry may be due to the reasons as below: the two nitro-
gen atoms in pyrazole are ortho position and meta position in
coordination frameworks. Just subtle variations of nitrogen hetero-
cyclic ring not only affect the coordinated bonds of entities, but
also affect various individual interactions, such as C–Hꢀ ꢀ ꢀO, C–
imidazole, namely, l1 and
l
3. So the steric hindrance of the latter
Hꢀ ꢀ ꢀN, O–Hꢀ ꢀ ꢀN, C–Hꢀ ꢀ ꢀ
p
and
p p stacking interactions, which
ꢀ ꢀ ꢀ
one is smaller than the former and it allows the nitrogen on l3 to
influence the final supramolecular assembly.
be a coordination site to bind metals. The added nitrogen atoms
rather than that
l3 in triazole and tetrazole increase the capability
2.2. Optical properties
for attracting electrons, which adversely affects the ability to coor-
dinate with metals [28]. Therefore, in our reported compounds,
only HL1 containing imidzole can coordinate with Sn to form linear
coordination polymer.
There is considerable contemporary interest in the develop-
ment of new organic/organometallic luminescent compounds. This
is because of the enormous potential of such materials in niche
technological applications based on the possibility of using them
as photo- and electroluminescent devices [31]. Therefore the pho-
toluminescence properties of the ligands and complexes were
measured in the solid state at room temperature. The nanosecond
range of lifetime in the solid state at 298 K reveals that the emis-
sion is fluorescent in nature. The measurements were carried out
under the same experimental conditions.
In comparison with HL1 with an emission maximum at 481 nm,
polymer 1 exhibits strongly blue shift with emissions at 369 nm,
upon excitation at 320 nm. As shown above, the L1 in polymer 1
is more twisted and resulted in a larger energy gap between p⁄
In some extent, ligands consisting of both imidazole and car-
boxylate as building block may have a tendency to form polymer.
While the central metal Sn atom only coordinates with O donor
atoms of other three complexes, which display diversiform discrete
structures with their own character. The crystal structure of com-
plex 2 and 4 are similar to each other. We can conclude that com-
plexes 2 and 4 are five-coordinated because of values of d (119Sn) of
2 and 4 are ꢁ107.8 and ꢁ101.7 ppm, respectively [29,30]. The Sn
atom has four covalent bonds and a fifth weaker bonding interac-
tion, which form distorted trigonal bipyramidal geometry. Solvent
molecule plays an important role in constructing the 3D frame-
work in complex 3. Taking complexes 5 and 6 into account, we
use the same n-Bu2SnO and make the nitrogen heterocyclic ring
group of the ligands be different. Although the coordination modes
are the same, the supramolecular structures vary. The structure of
5 is more complicated than that of 6, for the simple reason that the
crystal unit of the former one containing two molecules yet the lat-
ter one containing only one molecule.
and
p orbitals, which could give rise to the emission wavelength
of polymer 1 blue-shifted [32].
Complexes 2 and 5 exhibit photoluminescence with emissions
at 347 and 340 nm, respectively, upon excitation at 320 nm, which
indicate blue shift comparing with that of HL2 with an emission
maximum at 361 nm under the same excitation wavelength. The
emission maximum of complexes 6 is at 366 nm, which has no
shift basically comparing with that of HL3 (368 nm). For complexes
4, blue emissions with maxima at 483 nm were observed upon
From above, we can safely propose that the selection of the
nitrogen heterocyclic ring can definitely adjust the topologies of

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W.-Q. Geng et al. / Polyhedron 31 (2012) 738–747
Fig. 6. (a) ORTEP diagram showing the structures of complex 6. (b) The 1D ladder of complex 6 showing C–Hꢀ ꢀ ꢀO interactions along the b-axis. (c) The 2D network of complex
6 showing the weak C–Hꢀ ꢀ ꢀN interactions along the b-axis and c-axis. Only H atoms that were from hydrogen bonds were saved.
Table 1
Crystal data and details of structure refinement parameters for complexes 1–6.
Compound
1
2
3
4
5
6
Formula
C
28H22N2O2Sn
C28H22N2O2Sn
537.17
C28H25N3O3Sn
570.20
C26H20N4O2Sn
539.15
C54H92N4O8Sn4
1400.08
C52H90N6O8Sn4
1402.06
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
537.17
monoclinic
P2(1)/c
9.816(5)
18.729(5)
14.288(4)
90.000(5)
118.080(2)
90.000(5)
2317.6(16)
4
monoclinic
P2(1)/c
6.779(5)
42.144(5)
8.549(5)
90.000(5)
93.839(5)
90.000(5)
2437(2)
4
triclinic
monoclinic
P2(1)/c
6.792(5)
41.628(5)
8.577(5)
90.000(5)
94.557(5)
90.000(5)
2417(2)
4
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
10.108(5)
10.282(5)
12.446(5)
85.768(5)
83.055(5)
86.425(5)
1278.7(10)
2
11.946(5)
14.429(5)
21.175(5)
74.530(5)
75.566(5)
66.114(5)
3174.8(19)
2
11.821(5)
12.219(5)
12.345(5)
63.800(5)
89.167(5)
85.404(5)
1594.3(11)
1
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalc (mg mꢁ3
)
1.539
1.130
1.464
1.075
1.481
1.033
1.481
1.086
1.465
1.604
1.460
1.598
l
(mmꢁ1
)
h range (°)
1.95–25.00
15636
4083
298
0.0258
0.97–25.00
28223
4289
298
0.0409
1.99–25.00
8884
4418
0.98–24.99
16925
4252
299
0.0400
1.97–25.00
22528
11062
661
0.0354
1.73–25.00
11136
5538
321
0.0596
Total No. of data
No. of unique data
No. of parameters refined
R1
320
0.0483
0.1217
1.047
wR2
0.0515
1.028
0.1220
0.961
0.1197
0.947
0.0870
0.992
0.1597
0.959
Goodness-of-fit (GOF)on F2
excitation at 395 nm, while free ligand HL4 displays two emissions
at 444 nm and 468 m under the same conditions. The observed
kem of complexes 3 was located at 421 nm while that of HL3 was
at 368 nm, which can be tentatively assigned to a MLCT based on a
significant red shift from HL3 to 3 [34].
emissions above are probably contributed by the p–
p⁄ intraligand
fluorescence since similar emissions were also observed for corre-
sponding ligands themselves [33].
The emission range varied extensively, which was considered to
mainly originate from the influence of the coordination modes of

W.-Q. Geng et al. / Polyhedron 31 (2012) 738–747
745
Table 2
Metric parameters for the molecular structures of 1–6.
Compound Coordination mode of the carboxylate ligand and coordination Sn–O (carboxylate) bond
Lengths of covalent bond
around tin (Å)
Bond angles (°)
environment around tin
lengths (Å)
1
Monodentate pentacoordinate (3C, O, N)
distorted trigonal-bipyramidal
Sn(1)–O(1) 2.164(2)
Sn(1)ꢀ ꢀ ꢀO(2) 3.311(5)
Sn(1)–O(1) 2.164(2)
Sn(1)–N(1)#1 2.475(2)
Sn(1)–C(11) 2.137(3)
Sn(1)–C(17) 2.128(3)
Sn(1)–C(23) 2.141(3)
C(11)–Sn(1)–O(1) 90.2(1)
C(17)–Sn(1)–O(1) 97.5(6)
C(23)–Sn(1)–O(1) 93.9(5)
2
3
Anisobidentate chelating pentacoordinate
(3C, 2O) distorted trigonal-bipyramidal
Sn(1)–O(1) 2.058(3)
Sn(1)–O(2) 2.725(5)
Sn(1)–O(1) 2.058(3)
Sn(1)–C(11) 2.134(5)
Sn(1)–C(17) 2.114(5)
Sn(1)–C(23) 2.138(5)
O(1)–Sn(1)–C(17) 108.1(2)
O(1)–Sn(1)–C(11) 97.7(6)
O(1)–Sn(1)–C(23) 110.6(9)
Monodentate pentacoordinate (3C, O, O)
distorted trigonal-bipyramidal
Sn(1)–O(1) 2.098(3)
Sn(1)ꢀ ꢀ ꢀO(2) 3.023(5)
Sn(1)–O(1) 2.098(3)
Sn(1)–O(3) 2.533(4)
Sn(1)–C(10) 2.122(5)
Sn(1)–C(16) 2.128(5)
Sn(1)–C(22) 2.126(5)
O(1)–Sn(1)–C(10) 98.1(8)
O(1)–Sn(1)–C(16) 100.9(4)
O(1)–Sn(1)–C(22) 91.4(2)
4
5
Anisobidentate chelating pentacoordinate
(3C, 2O) distorted trigonal-bipyramidal
Sn(1)–O(2) 2.068(3)
Sn(1)–O(1) 2.749(3)
Sn(1)–O(2) 2.068(3)
Sn(1)––C(8) 2.120(5)
Sn(1)–C(14) 2.138(5)
Sn(1)–C(20) 2.135(5)
O(2)–Sn(1)–C(8) 108.4(8)
O(2)–Sn(1)–C(14) 109.1(0)
O(2)–Sn(1)–C(20) 97.6(6)
Monodentate pentacoordinate (2C, O, 2O)
distorted trigonal-bipyramidal
A
A
A
Sn(1)–O(4) 2.154(3)
Sn(1)ꢀ ꢀ ꢀO(3) 2.974(5)
Sn(1)–O(4) 2.154(3)
Sn(1)–O(7) 2.022(3)
Sn(1)–O(8) 2.240(3)
Sn(1)–C(36) 2.130(5)
Sn(1)–C(50) 2.128(5)
O(7)–Sn(1)–O(4) 80.7(6)
C(50)–Sn(1)–O(4) 96.6(5)
C(36)–Sn(1)–O(4) 100.9(8)
O(4)–Sn(1)–O(8) 151.8(6)
O(7)–Sn(1)–O(8) 71.5(3)
C(50)–Sn(1)–O(8) 90.1(3)
C(36)–Sn(1)–O(8) 94.4(5)
O(7)–Sn(1)–C(50) 113.6(0)
O(7)–Sn(1)–C(36) 113.1(6)
C(50)–Sn(1)–C(36) 131.9(6)
B
B
B
Sn(4)–O(1) 2.153(3)
Sn(4)ꢀ ꢀ ꢀO(2) 2.874(5)
Sn(4)–O(1) 2.153(3)
Sn(4)–O(5) 2.012(3)
Sn(4)–O(6) 2.237(3)
Sn(4)–C(21) 2.119(6)
Sn(4)–C(25) 2.130(5)
O(5)–Sn(4)–C(21) 113.2(2)
O(5)–Sn(4)–C(25) 114.5(0)
C(21)–Sn(4)–C(25) 130.8(2)
O(5)–Sn(4)–O(1) 81.1(5)
C(21)–Sn(4)–O(1) 98.2(4)
C(25)–Sn(4)–O(1) 100.1(4)
O(5)–Sn(4)–O(6) 71.6(3)
C(21)–Sn(4)–O(6) 91.9(2)
C(25)–Sn(4)–O(6) 91.9(8)
O(1)–Sn(4)–O(6) 152.7(7)
6
Monodentate pentacoordinate (2C, O, 2O) distorted trigonal-
bipyramidal
Sn(4)–O(3) 2.153(6)
Sn(4)ꢀ ꢀ ꢀO(4) 2.879(5)
Sn(4)–O(3) 2.153(6)
Sn(4)–O(7) 2.221(7)
Sn(4)–O(8) 2.010(6)
Sn(4)–C(13) 2.125(2)
Sn(4)–C(14) 2.029(2)
O(8)–Sn(4)–O(3) 82.5(2)
C(14)–Sn(4)–O(3) 102.6(6)
O(3)–Sn(4)–O(7) 153.7(2)
C(13)–Sn(4)–O(3) 96.5(5)
C(13)–Sn(4)–O(7) 93.0(5)
C(14)–Sn(4)–O(7) 89.3(6)
O(8)–Sn(4)–O(7) 71.2(3)
C(14)–Sn(4)–C(13) 130.9(7)
O(8)–Sn(4)–C(14) 116.0(6)
O(8)–Sn(4)–C(13) 111.1(5)
Symmetry transformations used to generate equivalent atoms: #1 x + 1, y, z + 1.
metal atom and diverse intermolecular interactions in the solid
state [35].
p p stacking interactions, which influence the final supramolecu-
ꢀ ꢀ ꢀ
lar assembly. At the same time, solvent molecule plays an important
role in forming the 3D framework. In addition, this article provides
useful information on the photoluminescence. The emission range
varied extensively, which was considered to mainly originate from
the influence of the coordination modes of metal atom and diverse
intermolecular interactions in the solid state.
3. Conclusions
Complexes 1–6 are synthesized based on the functional ligands
(HL1–HL4) and Ph3Sn(OH) or n-Bu2SnO. X-ray diffraction analyses
show the novel structures of compounds 1–6 with 1D infinite chain
of polymer 1, single molecular structures of complex 2 and 4, con-
taining solvent molecule of complex 3 and similar structures of com-
plex 5 and 6. In some extent, ligands consisting of both imidazole
and carboxylate as building block may have a tendency to form poly-
mer. Just subtle variations of nitrogen heterocyclic ring not only
affect the coordinated bonds of entities, but also affect various indi-
4. Experimental
4.1. Materials and methods
The reagents and solvents employed were commercially avail-
able and used as received without further purification. The syn-
thetic route complexes are presented in Scheme 2. IR spectra
vidual interactions, such as C–Hꢀ ꢀ ꢀO, C–Hꢀ ꢀ ꢀN, O–Hꢀ ꢀ ꢀN, C–Hꢀ ꢀ ꢀ
pand

746
W.-Q. Geng et al. / Polyhedron 31 (2012) 738–747
Scheme 2. Synthetic route for complexes 1–6.
were recorded with a Nicolet FTIR 170SX instrument using KBr
pellets. Elemental analysis was performed with a Perkin-Elmer
240C analyzer. 1H NMR spectra were recorded on a Bruker AV
400 spectrometer with tms as internal standard. 119Sn NMR spec-
tra (proton-decoupled) were recorded on a Bruker AV 400 spec-
trometer operating at 150 MHz; resonances are referenced to
tetramethyltin (external standard, 119Sn). The luminescent spectra
were measured on powder samples at room temperature using a
model Perkin-Elmer LS55 fluorescence spectrophotometer. Both
the excitation and the emission slits were 10 nm, and the re-
sponse time was 2 s.
Single-crystal X-ray diffraction measurements were carried out
on a Bruker Smart 1000 CCD diffractometer equipped with a
graphite crystal monochromator situated in the incident beam
for data collection at room temperature. The determinations of
unit cell parameters and data collections were performed with
4.3. Synthesis of complexes
Ph3Sn(OH) (370 mg, 1 mmol) and ligands HL1–HL4 (1 mmol)
were dissolved in 30 mL toluene and were stirred at 60 °C for 8 h
after formed in the reaction was removed by using a Dean–Stark
apparatus. The excessive toluene was evaporated and filtered to af-
ford the crude powder. The powder was washed with 5 mL CH2Cl2
three times and dried in vacuo and then dissolved in 15 mL meth-
anol. Crystals of 1–4 suitable for single-crystal X-ray diffraction
analysis were obtained after the solution was allowed to stand
for approximately 2 weeks at room temperature, respectively.
Synthesis of 5 and 6 were similar to that of 1, except that n-Bu2S-
nO (500 mg, 2 mmol) was used instead of Ph3Sn(OH). Colorless,
block crystals of 5 and 6 suitable for single-crystal X-ray diffraction
analysis were collected after evaporation at room temperature for
about 2 weeks.
Mo K
a
radiation (k = 0.71073 Å). Unit cell dimensions were ob-
Polymer 1: Primrose yellow crystals. Weight: 180 mg, yield:
tained with least-squares refinements, and all structures were
solved by direct methods with SHELXL-97 [36]. The other non-
hydrogen atoms were located in successive difference Fourier
syntheses. The final refinement was performed by full-matrix
least-squares methods with anisotropic thermal parameters for
non-hydrogen atoms on F2. The hydrogen atoms were added the-
oretically and riding on the concerned atoms.
34%. 119Sn NMR (DMSO-d6): d = ꢁ226.374 ppm. Anal. Calc. (%) for
C
28H22N2O2Sn: C, 62.57; H, 4.10; N, 5.21. Found: C, 62.23; H,
3.97; N, 5.58%. IR (KBr, cmꢁ1): 3122 (m), 3066 (m), 1645 (s),
1604 (m), 1514 (s), 1480 (m), 1428 (m), 1309 (s), 1236 (m), 1122
(m), 1061 (s), 782 (m), 733 (s), 698 (s), 451 (m).
Complex 2: Colorless crystals. Weight: 330 mg, yield: 62%. 119Sn
NMR (DMSO-d6): d = ꢁ107.822 ppm. Anal.
Calc. (%) for
C
28H22N2O2Sn: C, 62.57; H, 4.10; N, 5.21. Found: C, 62.26; H,
3.95; N, 5.54%. IR (KBr, cmꢁ1): 3113 (w), 3065 (m), 1622 (s),
1527 (s), 1479 (m), 1606 (s), 1431 (s), 1343 (s), 1200 (s), 931 (s),
857 (s), 733 (s), 988 (s), 696 (s), 589 (s), 447 (s).
4.2. Synthesis of ligands
See supporting information.

W.-Q. Geng et al. / Polyhedron 31 (2012) 738–747
747
Complex 3: Primrose yellow crystals. Weight: 400 mg, yield:
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C
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C
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