Multiple bismuth(III)-thioether secondary interactions integrate metalloporphyrin ligands into functional networks

Article abstract of DOI:10.1021/ic061711m

We introduce the 1,2,3-tris(organylthiophenyl) group as a symmetrical, multidentate chelation link for building coordination networks. For this, zinc(II) 5,10,15,20-tetrakis[3′,4′,5′-tris(methylthio)phenyl] porphyrin was synthesized and integrated into a two-dimensional network via coordination with BiBr₃. The coordination link exhibits an unusually complex bonding pattern, involving six S atoms from two neighboring ligands that form multiple Bi-S interactions (distances ranging from 3.08 to 3.63 A) with a dimerlike unit of Bi₂Br₆. The electronic interaction between the porphyrin center and the Bi₂Br₆ block was illustrated by the diffuse-reflectance spectrum of the network compound, in which a modest red-shifted feature at 1.8 eV was seen (while the Q-band absorption of the metalloporphyrin core continues to be dominant at 1.9 eV).

Full text of DOI:10.1021/ic061711m

Inorg. Chem. 2007, 46, 4844−4849
Multiple Bismuth(III)
−Thioether Secondary Interactions Integrate
Metalloporphyrin Ligands into Functional Networks
Kunhao Li,† Guo Huang,‡ Zhengtao Xu,*,‡ Mingliang Zhang,‡ Matthias Zeller,§ Allen D. Hunter,§
Stephen Sin-Yin Chui,| Chi-Ming Che,| and Wai-Yeung Wong
Department of Chemistry, The George Washington UniVersity, 725 21st Street NW, Washington,
D.C. 20052, Department of Biology and Chemistry, City UniVersity of Hong Kong, 83 Tat Chee
AVenue, Kowloon, Hong Kong, China, Department of Chemistry, Youngstown State UniVersity,
One UniVersity Plaza, Youngstown, Ohio 44555, Department of Chemistry, The UniVersity of
Hong Kong, Pokfulam Road, Hong Kong, China, and Department of Chemistry, Hong Kong
Baptist UniVersity, Waterloo Road, Kowloon Tong, Hong Kong, China
Received September 10, 2006
We introduce the 1,2,3-tris(organylthiophenyl) group as a symmetrical, multidentate chelation link for building
coordination networks. For this, zinc(II) 5,10,15,20-tetrakis[3 ,4 ,5 -tris(methylthio)phenyl]porphyrin was synthesized
and integrated into a two-dimensional network via coordination with BiBr3. The coordination link exhibits an unusually
complex bonding pattern, involving six S atoms from two neighboring ligands that form multiple Bi S interactions
′
′ ′
−
(distances ranging from 3.08 to 3.63 Å) with a dimerlike unit of Bi2Br6. The electronic interaction between the
porphyrin center and the Bi2Br6 block was illustrated by the diffuse-reflectance spectrum of the network compound,
in which a modest red-shifted feature at 1.8 eV was seen (while the Q-band absorption of the metalloporphyrin
core continues to be dominant at 1.9 eV).
Introduction
required orientation in the growing lattice. On the other hand,
chelation bonds attract attention as linkages for extended
networks,14-19 partly because of the potentially higher
bonding strength that might be achieved in comparison to
single-fold coordination bonds. The discovery reported here
arises from the newly synthesized porphyrin ligand zinc(II)
In the growing field of coordination networks,1-5 it is of
interest to develop ligand systems for uncovering novel
structural features (e.g., local coordination bonding patterns
and network connectivity) and for achieving richer func-
tionalities in the solid state. Among the numerous consid-
erations, ligand symmetry and chelation ability are two
features that could offer important advantages. Besides the
general aesthetic appeal, rigid, symmetrical ligands tend to
facilitate the formation of highly ordered, crystalline extended
networks,6-13 apparently because the multiple equivalent
positions allow the ligand to achieve more readily the
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† The George Washington University.
‡ City University of Hong Kong.
§ Youngstown State University.
| The University of Hong Kong.
Hong Kong Baptist University.
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4844 Inorganic Chemistry, Vol. 46, No. 12, 2007
10.1021/ic061711m CCC: $37.00
© 2007 American Chemical Society
Published on Web 05/09/2007

Multiple Bismuth(III)-Thioether Secondary Interactions
Chart 1
(X ) Cl or Br) components and aromatic π-electron systems
equipped with organylthio (RS-) groups. Besides the
substantial charge-transfer phenomena that could lead to
potentially useful semiconductive properties, these networks
and the other related compounds34-37 are usually convenient
to grow and provide advantages for solution processing. The
network herein exemplifies a preliminary effort to install the
potentially electroactive bismuth(III)-thioether coordination
links across the functional molecular systems of metallopor-
phyrins. The ultimate prospect of achieving a functional
semiconductive network with fully integrated porphyrin units
is fascinating because of the rich photophysical and electronic
properties associated with the widely studied10,38-43 porphyrin
functionality.
5,10,15,20-tetrakis[3′,4′,5′-tris(methylthio)phenyl]porphy-
rin (Zn-T3MTPP; see Chart 1) with multiple thioether groups
symmetrically disposed to hatch chelation links in network
formation. We now elaborate on the original aspects of this
discovery.
Experimental Section
Starting materials, reagents, and solvents were purchased from
commercial sources (Aldrich and Fisher Scientific) and used without
further purification unless stated otherwise. Melting points were
measured on a Mel-temp II melting point apparatus and were
Thioethers (R-S-R′) have proven quite versatile as
network building blocks in both the single-fold coordination
and the chelation mode.20-30 In this regard, the symmetric
1,2,3-tris(methylthio)phenyl group presents a versatile mul-
tisite donor for forming extended coordination nets. Previ-
ously, hexakis(organylthio)benzene or octakis(organylthio)-
naphthalene ligands containing the 1,2,3-tris(organylthio)
moiety have been used for network formation.23-25 However,
the tris(organylthio) moieties thereof are embedded among
other organylthio groups, and their configuration and function
as a distinct chelating unit are thus largely obscured. In order
to probe and accentuate the utility of the tris(organylthioaryl)
moiety as an explicit and prominent chelating unit, we have
synthesized ligand Zn-T3MTPP, in which four 1,2,3-tris-
(methylthio)phenyl groups are symmetrically affixed onto
the metalloporphyrin core. Interestingly, in forming networks
with bismuth(III) bromide (BiBr3), an unusually complex
chelation link consisting of multiple Bi-S interactions was
established across the Zn-T3MTPP ligands, which, in a large
connection, is also reminiscent of the multiple hydrogen-
bonding motifs that are so widely used in constructing robust
supramolecular arrays.
1
uncorrected. Solution H and 13C NMR spectra were recorded on
a 200 MHz Varian Mercury spectrometer at room temperature, with
tetramethylsilane as the internal standard. Energy-dispersive spec-
trometry (EDS) was performed on a Philips XL30 FEG scanning
electron microscope. The atom ratio of the concerned elements was
kept constant in different regions. The results were the average
values of three points.
The X-ray datasets of 2 and 3 were collected from red platelike
crystals on a Bruker AXS SMART APEX CCD system using Mo
KR (λ ) 0.710 73 Å) radiation. The structure was solved and refined
2
by full-matrix least squares on Fo using Bruker Advanced X-ray
Solutions SHELXTL (version 6.14; Bruker AXS Inc.: Madison,
WI, 2003). Selected crystallographic data are summarized in Table
1, with details of the X-ray diffraction studies on the single crystals
provided in the Supporting Information.
Powder X-ray diffraction patterns of crystal samples of 2 and 3
(packed inside a sealed capillary) were collected on a Bruker D8
Advance diffractometer with nickel-foil-filtered and monochromatic
Cu KR1,2 radiation (λ ) 1.541 t42 Å) operated at 1.6 kW. The
primary parallel X-ray beam was generated by a Go¨bel Mirror and
Soller slit (2.5°), and the scattered beam was analyzed by an energy-
dispersive X-ray detector (Sol-X) with the following scanning
parameters (2θ range ) 5-60°; step size ) 0.04°; time per step )
5 s). The sample was continuously rotated during data collection.
Deterioration or color change of crystals inside the capillary was
Another potentially important aspect of the discovery here
relates to our recent efforts in synthesizing semiconductive
coordination networks.31-33 In the previous networks, sig-
nificant electronic interactions were observed between BiX3
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Inorganic Chemistry, Vol. 46, No. 12, 2007 4845

Li et al.
Table 1. Selected Crystallographic Data for 2 and 3
brown solution. The burgundy mixture was then heated to reflux
for 1 h. After being cooled down to room temperature, the mixture
was transferred into a round-bottomed flask and silica gel was
added. After removal of the solvent in vacuo, the purple residue
was loaded on top of a prepacked silica gel column. The column
was then eluted first with 50% (by volume) dichloromethane in
hexanes to remove the side products. The product was then eluted
by 70% dichloromethane in hexanes. After evaporation of the
solvent in vacuo, the pure product was obtained as a shiny purple
solid [0.54 g, 42% based on 3,4,5-tris(methylthio)benzaldehyde].
Mp: 398-400 °C. 1H NMR (200 MHz, CDCl3): δ 2.42 (s, 24 H),
2.67 (s, 12 H), 7.72 (s, 8 H), 8.96 (s, 8 H). 13C NMR (50 MHz,
CDCl3): δ 15.97, 17.83, 119.84, 126.17, 128.03, 131.16, 131.54,
143.67, 145.56.
2
3
chemical
formula
fw
space group
a, Å
C
104H96Bi4Br12N8-
O8S12Zn
C
104H96Bi4Br12N8-
O8S12Cu
3830.84
P21/n
3828.99
P21/n
13.894(2)
27.684(5)
16.744(3)
106.879(3)
6163(2)
2
2.064
0.710 73 (Mo KR)
10.032
13.949(2
27.592(4)
16.714(2)
107.134(2)
6147(1)
2
2.069
0.710 73 (Mo KR)
10.035
b, Å
c, Å
â, deg
V, Å3
Z
F
calcd, g/cm3
wavelength, Å
abs coeff (µ),
mm-1
R1a
3.10% [I > 2σ(I)]
7.56% [I > 2σ(I)]
2.57% [I > 2σ(I)]
5.66% [I > 2σ(I)]
wR2b
Zinc(II) 5,10,15,20-Tetrakis[3′,4′,5′-tris(methylthio)phenyl]-
porphyrin (Zn-T3MTPP). A stirred mixture of 2H-T3MSPP (0.21
g, 0.18 mmol) and zinc acetate dihydrate (42 mg, 99%, 0.19 mmol)
in dimethylformamide (DMF; 30 mL) was refluxed for 15 min
before water (150 mL) was added and the resultant suspension/
emulsion extracted with dichloromethane (100 mL × 3). The
combined organic layers were washed with water and brine and
dried over sodium sulfate for 15 min. After removal of the solvent
on a rotary evaporator, the product was obtained as a purple solid.
The crude product was purified by a short column with 3:2 CHCl3/
hexanes as the eluent (0.18 g, 84% based on 2H-T3MTPP). Mp:
a R1 ) ∑||Fo| - |Fc||/∑(|Fo|). b wR2 ) {∑[w(Fo2 - Fc2)2]/∑[w(Fo ) ]}1/2
.
2 2
not observed after data collection. Diffraction data of 2 were
corrected by the background contribution and sample displacement
error, and the corrected and scaled data were compared with that
generated by a simulation program Mercury 1.4, which was based
on single-crystal data of the sample (see the Supporting Information
for the patterns). Crystals of 2 and 3 display similar diffraction
patterns in the same spectral range as that of the isostructural
analogues.
1
385-387 °C (without dec). H NMR (200 MHz, CDCl3): δ 2.41
(s, 24 H), 2.68 (s, 12 H), 7.71 (s, 8 H), 9.06 (s, 8 H). 13C NMR is
not available because of low solubility in common deuterated
solvents. Further characterization was provided by the subsequent
single-crystal X-ray diffraction analysis of the hybrid extended
networks (see below) prepared from this compound.
3,4,5-Tris(methylthio)benzaldehyde (1). In an argon-filled
glovebox, sodium methylthiolate (3.32 g, 95%, 45.0 mmol) and a
magnetic stirring bar were loaded into a two-neck round-bottomed
flask. The flask was then taken out of the glovebox and connected
to a nitrogen bubbler. DMEU (anhydrous, 50 mL) was transferred
via a cannula into the flask, and stirring was started. 3,4,5-
Trifluorobenzaldehyde (1.61 g, 99%, 10 mmol) dissolved in DMEU
(anhydrous, 30 mL) was purged with nitrogen for 5 min and then
transferred into the flask slowly at room temperature. After being
stirred at room temperature for 20 min, the mixture changed into
a red-brown solution. At 1 h, methyl iodide (3.4 mL, 99%, 53.9
mmol) was injected slowly into the solution when the mixture was
chilled in an ice/water bath. The resultant light-yellow solution was
poured into water (100 mL), and the aqueous suspension was
extracted with hexanes/dichloromethane (1:1, 100 mL × 3). The
organic layers were combined and washed with water (200 mL ×
3) and brine (200 mL). After being dried over anhydrous sodium
sulfate for 10 min, the solvent was removed on a rotary evaporator
to afford a yellow solid. The crude product was purified by flash
chromatography (with 1:2 CH2Cl2/hexanes as the eluent) to yield
the pure product as a light-yellow solid (1.55 g, 63% based on the
starting trifluorobenzaldehyde). Mp: 150-152 °C. 1H NMR (200
MHz, CD2Cl2): δ 2.36 (s, 3 H), 2.49 (s, 6 H), 7.32 (s, 2 H), 9.97
(s, 1 H). 13C NMR (50 MHz, CD2Cl2): δ 15.78, 17.26, 120.00,
134.79, 137.18, 148.84, 191.77.
Copper(II)5,10,15,20-Tetrakis[3′,4′,5′-tris(methylthio)phenyl]-
porphyrin (Cu-T3MTPP). By refluxing of a mixture of 2H-
T3MTPP (0.17 g, 0.14 mmol) and copper(II) chloride (42.6 mg,
99.5%, 0.32 mmol) in DMF (15 mL) for 2 h, Cu-T3MTPP was
prepared in 82% yield (0.15 g after flash column separation with
3:2 CHCl3/hexanes as the eluent) as a red-purple solid. Mp: 379-
380 °C. NMR is not available because of low solubility in common
deuterated solvents. Further characterization was provided by the
single-crystal X-ray diffraction analysis of the hybrid extended
networks prepared from this compound.
X-ray-Quality Single Crystals of 2. Inside an argon-filled
glovebox, a nitrobenzene solution of Zn-T3MTPP (0.4 mL, 1.68
mM) was layered at the bottom of three glass tubes (10 mm o.d./6
mm i.d.). A 1:1 mixture of nitrobenzene/benzene (0.2 mL) and a
benzene solution of BiBr3 (6.7 mM, 0.2, 0.4, and 0.6 mL,
respectively) were layered sequentially without disturbing the
interfaces. The tubes were sealed with Parafilm and left upright
and undisturbed inside the glovebox. After about 7 days, red
platelike single crystals suitable for X-ray diffraction analysis were
observed for the setups with 0.4 and 0.6 mL of BiBr3 solution (i.e.,
with ligand/BiBr3 ratios at 1:4 and 1:6, respectively). Single-crystal
X-ray diffraction analysis for both batches of crystals yielded the
same crystal structure of 2. Powder X-ray diffraction studies
indicated a single phase consistent with the single-crystal structure
(see Figure S5 in the Supporting Information). EDS (by a Philips
XL30 FEG scanning electron microscope) measurement of the
product indicated the S/Zn/Bi/Br ratio to be 11.7:1.0:3.9:9.5. The
crystal growth experiments are readily repeatable, and exact yields
will be obtained in subsequent preparations on larger scales. A
similar procedure was used for obtaining the single crystals of 3.
2H-5,10,15,20-Tetrakis[3′,4′,5′-tris(methylthio)phenyl]porphy-
rin (2H-T3MTPP). To an oxygen-free solution of 3,4,5-tris-
(methylthio)benzaldehyde (1.07 g, 4.4 mmol) in dichloromethane
(anhydrous, 290 mL) was added pyrrole (0.30 g, 99%, 4.4 mmol,
purged with nitrogen for 5 min) under nitrogen protection. After 5
min, boron trifluoride diethyl etherate (0.1 mL, 1 M in dichlo-
romethane) was injected at room temperature while the mixture
was stirred magnetically. The mixture was then covered with
aluminum foil, and the stirring was continued for another 2 h,
followed by the addition of p-chloranil (2,3,5,6-tetrachloro-1,4-
benzoquinone, 0.81 g, 99%, 3.3 mmol) into the resultant dark-red-
4846 Inorganic Chemistry, Vol. 46, No. 12, 2007

Multiple Bismuth(III)-Thioether Secondary Interactions
Scheme 1a
Figure 1. Chelation motif in the crystal structure of 2. Interatomic distances
(Å): Bi1-Br1, 2.6735(5); Bi1-Br2, 2.6519(5); Bi1-Br3, 2.6449(5); Bi1-
Br5, 3.378; Bi1-S1, 3.085(1); Bi1-S2, 3.630(1); Bi1-S4, 3.3394(9); Bi1-
S5, 3.428(1); Bi2-Br4, 2.6243(5); Bi2-Br5, 2.6785(6); Bi2-Br6, 2.6457-
(6); Bi2-S2, 3.590(1); Bi2-S3, 3.264(1); Bi2-S5, 3.326(1); Bi2-S6,
3.337(1); Bi2-O3, 3.112(4); Bi2-O4, 3.116(3). Bi-S and Bi-Br interac-
tions above 3.4 Å and Bi-O interactions are shown as dotted lines.
a Key: (a) NaSMe, DMEU, rt, N2, 1 h, MeI; (b) pyrrole, CH2Cl2, BF3
etherate, N2, rt, 2 h/p-chloranil, reflux, 1 h; (c) Zn(AcO)2, CHCl3, reflux,
1 h; (d) CuCl2, DMF, reflux, 2 h.
loss of the crystalline order of the original frameworks.
Further studies are ongoing for obtaining more robust
frameworks.
Results and Discussion
The metalloporphyrin ligands Zn-T3MTPP and Cu-
T3MTPP were efficiently synthesized in a multistep proce-
dure (see Scheme 1). The reaction of sodium methylthiolate
with 3,4,5-trifluorobenzaldehyde gave in 63% yield of 1. In
comparison to the reported multistep synthetic route to 1,44
this single-step procedure provides obvious advantages.
Aldehyde 1 was then subjected to the Lindsey porphyrin
synthesis conditions45 to afford 2H-T3MTPP as the product
in 42% yield. The metalation of the porphyrin thus obtained
was carried out by refluxing of the porphyrin with a metal
salt [Zn(OAc)2 or CuCl2] in DMF, and the processes were
usually complete in 2 h. The purification was straightforward
(usually by a short silica gel flash column), and yields were
good (see the Experimental Section for details).
The crystallization of the Zn-T3MTPP (or Cu-T3MTPP)
ligand with BiBr3 was conducted at room temperature in a
slow-diffusion setup (see the Experimental Section). X-ray
structure determination on the resultant single crystals
indicated a chemical composition of Zn-T3MTPP‚4BiBr3‚
4PhNO2‚4benzene (2). An isomorphic product (3) was
obtained with Cu-T3MTPP (detailed crystallographic data
for 2 and 3 are given in the Supporting Information). The
composition of 2 is also consistent with the results from
thermogravimetric analysis (TGA) measurement. As seen in
Figure S1 in the Supporting Information, the thermogram
of the solid sample of 2 features a distinct step of weight
loss of about 20% around 120 °C, corresponding to the
removal of the included benzene and nitrobenzene molecules
(calculated weight percentage of benzene and nitrobenzene
in 2: 21.0%). Powder X-ray diffraction studies indicate that
the evacuation of guest molecules resulted in a substantial
The crystal structure formed in the space group P21/n (a
) 13.894 Å, b ) 27.684 Å, c ) 16.744 Å, and â )
106.879°), with the asymmetric portion of the unit cell
containing half of the Zn-T3MTPP molecule and two BiBr3
fragments, together with two benzene molecules and two
nitrobenzene molecules included as guest molecules. The Zn-
T3MTPP molecule adopts a centrosymmetric conformation
with the pendant phenyl groups significantly tilted out of
the plane with the porphyrin core (dihedral angles: 75 and
63°). The interaction of the Zn-T3MTPP ligand with the
BiBr3 components is established primarily through the
coordination between the BiIII center and the S atoms on the
ligand. The local bonding features are shown in Figure 1, in
which three distinct components can be identified as the Bi2-
Br6 portion, two tris(methylthio)phenyl groups (from two
neighboring Zn-T3MTPP molecules), and one associated
nitrobenzene molecule. The Bi2Br6 unit is based on the
sharing of the Br5 atom, which interacts with Bi1 and Bi2
in rather different interatomic distances (Bi1-Br5, 3.38 Å;
Bi2-Br5, 2.68 Å). Additionally, Bi1 further bonds to three
Br atoms (Br1, Br2, and Br3), while Bi2 bonds to only two
(Br4 and Br6). Part of the remaining coordination sphere of
Bi2 is occupied by the two O atoms of a nitrobenzene
molecule featuring Bi-O distances of 3.11 and 3.12 Å.
One striking feature of the current network is the multi-
plicity of the chelation interactions in the linkage across the
neighboring ligands; namely, the Bi2Br6 unit serves as a
complex Lewis acid linkage and forms a relatively large
number of coordination bonds and secondary interactions
with the neighboring Zn-T3MTPP molecules. As shown in
Figure 1, the interatomic distances are quite variable, as is
typical of secondary interactions in other systems.46,47 For
one of the tris(methylthio)phenyl groups, the major links are
(44) Kompis, I.; Wick, A. E. Patent DE2847825, 1979.
(45) Lindsey, J. S.; MacCrum, K. A.; Tyhonas, J. S.; Chuang, Y. Y. J.
Org. Chem. 1994, 59, 579.
Inorganic Chemistry, Vol. 46, No. 12, 2007 4847

Li et al.
Figure 3. Topological representation of the 2D net in 2. Color code: purple
sphere, Zn; red sphere, midpoint of Bi1 and Bi2 in the Bi2Br6 unit.
Figure 2. 2D net in 2. Color code: large red sphere, Bi; large purple
sphere, Zn; medium green sphere, Br; medium orange sphere, S; small white
sphere, C; small blue sphere, N.
Bi1-S1 (3.09 Å) and Bi2-S3 (3.26 Å); for the other, they
are Bi2-S5 (3.33 Å), Bi2-S6 (3.34 Å), Bi1-S4 (3.34 Å),
and Bi1-S5 (3.43 Å). In addition, atom S2 also interacts
with Bi1 and Bi2 at longer distances (3.63 and 3.59 Å,
respectively). Such multiple-fold chelation interactions be-
tween neighboring ligands are rare among the coordination
networks because most networks are based on only one or
two coordination bonds between the ligating unit (e.g.,
-COO-, -CN) and metal centers. This multiple-coordina-
tion motif is also reminiscent of the multiple hydrogen-
bonding patterns that are widely used for strengthening
supramolecular networks and may similarly serve as a
possible means for reinforcing the coordination linkages
across the organic ligands. Further study is ongoing in this
group to probe the generality and utility of similar multiple-
interaction patterns for assembling functional coordination
networks.
The network thus resulting from the intermolecular linkage
is two-dimensional, and an overview of the net is depicted
in Figure 2. The connectivity of the network can be
represented by connecting the Zn atom (as the center of the
Zn-T3MTPP ligand) and the geometric center of the inter-
linking Bi2Br6 block (roughly treated as the midpoint between
the two Bi atoms). The resultant representation is a relatively
simple four-connected net as shown in Figure 3. The 2D
net is parallel to the lattice plane [-1, 0, 1]. The 2D network
shows substantial corrugation, and large void space exists
between the neighboring networks (see Figures S2 and S3
in the Supporting Information). The void space is occupied
by the nitrobenzene and benzene molecules from the crystal-
lization process (see Figure S4 in the Supporting Informa-
tion). Among the two crystallographically equivalent ni-
trobenzene molecules, one is coordinated to the Bi2 atom
and the other is stacked parallel to the metalloporphyrin core,
with an interplanar distance of 3.33 Å. Because of the
centrosymmetric packing in the structure, each porphyrin core
is thus sandwiched by two crystallographically equivalent
Figure 4. Room-temperature solid-state absorption spectra for (a) Zn-
T3MTPP and (b) 2.
nitrobenzene guests. By comparison, the interaction of the
benzene molecules with the host network is less distinct, and
they appear to function mostly as van der Waals space fillers.
It has been in our interest to observe the potential
electronic interaction between the metalloporphyrin core and
the BiBr3 component within this composite network because
our previous work has established that effective electronic
interactions could be achieved between large aromatic
hydrocarbon ligands and BiIII centers. Diffuse-reflectance
measurements were therefore carried out on the solid samples
of Zn-T3MTPP and network compound 2. As shown in
Figure 4, compound Zn-T3MTPP features a major absorption
at about 1.9 eV, corresponding to the Q band in typical
molecular metalloporphyrin systems. The Q-band feature
continues to dominate in the spectrum of compound 2,
indicating the distinct contribution from the porphyrin
moiety. Notably, a slightly red-shifted new absorption feature
occurs at 1.8 eV, which might be ascribed to the electronic
interaction between the Bi2Br6 fragment and the porphyrin
core. In comparison with the dominant red shift of the
previously studied aromatic hydrocarbon systems,32,33 the
new absorption feature of 2 appears quite modest, suggesting
weaker electronic coupling between the ligand and the BiBr3
component. The weaker electronic coupling might partly be
due to the nonplanar alignment of the porphyrin core and
the pendant phenyl groups of Zn-T3MTPP. We also suspect
that the highest occupied molecular orbital level of the
metalloporphyrin molecule is lower than that of the previ-
ously studied aromatic hydrocarbon systems, hindering the
electron donation onto the Lewis acid units of BiBr3. Further
(46) Starbuck, J.; Norman, N. C.; Orpen, A. G. New J. Chem. 1999, 23,
969.
(47) Alcock, N. W. AdV. Inorg. Chem. Radiochem. 1972, 15, 1.
4848 Inorganic Chemistry, Vol. 46, No. 12, 2007

Multiple Bismuth(III)-Thioether Secondary Interactions
study is ongoing to access systems for stronger electronic
interaction that more effectively integrates the porphyrin core
into a semiconductive coordination network.
Acknowledgment. This work is partially supported by
City University of Hong Kong (Project No. 9360121) and
by a grant from the Research Grants Council of the Hong
Kong Special Administrative Region, China [Project No.
9041109 (CityU 102406)]. We thank the donors of the
American Chemical Society Petroleum Research Fund for
partial support of this research, and one of the diffractometers
was funded by NSF Grant 0087210, by the Ohio Board of
Regents Grant CAP-491, and by Youngstown State Univer-
sity. We also thank Dr. Yanqiong Sun for demonstrating
further the repeatability of the crystal growth.
Conclusion
In short, we have explored the usefulness of the 1,2,3-
tris(methylthio)phenyl group as a distinct and prominent
chelating unit in forming functional coordination networks.
The porphyrin-based networks reported herein could serve
as a first step toward semiconductive coordination networks
in which the porphyrin unit is more fully integrated via
stronger electronic interactions. In a wider perspective, the
methyl groups could be replaced by more sophisticated
organic groups, the resultant tris(organylthio)phenyl unit
could be attached to a variety of building blocks, and a
variety of other metal salts could be used as acceptors, in
order to explore other patterns of multiple chelation links
and to achieve crystalline networks with more advanced
functions and properties.
Supporting Information Available: Full crystallographic data
in CIF format for 2 and 3, a TGA plot for the solid sample of 2,
additional figures of the crystal structure of 2, and powder X-ray
diffraction patterns of 2. This material is available free of charge
via the Internet at http://pubs.acs.org.
IC061711M
Inorganic Chemistry, Vol. 46, No. 12, 2007 4849