Sulfur-bridged iron and manganese carbonyl clusters: Synthesis, structure and nonlinear optical properties of [(μ-SPh)2Fe 2(CO)6]2(μ4-S) and [PPN][(μ3-S)2Mn3(CO)9]

Article abstract of DOI:10.1016/S0022-2860(03)00415-0

Two sulfur-bridged carbonyl clusters [(μ-SPh)₂Fe ₂(CO)₆]₂(μ₄-S) 1 and [PPN][(μ3-S)₂Mn₃(CO)₉] 2 were synthesized for study of the third-order nonlinear properties. Cluster 1 consists of two doubly bridged Fe₂(CO)₆ fragments bonded for a center μ4-sulfur atom of the distorted tetrahedron. Each fragments is also bridged with the sulfur from a thiophenol group. Cluster 2 exhibits a D_3h equilateral triangular frame with three Mn(CO)₃ units apically bicapped by the two μ3-sulfur atoms. The moderate third-order optical nonlinear absorption and refraction effects of clusters 1 and 2 in CH ₂Cl₂ solution were observed at 532 nm by using of the z-scan measurements of an 8-ns pulsed laser. The third-order nonlinear optical susceptibilities, X⁽³⁾, were detected with 5.4 × 10 ^-13 and 1.2 × 10^-13 esu for 1 and 2, respectively, in solution. The structure-property relationship in clusters is also discussed in the paper.

Full text of DOI:10.1016/S0022-2860(03)00415-0

Journal of Molecular Structure 657 (2003) 165–175
www.elsevier.com/locate/molstruc
Sulfur-bridged iron and manganese carbonyl clusters: synthesis,
structure and nonlinear optical properties
of [(m-SPh)2Fe2(CO)6]2(m4-S) and [PPN][(m3-S)2Mn3(CO)9]
Wen-Rui Yaoa, Dian-Shun Guob, Ze-Hua Liua, Qian-Feng Zhanga,
*
aDepartment of Chemistry and Chemical Engineering, Anhui University of Technology, Maanshan, Anhui 243002, People’s Republic of China
bDepartment of Chemistry, Shandong Normal University, Jinan 250014, People’s Republic of China
Received 1 April 2003; accepted 29 May 2003
Abstract
Two sulfur-bridged carbonyl clusters [(m-SPh)2Fe2(CO)6]2(m4-S) 1 and [PPN][(m3-S)2Mn3(CO)9] 2 were synthesized for
study of the third-order nonlinear properties. Cluster 1 consists of two doubly bridged Fe2(CO)6 fragments bonded for a center
m4-sulfur atom of the distorted tetrahedron. Each fragments is also bridged with the sulfur from a thiophenol group. Cluster 2
exhibits a D3h equilateral triangular frame with three Mn(CO)3 units apically bicapped by the two m3-sulfur atoms. The
moderate third-order optical nonlinear absorption and refraction effects of clusters 1 and 2 in CH2Cl2 solution were observed at
532 nm by using of the z-scan measurements of an 8-ns pulsed laser. The third-order nonlinear optical susceptibilities, xð3Þ
;
were detected with 5.4 £ 10213 and 1.2 £ 10213 esu for 1 and 2, respectively, in solution. The structure–property relationship
in clusters is also discussed in the paper.
q 2003 Elsevier B.V. All rights reserved.
Keywords: Synthesis; Crystal structure; Sulfur; Cluster; NLO properties
1. Introduction
research is to empirically determine what properties
are necessary for materials to exhibit large xð3Þ values
[2]. One of promising approaches is to develop the
structure–property relationship so that we may
understand which structural modes of materials with
easily polarized electrons generally exhibit large xð3Þ
values [3,4]. Recently, metal–organic complexes
have been extensively studied for the development
of NLO materials due to their rich electronic
characters and structural variations [5]. For example,
transition metal complexes with planar and p-
conjugated ligands contain both electrons that are
free to move within the extended p systems of the
ligands and the addition energy levels introduced by
Third-order nonlinear optical (NLO) materials
with large effective third-order NLO susceptibilities,
xð3Þ; have applications in a number of important
technologies including power limiting for sensor
protection and optically addressed optical switches
for photonics switching [1]. The design of materials
with large xð3Þ values is challengingly undertaking.
Thus, as a consequence, a major focus of current
*
Corresponding author. Tel.: þ86-555-2400551; fax: þ86-555-
2400552.
E-mail address: zhangqf@ahut.edu.cn (Q.-F. Zhang).
0022-2860/03/$ - see front matter q 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-2860(03)00415-0

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W.-R. Yao et al. / Journal of Molecular Structure 657 (2003) 165–175
the presence of the metal [6]; organometallic
transition metal complexes containing p-conjugated
ligands have the extensive p-electron delocalization
in the ligands [7]; both the skeleton and terminal
elements of the metal clusters can be altered through
structural manipulation [8]. The recent reports of
structure–property relationships in metal–organic
third-order NLO materials have clearly demonstrated
that variations in both the metal and the ligands of
these materials can have significant effects on their
third-order NLO properties [9]. Furthermore, with the
proper combination of metal and ligands, metal–
organic materials exhibits large xð3Þ values which are
compatible to or greater than those reported for
conjugated polymers [10].
2. Experimental
2.1. General
All reactions were performed in oven-dried
glassware under a purified nitrogen atmosphere
using standard Schlenk techniques. The solvents
were purified by conventional methods and degassed
prior to use. Fe3(CO)12 (Strem), Mn2(CO)10 (Strem),
S
powder (Strem), bis(triphenylphosphine)-
nitrogen(1 þ ) chloride [PPN]Cl (Aldrich), and
thiophenol PhSH (Aldrich) were used without
further purification.
Electronic absorption spectra were obtained on a
Shimazu UV-3000 spectrophotometer with n-hexane
as solvent. Infrared spectra were recorded on a Nicolet
170sx FT-IR spectrophotometer as solutions in CaF2
In our recent efforts to search for new NLO
materials, we have investigated the third-order NLO
properties of heterometallic sulfur and selenium
clusters with different structures [11,12]. It has been
noticed that skeleton atom substitution and struc-
tural alteration in clusters may induce large changes
in their NLO properties [13]. An obvious advantage
of these clusters is that the heavy atom effect exists
in clusters, thereby introducing more sublevels into
the energy continuum in comparison to organic
molecules with the same number of skeletal atoms
[14]. Thus, an optimization of the NLO properties
of clusters can be realized through the design of
structural modes and the control of skeleton heavy
atoms. It has also been considerably attended that
the clusters contain the weaker metal–metal bonds
with one more bridging chalcogen ligands, possibly
enhancing the photostability of the cluster during
the optical determination. With these in mind, it is
possible to design the construction of certain
classes of metal–chalcogenide clusters in which
the special NLO properties may be desired. In
continuation of our efforts to understand the
structure–property relationship for metal–organic
NLO materials [13–15], we extend our study to
organometallic clusters containing the bridging
chalcogen ligands, which are expected to possess
rich structural chemistry. Herein, we initially
present the synthesis, structure and NLO properties
of two sulfur-bridged clusters [(m-SPh)2Fe2
(CO)6]2(m4-S) (1) with double butterfly shaped
configuration and [PPN][(m3-S)2Mn3(CO)9] (2)
with triangular structural mode.
1
cells. H NMR spectra were recorded on a Bruker
DPX-300 Fourier-transform spectrometer with refer-
ence to SiMe4. Mass spectra were obtained on a
Finnigan TSQ-700 spectrometer. Elemental analyses
were performed by Medac Ltd, Surrey, UK.
2.2. Preparations
2.2.1. [(m-SPh)2Fe2(CO)6]2(m4-S) 1
A mixture of Fe3(CO)12 (0.61 g, 1.21 mmol),
PhSH (0.16 cm3, 1.21 mmol) and Et3N (0.17 cm3,
1.22 mmol) was dissolved in 20 cm3 of THF and then
stirred overnight, during which time the solution color
changed from green to orange. The solvent was
removed at reduced pressure and the residue was
extracted with petroleum ether. Filtration chromatog-
raphy (silica gel; 10% CH2Cl2–petroleum ether) gave
red solid after evaporation of the solvent, which was
recrystallized from petroleum ether to give red
crystals suitable for X-ray analysis. Yield: 0.54 g
(79%). 1H NMR (CDCl3): d 7.18–7.54 (m, Ph). IR (in
CH2Cl2, cm21): n(CxO) 2075, 2035, 2021, 1992,
1984. UV–Vis (CH2Cl2, lmax (nm), 1023
1
(dm3 mol21 cm21): 344 (25.1), 452 (12.3). MS
(FAB): m/z 810 (Mþ), 390 ([Fe2(CO)6(SPh)] þ 1).
(Found: C, 35.41; H, 1.22. Calcd for C24H10O12S3Fe4:
C, 35.59; H, 1.24%).
2.2.2. [PPN][(m3-S)2Mn3(CO)9] 2
To a mixture of Mn2(CO)10 (0.58 g, 1.48 mmol)
and KOH (0.87 g, 15.54 mmol) was added 25 cm3 of

W.-R. Yao et al. / Journal of Molecular Structure 657 (2003) 165–175
167
MeOH. The mixture solution was stirred at room
Table 1
Crystallographic data for compounds 1 and 2
temperature for 30 min, during which time the
mixture acquired a red color. To this solution was
added 0.096 g sulfur powder (3.00 mmol), and the
reaction turned to reddish brown and was allowed to
stir overnight. The resulting solution was filtered and
concentrated, and an aqueous solution of [PPN]Cl
(1.72 g, 3.00 mmol) was added dropwise, precipitat-
ing the solid. The brown solid was washed with
water and dried by high vacuum. Recrystallization
for CH2Cl2/hexane afforded the reddish brown
crystals suitable for X-ray analysis. Yield: 1.26 g
1
2
Empirical formula
C24H10O12S3Fe4
C45H3ONO9
P2S2Mn3
1019.56
Triclinic
P-1 (no. 2)
16.3545(12)
16.8554(13)
16.9277(14)
84.445(2)
81.902(2)
63.2480(10)
4609.4(6)
4
Formula weight
Crystal system
Space group
˚
a (A)
˚
b (A)
809.90
Triclinic
P-1 (no. 2)
9.1974(17)
15.886(3)
21.172(4)
94.870(4)
91.789(4)
90.528(5)
3080.6(10)
4
˚
c (A)
a (8)
b (8)
g (8)
1
(52%). H NMR (CDCl3): d 7.09–7.64 (m, Ph). IR
(in CH2Cl2, cm21): n(CxO) 1986, 1947, 1908. UV–
Vis (CH2Cl2, lmax (nm), 1023 1 (dm3 mol21 cm21):
329 (21.4), 447 (br, 9.2). MS (FAB): m/z 481
(Mþ 2 PPN), 539 (PPN þ 1). (Found: C, 52.83; H,
2.93; N, 1.35. Calcd for C45H30NO9P2S2Mn3: C,
53.01; H, 2.97; N, 1.37%).
V (A )
3
˚
Z
T
293
293
m(Mo Ka) (mm21
)
2.107
1.023
Dc (g cm23
)
1.746
1.466
Reflections collected
Independent
reflections/R(int)
Final R1,
25453
38192
10792/0.0287
16264/0.0177
0.0357, 0.0778
0.0667, 0.1884
wR2½I . 2sðIÞꢀ
[all data]
2.3. X-ray crystallography
0.0555, 0.0859
0.990
0.0776, 0.2006
1.022
Goodness-of-fit
on F 2
˚
Residual (r=e A
Well developed single-crystals of 1 ð0:20 £
0:10 £ 0:06 mm3Þ and 2 ð0:55 £ 0:40 £ 0:35 mm3Þ
were mounted in random orientation on glass
fibers. Diffraction data were collected on a Bruker
APEX CCD area-detecting diffractometer equipped
with graphite monochromated Mo Ka radiation
23
)
þ0.833, 20.232
þ3.016, 20.711
2.4. Optical measurements
ꢀ
ðl ¼ 0:71073 AÞ by using an v scan technique
A CH2Cl2 solution of the cluster 1 or 2 was placed
in a 5 mm quartz cuvette for optical limiting property
measurements which were performed with linearity
polarized 8 ns pulses at 532 nm generated from a Q-
switched frequency-doubled Nd:YAG laser. The
cluster is stable toward air and laser light under
present experimental conditions. The spatial profiles
of the pulsed laser were focused on the sample cell
with a 15 cm focal length mirror. The spot radius of
the laser beam was measured to be 55 mm (half-width
at 1=e2 maximum). The energies of the input and
output pulses were measured simultaneously by
precision laser detectors (Rjp-735 energy probes)
which were linked to a computer by an IEEE
interface, while the incident energy was varied by a
Newport Com. Attenuator [19]. The interval between
the laser pulses was chosen to 1 s to avoid influence of
thermal and long-term effects.
(for 1, 0:998 , u , 25:078; for 2, 1:008 , u ,
25:038). The collected frames were processed
with the software SAINT [16]. The data was
corrected for absorption using the program
SADABS [17]. Structures were solved by the
direct methods and refined by full-matrix least-
squares on F2 using the SHELXTL software
package [18]. All nonhydrogen atoms were refined
anisotropically. The positions of all hydrogen atoms
were generated geometrically (C–H bond fixed at
˚
0.96 A), assigned isotropic thermal parameters, and
allowed to ride on their respective parent C atoms
before the final cycle of least-squares refinement.
The large peak in the final difference maps had
23
˚
height of 3.016e A for 2 is in the vicinity of the
Mn atoms. Crystallographic data are summarized
in Table 1.

168
W.-R. Yao et al. / Journal of Molecular Structure 657 (2003) 165–175
The effective third-order NLO absorptive and
CH2Cl2 revealed characteristic absorption band of
terminal carbonyl at 2075, 2035, 2021, 1992 and
1984 cm21. The proton NMR spectrum in CDCl3
presents a mutilplet at d 7.18–7.54 ppm which was
assigned to the phenyl ring protons. Treatment of
dimanganese decacarbonyl with two equiv of sulfur
powder in the presence of strong base gave the
trimanganese cluster [PPN][(m3-S)2Mn3(CO)9] (2)
with sulfur-bridging. The IR spectrum of 2 in
CH2Cl2 showed strong absorption band of terminal
refractive properties of clusters 1 and 2 were recorded
by moving the sample along the axis of the incident
laser beam (z direction), with respect to the focal point
instead of being positioned at its focal point, and an
identical set-up was adopted in the experiments to
measure the z-scan data. An aperture of 0.5 mm radius
was placed in front of the detector to assist the
measurement of the NLO absorption and refraction
effect.
carbonyl at 1986, 1947, and 1908 cm21
.
3. Results and discussion
3.2. Structure
3.1. Synthesis
The molecular structure of 1 is shown in Fig. 1,
selected bond lengths and angles are list in Table 2.
Cluster 1 crystallizes in the triclinic crystal system.
There are two perpendicular arrangements of the
molecules in the crystal with slightly different
conformations. No significant differences in bonding
parameters between these two molecules (A and B)
were found. Each molecular can be described as
consisting of two doubly bridged Fe2(CO)6 units
The reaction of Fe3(CO)12 with thiophenol in the
presence of an excess of base gave an orange material.
The pure red solid of [(m-SPh)2Fe2(CO)6]2(m4-S) (1)
was isolated in a yield of 79% by chromatography
(silica gel; 10% CH2Cl2–petroleum ether) technique.
The m4-S atom is considered to come from the rupture
of the C–S bond in PhSH. The IR spectrum of 1 in
Fig. 1. A view of cluster 1, showing the perpendicular arrangements of two molecules in the crystal.

W.-R. Yao et al. / Journal of Molecular Structure 657 (2003) 165–175
169
Table 2
Selected bond length (A) and angles (8) for 1
Table 2 (continued)
˚
Molecule A
Molecule B
Molecule A
Molecule B
C(31)–Fe(3)–S(3) 160.69(13) C(71)–Fe(7)–S(6) 160.16(12)
C(33)–Fe(3)–S(3) 94.04(13) C(73)–Fe(7)–S(6) 96.06(12)
C(32)–Fe(3)–S(3) 98.64(12) C(72)–Fe(7)–S(6) 99.39(11)
C(31)–Fe(3)–Fe(4) 104.63(13) C(71)–Fe(7)–Fe(8) 104.11(12)
C(33)–Fe(3)–Fe(4) 99.77(14) C(73)–Fe(7)–Fe(8) 101.74(12)
C(32)–Fe(3)–Fe(4) 148.44(11) C(72)–Fe(7)–Fe(8) 148.88(11)
C(41)–Fe(4)–S(1) 91.17(14) C(81)–Fe(8)–S(4) 88.87(12)
C(43)–Fe(4)–S(1) 153.00(15) C(83)–Fe(8)–S(4) 154.58(12)
C(42)–Fe(4)–S(1) 108.42(13) C(82)–Fe(8)–S(4) 106.56(14)
C(41)–Fe(4)–S(3) 159.41(13) C(81)–Fe(8)–S(6) 156.65(12)
C(43)–Fe(4)–S(3) 93.10(13) C(83)–Fe(8)–S(6) 94.25(12)
C(42)–Fe(4)–S(3) 100.03(12) C(82)–Fe(8)–S(6) 100.50(13)
C(41)–Fe(4)–Fe(3) 103.39(13) C(81)–Fe(8)–Fe(7) 100.19(12)
C(43)–Fe(4)–Fe(3) 97.87(14) C(83)–Fe(8)–Fe(7) 99.57(12)
C(42)–Fe(4)–Fe(3) 151.91(12) C(82)–Fe(8)–Fe(7) 151.55(13)
Fe(1)–S(1)
Fe(1)–S(2)
Fe(2)–S(1)
Fe(2)–S(2)
Fe(3)–S(1)
Fe(3)–S(3)
Fe(4)–S(1)
Fe(4)–S(3)
Fe(1)–Fe(2)
Fe(3)–Fe(4)
Fe–C(CO) (av)
2.2565(11) Fe(5)–S(4)
2.2696(10) Fe(5)–S(5)
2.2365(11) Fe(6)–S(4)
2.2684(10) Fe(6)–S(5)
2.2449(10) Fe(7)–S(4)
2.2660(10) Fe(7)–S(6)
2.2440(11) Fe(8)–S(4)
2.2668(10) Fe(8)–S(6)
2.5189(8) Fe(5)–Fe(6)
2.5319(8) Fe(7)–Fe(8)
2.2398(10)
2.2728(11)
2.2353(10)
2.2674(11)
2.2406(9)
2.2791(10)
2.2293(10)
2.2694(11)
2.5206(8)
2.5251(7)
1.810(4)
1.790(4)
Fe–C(CO) (av)
S(1)–Fe(1)–S(2)
S(1)–Fe(2)–S(2)
S(1)–Fe(3)–S(3)
S(1)–Fe(4)–S(3)
S(1)–Fe(1)–Fe(2)
S(2)–Fe(1)–Fe(2)
S(1)–Fe(2)–Fe(1)
S(2)–Fe(2)–Fe(1)
S(1)–Fe(3)–Fe(4)
S(3)–Fe(3)–Fe(4)
S(1)–Fe(4)–Fe(3)
S(3)–Fe(4)–Fe(3)
Fe(2)–S(1)–Fe(4)
Fe(2)–S(1)–Fe(3)
Fe(4)–S(1)–Fe(3)
Fe(2)–S(1)–Fe(1)
Fe(4)–S(1)–Fe(1)
Fe(3)–S(1)–Fe(1)
Fe(2)–S(2)–Fe(1)
Fe(3)–S(3)–Fe(4)
76.85(4)
77.28(4)
76.93(3)
76.93(4)
55.53(3)
56.26(3)
56.28(3)
56.31(3)
55.65(3)
56.06(3)
55.68(3)
56.03(3)
S(4)–Fe(5)–S(5)
S(4)–Fe(5)–Fe(6)
S(4)–Fe(6)–S(5)
S(4)–Fe(7)–S(6)
S(4)–Fe(8)–S(6)
S(4)–Fe(6)–Fe(5)
S(5)–Fe(5)–Fe(6)
S(5)–Fe(6)–Fe(5)
S(4)–Fe(7)–Fe(8)
S(6)–Fe(7)–Fe(8)
S(4)–Fe(8)–Fe(7)
S(6)–Fe(8)–Fe(7)
75.40(4)
55.63(3)
75.60(4)
77.27(3)
77.70(3)
55.80(3)
56.18(3)
56.38(3)
55.39(3)
56.10(3)
55.82(3)
56.46(3)
131.81(4)
139.43(4)
68.56(3)
68.79(3)
134.33(4)
126.54(4)
67.44(3)
67.44(3)
sharing a common central sulfur atom ligand. The
two Fe2(CO)6 units also bridge by equatorial SPh
ligands. The coordination about the central sulfur
atom is distortedly tetrahedral, indicated by the
bond angles of Fe–S(center)–Fe varying from
67.92(3) to 136.05(6)8. The molecular geometry is
very similar to those of the previously reported
complexes, namely symmetrical [(m-SR)2Fe2
(CO)6]2(m4-S) (R ¼ Me, Et and CH2Ph) [20–22]
and the unsymmetrical [(m-SR1)(m-SR2)Fe2(CO)6]2
(m4-S) (R1 ¼ t-Bu, R2 ¼ CH2Ph; R1 ¼ Et, R2 ¼ Ph)
[23,24].
136.05(4) Fe(8)–S(4)–Fe(6)
133.65(4) Fe(8)–S(4)–Fe(5)
68.67(3)
68.20(3)
Fe(6)–S(4)–Fe(5)
Fe(8)–S(4)–Fe(7)
134.22(4) Fe(6)–S(4)–Fe(7)
128.32(4) Fe(5)–S(4)–Fe(7)
67.43(3)
67.92(3)
Fe(6)–S(5)–Fe(5)
Fe(8)–S(6)–Fe(7)
The average Fe–S(center) bond length in 1 is
C(13)–Fe(1)–S(1) 90.63(13) C(53)–Fe(5)–S(4) 89.64(14)
C(11)–Fe(1)–S(1) 156.29(14) C(51)–Fe(5)–S(4) 154.83(17)
C(12)–Fe(1)–S(1) 105.51(12) C(52)–Fe(5)–S(4) 104.84(14)
C(13)–Fe(1)–S(2) 157.33(15) C(53)–Fe(5)–S(5) 158.31(14)
C(11)–Fe(1)–S(2) 94.12(12) C(51)–Fe(5)–S(5) 94.93(16)
C(12)–Fe(1)–S(2) 103.65(14) C(52)–Fe(5)–S(5) 99.62(15)
C(13)–Fe(1)–Fe(2) 101.07(15) C(51)–Fe(5)–Fe(6) 99.57(16)
C(11)–Fe(1)–Fe(2) 101.17(13) C(53)–Fe(5)–Fe(6) 102.43(14)
C(12)–Fe(1)–Fe(2) 153.02(13) C(52)–Fe(5)–Fe(6) 150.22(14)
C(23)–Fe(2)–S(1) 89.86(13) C(63)–Fe(6)–S(4) 89.12(12)
C(21)–Fe(2)–S(1) 152.91(14) C(61)–Fe(6)–S(4) 154.50(17)
C(22)–Fe(2)–S(1) 107.81(15) C(62)–Fe(6)–S(4) 106.99(14)
C(23)–Fe(2)–S(2) 160.19(15) C(63)–Fe(6)–S(5) 156.73(13)
C(21)–Fe(2)–S(2) 94.24(13) C(61)–Fe(6)–S(5) 95.46(16)
C(22)–Fe(2)–S(2) 98.84(14) C(61)–Fe(6)–Fe(5) 99.23(17)
C(23)–Fe(2)–Fe(1) 104.01(15) C(62)–Fe(6)–S(5) 103.03(13)
C(21)–Fe(2)–Fe(1) 97.51(14) C(63)–Fe(6)–Fe(5) 100.53(13)
C(22)–Fe(2)–Fe(1) 151.18(14) C(62)–Fe(6)–Fe(5) 154.11(13)
C(31)–Fe(3)–S(1) 92.08(13) C(71)–Fe(7)–S(4) 90.28(12)
C(33)–Fe(3)–S(1) 154.86(14) C(73)–Fe(7)–S(4) 156.12(13)
C(32)–Fe(3)–S(1) 103.85(12) C(72)–Fe(7)–S(4) 104.10(11)
˚
2.2455(10) A. In the binuclear fragments of
molecular A, the Fe atoms are bonded by normal
˚
Fe–Fe bonds (2.5159(8) and 2.5319(8) A), and also
with a bridging S atom of the SPh ligand. The
˚
average Fe–S(Ph) bond length is 2.2677(10) A and
the average angles of Fe–S(Ph)–Fe and Fe–S(Ph)–
C are 67.9(1) and 115.2(4)8, respectively. In addition,
each Fe atom is coordinated with three terminal
carbonyl groups. The average Fe–C(O) and C–O
˚
bond lengths are 1.790(4) and 1.133(5) A, respect-
ively, so that the Fe outermost electron shell, contain
18 electrons. The coordination polyhedron around
the iron is a distorted tetragonal bypyramid with two
carbonyls and two sulfur atoms at equatorial
positions and the other carbonyl and iron atoms at
axial positions. As expected, the four iron atoms are
˚
displaced by ca 0.42 A from their respective

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W.-R. Yao et al. / Journal of Molecular Structure 657 (2003) 165–175
equatorial places in the direction of their axial
carbonyl group. Similar displacements of the iron
atoms were also observed in [(m-SEt)2Fe2(CO)6]2
is also reflected in the S–Mn–S angles, which are
very close to 908. The separation of two sulfur atoms
˚
of 3.372 A is two long, considerably being
nonbonding.
˚
(m4-S) (0.37 A for four irons) [21] and [(m-SMe)2Fe2
˚
(CO)6]2(m4-S) (0.36 A for four irons) [24]. The
dihedral angles between Fe2S planes in molecule
A are 93.64 and 92.358, and an angle of between
Fe2S plane in the Fe4S tetrahedron is 84.28.
3.3. NLO properties
Clusters 1 and 2 were synthesized for the study of
their NLO properties, thus, the NLO properties of
both clusters with different structure types were
investigated by using the z-scan technique. The z-
scan results without and with the aperture are given
in Figs. 3 and 4, respectively. Figs. 3(a) and 4(a)
clearly illustrates that the absorption increases as the
incident light irradiance rises, which are the charac-
teristics of reverse saturable absorption (RSA)
process. Based on the previous time-resolved non-
linear transmission studies [28], we found that the
nonlinear absorption decreases as the pulse time
range elongates. The origin of the observed RSA in
clusters 1 and 2 can be attributed to excited-state
absorption. Figs. 3(b) and 4(b) indicate the refractive
nonlinearities of cluster 1 and 2. To obtain the NLO
parameters, we employed a z-scan theory that
considers effective nonlinearity of third-order nature.
The nonlinear absorption components were
evaluated by z-scan method under an open aperture
The molecular structure of anion in 2 is shown in
Fig. 2, selected bond lengths and angles are list in
Table 3. Cluster 2 also crystallizes in the triclinic
crystal system, containing two perpendicular arrange-
ments in the molecular structure. Cluster anion of 2
exhibits a structural feature of the near-idealized D3h
trigonal-bipyramidal frame. The three Mn–Mn bonds
are nearly equal (2.7688(10), 2.7695(11) and
˚
2.7637(10) A for molecule A, 2.7684(14),
˚
2.7623(10) and 2.7595(14) A for molecule B) and
three Mn–Mn–Mn angles are very close to 608. The
˚
average Mn–S bond length of 2.2455(12) A in cluster
2 is in agreement with that in a similar trigonal-Mn
˚
cluster [Ph4P][(m3-S)2Mn3(CO)9] (av 2.2455(15) A)
[25], but slightly shorter than those in the bridging
disulfido clusters such as [PPN][S8C2Mn2(CO)6] (av
˚
2.374(3) A) [26] and [Ph3PMe][[Mn3(CO)10(m3-S2)2]
˚
(av 2.356(2) A) [27]. The high symmetry of the
biscapped metal plane and strong Mn–Mn interaction
Fig. 2. A view of anion in cluster 2, showing the perpendicular arrangements of two anions in the crystal.

W.-R. Yao et al. / Journal of Molecular Structure 657 (2003) 165–175
171
Table 3
˚
Selected bond length (A) and angles (8) for 2
Molecule A
Molecule B
Mn(1)–S(1)
Mn(1)–S(2)
Mn(2)–S(1)
Mn(2)–S(2)
Mn(3)–S(1)
Mn(3)–S(2)
Mn(1)–Mn(2)
Mn(1)–Mn(3)
Mn(2)–Mn(3)
Mn–C (av)
2.2386(13)
2.2468(14)
2.2227(12)
2.2399(13)
2.2365(14)
2.2585(15)
2.7688(10)
2.7695(11)
2.7637(10)
1.797(6)
Mn(4)–S(4)
Mn(4)–S(3)
Mn(5)–S(4)
Mn(5)–S(3)
Mn(6)–S(3)
Mn(6)–S(4)
Mn(4)–Mn(6)
Mn(4)–Mn(5)
Mn(5)–Mn(6)
Mn–C (av)
2.2188(14)
2.2550(16)
2.2170(14)
2.2393(14)
2.2788(16)
2.1934(15)
2.7684(14)
2.7623(16)
2.7595(14)
1.828(8)
Mn(2)–Mn(1)–Mn(3)
Mn(3)–Mn(2)–Mn(1)
Mn(2)–Mn(3)–Mn(1)
Mn(2)–S(1)–Mn(3)
Mn(2)–S(1)–Mn(1)
Mn(3)–S(1)–Mn(1)
Mn(2)–S(2)–Mn(1)
Mn(2)–S(2)–Mn(3)
Mn(1)–S(2)–Mn(3)
S(1)–Mn(1)–S(2)
59.87(3)
60.08(3)
60.05(3)
76.60(4)
76.72(4)
76.46(4)
76.21(4)
75.81(4)
75.86(5)
88.91(5)
89.49(5)
88.67(5)
51.38(3)
51.78(4)
51.73(4)
52.26(4)
51.93(4)
52.40(4)
51.48(3)
51.79(4)
51.80(4)
51.88(4)
148.1(2)
110.34(17)
109.2(2)
88.3(2)
Mn(6)–Mn(4)–Mn(5)
Mn(6)–Mn(5)–Mn(4)
Mn(4)–Mn(6)–Mn(5)
Mn(5)–S(3)–Mn(4)
Mn(5)–S(3)–Mn(6)
Mn(4)–S(3)–Mn(6)
Mn(6)–S(4)–Mn(5)
Mn(6)–S(4)–Mn(4)
Mn(5)–S(4)–Mn(4)
S(4)–Mn(4)–S(3)
60.22(4)
59.46(4)
60.32(4)
75.85(5)
75.28(5)
74.31(5)
77.46(5)
76.72(5)
77.03(5)
89.08(6)
89.52(5)
89.10(5)
51.45(4)
51.82(4)
51.22(4)
53.24(5)
50.89(4)
53.01(4)
51.51(4)
52.33(4)
52.05(4)
52.45(4)
142.8(4)
111.7(2)
103.8(2)
82.7(4)
S(1)–Mn(2)–S(2)
S(4)–Mn(5)–S(3)
S(1)–Mn(3)–S(2)
S(4)–Mn(6)–S(3)
S(1)–Mn(1)–Mn(2)
S(2)–Mn(1)–Mn(2)
S(1)–Mn(1)–Mn(3)
S(2)–Mn(1)–Mn(3)
S(1)–Mn(2)–Mn(3)
S(2)–Mn(2)–Mn(3)
S(1)–Mn(3)–Mn(2)
S(2)–Mn(3)–Mn(2)
S(1)–Mn(3)–Mn(1)
S(2)–Mn(3)–Mn(1)
C(3)–Mn(1)–Mn(2)
C(2)–Mn(1)–Mn(2)
C(1)–Mn(1)–Mn(2)
C(3)–Mn(1)–Mn(3)
C(2)–Mn(1)–Mn(3)
C(1)–Mn(1)–Mn(3)
C(4)–Mn(2)–Mn(3)
C(5)–Mn(2)–Mn(3)
C(6)–Mn(2)–Mn(3)
C(4)–Mn(2)–Mn(1)
C(5)–Mn(2)–Mn(1)
C(6)–Mn(2)–Mn(1)
C(7)–Mn(3)–Mn(2)
C(9)–Mn(3)–Mn(2)
C(8)–Mn(3)–Mn(2)
C(7)–Mn(3)–Mn(1)
C(9)–Mn(3)–Mn(1)
C(8)–Mn(3)–Mn(1)
S(4)–Mn(4)–Mn(5)
S(3)–Mn(4)–Mn(5)
S(4)–Mn(4)–Mn(6)
S(3)–Mn(4)–Mn(6)
S(4)–Mn(5)–Mn(6)
S(3)–Mn(5)–Mn(6)
S(4)–Mn(5)–Mn(4)
S(3)–Mn(5)–Mn(4)
S(4)–Mn(6)–Mn(4)
S(3)–Mn(6)–Mn(4)
C(12)–Mn(4)–Mn(6)
C(11)–Mn(4)–Mn(6)
C(10)–Mn(4)–Mn(6)
C(12)–Mn(4)–Mn(5)
C(11)–Mn(4)–Mn(5)
C(10)–Mn(4)–Mn(5)
C(15)–Mn(5)–Mn(4)
C(14)–Mn(5)–Mn(4)
C(13)–Mn(5)–Mn(4)
C(15)–Mn(5)–Mn(6)
C(14)–Mn(5)–Mn(6)
C(13)–Mn(5)–Mn(6)
C(18)–Mn(6)–Mn(4)
C(16)–Mn(6)–Mn(4)
C(17)–Mn(6)–Mn(4)
C(18)–Mn(6)–Mn(5)
C(16)–Mn(6)–Mn(5)
C(17)–Mn(6)–Mn(5)
134.16(17)
136.42(19)
146.4(2)
111.77(17)
107.97(18)
86.4(2)
134.8(2)
135.5(2)
142.2(4)
111.3(2)
107.7(3)
82.8(4)
133.99(17)
135.33(19)
86.53(19)
132.2(3)
134.8(3)
146.52(19)
110.7(2)
108.3(2)
132.3(2)
135.8(2)
81.2(3)
132.5(3)
134.8(3)
145.1(3)
111.4(2)
106.5(3)
(continued on next page)

172
W.-R. Yao et al. / Journal of Molecular Structure 657 (2003) 165–175
Table 3 (continued)
Molecule A
Molecule B
C(3)–Mn(1)–S(1)
C(2)–Mn(1)–S(1)
C(1)–Mn(1)–S(1)
C(3)–Mn(1)–S(2)
C(2)–Mn(1)–S(2)
C(1)–Mn(1)–S(2)
C(4)–Mn(2)–S(1)
C(5)–Mn(2)–S(1)
C(6)–Mn(2)–S(1)
C(4)–Mn(2)–S(2)
C(5)–Mn(2)–S(2)
C(6)–Mn(2)–S(2)
C(7)–Mn(3)–S(1)
C(9)–Mn(3)–S(1)
C(8)–Mn(3)–S(1)
C(7)–Mn(3)–S(2)
C(9)–Mn(3)–S(2)
C(8)–Mn(3)–S(2)
111.4(3)
C(12)–Mn(4)–S(4)
C(11)–Mn(4)–S(4)
C(10)–Mn(4)–S(4)
C(12)–Mn(4)–S(3)
C(11)–Mn(4)–S(3)
C(10)–Mn(4)–S(3)
C(15)–Mn(5)–S(4)
C(14)–Mn(5)–S(4)
C(13)–Mn(5)–S(4)
C(15)–Mn(5)–S(3)
C(14)–Mn(5)–S(3)
C(13)–Mn(5)–S(3)
C(18)–Mn(6)–S(4)
C(16)–Mn(6)–S(4)
C(17)–Mn(6)–S(4)
C(18)–Mn(6)–S(3)
C(16)–Mn(6)–S(3)
C(17)–Mn(6)–S(3)
110.8(4)
87.5(2)
86.04(16)
156.0(2)
155.7(2)
107.2(3)
160.3(3)
84.6(2)
108.7(3)
158.53(19)
86.81(19)
109.67(19)
86.23(17)
155.7(2)
107.1(3)
85.5(2)
155.2(3)
104.4(3)
160.6(3)
84.8(2)
106.84(19)
160.93(18)
85.65(18)
109.97(18)
84.8(2)
109.7(3)
85.9(3)
156.5(3)
155.7(2)
101.0(3)
162.6(2)
85.7(3)
106.99(17)
160.3(2)
85.7(3)
configuration and the NLO absorptive experimental
data for clusters 1 and 2 obtained under the
conditions. Theoretical curves of transmittance
against the z-position, Eqs. (1) and (2), were
DTV–P are 0.96 and 0.59 for 1 and 2, respectively. An
effective third-order nonlinear refractive index n2 of
clusters 1 and 2 can be derived from the difference
between normalized transmittance values at valley
and peak position ðTV–PÞ by use of Eq. (3)
ð1
2
TðZÞ ¼
ln½1 þ qðzÞꢀe2t dt
ð1Þ
ð2Þ
1
p1=2qðZÞ
la0
21
n2 ¼
DTV–P
ð3Þ
0
0:812pIð1 2 e2a L
Þ
0
ð1 2 e2a L
Þ
qðZÞ ¼ a2IiðZÞ
a0
With the measured values of the difference of
normalized transmittance values at valley and peak
positions DTV–P and nonlinear absorptive values, the
NLO refractive indices n2 were calculated to be
4.2 £ 10211 esu for 1 and 7.6 £ 10212 esu for 2,
respectively.
fitted to the observed z-scan data by varying the
effective third-order NLO absorptivity a2 value,
where the experimentally measured a0 (linear
absorptivity), L (the optical path of sample) and
IiðZÞ (the on-axis irradiance at z-position) were
adopted. The solid lines in Figs. 3(a) and 4(a) are
the theoretical curve calculated with a2 ¼ 7:42 £
The positive values of the NLO refractive effects of
clusters 1 and 2 indicate that there are self-focusing
effects in the NLO refractive behavior. In accordance
with the observed a2 and n2 values, the modulus of the
effective third-order susceptibility xð3Þ can be calcu-
lated by Eq. (4)
10210 and 4.15 £ 10211 m/W for clusters
1
(5.5 £ 1023 mol/dm3) and 2 (6.8 £ 1023 mol/dm3),
respectively.
The nonlinear refractive properties of clusters 1
and 2 were assessed by dividing the normalized z-scan
data obtained under the closed aperture configuration
by the normalized z-scan data obtained under the open
aperture configuration. The valley and peak occur at
about equal distances from the focus. It can be seen
that the difference in valley–peak positions DZV–P is
10 mm and the differences between the normalised
transmittance values at the valley and peak position
vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
u
u
t
2
8
2
0
2
2
9 £ 10 1n c
cn
0
ð3Þ
lx l ¼
ꢀ
a2ꢀ þ ꢀ
n2ꢀ
ð4Þ
ꢀ
ꢀ
ꢀ
ꢀ
2n
80p
where n is frequency of the laser light, n0 is the linear
refractive index of the sample, 10 and c are the
permittivity and the speed of the light in a vacuum,
respectively. The xð3Þ parameters were calculated to

W.-R. Yao et al. / Journal of Molecular Structure 657 (2003) 165–175
173
Fig. 4. z-Scan of cluster 2. Up: open-aperture data; down: closed-
aperture data. Solid curves are the best numerical fits.
Fig. 3. z-Scan of cluster 1. Up: open-aperture data; down: closed-
aperture data. Solid curves are the best numerical fits.
be 5.4 £ 10213 and 1.2 £ 10213 esu for 1 and 2,
respectively, with the concentration of 5.5 £ 1023 and
6.8 £ 1023 mol/dm3 for 1 and 2, respectively.
a m3-sulfur bridge [29]. One example of selenium-
bridged iron carbonyl clusters, [Fe2(CO)6Se2{m-
(CO)3Cr(h5-C5H(CH2Ph)(Ph)(OEt)}], having the
butterfly unit of Fe2(CO)6(m-Se)2, is of interesting
nonlinear refraction effect and large optical limiting
ability [30]. In the contrast, cluster 2 has a triangular
configuration of metal atoms. Its NLO behavior is
obviously inferior to those of clusters with butterfly
shaped configuration. Although we cannot highly
systematize structure–property relationship to date
Comparing the NLO data of clusters 1 and 2, the
nonlinear absorption and refraction capabilities of 1
are stronger than those of 2. Cluster 1 has an open
double butterfly like structure with a m4-sulfur center,
it is also noted that strong NLO behavior has been
found for a butterfly shaped thiometallic cluster
[MCu2OS3(PPh3)n] (M ¼ Mo, W, n ¼ 3,4) with

174
W.-R. Yao et al. / Journal of Molecular Structure 657 (2003) 165–175
due to a few examples for comparison, the influence
of structural variation on the NLO properties of
clusters is apparent.
References
[1] S.P. Karna, A.T. Yeates, Nonlinear Optical Materials,
American Chemical Society, Washington, DC, 1996, and
reference therein.
Early attempts to study the optical nonlinearity of
metal carbonyl clusters, such as Ru3(CO)12,
Os3(CO)9, and Ir4(CO)12, have failed due to their
photoinstability [31]. Photoexcitation by laser pulses
causes facile M–M bond cleavage of the clusters
without the bridging chalcogen ligands. However,
we have noticed that a mixed-metal carbonyl
cluster [(h-C5H5)CoFe2SSe(CO)6] with chalcogen-
ide bridges displays superior performance and
photostability [32]. As expected, the current both
clusters also show the relatively good photostability
during the optical determination because of the
weaker metal–metal bonds stabilized by one more
bridging chalcogen ligands. No obvious change of
the absorption peaks and the vibration wavelengths
of characteristic carbonyl were, respectively, found
in the UV–Vis spectra and in the solution IR
spectra of clusters during the optical measurements.
Thus, it may become a route to synthesize the
designed clusters with bridging chalcogen ligands
for our further understanding of the structure–
property relationship.
[2] A. Miller, K.R. Welford, B. Daino, Nonlinear Optical Materials
and Devices for Applications in Information Technology,
Kluwer Academic, Dordrecht, The Netherlands, 1993.
[3] N.J. Long, Angew. Chem., Int. Ed. Engl. 34 (1995) 21.
[4] P.N. Prasad, D.J. Williams, Introduction to Nonlinear Optical
Effects in Molecules and Polymers, Wiley, New York, 1991.
[5] D.M. Roundhill, J.P. Fackler Jr, Optoelectronic Properties of
Inorganic Compounds, Plenum Press, New York, 1999.
[6] Z.H. Kafafi, J.R. Lindle, C.S. Weisbecker, F.J. Bartoli, J.S.
Shirk, T.H. Yoon, O.J. Kim, Chem. Phys. Lett. 179 (1991) 79.
[7] M.E. Thompson, W. Chiang, L.K. Meyers, C. Langhoff, SPIE
Proc. 1497 (1991) 423.
[8] I.W. Tutt, S.W. McCahon, Opt. Lett. 15 (1990) 700.
[9] S. Shi, Z.Y. Lin, Y. Mo, X.Q. Xin, J. Phys. Chem. 100 (1996)
10696.
[10] N.J. Long, in: D.M. Roundhill, J.P. Fackler Jr (Eds.),
Organometallic for Nonlinear Optics in Optoelectronic
Properties of Inorganic Compounds, Plenum Press, New
York, 1999, pp. 107–167.
[11] Q.F. Zhang, W.H. Leung, X.Q. Xin, Coord. Chem. Rev. 224
(2002) 35.
[12] Q.F. Zhang, Y. Niu, W.H. Leung, Y. Song, I.D. Williams,
X.Q. Xin, Chem. Commun. (2001) 1126.
[13] S. Shi, W. Ji, W. Xie, T.C. Chong, H.C. Zeng, J.P. Lang, X.Q.
Xin, Mater. Chem. Phys. 39 (1995) 298.
[14] S. Shi, W. Ji, S.H. Tang, J.P. Lang, X.Q. Xin, J. Am. Chem.
Soc. 116 (1994) 3615.
[15] Q.F. Zhang, M.T. Bao, M.C. Hong, R. Cao, Y.L. Song, X.Q.
Xin, J. Chem. Soc., Dalton Trans. (2000) 605.
4. Supplementary materials
[16] Bruker, SMART and SAINT þ , Version 6.02a, Siemens
Analytical X-ray Instruments Inc., Madison, Wisconsin, USA,
1998.
Crystal data (excluding structure factors) for the
structures in this paper have been deposited with the
Cambridge Crystallographic Data Centre as sup-
plementary publication no. CCDC-0119/206679-80
and also available from the corresponding author.
¨
[17] G.M. Sheldrick, SADABS, University of Gottingen, Germany,
1996.
[18] G.M. Sheldrick, SHELXTL Software Reference Manual.
Version 5.1, Bruker AXS Inc., Madison, Wisconsin, USA,
1997.
[19] M. Sheik-Bahae, A.A. Said, T.H. Wei, D.J. Hagan, E.W. Van
Stryland, IEEE J. Quant. Electron. 26 (1990) 760.
[20] J.M. Coleman, A. Wojcicki, P.J. Pollick, L.F. Dahl, Inorg.
Chem. 6 (1967) 1236.
Acknowledgements
[21] L.C. Song, M. Kadiate, J.T. Wang, R.J. Wang, H.G. Wang,
J. Organomet. Chem. 340 (1988) 239.
[22] R.E. Marsh, Acta Crystallogr. B51 (1996) 897.
[23] L.C. Song, C.G. Yan, Q.M. Hu, R.J. Wang, T.C.W. Mak,
Organometallics 15 (1996) 1535.
This project was sponsored by the Scientific
Research Foundation for the Returned Overseas
Chinese Scholars, State Education Ministry of
China. Supports from Anhui Provincial Natural
Science Foundation (00045105) and the Natural
Science Foundation of Shandong Province
(Y2000B05) are also acknowledged.
[24] Z.X. Wang, C.S. Jia, Z.Y. Zhou, X.G. Zhou, J. Organomet.
Chem. 580 (1999) 201.
[25] Z.G. Fang, T.S.A. Hor, K.F. Mok, S.C. Ng, L.K. Liu, Y.S.
Wen, Organometallics 12 (1993) 1009.
[26] M. Shieh, H.S. Chen, H.Y. Yang, S.F. Lin, C.H. Ueng, Chem.
Eur. J. 7 (2001) 3152.

W.-R. Yao et al. / Journal of Molecular Structure 657 (2003) 165–175
175
[27] R.D. Adams, S.B. Miao, J. Organomet. Chem. 665 (2003) 43.
[28] W. Ji, H.J. Du, S.H. Tang, S. Shi, J. Opt. Soc. Am. B12 (1995)
126.
[31] S. Shi, in: D.M. Roundhill, J.P. Fackler Jr. (Eds.), Nonlinear
Optical Properties of Inorganic Clusters in Optoelectronic
Properties of Inorganic Compounds, Plenum Press, New York,
1999, pp. 55–105.
[29] S. Shi, H.W. Hou, X.Q. Xin, J. Phys. Chem. 99 (1995) 4050.
[30] R. Philip, G.R. Kumar, P. Mathur, S. Ghosh, Chem. Phys. Lett.
313 (1999) 719.
[32] S. Banerjee, G.R. Kumar, P. Mathur, P. Sekar, Chem.
Commun. (1997) 299.