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Cite this: J. Mater. Chem. C,
2024, 12, 1958

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Impact of substituent position on crystal structure
and photoconductivity in 1D and 2D lead(II)benzenethiolate coordination polymers†
Ryohei Akiyoshi,
Daisuke Tanaka*a Akinori Saeki,*ab

Kazuyoshi OgasawaraaandCoordination polymers containing a sulfur coordination atom (S-CPs) are an emerging class of materials
with unique optoelectronic properties resulting from their inorganic metal–sulfur (–M–S–)n networks.
Although the structural dimensionalities of (–M–S–)n networks govern the semiconductive properties of
S-CPs, few systematic investigations have examined the impact of these dimensionalities on their semiconductive nature. In this study, we explored the relationship between the (–Pb–S–)n dimensionality
and photoconductivity. We systematically synthesized Pb(II) S-CPs with the formula [Pb(x-SPhOMe)2](x = ortho (KGF-32), meta (KGF-33), and para (KGF-34); HSPhOMe = methoxybenzenthiol). Singlecrystal X-ray diffraction showed that KGF-32 and KGF-34 featured holodirected coordination spheres,but 1D (–Pb–S–)n chains with [PbO2S4] octahedra and 2D (–Pb–S–)n layers with [PbS6] octahedra,
Received 26th November 2023,
Accepted 25th December 2023
DOI: 10.1039/d3tc04362b

respectively. In contrast, KGF-33 features a 1D (–Pb–S–)n chain comprising a hemidirected [PbS5] coordination sphere. Notably, time-resolved microwave conductivity measurements and first-principles calculations revealed that the 2D-extended (–Pb–S–)n layer with the holodirected [PbS6] octahedronobserved in KGF-34 served as a pathway for electron mobility. The findings of this study provide further

rsc.li/materials-c

design strategies for fabricating highly photoconductive Pb(II) S-CPs.

Introduction
Coordination polymers containing a sulfur coordination atom
(S-CPs)1–5 have attracted increasing attention because of theirpotential applications in photocatalysts,6–8 gas sensors,9–11 andelectronic devices.12–14 The inorganic (–M–S–)n structures of the
S-CPs induce unique optoelectronic properties such as visiblelight absorption and high charge mobility.15,16 As the structuraldimensionalities of the (–M–S–)n networks significantly affectthe band gap energies and charge mobilities of S-CPs,17 theengineering of the (–M–S–)n network structure based on theaDepartment of Chemistry, School of Science, Kwansei Gakuin University, 1 Gakuen
Uegahara, Sanda, Hyogo 669-1330, Japan. E-mail: r.akiyoshi@kwansei.ac.jp,
dtanaka@kwansei.ac.jpbDepartment of Applied Chemistry, Graduate School of Engineering, Osaka
University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan† Electronic supplementary information (ESI) available: SEM textures, crystallographic data, asymmetric units, bond length, coordination mode of SPhOMeanions, structure focusing on (–Pb–S–)n network, packing structure, dinuclear
unit of KGF-33, 2D layer stacking of KGF-34, simulated and experimental PXRD
patterns, TGA results, PXRD patters after immersing in various solvents, PYS
results, TRMC results of KGF-32 and KGF-33, TRMC results of photoconductive SCPs, distribution of the VBM and CBM. CCDC 2308865–2308867. For ESI andcrystallographic data in CIF or other electronic format see DOI: https://doi.org/10.
1039/d3tc04362b

1958 | J. Mater. Chem. C, 2024, 12, 1958–1964

precise design of organic ligand moieties is crucially importantfor fine-tuning semiconductive properties. However, to date,there have been few systematic investigations into the tuning ofthe (–M–S–)n dimensionalities of S-CPs.
Benzenethiol derivatives (HSPhX, X = substituents) are promising organic ligands for the construction of S-CPs with a(–M–S–)n network. The HSPh-derived ligands have facile
potential for modification, thus yielding 1D,18–20 2D,12,21,22
and 3D (–M–S–)n networks23–25 that serve as pathways for charge
delocalization.5 For example, S-CPs containing 3d transition
metal ions (i.e. Mn2+, Fe2+, and Co2+) often exhibit 1D architectures with 1D (–M–S–)n chains.26–28 Conversely, S-CPs with d10
coinage metal ions (i.e., Cu+, Ag+, and Au+) undergo a (–M–S–)ndimensionality change depending on substituent species.12,18,29
A recent report also showed that the electron-donating ability ofthe substituent employed on the HSPh skeleton in the Pb(II) SCPs affects the (–M–S–)n dimensionality.30 Although the effect of
substituent species on the obtained (–M–S–)n networks has been
well investigated in the aforementioned study, the correlation
between (–M–S–)n dimensionalities and semiconductive properties such as photoconductivity has remained unclear. To further
elucidate the aforementioned correlation, a systematic synthesisof S-CPs with the same composition but different (–M–S–)ndimensionalities is required.

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Paper
In the present study, we focused on the Pb(II) ion because Pb(II)S-CPs reported by our group serve as excellent semiconductive
materials that are utilized as photocatalysts.6,7 Furthermore, Pb(II)S-CPs exhibit either a holodirected coordination sphere whose Pb–
S bonds are distributed throughout the surface of an encompassing globe or a hemidirected coordination sphere whose Pb–S
bonds are directed throughout only part of an encompassing globe
depending on ligand design.31 As the holodirected coordination
sphere forms more covalent bonds than those of the hemidirected
coordination sphere, the local structure around Pb(II) centers aswell as the (–Pb–S–)n dimensionality are expected to influence thesemiconductive properties in the Pb(II) S-CPs. However, the impactof the local coordination structure and (–Pb–S–)n dimensionality
on the photoconductivity of Pb(II) S-CPs remains largely unexplored. Herein, we investigated the influence of the local structurearound Pb(II) ions and (–Pb–S–)n network structures on semiconductive properties by systematically synthesizing Pb(II) S-CPs withmethoxybenzenethiol (HSPhOMe) ligands (Fig. 1). By changing theposition of the methoxy substituent on the HSPh skeleton, we
synthesized three Pb(II) S-CPs with a formula of [Pb(x-SPhOMe)2]n(x = ortho (KGF-32), meta (KGF-33), and para (KGF-34); HSPhOMe =methoxybenzenthiol) and analyzed their photoconductivity using
time-resolved microwave conductivity (TRMC) and first-principles
calculations.

Results and discussion
Single crystal X-ray diﬀraction (SCXRD) analyses
The syntheses were performed in an autoclave using thesolvothermal method (see the Experimental section). Single

Journal of Materials Chemistry C
crystals of KGF-32, KGF-33, and KGF-34 were obtained as
pale-yellow needle crystals, light-yellow needle crystals, anddark brown plate crystals, respectively (Fig. 1 and Fig. S1, ESI†).
The crystal structures were determined using single-crystal
X-ray diﬀraction (SCXRD) at 150 K. The crystal parameters arepresented in Table S1 (ESI†), with the full structural data
available from the CCDC (CCDC 2308865–2308867†). KGF-32
crystallizes in the monoclinic P21/c space group. The asymmetric unit consists of one Pb(II) ion and two chelating
o-SPhOMe anions (Fig. S2a, ESI†). The Pb(II) center wascoordinated by two O atoms of the methoxy group and four S
atoms of the thiolate, yielding a holodirected coordinationgeometry with a distorted [PbO2S4] octahedron (Fig. 2a). The
Pb–O bond lengths are 2.703 and 2.862 Å, whereas the Pb–S
bond distance falls in the range 2.689–3.384 Å (Fig. S3a, ESI†).
The S atoms of thiolate act as a m2-S atom (Fig. S4a, ESI†), whichconnects the neighboring [PbO2S4] octahedra by edge sharing,consequently forming a 1D structure along the c-axis (Fig. 2b).
Thus, KGF-32 has a 1D structure containing a 1D (–Pb–S–)nchain with holodirected [PbO2S4] octahedra (Fig. S5a, ESI†).
Furthermore, 1D chains were arranged by weak van der Waals(vdW) interactions between the 1D chains (Fig. S6a, ESI†).
Similar to KGF-32, KGF-33 crystallized in the monoclinic
P21/c space group, and the formation of a 1D-extended structure was evident. However, in contrast to KGF-32 which features
a holodirected coordination sphere with a [PbO2S4] octahedron,
KGF-33 features a hemidirected coordination mode with a[PbS5] square pyramidal coordination geometry and five S atomsof m-SPhOMe bound to the Pb(II) ion (Fig. 2c). The Pb–S bondlengths were in the range 2.693–3.204 Å (Fig. S3b, ESI†). The S

Fig. 1 Schematic illustration of structures for [Pb(x-SPhOMe)2]n (x = ortho (KGF-32), meta (KGF-33), and para (KGF-34)). From left to right: Coordination
modes of SPhOMe ligands, local structures around Pb(II) ions, (–Pb–S–)n dimensionality, photographs of corresponding samples.

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Journal of Materials Chemistry C

Paper
According to previously reported literature,30,31 the electron
density of thiol groups has a significant impact on both thelocal structure around the Pb(II) ions and the coordination
numbers, which in turn undergo a (–Pb–S–)n dimensionalitychange. Specifically, the increased electron density of the thiolgroup contributes to the transition from the hemidirected tothe holodirected mode and increases the coordination numberof the Pb–S unit, consequently resulting in the formation of a2D (–Pb–S–)n layer. In the current study, a structural change inthe coordination sphere, depending on the position of themethoxy substituents, was evident. As anticipated, KGF-33 with
an electron-donating methoxy substituent at meta-position
featured a hemidirected [PbS5] structure, whereas KGF-32 andKGF-34 with methoxy substituents at ortho- and para-positions
exhibited holodirected structures with [PbO2S4] and [PbS6]
units, respectively. These structural variations in the coordination sphere also influence the dimensionality of the (–Pb–S–)nstructure. KGF-33 exhibited a 1D (–Pb–S–)n chain structure
attributed to its hemidirectional structure, whereas KGF-34
displayed a 2D (–Pb–S–)n layer due to its holodirectional structure. These results are consistent with the previously reported
trends. Notably, KGF-32 with a methoxy substituent at the orthoposition featured a 1D (–Pb–S–)n chain despite its holodirectedstructure. This may be attributed to the presence of O coordination atoms that disturb the 2D extension of the (–Pb–S–)n network
through m3-S atoms, thereby leading to the formation of a 1D
chain structure. The purities of the respective products wereconfirmed by powder X-ray diffraction (PXRD) and elemental
analyses before the physical measurements (Fig. S9, ESI†).

Fig. 2 Crystal structures of KGF-32, KGF-33, and KGF-34. (a) Holodirected
sphere with a [PbO2S4] octahedron; (b) 1D chain structure of KGF-32; (c)Hemidirected sphere with a [PbS5] square pyramid; (d) 1D chain structure of
KGF-33; (e) and (g) Holodirected [PbS6] octahedron; (f) and (h) 2D layer
structure of KGF-34. Color code: Pb: green, S: yellow, C: grey, O: red, H: white.

atoms exhibit two coordination modes: S1 is a m2-S atom, whereas
S2 is a m3-S atom (Fig. S4b, ESI†). The m2-S1 atom behaves as abridging atom to form a dinuclear coordination unit (Fig. S7,
ESI†). In contrast, the m3-S2 atom serves to bridge the dinuclear
units, forming a 1D chain structure along the a-axis (Fig. 2d,
Fig. S5b, ESI†). Consequently, KGF-33 features a 1D chain structure composed of a 1D (–Pb–S–)n chain in the hemidirected [PbS5]
coordination mode. The resultant 1D chains were further
assembled by weak vdW interactions (Fig. S6b, ESI†).
KGF-34 was prepared using p-HSPhOMe crystallized in the
monoclinic space group P2/n, consistent with recently reported
literature.30 It contained two crystallographically nonequivalent Pb(II) ions (Fig. S2c, ESI†), whose Pb(II) centers had
a holodirected coordination structure with a [PbS6] octahedron(Fig. 2e and g). The Pb–S bond length was 2.835–3.321 Å (Fig.
S3c, ESI†). All S atoms serve as m3-S to form a 2D layer structure
parallel to the ab-plane (Fig. S4c, ESI†). Notably, the 2D layer of
KGF-34 contains a 2D-extended (–Pb–S–)n layer comprising
holodirected [PbS6] octahedra (Fig. 2f and h, Fig. S5c, ESI†).
The resultant 2D layer was stacked by weak vdW interactions
with an interlayer distance of 17.210 Å (Fig. S6c and S8, ESI†).

1960 | J. Mater. Chem. C, 2024, 12, 1958–1964

Thermal and chemical stability
The thermal stabilities of KGF-32, KGF-33, and KGF-34 were
investigated by thermogravimetry analyses (TGA). Fig. S10(ESI†) displays TG plots in the temperature range 30–600 1C
under N2 atmosphere, wherein no weight loss was observed up
to approximately 187 1C for KGF-32, 136 1C for KGF-33, and
205 1C for KGF-34. The enhanced thermal stabilities of KGF-32
and KGF-34 may be attributed to the holodirectional structureswith a more covalent Pb–S bond. The chemical stability inwater, 1 M HCl aq., 1 M NaOH aq., and organic solvents was
also examined by obtaining the PXRD pattern for the sample,
which had been immersed in the corresponding solvent for
24 h. As depicted in Fig. S11 (ESI†), all S-CPs exhibited
remarkable stability in water. However, KGF-32 and KGF-34,
which have holodirected coordination spheres, were unstable
under acidic conditions but remained stable under basic conditions. Conversely, KGF-33, featuring a hemidirected coordination sphere, exhibited instability under both acidic and basic
conditions. The resistance to basic conditions observed in KGF32 and KGF-34 may be attributed to the holodirected coordination spheres with a more covalent Pb–S bond. The series ofPb(II)-based S-CPs also exhibited remarkable stability in organic
solvents (Fig. S12, ESI†). Accordingly, the resultant thermal andchemical stabilities may be attributed to the strong bonds
between the Pb(II) ions and the S coordination atoms.

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Semiconductive properties
The electronic and optical properties were evaluated using
diﬀuse-reflectance ultraviolet-visible-near-infrared (DR-UV-VisNIR) spectroscopy. KGF-32 and KGF-33 display broad absorption
below 500 nm, whereas KGF-34 shows visible light absorption
with an absorption edge at 765 nm (Fig. 3a). By extrapolating a
Tauc plot in the forms of [F(R)  hn]1/2 vs. hn for the indirect
semiconductors (KGF-33 and KGF-34) and [F(R)  hn]2 vs. hv forthe direct semiconductor (KGF-32) (see the following firstprinciples calculation results), the optical bandgaps of KGF-32,
KGF-33, and KGF-34 were estimated to be 2.93, 2.51, and 1.64 eV,
respectively (Fig. 3b). Photoelectron yield spectroscopy (PYS) was
employed for determining the absolute valence band maximum(VBM) level,32 in which the VBM levels were determined to be5.66, 5.63, and 5.18 eV below the vacuum level for KGF-32,
KGF-33, and KGF-34, respectively (Fig. S13, ESI†). Considering
the optical bandgap obtained from the DR-UV-Vis-NIR results,
the absolute conduction band minimum (CBM) levels of KGF-32,
KGF-33, and KGF-34 were determined to be 2.73, 3.12, and3.54 eV below the vacuum level, respectively (Fig. 3c).
The photoconductive properties of KGF-32, KGF-33, and
KGF-34 were investigated using TRMC experiments. TRMC isa contactless technique that uses high-frequency microwaves toprobe the laser-induced transient increase in conductivity,
providing information on charge transport on a multiP
nanometer length scale.33,34 The j mmax values (j = quantumP
yield of charge-carrier generation; m = sum of the hole andelectron mobilities) were determined to be 2.5  105 cm2 V1Journal of Materials Chemistry Cs1 for KGF-32, 3.8  105 cm2 V1 s1 for KGF-33, and 1.4 
103 cm2 V1 s1 for KGF-34 (Fig. 3d and Fig. S14, ESI†). TheP
j mmax value of KGF-34 is two orders of magnitude higherPthan those of KGF-32 and KGF-33. Notably, the j mmax value
obtained for KGF-34 is the highest among the previously
reported photoconductive CPs and MOFs (Table S2, ESI†). This
remarkable photoconductivity reflects the coordination
environment around the Pb(II) ion and (–Pb–S–)n dimensionality, as discussed below.
First-principles calculations
In the Pb(II) S-CPs, the local structure around the Pb(II) centers
and the (–Pb–S–)n dimensionality are expected to affect theelectronic structures because the bond of the holodirectedstructure is more covalent than that observed in the hemidirected structure. Therefore, we evaluated the band structureusing first-principles calculations to elucidate the relationshipbetween crystal structure and photoconductivity (details of thecalculation method are presented in the Experimental
section).35 The calculations demonstrated that KGF-32 is anindirect transition semiconductor, whereas KGF-33 and KGF-34
are direct transition semiconductors. The calculated bandgaps,
determined by the energy difference between the VBM and the
CBM, are 2.84 eV for KGF-32, 2.58 eV for KGF-33, and 1.18 eV
for KGF-34. These values are in good agreement with the trends
obtained from DR-UV-Vis-NIR spectroscopy. Notably, the calculated band gaps were typically lower than the experimental
values.36 In the simulated band structures, KGF-32 and KGF-33

Fig. 3 Semiconductive natures of KGF-32, KGF-33, and KGF-34. (a) DR-UV-Vis-NIR spectra; (b) Tauc plot; (c) Electronic energy diagram below vacuum
level. The VBM energy level was determined by PYS experiments, as depicted in Fig. S13 (ESI†); and (d) Results of TRMC experiments (lex = 355 nm; red:
KGF-32, blue: KGF-33, green: KGF-34).

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Fig. 4 Band structures and DOS profiles of (a) KGF-32, (b) KGF-33, and (c) KGF-34. VBM energy level is presented as zero.

each had flat bands with a dispersion width o0.3 eV in boththe VBM and CBM (Fig. 4a and b). KGF-34 also showed arelatively flat band in the VBM while exhibiting an anomalous
CBM dispersion with a dispersion width of approximately
1.6 eV (Fig. 4c). The direction of the CBM dispersion obtainedfor KGF-34 corresponded to the in-plane direction of the 2D
layer (G–Y, A–B, and D–E). Because typical semiconductive CPs
possess a flat band structure with o0.3 eV dispersion widths,
the resultant steep CBM dispersion of KGF-34 strongly
indicates that the electron mobility of KGF-34 along the 2D
layer structure is remarkable. The band dispersion trends
observed for KGF-32, KGF-33, and KGF-34 are fully consistent
with the TRMC results.
Density of states (DOS) analyses provided additional insight
into the origin of the bands from the elements, where the blackline represents the total DOS, and the other colored lines
represent the partial DOS (PDOS). In the PDOS analyses of
KGF-32 and KGF-33, the C and S atoms largely contributed to
the VBM. The CBM of KGF-32 was dominated by Pb andC atoms, with a negligible contribution from S atoms, whereas
the CBM of KGF-33 mainly consisted of Pb, with small contributions from S and C atoms. For KGF-34, the VBM mainly
consisted of C and S atoms, whereas the CBM largely consistedof Pb and S atoms. The distribution of the VBM and CBM also
supported the PDOS results (Fig. S15–S17, ESI†). In particular,
the VBM of KGF-34 was localized on the SPhOMe ligands,
whereas the CBM was delocalized through the 2D (–Pb–S–)nlayer. These results clearly reveal that the 2D (–Pb–S–)n layer,
composed of holodirected [PbS6] coordination spheres, serves
as a pathway for electron mobility.
Overall, the series of Pb(II) S-CPs exhibited photoconductivity that reflected the local structure around the Pb(II) ions and(–Pb–S–)n dimensionality. As expected, KGF-33 with methoxy
substituents at the meta-position displayed poor photoconductivity with a flat band owing to the hemidirected coordination
sphere with more ionic bonds. In contrast, KGF-34 with methoxy
substituents at the para-position exhibited high photoconductivity with a large CBM dispersion because of its holodirected
coordination environment with more covalent bonds. Although
KGF-32 with methoxy substituents at the ortho-position featured
a holodirected coordination sphere, it exhibited lower photoconductivity than KGF-33 and KGF-34. From this perspective, we

1962 | J. Mater. Chem. C, 2024, 12, 1958–1964

suggest that a 2D-arranged, holodirected [PbS6] octahedron is
crucial for constructing a pathway for electron mobility.

Conclusions
We systematically synthesized three Pb(II) S-CPs of [Pb(SPhOMe)2]nwith various coordination environments and inorganic (–Pb–S–)ndimensionalities by changing the positions of the methoxy substituents. Because of the electron-donating methoxy group at theortho- and para-positions, KGF-32 and KGF-34 featured holodirected coordination spheres, 1D (–Pb–S–)n chains with [PbO2S4]octahedra and 2D (–Pb–S–)n layers with [PbS6] octahedra, respectively. In contrast, KGF-33 with a methoxy substituent at the metaposition features a 1D (–Pb–S–)n layer comprising a hemidirected[PbS6] coordination sphere. Our systematic investigation using
TRMC measurements and first-principles calculations revealed
that a 2D-extended (–Pb–S–)n layer composed of holodirected[PbS6] octahedra is crucial for inducing high electron mobility.
These results provide new insights into design strategies forfabricating highly photoconductive Pb(II) S-CPs.

Experimental
Materials
Pb(NO3)2 (Z99.9%) and methanol (MeOH) (Z99.5%) werepurchased from FUJIFILM Wako Pure Chemical Industries,
Osaka, Japan. o-Methoxybenzenethiol (o-HSPhOMe) (Z98.0%),
m-methoxybenzenethiol (m-HSPhOMe) (Z98.0%), and p-methoxybenzenethiol (p-HSPhOMe) (Z96.0%) were obtained from Tokyo
Chemical Industry Co., Ltd., Tokyo, Japan. Acetone (Z99.0%) was
obtained from Kanto Chemical Co., Inc. (Japan). All chemicals andsolvents employed in the synthesis were of reagent grade and usedwithout further purification.
Synthetic procedures
Synthesis of KGF-32. Pb(NO3)2 (198.7 mg, 0.6 mmol) ando-HSPhOMe (168.2 mg, 1.2 mmol) were dissolved in MeOH/H2O(8.0 mL, v : v = 1 : 1) and sealed in a 16 mL Teflon-lined
stainless-steel container. The solution was heated to 60 1C
for 48 h. Then, the container was cooled to 30 1C for 12 hin the autoclave. The residue was collected by centrifugation

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Journal of Materials Chemistry C(4000 rpm, 3 min) and washed with MeOH. The resulting solid was
dried under vacuum to yield the product as pale-yellow, needle-likecrystals. Yield: 94.6 mg (66.6%). Anal. C14H14O2PbS2: calcd C 34.63,
H 2.91, N 0.00; found C 34.62, H 2.87, N 0.00.
Synthesis of KGF-33. Pb(NO3)2 (198.7 mg, 0.6 mmol) andm-HSPhOMe (168.2 mg, 1.2 mmol) were dissolved in acetone/
H2O (8.0 mL, v : v = 1 : 1) and sealed in a 16 mL Teflon-lined
stainless-steel container. The solution was heated to 80 1C for
48 h. Subsequently, the container was cooled to 30 1C for 12 hin the autoclave. The residue was collected by centrifugation(4000 rpm, 3 min) and washed with MeOH. The resulting solid
was dried under vacuum to yield the product as yellow needlelike crystals. Yield: 116.6 mg (40.0%). Anal. C14H14O2PbS2:
calcd C 34.63, H 2.91, N 0.00; found C 34.54, H 2.87, N 0.00.
Synthesis of KGF-34. Pb(NO3)2 (198.7 mg, 0.6 mmol) and
p-HSPhOMe (168.2 mg, 1.2 mmol) were dissolved in acetone/
H2O (8.0 mL, v : v = 1 : 1) and sealed in a 16 mL Teflon-lined
stainless-steel container. The solution was heated to 80 1C for
48 h. Then, the container was cooled to 30 1C for 12 h in the
autoclave. The residue was collected by centrifugation (4000rpm, 3 min) and washed with MeOH. The resulting solid was
dried under vacuum to yield the product as dark-brown crystalline sheets. Yield: 131.6 mg (45.2%). Anal. C14H14O2PbS2: calcd
C 34.63, H 2.91, N 0.00; found C 34.60, H 2.65, N 0.00.
Methods
Single crystal X-ray diﬀraction (SCXRD). SCXRD data werecollected on a Rigaku Saturn CCD diﬀractometer equipped with
Mo-Ka radiation (l = 0.71073 Å). The diﬀraction profiles were
integrated using the CrysAlisPro software. The structures wereobtained by direct methods using the SHELXT program andrefined using SHELXL.37,38 Anisotropic thermal parameters
were used to refine all non-H atoms. All the calculations were
performed using the Olex2 crystallographic software package.39
Diﬀuse-reflectance ultraviolet-visible-near-infrared (DR-UVVis-NIR) spectroscopy. DR-UV-Vis-NIR spectroscopy was performed using a SHIMADZU UV-3600 UV-Vis-NIR spectrophotometer at wavelengths ranging from 200 nm to 1000 nm. BaSO4
powder was used as the non-adsorbing background. The bandgaps were calculated using the Kubelka–Munk function and thefollowing equation:Kð1  RÞ2¼ FðRÞ ¼
S
2R
where K is the absorption coefficient, S the scattering factor, R
the reflectance, and F(R) the KM function. The bandgap wasdetermined from the Tauc plot with [F(R)  hn]1/2 vs. hn (for theindirect semiconductors) and [F(R)  hn]2 vs. hn (for the direct
semiconductor) by extrapolating the linear region to theabscissa.
Photoelectron yield spectroscopy (PYS). Crystalline samples
were placed on a conductive carbon tape on a glass substrate,
which was connected to the earth wire in a vacuum chamber(104 Pa) of a Bunko Keiki BIP-KV202GD instrument. The sample
was exposed to monochromated ultraviolet (UV) light (4–7 eVcorresponding to 355 to 177 nm), and the photoelectrons emittedThis journal is © The Royal Society of Chemistry 2024

from the sample were detected. The photon number (power) of UV
light was measured by a photodetector prior to the experiment.
Time-resolved microwave conductivity (TRMC) measurement. Crystalline samples on an adhesive tape attached to aquartz substrate were placed in the resonant cavity and exposed
to continuous microwave radiation at approximately 9.1 GHz.
The third harmonic generation (355 nm) of a Nd:YAG laser(Continuum Inc., Surelite II, pulse duration = 5–8 ns, 10 Hz)
was used as the excitation source (incident photon density I0 =9.1  1015 photons cm2 pulse1). The photoconductivity(Ds = A1DPrPr1 where A is the sensitivity factor, Pr is thereflected microwave power, and DPr is the change in Pr upon
exposure to light) was converted into the product of thequantum yield (j) and sum of the charge carrier mobilitiesPP
m (= m+ + m–) using the relationship j m = Ds(eI0Flight)1,
where e and FLight are the electron charge and correction (orfilling) factor, respectively. The experiments were performed at
25 1C in air.
First-principles calculation. First-principles calculations
were performed using CASTEP 2020 (20.1.0.5). The generalized
gradient approximation (GGA) and the Perdew–Burke–Ernzerhof (PBE) exchange correlation potential with the ultrasoft
pseudopotential plane-wave method were used. The planewave cut-off were set to 570 eV for KGF-32, 630 eV for KGF-33,
and 490 eV for KGF-34. The Brillouin zones of KGF-32, KGF-33,
and KGF-34 were sampled with a 4  2  4 k-point mesh, 3  1 
1 k-point mesh, and 13  19  3 k-point mesh, respectively.
Other physical measurements. Elemental analysis was performed using A-Rabbit-Science Japan Co., Ltd, Japan. SEM
textures were recorded using a JEOL scanning electron microscope. The acceleration voltage was set at 15 kV. Scanningelectron microscopy (SEM) images were acquired using a JEOL
JCM-6000 instrument. All samples were sputter-coated with Au
prior to analysis. Powder X-ray diﬀraction (PXRD) was performed on a Rigaku MiniFlex600 diﬀractometer at 40 kV and
15 mA using a Cu target tube. Samples were examined without
grinding, and data were collected in the 2–501 2y range using
Cu-Ka radiation (l = 1.54187 Å). Thermogravimetric analysis(TGA) was performed on a Shimadzu DTG-60 instrument. The
analysis was conducted in the temperature range of 30–600 1C,
with a heating rate of 10 1C min1, under an N2 atmosphere.

Author contributions
The manuscript was written with contributions from all authors. All
the authors approved the final version of the manuscript.

Conflicts of interest
There are no conflicts to declare.

Acknowledgements
This work was supported by JSPS Grant numbers JP22K14702,
JP20H05836, JP20H02577, JP23H01810, and JP23H04637

J. Mater. Chem. C, 2024, 12, 1958–1964 | 1963

View Article Online

Journal of Materials Chemistry C(Transformative Research Areas (A) ‘‘Supra-ceramics’’) andpartially supported by the ENEOS Hydrogen Trust Fund. R. A.
acknowledges the financial support provided by the Izumi
Science and Technology Foundation and the Kawanishi Memorial ShinMaywa Education Foundation. D. T. acknowledges thefinancial support provided by JST, Grant number JPMJPF2204,
and the Samco Foundation. We would like to thank Editage(https://www.editage.jp) for the English-language editing.

Published on 29 December 2023. Downloaded on 10/11/2024 5:49:13 PM.

Notes and references
1 O. Veselska and A. Demessence, Coord. Chem. Rev., 2018,
355, 240–270.
2 J. Xie, L. Wang and J. S. Anderson, Chem. Sci., 2020, 11,8350–8372.
3 Y. Jin, C. Zhang, X. Y. Dong, S. Q. Zang and T. C. W. Mak,
Chem. Soc. Rev., 2021, 50, 2297–2319.
4 Y. Kamakura and D. Tanaka, Chem. Lett., 2021, 50, 523–533.
5 G. E. Wang, S. Luo, T. Di, Z. Fu and G. Xu, Angew. Chem., Int.
Ed., 2022, 61, e202203151.
6 Y. Kamakura, P. Chinapang, S. Masaoka, A. Saeki, K. Ogasawara,
S. R. Nishitani, H. Yoshikawa, T. Katayama, N. Tamai,
K. Sugimoto and D. Tanaka, J. Am. Chem. Soc., 2020, 142, 27–32.
7 Y. Kamakura, S. Yasuda, N. Hosokawa, S. Nishioka, S. Hongo,
T. Yokoi, D. Tanaka and K. Maeda, ACS Catal., 2022, 12,10172–10178.
8 Y. Kamakura, C. Suppaso, I. Yamamoto, R. Mizuochi,
Y. Asai, T. Motohashi, D. Tanaka and K. Maeda, Angew.
Chem., Int. Ed., 2023, 62, e202305923.
9 Y. Li, J. Shu, Q. Huang, K. Chiranjeevulu, P. N. Kumar, G. E.
Wang, W. H. Deng, D. Tang and G. Xu, Chem. Commun.,
2019, 55, 10444–10447.
10 H. Jiang, L. Cao, Y. Li, W. Li, X. Ye, W. Deng, X. Jiang,
G. Wang and G. Xu, Chem. Commun., 2020, 56, 5366–5369.
11 Y. Wen, G. E. Wang, X. Jiang, X. Ye, W. Li and G. Xu, Angew.
Chem., Int. Ed., 2021, 60, 19710–19714.
12 A. Pathak, J. W. Shen, M. Usman, L. F. Wei, S. Mendiratta,
Y. S. Chang, B. Sainbileg, C. M. Ngue, R. S. Chen, M. Hayashi,
T. T. Luo, F. R. Chen, K. H. Chen, T. W. Tseng, L. C. Chen and
K. L. Lu, Nat. Commun., 2019, 10, 1721.
13 G. Xing, Y. Li, Z. Feng, D. J. Singh and F. Pauly, ACS Appl.
Mater. Interfaces, 2020, 12, 53841–53851.
14 C. Andrade, S. Hawila, A. Abdallah, J.-L. Rukemampunzi,
A. Mesbah, N. Guillou, F. Perret, S. Wuttke, T. Niehaus,
R. Debord, O. Boisron, S. Pailhès and A. Demessence,
J. Mater. Chem. C, 2023, 11, 14540–14544.
15 L. Sun, T. Miyakai, S. Seki and M. Dinca, J. Am. Chem. Soc.,
2013, 135, 8185–8188.

1964 | J. Mater. Chem. C, 2024, 12, 1958–1964

Paper
16 L. Sun, C. H. Hendon, M. A. Minier, A. Walsh and M. Dinca,
J. Am. Chem. Soc., 2015, 137, 6164–6167.
17 T. Wakiya, Y. Kamakura, H. Shibahara, K. Ogasawara,
A. Saeki, R. Nishikubo, A. Inokuchi, H. Yoshikawa and
D. Tanaka, Angew. Chem., Int. Ed., 2021, 60, 23217–23224.
18 C. M. Che, C. H. Li, S. S. Chui, V. A. Roy and K. H. Low,
Chem. – Eur. J., 2008, 14, 2965–2975.
19 C. Lavenn, L. Okhrimenko, N. Guillou, M. Monge, G. Ledoux,
C. Dujardin, R. Chiriac, A. Fateeva and A. Demessence, J. Mater.
Chem. C, 2015, 3, 4115–4125.
20 J. Troyano, Ó. Castillo, P. Amo-Ochoa, J. I. Martı́nez, F. Zamora
and S. Delgado, CrystEngComm, 2019, 21, 3232–3239.
21 C. Lavenn, N. Guillou, M. Monge, D. Podbevsek, G. Ledoux,
A. Fateeva and A. Demessence, Chem. Commun., 2016, 52,
9063–9066.
22 Y. Li, X. Jiang, Z. Fu, Q. Huang, G. E. Wang, W. H. Deng,
C. Wang, Z. Li, W. Yin, B. Chen and G. Xu, Nat. Commun.,
2020, 11, 261.
23 I. G. Dance, J. Am. Chem. Soc., 1980, 102, 3445–3451.
24 I. G. Dance, R. G. Garbutt, D. C. Craig and M. L. Scudder,
Inorg. Chem., 1987, 26, 4057–4064.
25 C. Xu, H.-T. Shi, Z.-F. Xin, A.-Q. Jia and Q.-F. Zhang,
J. Cluster Sci., 2014, 25, 1353–1361.
26 A. Eichhofer and G. Buth, Dalton Trans., 2016, 45, 17382–17391.
27 A. Eichhofer and S. Lebedkin, Inorg. Chem., 2018, 57,
602–608.
28 A. Eichhöfer and G. Buth, Eur. J. Inorg. Chem., 2019, 639–646.
29 L. Okhrimenko, C. Cibaka Ndaya, A. Fateeva, G. Ledoux and
A. Demessence, New J. Chem., 2020, 44, 17970–17975.
30 H. Yang, S. Mandal, Y. H. Lee, J. Y. Park, H. Zhao, C. Yuan,
L. Huang, M. Chen and L. Dou, J. Am. Chem. Soc., 2023, 145,
23963–23971.
31 L. Shimoni-Livny, J. P. Glusker and C. W. Bock, Inorg. Chem.,
1998, 37, 1853–1867.
32 R. Nishikubo, N. Ishida, Y. Katsuki, A. Wakamiya and
A. Saeki, J. Phys. Chem. C, 2017, 121, 19650–19656.
33 A. Saeki, Y. Koizumi, T. Aida and S. Seki, Acc. Chem. Res.,
2012, 45, 1193–1202.
34 A. Saeki, Polym. J., 2020, 52, 1307–1321.
35 S. J. Clark, M. D. Segall, C. J. Pickard, P. J. Hasnip,
M. I. J. Probert, K. Refson and M. C. Payne, Z. Kristallogr. Cryst. Mater., 2005, 220, 567–570.
36 C. Lee, W. Yang and R. G. Parr, Phys. Rev. B: Condens. Matter
Mater. Phys., 1988, 37, 785–789.
37 G. M. Sheldrick, Acta Crystallogr., 2008, A64, 112–122.
38 G. M. Sheldrick, Acta Crystallogr., 2015, C71, 3–8.
39 O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howardand H. Puschmann, J. Appl. Crystallogr., 2009, 42, 339–341.

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