Preparation and Characterization of [C6H 5 CH2 NH3 ]2 PbI4,
[C6 H 5 CH 2 CH 2 SC(NH2 )2 ]3 PbI5 and [C10 H 7 CH 2 NH3 ]PbI3
Organic-Inorganic Hybrid Compounds
G. C. Papavassilioua, G. A. Mousdisa, C. P. Raptopouloub, and A. Terzisb
a Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation,
48, Vassileos Constantinou Ave., Athens 116/35, Greece
b Institute of Materials Science, NCSR, Demokritos, Athens 153/10, Greece
Reprint requests to Prof. G. C. Papavassiliou. Fax: (301) 7273794
Z. Naturforsch. 54 b, 1405-1409 (1999); received July 7, 1999
Organic-Inorganic Hybrides, Perovskites, Low-Dimensional Compounds, Excitonic Spectra
The preparation, crystal structures, optical absorption spectra, and photoluminescence spectra
of the title compounds are reported. The compounds were prepared in single crystal form.
[CftHsCHiNH.^PbL consists of anionic perovskite sheets of corner-sharing Pbl6 octahedra,
which alternate with the C ö H s C ^ N H ^ sheets. [ C ftH s C ^ C ^ S Q N H i^ b P b ls consists of
zig-zag chains of anionic corner sharing Pbl6 octahedra separated by C 6H 5CH 2CH 2SC(NH 2)2
cations. [CioH7CH 2N H 3]Pbl3 consists of twin chains of edge-sharing P b^ octahedra separated
by C 10 H 7 CH 2 NH 3 cations. The compounds are thus low-dimensional systems. The excitonic
spectra were observed in all cases, even at room temperature, and the possibility of organicinorganic excitonic interactions is discussed.
Introduction
During the last years a number of organicinorganic hybrid low-dimensional (LD ) semicon­
ductors based on metal-halide units have been pre­
pared and studied [1 - 16] (for reviews see [1 , 10 ,
11]). Some of them could be candidates for the
construction of optoelectronic devices [12 - 14]. In
these systems either one of the components (or­
ganic or inorganic) is active, or both of them are
active. For example, compounds of the types [C6H 5(C H 2),!NH^]2M X 4 [1 - 3, 5 - 7, 10 - 15], [C,0H 7(CH 2)„NH^]2M X 4 [8, 16], and [Ci4H 9(C H 2)„N H 3]2M X 4 [8] (M = Pb, Sn; C 6H 5 = phenyl-,
C 10H 7 = naphthyl-, C 14H 9 = anthranyl-groups; n =
1, 2, 3. . . . ) are two-dimensional (2D) semiconduc­
tors. They exhibit pronounced linear and nonlin­
ear optical properties, in comparison to those of
the corresponding three-dimensional systems. Re­
cently, Era et al. [16] studied the optical and related
properties of [C1oH7(C H 2)nN H 3]2PbBr4 and sim­
ilar 2D perovskite-like structures based on PbBrnetworks, where both the organic (C 10H 7) and in­
organic (PbBr4) components are (optically) active.
They found a strongly enhanced phosphorescence
arising from the organic part (:CioH7) of the sys­
tems. This phosphorescence has been attributed
0932-0776/99/1100-1405 $ 06.00
©
to the (electronic) interaction between the organic
and inorganic components of the (2D ) systems.
The phosphorescence was found to increase on de­
creasing the alkyl-linking group (C H 2)„ (i.e., for
smaller n). On the other hand, for organic-inorganic
hybrid systems it was predicted theoretically that the
interaction is a consequence of the fact that the inor­
ganic (Wannier-type) excitons have Bohr radii much
larger than organic (Frenkel-type) excitons [17]. If
the conditions reported in [17] are fulfilled, we ex­
pect that for Pb/I-based ID compounds the inter­
action will be as strong as that of Pb/Br-based 2D
systems (with the same organic component), be­
cause the exciton Bohr radius in these two systems
is almost the same (12 and 8 A, respectively) (see
[1, 6 , 10 ]).
In this paper the preparation and characterization
of some L D compounds based on Pb/I-networks
with relatively small alkyl linking groups are de­
scribed.
Experimental
Starting materials and apparatus
The following starting materials were used without
further purification. PbL (Johnson Matthey, 976204),
PbO (Ferak 01-881), hydroiodic acid 57% (Merck
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G. C. Papavassiliou et al. • Organic-Inorganic Hybrid Compounds
1406
Table I. Summary of crystal, intensity collection and re­
finement data
Compound
1
2
3
Fw
a (A)
b (A)
c (A)
V (A 3)
ß (deg)
Z
D (cald/ M gm -3)
Space group
GOF
Ri
WR2
931.12
8.689(5)
28.78(1)
9.162(4)
2291(2)
1385.51
16.130(6)
27.75(1)
9.334(4)
4079(1)
102.44(1)
4
2.256
P2,/c
1058
0.0779
0.1409b
746.11
15.16(1)
4.749(3)
11.676(9)
808.6(1)
105.93(2)
4
2.699
Pbca
1.101
0.0573
0 .1030a
2
3.065
P2.
1.088
0.0414
0.1152°
aFor 1536 reflections with I > 2a(I); bfor 4504 reflections
with I > 2<t(I); cfor 2683 reflections with 1 > 2<x(I).
341), H 3PO 2 50% (Fluka 9421), (2-iodoethyl)benzene
(Aldrich 38,049-0), benzylamine (Fluka 13180), 1-naphthylmethylamine (Fluka 71020) and thiourea (Ferak
01-525).
Crystal X-ray intensity data were collected on a
Crystal Logic [18] dual goniometer using graphitemonochromated MoKa radiation. Unit cell dimensions
were determined and refined by using the angular set­
ting of 24 automatically centered reflections in the range
11° < 29 < 24°. Intensity data were recorded using a
9-29 scan: for (C öH ^C H zN H ^P bL, 9 range 0 - 2 5 ° ,
scan speed 2° min-1, scan range 2.3 plus a\a2 separa­
tion, data collected / unique / used 2017 / 2017 / 2017,
for [C6H 5CH 2CH 2SC(NH 2)2]3Pbl5, 9 range 0-25°, scan
speed 2° min“ 1, scan range 2.3 plus a\a2 separation,
data collected / unique / used 6713 / 6255 (R\„t - 0.0350)
/ 6255; for [Q oH yO ^N H jliP bF,, 9 range 0 - 25°, scan
speed 4° min- 1, scan range 2.4 plus a 1a 2 separation, data
collected/unique/used 2989/2839 (Rm{ = 0.0321 )/2839.
Three standard reflections monitored every 97 re­
flections showed less than 3% variation and no sys­
tematic decay. Lorentz polarization and psi-scan ab­
sorption correction were applied using Crystal Logic
Software. The structures were solved by Patterson
methods using SHELXS -86 [19] and refined by fullmatrix least-squares technique with SHELXL-93 [20],
Hydrogen atoms were introduced at calculated posi­
tions as riding carbon atoms (except those of NH 2
groups in [ C ö H s C ^ C ^ S Q N ^ h b P b ls , which were
not included. All non-hydrogen atoms were refined
anisotropically. Crystallographic information files have
been deposited in the Cambridge Crystallographic Data
Center, 12 Union Road. Cambridge CB2 IEZ, UK
(e-mail: [email protected]). Deposition num­
bers 134705. 134706, and 134707 for [C6H?CH 2NH 3]2-
Fig. 1. Crystal structure of CftHsC^NHs^PbLj.
Fig. 2 . Crystal structure of [C6H 5C H .C H ,S C (N H ,) 2]3Pbl5.
Pbl4, [C6H 5CH 2CH 2SC(NH 2)2]3Pbl5 and [C„)H7CH 2NHiJPbl}, respectively.
Optical absorption (OA) spectra of thin deposits on
quartz plates were recorded on a Varian model 2390 spec­
trophotometer and the photoluminescence (PL) as well as
Raman spectra on a Jobin-Yvon model HG2S Raman
spectrophotometer using Argon Laser (:454.5 nm exci­
tation line). All measurements were performed at room
temperature.
Preparation of compounds
The precursors CftHsCHTNH^I and CioH 7CH 2N H 3l
were prepared by treating the corresponding amine with
aq.HI 57% in the presence of HiPO;? and recrystallization
of the precipitate from acetonitrile. The precursor CfcHsCH 2CH 2SC(NH2)2I was prepared by refluxing a solution
of thiourea (0.4 g, 5 mmol) and C 6H 5CH 2CH 2I (1.2 g,
G. C. Papavassiliou et al. ■Organic-Inorganic Hybrid Compounds
Fig. 3. Crystal structure of [CioH7CH 2NH 3]Pbl3.
5 mmol) in C H 3 C N for 2.5 h. The solution was concen­
trated to ca. 2 ml, 5 ml of ether was added and the mixture
cooled to 0 °C. The precipitate was filtered, washed with
ether and dried in air; yield 90% , m. p. 82 °C.
Small crystals of [ C ftH sC ^ N H ^ P b L were obtained
by treating C 6H 5CH 2NH 3I and PbF in molar ratio 2:1 in
CH 3CN or DMF. Large crystals were obtained as follows:
C 6H 5CH 2NH 2 (107 mg, 1 mmol) and PbO (111.5 mg,
0.5 mmol) were dissolved in aq. HI (57%) in the presence
of H 3PO 2 at reflux temperature. The solution was cooled
slowly and the crystals obtained after several hours were
filtered and dried in air; yield 70%, orange plates.
Analysis for C u H ^o ^L P b
Calcd C 18.06 H2.16 N3.01%,
Found C 17.93 H 1.98 N 3.13%.
Crystals of [C ftH sC ^C ^ S Q N H sh h P b h ; were ob­
tained as follows: C 6H 5CH 2CH 2SC(NH 2)2l (462 mg,
1.5 mmol) and PbO (111.5 mg, 0.5 mmol) were dissolved
in aq. HI (57%, 5 ml) in the presence of H 3 P O 2 at reflux
temperature. The solution was cooled slowly and the crys­
tals obtained after several hours were filtered and dried in
air; yield 78%, orange-yellow needles.
Analysis for C 27H 3yN6l 5S3Pb
Calcd C 23.40 H 2.84 N 6.07%,
Found C 23.70 H 2.86 N 5.89%.
Small crystals of [CioH7CH 2NH 3]Pbl3 were obtained
by treating C 10 H 7 C H 2 N H 3 I and P b F in molar ratios 1:1
in DM SO and precipitation with C 2 H 5 O H . Large crys­
tals were obtained as follows: CioH 7CH 2NH 2 (158 mg,
1 mmol) and P bO (223 mg, 1 mmol) were disolved in
15 ml of aq. H I (57%) in the presence of H 3 P O 2 at re­
flux temperatures. The solution was cooled slowly and
the crystals obtained after several hours were filtered and
dried in air; yield 93%, bright yellow needles.
Analysis for C n H ^N L P b
Calcd C 17.71 H 1.62 N 1.87%,
Found C 17.72 H 1.81 N 1.69%.
1407
X [nm]
Fig. 4. Optical absorption (a, b) and photoluminescence
(a', a") spectra of thin deposits of [CftH.^C^NH^hPbU
(a) and C 6H 5CH 2NH 3I (b), and of single crystals of
[C6H 5CH 2NH 3]2Pbl4 before (a1) and after (a") aging.
Results and Discussion
Morphology o f materials
The compounds were prepared in pure form of
single crystals. Plate- or needle-shaped crystals
were large enough for X-ray crystal structure deter­
mination and investigation of some physical prop­
erties (Raman and photoluminescence spectra).
Crystal structures
A summary of the crystal data of the com­
pounds [QH.CH^NFhbPbU ( 1), [QHsCH.CFbSC(NH 2 )2 ]3 PbI5 (2) and [C,oH7 CH 2 NH 3 ],Pbl3 (3)
are given in Table I.
The packing diagram of [CöH^CFLNH^kPbLt (1)
is shown in Fig. 1. It consists of 2D anionic inorganic
networks of comer-sharing Pblft octahedra, which
alternate with layers of the organic cations. The 2-D
inorganic network is similar to that of [C6H 5 CH 2 CH 2 NH 3 ]2 M I 4 (M = Pb, Sn) [3].
The packing diagram of [C6H 5CH 2 CH 2 SC(NH 2 )2 ]3 Pbl5 (2) is shown in Fig. 2. It consists of
anionic zig-zag chains of comer-sharing Pblö octa­
hedra, which are formed via cis iodine bridges. Or­
ganic cations fill the space between the chains which
results in the ID character of this compound. It is
similar to the structures of [H3N(CH?)6NH 3 ]MX 5
(M = Bi, X = Cl, I; M = Sb, X = Br, I) [4].
The structure of [C iofyC F bN ^JP b^ (3) is
shown in Fig. 3 . It consists of anionic twin chains of
edge-sharing Pblö octahedra which are surrounded
by organic cations. It can be viewed as columns of
G. C. Papavassiliou et al. ■Organic-Inorganic Hybrid Compounds
1408
X [nm]
Fig. 5. Optical absorption (a, b) and photolumines­
cence (a') spectra of thin deposits of [C6HsCH?CH->SC(NH 2)2b P b I 5 (a) and CftH^CH^CTTSQNH.M (b), and
of a single crystal of [C6H 5C H 2CH 2SC(NH 2)2]3Pbl5 (a').
inorganic twin chains down the b axis, surrounded
by parallel columns of organic cations, and this
gives it the ID character.
Optical and related properties
Fig. 4 shows the optical absorption (OA) spec­
tra of a thin deposit of [C^HsCI-LNI-^kPbL* and
of a thin deposit of the precursor C 6 H 5 CH 2 NH 3 I,
for comparison. Also, Fig. 4 shows the photolumi­
nescence (PL) spectrum of a freshly cleaved single
crystal of [C^HsCF^NF^^PbL* and the spectrum
of a single crystal after exposure to light and air
for several months. Similar spectra were obtained
from thin deposits. The OA spectrum exhibits an
excitonic peak at 516 nm, due to the PbL* network
(layer), which occurs far off the OA band {ca. 2 eV)
of the organic component (i. e., the precursor). The
PL spectra exhibit excitonic peaks at ca. 531 nm,
and in the case of an aged sample, a shoulder at ca.
561 nm, due to bound excitons, and a broad band
at ca. 720 nm. In this case, there is no indication of
exciton interactions of organic and inorganic com­
ponents; the C 6H 5 CH 2 NH 3 cations behave here as
a barrier [1 , 1 1 , 1 2 ],
Fig. 5 shows the OA spectra of a thin deposit
of [CfiF^CFbCFbSQNFhbhPbls and of a thin de­
posit of the precursor CöHsCI-hC^SCXNI-^bl, for
comparison. Also, Fig. 5 shows the PL spectrum of
200
300
400
500
X [nm]
600
Fig. 6 . Optical absorption (a, b) and photoluminescence
(a1) spectra of thin deposits of [CioHyCHjNH^Pbl.}
(a) and C 10 H 7 C H 2 N H 3 I (b), and of a single crystal of
[CioH7CH 2N H 3]Pbl3 (a’). The insert shows the Raman
spectrum of [C]oH 7 C H 2 N H 3 ]P bl 3 single crystal. Z is the
needle-axis (/?-axis).
a single crystal of [CöHsCFbCFLSCXNFbbhPbls.
The OA spectrum exhibits an excitonic peak at
412 nm, due to the PM 5 network (chain), which
occurs close to the OA band of the organic com­
ponent (i.e., the precursor). Perhaps, the PL band
at ca. 492 nm is a phosphorescence band resulting
from organic-inorganic interaction.
Fig. 6 shows the OA spectra of a thin deposit of
[C ioFbC FbN tyPb^ and of a thin deposit of the
precursor C 10H 7 CH 2 NH 3 I. Also, Fig. 6 shows the
PL and Raman spectra of a single crystal of [ C i o H 7 C F b N iy P b ^ . The OA spectrum exhibits an exci­
tonic peak at 401 nm, due to the PM 3 network (twin
chain), which occurs close to the OA band of the or­
ganic component (i.e., the precursor). The PL band
consists of peaks at 495, 531, and 572 nm, of which
the separation is 1370 - 1375 cm-1. This corre­
sponds to the A„ vibrational mode of the napthalene
entity. This is in accordance with the Raman shift
of 1374 cm - 1 shown in the insert of Fig. 6 . The
observation of this PL-band at room temperature,
which may be a phosphorescence band, could be at­
tributed to the interaction of organic and inorganic
components [16, 17], as in the case of PbBr4 -based
(2D) materials (at 13 K) [16]. Details on such mea­
surements, especially at low temperatures, and the
investigation of organic-inorganic interactions will
be reported elsewhere.
G. C. Papavassiliou et al. ■Organic-Inorganic Hybrid Compounds
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