Mesolamellar thiogermanates [CnH2n + 1NH 3]4Ge4S10

Article abstract of DOI:10.1016/j.ica.2004.08.002

The mesostructured lamellar phases with the general formula [C _nH_{2n + 1}NH₃]₄Ge₄S ₁₀ (n = 12, 14, 16, 18) were synthesized by metathesis of alkyl ammonium chloride surfactants and Na₄Ge₄S₁₀ in aqueous medium. The crystal structures of the phases with n = 12 and 14 were determined by single-crystal X-ray diffraction; [C₁₂H ₁₃NH₃]₄Ge₄S₁₀ crystallizes in monoclinic C2/c space group (a = 16.149(3), b = 46.576(9) c = 9.147(2) ?, β = 97.13(3)° and Z = 4) and [C₁₄H ₂₉NH₃]₄Ge₄S₁₀ in the triclinic P1? space group (a = 9.1280(6), b = 16.1992(1), c = 26.971(2) ?, α =73.370(1)°, β = 88.307(1)°, γ = 82.825(1)° and Z = 2). These compounds possess layers of adamantane [Ge ₄S₁₀]^4- anions separated by layers of deeply interpenetrated long chain alkylammonium molecules. Strong hydrogen bonding is observed between the terminal sulfur atoms of the [Ge₄S ₁₀]^4- clusters and H atoms of the NH₃ groups of the surfactant molecules. Spectroscopic and thermal characterization of these compounds is reported.

Full text of DOI:10.1016/j.ica.2004.08.002

Inorganica Chimica Acta 357 (2004) 4036–4044
www.elsevier.com/locate/ica
Mesolamellar thiogermanates [CnH2n + 1NH3]4Ge4S10
*
Krishnaswamy K. Rangan, Mercouri G. Kanatzidis
Department of Chemistry, Center for Fundamental Materials Research, Michigan State University, East Lansing, MI 48824, USA
Available online 18 September 2004
Dedicated to Professor Tobin J. Marks on the occasion of his 60th birthday
Abstract
The mesostructured lamellar phases with the general formula [CnH2n + 1NH3]4Ge4S10 (n = 12, 14, 16, 18) were synthesized by
metathesis of alkyl ammonium chloride surfactants and Na4Ge4S10 in aqueous medium. The crystal structures of the phases with
n = 12 and 14 were determined by single-crystal X-ray diffraction; [C12H13NH3]4Ge4S10 crystallizes in monoclinic C2/c space group
˚
ꢀ
(a = 16.149(3), b = 46.576(9) c = 9.147(2) A, b = 97.13(3)ꢀ and Z = 4) and [C14H29NH3]4Ge4S10 in the triclinic P1 space group
˚
(a = 9.1280(6), b = 16.1992(1), c = 26.971(2) A, a =73.370(1)ꢀ, b = 88.307(1)ꢀ, c = 82.825(1)ꢀ and Z = 2). These compounds possess
layers of adamantane [Ge4S10]4ꢀ anions separated by layers of deeply interpenetrated long chain alkylammonium molecules. Strong
hydrogen bonding is observed between the terminal sulfur atoms of the [Ge4S10]4ꢀ clusters and H atoms of the NH3 groups of the
surfactant molecules. Spectroscopic and thermal characterization of these compounds is reported.
ꢁ 2004 Elsevier B.V. All rights reserved.
1. Introduction
synthetic methodologies for chalcogenide-based meso-
structured materials have been described [4,5]. The
materials are based on the adamantane [Ge4S10]4ꢀ and
other anionic clusters which proved to be an excellent
precursors for ordered mesostructured chalcogenides [6].
Despite the long range order of the pores in meso-
structured phases very little is known about the struc-
ture of the inorganic frameworks or the arrangement
of the templating surfactant molecules in the pores. Ef-
forts are being made to understand pore wall structures
in these materials using electron diffraction, pair distri-
bution function analysis techniques, and theoretical
structural modeling [4,7]. Increased understanding of
supramolecular arrangements in these materials would
help the design of new phases with valuable properties.
In addition, if we can elucidate the interaction of surfac-
tants with the chalcogenide framework, better pathways
for their removal could be developed.
Materials with designed porous structure are impor-
tant because of potential applications as adsorbents,
shape selective catalysts and molecular sieves [1,2].
Among the porous solids, MCM-n, SBA-n, MSU-n
and related types of mesoporous silicates have emerged
as a frontier field of materials chemistry and a vast
amount of work has been devoted to the study of their
synthesis, properties, and technological applications
[3]. The general synthetic method for mesostructured sil-
icates involves assembling of inorganic molecular species
in the presence of long-chain organic liquid-crystal tem-
plates. Mesoporous non-oxidic materials such as sulfo-
and seleno-based systems are also of interest because
special properties can be envisaged from the combina-
tion of mesoporocity with the opto-electronic properties
of semiconducting frameworks. Recently, successful
Insights about the interaction of surfactants with the
framework could be gleaned from single crystal structure
studies of model systems such as mesostructured phases
resulting from the crystallization of [Ge4Q10]4ꢀ (Q=S,
*
Corresponding author. Tel.: +1 517 355 9715; fax: +1 517 353
1793.
E-mail address: kanatzid@cem.msu.edu (M.G. Kanatzidis).
0020-1693/$ - see front matter ꢁ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.08.002

K.K. Rangan, M.G. Kanatzidis / Inorganica Chimica Acta 357 (2004) 4036–4044
4037
Se) clusters and templating surfactants. These com-
2. Experimental
pounds tend to be layered and stabilized with the same
electrostatic interactions present in the polymeric com-
pounds of the type S+I2ꢀ [8]. In this context, we have stud-
ied the [CnH2n + 1N(CH3)3]4Ge4S10 phases (Cn-GeS, n =
12, 14, 16, 18) which contain parallel planes of uncon-
nected [Ge4S10]4ꢀ clusters, separated at mesoscopic scale
lengths by organic bilayers of cationic surfactant chains.
The interlayer separation could be tuned by changing
the alkyl chain length of the surfactants as exhibited
in the series [CnH2n + 1N(CH3)3]4Ge4Se10 (n = 8, 9,10,12,
14,16,18). We were interested in investigating salts of
the [Ge4S10]4ꢀ clusters with surfactant molecules con-
taining N–H groups as these can engage in hydrogen
bonding with the sulfide anions and change the nature
2.1. Reagents
Chemicals were used as obtained without further
purification: Ge powder 99.999% purity, ꢁ100 mesh,
Alfa Aesar; S powder, sublimed, J.T. Baker Chemical
Co.; sodium metal, 98%, Spectrum Chemical; dodecyl-
amine, 99%, Aldrich; tetradecylamine, 99%, Aldrich;
hexadecylamine, 99%, Aldrich; octadecylamine, 98%
Aldrich; ethanol, ACS anhydrous, EM Science, Inc.;
diethyl ether, ACS anhydrous, EM Science, Inc.
2.2. Synthesis
`
of the interactions vis-a-vis the alkylated [CnH2n + 1N-
(CH3)3]+ cations mentioned above. Accordingly, we ex-
plored salts with the simpler n-alkyl ammonium cations
([CnH2n + 1NH3]+, n = 12, 14, 16, 18). We obtained
crystals of the lamellar mesophases [CnH2n + 1NH3]4-
Ge4S10 (n = 12, 14, 16 and 18) (hereafter designated as
CnNH3GeS) and report here their crystal structure,
spectroscopic and physicochemical properties. The
interactions of the n-alkyl ammonium cations with the
crystal [Ge4S10]4ꢀ clusters are substantially different
from those of the [CnH2n + 1N(CH3)3]+ cations [8], and
this has a profound influence on the absorption proper-
ties of these compounds toward alcohols.
Na2S was prepared by reacting stoichiometric
amounts of the elements in liquid ammonia as described
elsewhere [9]. Na4Ge4S10 was prepared by heating stoi-
chiometric amounts of thoroughly mixed Na2S, Ge
and S (1:2:4) in evacuated quartz tubes at 850 ꢀC for
48 h [10]. This procedure gave a very hygroscopic, crys-
talline pale-yellow translucent phase, which was stored
in nitrogen filled glove box. Alkyl ammonium chlorides
R-NH3Cl (R = C12H25, C14H29, C16H33, C18H37) were
prepared by passing gaseous hydrochloric acid into a
solution of alkyl amine in acetone. The white solids
formed were filtered, and dried under vacuum.
Table 1
Crystal data and structure refinement for [C12H25NH3]4Ge4S10 and [C14H29NH3]4Ge4S10
[C12H25NH3]4Ge4S10
[C14H29NH3]4Ge4S10
Empirical formula
Formula weight
Temperature (K)
Crystal system
C48H112N4Ge4S10
1356.54
293
C56H128N4Ge4S10
1468.76
293
monoclinic
C2/c
triclinic
ꢀ
Space group
Unit cell dimensions
P1
˚
a (A)
16.149(3)
46.576(9)
9.1280(6)
16.1992(1)
˚
b (A)
˚
c (A)
9.147(2)
90
26.971(2)
73.370(1)
a (ꢀ)
b (ꢀ)
c (ꢀ)
97.13(3)
90
6827.0(2)
88.307(1)
82.825(1)
3791.3(4)
3
˚
V (A )
Z
4
0.71073
2.08
2
0.71073
1.880
˚
k (A)
Absorption coefficient (mmꢀ1
Crystal size (mm)
Crystal shape
)
0.30 · 0.19 · 0.04
long plate
0.52 · 0.13 · 0. 07
long plate
Color
colorless
4.03–30.60ꢀ
colorless
3.86–31.13ꢀ
h range for data collection
Limiting indices
Reflections collected/unique
ꢀ22 6 h 6 22, ꢀ64 6 k 6 64, ꢀ13 6 l 6 13
ꢀ13 6 h 6 13, ꢀ23 6 k 6 23, ꢀ37 6 l 639
39738/10080 [Rint = 0.2363]
2543
45478/21800 [Rint = 0.0434]
11956
0.913
Number of reflections F0 > 4r(F0)
Goodness-of-fit on F2
0.715
R1 = 0.0512
wR2 = 0.0886
Final R indices [I>2r(I)]
R1 = 0.0453
wR2 = 0.1111
1.48/ꢀ0.63
ꢀ3
˚
Largest diff. peak/hole (e A
)
0.51/ꢀ0.47
P
P
P
P
2
2
1=2
R1 ¼ ðjF obsj ꢀ jF calcjÞ= ðF obsÞ; wR2 ¼ f½wðF 2obs ꢀ F 2calcÞ = ½wðF o2bsÞ ꢂg ; w ¼ 1=½r2F o2bs þ 151:11Pꢂ; P ¼ ðF 2obs þ 2F c2alcÞ=3:

4038
K.K. Rangan, M.G. Kanatzidis / Inorganica Chimica Acta 357 (2004) 4036–4044
Table 2
Atomic coordinates (·104) and equivalent isotropic displacement
parameters (A · 10 ) for C14NH3GeS
Alkyl ammonium chlorides were dissolved by stirring
in ethanol: water (1:5) mixture at 50 ꢀC (typically 2 g in
50 mL). An amount of 0.35 g Na4Ge4S10 was dissolved
in water and filtered to remove insoluble impurities. The
clear filtrate was added to the solution of RNH3Cl and
formed immediately a white precipitate. The mixture
was stirred for 2 h at 60 ꢀC and cooled. The precipitate
was then filtered, washed with ethanol: water mixture,
and finally with ether and dried under vacuum at room
temperature overnight. Typical yield was 90% based on
Na4Ge4S10. Single crystals of C12NH3GeS and
C14NH3GeS were obtained by dissolving 0.5 g of the
products in 5 ml of ethanol:water (5:1) mixture by heat-
ing at 60 ꢀC. On cooling slowly to room temperature
colorless, long plate-like crystals were formed. Semi-
quantitative microprobe EDS analysis performed on
all phases showed that chloride or sodium were not pre-
sent. The Ge:S elemental ratio was 1:2.5 in all phases.
The elemental analyses were in good agreement with
the general composition [CnH2n + 1NH3]4Ge4S10
(n = 12, 14, 16, 18) as determined by the structure
2
3
˚
x
y
Z
U(eq)
Ge(1)
Ge(2)
Ge(3)
Ge(4)
S(1)
8952(1)
6139(1)
6122(1)
8914(1)
7577(1)
7515(1)
4669(1)
7508(1)
10395(1)
4768(1)
10353(1)
4767(1)
7519(1)
10265(1)
11061(5)
11760(4)
11624(6)
11949(5)
11819(6)
11979(6)
11841(6)
11953(6)
11819(6)
11891(6)
11767(6)
11820(6)
11686(7)
11744(4)
5728(4)
6315(6)
5594(6)
5947(7)
5559(8)
5818(7)
5512(8)
5758(8)
5454(8)
5721(8)
5441(8)
5694(8)
5427(6)
5693(6)
596(4)
8319(1)
6938(1)
8052(1)
6251(1)
7866(1)
5785(1)
7617(1)
9005(1)
7171(1)
6508(1)
9211(1)
8714(1)
6914(1)
5156(1)
7119(2)
6854(2)
7561(3)
7350(3)
8049(3)
7877(3)
8570(3)
8418(3)
9103(3)
8966(3)
9662(3)
9554(3)
10262(4)
10205(3)
4540(3)
4010(5)
4415(5)
4983(5)
4991(5)
5603(4)
5582(5)
6168(4)
6157(4)
6725(4)
6699(4)
7256(4)
7251(4)
7713(4)
8391(3)
8257(3)
7797(4)
7585(4)
7275(4)
7000(4)
6742(4)
6438(3)
6208(3)
5882(3)
5667(3)
5337(4)
5129(4)
4776(4)
9256(2)
9804(2)
9716(3)
10169(3)
10219(3)
10651(3)
9671(1)
9652(1)
10649(1)
10662(1)
9152(1)
10154(1)
10136(1)
10146(1)
10167(1)
9181(1)
9236(1)
11102(1)
11161(1)
11125(1)
8602(1)
8159(1)
7662(2)
7175(2)
6687(2)
6184(2)
5702(2)
5196(2)
4717(2)
4210(2)
3739(2)
3224(2)
2760(2)
2232(2)
8757(2)
8471(2)
7921(2)
7471(2)
6962(2)
6495(2)
5989(2)
5508(2)
5006(2)
4526(2)
4031(2)
3550(2)
3063(2)
2537(2)
11147(1)
11650(1)
12105(2)
12598(2)
13080(2)
13580(2)
14072(2)
14559(2)
15051(2)
15542(2)
16039(2)
16524(2)
17014(2)
17500(2)
8627(2)
8190(1)
7675(2)
7217(2)
6701(2)
6224(2)
35(1)
36(1)
36(1)
36(1)
41(1)
44(1)
40(1)
43(1)
38(1)
61(1)
62(1)
50(1)
40(1)
48(1)
60(1)
56(1)
81(1)
73(1)
88(2)
86(1)
90(2)
87(2)
90(2)
85(1)
95(2)
84(1)
119(2)
111(2)
137(3)
183(4)
228(6)
127(2)
129(2)
109(2)
125(2)
122(2)
120(2)
123(2)
118(2)
133(3)
145(3)
173(4)
95(2)
113(2)
99(2)
101(2)
97(2)
89(2)
95(2)
86(1)
94(2)
84(1)
94(2)
90(2)
106(2)
125(2)
62(1)
57(1)
76(1)
76(1)
82(1)
86(1)
S(2)
S(3)
S(4)
S(5)
S(6)
S(7)
S(8)
S(9)
S(10)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
1
analysis.
C(9)
2.3. Physical measurements
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(46)
C(47)
C(48)
2.3.1. Infrared and Raman spectroscopy
Infrared spectra, in the IR region (6000–400 cmꢀ1) or
far-IR region (600–100 cmꢀ1), were recorded with a
computer controlled Nicolet 750 Magna-IR Series II
spectrometer equipped with a TGS/PE detector and a
silicon beam splitter in 4 cmꢀ1 resolution. The samples
were ground with dry CsI and pressed into translucent
pellets. Raman spectra of the powdered samples were re-
corded on a Holoprobe Raman spectrograph equipped
with a 633 nm Helium–Neon laser and a CCD camera
detector. The instrument was coupled to an Olympus
BX60 microscope. The spot size of the laser beam was
10 mm when a 50x objective lens was used.
2.3.2. Solid state UV–Vis–near-IR spectroscopy
UV–Vis–near-IR diffuse reflectance spectra were ob-
tained at room temperature on a Shimadzu UV-
3101PC spectrophotometer in the wavelength range of
200 – 2500 nm.
1116(4)
275(6)
970(6)
154(6)
928(6)
138(6)
949(6)
186(6)
990(6)
2.3.3. Thermogravimetric analyses (TGA)
TGA data were obtained with a computer-controlled
Shimadzu TGA-50 thermal analyzer. Typically 20 mg of
sample was placed in a quartz bucket and heated in a
228(6)
1046(6)
293(7)
1120(8)
14256(5)
13254(4)
13812(5)
12883(5)
13607(6)
12726(6)
1
C, H, N analyses were performed with Perkin–Elmer Series II
CHNS/O analyser 2400. The observed CHN content for C12NH3GeS,
C 42.66%, H, 8.74%, N, 4.09%; C14NH3GeS 46.30%, H, 9.33%, N,
3.81%; C16NH3GeS C 54.50%, H, 10.90%, N, 3.99% and C18NH3GeS,
C 70.50%, H, 12.09%, N, 3.79%.

K.K. Rangan, M.G. Kanatzidis / Inorganica Chimica Acta 357 (2004) 4036–4044
4039
Table 2 (continued)
Table 4
Bond distances between the atoms in [Ge4S10
4ꢀ
cluster
]
x
y
Z
U(eq)
Bond
Bond length
C(49)
C(50)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
N(1)
13518(6)
10747(3)
11182(3)
11297(3)
11733(3)
11858(3)
12270(3)
12401(4)
12785(4)
6435(2)
5721(2)
5238(2)
4738(2)
4247(2)
3758(2)
3263(2)
2777(2)
2275(2)
9096(1)
9259(1)
10717(1)
9124(1)
86(1)
86(1)
87(1)
88(2)
90(2)
89(2)
109(2)
127(2)
54(1)
58(1)
54(1)
55(1)
12655(6)
13483(6)
12665(6)
13504(6)
12701(6)
13562(7)
12789(8)
11193(3)
6373(3)
C12NH3GeS
Ge1–S5
Ge1–S4
2.122(2)
2.231(1)
2.237(2)
2.250(2)
Ge1–S1
Ge1–S3
Ge2–S6
Ge2–S1
Ge2–S2
Ge2–S3
2.121(2)
2.227(2)
2.236(1)
2.246(2)
N(2)
N(3)
4552(2)
8902(2)
9445(2)
1340(3)
13904(3)
N(4)
C
14NH3GeS
U(eq) is defined as one-third of the trace of the orthogonalized Uij
tensor.
Ge1–S7
Ge1–S4
Ge1–S1
Ge1–S5
2.1214(9)
2.2290(9)
2.2347(8)
2.2483(8)
Table 3
Atomic coordinates (·104) and equivalent isotropic displacement
parameters (A · 10 ) for C12NH3GeS
Ge2–S6
Ge2–S2
Ge2–S1
Ge2–S3
2.1178(9)
2.2287(9)
2.2425(8)
2.2498(9)
2
3
˚
x
y
Z
U(eq)
Ge(1)
Ge(2)
S(1)
4099(1)
4306(1)
3386(1)
5000
7137(1)
7687(1)
7416(1)
7970(1)
7417(1)
6857(1)
6885(1)
7938(1)
7002(1)
7900(1)
6726(1)
6487(1)
6205(2)
5939(2)
5662(2)
5391(2)
5120(2)
4845(2)
5426(2)
5710(2)
5972(2)
6254(2)
8159(2)
8398(2)
8661(2)
8930(2)
9201(2)
9471(2)
9747(2)
10019(2)
10291(2)
5564(2)
5837(2)
6110(2)
1112(1)
3906(1)
2510(2)
2500
42(1)
42(1)
Ge3–S8
Ge3–S9
Ge3–S4
Ge3–S3
2.1224(9)
2.2333(8)
2.2390(8)
2.2514(8)
50(1)
48(1)
S(2)
S(3)
5222(1)
5000
5356(1)
2500
46(1)
46(1)
S(4)
S(5)
3220(1)
3635(1)
1506(3)
1725(3)
1064(4)
1473(4)
1074(5)
1431(5)
1060(5)
1398(5)
1100(6)
1391(6)
1093(6)
1360(5)
1059(7)
1319(6)
1432(6)
1420(10)
1151(8)
1321(7)
1162(7)
1317(6)
1181(7)
1302(7)
1180(7)
3713(7)
3818(7)
3764(7)
ꢀ245(2)
5292(2)
1144(5)
3639(5)
899(7)
56(1)
71(1)
Ge4–S10
Ge4–S9
Ge4–S2
Ge4–S5
2.1225(9)
2.2306(9)
2.2382(8)
2.2556(8)
S(6)
N(1)
N(2)
C(1)
66(2)
64(2)
67(2)
62(2)
C(2)
C(3)
1756(6)
1384(9)
2059(8)
1569(9)
2166(9)
1634(9)
2152(9)
ꢀ3410(9)
ꢀ2927(9)
ꢀ3509(11)
ꢀ3017(10)
4304(9)
3868(9)
4563(11)
4031(9)
4665(10)
4106(9)
4695(10)
4075(10)
4696(10)
920(11)
320(10)
958(12)
98(3)
85(2)
(a)
(b)
C(4)
C(5)
104(3)
104(3)
111(3)
110(3)
124(3)
109(3)
159(5)
143(4)
120(4)
230(8)
167(5)
127(4)
145(4)
121(3)
135(4)
134(4)
134(4)
147(4)
146(4)
178(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
5
10
15
20
25
5
10
15
20
25
2θ (deg), CuKα
2 (deg), CuK
θ
α
(c)
(d)
5
10
15
20
25
5
10
15
20
25
2θ (deg), CuKα
2θ (deg), CuKα
Fig. 1. Powder X-ray diffraction pattern of (a) C12NH3GeS, (b)
C14NH3GeS, (c) C16NH3GeS, and (d) C18NH3GeS. Only the basal
001 reflections are observed.
U(eq) is defined as one-third of the trace of the orthogonalized Uij
tensor.
2.3.4. Differential scanning calorimetry (DSC)
nitrogen flow of 30 mL/min with a rate of 5 ꢀC/min. The
end products of the TGA experiments were examined by
powder X-ray diffraction.
DSC experiments were performed on a computer-
controlled Shimadzu DSC-50 thermal analyzer. About
10 mg of sample were sealed under nitrogen in an

4040
K.K. Rangan, M.G. Kanatzidis / Inorganica Chimica Acta 357 (2004) 4036–4044
aluminum container. An empty container was used as a
reference. All measurements were done with a heating
rate of 2 ꢀC/min.
lected over a full sphere of reciprocal space, up to 58ꢀ in
2h. The individual frames were measured with a h rota-
tion of 0.3ꢀ and acquisition times of 30 s. The SMART
[11] software was used for the data acquisition and
SAINT [12] for the data extraction and reduction. The
absorption correction was performed using SADABS
[13]. Structure solutions and refinements were per-
formed with the SHELXTL package of crystallographic
programs [14]. Intensity statistics suggested that
C12NH3GeS and C14NH3GeS are centrosymmetric.
The structure of C12NH3GeS was solved in the mono-
clinic space group C2/c and C14NH3GeS in the triclinic
2.3.5. X-ray crystallography
Phase analyses were performed using a Rigaku Rota-
flex powder X-ray diffractometer with Ni-filtered Cu Ka
radiation and operating at 45 kV and 100 mA. Crystal-
lographic data sets for the compounds were collected on
a Siemens Platform CCD diffractometer using graphite
monochromatized Mo Ka radiation. The data were col-
ꢀ
space group P1. The structures were solved by the
34
32
30
28
26
24
22
20
18
Patterson method, which gave the positions of the ada-
mantane clusters (Ge and S atoms). In consecutive full-
matrix least-squares refinements, all C and N atoms
were gradually found from subsequent difference Fou-
rier syntheses. The H atoms were placed geometrically
and refined with a riding model using SHELX. Complete
data collection parameters and details of the structure
solution and refinement are given in Table 1.
3. Results and discussion
3.1. Synthesis
12
14
16
18
The CnNH3GeS phases were prepared according to
the metathesis reaction:
Surfactant Chain Length (n)
˚
Fig. 2. Plot of inorganic layer-to-layer distance (A) vs. alkyl chain
length n of the surfactant molecule Cn (n = 12, 14, 16, 18) in
CnNH3GeS phases.
4CnH2nþ1NH3Cl þ Na4Ge4S10
! ½CnH2nþ1NH3ꢂ Ge4S10 þ 4NaCl
4
4ꢀ
Fig. 3. Pseudo-hexagonal arrangement of [Ge4S10
]
clusters in the inorganic layer in C12NH3GeS.

K.K. Rangan, M.G. Kanatzidis / Inorganica Chimica Acta 357 (2004) 4036–4044
4041
The products were recrystallized from ethanol/water
mixtures by heating at 60 ꢀC and cooling slowly to room
temperature. We were able to obtain long plate-type sin-
gle crystals up to 2 mm in length for C12NH3GeS and
C14NH3GeS. In the case of C16NH3GeS and
C18NH3GeS we were able to obtain pure phases only
as microcrystalline powders. (see Tables 2–4).
The X-ray powder diffraction patterns of all the
phases reported here are characteristic of a lamellar
structure showing mainly 001 reflections due to the pre-
ferred orientation of crystallites, Fig. 1. The 001 reflec-
tions are associated with the inorganic layer-to-layer
separation, which increases monotonically with increas-
ing alkyl chain length of the surfactant ammonium cat-
ions, Fig. 2. This observation is similar to previous
reports on lamellar compounds containing isolated ani-
ons such as [Cr2O7]2ꢀ and [Ge4Q10]4ꢀ (Q = S, Se) and
alkyltrimethyl ammonium surfactants [16,8a].
3.2. Crystal structure
C12NH3GeS crystallizes in the monoclinic space
group C2/c with two crystallographically distinct Ge
atoms, whereas C14NH3GeS crystallizes in the lower
ꢀ
symmetry triclinic P1 space group with four crystallo-
graphically distinct Ge atoms. These two compounds
essentially feature the same structural characteristics
presenting alternating layers of [Ge4S10]4ꢀ clusters and
alkyl-ammonium cations. In other words, there is a well
defined lamellar segregation of the organic from the
inorganic moieties in these structures. Solvent molecules
were not found in the lattice, unlike with the lamellar
thiostannate compound [C12H25NH3]4Sn2S6 Æ 2H2O
[16]. Furthermore, the calculation [17]. of the solvent-ac-
cessible surfaces of the CnNH3GeS phases (n = 12, 14)
did not show any void space available to accommodate
even small solvent molecules.
The [Ge4S10]4ꢀ clusters are discrete and packed in a
pseudo-hexagonal fashion where every cluster is sur-
rounded with six neighbors, see Fig. 3. This is similar
to the arrangement of these clusters in the alkyl-tri-
methyl ammonium salts [8]. The average minimum
4ꢀ
˚
intercluster distance is ꢁ10.4 A. The [Ge4S10] clusters
are undistorted with almost perfect (109.47ꢀ) tetrahedral
angles at all Ge atoms (107.2–111.7ꢀ). The bridging Ge–
˚
Sb bond lengths, 2.25 A, are significantly longer than the
˚
terminal Ge–St bonds (2.12 A), and agree well with the
values reported in the literature for Na4Ge4S10 [10].
The adamantane layers are separated by deeply inter-
digitating surfactant chains, Fig. 4. The ammonium
head groups of the four crystallographically different
molecules (two in the case of C12NH3GeS) are posi-
tioned directly towards the adamantane clusters. Each
alkyl chain is perpendicular to the adamantane cluster
layer with a fully extended, all-trans straight chain con-
figuration of C–C bonds, Fig. 5. This alkyl chain
arrangement is very different from that of the alkyl
chains of alkyl-trimethylammonium molecules in
[CnH2n + 1N(CH3)3]4Ge4S10, where they are only
Fig. 4. Structure of C12NH3GeS viewed down the [001] axis. The
˚
inorganic interlayer distance is ꢁ22 A. The alkyl chains are fully
extended being essentially straight and they are positioned perpendic-
4ꢀ
ular to the layer containing the [Ge4S10
]
clusters. The ammonium
head-groups of neighboring surfactant molecules point to opposite
adamantane layers and possess anti-parallel alkyl chains. This defines a
completely interdigitated structure of the surfactant molecules.

4042
K.K. Rangan, M.G. Kanatzidis / Inorganica Chimica Acta 357 (2004) 4036–4044
4ꢀ
]
Fig. 5. Unit cell of C14NH3GeS down [100] axis. The alkyl chains in this case are also positioned perpendicular to the layer containing the [Ge4S10
clusters. The ammonium head-groups of neighboring surfactant molecules are anti-parallel and point to opposite directions.
(b)
(a)
600
500
400
300
200
600
500
400
300
200
Raman Shift (cm-1)
Raman Shift (cm-1)
(c)
(d)
600
500
400
300
200
100
500
400
300
200
Wavenumber (cm-1)
Wavenumber (cm-1)
Fig. 6. Raman spectra of (a) Na4Ge4S10 and (b) C12NH3GeS (c) Far-IR spectra (CsI pellets) of (c) Na4Ge4S10 and (d) C14NH3GeS.
partially interdigitated and are not fully extended but
bent at the middle of the chain [8].
[Ge4S10]4ꢀ cluster. The average N–Hꢃ ꢃ ꢃS bond length
˚
is 2.6 A (dotted bonds in Fig. 6), shorter than the ob-
An important structural feature of the phases de-
scribed here deals with the organic–inorganic interface.
A proton from the R–NH3 head group forms very short
hydrogen bonds with a terminal sulfur atom of the
served values in other compounds showing Hꢃ ꢃ ꢃS hydro-
˚
gen bridges, for example, 3.3 A in Na4Ge2S6 Æ 14H2O.
This is a direct anion–cation interaction that is over
and above the simple coulombic attractive forces pre-

K.K. Rangan, M.G. Kanatzidis / Inorganica Chimica Acta 357 (2004) 4036–4044
4043
sent. Such direct interactions are absent in
[CnH2n + 1N(CH3)3]4Ge4S10 [8]. In the solid state, the
interchain CH2/CH2 van der Waals interactions (con-
(a)
˚
tacts around 4.2 A) contribute further to the stability
of the structure.
3.3. Properties
The Raman and far-IR spectra of C14NH3GeS are
shown in Fig. 6 and are similar those observed for
Na4Ge4S10 [18]. The most intense band at 340 cmꢀ1 in
the Raman spectrum can be assigned to the totally sym-
metric breathing vibration of the [Ge4S6] cage. The band
at 460 cmꢀ1 is due to the totally symmetric stretching
mode of the terminal Ge–S bonds, which occurs at 458
cmꢀ1 in the far-IR spectrum. The band at 393 cmꢀ1 is
due to S–Ge–S bending mode. Thus, the vibrational
spectra clearly exhibit the finger-print pattern for
[Ge4S10] modes. The free tetradecylamine has a sharp
absorption band at 3258 cmꢀ1 which is shifted to 3125
cmꢀ1 in the case of C14NH3GeS because the nitrogen
atom is protonated. The lack of water molecules in the
structure of these materials is further supported by the
absence of bands near 3400 cmꢀ1 corresponding to O-
H stretching vibrations.
0
1
2
3
4
5
6
Energy (eV)
(b)
-10
-20
-30
-40
-50
-60
Ge4S6(SH)4 ??
step 1
54%
step 2
59%
0
100
200
300
400
500
Temperature (oC)
The solid state UV–Vis absorption spectrum of
C12NH3GeS shows an absorption edge at 3.56 eV, Fig.
7a. The absorption is due to intra-cluster excitations
and as expected it does not vary with the change in
the alkyl chain length of the surfactants.
(c)
The CnNH3GeS phases decompose before melting as
suggested by TG, DSC and pyrolysis mass spectrometry,
Fig. 7(b). Under TGA conditions weight loss is observed
in two steps between 200 and 500 ꢀC. In the case of
C12NH3GeS, the first step beginning at ꢁ200 ꢀC corre-
sponds to the loss of all four C12H25NH2 molecules as
volatile products (weight loss observed 54%, calculated
53.9%). At this point the remaining material corre-
sponds to Ge4S6(SH)4 an intermediate which seems to
have some stability under these conditions. The second
weight loss step between 300 and 500 ꢀC (ꢁ5%) is due
to loss of H2S from the intermediate compound. The
presence of Ge4S6(SH)4 was not verified experimentally
in this work but this molecule is known to be stable
[19]. The general decomposition route can be formulated
as:
72
40 60 80 100 120 140 160 180
Temperature (oC)
Fig. 7. (a) Solid state UV–Vis absorption spectrum. (b) TG analysis
plot. Sample under nitrogen flow with a heating rate of 5 ꢀC/min and
(c) DSC plot of C12NH3GeS. The heating rate was 5 ꢀC/min.
N(CH3)3]4Ge4S10 (n = 12, 14, 16, and 18) materials and
concomitant destruction of the adamantane cluster. This
observation has implications towards designing meso-
structured metal chalcogenides templated by surfactants
containing N–H groups, so that facile removal of surfac-
tants can be expected.
½CnH2nþ1NH3ꢂ Ge4S10 ! 4CnH2nþ1NH2 þ Ge4S6ðSHÞ
4
4
DSC experiments show that CnNH3GeS undergo
endothermic solid-state phase transition well below the
decomposition temperature. The transition is very well
defined and occurs in the range 60–80 ꢀC depending
on the alkyl chain length of the surfactant molecules,
Fig. 7c. These phenomena are attributed to the con-
formational changes of the alkyl chains packed between
Ge4S6ðSHÞ ! 4GeS2 þ 2H2S
4
This mechanism also observed with pyrolysis mass
spectrometry. It shows that the surfactants are removed
as neutral molecules without the extraction of sulfide
ions from the [Ge4S10] clusters. This behavior is in con-
trast to the loss of (CH3)2S observed in [CnH2n + 1

4044
K.K. Rangan, M.G. Kanatzidis / Inorganica Chimica Acta 357 (2004) 4036–4044
(c) B.J. Scott, G. Wirnsberger, G.D. Stucky, Chem. Mater. 13
(2001) 3140;
the inorganic layers. Similar phase transitions were
extensively studied in systems such as [CnH2n + 1NH3]2-
MCl4 (M = Co2+, Zn2 +) [20]. and also observed in
[C16Py]2[CdCl4] [21] and Cn-GeS and Cn-GeSe systems
[8].
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Because the [CnH2n + 1N(CH3)3]4Ge4Se10 (n = 8, 9,
10, 12, 14, 16, 18) salts [8a] were reported to absorb
reversibly a variety of alcohols by modulating their
interlayer distance, we investigated the CnNH3GeS
phases for similar behavior. Interestingly, the mesopha-
ses reported here do not show absorption of alcohols or
other polar solvents. The interlayer distance in
CnNH3GeS did not change upon contact with a variety
of alcohols such as methanol, ethanol, propanol and
butanol. Branched alcohols did not absorb either. We
attribute this difference in absorption behavior between
the two types of mesolamellar phases primarily to the
strong hydrogen bonding interactions of the R-NH3þ
head group with the [Ge4S10]4ꢀ cluster. The Nꢃ ꢃ ꢃS dis-
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681;
˚
tance of 3.3 A for NH3 group is much shorter than
(b) K.K. Rangan, P.N. Trikalitis, M.G. Kanatzidis, J. Am.
Chem. Soc. 122 (2000) 10230;
þ
˚
the 4.0 A for R-NMe3 group. Evidently, this interaction
cannot be disturbed when exposed to alcohols and the
materials are not penetrated by the polar molecules.
On the contrary, the electrostatic interaction between
the terminal sulfur atoms of the cluster and the
R-NMeþ3 groups in [CnH2n + 1N(CH3)3]4Ge4Se10 are
comparatively much weaker and allow the insertion of
alcohols which presumably can establish their own
hydrogen bonding with [Ge4S10]4ꢀ. This would suggest
that in the latter, the alcohols insert into organic-inor-
ganic interface rather than in the Van der Walls space
between the alkyl chains of the surfactants.
(c) K.K. Rangan, P.N. Trikalitis, T. Bakas, M.G. Kanatzidis,
Chem. Commun. (2001) 809.
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Acknowledgement
[9] T.J. McCarthy, S.-.P. Ngeyi, J.-.H. Liao, D.C. DeGroot, T.
Hogan, C.R. Kannewurf, M.G. Kanatzidis, Chem. Mater. 5
(1993) 331.
Financial support from the National Science Foun-
dation CHE-0211029 (Chemistry Research Group) is
gratefully acknowledged.
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[11] SMART, version 5: Siemens Analytical X-ray Systems, Inc.
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