Semiconducting nanostructured copper sulfide thin films from bidentate copper(ii) complexes of N-(dialkylcarbamothioyl)-nitrosubstituted benzamides by chemical vapour deposition

Article abstract of DOI:10.1039/c3nj00668a

Copper(ii) complexes of various N-(dialkylcarbamothioyl)-nitrosubstituted benzamide [dialkyl = di-n-butyl (1a, 2a); hexyl, methyl (3a); butyl, ethyl (4a)] have been synthesized and characterized by elemental analysis, IR spectroscopy and atmospheric pressure chemical ionization-mass spectrometry (MS-APCI). The molecular structure of the complex 2a was determined by single-crystal X-ray diffraction. These complexes were used as single-source precursors for the deposition of copper sulfide thin films by aerosol assisted chemical vapour deposition (AA-CVD) at 350 °C. The powder X-ray diffraction (p-XRD) patterns of the thin films of complexes 3a and 4ashowed the deposition of rhombohedral digenite Cu₉S₅ phase, and complex 1a deposited monoclinic roxbyite Cu₇S₄ phase at 350 °C with spherical crystallites. Complex 2a deposited orthorhombic anilite Cu₇S ₄ phase with spherical crystallites. The degree of roughness of the film surface was determined by atomic force microscopy (AFM). The scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) results showed the uniform distribution of copper sulfide in the films, which makes them useful semiconducting materials on a structured surface.

Full text of DOI:10.1039/c3nj00668a

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Semiconducting nanostructured copper sulfide
thin films from bidentate copper(II) complexes
of N-(dialkylcarbamothioyl)-nitrosubstituted
benzamides by chemical vapour deposition†
Cite this: NewJ.Chem., 2013,
3
7, 3214
ab
a
b
c
Sohail Saeed,* Naghmana Rashid, Rizwan Hussain, Muhammad Azad Malik,
c
d
Paul O’Brien and Wing-Tak Wong
Copper(II) complexes of various N-(dialkylcarbamothioyl)-nitrosubstituted benzamide [dialkyl = di-n-butyl
1a, 2a); hexyl, methyl (3a); butyl, ethyl (4a)] have been synthesized and characterized by elemental
(
analysis, IR spectroscopy and atmospheric pressure chemical ionization-mass spectrometry (MS-APCI).
The molecular structure of the complex 2a was determined by single-crystal X-ray diffraction. These
complexes were used as single-source precursors for the deposition of copper sulfide thin films by
aerosol assisted chemical vapour deposition (AA-CVD) at 350 1C. The powder X-ray diffraction (p-XRD)
patterns of the thin films of complexes 3a and 4ashowed the deposition of rhombohedral digenite
Cu
9
S
5
phase, and complex 1a deposited monoclinic roxbyite Cu
7 4
S phase at 350 1C with spherical
Received (in Montpellier, France)
9th June 2013,
1
crystallites. Complex 2a deposited orthorhombic anilite Cu S
7 4
phase with spherical crystallites. The degree
Accepted 27th July 2013
of roughness of the film surface was determined by atomic force microscopy (AFM). The scanning
electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) results showed the uniform
distribution of copper sulfide in the films, which makes them useful semiconducting materials on a
structured surface.
DOI: 10.1039/c3nj00668a
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that in 1940 only the end member (Cu
2
S) and CuS were known
Introduction
in the Cu–S system. By 1974 nine more copper sulfide phases
Recently, nanostructured materials have attracted great atten- had been identified11,12 and in 2006 a total of fourteen copper
1
2
tion in the fields of experimental and theoretical chemistry sulfide phases were recognized. Some known forms of copper
1
–3
sciences. Due to the extensive dependence of the properties sulfide include: chalcocite (Cu S), djurleite (Cu S or Cu1.94S),
2
31 16
and application of nanostructured semiconductors on their digenite (Cu9S5 or Cu1.8S), anilite (Cu S or Cu1.75S), covellite
7
4
7
–13
crystal phase, size, composition and shape, the synthesis of (CuS) and villamaninite (CuS2).
Thin films of copper sulfide
have been prepared by various methods including RF-reactive
4
highly tuned nanocrystals has been a challenging issue.
1
4
15
Copper sulfides thin films and nanoparticles have been sputtering, spray pyrolysis, successive ionic layer adsorption
1
6
17
investigated for many uses including as: p-type semiconductors and reaction, chemical bath deposition and chemical vapor
in solar cells, nanoscale switches and cathodic materials for deposition.
5
–7
8
18
9
10
lithium rechargeable batteries. Vaughan and Craig reported
Thiourea and its alkyl derivatives are important precursors
for the preparation of metal sulfide nanoparticles. Besides
focusing on the applications of these ligands, special attention
has been placed on their coordination chemistry to different
metal atoms because of the various potential donor sites
a
Department of Chemistry, Research Complex, Allama Iqbal Open University,
Islamabad-44000, Pakistan. E-mail: sohail262001@yahoo.com;
Fax: +92 51 9250081; Tel: +92 51 9250081
b
National Engineering & Scientific Commission, P.O. Box 2801, Islamabad,
1
9
19
20
that these ligands possess. Arslan et al. and Binzet et al.
Pakistan
c
School of Chemistry, The University of Manchester, Oxford Road, Manchester,
reported the complexation of Cu(II) and Zn(II) with thiourea
derivatives and concluded that the coordination was through
the sulfur and oxygen atom, using infrared spectroscopy and
X-ray diffractions to determine the coordination. In addition, com-
plexes prepared using the alkyl thiourea, such as methylthiourea,
showed, using infrared spectroscopy, that the coordination was also
M13 9PL, UK
d
Department of Chemistry, The University of Hong Kong, Pokfulam Road,
Hong Kong SAR, People’s Republic of China
†
Electronic supplementary information (ESI) available: Scanned copies of APCI
mass spectra of precursors. CCDC 879352. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/c3nj00668a
3
214 New J. Chem., 2013, 37, 3214--3221
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2
1
through sulfur.
Thiourea and its derivatives were used Preparation of the ligands and copper(II) complexes
as a source of sulfur because their advantages in this regard
are that they are stable for a long time, easy to synthesise,
inexpensive and yield good quality crystalline semiconductor
particles.
Our interest in such precursors led us to synthesize a series
of symmetrical and unsymmetrical copper complexes with the
ligands, N-(dialkylcarbamothioyl)-nitrosubstitutedbenzamide,
Synthesis of N-[dibutylcarbamothioyl]-3,5-dinitrobenzamide
1). A solution of 3,5-dinitrobenzoyl chloride (0.01 mol) in
(
anhydrous acetone (80 ml) and 0.3 mol% of tetrabutyl-
ammonium bromide (TBAB) in acetone was added drop-wise
to a suspension of sodium thiocyanate in acetone (50 ml) and
the reaction mixture was refluxed for 45 minutes. After cooling
to room temperature, a solution of di-n-butylamine (0.01 mol)
in acetone (25 ml) was added and the resulting mixture refluxed
for 2 h. The reaction mixture was poured into five times its
volume of cold water, whereupon the acylthiourea precipitated.
The solid product was washed with water and purified by
re-crystallization from an ethanol–dichloromethane mixture
(1–4), to be used as single source precursors for copper sulfide.
The ligands and copper complexes can be easily synthesized
in high yields from relatively inexpensive and only mildly
hazardous starting materials, making them ideal for the
potential large scale manufacturing of copper sulfide nano-
structured thin films.
(
1 : 2). Blackish brown in semi-solid state. M.p.: 92–93 1C. Yield:
ꢀ
1
3
1
.4 g (78%). IR (nmax/cm ): 3206 (NH), 2955, 2847 (C–H),
1
3
685 (CQO), 1261 (CQS). H NMR (400 MHz, CDCl ) in d
Experimental section
(
ppm) and J (Hz): d 9.10 (t, 1H, J = 1.8), 8.85 (d, 2H, J = 1.8),
8
.38 (bs, 1H, CONH), 3.97 (t, 2H, N–CH ), 3.52 (t, 2H, N–CH ),
Materials and reagents
ꢀ
ꢀ
2 2
ꢀ
1.83 (m, 2H, –CH –), 1.68 (m, 2H, –CH –), 1.46 (m, 2H, –CH –),
ꢀ
2 2 2
ꢀ
ꢀ
Analytical grade 4-nitrobenzoyl chloride (Z98.0%), N-hexyl-
methylamine (Z98%), N-ethylbutylamine (98%), di-n-butyl amine
1.32 (m, 2H, –CH –), 1.01 (t, 3H, CH ), 0.92 (t, 3H, CH ). Anal.
ꢀ
2 3 3
ꢀ
ꢀ
22 4 5
calcd for C16H N O S: C, 50.25; H, 5.80; N, 14.65; S, 8.38.
Found: C, 50.23; H, 5.83; N, 14.67; S, 8.35.
Synthesis of N-(dibutylcarbamothioyl)-4-nitrobenzamide (2).
Ligand (2) was synthesized by the method described for ligand
(
(
3
99%), sodium thiocyanate (99%), copper(II) nitrate trihydrate
99.5%), tetrabutylammonium bromide (TBAB) (Z98%) and
,5-dinitrobenzoyl chloride (Z98.0%) were purchased from
Sigma-Aldrich. Analytical grade solvents such as; tetrahydro-
furan (THF), toluene, acetonitrile, n-hexane, dichloromethane,
ethanol, methanol, chloroform, ethyl acetate and others were
purchased from Sigma-Aldrich and Riedel-de Ha ¨e n (Germany)
whereas ethanol and acetone were dried using standard proce-
(1) using di-n-butylamine. Light yellow. M.p.: 86–87 1C. Yield:
ꢀ1
3
.3 g (86%). IR (nmax/cm ): 3227 (NH), 2931, 2840 (C–H), 1685
1
(CQO), 1259 (CQS). H-NMR (400 MHz, CDCl ) in d (ppm):
3
8
2
1
.41 (br s, 1H, CONH), 8.29 (d, 2Hmeta, p-nitrophenyl), 8.05 (d,
H
ortho, p-nitrophenyl), 3.97 (t, 2H, N–CH ), 3.55 (t, 2H, N–CH ),
2
2
2
2
ꢀ
ꢀ
dures. All manipulations were carried out in air except for the
thermolysis experiments. The thermolysis experiments were
2 2 2
.97 (m, 2H, CH ), 1.75 (m, 2H, CH ), 1.42 (m, 2H, CH ), 1.31
ꢀ
ꢀ
ꢀ
2 3 3
(m, 2H, CH ), 1.01 (t, 3H, –CH ), 0.92 (t, 3H, –CH ); anal. calcd
ꢀ
ꢀ
ꢀ
2
carried out under an inert N atmosphere.
23 3 3
for C16H N O S: C, 56.95; H, 6.87; N, 12.45; S, 9.50. Found: C,
5
6.93; H, 6.89; N, 12.44; S, 9.54.
Synthesis of N-[hexyl(methyl)carbamothioyl]-3,5-dinitro
Physical measurements
Elemental analysis was performed by the University of benzamide (3). Ligand (3) was synthesized by the method
Manchester micro-analytical laboratory. Infrared spectra were described for ligand (1) using N-hexylmethylamine. Light
recorded on a Specac single reflectance Attenuated Total Reflec- yellow in semi-solid state. M.p.: 98–99 1C. Yield: 3.3 g
ꢀ
1
ꢀ1
ꢀ1
1
tance (ATR) instrument (4000–400 cm , resolution 4 cm ). The (78%). IR (nmax/cm ): 3176 (NH), 2959, 2877 (C–H), 1685
Atmospheric Pressure Chemical Ionization Mass Spectrometry (CQO), 1262 (CQS). H NMR (400 MHz, CDCl ) in d (ppm)
3
(MS-APCI) of the copper complexes was recorded on a Micro- and J (Hz): d 9.11 (t, 1H, J = 1.8), 8.83 (d, 2H, J = 1.8), 8.38 (bs,
mass Platform II instrument. Metal analysis of the complexes 1H, CONH), 3.90 (t, 2H, N–CH ), 3.01 (s, 3H, CH ), 2.57 (m, 2H,
ꢀ
ꢀ
2
ꢀ
ꢀ
3
was carried out by Thermo iCap 6300 Inductively Coupled –CH –), 1.83 (m, 2H, –CH –), 1.66 (m, 2H, –CH –), 1.27 (m, 2H,
Plasma Optical Emission Spectroscopy (ICP-OES). All the –CH –), 0.90 (t, 3H, CH ). Anal. calcd for C H N O S: C, 48.90;
complexes were studied by thermogravimetry in an inert atmo- H, 5.47; N, 15.21; S, 8.70. Found: C, 48.87; H, 5.49; N, 15.20;
sphere, at a sample heating rate of 10 1C min , with a DuPont S, 8.70.
000 ATG. Melting points were recorded on Barloworld SMP10
Synthesis of N-[ethyl(butyl)carbamothioyl]-4-nitrobenza-
ꢀ
ꢀ
2
ꢀ
2
2
2
ꢀ
3
15 20 4 5
ꢀ
1
2
Melting Point Apparatus. The X-ray Powder Diffraction (p-XRD) mide (4). Ligand (4) was synthesized by the method described
studies were performed on a Bruker SMART 1000 CCD diffract- for ligand (1) using N-ethylbutylamine. Yellow. M.p.: 89–90 1C.
ꢀ
1
ometer using Cu-Ka radiation. The samples were mounted flat Yield: 3.3 g (90%). IR (nmax/cm ): 3233 (NH), 2931, 2852 (C–H),
1
and scanned between 20 and 651 with a step size of 0.05 with 1691 (CQO), 1256 (CQS). H NMR (400 MHz, CDCl ) in d
3
various count rates. The diffraction patterns were then compared (ppm): 8.45 (s, 1H, CONH), 8.12 (d, 2Hmeta, p-nitrophenyl),
to the documented patterns in the International Centre Diffrac- 7.35 (d, 2Hortho, p-nitrophenyl), 3.82 (t, 2H, CH ), 3.54 (m, 2H,
2
tion Data (ICDD) index. SEM analysis was performed using a CH ), 1.85 (m, 2H, CH ), 1.65 (m, 2H, CH ), 0.98 (t, 3H, CH ),
2
2
2
3
Philips XL 30FEG and Energy Dispersive X-ray (EDX) analyses 0.91 (t, 3H, CH
); anal. calcd for C14
H
N
19
O
S: C, 54.35; H,
3
3
3
were carried out using a DX4 instrument. AFM analysis was 6.19; N, 13.58; S, 10.36. Found: C, 54.32; H, 6.35; N, 13.57;
carried using a Veeco CP2 instrument.
S, 10.37.
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Synthesis of bis[N-[dibutylcarbamothioyl]-3,5-dinitrobenz the transport of the aerosol. This round-bottom flask was
amide]copper(II) (1a). To a stirred solution of the thiourea ligand connected to the reactor tube by a piece of reinforced tubing.
(0.01 mol) in ethanol (30 ml), was added drop-wise a solution of The argon flow rate was controlled by a Platon flow gauge.
copper nitrate (0.005 mol) in ethanol (30 ml). The reaction Seven soda glass substrates (approx. 1 ꢁ 2 cm) were placed
mixture was stirred for 3 h. The reaction mixture was filtered, inside the reactor tube, which was placed in a CARBOLITE
washed with ethanol and re-crystallized from THF: acetonitrile furnace. The precursor solution in a round-bottom flask was
mixture (1 : 1). The quantities used were 3.82 g (0.01 mol) ligand kept in a water bath above the piezoelectric modulator of a
(
1) and 1.20 g (0.005 mol) copper nitrate in ethanol. Green PIFCO ultrasonic humidifier (Model No. 1077). The aerosol
ꢀ
1
shining small particles. Yield: 3.8 g (77%). IR (nmax/cm ): 2929, droplets of the precursor thus generated were transferred into
856 (Ar–H), 1505 (C–O), 1537 (C–N), 1142 (C–S); anal. calcd for the hot wall zone of the reactor by carrier gas. Both the solvent
C H N O S Cu: C, 46.51; H, 5.12; N, 13.56; S, 7.76; Cu, 7.69. and the precursor were evaporated and the precursor vapor
2
3
2 42 8 10 2
Found: C, 46.32; H, 5.27; N, 13.57; S, 7.73; Cu, 7.03. Mass reached the heated substrate surface where thermally induced
+
(
MS-APCI) (major fragment, m/z): 826 [M , C H N O S Cu].
reactions and film deposition took place.
3
2
42 8 10 2
Synthesis of bis[N-(dibutylcarbamothioyl)-4-nitrobenzamide]-
copper(II) (2a). Quantities used were 3.37 g (0.01 mol) ligand (2)
Results and discussion
and 1.20 g (0.005 mol) copper nitrate in ethanol. Light green.
ꢀ
1
Yield: 3.4 g (76%). IR (nmax/cm ): 2929, 2852 (Ar–H), 1506 (C–O), Most of the materials reported for photovoltaic uses are either
532 (C–N), 1139 (C–S); anal. calcd for C32 Cu: C, 52.19; toxic or use less-abundant elements, such as lead, cadmium,
H, 6.02; N, 11.41; S, 8.71; Cu, 8.63. Found: C, 51.87; H, 6.34; N, indium or gallium. Less-toxic, abundant, and thus cheaper
1
44 6 6 2
H N O S
1
1.48; S, 8.70; Cu, 8.37. Mass (MS-APCI) (major fragment, m/z): materials may be more promising even with overall lower
+
7
36 [M , C H N O S Cu].
efficiencies. Recent estimates of the annual electricity
Synthesis of bis[N-[hexyl(methyl)carbamothioyl]-3,5-dinitro potential, as well as material extraction costs and environ-
benzamide]copper(II) (3a). Quantities used were 3.68 g (0.01 mol) mental friendliness, led to the identification of materials that
3
2
44 6 6 2
2
4
ligand (3) and 1.20 g (0.005 mol) copper nitrate in ethanol. Green. could be used in photovoltaic applications on a large scale.
ꢀ1
Yield: 3.9 g (81%). IR (nmax/cm ): 2926, 2856 (Ar–H), 1508 (C–O), The most promising materials include iron and copper
537 (C–N), 1121 (C–S); anal. calcd for C30 Cu: C, 45.13; sulfide.
H, 4.80; N, 14.04; S, 8.05; Cu, 7.96. Found: C, 44.78; H, 4.87; N,
1
38 8 10 2
H N O S
Preparation and spectroscopic characterization
14.00; S, 8.06; Cu, 7.72. Mass (MS-APCI) (major fragment, m/z):
+
798 [M , C H N O S Cu].
Four bidentate ligands were synthesized from nitrosubstituted
30 38 8 10 2
Synthesis of bis[N-[ethyl(butyl)carbamothioyl]-4-nitrobenz benzoyl chloride, ammonium thiocyanate and di-n-butylamine
amide]copper(II) (4a). Quantities used were 3.09 g (0.01 mol) (1 and 2), N-hexylmethylamine (3) and N-butylethylamine (4) in
ligand (4) and 1.20 g (0.005 mol) copper nitrate in ethanol. Dark anhydrous acetone. The thiourea derivatives (1–4) and their
ꢀ
1
brown. M.p.: 175–176 1C. Yield: 3.3 g (78%). IR (nmax/cm ): copper complexes (1a–4a) were synthesized according to the
2
5–30
2928, 2855 (Ar–H), 1508 (C–O), 1535 (C–N), 1140 (C–S); anal. reported procedure
with minor modifications, as pre-
calcd. for C H N O S Cu: C, 49.43; H, 5.33; N, 12.35; S, sented in Scheme 1. The use of a phase transfer catalyst, as a
2
8
36 6 6 2
9
.43; Cu, 9.34. Found: C, 49.51; H, 5.56; N, 12.22; S, 9.45; method of agitating a heterogeneous reaction system, is gain-
3
1,32
Cu, 9.05. Mass (MS-APCI) (major fragment, m/z): 680 ing recognition.
In search of improved methods to prepare
+
[M , C28
H
36
N
6
O
6
S
2
Cu].
the target ligands by reacting isothiocyanates with nucleophiles, we
have found that the use of tetrabutylammonium bromide (TBAB) as
phase transfer catalysts (PTC) can produce isothiocyanates in good
X-Ray structure determination
The single crystal X-ray diffraction data for compound 2a yield, as reported here. The reaction proceeds via nucleophilic
was collected using graphite-monochromated Mo Ka radiation addition of the secondary amine to the isothiocyanate. Four coordi-
(l = 0.71073 Å) on a Bruker SMART 1000 CCD diffractometer. nated copper(II) complexes (1a–4a) were synthesized by reacting
The structure was solved using direct methods and refined using copper nitrate with N-(dibutylcarbamothioyl)-3,5-dinitrobenza-
2
3
least-square methods on F-squared. All non-hydrogen atoms mide (1), N-(dibutyl carbamothioyl)-4-nitrobenzamide (2), N-
were refined anisotropically. Hydrogen atoms were included in [hexyl(methyl)carbamo thioyl]-3,5-dinitrobenzamide (3) and
calculated positions, assigned isotropic thermal parameters, and N-[ethyl(butyl)carbamo thioyl]-4-nitrobenzamide (4), respec-
allowed to ride on their parent carbon atoms.
tively in ethanol. Analytical, spectral and single crystal X-ray
diffraction studies reveal that these complexes contain two mole-
cules of ligands. The obtained complexes (1a–4a) were green in
color, air stable, non-hygroscopic in nature, and are soluble in
Deposition of copper sulfide thin films by aerosol assisted
chemical vapor deposition (AA-CVD)
Experiments were designed according to those reported by us tetrahydrofuran (THF), acetonitrile, dichloromethane, chloro-
1
8
previously. In a typical experiment, 0.25 g of the precursor form, DMSO, and DMF.
was dissolved in 15 ml tetrahydrofuran (THF) and loaded in a The solid state IR spectra of the acylthiourea ligands and the
ꢀ1
two-necked 100 ml round-bottom flask with a gas inlet that metal complexes in the 4000–400 cm region were compared
allowed the carrier gas (argon) to pass into the solution to aid and assigned on careful comparison. The acylthiourea ligands
3
216 New J. Chem., 2013, 37, 3214--3221
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(
CH), 1505–1508 (C–O), and 1121–1142 (C–S). The most striking
ꢀ
1
changes are the N–H stretching frequency at B3200 cm in
the free ligands, which disappears completely, and is in agree-
ment with both the ligand and complex structure and the
complexation reaction. This indicates the loss of the proton
originally bonded to the nitrogen atom of the (NH–CO) amide
group. Another striking change is observed for the carbonyl
stretching vibrations. The vibrational frequencies due to the
carbonyl (1685–1691 cm ) groups in the free ligands are
shifted (20–25 cm ) towards lower frequencies upon com-
plexation, confirming that the ligands are coordinated to the
ꢀ
1
ꢀ
1
3
6–40
copper(II) ion through the oxygen and sulfur donor atoms.
A comparative absorption pattern of the complexes with the
values of the free ligands demonstrate that the coordination of
the thiourea ligands to the copper atom has a significant effect
on the n(NH), n(CO), and n(CS) frequencies.
Fig. 1 X-Ray structure of 2a. Selected bond lengths (Å) and bond angles (1):
Cu1–O1 1.919 (2), Cu1–S1 2.2448 (11), S1–C8 1.731 (4), S2–C24 1.715 (4),
N1–C1 1.316 (4), N5–C21 1.482 (5), O3–N2 1.212 (4); O1–Cu1–O4 84.88 (10),
O1–Cu1–S1 93.14 (8), S1–Cu1–S2 88.96 (4), C8–S1–Cu1 107.78 (13), C17–O4–
Cu1 130.7 (2).
Scheme 1 Preparation of ligands 1–4 and their copper complexes (1a–4a).
behave both as monodentate and bidentate ligands, depending
upon the reaction conditions. The characteristic bands of the
acylthiourea ligands are between/near to; 3176–3233 (NH),
2931–2954 Ph(CH), 1685–1691 (CQO) and 1256–1262 (CQS),
and there is a slight shift of the stretching frequencies of
the (CN) and (CS) groups due to coordination of the ligands
to the copper atom. As is well known, acylthioureas usually act
as bidentate ligands to transition-metal ions through the acyl
3
3–35
oxygen and sulfur atoms.
The FTIR spectra of the com-
plexes show significant changes when compared with the FT-IR
spectra of the corresponding ligands. The IR spectra of the
complexes show absorption bands at nmax/cm : 2926–2929 Ph copper(II) (2a).
Fig. 2 The unit cell diagram of bis[N-(dibutylcarbamothioyl)-4-nitrobenzamide]-
ꢀ1
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Single crystal X-ray crystallography
The molecular structure and unit cell diagram of bis[N-(dibutyl-
carbamothioyl)-4-nitrobenzamide]copper(II) (2a) are shown in
Fig. 1 and 2, respectively. In 2a structure, the central copper
atom is coordinated to two N-(dibutylcarbamothioyl)-4-nitro-
benzamide ligands in the cis-configuration. The copper atoms
are in a slightly distorted square planar geometry coordinated
by two oxygens and two sulfurs, forming the neutral form of
cis-[CuL ]. There are two molecules of the copper(II) complex in
2
the unit cell (Fig. 2). One of the butyl groups was found to be
disordered in two positions at occupancies of 0.782(16) and
0.218(16), respectively. A total of six restraints have been used
in the refinement. They are related to the anisotropic refine-
0
ment of atom C31 using the isotropic restrains of standard
uncertainty of 0.01, six restraints for each atom. The highest
peak is 0.41 at (0.3899, 0.3586, 0.7181) [1.12 Å from C10] and
the deepest hole is ꢀ0.37 at (0.1563, 0.5255, 0.0791) [0.82 Å
from Cu1]. The weighted R-factor wR and goodness of fit S are
2
based on F , conventional R-factors R are based on F, with F set
2
2
2
2
to zero for negative F (R[F > 2s(F )] = 0.049, wR(F ) = 0.119) and
independent reflections and measured reflections are 6286,
10 157 respectively.
The details for the data collection of the crystals (2a) are as
follows: crystals were obtained by dissolving 0.5 g of the crude
product in a minimum quantity of THF : acetonitrile (1 : 1) to
give a brown clear solution, which was evaporated at room
temperature over two weeks to deposit dark brown blocks.
Crystal data: C32
H
44
N
6
O
6
S
2
Cu, triclinic, space group P1%/c, a =
.585(2) Å, b = 12.347(3) Å, c = 17.326(4) Å, b = 89.305(4)1, V =
828.8(8) Å , T = 300 K, Z = 2, F(000) = 774, D = 1.337 g cm .
x
8
1
3
ꢀ3
Thermogravimetric analysis of precursors 1a–4a
TGA data of complex 1a shows two-step decomposition. The
first step starts at 180 1C and is accomplished at 227 1C, with
weight loss 8.40%. The major part of the complex degraded
sharply in the first region (240–320 1C). The second step
decomposition starts at 325 1C and is completed at 581 1C
and the residual amount left at 600 1C is 16.78%, which is
almost close to the accumulative mass of the decomposed
product CuS (cal. 15.45%). The TGA data of complex 2a also
shows two-step decomposition. The first step starts at 164 1C
and is completed at 335 1C with a weight loss of 67.24%. The
major part of the complex degraded sharply in the first region Fig. 3 X-Ray diffractograms of the copper sulfide thin films obtained from
precursors 1a–4a at 350 1C.
(164–335 1C). In second step, the decomposition starts at 343 1C
and is completed at 586 1C and the residual amount left at
00 1C is 19.01%, which is considerably close to the accumu- thermogram of complex 3a also shows two stages of weight
6
lative mass of the decomposed product CuS (cal. 17.34%). The loss. The first step begins at 41 1C and is accomplished at
Table 1 Thermogravimetric analysis of complexes 1a–4a
1a
2a
3a
4a
1
2
st stage decomposition temperature range (1C)
nd stage decomposition temperature range (1C)
180–227
325–581
240–320
8.40
164–335
343–586
164–335
67.24
41–213
214–582
250–340
1.62
167–563
—
220–310
81.05
18.95
Maximum degradation temperature range (1C)
Weight loss at 1st stage decomposition (%)
Residual weight at 600 1C (%)
16.78
19.01
16.73
3
218 New J. Chem., 2013, 37, 3214--3221
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Table 2 The experimental and calculated lattice parameters of deposited copper sulfide films prepared from precursors 1a–4a
3
2y
Cell parameters (Å)
Cell volume (Å )
Precursors
Obs
JCPDS
34.06
hkl
d-Spacing (Å)
Obs
STD
Obs
STD
Crystallite phase
1
2
3
a
33.82
2001
2.63
a
c
a
c
a
c
55.35
15.85
8.92
13.26
4.25
53.79
13.36
7.90
11.07
3.91
21 528.4
22 205.8
685.1
Cu
Cu
Cu
7
7
9
S
4
S
4
S
5
(monoclinic)
a
46.10
46.12
46.23
46.29
224
110
1.96
1.95
665.86
610.52
(orthorhombic)
(rhombohedral)
a, 4a
638.44
53.93
48.00
2
5
13 1C. The second one starts at 214 1C and is completed at
82 1C, with the residue amounting to 16.73% of the initial
weight at 600 1C. The residual weight (16.73%) is almost close
to the expected composition for CuS (cal. 15.99%), the presence
of which was further supported by XRD analysis of the residue.
The TGA data of complex 4a shows single-step decomposition
of the complex, which starts at 167 1C and is completed by
563 1C. The major part of the complex degraded sharply in the
region of 220–310 1C leaving an approximate residual amount
of 18.95%, which is exactly the same mass of the decomposed
product CuS (cal. 18.77%). The TGA data of the precursors
(1a–4a) is presented in Table 1.
XRD studies
Using the TGA data, the AACVD experiments of the precursors
(1a–4a) were run at 350 1C with an argon flow rate of 160 sccm
on glass substrates. Light black adherent uniform films were
deposited at 350 1C. The X-ray diffraction (XRD) patterns of the
as-deposited films from precursors 1a–4a at 350 1C are shown
in Fig. 3. The diffraction pattern of the crystallite phase
Fig. 4 SEM images of copper sulfide thin films deposited from precursors 1a–4a
at 350 1C.
deposited from precursor 1a is ‘‘monoclinic roxbyite’’ (Cu
in the space group C2/m (12) with major diffraction peaks of the
1600), (804), (2001) and (0160) planes (ICDD: 023-0958). The to (2001), (224) and (110) planes, respectively, for precursors
7 4
S )
(
experimental d-spacing values are in good agreement with the 1a–4a, as presented in Table 2.
standard JCPDS d-spacing values, confirming that the material
SEM and AFM studies
has a monoclinic structure (a = 55.35 Å, c = 15.85 Å) of Cu S .
7
4
The XRD pattern of the copper sulfide thin film from precursor Fig. 4 shows the scanning electron microscopy (SEM) images of
a shows that the deposited crystallite phase is ‘‘orthorhombic the copper sulfide thin films deposited at 350 1C from pre-
anilite’’ (Cu ) and in the space group Pnma (62) with major cursors 1a–4a. The images show the morphology of the films
diffraction peaks of the (202), (004), (224) and (422) planes with evenly distributed small crystallites without any preferred
2
7 4
S
2
4
(ICDD: 033-0489). O’Brien and co-workers
have already orientation and diffusion grain boundaries. The particles with
reported a mixture of cubic CuS
2
and hexagonal Cu S spherical spherical appearances have good orientations and clearly well
2
crystallites at 280 1C, cuboids at 320 1C and plate-like crystallites defined grain boundaries. The thickness of the film and crystal-
i
between 360 and 400 1C, deposited from [Cu(SON(CN Pr ) ) ] by lite size is controlled by the time of deposition and the concen-
2
2 2
4
1
aerosol assisted chemical vapor deposition. The diffraction tration of the precursor solution. EDX analysis of the film
pattern of the deposited crystallite phase from precursor 3a deposited from precursor 1a shows that the composition has
and 4a is ‘‘rhombohedral digenite’’ (Cu
R3%m (166) with major diffraction peaks of the (0015), (1010), and 6) shows the growth of closely packed crystallites onto a
110) and (205) planes (ICDD: 026-0476). The grain sizes of all the glass substrate with an average roughness of 5.98 nm.
deposited crystallite phases were also estimated using the
EDX analysis of the film prepared from precursor 2a shows
FWHM from the Scherrer’s relation, and it is of the order of that the composition has a Cu : S ratio of 77.3 : 22.7. The AFM
9.5 to 65.8 nm.
image of the film shows the growth of closely packed crystal-
The experimental and calculated lattice parameters are cell lites onto a glass substrate with an average roughness of
parameters, cell volume, d-spacing, 2y, hkl planes with respect 14.89 nm. EDX analyses of the films deposited from precursors
9 5
S ) in the space group a Cu : S ratio of 77.2: 22.8. The AFM images of the film (Fig. 5
(
4
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Fig. 6 Histogram of copper sulfide thin films deposited from precursors 1a–4a
at 350 1C showing average roughness and RMS roughness morphologies.
Fig. 5 AFM images in 3D view of copper sulfide thin films deposited from
precursors 1a–4a at 350 1C.
the surface morphology of the films is very much dependant on
the concentration of the precursor solution, configuration of the
precursor (symmetrical or unsymmetrical) and nature of the
4
3
solvents used in the chemical vapour deposition.
3a and 4a show that they have compositions with Cu : S ratios
of 78.1 : 21.9 and 79.85 : 20.15, respectively. The AFM images of
the films prepared from these precursors show the growth of
closely packed crystallites onto a glass substrate with an average
Conclusions
roughness of 16.52 nm and 5.11 nm. In general, the lower We have successfully synthesized a series of new copper(II)
the surface roughness, the less light that is scattered by the complexes of N-(dialkylcarbamothioyl)-nitrosubstituted benza-
4
2
optical surface, and hence the better the surface quality. The mide [dialkyl = di-n-butyl (1a and 2a); hexyl, methyl (3a); butyl,
change of surface roughness is due to the variation of crystallite ethyl (4a)]. The single crystal structure of complex 2a was
size. From the SEM micrographs obtained, we can conclude that determined by X-ray crystallography. These studies have shown
3
220 New J. Chem., 2013, 37, 3214--3221
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NJC
that the metal complexes are neutral in the cis-configuration. 18 M. J. Moloto, N. Revaprasadu, P. O’Brien and M. A. Malik,
AA-CVD from complexes 3a and 4a, deposited the rhombo-
J. Mater. Sci.: Mater. Electron., 2004, 15, 313–316.
hedral digenite Cu S phase at 350 1C with spherical crystal- 19 H. Arslan, U. Fl o¨ rke, N. Kulcu and M. F. Emen, J. Coord.
9
5
lites. Complex 1a deposited monoclinic roxbyite Cu S phase at
Chem., 2006, 59, 223–228.
50 1C with spherical crystallites. Similarly, complex 2a depos- 20 G. Binzet, H. Arslan, U. Fl o¨ rke, N. Kulcu and N. Duran,
ited orthorhombic anilite Cu with spherical crystallites. The
J. Coord. Chem., 2006, 59, 1395–1406.
composition of the films deposited from the different com- 21 R. A. Bailey and T. R. Peterson, Can. J. Chem., 1967, 45,
plexes was confirmed by EDX analysis. The average roughness
1135–1142.
of the deposited films from these precursors was in the range of 22 D. D. Perrin, W. L. F. Armarego and D. R. Perrin, Purification
7
4
3
7 4
S
5.11 to 16.52 nm.
of laboratory chemicals, Pergamon Press Ltd, Oxford, 3rd
edn, 1988.
2
3 G. M. Sheldrick, Acta Crystallogr., Sect. A: Fundam. Crystal-
logr., 2008, 64, 112–122.
Acknowledgements
Sohail Saeed would like to acknowledge the Higher Education 24 A. L. Abdelhady, K. Ramasamy, M. A. Malik, P. O’Brien,
Commission (HEC), Government of Pakistan for financial sup-
port and also would like to thank The University of Manchester
for providing the facilities for this work.
S. J. Haigh and J. Raftery, J. Mater. Chem., 2011, 21,
17888–17895.
25 S. Saeed, N. Rashid, P. G. Jones and A. Tahir,
J. Heterocycl.Chem., 2011, 48, 74–84.
2
6 S. Saeed, N. Rashid, P. G. Jones, M. Ali and R. Hussain, Eur.
J. Med. Chem., 2010, 45, 1323–1331.
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