Heteroleptic copper(i) halides with triphenylphosphine and acetylthiourea: Synthesis, characterization and biological studies (experimental and molecular docking)

Article abstract of DOI:10.1039/c9nj03005k

Nine new copper complexes with the general formula [CuX(TPP)_n(ATU)_3-n] (where X = Cl, Br, and I, ATU = acetylthiourea, TPP = triphenylphosphine and n varies as 0, 1 and 2) were synthesized in a simple fashion, by changing the ratio of the ligands. The synthesized complexes were characterized by techniques, such as FT-IR and NMR spectroscopy, CHNS elemental analysis and single crystal X-ray technique. The XRD technique showed the monodentate behavior of TPP and ATU. The synthesized compounds were utilized in different biological assays, which showed anti-bacterial, anti-fungal, anti-lieshmanial, anti-oxidant and cytotoxic properties against brine shrimps. In parallel, molecular docking was carried out to decipher the binding conformation and chemical interactions of the compounds in the active binding pockets of biological drug targets against bacterial pathogens and lieshmanial parasite, as well as a cancer target. All these analyses revealed compounds [CuCl(TPP)(ATU)₂] and [CuI(TPP)(ATU)₂] to be the most effective molecules of the series. Molecular docking indicated that hydrogen bonding and hydrophobic pi-interactions play important role for the activities of complexes with ligands TPP/ATU ratio of 1/2.

Full text of DOI:10.1039/c9nj03005k

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Heteroleptic copper(I) halides with
triphenylphosphine and acetylthiourea:
synthesis, characterization and biological
studies (experimental and molecular docking)†
d
Cite this: New J. Chem., 2019,
43, 19318
Syed Ishtiaq Khan,‡ab Sajjad Ahmad,‡c Ataf Ali Altaf,
Muhammad Khawar Rauf,a
Amin Badshah, *a Syed Sikander Azam*b and Muhammad Nawaz Tahir
e
Nine new copper complexes with the general formula [CuX(TPP)n(ATU)3ꢀn] (where X = Cl, Br, and I,
ATU = acetylthiourea, TPP = triphenylphosphine and n varies as 0, 1 and 2) were synthesized in a simple
fashion, by changing the ratio of the ligands. The synthesized complexes were characterized by
techniques, such as FT-IR and NMR spectroscopy, CHNS elemental analysis and single crystal X-ray
technique. The XRD technique showed the monodentate behavior of TPP and ATU. The synthesized
compounds were utilized in different biological assays, which showed anti-bacterial, anti-fungal, anti-
lieshmanial, anti-oxidant and cytotoxic properties against brine shrimps. In parallel, molecular docking
was carried out to decipher the binding conformation and chemical interactions of the compounds in
the active binding pockets of biological drug targets against bacterial pathogens and lieshmanial
parasite, as well as a cancer target. All these analyses revealed compounds [CuCl(TPP)(ATU)2] and
[CuI(TPP)(ATU)2] to be the most effective molecules of the series. Molecular docking indicated that
hydrogen bonding and hydrophobic pi-interactions play important role for the activities of complexes
with ligands TPP/ATU ratio of 1/2.
Received 9th June 2019,
Accepted 1st November 2019
DOI: 10.1039/c9nj03005k
rsc.li/njc
forms depending on the oxidation states, and the most common
ones are Cu(II), Cu(I) and rarely Cu(III). The use of Cu(I) and Cu(II)
Introduction
The synthesis of metal containing compounds as drugs has compounds as anti-biological agents has increased in the recent
been one of the most important research fields for the last fifty past, which is clear from the large number of articles published
years. The capability of metals to bind to nucleic acids can during the last two decades.6,7 Copper(I) complexes are studied
bring promising results in the field of metal-based drugs.1,2 less for biological evaluations in comparison to copper(II)
In aerobic organisms, copper is an essential element and is complexes; rather, they are studied for catalytic and photo-
used as a structural and catalytic cofactor.3,4 Among the essential luminescence purposes.7,8 Likewise, complexes of coinage
trace metals, copper has been used as drugs for centuries either in metals, like Ag, Cu and Au with arylphosphine and sulfur
the form of a metal ion or a complex to disinfect liquids, solids donor co-ligands have been studied extensively in the recent
and human tissues.5 Copper exists in a variety of geometrical past9,10 for their potential biological applications, such as
antimicrobial activities.9,11 Our interest for the synthesis of
a Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan.
mixed ligand complexes comes from the current research of
coinage metal coordination complexes with ligands, like hetero-
cyclic thiones,12,13 because of their binding sites’ relevance to
the living systems.6,12 Tertiary phosphines are very useful for
the crystallization of N, S donor ligands with Cu(I) and Ag(I)
complexes.11,14 The structural studies of these complexes suggest
the mononuclear tetrahedral and binuclear with tetrahedral and
trigonal arrangements around the metal atoms.15,16
Thioureas, having N and S, are extensively reported for their
excellent biological activities. N,N0-Disubstituted thioureas are
very remarkable precursors for the synthesis of important
biological compounds when subjected to various structural
E-mail: aminbadshah@yahoo.com
b Geoscience Advance Research Laboratories, Geological Survey of Pakistan,
Islamabad, Pakistan. E-mail: syedazam2008@gmail.com, ssazam@qau.edu.pk
c Computational Biology Lab, National Center for Bioinformatics,
Quaid-i-Azam University, Islamabad, Pakistan
d Department of Chemistry, University of Gujrat, hafiz Hayat Campus,
Gujrat-50700, Pakistan
e Department of Physics, University of Sargodha, Sargodha, Pakistan
† Electronic supplementary information (ESI) available: CIF file for A2 and A3
(CIF file), NMR spectral data (PDF files) and other described data. CCDC 1889116 (A2)
and 1889117 (A3). For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c9nj03005k
‡ Both the authors contributed equally to this work.
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thiourea phosphine copper(I) halide complexes were conducted
on Bruker Smart APEX-II diffractometers.
Synthesis and characterization of precursor
tris(triphenylphosphine)copper(I) halide complexes
Phosphine and copper(I) halide (where the halide was Cl, Br, or I)
complexes were synthesized by the reaction of copper(I) halide salt
and TPP in an acetonitrile solvent at 80 1C under inert atmosphere
in 1 : 3 (salt to ligand), in accordance with literature.23,24 Separate
solutions of the copper salt and TPP were prepared in acetonitrile
and mixed under an inert atmosphere with gentle stirring. Crystal-
line products were collected on a folded filter paper, washed
several times and dried at room temperature. The quantities of
the reactants used for the synthesis of Cu(TPP)3X complexes were
1 mmol of the copper salt (0.099 g of CuCl, 0.143 g of CuBr and
0.190 g of CuI) and 3 mmol of phosphine (0.788 g of TPP).
Chloridotris(triphenylphosphine)copper(I) [Cu(TPP)3Cl]. Three
precursors were prepared according to the above mentioned
general procedure by mixing the salt and TPP in a 1 : 3 ratio.
Physical state: colourless solid, yield 70%, melting point (M.P):
176 1C, anal. calcd for C55H45ClCuP3 (885.87): C, 73.22; H, 5.12;
Cu, 7.17; found C, 73.02; H, 5.06; Cu, 7.01%. FT-IR (ATR,
u in cmꢀ1): 3047 (aromatic C–H), 1584 (aromatic CQC), 1431
(C–P), 740 (TPP). 1H NMR (300 MHz, CDCl3, d in ppm at 25 1C):
d 7.16–7.36 (m, 45H, Ar-H), 13C NMR (75 MHz, CDCl3, d in ppm,
at 25 1C): 128.52 (d, 3J = 8.66 Hz), 129.49, 133.45 (d, 1J = 20.36 Hz),
133.87 (d, 2J = 15.95 Hz, P–C coupling aromatic-C) 128.8, 31P NMR
(31P NMR 121.49 MHz, 83% aqueous H3PO4, d in ppm, at 25 1C):
ꢀ3.53(s).
Chart 1 Drawings of the chemical structures of the precursors (ATU, TPP)
and complexes A1–A9; ATU binds to Cu(I) through the sulfur atom and
TPP binds through phosphorous.
modifications by treating them with different reagents having
different functionalities. In vitro studies have clearly indicated
that thioureas have a remarkable potential as antimalarial and
anticancer agents and a TRPV1 receptor antagonist, while also
having antihypertensive activities.17–19 In the current research
work, we have synthesized new complexes (A1 to A9) of Cu(I)
halide with acetylthiourea (ATU) and triphenylphosphine (TPP)
as shown in Chart 1. All the synthesized complexes were tested
for various biological activities and subjected to molecular
docking studies.
Experimental
Materials and methods
Bromotris(triphenylphosphine)copper(I) [Cu(TPP)3Br]. Physical
state: colourless solid, yield 71%, (M.P): 166 1C, analytical and
calculated for C54H45P3CuBr (930.31): C, 69.72; H, 4.88; Cu, 6.83;
found C, 69.61; H, 4.70; Cu, 6.51%. FT-IR (ATR, cmꢀ1 u): 3047.5
(aromatic C–H), 1584.8 (aromatic CQC), 1433.2 (aromatic C–P),
740.6 (TPP). 1H NMR (300 MHz, CDCl3, d in ppm, at 25 1C): d 7.15–
7.37 (m, 45H, Ar-H), 13C NMR (75 MHz, CDCl3, d in ppm, at 25 1C):
Chemicals, reagents and organic solvents used in this work
were acquired from Sigma-Aldrich. CuCl, CuBr, CuI, organic
acids, N-acetylthiourea (ATU), and triphenylphosphine (TPP)
were used as received without further purification. We used the
following organic solvents: acetone, alcohols, chloroform, dichloro-
methane, petroleum ether and n-hexane. These solvents were
purified and dried as per reported literature methods,20–22
saturated with nitrogen, stored over 4 Å molecular sieves and
degassed before use.
2
128.48 (d, J = 8.73 Hz, P–C coupling aromatic-C), 129.51, 133.58
(d, 3J = 20.64 Hz, P–C coupling aromatic-C), 133.94 (d, 1J =
15.38 Hz, P–C coupling aromatic-C), 31P NMR (121.49 MHz,
83% aqueous H3PO4, d in ppm, at 25 1C), ꢀ4.07 (s).
Iodidotris(triphenylphosphine)copper(I) [Cu(TPP)3I]. Physical
state: colourless solid, yield 73%, (M.P): 150.5 1C, analytical and
Instrumentation
The purity of chemicals was ensured through the melting point calculated for C54H45CuIP3 C, 66.36; H, 4.64; Cu, 6.50; found C,
using the BioCote, model SMP10-UK. A Bruker AV-300 MHz 66.10; H, 4.54; Cu, 6.29%. FT-IR (ATR, cmꢀ1 u): 3048 (aromatic
instrument was used to record NMR spectra using deuterated C–H), 1584.7 (aromatic CQC), 1432 (aromatic C–P), 739.9
1
solvents. For 1H NMR (300 MHz): internal standard solvent (TPP). H NMR (300 MHz, CDCl3, d in ppm, at 25 1C): d 7.14–
CDCl3 (7.28 ppm from TMS (Si(CH3)4)); for 13C NMR (75.47 MHz): 7.38 (m, 45H, Ar-H), 13C NMR (75 MHz, CDCl3, d in ppm, at
internal standard solvent CDCl3 (77.0 ppm from TMS). In 1H NMR 25 1C): d 128.49 (d, 3J = 8.70 Hz, P–C coupling aromatic-C),
spectra, the splitting of proton resonance is defined as s = singlet, 129.54, 133.50 (d, 1J = 20.41 Hz, P–C coupling aromatic-C),
2
d = doublet, t = triplet, and m = multiplet. An attenuated total 133.98 (d, J = 15.29 Hz), 31P NMR (121.49 MHz, 83% aqueous
reflection (ATR) Alpha Bruker Model 1001 8394 machine was H3PO4, d in ppm, at 25 1C): ꢀ4.50.
used for infrared (IR) absorption measurements in the range of
4000–400 cmꢀ1. For elemental analyses, Fisons EA1108 CHNS
General synthesis procedure for heteroleptic copper(I) halides
(compounds A1–A9)
analyzer was utilized, while the metal (copper) contents were
determined on a PerkinElmer A800 atomic absorption spectro- The TPP and ATU containing copper halide complexes (A1–A3)
photometer (AAS). Single crystal analyses of the synthesized of type [Cu(TPP)2(ATU)X] were synthesized by the reaction of
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[CuX(TPP)3] and ATU in a methanol and chloroform mixture [CuI(TPP)3] and ATU in 1 : 1 ratio. Yield 71%, (M.P): 180 1C,
under reflux. ATU (1 mmol) and Cu(TPP)3X (X = Cl, Br, and I; analytical and calculated for C39H36ICuN2OP2S (833.19): C,
1 mmol) were separately dissolved in methanol (20 mL) and 56.22, H, 4.36, N, 3.36, S, 3.85, Cu, 7.63, found, C, 55.98,
chloroform (10 mL), respectively. The solution of ATU was kept H, 4.15, N, 3.18, S, 3.57, Cu, 7.47%. FT-IR, (ATR, u in cmꢀ1):
under stirring and the Cu(TPP)3X solution was added dropwise 3211.2 (N–H), 3157 (aromatic C–H), 2978 (aliphatic C–H), 1708.5
at room temperature. A white precipitate was obtained, which (CQO), 1519.7 (aromatic CQC), 1432 (aromatic C–P), 1219.6
was collected on a folded filter paper, followed by washing and (CQS), 1093.3 (C–N), 1054.5, 743 (TPP). 1H NMR (300 MHz,
drying. The filtrate was kept for crystallization and fine colour- CDCl3, d in ppm, at 25 1C): d 2.14 (s, 3H, CH3), 7.16–7.53 (broad
less crystals were collected after 48 h.
m, 30H, Ar-H), 9.80, (s, 2H, NH2 protons), d 10.75 (s, 1H, NH
For the synthesis of [Cu(TPP)(ATU)2X] type complexes proton), 13C NMR (75 MHz, CDCl3, d in ppm, at 25 1C): d 24.76
(A4–A6), a CuX (1 mmol) suspension was prepared in aceto- (CH3 carbon), 128.35 (d, 2J = 8.88 Hz, P–C coupling, Ar-C), 129.53,
nitrile (20 mL) and was kept under stirring. A clear solution of 133.39 (d, 1J = 26.47 Hz, P–C coupling, Ar-C), 134.04 (d, 3J =
ATU (2 mmol in acetonitrile (20 mL)) was added dropwise to 14.13 Hz, P–C coupling, Ar-C), 172.37, 180.36, 31P NMR
the suspension of the copper salt, which resulted in a white (121.49 MHz, 83% aqueous H3PO4, d in ppm at 25 1C): d ꢀ5.22.
precipitate. The precipitate got dissolved upon the addition of
Chloridodiacetylthioureatriphenylphosphinecopper(I) [Cu(TPP)-
the TPP solution ((1 mmol) in acetonitrile (20 mL)). The final (ATU)2Cl] (A4). A4 was prepared from the reaction between CuCl,
mixture was kept under stirring at 80 1C for 48 h. Afterward, TPP and ATU according to the above described procedure. Yield
rotary evaporation was used to concentrate the solution and the 67%, (M.P): 205 1C, analytical and calculated for C24H27ClCu-
clear solution was kept for crystallization. Transparent crystals N4O2PS2 (597.60): C, 48.24, H, 4.55, N, 9.38, S, 10.73, Cu, 10.63,
were collected after 48 h. The same process was repeated for found, C, 47.98, H, 4.33, N, 9.19, S, 10.59, Cu, 10.40%. FT-IR, (ATR,
Cu(ATU)3X type complexes (A7–A9). The ATU solution (3 mmol) u in cmꢀ1): 3298 (N–H), 3152 (aromatic C–H), 2980 (aliphatic C–H)
was added and a white crystalline-precipitate was collected 1702 (CQO), 1522 (aromatic CQC), 1432 (aromatic C–P), 1226
after washing and drying.
(CQS), 1093 (C–N), 744 (TPP), 1H NMR (300 MHz, (CD3)2SO,
Chloridoacetylthiourea-bis-(triphenylphosphine)copper(I) d in ppm, at 25 1C): d 2.10 (s, 6H, CH3), 7.06–7.69 (m, 15H, Ar-H),
[Cu(TPP)2(ATU)Cl] (A1). A1 was prepared from [CuCl(TPP)3] 9.88 (s, 2H, NH proton), 11.43 (s, 4H, NH2 protons), 13C NMR
3
and ATU according to the above described procedure. Yield 70%, (75 MHz, (CD3)2SO, d in ppm, at 25 1C): d 24.49, 129.27 (d, J =
1
(M.P): 190 1C, analytical and calculated for C39H36ClCuN2OP2S 9.16 Hz, P–C coupling, Ar-C), 130.62, 133.17 (d, J = 30.13 Hz,
(741.73): C, 63.15, H, 4.89, N, 3.78, S, 4.32, Cu, 8.35, found, P–C coupling, Ar-C), 133.77 (d, 2J = 15.11 Hz, P–C coupling, Ar-C),
C, 62.97, H, 4.58, N, 3.51, S, 4.16, Cu, 8.02%. FT-IR, (ATR, u 172.41, 179.84, 31P NMR (121.49 MHz, 83% aqueous H3PO4, d in
in cmꢀ1): 3294 (N–H), 3151 (aromatic C–H), 1703 (CQO), 1534 ppm at 25 1C): d ꢀ4.02.
(aromatic CQC), 1432 (C–P), 1227 (CQS), 1092 (C–N), 742 u (TPP),
Bromidodiacetylthioureatriphenylphosphinecopper(I) [Cu(TPP)-
1H NMR (300 MHz, CDCl3, d in ppm, at 25 1C): d 2.09 (s, 3H, CH3), (ATU)2Br] (A5). A5 was prepared from the reaction of CuBr, TPP and
7.18–7.50 (m, 30H, Ar-H), 9.82, (s, 2H, NH2 protons), 11.96 (s, 1H, ATU in 1 : 1 : 2 ratio. Yield 72%, (M.P): 195–200 1C, analytical and
NH proton), 13C NMR (75 MHz, CDCl3, d in ppm, at 25 1C): d 24.56 calculated for C24H27BrCuN4O2PS2 (642.05): C, 44.90, H, 4.24, N,
(CH3 carbon), 128.34 (d, 2J = 8.72 Hz, P–C coupling, Ar-C), 129.36, 8.73, S, 9.99, Cu, 9.90, found, C, 44.58, H, 4.01, N, 8.41, S, 9.61, Cu,
133.91 (d, 1J = 14.93 Hz, P–C coupling, Ar-C), 134.12, 172.76, 9.59%. FT-IR, (ATR, u in cmꢀ1): 3287.9 (N–H), 3138.9, 1701.7,
181.37, 31P NMR (121.49 MHz, 83% aqueous H3PO4, d in ppm at 1597.6, 1524.3, 1478.2, 1432, 1365.5, 1221, 1093.7, 1053.3, 944.4,
1
25 1C): d ꢀ3.13.
799.8, 742.2, 690.9, 603.3, 514.4, 502.7, 405.7, H NMR (300 MHz,
Bromidoacetylthiourea-bis-(triphenylphosphine)copper(I) (CD3)2SO, d in ppm, at 25 1C): d 2.01 (s, 6H, CH3), 7.04–7.69
[Cu(TPP)2(ATU)Br] (A2). A2 was prepared from the reaction (m, 15H, Ar-H), 9.47 (s, 4H, NH2 proton), 10.89 (s, 2H, NH protons),
of [CuBr(TPP)3] and ATU in 1 : 1 ratio. Yield 74%, (M.P): 13C NMR (75 MHz, (CD3)2SO, d in ppm at 25 1C): d 24.15, 127.26
195 1C, analytical and calculated for C39H36BrCuN2OP2S (d, 2J = 8.25 Hz, P–C coupling, Ar-C), 128.52, 129.46, 130.68 (d, 1J =
(786.19): C, 59.58, H, 4.62, N, 3.56, S, 4.08, Cu, 8.08, found, 31.50 Hz, P–C coupling, Ar-C), 171.20, 177.61, 31P NMR (121.49 MHz,
C, 59.19, H, 4.47, N, 3.41, S, 3.92, Cu, 8.74%. FT-IR, (ATR, u in 83% aqueous H3PO4, d in ppm at 25 1C): d ꢀ4.45.
cmꢀ1): 3302, 3213, (N–H), 3147 (aromatic C–H), 2985 (aliphatic
Iodidodiacetylthioureatriphenylphosphinecopper(I) [Cu(TPP)-
C–H), 1709 (CQO), 1527 (aromatic CQC), 1431.6 (aromatic C–P), (ATU)2I] (A6). A6 was prepared from the reaction of CuI, TPP
1
1266 (CQS), 1092 (C–N), 744.3 (TPP). H NMR (300 MHz, d in and ATU in 1 : 1 : 2 ratio. Yield 70%, (M.P): 190 1C, analytical and
ppm CDCl3, at 25 1C): d 1.99 (s, 3H, CH3), d 7.18–7.48 (broad m, calculated for C24H27ICuN4O2PS2 (642.05): C, 41.83, H, 3.95, N,
30H, Ar-H), 9.80, (s, 2H, NH2 protons), 11.35 (s, 1H, NH proton), 8.13, S, 9.31, Cu, 9.22, found, C, 41.54, H, 3.71, N, 7.94, S, 8.96, Cu,
13C NMR (75 MHz, CDCl3, at 25 1C): d 24.64 (CH3 carbon), 9.01%. FT-IR, (ATR, u in cmꢀ1): 3242 (N–H), 3165 (aromatic N–H),
128.33 (d, 2J = 8.74 Hz, P–C coupling, Ar-C), 129.43, 133.57, 2940 (aliphatic C–H), 1709 (CQO), 1517 (CQC), 1432.2 (C–P),
133.96 (d, 1J = 14.45 Hz, P–C coupling, Ar-C), 172.58, 180.93, 1213.9 (CQS), 1094 (C–N), 745 (TPP). 1H NMR (300 MHz,
31P NMR (121.49 MHz, 83% aqueous H3PO4, d in ppm at 25 1C): (CD3)2SO, d in ppm at 25 1C): d 1.91 (s, 6H, CH3), 7.01–7.34 (broad
d ꢀ3.92.
m, 15H, Ar-H), 9.45 (s, 4H, NH2 proton), d 10.61 (s, 2H, NH protons),
Iodidoacetylthiourea-bis-(triphenylphosphine)copper(I) 13C NMR (75 MHz, (CD3)2SO, d in ppm at 25 1C): d 24.12, 127.88
[Cu(TPP)2(ATU)I] (A3). A3 was prepared from the reaction of (d, 2J = 8.25 Hz, P–C coupling of Ar-C), 127.84, 128.61, 129.66
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1
(d, J = 24.01 Hz P–C coupling, of Ar-C), 170.76, 177.15, 31P NMR (ATCC 43816), Pseudomonas aeruginosa (27853), Enterococcus
(121.49 MHz, 83% aqueous H3PO4, d in ppm at 25 1C): d ꢀ5.07.
faecalisis (ATCC 51299), and Bacillus subtilis (ATCC 60512).
Chloridotriacetylthioureacopper(I) [Cu(ATU)3Cl] (A7). A7 was Compound’s stock solution (3 mg/1 mL of DMSO) was
prepared from CuCl and ATU according to the above described prepared, while Ciprofloxacin (1 mg/1 mL of DMSO) was used
procedure. Yield 73%, (M.P): 200 1C, analytical and calculated as a positive control. Turbidity of the bacterial inoculum was
for C9H18ClCuN6O3S3 (453.46): C, 23.84, H, 4.00, N, 18.53, S, adjusted according to 0.5 McFarland (1% BaCl2 and 1% H2SO4).
21.21, Cu, 14.01, found, C, 23.56, H, 3.84, N, 18.39, S, 21.03, Cu, Sterilized filter paper discs of 6 mm diameter at an angle
13.89%. FT-IR, (ATR, u in cmꢀ1): 3296 (N–H), 3127 (aromatic of 901 were placed on bacterial lawns formed using sterilized
C–H), 1697.4 (CQO), 1537 (aromatic CQC), 1295 (CQS), 1039.2 cotton swabs. Finally, the compounds (5 mL of concentration
(C–N). 1H NMR (300 MHz, CDCl3, d in ppm at 25 1C): d 2.09 3 mg mLꢀ1), negative control (DMSO impregnated disc) and
(s, 9H, CH3), 9.62–9.81 (d, 6H, NH2 protons), 12.24 (s, 3H, NH positive control (5 mL of concentration 1 mg mLꢀ1) were applied
proton), 13C NMR (75 MHz, CDCl3, d in ppm, at 25 1C): d 24.41 on the labeled discs. The procedure was repeated in triplicate
(CH3, carbon), 172.42, 180.50.
Bromidotriacetylthioureacopper(I) [Cu(ATU)3Br] (A8). A8 was zones of inhibition (MZI) that was statistically examined.
prepared from the reaction of CuBr and ATU in 1 : 3 ratio. Yield Antifungal activity. Antifungal activity of the compounds
and the compound’s activity was measured by the mean of
69%, (M.P): 170 1C, analytical and calculated for C9H18BrCu- was tested against an aliquot of 100 mL spore suspension from
N6O3S3 (497.91): C, 21.71, H, 3.64, N, 16.88, S, 19.32, Cu, 12.76, each fungal strains: Aspergillus niger, Aspergillus fumigatus and
found, C, 21.12, H, 3.28, N, 16.31, S, 18.81, Cu, 12.19%. FT-IR, Aspergillus flavus.28 The spores harvested in 0.02% (v/v) Tween
(ATR, u in cmꢀ1): 3290 (N–H), 2940 (aliphatic C–H), 1672 20 solution were swabbed on sterile Petri Sabouraud Dextrose
(CQO), 1295 (CQS), 1091 (C–N), 1H NMR (300 MHz, CDCl3 Agar (SDA) plates. From each compound, a 5 mL (3 mg mLꢀ1
)
and (CD3)2SO, d in ppm at 25 1C): d 2.05 (s, 9H,CH3), 9.61 (s, 6H sample was applied on the sterile disc placed at an angle of 901.
NH2 protons), 11.74 (s, 3H, NH proton), 13C NMR (75 MHz, Clotrimazole (4 mg mLꢀ1) and DMSO impregnated discs were
CDCl3 and (CD3)2SO, d in ppm at 25 1C): d 29.01 (CH3, carbon), used as positive and negative controls, respectively. The proce-
177.00, 185.42.
dure was repeated in triplicate, while MZI produced by the
Iodidotriacetylthioureacopper(I) [Cu(ATU)3I] (A9). A9 was compounds were measured in mm.
prepared from the reaction of CuI and ATU in 1 : 3 ratio. Yield
68%, (M.P): 140 1C, analytical and calculated for C9H18ICu-
Antileishmanial assay
N6O3S3 (544.91): C, 19.84, H, 3.33, N, 15.42, S, 17.65, Cu, 11.66,
found, C, 19.49, H, 3.17, N, 15.24, S, 17.47, Cu, 11.47%. FT-IR,
(ATR, u in cmꢀ1): 3310 (N–H), 2968 (aliphatic C–H), 1693
(CQO), 1212 (CQS), 1040 (C–N). 1H NMR (300 MHz, in CD3CN
d in ppm at 25 1C): d 2.13 (s, 9H, CH3), 9.43 (s, 6H, NH2
protons), 12.68 (s with shoulder, 3H, NH protons), 13C NMR
(75 MHz, CDCl3 and (CD3)2SO d in ppm at 25 1C): d 23.60
(CH3, carbon), 171.86, 181.15.
A quantitative colorimetric assay using 3-(4,5-dimethylthiazol-2-yl)-2,
5-diphenyl tetrazolium bromide (MTT) was used to evaluate
the potency of the compounds (10 mL with a concentration of
3 mg mLꢀ1) against promastigotes of Leishmania tropica (seeding
density: 2 ꢁ 106 cells per mL).29,30 The parasite was cultured in
medium 199 at a temperature of 24 1C. DMSO with phosphate
buffer saline (PBS) was used as a negative control. A microplate
reader (MULTISKAN GO spectrophotometer, Thermo Fisher
Scientific, United States) was used to estimate the cell viability
at 540 nm.
Single crystal X-ray diffraction study
Suitable crystals of complexes A2 and A3 were analyzed on a
Bruker Smart diffractometer equipped with an Incoatec IMuS
source, a Quazar MX mirror and an APEX II CCD detector. The
distance of crystal-to-detector was 4.0 cm, and data were
collected in the 512 ꢁ 512 pixel mode. Suitable crystals of sizes
0.36 ꢁ 0.28 ꢁ 0.32 and 0.37 ꢁ 0.18 ꢁ 0.14 mm were then
mounted on the Bruker Smart APEX diffractometer. During
data collection, the crystals were kept at 296 K while Mo Ka
radiation with wavelength set to 0.71073 Å was used. With the
use of Olex2,25 the structure was solved with SHELXT,26 and
then refined with the XL27 refinement package using Least
Squares minimization. Hydrogen atoms were refined isotropi-
cally while the atoms other than hydrogen were refined using
anisotropic thermal parameters.
Antioxidant assay
Antioxidant activity of the compound was investigated using the
1,1-diphenyl-2-picrylhydrazyl (DPPH) assay.31–33 The optical density
of the DPPH solution (0.0024 g/100 mL methanol) was adjusted to
0.98 at 517 nm using a MULTISKAN GO spectrophotometer. An
ascorbic acid (Sigma-Aldrich, United States) solution was prepared
by dissolving 1 mg mLꢀ1 of DMSO and a standard curve was
calibrated that was used as the reference. Different volumes of the
test samples, i.e. 5, 10, 15 and 20 mL, were used and added to the
wells of 96 well plates. The wells were filled with DPPH, 200 mL
solution in each well. The plates were analyzed for absorbance (Abs)
at 517 nm after incubation in the dark for 5 min. Both a positive
control (ascorbic acid + DPPH) and a negative control (DPPH) were
used. The percent radical scavenging activity (% RSA) of the
compounds was calculated as,
Biological activity assays
In vitro antibacterial activity. Agar disc diffusion method28 on
Mueller Hinton Agar was performed against five ATCC bacterial
strains: Escherichia coli (ATCC 10536), Klebsiella pneumoniae
Abscontrol ꢀ Abssample
% RSA ¼
ꢁ 100
Abscontrol
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Cytotoxicity assay
Toxicity of synthesized complexes against brine shrimps was
evaluated following a protocol reported in literature.33,34 A perfo-
rated bi-compartment tank was filled with seawater and Artemia
salina eggs (1.5 g Lꢀ1) were added to it in an appropriate amount.
The tank was then incubated at 30 1C to allow the eggs to hatch. The
tank compartment containing the eggs was covered with aluminum
foil while the other compartment was left uncovered and placed
under a light source. Following two days of incubation, the shrimps
were collected from the uncovered compartment using a Pasteur
pipette and were transferred to sterilized test tubes containing
artificial seawater. The compounds as test samples were analyzed
Scheme 1 Reaction equations for the synthesis of precursor complexes
[Cu(TPP)3X] and final products A1–A3; reaction between [Cu(TPP)3X] and 2
or 3 mole equivalent ATU concentration yielded the single substitution
products A1–A3.
shown in reaction Scheme 1.23,24 The copper(I) complexes A1 to
A9 have been synthesized by the procedure elaborated in the
experimental section. The complexes A1–A3, where the phosphine
ligand was two-fold as compared to ATU, were synthesized by a
displacement reaction, in which thiourea substituted the phosphine
ligand. In the other trials, the mole ratio of ATU was increased by
two and three times for the reaction with [CuX(TPP)3] to
produce di and tri substituted products, but in all the trials
we got the same single substitution products, like A1–A3, as
described in reaction Scheme 1. However, the complexes A4 to
A9 were synthesized by the direct reaction between copper salts,
TPP and ATU in appropriate stoichiometry, as described in the
experimental section and Scheme 2.
at various concentrations, i.e. 100 mg mLꢀ1, 75 mg mLꢀ1
,
50 mg mLꢀ1, and 25 mg mLꢀ1. The tubes were then placed at
37 1C for 24 hours. Doxorubicin was used as a positive control, while
DMSO was used as a negative control. The number of dead shrimps
in each test tube was counted and compounds showing Z50%
mortality were analyzed for LC50 (50% lethal dose concentration)
using the Table Curve 2D v4 software. The percent of mortality was
calculated using the formula described below:
% Mortality = Number of dead shrimps/Total number of
shrimps ꢁ 100
Molecular docking studies
Molecular docking for the molecular structures of the synthesized
compounds into the catalytic cavities of Acinetobacter baumannii
MurF ligase35 and KdsB,36 Escherichia coli FabH,37 trypanothione
reductase (TR) of Leishmania infantum,38 and Bcl2 (an anti-apoptotic
protein)39 was performed through GOLD suit 5.2.40 All the men-
tioned enzymes are broad-spectrum and are highly selective and
specific targets; therefore, they were used as receptors in molecular
docking studies. The crystal structures of the receptor proteins
MurF, KdsB, FabH, TR and Bcl2 were retrieved from the protein
data bank (PDB) via pdb id of 4QDI, 4FCU, 1HNJ, and 202F,
respectively. The protein structures were assigned with Gasteiger
charges and minimized for 1500 rounds of steepest descent and
conjugate gradients with step size set 0.02 Å under Tripos Force
Field (TFF).41 All the compounds were drawn and minimized using
the MM2 force field of the ChemDraw office package.42 The binding
site for the compounds was defined in such a way that the residues
lying within 10 Å of the specified residues were also considered for
ligand binding. The active site information was gathered through a
literature search and Thr42:O coordinates for MurF, Asp236:OD1 for
KdsB and Asn274:N for FabH, His461:NE2 for TR, and Phe109:HE1
for Bcl2 were set as the points for the docking of the compounds.
Ten solutions for each ligand were sorted and only the best solution
based on the GOLD fitness score was characterized by binding
mode interactions. A positive control of penicillin G was used.
Solution phase characterization
In the solution phase, all the synthetic products (A1–A9) were
analyzed by multinuclear NMR spectroscopy. For the complexes
(A1–A6), 1H, 13C and 31P NMR spectra were recorded in deuterated
solvents, like CDCl3 and (CD3)2SO solution. In all the complexes,
singlet peaks in the range of d 1.91–2.14 were observed, which
were attributed to the CH3 protons of complexes A1–A9; mean-
1
while, the multiplets around d 7.06–7.53 ppm in their H NMR
spectra were assigned to the aromatic protons of the phenyl rings
present in TPP. In the 1H NMR spectra of the complexes, the
characteristic signal for the NH2 group appeared in the range of
d 9.45–9.88 ppm, while the small singlet peaks for NH protons
were observed in the range of d 10.61–12.68 ppm as compared to
the free ligand because the protons were involved in the intra-
molecular hydrogen bonding between the hydrogen of NH group
and the halide ions coordinated to the central metal atom.23,43,44
In some cases (for example A7 and A9), the broad signal for the
NH2 group split into a pair of signals due to the conventional
hydrogen bonding of type N–HꢂꢂꢂO. This kind of bonding was
observed in the solid structures of complexes A2 and A3 during
crystallographic studies (as shown in Fig. 1). This kind of
Results and discussions
Synthesis
Precursor copper(I) phosphine complexes [Cu(TPP)3X] were
synthesized by following the method reported in literature, as
Scheme 2 Reaction equations for the synthesis of Cu(I) complexes final
products A4–A9.
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Fig. 1 ORTEP diagrams of [CuBr(TPP)2ATU] (A2) and [CuI(TPP)2ATU] (A3); displacement ellipsoids are drawn at the 50% probability level.
hydrogen bonding has been reported in literature for other Cu(I) The bands in the range of 1221 to 1295 were observed in the
thiourea complexes.45
complexes A1–A9, which could be assigned to CQS. In the IR
In the 13C NMR spectra of complexes A1–A6, signals around spectra of the complexes, the CQS groups appeared at lower
d 126.81–129.33 and d 129.81–134.12 ppm were observed, which frequencies, which indicated that sulfur is involved in the
can be assigned to the aromatic carbons of the phenyl rings of coordination with Cu. The characteristic broad band in the
TPP, which gave a doublet due to C–P coupling; the J values range of 3213–3310 cmꢀ1 can be assigned to corresponding
indicate that there is more splitting for the carbon directly thiourea based N–H groups in the spectra of the copper
attached to the P atom and less splitting at the meta position, complexes. The broadening of this signal can be associated
as can be seen from 1J, 2J and 3J values, which can be assigned to with hydrogen bonding that was also observed in the crystallo-
the carbons at ipso, ortho and meta positions, respectively. The graphic studies. The characteristic aliphatic C–H stretching was
singlet peaks in the range of d 129.36–133.57 are also assigned to observed below 3000 cmꢀ1 in the spectra of all the complexes,
the aromatic carbons of TPP. The complexes A1–A9 showed which can be assigned to the C–H stretching of the CH3 group
signals in 13C NMR spectra in the regions of d 170.76–177.00 of acetylthiourea. In addition, bands around 1530, 1432, 1100
and d 177.61–185.42 ppm, which can be assigned to the CQO and 740 were observed for the TPP ligand in IR spectra. All the
and CQS carbon atoms, respectively. All the complexes (A1–A9) observed data are in close agreement with the literature
exhibited resonances for the aliphatic carbons in the range of d reported data for similar functionalities.33,46
23.60–29.01, which are assigned to methyl carbons. The 31P NMR
spectra of complexes A1–A6 gave the singlet peaks in the range of
X-ray crystallography
ꢀ3.13 to ꢀ5.22, which confirmed that the TPP ligand is coordi- Compounds A2 and A3 were crystallized from a methanol–
nated to the Cu(I) in a tetrahedral arrangement around the metal chloroform mixture (2–1 v/v) by slow evaporation and subjected
center in A1–A6. All the observed data are in close agreement with to single crystal X-ray analysis, as described in the experimental
the literature reported data for similar functionalities.44,46
section. Data obtained in this regard show that both the
compounds crystallized in a monoclinic crystal system with
the P21/n space group. Other crystallographic parameters for
Solid phase characterization
All the synthesized complexes were characterized in the solid both compounds have been detailed in Table 1.
phase by elemental analysis and FTIR spectroscopic techni- The ORTEP diagrams of complexes A2 and A3 are illustrated
ques; data of the analyses are reported in the experimental in Fig. 1, and selected bond lengths and bond angles are listed
section. Two complexes (A2 & A3) were also additionally char- in Table 2, while hydrogen bond lengths and angles for com-
acterized by single crystal X-ray diffraction analysis. The ele- plexes A2 and A3 are given in Table 3. The crystal packing
mental results indicate the high purity of all the complexes diagrams are presented in ESI,† as Fig. S1 and S2, which clearly
along with the verification of the metal ligand ratio as per the show that there are 4 molecules per unit cell. In the ORTEP
expected stoichiometry.
diagrams (Fig. 1) of monomeric complexes (A2 and A3), it is
clear that the Cu(I) ion has two TPP ligands, which are coordi-
nated through the phosphorus atom, as well as coordinated
FTIR
A medium intensity band for free ATU was observed in the bromide and iodide ions and an ATU ligand. The ATU ligand
range of 1200–1300 cmꢀ1 for the CQS stretching frequency. has N, O and sulfur as donor atoms, but in the current case, it is
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Table 1 Crystal structure data and refinement parameters for complex A2 and complex A3
Parameter
Complex A2
Complex A3
CCDC
1889116
C39H36BrCuN2OP2S
Colorless
786.15; 1608
Monoclinic
P21/n
14.782(5)
1889117
C39H36CuIN2OP2S
Colorless
833.14; 1680
Monoclinic
P21/n
Chemical formula
Crystal colour
Fw; F(000)
Crystal system
Space group
a (Å)
14.149(3)
b (Å)
c (Å)
13.220(3)
18.6700(8)
13.291(2)
20.563(5)
b (deg)
97.260(14)
4
3759.6(19)
1.389
100.843(12)
4
3798.0(13)
1.457
Z
V (Å3)
rcalcd (g cmꢀ3
)
m (mmꢀ1
)
1.817
1.559
Crystal size/mm3
0.36 ꢁ 0.28 ꢁ 0.32
0.37 ꢁ 0.18 ꢁ 0.14
4.452 to 55.662; 0.968
26493; 0.0371
8949 [Rint = 0.0671, RSigma = 0.0898]
8949/0/390
y range (deg); completeness
Unique reflections; Rint
Independent reflections
Data/restraints/parameters
Index ranges
Final R indexes [I Z 2s(I)]
Goodness of fit on F2
Largest diff peak and hole/e Åꢀ3
5.238–55.662; 0.958
25501; 0.0280
8784 [Rint = 0.0668, RSigma = 0.0973]
8784/0/425
ꢀ18 r h r 19, ꢀ16 r k r 15, ꢀ25 r l r 22
R1 = 0.0461, wR2 = 0.0842
0.959
ꢀ18 r h r 18, ꢀ16 r k r 17, ꢀ22 r l r 27
R1 = 0.0511, wR2 = 0.1026
0.992
0.40/ꢀ0.32
0.82/ꢀ0.61
Table 2 Selected important bond lengths and bond angles of complex A2 and complex A3
Complex A2
Complex A3
Bond lengths (Å)
Bond angles (1)
Bond lengths (Å)
Bond angles (1)
Br1–Cu1
Cu1–S1
Cu1–P1
Cu1–P2
S1–C1
2.5320(8)
2.4203(10)
2.2800(12)
2.3062(10)
1.682(4)
S1–Cu1–Br1
P1–Cu1–Br1
P1–Cu1–S1
P2–Cu1–Br1
P2–Cu1–S1
P2–Cu1–P1
C1–S1–Cu1
107.28(5)
108.96(5)
106.56(6)
104.10(5)
101.22(6)
127.24(6)
104.7(2)
I1–Cu1
Cu1–S1
Cu1–P2
Cu1–P1
S1–C37
2.6785(7)
2.4009(14)
2.2893(13)
2.3058(14)
1.684(5)
S1–Cu1–I1
P2–Cu1–I1
P2–Cu1–S1
P2–Cu1–P1
P1–Cu1–I1
P1–Cu1–S1
C37–S1–Cu1
111.25(4)
105.34(3)
98.33(5)
125.40(5)
107.53(4)
108.51(5)
108.05(18)
Table 3 Hydrogen bonding parameters in complexes A2 and A3, with
H-bond donor atom (D) and H-bond acceptor (A); d stands for distance
To further understand the geometric configuration around
the central metal atom, a structural parameter (t4) was calcu-
lated for complexes A2 and A3 in accordance with literature.47
The values of t4 were found as 0.2804 and 0.2242 for A2 and A3,
respectively. It has been established in literature that the value
of t4 is one for perfect square planar geometry and that is zero
for perfect tetrahedral geometry around the central metal
atom.47 In our case, the values of t4 (0.2804 and 0.2242)
confirm that A2 and A3 have a distorted tetrahedral arrange-
ment around the cuprous atom. The distortion may also occur
due to the intramolecular hydrogen bond between the hydro-
gen of thiourea N–H group and the halide ion coordinated to
the central metal atom. The Cu–S bond length of 2.3875(15) Å
in complex A2 is comparable to that (2.2668–2.4226 Å) of tetra-
Complex A2
D
H
A
d(D–H)/Å d(H–A)/Å d(D–A)/Å Angle D–H–A/1
N2 H2
N1 H1A O1
Br1 0.90(5)
2.47(5)
2.02(7)
3.346(5)
2.649(8)
165(4)
130(6)
0.86(7)
Complex A3
D
H
A
d(D–H)/Å
d(H–A)/Å
d(D–A)/Å
D–H–A/1
N2
N1
N1
H2
H1A
H1B
I1
O1
I11
1.09(6)
1.00(7)
0.87(5)
2.53(6)
1.92(7)
2.87(6)
3.612(5)
2.665(8)
3.693(7)
173(4)
129(5)
161(4)
coordinated through the sulfur atom. The bond angles in the hedral complexes consisting of monodentate acetylthiourea
four coordinated molecules around the central copper ion are ligands having Cu(I) as the central atom.48 The Cu1–Br1 bond
in the range of 101.22(5)–127.24(6) and 99.68(6)–123.32(7), length [2.5273(9) Å] in complex A2 and the I1–Cu1 bond length
respectively. The bond angles in complex A2 are mostly away 2.6666(9) in complex A3 were not equal to the sums of the total
from those of an ideal tetrahedral geometry, having a narrow ionic radii of Cu+ and Brꢀ ions (2.69 Å) and Cu+ and Iꢀ (2.93 Å),
101.22(6) for P2–Cu1–S1 to a wide 127.24(6) for P2–Cu1–P1, and indicating the covalent bonding character.49
for complex A3, a narrow 99.68(6) for P2–Cu1–S1 to a wide
Accordingly, all analytical, spectral and elemental studies
123.32(7) for P2–Cu1–P1, most probably due to the presence showed that all the complexes (A1–A9) have distorted tetra-
of two bulky groups, like TPP in the coordination sphere. hedral geometries. This has been confirmed by single crystal
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Fig. 2 Mean zone of inhibition (measured in millimeters – mm) of compounds A1–A9 (5 mL with the concentration of 3 mg mLꢀ1) against different ATCC
bacterial strains.
analysis for complexes A2 and A3, in which the copper center and Aspergillus flavus (AL). Results suggested that all of them
was occupied by two TPP groups, one halogen and one ATU. In have a significant activity, as shown in Fig. 3. Compounds A4,
all these complexes, ATU ligand, which is coordinated with the A5 and A6 were revealed to have the highest antifungal activity
Cu+ ion through the sulfur atom, shows a neutral and a when compared with the control Clotrimazole drug. Com-
monodentate behavior.
pounds A4 and A5 were most active against A. flavus with an
MZI of 20 mm each. Compound A6 was found to be the most
active against A. fumigatus with an MZI of 22 mm. The possible
Biological studies
After the successful synthesis and characterization, these com- reason for the high activity of these two compounds, which
plexes (A1–A9) were subjected to different biological assays to makes them more potent, is that they have one phosphine
explore their medicinal potential. Antibacterial, antifungal, group and two thioureas along with Cl and Br. The data
antileishmanial, and antioxidant properties as well as brine revealed that chloro compounds are more active than the
shrimp cytotoxicity behavior were tested for these compounds bromo ones and bromo compounds are more active than the
and the effect of the phosphine attachment in Cu–thiourea iodo derivatives. The order of the antifungal potency of all
complexes has been explored.
compounds was as follows: A6 4 A4 4 A5 4 A9 4 A7 4 A8 4
Antibacterial activity. The biological potency of the com- A3 4A1 4 A2; this order of reactivity is based on the average of
pounds against five ATCC bacterial strains, Escherichia coli results against different tested strains.
(EC) (ATCC 10536), Klebsiella Pneumoniae (PN) (ATCC 43816),
Antileishmanial activity. The potential of all the synthesized
Pseudomonas Aeruginosa (PA) (27853), Enterococcus Faecalisis complexes to act as an antileishmanial agent was evaluated
(EF) (ATCC 51299), and Bacillus Subtilis (BS) (ATCC 60512) against Leishmania tropica KWH23 strain promastigotes and the
was tested according to the procedure illustrated in the experi- results are illustrated in Fig. 4 as the fifty percent inhibitory
mental section. For comparative analysis, a reference drug, concentration (IC50). All the compounds were revealed to be
Ciprofloxacin was used, and the results are presented as mean highly potent. Compound A5 was found to be the most potent
zone of inhibition in mm as shown in Fig. 2. Compound A7 was with an IC50 value of 0.22 mg mLꢀ1. Potency of the compounds
found to be the most potent, while compound A5 was the least was observed in the following order: A5 4 A6 = A4 4 A8 4
potent against the tested strains compared to the reference. A9 4 A3 4 A2 4 A7 4 A1.
Compound A1 was found to be inactive in all these tests.
DPPH antioxidant assay. All the compounds were observed
Compared to the positive control, compound A7 was found to to have a significant antioxidant activity when compared to the
have a significant potency against B. subtilis and E. faecalisis reference ascorbic acid solution standard, as illustrated in
by producing MZI of 16.6 mm and 14.6 mm, respectively. Fig. 4. The percent free radical scavenging activity (% FRSA)
Compound A6 was the second most potent, especially against was examined for all compounds based on the discoloration
E. faecalisis by producing an MZI of 15.6 mm, which was higher of the purple colored DDPH solution. IC50 values were calcu-
than that produced by the positive control (MZI of 8.6 mm). lated using a regression curve with logarithmic fit. The
The antibacterial potency of the compounds was in the following results are shown as logarithm of IC50 (ng Lꢀ1 unit) values.
order: A7 4 A6 4 A9 4 A8 4 A4 4 A3 4 A2 4 A5; this order of The results showed that all the compounds have a good free
reactivity is based on the average of results against different radical scavenging activity. Compound A5 was found as the
tested strains.
most active agent to capture the free radicals with the lowest
Antifungal assay. All the compounds were screened against three value of IC50. The activity of all the compounds varies at a
fungal strains Aspergillus niger (AN), Aspergillus fumigatus (AF) logarithmic scale. The compounds’ potency was observed in
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Fig. 3 Mean zone of inhibition (measured in millimeters – mm) of compounds A1–A9 (5 mL with the concentration of 3 mg mLꢀ1) against three fungal
strains.
Fig. 4 Antileishmanial (left) and antioxidant (right) activity plots for compounds A1–A9.
the following order: A5 4 A4 4 A8 4 A6 4 A3 4 A9 4 A1 4 concentration of the compounds is directly proportional to
A2 4 A7.
the mortality rate of the shrimps. All the compounds were
Brine shrimp cytotoxicity. The brine shrimp cytotoxicity of observed to show high toxic activities with compound A8 being
all the synthesized compounds was evaluated in accordance the most potent having a LC50 value of 17.8 mg mLꢀ1, followed
with a literature reported method33,34 and the results are by compounds A2, A6 and A9, which all had a cytotoxicity
presented in Fig. 5 as LC50 values. In general, the findings of potency LC50 value of 20.83 mg mLꢀ1
.
the cytotoxic activity indicate that the increase in the
Molecular docking. A coherence docking activity with the
antibacterial activity was found. Compounds A4 and A6 were
identified as the best-fit compounds in the receptor active
pockets. The GOLD fitness scores of the compounds can
be seen in Table 4. When the antibacterial activities were
compared, both the compounds were found to have better
antibacterial activity, similar to the results reported by the
docking studies.
The binding interactions of both compounds in different
receptor cavities can be observed in Fig. 6 (for compound A4 in
the active site of protein Bcl2) and Fig. S3 and S4 in ESI,† for
other represented compounds, respectively. It was observed
that the major contribution towards both compounds’ activity
came from N-carbamathioylacetamide rings. Both these rings
were observed in hydrogen and hydrophobic interactions with
the enzyme active site residues. The compounds were found to
Fig. 5 Cytotoxic activity plots (as LC50 values) for compounds (A1–A9).
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Table 4 Docking scores of the compounds
Conclusion
GOLD fitness score
The preparation of CuCl, CuBr, and CuI, complexes with ATU
and TPP ligands has produced a variety of product stoichiome-
tries and structural types, giving monomeric species. This
indicates that the presence of the TPP ligand in the coordina-
tion environment of Cu(I) hinders the bi-substitution of the
incoming ATU ligand. The synthesized copper(I) complexes
have been characterized with four coordination number and
tetrahedral geometries. The important features of complexes
A1–A6 in the presence of TPP bulky groups and the complexes
A7–A9 having three ATU ligands are very simple. The synthesized
complexes were subjected to different biological activities. The
results of all the biological studies have been compared with those
of some literature reported similar compounds and data are
presented in Table 5. Comparative data conclude that compounds
reported in this work generally have a lower activity than the
literature reported compounds in antibacterial assays. However,
compounds A1 to A9 are more active than the literature reported
ones in all other performed bioassays. Biological activities
revealed that compounds A4 and A6 are the most active molecules
against bacteria, fungi, and the lieshmanial pathogen, in addition
to having an excellent antioxidant activity. Molecular docking
study revealed that the major activity of both compounds is due
to N-carbamathioylacetamide rings. Both these rings are involved
in hydrogen and hydrophobic interactions with the enzyme active
site residues. It further confirms that the presence of mix ligands
in these compounds played an important role for the biological
Compound
MurF
KdsB
FabH
TR
Bcl2
A1
A2
A3
A4
A5
A6
A7
A8
46.10
40.93
45.07
58.16
46.19
59.64
48.40
47.49
46.91
32.12
59.65
59.98
56.33
54.71
53.08
56.35
48.45
53.42
50.66
42.31
54.56
35.95
45.65
37.84
24.61
57.66
38.99
51.94
46.38
44.32
58.42
50.37
55.80
51.44
50.20
51.29
46.42
43.49
51.51
43.21
45.47
49.35
43.42
65.07
53.58
63.39
47.78
56.84
51.06
49.31
A9
Control
be intensely bound, which was mainly driven by the (triphenyl-
phosphoranyl)copper(I)iodide component of the compounds.
Similarly, the compounds interact with the key residues of the
enzymes involved in ligand binding and catalysis. In the case of
MurF, both compounds interact with Ile32, Thr34, Ser36, and
Arg37, which are the key residues of the MurF active pocket.
Similarly, in the case of KdsB, both compounds closely interact
with Arg9, Ser11, and Lys18. For FabH, Gly152, Met207, and
Asn247 were found in the interactions with the ligands. Similar
to the case of the TR enzyme, the compounds interact with
similar residues of the pocket, i.e. Leu399, His461, Thr463,
Ser464, Glu466, Glu467, Ser470, and Pro462. In the case of Bcl2,
the common interacting residues were Phe38, Tyr42, Asp45,
Phe46, Glu48, Met49, Gln52, Val67, Glu70, Arg80, and Ala83.
Fig. 6 Molecular docking interaction plot of A4 in the active site of protein Bcl2 (representative image). Green dash line indicates the conventional
hydrogen bonding.
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Paper
Table 5 Comparison of biological activity data with some previously reported data for45,50 similar copper(I) compounds; structures of compounds X1 to
X9 have been provided in ESI (Chart X)
Antifungal activity
Antibacterial activity
(mean zone of inhibition in mm) (mean zone of inhibition in mm)
Cytotoxicity
Antioxidant activity Antileishmanial activity
Comp. code (LC50 in mg mLꢀ1) (IC50 in mg Lꢀ1
)
(IC50 in mg mLꢀ1
)
AN
AF
AL
EC
PN
0
7.3
7.6
PA
EF
BS
A1
A2
A3
A4
A5
A6
A7
A8
62.5
20.8
27.8
35.7
45.5
20.8
62.5
17.8
20.8
110.6
1.87
2.86
8.15
0.10
0.71
0.10
0.01
0.17
1.24
1.78
0.82
0.81
0.23
0.22
0.23
1.2
0.66
0.69
11
12
13
19
18
19
14
13
14
13
11
12
19
18
22
12
14
15
12
12
13
20
20
20
15
13
16
0
0
0
0
0
4.6
3.6
0
4.6
0
0
10
0
0
0
8
15
8.3
0
0
7.6
0
0
16
17
0
7.3 11
0
4.6
7.6
11
10
0
9.6
8.6
0
0
A9
11
8.6 16
0
X150
X250
X350
X450
X550
X645
X745
X845
X945
110
34.89
21.25
450
32.25
4 50
7.5
4200
200
131
150
139
7.5
7.5
7.5
0
94.9
90.26
120.9
20
15
17
12
20
14
12
13
10
14
18
10
7 A. Binolfi, L. Quintanar, C. W. Bertoncini, C. Griesinger and
activities. Thus, the structure of both these compounds can serve
as an excellent parent structure for future lead optimization.
´
C. O. Fernandez, Bioinorganic chemistry of copper coordi-
nation to alpha-synuclein: Relevance to Parkinson’s disease,
Coord. Chem. Rev., 2012, 256, 2188.
Conflicts of interest
8 J.-P. Zhang, Y.-Y. Lin, X.-C. Huang and X.-M. Chen, Copper(I)
1,2,4-triazolates and related complexes: studies of the sol-
vothermal ligand reactions, network topologies, and photo-
luminescence properties, J. Am. Chem. Soc., 2005, 127, 5495.
9 A. A. Isab, S. Nawaz, M. Saleem, M. Altaf, M. Monim-ul-
Mehboob, S. Ahmad and H. S. Evans, Synthesis, characteriza-
tion and antimicrobial studies of mixed ligand silver(I)
complexes of thioureas and triphenylphosphine; crystal structure
of {[Ag(PPh3)(thiourea)(NO3)]2ꢂ[Ag(PPh3)(thiourea)]2(NO3)2},
Polyhedron, 2010, 29, 1251.
There are no conflicts to declare.
Acknowledgements
Syed Ishtiaq Khan is highly thankful to Higher Education
Commission of Pakistan for financial support during IRSIP
scholarship to carry out this work. Sajjad Ahmad and Sikander
Azam are highly grateful to the Pakistan-United States Science and
Technology Cooperation Program (Grant No. Pak-US/2017/360) for
granting the financial assistance.
´
10 A. Nimthong-Roldan, J. Ratthiwal and Y. Wattanakanjana,
Crystal structure of bis [m-bis (diphenylphosphanyl) methane-
k2P: P0]-m-chlorido-chlorido-1kCl-(1-phenylthiourea-2kS) disilver
acetonitrile hemisolvate, Acta Crystallogr., Sect. E: Crystallogr.
Commun., 2015, 71, m133.
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