Coordination variability of CuI in multidonor heterocyclic thioamides: Synthesis, crystal structures, luminescent properties and ESI-mass studies of complexes

Article abstract of DOI:10.1039/c4ra02748e

The chemistry of copper(i) with scarcely investigated heterocyclic thioamides, particularly 2,4,6-trimercaptotriazine, purine-6-thione, 2,4-dithiouracil, 2-thiouracil and pyrimidine-2-thione is described. The interaction of 2,4,6-trimercaptotriazine (tmtH₃) with [Cu(CH ₃COO)(PPh₃)₂] resulted in a pair of bond isomers: [Cu(κ¹N-tmtH₂)(PPh₃) ₂] (6a), [Cu(κ¹N,κ¹S-tmtH ₂)(PPh₃)₂] (6b); with copper(i) bromide and PPh₃, it formed a trinuclear complex, [Cu₃Br ₂(κ¹N,κ¹S, μ-S-tmtH ₂)(PPh₃)₆] (7) with anionic tmtH ₂^-. The 2,4-dithiouracil with copper(i) halides (CuCl, CuBr) and PPh₃ yielded dinuclear complexes: [Cu₂(μ-Cl) (κ¹S,κ¹S-dtucH)(PPh₃)₄] (4) and [Cu₂(μ-Br)(κ¹S,κ¹S- dtucH)(PPh₃)₄] (5) with unusual eight-membered metallacyclic rings. Pyrimidine-2-thione (pymSH) is an N,S-chelated anion in a mononuclear complex, [Cu(κ¹N,κ¹S-pymS) (PPh₃)₂] (1), whereas 2-thiouracil (tucH₂) with copper(i) chloride and PPh₃ yielded a tetrahedral complex, [CuCl(κ¹S-tucH₂)(PPh₃)₂] (3). Purine-6-thione (purSH₂) coordinated to Cu^I in two different modes yielding mono- and di-nuclear complexes, [Cu(κ ¹N,κ¹S-purS)(PPh₃)₂] ·CH₃OH (2a) and [Cu₂(κ¹N,μ-S- purS)₂(PPh₃)₂] (2b). The existence of bond isomers (6a and 6b), synthesis of novel dinuclear (4 and 5) and rare trinuclear (7) complexes with unusual bonding patterns are the novel features of the present study. Complexes show intense emission bands in the 380-530 nm region with λ_em at 490 to 495 nm.

Full text of DOI:10.1039/c4ra02748e

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Coordination variability of CuI in multidonor
heterocyclic thioamides: synthesis, crystal
Cite this: RSC Adv., 2014, 4, 30511
structures, luminescent properties and ESI-mass
studies of complexes†
a
Tarlok S. Lobana, Amanpreet K. Sandhu,a Razia Sultana,a Alfonso Castineiras,b
*
Ray J. Butcherc and Jerry P. Jasinskid
The chemistry of copper(I) with scarcely investigated heterocyclic thioamides, particularly 2,4,6-
trimercaptotriazine, purine-6-thione, 2,4-dithiouracil, 2-thiouracil and pyrimidine-2-thione is described.
The interaction of 2,4,6-trimercaptotriazine (tmtH3) with [Cu(CH3COO)(PPh3)2] resulted in a pair of bond
isomers: [Cu(k1N-tmtH2)(PPh3)2] (6a), [Cu(k1N,k1S-tmtH2)(PPh3)2] (6b); with copper(I) bromide and PPh3, it
formed a trinuclear complex, [Cu3Br2(k1N,k1S, m-S-tmtH2)(PPh3)6] (7) with anionic tmtH2ꢀ. The 2,4-
dithiouracil with copper(I) halides (CuCl, CuBr) and PPh3 yielded dinuclear complexes: [Cu2(m-Cl)(k1S,k1S-
dtucH)(PPh3)4] (4) and [Cu2(m-Br)(k1S,k1S-dtucH)(PPh3)4] (5) with unusual eight-membered metallacyclic
rings. Pyrimidine-2-thione (pymSH) is an N,S-chelated anion in a mononuclear complex, [Cu(k1N,k1S-
pymS)(PPh3)2] (1), whereas 2-thiouracil (tucH2) with copper(I) chloride and PPh3 yielded a tetrahedral
complex, [CuCl(k1S-tucH2)(PPh3)2] (3). Purine-6-thione (purSH2) coordinated to CuI in two different
modes yielding mono- and di-nuclear complexes, [Cu(k1N,k1S-purS)(PPh3)2]$CH3OH (2a) and
[Cu2(k1N,m-S-purS)2(PPh3)2] (2b). The existence of bond isomers (6a and 6b), synthesis of novel dinuclear
(4 and 5) and rare trinuclear (7) complexes with unusual bonding patterns are the novel features of the
present study. Complexes show intense emission bands in the 380–530 nm region with lem at 490 to
495 nm.
Received 28th March 2014
Accepted 20th June 2014
DOI: 10.1039/c4ra02748e
www.rsc.org/advances
guanidines,32 phenanthroline33 and quinolin-2(1H)-one-derived
Schiff bases34 have shown anticancer, antitumor, antifungal,
Introduction
antimicrobial and antibacterial properties.
The coordination chemistry of heterocyclic thioamides with
transition/main-group metals has been the focus of numerous
studies, particularly with pyridine-2-thiones, imidazolidine-2-
thiones, thiazolidine-2-thiones and a few other allied bases.
These studies deal with the synthesis and structures of a variety
of compounds, as well as their biochemical and other applica-
tions.1–29 Among applications, copper complexes have shown
antitumor, anti-inammatory and antimicrobial proper-
ties.2,16–18 There is keen interest in the chemistry of Cu(I)/Cu(II)
with analogous N-based ligands because their complexes with 6-
(2-chlorobenzylamino)purine,30 2,20-biquinolines,31 substituted
Considering the importance of copper complexes with N/S
donor ligands, it was decided to pursue copper chemistry with
multifunctional heterocyclic thioamides, as shown in Scheme
1, having the propensity to bind to more than one metal ion.
Coordination chemistry of copper(I) with pyrimidine-2-thi-
one,8–13,35 purine-6-thione,36–38 2-thiouracil,39 2,4-dithiouracil40,41
and 2,4,6-trimercaptotriazine is limited.35,42,43 Herein, it is
planned to react copper(I) salts with multifunctional hetero-
cyclic thioamides (Scheme 1) with the objective of obtaining
mono-, di- and polynuclear copper complexes by changing the
number of donor atoms in organic thiobases. In the prepara-
tion of complexes, the reactions of pyrimidine-2-thione
(pymSH, I), purine-6-thione (purSH2, II), 2,4,6-trimercapto-
triazine (tmtH3, III), 2-thiouracil (tucH2, IV) and 2,4-dithiour-
acil (dtucH2, V) (Scheme 1) were carried out with copper(I)
halides/Cu(CH3COO)(PPh3)2. The resulting isolated mono-, di-
and trinuclear complexes isolated were characterized using
analytical data, spectroscopy, ESI-MS spectrometry and X-ray
crystallography.
aDepartment of Chemistry, Guru Nanak Dev University, Amritsar – 143 005, India.
E-mail: tarlokslobana@yahoo.co.in; Fax: +91-183-2258820
bDepartamento de Quimica Inorganica, Facultad de Farmacia, Universidad de
Santiago, 15782-Santiago, Spain
cDepartment of Chemistry, Howard University, Washington DC, 20059, USA
dDepartment of Chemistry, Keene State College, Keene NH 03435-2001, USA
† Electronic supplementary information (ESI) available: CCDC reference numbers
976978 (1), 976979 (2a), 976980 (2b), 976981 (3), 976982 (4), 976983 (5), 976984 (6)
and 976985 (7). For ESI and crystallographic data in CIF or other electronic format
see DOI: 10.1039/c4ra02748e
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thione (purSH2) with [Cu(CH3COO)(PPh3)2], the acetate
removed one proton from an –NH– group.
The anionic purSHꢀ coordinated to CuI in two different
modes yielding mono- and di-nuclear complexes, [Cu(k1N,
k1S-purS)(PPh3)2]$CH3OH (2a) and [Cu2(k1N,m-S-purS)2(PPh3)2]
(2b) from the same reaction. The crystals of 2a and 2b were
manually separated. The interaction of tmtH3 with [Cu(CH3-
COO)(PPh3)2] resulted in a pair of bond isomers: [Cu(k1N-
tmtH2)(PPh3)2] (6a) and [Cu(k1N,k1S-tmtH2)(PPh3)2] (6b) in the
same unit cell (X-ray crystallography, vide infra). The reaction of
tmtH3 with copper(I) bromide in the presence of two moles of
PPh3 involved the removal of one –NH– hydrogen and unin-
egative tmtH2ꢀ, yielding a trinuclear complex, [Cu3Br2(k1N,k1S,
m-S-tmtH2)(PPh3)6] (7). The reaction of 2-thiouracil with cop-
per(I) chloride in the presence of two moles of PPh3 yielded
Scheme 1 Molecular structures of thiol ligands under study.
light yellow crystals of
a mononuclear complex, [CuCl
(k1S-tucH2)(PPh3)2] (3). The reaction of 2,4-dithiouracil with
copper halides (CuCl, CuBr) in the presence of two moles of PPh3
also removed one –NH– hydrogen and reacted with two CuX units
yielding yellow complexes, [Cu2(m-Cl)(k1S,k1S-dtucH)(PPh3)4] (4)
and [Cu2(m-Br)(k1S,k1S-dtucH)(PPh3)4] (5) with unusual bonding
patterns. All the complexes except 2b were soluble in organic
solvents such as chloroform and dichloromethane.
The IR spectral data of complexes is given in the Experi-
mental section and that of the ligands is provided in the ESI.†
The n(N–H) band of the free pyrimidine-2-thione ligand at 3078
cmꢀ1 disappeared in complex 1. Similarly, the diagnostic n(C–S)
band at 1187 cmꢀ1 shied to 1026 cmꢀ1 in the complex, which
revealed that the thio-ligand is coordinating as anion through
its N and S donors. The n(N–H) bands in complexes 2–7 occur in
the region 3082–3250 cmꢀ1, which are at different positions
from those of the thio-ligands. In complex 3, the n(O–H) band is
assigned to 3447 cmꢀ1. In complexes 2–7, the n(C–S) bands are
assigned in the region 844–1184 cmꢀ1, which are generally at
low-energy regions relative to the respective free thio-ligand.
The n(P–CPh) bands in the region of 1094 to 1091 cmꢀ1 indicated
the presence of PPh3 in the complexes.
Results and discussion
Synthesis and IR spectroscopy
Scheme
2 shows a bonding pattern of the synthesized
complexes. In the synthesis of complexes 1, 2 and 6, no reux-
ing was carried out because high temperature led to the
formation of a solid which could not be crystallized, and thus
the reaction mixture was kept undisturbed at room tempera-
ture. For the synthesis of complexes 3, 4, 5 and 7, a copper(I)
halide was rst reacted with a thio-ligand under magnetic stir-
ring at room temperature, followed by the addition of PPh3.
Slow evaporation of the resulting solution gave pale yellow (3),
light orange (4, 5) or yellow (7) crystals. The reaction of pyrim-
idine-2-thione (pymSH) with [Cu(CH3COO)(PPh3)2] involved the
removal of the N–H proton and the anionic pymSꢀ chelated to
the {Cu(PPh3)2} moiety yielding the complex, [Cu(k1N,
k1S-pymS)(PPh3)2] (1). Similarly, in the reaction of purine-6-
Molecular structures
The crystal data of complexes are given in Table 1, and their
important bond parameters are given in Table 2. Complexes 1,
2b, 3–5 and 7 crystallized in the triclinic crystal system with the
ꢀ
space group P1, whereas other complexes (2a, 6) crystallized in
the monoclinic crystal system with the space groups P21/n (2a)
and P21(6).
Mononuclear complexes
The pyrimidine-2-thiolate chelates to the copper atom in
complex 1 through its N1, S– donor atoms with the N–Cu–S bite
angle of 69.10(6)ꢁ being the shortest, whereas the P–Cu–P angle
{126.25(3)ꢁ} is the largest among the various angles around the
Cu atom (Fig. 1). Purine-6-thiolate also chelates to the copper
atom in 2a through its N7, S– donor atoms with the N–Cu–S bite
angle of 88.24(5)ꢁ being the shortest, whereas the P–Cu–P angle
{126.081(19)ꢁ} is the largest among angles around the Cu atom
(Fig. 2). The geometry is severely distorted from the tetrahedron
Scheme 2 A view of bonding pattern of complexes synthesized.
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Table 1 Crystal data for complexes 1–7
1
2a
2b
3
Empirical formula
M
T/K
C
40H33N2CuP2S
C42H37N4OCuP2S
771.30
173(2)
C46H36N8Cu2P2S2
953.97
295(2)
C40H34ClCuN2OP2S
751.68
170(2)
699.24
296(2)
Crystal system
Space group
Triclinic
P1
Monoclinic
P21/n
9.0783(2)
25.2036(6)
16.9815(5)
—
102.171(3)
—
3798.13(17)
4
Triclinic
P1
Triclinic
P1
ꢀ
ꢀ
ꢀ
˚
a(A)
9.349(3)
11.140(4)
18.860(6)
93.050(13)
92.208(12)
113.907(11)
1789.2(10)
2
12.6132(6)
12.6674(6)
17.0373(7)
88.319(3)
69.754(4)
65.581(4)
2304.8(2)
2
10.8164(9)
13.1393(10)
14.7805(10)
76.189(6)
81.704(6)
67.452(7)
1880.7(2)
2
˚
b(A)
˚
c(A)
a (ꢁ)
b (ꢁ)
g (ꢁ)
3
˚
V(A )
Z
Dcalcd (g cmꢀ3
)
1.298
0.788
724
1.349
0.753
1600
1.375
2.966
976
1.327
0.826
776
m (mmꢀ1
F(000)
)
Reections collected
Unique reections
Data/restraints/parameters
Reens. With [I > 2s(I)]
19105
39221
17070
19880
7179 (Rint,0.0292)
7179/0/416
5988
9794 (Rint,0.0222)
9794/2/466
8534
9009 (Rint,0.0388)
9009/0/544
6944
9706 (Rint,0.0205)
9706/2/439
7531
R Indices [I > 2s(I)]
R1
WR2
0.0340
0.0837
0.0395
0.1027
0.0556
0.1583
0.0433
0.0960
R Indices (all data)
R1
WR2
0.0470
0.1031
0.453 and ꢀ0.412 e A
0.0481
0.1095
0.360 and ꢀ0.219 e A
0.0715
0.1757
0.763 and ꢀ0.355 e A
0.0660
0.1122
0.546 and ꢀ0.381 e A
ꢀ3
ꢀ3
ꢀ3
ꢀ3
˚
˚
˚
˚
Largest diff. Peak and hole
4
5
6
7
Empirical formula
M
T/K
C
76H63ClCu2N2P4S2
C76H63BrCu2N2P4S2
1399.27
123(2)
C39H33N3O0.50CuP2S3
773.34
100 (2)
C111H92Br2Cu3N3P6S3
2100.32
173(2)
1354.81
173(2)
Crystal system
Space group
Triclinic
P1
Triclinic
P1
Monoclinic
P21
12.864(4)
16.167(5)
17.506(5)
—
95.271(4)
—
3625.4(19)
4
Triclinic
P1
ꢀ
ꢀ
ꢀ
˚
a(A)
17.6065(5)
18.9904(6)
22.8262(7)
66.994(3)
69.512(3)
81.169(3)
6579.4(3)
4
17.5439(3)
18.7998(3)
22.7125(4)
67.538(2)
69.421(2)
80.7420(10)
6477.95(19)
4
12.8825(5)
13.2054(5)
33.4043(1)
93.2233(3)
96.511(3)
119.084(4)
4893.4(3)
2
˚
b(A)
˚
c(A)
a (ꢁ)
b (ꢁ)
g (ꢁ)
3
˚
V(A )
Z
Dcalcd (g cmꢀ3
)
1.368
0.893
2800
1.435
1.483
2872
1.417
0.898
1596
1.425
1.675
2148
m (mmꢀ1
F(000)
)
Reections collected
Unique reections
Data/restraints/parameters
Reens. With [I > 2s(I)]
77752
134549
42507
50419
31317 (Rint,0.0475)
31317/2/1573
19640
65025 (Rint,0.0641)
65025/0/1573
37449
14793 (Rint,0.0473)
14793/1/875
12435
23304 (Rint,0.0341)
23304/4/1124
17703
R Indices [I > 2s(I)]
R1
WR2
0.0542
0.1041
0.0683
0.1416
0.0495
0.1121
0.0679
0.1345
R Indices (all data)
R1
WR2
0.1037
0.1234
0.849 and ꢀ0.497 e A
0.1342
0.1722
1.480 and ꢀ2.228 e A
0.0675
0.1215
1.012 and ꢀ0.904 e A
0.0932
0.1475
1.529 and ꢀ1.227 e A
ꢀ3
ꢀ3
ꢀ3
ꢀ3
˚
˚
˚
˚
Largest diff. Peak and hole
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Table 2 Important bond lengths(A˚) and bond angles(ꢁ)b
Mono-nuclear complexes (1, 2a, 3, 6a, 6b)
1
2a
3
6aa
6ba
Cu–N
Cu–S
Cu–P
2.144(2)
2.419(1)
2.262(1), 2.251(1)
1.711(3)
69.10(6)
2.130(2)
2.433(1)
2.262(1), 2.277(1)
1.715(2)
88.24(5)
—
2.015(4)
2.008(4)
2.381(1)
2.281(1), 2.256(1)
1.666(2)
—
124.53(3)
106.18(8)
3.144(2) (Cu2–S22)
2.249(1), 2.273(1)
1.680(5), 1.680(5), 1.652(5)
56.14(12)
125.88(5)
—
2.879(2) (Cu1–S12)
2.220(1), 2.254(1)
1.681(5), 1.664(5), 1.663(5)
61.59(12)
120.03(5)
69.40(17)
S–C
N–Cu–S
P–Cu–P
Cu–S–C
126.25(3)
78.98(9)
126.08(2)
93.60(7)
Dinuclear complexes (2b, 4 and 5)
2b
Molecule 1
Molecule 2
Molecule 1
Molecule 2
Cu–N
Cu–S
Cu–P
Cu–Cu
S–C
2.036(3)
2.362(1), 2.608(1)
2.223(1)
2.880(1)
1.710(3)
2.058(3)
2.345(1), 2.535(1)
2.215(1)
2.717(1)
1.739(3)
N–Cu–S
Cu–S–Cu, Cu–S–C
S–Cu–S
N–Cu–P
P–Cu–S
85.85(8), 101.43(8)
70.60(3), 89.85(13)
109.40(3)
127.62(8)
103.35(3), 122.19(4)
87.66(9), 105.87(11)
67.52(4), 90.88(12)
112.48(4)
117.64(11)
110.98(5), 118.24(4)
4
Molecule 1
Molecule 2
5
Molecule 1
Molecule 2
Cu–S
Cu–P
Cu–Cl
S–C
2.330(1), 2.344(1)
2.287(1), 2.283(1)
2.439(1)
1.693(3), 1.701(3)
112.14(11), 109.33(11)
2.316(1), 2.362(1)
2.289(1), 2.290(1)
2.462(1)
1.695(3), 1.711(3)
110.58(11) 106.47(12)
145.94(4), (Cl)
Cu–S
Cu–P
Cu–Br
S–C
2.356(1), 2.311(1)
2.281(1), 2.283(1)
2.553(1)
2.321(1), 2.337(1)
2.265(1), 2.291(1)
2.554(1)
1.717(3)
1.708(3)
Cu–S–C
Cu–Cl–Cu 146.92(4), (Cl)
P–Cu–S
P–Cu–P
Cu–S–C
Cu–Br–Cu 139.89(2), (Br)
107.42(9), 110.56(9) 112.94(9), 109.76(9)
140.94(2), (Br)
115.45(3), 104.25(3) 114.96(3) 105.86(2)
122.76(3), 122.77(2) 122.35(2), 121.31(3)
113.20(4), 106.13(3), 114.06(3), 105.66(3) 113.66(4), 105.52(4), 114.57(3), 104.43(3) P–Cu–S
122.44(3), 121.14(3)
122.66(3), 122.36(3)
106.98(3), 108.82(3)
P–Cu–P
S–Cu–Br 109.73(2)
S–Cu–Cl 109.23(3), 110.38(3)
111.21(2)
Trinuclear complex (7)
Cu–N
Cu–S
Cu–P
2.080(3)
S–C
Cu–Br
S–Cu–Br
1.693(4), 1.672(4), 1.631(4)
2.478(), 2.477(1)
104.32(3), 109.13(3)
N–Cu–S
P–Cu–P
Cu–S–C
62.93(9)
121.19(4), 124.61(5)
72.03(14), 109.84(14), 114.30(14)
2.395(1), 2.769(1) (Cu2–S1), 2.423(1)
2.270(1), 2.293(1),
a
A case of bond isomerism (6a and 6b) in the crystal lattice. b Each of the complexes, 4 and 5, has independent molecules in the asymmetric unit.
in two cases; however, the Cu–N, Cu–S and Cu–P bond distances
are similar. Methanol was hydrogen-bonded to N4 nitrogen with
˚
an N–O distance of 2.801 A, which is less than the sum of the van
˚
der Waals radius of N and O, viz. 3.05 A, indicating weak O–H/N
interaction.44 The thiouracil did not chelate to CuI in complex 3,
rather it bonded to the metal atom as a neutral ligand through
its S-donor atom, whereas other donor atoms remained
unbound (Fig. 3). As before, the P–Cu–P angle is the largest
{124.53(3)ꢁ}, whereas other angles around the metal center fall
in a narrow range, 103–109ꢁ. Complexes 6a and 6b exist as bond
isomers in the same unit cell (Fig. 4). In 6a, the tmtH2ꢀ as mono
anion is bonded to CuI through its one N donor atom only
forming a three coordinate complex, and in 6b it is bonded to
one N donor and to one S donor atom. Whereas, the Cu–N bond
distances in 6a and 6b are nearly equal, although shorter than in
˚
1 and 2a, the Cu–S distance of 2.879(2) A in 6b is signicantly
longer than that in other mononuclear complexes (1, 2a, 3). In
˚
three-coordinate 6a, the Cu–S distance of 3.144(2) A is still longer
1
Fig. 1 Molecular structure of [Cu(k1N,k S-pymS)(PPh3)2] 1.
˚
than 6b. The expected Cu–S bond distance is 2.61 A, based on the
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dinuclear complex 2b (Fig. 5). It exists as two independent
entities: molecule 1 and molecule 2 in the asymmetric unit. Two
molecules differ signicantly in various bond lengths and bond
angles, particularly pertaining to the bridging sulfur donor
atoms. The N–Cu–S bite angles decrease to 85.85(8)ꢁ and
ꢁ
ꢁ
`
87.66(9) vis-a-vis that 88.24(5) of 2a. The central cores Cu2S2
that have unequal Cu–S distances form parallelograms and
have Cu–S–Cu and S–Cu–S bond angles of 70.60(3)/67.52(4)ꢁ
and 109.40(3)/112.48(4)ꢁ of molecules 1 and 2, respectively, and
are typical of such cores observed in different dinuclear
complexes.47 Compound 4, [Cu2(m-Cl)(k1S,k1S-dtucH)(PPh3)4],
exists as two independent molecules in the asymmetric unit
with small differences in various bond parameters. In this
hetero-bridged dinuclear complex, each copper is bonded to
one S donor atom of dtucH anion, two P donor atoms of two
PPh3 molecules, and one bridging m-Cl (Fig. 6a and b). The
binding pattern of complex [Cu2(m-Br)(k1S,k1S-dtucH)(PPh3)4]
(5) is similar to that of complex 4 (Fig. 7a and b). Each metal
center acquires tetracoordination in a distorted tetrahedral
geometry. The trinuclear complex, [Cu3Br2(k1N,k1S,m-S-
tmtH2)(PPh3)6] 7 has three types of Cu metal ions differently
bonded (Fig. 8 and b). Here, Cu1 is bonded to one Br, two P and
one bridging S donor atoms; Cu3 is bonded to one Br, two P and
one S donor atoms; and nally, Cu2 is bonded to two P, one N
and one bridging S donor atoms. The Cu2–S1 distance is the
longest among various Cu–S distances found in complexes 1, 2,
3–5, except 6b, which is similarly bonded but has a longer
distance than that observed in 7.
Fig. 2 Molecular structure of [Cu(k1N,k1S-purSH)(PPh3)2]$CH3OH 2a.
Variations in C–S, Cu/Cu bond lengths and Cu–S–C bond
angles
Fig. 3 Molecular structure of [CuCl(k1S-tucH2)(PPh3)2] (3).
˚
It is known that the C]S double-bond length is 1.62 A, whereas
44,45
˚
the C–S single-bond length is 1.81 A.
A comparison of C–S
bond distances observed in different complexes (Table 2) reveal
˚
a wide variation from 1.631(4) to 1.739(3) A. In complex 3, the
thio-ligand tucH2 binds to CuI as a neutral ligand, and the C–S
˚
distance of 1.666(2) A exhibits a weakening of this bond on
coordination but there is considerable double-bond character.
Complexes 1, 2, 4 and 5 with pymSꢀ(1), purSHꢀ(2) and
dtucHꢀ(4, 5) uninegative anionic thio-ligands have C–S
distances in the range of 1.693(3) (4, molecule 1)-1.739(3) (2b,
molecule 2), suggesting signicantly larger weakening of C–S
bonds in the complexes. The C–S distances in three-coordinated
6a and tetracoordinated 6b are highly similar and have
considerable double-bond character. Finally, in trinuclear
complex 7, all three C–S distances are distinctly separate:
Fig. 4 Molecular structures of Cu(k1N-tmtH2)(PPh3)2] 6a, [Cu(k1N,
k1S-tmtH2)(PPh3)2]$H2O 6b (bond isomers).
˚
˚
˚
1.693(4) A (bridging S), 1.672(4) A (terminal S) and 1.631(4) A
2ꢀ
ionic radii of Cu+ (0.91 A) and S (1.70 A), and the Cu–S
distances found in 6a and 6b complex species are signicantly
longer and reveal a weak Cu–S bond.44 The Cu–S bonds in other
complexes are similar to the literature trends.1–15
˚
˚
(uncoordinated S). Regarding the Cu/Cu separation, the
shortest distances are found in molecule 1{2.880(1) A} and
molecule 2 {2.717(1) A}, which are comparable with 2.80 A,
which is twice the sum of the van der Waals radius of Cu.46–48 In
˚
˚
˚
˚
other cases, this metal-metal separation was well above 3.0 A
and is not cited in this paper.
Di- and trinuclear complexes
The Cu–S–C angle of 78.98(9) in 1 changes to 93.60(7)ꢁ in 2a,
Complex 2a appears to lose one PPh3 forming species, the cases in which thio-ligands are N,S-chelating. When
{Cu(purSH)(PPh3)}, which dimerized via sulfur to yield the the thio-ligand is N,S-chelating –cum-S bridging as in 2b, the
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Fig. 5 Molecular structure of [Cu2(k1N,k2S-purSH)2(PPh3)2] 2b.
Fig.
7
(a) Molecular structure of dinuclear [Cu2(k2Br)(k1S,
k1S-dtucH)(PPh3)4] (5). (b) Skeletal structure of 5 (phenyl rings omitted).
whether copper metal is chelated (Cu2, N,S-chelation), bonded
to bridging S (Cu1) or nonbridging S(Cu3).
A comparison with literature reports
A comparison with literature reports reveals that pyrimidine-2-
thione(pymSH) bonds to CuI as a neutral thio-ligand (S-bonded
or N,S-bridged) in its complexes with copper(I) halides.9–13,35
Complex 1, obtained from Cu(OAc)(PPh3)2 and pymSH in
methanol-dichloroform, represents the rst example in which
the pymSH is chelating to CuI as the anion. Copper(II) acetate
with pymSH and PPh3 in a 1 : 2 : 2 molar ratio in ethanol also
formed the same product.35 Here, it is inferred that pymSH did
not rupture the Cu-halogen bonds; however, with acetate as the
counter anion, it deprotonated pymSH and the thio-ligand
acted as the anion. This behavior is unlike that shown by
purine-6-thione (purSH2), which ruptured both the Cu-halogen
bonds (Cl, Br) in [Cu(k2-N,S-purSH)(PPh3)2]$CH3OH, or bonded
to the metal center as the neutral ligand in its complexes with
copper(I) halides.36–38 With acetate as the counter anion, purSH2
formed mononuclear Cu(k1N,k1S-purS)(PPh3)2]$CH3OH 2a and
dinuclear [Cu2(k1N,m-S-purS)2(PPh3)2] 2b complexes. Thiouracil
did not rupture Cu-halogen bonds and formed the complex 3, a
Fig.
6
(a) Molecular structure of dinuclear [Cu2(k2Cl)(k1S,k1S-
dtucH)(PPh3)4] (4). (b) Skeletal structure of 4 (phenyl rings omitted).
Cu–S–C angles slightly contract to 89.85(13) and 90.88(12)ꢁ. The
Cu–S–C angle further changes to 69.40(17)ꢁ in 6b in which there
is N,S-chelation. This angle lies in the range of 106–113ꢁ in the
complexes 3, 4 and 5 where a thione sulfur is terminally
(unidentate) bonded. Finally, the Cu–S–C angles in trinuclear
cluster 7 are 72.03, 109.84(14) and 114.30(14)ꢁ depending on
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only other trinuclear cluster of copper(I) with heterocyclic thi-
oamides, namely [Cu3I3L1 L2 ] (L1 ¼ Ph2P–CH2–CH2-PPh2; L2 ¼
3
pyridine-2-thione) was reported from this laboratory.13
NMR (1H and 31P) spectroscopy, electronic absorption and
uorescence spectroscopy
The 1H NMR spectra of complexes 1–7 reveal proton signals
because of the thio-ring protons and phenyl protons of PPh3
(Experimental and ESI†). The PPh3 protons appeared as
complex multiplets, and in only a few cases, signals for o-H, m-H
and p-H protons of phenyl rings could be separated. The
complex 1 did not show a signal for N1H proton, which sup-
ported that the thio-ligand coordinates to CuI as the anion. The
H4 and H5 protons appear at 7.93 and 6.44 ppm, respectively,
and are at high elds relative to the free pymSH ligand, which is
attributed to the aromatization of the pyrimidine ring in the
complex. The N9H, H2 and H8 protons of complex 2a moved at a
low eld relative to the free purSH2 ligand. Similarly, N1,3
H
protons of tucH2 in complex 3 appeared as a combined signal,
which is at low eld, and H5 and H6 signals are marginally
affected relative to a free ligand. In dtucH2 complexes 4 and 5,
the expected N3H proton signals could not be identied because
it was observed to be involved in H/X (X ¼ Cl, Br) hydrogen
bonding (X-ray crystallography, vide supra). The H5 and H6
protons move to a low eld and appeared as a combined signal
Fig. 8 (a) Molecular structure of [Cu3Br2(k1N,k1S,k2S-tmtH2)(PPh3)6]
(7). (b) Skeletal view of 7(phenyl rings omitted).
behavior similar to the one noticed earlier in its only other
trigonal planar complex, [CuCl(k1-S-tucH2)2].39 Dithiouracil with
copper(I) halides shows dual behaviour forming mononuclear
[CuBr(k2-P,P-dppbz)(k1-S-dtucH2)] {dppbz ¼ 1,2-bis(diphenyl-
phosphanyl)benzene} and polynuclear complexes [Cu(m-S,
S-dtucH2)(PPh3)X]n (X ¼ Cl, Br, I) in which there is no Cu-
halogen rupture,40,41 as well as dinuclear complexes 4 and 5 in
which there is a rupture of Cu-halogen bonds {one Cu–X bond
per two CuX units is ruptured}. Complexes 4 and 5 display
unusual eight-membered metallacyclic rings. The reaction of
Cu(OAc)(PPh3)4 with a sodium salt of tmtH3 (tmtH2ꢀNa+) only
gave [Cu(k1N-tmtH2)(PPh3)2] (6a), as reported earlier.42 This
multidentate ligand has shown the formation of unusual
bond isomers, [Cu(k1N-tmtH2)(PPh3)2] (6a) and [Cu(k1N,
k1S-tmtH2)(PPh3)2] (6b) in which the thio-ligand is differentially
bonded, Cu–N (6a) and N,S-chelated (6b). A few other tmtH3
reported complexes are hexanuclear [(Cu6(PPh3)6(m6-tmt)2]43
and polynuclear, [Cu(m3-S,S,S-tmtH3)X]n (X ¼ Cl, Br, I).35 Finally,
tmtH3 with copper(I) bromide in the presence of PPh3 ligand
loses one N–H proton and thio-ligand as anion tmtH2ꢀ binds to
CuI ions in three different bonding modes, resulting in a novel
trinuclear cluster [Cu3Br2(k1N,k1S,m-S-tmtH2)(PPh3)6] (7). The
Fig. 9 (a) Electronic absorption spectra of complexes 1–3. (b) Elec-
tronic absorption spectra of complexes 4–7.
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The 31P NMR spectrum of complex 1 showed one signal with
a coordination shi of 2.84 ppm, suggesting that both phos-
phorus atoms are under identical chemical environments.
Complex 2a with similar stoichiometry showed two 31P NMR
signals, suggesting two types of PPh3 groups. It shows the
formation of 2b in solution. The coordination shis of 1.60 and
3.34 ppm are assigned to complexes 2a and 2b, respectively.
Thiouracil and dithiouracil complexes 3–5 showed one signal
each with Dd values of 1.29, 1.45 and 1.07 ppm, respectively.
Complex 6 whose X-ray crystallography indicated the existence
of bond isomers 6a and 6b revealed equivalent chemical envi-
ronments for PPh3 ligands in a solution state (Dd, 6.10 ppm).
Finally, complex 7 also showed a signal with Dd ¼ 2.13 ppm.
Complexes 1–7 show electronic absorption in the region of
259–450 nm (Fig. 9a and b). The absorption bands in the region
250–291 nm are because of p / p* transitions, whereas those
in the region 334–370 nm are attributed to the metal to thio-
ligand/n / p* transitions. To investigate if these copper(I)
complexes display any emission properties, the complexes were
excited in the region 270 to 291 nm. The complexes exhibited
intense emission bands in the 380–530 nm region with lmax at
490 to 495 nm (Fig. 10).
Fig. 10 Fluorescence spectra of complexes 1–7. (It may be noted that
emission shown in the region of 540–586 nm is shown by DMSO in
the absence of the sample and appears at twice the wavelength of
excitation at 276 nm-spectrum of DMSO placed in ESI†).
Table 3 ESI-mass data indicating assignment
Complex % Intensity m/z: obsd m/z: calcd. Species identied
1
2
20
100
15
70
25
100
40
20
587.1
761.0
935.0
1023.1
1197.1
477.0
803.0
587.1
1065.1
587.1
587.1
729.0
991.0
587.1
676.9
765.0
939.0
587.1
587.1
761.0
935.0
1023.1
1197.1
478.0
803.0
587.1
1065.2
587.1
587.1
729.0
991.0
587.5
676.9
763.1
939.0
587.1
[Cu(PPh3)2]+
[Cu2(pymS)(PPh3)2]+
[Cu3(pymS)2(PPh3)2]+
[Cu2(pymS)(PPh3)3]+
[Cu3(pymS)2(PPh3)3]+
[Cu(purS)(PPh3) + 2H]+
[Cu2(purS)(PPh3)2 + 2H]+
[Cu(PPh3)2]+
ESI-mass spectral studies
The ESI-mass spectral data of most of the complexes (1–3, 5–7)
have been obtained. The purpose of carrying out this study was
manifold: to determine the molecular ion ([M]+), to understand
the fragmentation pattern and the formation of new species,
and to investigate the possibility of rupture of the Cu–P, Cu–S or
C–S bonds. The C–S rupture is signicant, particularly because
of the presence of PPh3 in the complexes, which might assist in
such cleavage. The signicant species identied are listed in
Table 3 and are discussed. The most signicant feature of this
study is the formation of the species [Cu(PPh3)2]+, which is most
abundant in complexes 3–7 and is reasonably intense in
complexes 1 and 2. This shows that Cu–P bond is the most
stable, and the rupture predominantly occurs at Cu–S/N bonds.
Species that could be attributed only to [Cu(thio-ligand)n]+were
not observed. Nevertheless, there is a tendency to form mono-
nuclear, dinuclear and trinuclear species. In complexes 3, 5,
species containing both the thio-ligand and PPh3 components
were not observed; rather, only PPh3 and halogens bonded to
10
[Cu2(purS)(PPh3)3 + 2H]+
[Cu(PPh3)2]+
3
5
100
100
10
15
100
85
25
80
100
[Cu(PPh3)2]+
[Cu2Br(PPh3)2]+
[Cu2Br(PPh3)3]+
6
7
[Cu(PPh3)2]+
[Cu(tmtH2)2(PPh3)]+
[Cu(tmtH2)(PPh3)2]+
[Cu(tmtH2)2(PPh3)2]+
[Cu(PPh3)2]+
at 7.58 and 7.56 ppm in 4 and 5, respectively. Regarding H3tmt
complexes 6 and 7, while complex 6 exhibited one signal at 9.90
ppm assigned to N3,5H protons, no NH signal could be detected
in 7 probably due to broadening by quadrupolar nitrogen.
Fig. 11 ESI-mass peak due to [Cu(PPh3)2]+ with isotopic pattern (complex 6).
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Fig. 12 ESI-mass peak due to molecular ion with isotopic pattern (complex 6).
CuI were found to be present. In addition, there is no evidence trimercaptotriazine, purine-6-thione, pyrimidine-2-thione, 2,4-
to support the rupture of C–S bonds, and this could be attrib- dithiouracil and 2-thiouracil were procured from Sigma-Aldrich
uted to the high stability of [Cu(PPh3)2]+ moiety, which favored Ltd. Melting point was determined with a Gallenkamp electri-
the de-ligation of thio-ligand moiety. Mixed-ligand species cally heated apparatus. IR spectra were recorded using KBr
containing both the thio-ligand and PPh3 components in pellets on Varian 660 FT IR and Perkin Elmer FT IR Spectrom-
complexes 1, 2 and 6 support that thio-ligands remain intact in eter in 4000–200 cmꢀ1 range. 1H NMR spectra were recorded in
the reaction system without any degradation and recombine CDCl3 using a Bruker Avance II 400 NMR spectrometer at 400
with Cu+ in different manners, generating unusual species, as MHz and JEOL AL300 FT 1H NMR at 300 MHz using TMS as an
given in Table 3. Only complex 6 showed the presence of a internal reference. 31P NMR spectra were recorded in CDCl3
molecular ion, [M]+ (m/z obsd. 765.0; calcd. 763.1). Interestingly, with Bruker Avance II 400 NMR at 161.97 MHz spectrometers
ESI-mass has very clearly supported our contention that 2b with o-phosphoric acid as the external reference (d ¼ 29.15
appears to have been formed from 2a via the formation of the ppm). The ESI-MS mass spectra was recorded on a microTOF-
most intense species, [Cu(purSH)(PPh3) +2H]+, which is strongly QII 10356 in positive mode.
implicated in its spectrum (m/z, obsd. 477.0; calcd. 478.0).
Finally, the spectrum of complex 1 has shown the formation of
dinuclear and trinuclear complex species. Fig. 11 shows ESI-
mass peak due to [Cu(PPh3)2]+ with an isotopic pattern found in
complex 6, and Fig. 12 shows its molecular ion peak.
Synthesis of complexes
[Cu(k1N, k1S-pymS)(PPh3)2] (1). To a methanolic (5 mL)
solution of pymSH (0.004 g, 0.036 mmol), a solution of
[Cu(PPh3)2(CH3COO)] (0.025 g, 0.039 mmol) in dichloro-
methane (5 mL) was slowly, and the clear solution was kept
undisturbed at room temperature for a period of three to four
days. The resulting pale yellow solution was allowed to evapo-
rate slowly at room temperature. The pale yellow crystals of 1
were formed over a period of three days. Yield: 0.018 g, 72%;
m.p 166–168 ꢁC. Anal. calc. for C40H33N2CuP2S (699.24): C,
68.65; H, 4.72; N, 4.01. Found: C, 68.87; H, 5.02; N, 3.01%. Main
IR peaks (KBr, cmꢀ1): n(C–H), 3048m, 3013w, 3001w, 2925w;
n(C–C) + n(C–N) + d(C–H), 1566s, 1531s, 1479s, 1434s; 1370s,
1309w, 1238m, 1215w, 1183s, 1157w; n(P–C), 1093s; 1070w,
n(C–S), 1026m; 997m, 850w, 796w, 768w, 747s, 695s, 651w,
619w, 516s, 505m, 467w. 1H NMR (d, ppm, J, Hz, CDCl3): 7.93 (d,
1H, J, 4.2, Hz, H4), 7.33 (m, 31H, H6, o-H, m-H and p-H, PPh3),
6.44 (t, 1H, J, 4.5, Hz, H5). 31P NMR (CDCl3, d ppm): ꢀ2.63 ppm,
Conclusion
The present investigation signicantly contributes to copper-
heterocyclic thioamide chemistry with scarcely investigated
multifunctional thio-ligands, particularly purine-6-thione,
thiouracils and 2,4,6-trimercaptotriazine. The formation of
mono- and di-nuclear complexes (2a, 2b), display of bond
isomerism by complex 6, formation of dinuclear complexes 4
and 5 with unusual bonding patterns, and the synthesis of rare
trinuclear complex 7 are novel features of this study. The only
other trinuclear cluster of copper(I) with heterocyclic thio-
amides, particularly [Cu3I3L13L2 ] (L1 ¼ Ph2P–CH2–CH2–PPh2; L2
¼ pyridine-2-thione), was reported from this laboratory.13
Dd(dcomplex ꢀ dPPh ) ¼ 2.84 ppm. UV-vis. data, DMSO, lmax
/
3
nm,:[10ꢀ5 M] 250–400 nm. Fluorescence data (l
¼ 494 nm,
em
max
Experimental
Materials and techniques
ex
l
¼ 274 nm).
max
[Cu(k1N,k1S-purSH)(PPh3)2]$CH3OH (2a). To a methanolic (5
The precursor, particularly Cu(PPh3)2(CH3COO), was prepared mL) solution of purSH (0.006 g, 0.039 mmol), a solution of
by the reduction of Cu(CH3COO)2 using a four-fold excess of [Cu(PPh3)2(CH3COO)] (0.025 g, 0.039 mmol) in dichloro-
PPh3 in CH3OH at a reux temperature for 3 h.49 Copper(I) methane (5 mL)was slowly added, and the clear solution was
halides were prepared by the reduction of CuSO4$5H2O using kept undisturbed at room temperature for a period of three to
SO2 in the presence of stoichiometric amounts of NaCl, NaBr, four days. The resulting pale yellow solution was allowed to
and NaI in water.50 Organic ligands, namely 2,4,6- evaporate slowly at room temperature. The pale yellow (2a) and
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yellow (2b) crystals were formed simultaneously over a period of p-H, PPh3). 31P NMR (CDCl3, d ppm): ꢀ4.02 ppm, Dd(dcomplex
ꢀ
three to four days, and the crystals were manually separated. dPPh ) ¼ 1.45 ppm. UV-vis. data, DMSO, lmax/nm, 3/L molꢀ1
3
[Cu(k2-N,S-purS)(PPh3)2]$CH3OH (2a) Yield: 0.016 g, 64%; m.p cmꢀ1: [10ꢀ5 M] 367 (7.54 ꢂ 103), 262 (4.76 ꢂ 104). Fluorescence
em
ex
above 300 ꢁC. Anal. calc. for C42H37N4OCuP2S (771.30): C, 65.34; data (l
H, 4.80; N, 7.26. Found: C, 65.56; H, 4.91; N, 7.43%. Main IR
¼ 495 nm, l
¼ 276 nm).
max
max
[Cu2(m-Br)(k1S,k1S-dtucH)(PPh3)4] (5). This was prepared by
peaks (KBr, cmꢀ1): n(N–H), 3080sh; n(C–H), 3049m, 2960w, the method used for the preparation of complex 4. Slow evap-
2936w, 2816m; n(C–C) + n(C–N) + d(C–H), 1592s, 1564s, 1479s, oration of the solution at room temperature formed light
1434s; 1374s, 1320s, 1233s, 1183w, 1129w; n(P–C), 1094s; orange crystals of [Cu2(m-Br)(m-S,S-dtucH)(PPh3)4] 5 (Yield: 0.024
1038m; n(C–S), 942m; 853s, 793w, 748s, 696s, 646m, 603w, 516s, g, 20%, M.p. 181–183 ꢁC). Anal. calcd for C76H63BrCu2N2P4S2
1
431w. H NMR (d, ppm, J, Hz, CDCl3): 14.45 (sb, N9H), 8.50 (s, (1399.27): C, 65.18; H, 4.50; N, 2.00; Found: C, 65.15; H, 4.21; N,
1H, H8), 8.22 (sb, 1H, –OH, CH3OH), 7.68 (m, 1H, H2), 7.47 (m, 2.14%. Main IR peaks (KBr, cmꢀ1): n(N–H), 3090w; n(C–H),
12H, o-H, PPh3), 7.22 (m, 18H, m-H and p-H, PPh3), 3.49 (s, 3H, 3048m, 2970w, 2925m, 2854w; n(C–N) + d(C–H), 1541s, 1505m,
CH3OH). 31P NMR (CDCl3, d ppm): ꢀ2.13, ꢀ3.87 ppm, 1479s; 1433s, 1384w, 1348w, 1309w, 1270m, 1204w, 1180w,
Dd(dcomplex ꢀ dPPh ) ¼ 3.34, 1.6 ppm. UV-vis. data, DMSO, lmax
/
1156w; n(C–S) 1126m; n(P–C), 1093m; 1026w, 996w, 976w, 920w,
3
nm, 3/L molꢀ1 cmꢀ1: [10ꢀ5 M] 334 (1.38 ꢂ 104). Fluorescence 832m, 742s, 693s, 616w, 516s. H NMR (d, ppm, J, Hz, CDCl3):
1
em
ex
data (l
¼ 490 nm, l
¼ 266 nm).
7.56 (m, 2H, H5,6), 7.37 (m, 12H, o-H, PPh3), 7.27 (m, 6H, p-H,
max
max
[Cu2(k1N,m-S-purS)2(PPh3)2] (2b). Yield: 0.004 g, 13%; m.p PPh3), 7.16 (m, 12H, m-H, PPh3). 31P NMR (CDCl3, d ppm): ꢀ4.4
above 300 ꢁC. Anal. calc. for C46H36N8Cu2P2S2 (953.97): C, 57.86; ppm, Dd(dcomplex ꢀ dPPh ) ¼ 1.07 ppm. UV-vis. data, DMSO, lmax
/
3
H, 3.77; N, 11.74. Found: C, 57.80; H, 3.19; N, 11.20%. Main IR nm, 3/L molꢀ1 cmꢀ1: [10ꢀ5 M] 370 (8.21 ꢂ 103), 262 (5.30 ꢂ 104).
peaks (KBr, cmꢀ1): n(N–H), 3130sh; n(C–H), 3051m, 2926w, Fluorescence data (l
¼ 493 nm, l
¼ 273 nm).
em
ex
max
max
2870w, 2766w; n(C–C) + n(C–N) + d(C–H), 1579s, 1477m, 1434s;
1385s, 1324m, 1230w, 1180m, n(P–C), 1094m; 1025m, 938w; methanolic (5 mL) solution of H3tmt (0.007 g, 0.039 mmol), a
n(C–S), 844m; 742s, 693s, 667w, 612m, 521s. solution of [Cu(CH3COO)(PPh3)2] (0.025 g, 0.039 mmol) in
[Cu(tmtH2)(PPh3)2]$0.5H2O (6) (bond isomers 6a,6b). To a
[CuCl(k1S-tucH2)(PPh3)2] (3). To a solution of copper(I) dichloromethane (5 mL) was slowly added, and the clear solu-
chloride (0.025 g, 0.25 mmol) in acetonitrile, a solution of 2- tion was kept undisturbed at room temperature for a period of
thiouracil (0.032 g, 0.25 mmol) in methanol was added, fol- three to four days. The reaction mixture became pale yellow and
lowed by stirring for 1 h at room temperature. Ph3P (0.132 g, was allowed to evaporate slowly at room temperature. The pale
0.50 mmol) was added to the obtained precipitates and stirred yellow-colored crystals were formed over a period of two to three
until a clear solution was obtained. The slow evaporation of the days. Yield: 0.021 g, 70%; m.p above 300 ꢁC. Anal. calc. for
solution at room temperature formed pale yellow crystals of 3.
Yield: 0.12 g, 63%, M.p. 180–182 ꢁC. Anal. calcd for C, 59.88; H, 4.66; N, 5.49%. Main IR peaks (KBr, cmꢀ1): n(N–H),
40H34ClCuN2OP2S (751.68): C, 63.86; H, 4.52; N, 3.72; Found: 3110sh; n(C–H), 3051m, 2959w, 2910m, 2831w; n(C–C) + n(C–N)
C39H33N3O0.50CuP2S3 (773.34): C, 60.52; H, 4.27; N, 5.43. Found:
C
C, 63.85; H, 4.34; N, 3.56%. Main IR peaks (KBr, cmꢀ1): n(O–H), + d(C–H), 1532m, 1477s; 1434s, 1396w, 1353s, 1233s, 1171m,
3447w; n(N–H), 3130w; n(C–H), 3048m, 3010w, 2960w; n(C–N) + 1154w, 1138s; n(P–C), 1095m; 1070w, 1026w, n(C–S), 1014m;
d(C–H) 1584m, 1480s; 1432s, 1309m, n(C–S) 1184m, 1154m; n(P– 998w, 917w, 893m, 882m, 849w, 743s, 693s, 618w, 517s, 492w,
C), 1091(s); 1027m, 998m, 923w, 851m, 743s, 694s, 517s. 1H 454s. 1H NMR (d, ppm, J, Hz, CDCl3): 9.90 (sb, 3H,
NMR (d, ppm, J, Hz, CDCl3): 13.58 (sb, 2H, N1,3H), 5.82 (d, 1H, J 2NH+0.5H2O), 7.36 (m, 18H, o-H and p-H, PPh3), 7.24 (m, 12H,
¼ 7.8 Hz, H5), 7.02 (d, 1H, J ¼ 7.8 Hz, H6), 7.19–7.42 (m, 15H, m-H, PPh3). 31P NMR (CDCl3, d ppm): 0.63 ppm, Dd(dcomplex
ꢀ
Ph3P). 31P NMR (CDCl3, d ppm): ꢀ4.18 ppm, Dd(dcomplex ꢀ dPPh
)
dPPh ) ¼ 6.10 ppm. UV-vis. data, DMSO, lmax/nm, 3/L molꢀ1
3
3
¼ 1.29 ppm. UV-vis. data, DMSO, lmax/nm, 3/L molꢀ1 cmꢀ1
:
cmꢀ1: [10ꢀ5 M] 346 (1.41 ꢂ 104), 291 (2.66 ꢂ 104). Fluorescence
em
ex
max
em
max
ex
max
[10ꢀ5 M] 250–400 nm. Fluorescence data (l ¼ 493 nm, l
¼
data (l
¼ 494 nm, l
¼ 291 nm).
max
270 nm).
[Cu3Br2(k1N,k1S,m-S-tmtH2)(PPh3)6] (7). To a solution of
[Cu2(m-Cl)(k1S,k1S-dtucH)(PPh3)4] (4). To a solution of cop- copper(I) bromide (0.025 g, 0.25 mmol) in acetonitrile (10 mL), a
per(I) chloride (0.025 g, 0.25 mmol) in acetonitrile (10 mL), a solution of 2,4,6-trimercaptotriazine (0.031 g, 0.25 mmol) in
solution of 2,4-dithiouracil (0.036 g, 0.25 mmol) in methanol (5 methanol (5 mL) was added, followed by stirring for 24 h at
mL) was added, followed by stirring for 24 h at low temperature room temperature. Solid Ph3P (0.091 g, 0.50 mmol) was added
(20 ꢁC). Solid Ph3P (0.132 g, 0.50 mmol) was added to the to the obtained orange precipitates. The contents were stirred
obtained orange precipitates. The contents were stirred until a until a clear solution was obtained, and the slow evaporation of
clear solution was obtained. Slow evaporation of solution the solution at room temperature formed yellow crystals of 7,
formed light orange crystals of [Cu2(m-Cl)(m-S,S-dtucH)(PPh3)4] which are stable in mother liquor. Yield: 0.084 g, 68%, M.p.
ꢁ
4. Yield: 0.032 g, 19%, M.p. 178–180 ꢁC. Anal. calcd for 200–203 C. Anal. calcd for C111H92Br2Cu3N3P6S3 (2100.32): C,
C
76H63ClCu2N2P4S2 (1354.81): C, 67.32; H, 4.65; N, 2.07; Found: 63.42; H, 4.38; N, 2.00; Found: C, 63.47; H, 4.51; N, 1.27%. Main
C, 67.02; H, 4.56; N, 2.18%. Main IR peaks (KBr, cmꢀ1): n(N–H), IR peaks (KBr, cmꢀ1): n(N–H), 3140w; n(C–H), 3049m, 3010w,
3250sh; n(C–H), 3049w, 2995w, 2927w; n(C–N) + d(C–H), 1543s, 2920w, 2855m; n(C–N) + d(C–H), 1524s, 1460s; 1433s, 1394m,
1507m, 1478m; 1433m, 1384w, 1271m, 1205w; n(C–S) 1128m; 1362s, 1274w; n(C–S), 1177s, 1126s; n(P–C), 1093s; 1026w, 997w,
n(P–C), 1094m; 833m, 743s, 693s, 616w, 516s. 1H NMR (d, ppm, 868w, 743w, 694s, 618w, 518s, 456w. H NMR (d, ppm, J, Hz,
1
J, Hz, CDCl3): 7.58 (m, 2H, H5,6), 7.26 (m, 30H, o-H, m-H and CDCl3): 7.33 (m, 30H, o-H, m-H and p-H, PPh3). 31P NMR (CDCl3,
30520 | RSC Adv., 2014, 4, 30511–30522
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d ppm): -3.34 ppm, Dd(dcomplex ꢀ dPPh ) ¼ 2.13 ppm. UV-vis. data, 13 T. S. Lobana, R. Sharma, R. Sharma, S. Mehra, A. Castineiras
3
DMSO, lmax/nm, 3/L molꢀ1 cmꢀ1: [10ꢀ5 M] 363 (1.41 ꢂ 104), 262
and P. Turner, Inorg. Chem., 2005, 44, 1914–1921.
¼ 273 nm). 14 T. S. Lobana, R. Sultana, Geeta Hundal and R. J. Butcher,
Dalton Trans., 2010, 39, 7870–7872.
em
max
ex
max
(8.11 ꢂ 104). Fluorescence data (l
¼ 495 nm, l
15 T. S. Lobana, R. Sultana and R. J. Butcher, Dalton Trans.,
2011, 40, 11382–11384.
16 U. Kela and R. Vijayavargiya, Biochem. J., 1981, 193, 799–803.
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18 M. S. Masoud, A. A. Soayed and A. F. El-Husseiny,
Spectrochim. Acta, Part A, 2012, 99, 365–372.
19 I. Papazoglou, P. J. Cox, A. G. Papadopoulos, M. P. Sigalasc
and P. Aslanidis, Dalton Trans., 2013, 42, 2755–2764.
20 K. Paizanos, D. Charalampou, N. Kourkoumelis,
D. Kalpogiannaki, L. Hadjiarapoglou, A. Spanopoulou,
K. Lazarou, M. J. Manos, A. J. Tasiopoulos, M. Kubicki and
S. K. Hadjikakou, Inorg. Chem., 2012, 51, 12248–12259.
21 G. Christodis, P. J. Cox and P. Aslanidis, Polyhedron, 2012,
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22 I. I. Ozturk, S. K. Hadjikakou, N. Hadjiliadis,
N. Kourkoumelis, M. Kubicki, A. J. Tasiopoulos,
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X-ray crystallography
Single crystals of compounds were mounted on glass bers, and
data were collected on a Bruker CCD SMART1000 (1), Xcalibur,
Eos, Gemini (2a, 4, 3, 7), Xcalibur, Ruby, Gemini (2b, 5) and
Bruker APEX-II CCD (1) diffractometer equipped with a graphite
˚
monochromator and Mo–Ka radiation (l ¼ 0.71073 A; 6, 2a, 1, 4,
˚
5, 3, 7) and Cu-Ka radiation (l ¼ 1.54184 A; 2b). The unit-cell
dimensions and intensity data were measured at 100(2) K for 6,
173(2) for 2a, 4 and 7, 295(2) for 2b, 296(2) K for 1, 123(2) for 5
and at 170(2) for 3. The data were processed with SMART (data
collection, cell renement), SAINT (data reduction) (1), CrysA-
lisPro (data collection, cell renement) (2a, 2b, 4, 5, 3, 7), Cry-
sAlisPro RED (data reduction) (2a, 4, 3), CrysAlisPro (data
reduction) (2b, 5 and 7),51 Bruker APEX2 (data collection), and
Bruker SAINT (cell renement, data reduction) (1).52 The
structures were solved by direct methods using the program
SHELXS-97 (ref. 53) (6, 2a, 2b, 4, 5, 3, 7), SIR-92 (1)54 and rened
by full-matrix least-squares techniques against F^2 using
SHELXL-97.55 The structure of 6 was rened as a racemic twin
with components 0.54(1), 0.46(1).56
23 M. N. Xanthopoulou, S. K. Hadjikakou, N. Hadjiliadis,
M. Kubicki, S. Skoulika, T. Bakas, M. Baril and I. S. Butler,
Inorg. Chem., 2007, 46, 1187–1195.
24 I. Ozturk, S. Filimonova, S. K. Hadjikakou, N. Kourkoumelis,
V. Dokorou, M. J. Manos, A. J. Tasiopoulos, M. M. Barsan,
I. S. Butler, E. R. Milaeva, J. Balzarini and N. Hadjiliadis,
Inorg. Chem., 2010, 49, 488–501.
25 P. P. Lourido, J. A. Garcia-Vazquez, J. Romero, M. S. Louro,
A. Sousa and J. Zubieta, Inorg. Chim. Acta, 1998, 271, 1–8.
26 R. Castro, J. Romero, J. A. Garcia-Vazquez, A. Sousa,
Y. D. Chang and J. Zubieta, Inorg. Chim. Acta, 1996, 245,
119–122.
Acknowledgements
Financial assistance from the University Grant Commission
(BSR, UGC); the Council of Scientic and Industrial Research
(CSIR), New Delhi; Emeritus Grant [21(0904)/12-EMR-II] to TSL;
and the Department of Science and Technology (DST) ST for the
X-ray diffractometer grant to the department are gratefully
acknowledged.
27 J. A. Garcia-Vazquez, J. Romero, A. S. Pedrares, M. L. Louro,
A. Sousa and J. Zubieta, J. Chem. Soc., Dalton Trans., 2000,
559–567.
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