Synthesis, structure, photophysical and catalytic properties of CuI-Iodide complexes of di-imine ligands

Article abstract of DOI:10.1016/j.molstruc.2015.12.028

Two new multifunctional Cu^II based complexes [CuI(L¹)] (1) and [Cu₂(μ-I)₂(L²)] (2) with bidentate N-N donor ligands L¹ and imino-pyridyl ligand L² have been synthesized and characterized by elemental analysis, IR, UV-Vis, NMR and single crystal X-ray crystallography. The bidentate di-imine ligand (L¹) forms monomeric Cu^I complex (1) whereas the bis-bidentate di-imine ligand (L²) favours the formation of dimeric Cu^I complex (2) in association with two bridging iodides. Structural analysis reveals that in complex 1 each monomeric units are connected by π? and C-H?π interactions to form 3D supramolecular structure whereas in complex 2 each molecules are connected by only πmellip;π interactions to form 3D supramolecular structure. The photoluminescence properties of the complexes have been studied at room temperature. Theoretical analysis shows that HOMO is focused on the Cu and iodides while LUMO is focused on di-imine ligands and the luminescence behaviour arises due to metal to ligand charge transfer (MLCT) and halide to ligand charge transfer (XLCT). The complexes 1 and 2 are effective catalysts for the synthesis of 2-substituted benzoxazoles.

Full text of DOI:10.1016/j.molstruc.2015.12.028

Journal of Molecular Structure 1108 (2016) 315e324
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Synthesis, structure, photophysical and catalytic properties of
I
Cu eIodide complexes of di-imine ligands
*
Jahangir Mondal, Anupam Ghorai, Sunil K. Singh, Rajat Saha, Goutam K. Patra
Department of Chemistry, Guru Ghasidas Vishwavidyalaya, Bilaspur, C.G, India
a r t i c l e i n f o
a b s t r a c t
I
1
2
Article history:
Received 18 July 2015
Received in revised form
2 2
Two new multifunctional Cu I based complexes [CuI(L )] (1) and [Cu (m-I) (L )] (2) with bidentate NeN
donor ligands L1 and imino-pyridyl ligand L2 have been synthesized and characterized by elemental
analysis, IR, UVeVis, NMR and single crystal X-ray crystallography. The bidentate di-imine ligand (L )
forms monomeric Cu complex (1) whereas the bis-bidentate di-imine ligand (L ) favours the formation
of dimeric Cu complex (2) in association with two bridging iodides. Structural analysis reveals that in
complex 1 each monomeric units are connected by
molecular structure whereas in complex 2 each molecules are connected by only
1
3
November 2015
I
2
Accepted 12 December 2015
Available online 17 December 2015
I
p
/
p
and CeH/
p
interactions to form 3D supra-
interactions to
p/p
Keywords:
form 3D supramolecular structure. The photoluminescence properties of the complexes have been
studied at room temperature. Theoretical analysis shows that HOMO is focused on the Cu and iodides
while LUMO is focused on di-imine ligands and the luminescence behaviour arises due to metal to ligand
charge transfer (MLCT) and halide to ligand charge transfer (XLCT). The complexes 1 and 2 are effective
catalysts for the synthesis of 2-substituted benzoxazoles.
N-N donor ligand
Cu I complexes
Crystal structure
Monomer
Dimer
I
Photophysics
Catalysis
©
2015 Elsevier B.V. All rights reserved.
þ
1. Introduction
investigated to date is that of [Cu(NeN)
2
] , where NeN indicates a
chelating ligand and the luminescence property of such complexes
originates due to metal to ligand charge transfer (MLCT) [23e26]. In
addition to the monomeric complexes, it has been noticed that the
presence of halides favours the formation of polynuclear complexes
Luminescent materials have attracted considerable attention for
their numerous potential applications in solar energy conversion
[1,2], luminescence-based sensors [3,4], organic light emitting di-
odes (OLEDs) [5e8] and biological labelling [9e11]. Monovalent
with
m2-, m3-, or m4-bridging halide atoms, and their structures are
I
I
I
group 11 metal ions, Au , Ag , and Cu , are well known for their
also dependent on chelating ligand along with their synthetic
procedure [27e31]. A number of complexes with a {Cu (m-I )} unit
2 2
I
I
interesting emissive properties [12]. Among these metal ions Cu is
inexpensive and abundant and thus the synthesis and study of
mono-/ploy-nuclear CuI complexes with di-imine ligands have
become an important area of current research [13]. The judicious
selection of NeN chelating ligands is the key point to control and
tune the structure and luminescence properties [14e16]. The
ancillary ligands such as halide and phosphine also have great ef-
have been prepared with various ligands and most of them possess
a planar diamond core [32,33]. Studies on these complexes show
that luminescence originates from {CuI
(m-I )} core to ligand charge
2 2
transfer (MLCT) excited state, which is critical to the rigidity of the
ligand.
In addition to this photophysical property, Cu(I) complexes are
well-known for their catalytic properties. There are few examples
in which Cu(I)-complexes act as efficient catalyst. G. Attilio Ardiz-
zoia et al. have reported the catalytic cyclopropanation reactions of
four Cu(I)-based complexes [34]. In another case, S. S. Chavan et al.
have reported that the Cu(I)-complexes act as effective catalyst for
the amination of aryl halides [35].
I
fects on the emissive properties of the Cu -complexes [17e21].
Several excited states such as metal-centered transitions, intra-
ligand transitions, and charge-transfer (CT) transitions between
metal and ligands exist as emissive states, depending on the ligands
and steric factors [22].
I
The largest class of luminescent Cu complexes has been
Herein, we have designed two different di-imine ligands; one is
1
2
bidentate (L ) and the other is bis-bidentate (L ) and synthesized
their Cu(I) complexes, 1 and 2 exploiting Cu(I)-iodides. Both the
complexes are characterized by elemental analysis, IR, UVeVis and
*
Corresponding author.
E-mail address: patra29in@yahoo.co.in (G.K. Patra).
http://dx.doi.org/10.1016/j.molstruc.2015.12.028
022-2860/© 2015 Elsevier B.V. All rights reserved.
0

316
J. Mondal et al. / Journal of Molecular Structure 1108 (2016) 315e324
1
3
ꢀ1
ꢀ1
single crystal X-ray crystallography. The bidentate ligand (L ) forms
3
UVeVIS lmax/nm (ε/dm mol cm ) (CH OH): 288 (27 500 260),
363 (10 250).
I
2
the monomeric Cu complex (1) while the bis-bidentate ligand (L )
favours the formation of dimeric complex (2) with very short
CueCu bond (2.486 Å) (Scheme 1). In complex 1, metal ions shows
trigonal geometry while in complex 2 each metal ions show
tetrahedral geometry. In 2, the dimer formation is favoured by
bridging of iodides. Supramolecular and CeH/ interactions
2.2.2. Synthesis of ligand L2
2.36 g (15 mmol) of 2-quinolinecarboxaldehyde was dissolved
in 100 ml of anhydrous methanol. To this yellowish solution 0.5 ml
(7.5 mmol) of freshly distilled ethylene diamine was added drop-
wise with stirring. Then, the reaction mixture was allowed to
reflux for 6 h, maintaining dry conditions. The solvent was evapo-
rated under reduced pressure to obtain a yellow semi-solid, which
on re-crystallization from diethyl ether gave yellow crystalline
m-2
p/p
p
connect each monomeric units in 1 to form 3D supramolecular
structure. And in 2, each molecules are connected by supramolec-
ular
p/p interactions to form 3D supramolecular structure. The
photoluminescence and catalytic properties of the complexes have
been studied. However, as far we know, this is the first report of
multifunctional properties of Cu(I)-complexes.
ꢁ
solid. Yield: 1.75 g (69%); mp: 128e130 C. Anal. found (calc. for
C22H18N ): C, 77.65 (78.07); H, 5.37 (5.36); N, 16.65 (16.56)%. EI-MS:
4
þ
þ
þ
3
38.1 (M , 84%); 181.1 (M ꢀ C10
H
6
NO, 25%); 169.1 (M /2, 98%).
FTIR/cm (KBr): 3451(vb), 3050 (m), 2890 (m), 1642(vs) (C]N),
592(vs), 1557(s), 1500(vs), 1461(s), 1432(s), 1382(m), 1321(w),
1280(s), 1206(m), 1142 (m), 1108(s), 1030(s), 1015(w), 971(s),
ꢀ
1
2
. Experimental
1
2.1. Materials and measurements
1
9
41(m), 893(s), 868(s), 840(vs), 748(vs), 619(m), 492(m). H NMR
(200 MHz, CDCl , TMS):
8.63 (s, 2H), 8.17 (s, 4H), 8.11 (d, J ¼ 4 Hz,
2H), 7.83-7.69 (m, 4H), 7.57 (t, J ¼ 4 Hz, 2H), 4.18 (s, methylene, 4H).
All the reagents were procured commercially from Aldrich and
used without further purification. Microanalyses were performed
by PerkineElmer 2400II elemental analyzer. The melting point
3
d
13
C NMR (200 MHz, CDCl
3
, TMS): d 163.91, 154.52 (quaternary),
(
mp) was determined by an electro-thermal IA9000 series digital
147.65 (quaternary), 136.50, 129.70, 129.50, 128.71 (quaternary),
3
ꢀ1
ꢀ1
melting point apparatus and is uncorrected. IR spectra (KBr disc)
were recorded on a Nicolet Magna-IR spectrophotometer (Series II),
UVeVis spectra on a Shimadzu UV-160A spectrophotometer,
and C NMR spectra by a Brucker DPX200 spectrometer, EI mass
spectra on a VG Autospec Mꢀ250 instrument. Photoluminescence
spectra were recorded on a Perkin Elmer LS55 Luminescence
Spectrometer.
127.63, 127.34, 118.40, 61.43. UVeVIS
(CH OH): 290 (10 260), 242 (42 710).
lmax/nm (ε/dm mol cm
)
3
1
H
13
2.3. Preparation of complexes
1
2.3.1. Synthesis of [CuI(L )] (1)
CuI (0.19 g, 1 mmol) dissolved in acetonitrile (30 ml) is added
1
dropwise into a 20 ml chloroform solution of the ligand L (0.498 g,
2
2
.2. Synthesis of ligands
1 mmol) within 1 h. Then the brownish reaction mixture is stirred
for another 1 h at room temperature. Reddish brown complex has
appeared. It is filtered out and washed with 5 ml acetonitrile and
dried in vacuo; yield, 4.485 g (65%). Deep red single crystals suitable
for X-ray analysis are obtained by careful layering of CuI (1.9 mg,
0.01 mmol) dissolved in acetonitrile (4 ml) onto a 4 ml chloroform
.2.1. Synthesis of ligand L1
3
.45 g (15 mmol) of 1- pyrenecarboxaldehyde was dissolved in
00 ml of anhydrous methanol. To this light yellowish solution
.625 ml (7.5 mmol) of freshly distilled 1,2-diaminopropane was
1
0
1
added drop-wise with stirring. Then, the reaction mixture was
allowed to reflux for 6 h, maintaining dry conditions. The solvent
was evaporated under reduced pressure to obtain a yellow solid. It
was thoroughly washed with methanol. Yield: 2.615 g (70%); mp:
solution of the ligand L (5 mg, 0.01 mmol). Anal. Calcd. for
37 26 2
C H N CuI: C 64.49, H 3.80, N 4.06; found: C 64.43, H 3.87, N 4.10.
ꢀ
1
FTIR cm
(KBr): 3047(m), 2922(m), 1613(s), 1593(s), 1252(m),
1234(s), 1108(m), 994(m), 844(vs), 824(m), 767(s), 715(vs), 475(m).
ꢁ
2
(
1
02e205 C. Anal. calc. for C37
5.25); N, 5.66 (5.62)%. EI-MS: 499.6 (M , 85%). FTIR/cm (KBr):
637(s), 1583(s), 843(vs), 829(m), 759(m), 716(vs), 682(m), 610(m).
H
26
N
2
: C, 89.19 (89.13); H, 5.20
UVeVis (MeCN) [
lmax, nm]: 283, 366.
þ
ꢀ1
2
2.3.2. Synthesis of [Cu
2
(
m-I)
2
(L )] (2)
1
H NMR (400 MHz, CDCl
3
, TMS):
H), 8.71 (dd, 2H), 8.52 (dd, 2H), 8.36 (m, 2H), 8.22 (m, 4H), 8.13 (m,
H), 7.90 (m, 4H), 7.60 (dd, 2H), 1.65 (s, 3H, methyl protons).
d
10.81 (d, 1H), 9.51 (s, 1H), 9.42 (s,
CuI (0.19 g, 1 mmol) dissolved in acetonitrile (30 ml) is added
2
1
4
dropwise into a 20 ml chloroform solution of the ligand L (0.338 g,
1 mmol) within 1 h. Then the reddish reaction mixture is stirred for
Scheme 1. Chemical structure of the ligands L1 and L2 used in this study.

J. Mondal et al. / Journal of Molecular Structure 1108 (2016) 315e324
317
another 1 h at room temperature. Deep red colored solid precipi-
tated out. It was filtered out and washed with 5 ml acetonitrile and
dried in vacuo. Yield: 5.177 g (72%). Deep red single crystals suitable
for X-ray analysis are obtained by careful layering of CuI (3.8 mg,
crystallographic data for the complexes are given in Table 1.
Selected coordination bond lengths, bond angles and non-covalent
interaction parameters are summarized in Tables 2e5.
0
.02 mmol) dissolved in acetonitrile (4 ml) onto a 4 ml chloroform
2.5. Computational details
2
solution of the ligand L (6.8 mg, 0.02 mmol). Anal. Calcd for C22
Cu : C 36.73, H 2.52, N 7.79; found: C 36.80, H 2.54, N 7.83.
H
18
N
4
2
I
2
The GAUSSIAN-09 Revision C.01 program package was used for
all calculations [41]. The gas phase geometries of the compounds
were fully optimized without any symmetry restrictions in singlet
ground state with the hybrid B3LYP [42,43] exchange-correlation
functional. Frequency calculations while optimizations of the
structures have no non-negative frequency, which implies that, the
structures obtained having true minima. Basis set 6e31þþG was
found to be suitable for the whole molecule.
ꢀ
1
FTIR cm (KBr): 3047(m), 2922(m), 1613(s), 1573(m), 1252(m),
234(s),1108(m), 994(m), 844(vs), 824(m), 767(s), 720(vs), 475(m),.
UVeVis (MeCN) [ max, nm]: 530, 350, 290.
1
l
2.4. Crystallographic data collection and refinement
Suitable single crystals of the complexes were mounted on a
Bruker SMART diffractometer equipped with a graphite mono-
chromator and Mo-K
were solved using Patterson method by using the SHELXS97. Sub-
sequent difference Fourier synthesis and least-square refinement
revealed the positions of the remaining non hydrogen atoms. Non-
hydrogen atoms were refined with independent anisotropic
displacement parameters. Hydrogen atoms were placed in ideal-
ized positions and their displacement parameters were fixed to be
a
(l
¼ 0.71073 Å) radiation. The structures
3. Result and discussions
3.1. Synthetic aspects
The Schiff-base ligand L1 was prepared in good yield by the
condensation of 1, 2-diaminopropane with 1-pyrinealdehyde in
1:2 M ratio in dry methanol maintaining dry condition throughout
1
1.2 times larger than those of the attached non-hydrogen atom.
the reaction. Reaction of CuI and diimine ligand L in 1:1 mol ratio
Successful convergence was indicated by the maximum shift/error
of 0.001 for the last cycle of the least squares refinement. All cal-
culations were carried out using SHELXS 97 [36], SHELXL 97 [37],
PLATON 99 [38], ORTEP-32 [39] and WinGX system Ver-1.64 [40].
Data collection and structure refinement parameters and
in room temperature yielded the brown red-coloured mono-nu-
2
clear complex 1. Ligand L is 1:2 condensate of ethylene diamine
1
and quinolone-2-carboxaldehyde. The ligand L contains two and
2
ligand L contains four N-sites suitable to coordinate to the metal
ions, and are conformationally flexible about the central saturated
Table 1
Summary of crystallographic data for complexes 1 and 2.
Complex 1
Complex 2
Formula
C
37
H
26 Cu I N
2
C
22
H
18 Cu
719.30
Monoclinic
P2 /n (No. 14)
2 2 4
I N
Formula Weight
Crystal System
Space group
a [Å]
689.04
Monoclinic
P2
15.765(3)
8.9392(17)
21.219(4)
108.696(4)
2832.5(9)
4
1
/c (No. 14)
1
9.1190(6)
17.2073(12)
14.4576(10)
96.996(1)
2251.7(3)
4
2.122
4.648
1368
b [Å]
c [Å]
ꢁ
b
[ ]
3
V [Å ]
Z
3
D(calc) [g/cm ]
(MoK ) [/mm ]
F(000)
1.616
1.891
1376
m
a
Crystal Size [mm]
Temperature (K)
0.08 ꢂ 0.10 ꢂ 0.12
0.06 ꢂ 0.08 x 0.10
293
293
Radiation [Å]
MoK
1.4; 25.3
a
0.71073
MoKa 0.71073
1.9; 28.8
ꢁ
q
Min-Max [ ]
Dataset
Total & Uniq. Data
R(int)
ꢀ18: 18; ꢀ10: 10; ꢀ25: 25
26344; 5114
0.044
ꢀ12: 11; ꢀ22: 22; ꢀ18: 18
24071, 5575
0.039
Observed data [I > 2.0
s(I)]
3819
4561
Nref, Npar
R
5114, 371
0.0529
5575, 271
0.0261
wR2
S
0.1420
1.07
0.0643
0.81
Max. and Av. Shift/Error
Min. & Max. Resd. Dens. [e/Å ]
0.00, 0.00
ꢀ1.54; 1.18
0.00, 0.00
ꢀ0.53, 0.69
3
w ¼ 1/[\s^2^(Fo^2^)þ(0.0545P)^2^þ7.0650P] where P¼(Fo^2^þ2Fc^2^)/3.
Table 2
ꢁ
Some selected coordination bond distances (Å) and bond angles ( ) of complex 1.
Experimental
Theoretical
Experimental
Theoretical
I1eCu2
Cu2eN2
I1eCu2eN2
2.4177(12)
2.050(6)
138.81(17)
2.44
2.03
137.6
Cu2eN1
I1eCu2eN1
N1eCu2eN2
2.047(8)
135.4(2)
84.0(3)
2.03
134.6
85.3

318
J. Mondal et al. / Journal of Molecular Structure 1108 (2016) 315e324
Table 3
All the
p/ interaction parameters of complex 1.
P
/
p
interactions
ꢁ
Ri/Rj
Distance between ring Centroids (Å)
Dihedral Angle between Planes I and J ( )
Symmetry
1-x, -y, 1-z
1-x, -y, 1-z
1-x, -y, 1-z
1-x, -y, 1-z
1-x, -y, 1-z
-x, -y, -z
R3/R5
R4/R5
R5/R3
R5/R4
R5/R5
R6/R6
R6/R8
R8/R6
3.706(4)
3.717(3)
3.705(4)
3.717(3)
3.634(3)
3.636(5)
3.984(4)
3.984(4)
2.3(3)
1.9(3)
2.3(3)
1.9(3)
0
0
1.9(4)
1.9(4)
-x, -y, -z
-x, -y, -z
CeH/p interactions
CeH/Ri
C2eH2/R9
C36eH36A/R5
ꢁ
H/Ri (Å)
2.66
2.66
<CeH/Ri ( )
153
153
Symmetry
1-x, ꢀ1/2 þ y, 1/2-z
1-x, ꢀ1/2 þ y, 1/2-z
*R3: C1- > C14- > C13- > C12- > C15- > C16->; R4: C5- > C6- > C7- > C8- > C15- > C16->; R5: C8- > C9- > C10- > C11- > C12- > C15->; R6: C19- > C20- > C21- > C31- > C22-
>
C27->; R7: C19- > C27- > C26- > C30- > C34- > C33->; R8: C22- > C23- > C24- > C25- > C26- > C27->; R9: C25- > C26- > C30- > C29- > C35- > C28->
CeC bond. In the presence of suitable metal ions, L1 and L2 can
adopt readily a different conformation about this bond in order to
arrange the nitrogen binding sites in a convergent manner and
optimize the metal-ligand coordination. The bright red homo-
dinuclear complex 2 is synthesised by the reaction of CuI with
the ligand L2 in 1:1 mol ratio at room temperature. Synthetic
procedure for complex 2 is given in Scheme 2. The complexes are
air-stable in solid state for at least 10 weeks. The solubility of the
complex 1 is better than the complex 2 in common solvents like
acetonitrile, dimethyl formamide and dimethyl sulphoxide. The
stability of the dissolved complexes 1 and 2 in air is one-week.
3
3
.2. Description of crystal structures
.2.1. Molecular and supramolecular structure of 1
Single crystal X-ray diffraction analysis reveals that complex 1 is
Table 4
ꢁ
Some selected coordination bond distances (Å) and bond angles ( ) of complex 2.
Experimental
Theoretical
Experimental
Theoretical
I1eCu3
I2eCu3
Cu3eN1
2.6513(5)
2.6078(5)
2.034(3)
2.64
2.62
2.02
I1eCu4
I2eCu4
Cu3eN2
2.5948(4)
2.6680(5)
2.102(3)
2.61
2.64
2.11
Cu4eN3
2.093(3)
2.07
Cu4eN4
2.035(2)
2.04
I1eCu3eI2
I1eCu3eN2
I2eCu3eN2
I1eCu4eI2
I1eCu4eN4
I2eCu4eN4
107.22(1)
122.49(7)
106.80(7)
107.10(1)
124.84(7)
111.70(7)
106.1
121.3
104.8
105.5
123.6
110.2
I1eCu3eN1
I2eCu3eN1
N1eCu3eN2
I1eCu4eN3
I2eCu4eN3
N3eCu4eN4
115.46(7)
122.88(7)
80.69(10)
116.95(7)
113.99(7)
80.54(10)
116.3
121.1
79.6
114.8
110.7
78.9
Table 5
All the
p/ interaction parameters of complex 2.
p
/
p
interactions
ꢁ
Ri/Rj
Distance between ring centroids (Å)
Dihedral angle between planes I and J ( )
Symmetry
R4/R4
R4/R5
R4/R6
R5/R4
R5/R5
R5/R7
R6/R4
R7/R5
3.7101(16)
3.6736(16)
3.7186(17)
3.6736(16)
3.6916(16)
3.5827(16)
3.7186(17)
3.5828(16)
0
1-x, ey, 1-z
16.24(13)
2.37(14)
16.24(13)
0
3.33(13)
2.37(14)
3.33(13)
3/2-x, ꢀ1/2 þ y, 1/2-z
1-x, ey, 1-z
3/2-x, 1/2 þ y, 1/2-z
2-x, 1-y, 1-z
2-x, 1-y, 1-z
1-x, ey, 1-z
2-x, 1-y, 1-z
*R4: N1- > C2- > C1- > C18- > C4- > C3->; R5: N4- > C8- > C9- > C10- > C11- > C12->; R6: C3- > C4- > C19- > C20- > C21- > C22->; R7: C11- > C12- > C13- > C14- > C15-
>
C16->
Scheme 2. Synthetic route of the ligand L2 and the complex 2.

J. Mondal et al. / Journal of Molecular Structure 1108 (2016) 315e324
319
Fig. 1. ORTEP diagram of complex 1.
þ
a monomeric metal-organic structure of Cu(I) and crystallizes in
1
achiral P2 /n space group. Each asymmetric unit contains two Cu
þ
2
achiral P2
1
/c space group. Each asymmetric unit contains one Cu
ions, one neutral tetra-dentate ligand (L ) and two bridging iodide
ions (I ). The ORTEP diagram of the asymmetric unit is shown in
Fig. 4. Two Cu ions are bridged by two iodides with formation of
} unit and one bis-bidentate ligand (L ). Some selected bond
lengths and bond angles are given in Table 4. Each Cu atom is four
coordinated with distorted tetrahedral geometry. For the Cu3 atom,
1
ꢀ
ion, one neutral bidentate ligand (L ) and one coordinating iodide
ꢀ
I
ion (I ). The ORTEP diagram of the asymmetric unit is shown in
{CuI
I
2
Fig. 1. Some selected bond lengths and bond angles are given in
Table 2. Each Cu atom is tri-coordinated (N1, N2 and I1) and shows
almost triangular planar geometry. For the Cu2 atom, N1 and N2
2
2
1
2
atoms of the ligand (L ) and the one iodide form the coordination
N1 and N2 atoms of the ligand (L ) and the two iodides (I1 and I2)
sphere. The CueN bond distances vary in the range of 2.047(8) e
form the coordination sphere while for Cu4 atom N3 and N4 atoms
of the ligand (L ) and the same two iodides (I1 and I2) are at the
2
2
.050(6) Å and CueI bond distance is 2.4177(12) Å.
Supramolecular interactions connect the monomeric units
to form 2D supramolecular layer structure, as shown in Fig. 2.
CeH/ interactions bridge these 2D supramolecular polymers to
p
/p
coordination sphere. The CueN bond distances vary in the range of
2.034(3)-2.102(3) Å and CueI bond distances vary in the range of
2
p
2.5948(4) - 2.6680(5) Å. The bis-bidentate di-imine ligand (L )
form 3D supramolecular framework in Fig. 3. All the
teractions are summarized in Table 3.
p
/ in-
binds two metal centres and the two iodides act as a m-2-bridging
ligand. The CueCu distance within this dimeric complex is 2.486 Å,
which is comparable with those found in other copper(I) dimeric
complexes.
3
.2.2. Molecular and supramolecular structure of complex 2
Single crystal X-ray diffraction analysis reveals that complex 2 is
a di-meric 0D metal-organic structure of Cu(I) and crystallizes in
Supramolecular
to form 3D supramolecular structure, Fig. 5. All the
p
/
p
interactions connect the monomeric units
/ interactions
p
Fig. 2. 2D supramolecular sheet structure formed by
p/p interactions of complex 1.

320
J. Mondal et al. / Journal of Molecular Structure 1108 (2016) 315e324
Fig. 3. 3D supramolecular structure formed by both
p/p and CeH/p interactions in complex 1.
are summarized in Table 5.
3.3. IR spectroscopy
The complexation processes of the ligands have been monitored
by IR spectroscopy. The IR spectrum of the ligand L and L show
1
2
3
.2.3. Comparison between the calculated and experimental data
We have compared our calculated bond distances and bond
ꢀ
1
1
characteristic bands at, 1637 and 1583 cm (for L ) and 1642 and
ꢀ1
2
angles of complexes 1 and 2, with those obtained from X-ray single
crystal data. These data have been tabulated in Tables 2 and 4. From
the comparison it is clear that calculated bond distances and bond
angles of complexes 1 and 2 are in good agreement with the
experimental data. The difference for particular bond using
experimental and calculated value lies within 0.028Åe0.01 Å and
1600 cm (for L ) which we assign to the pyridine/quinoline ring
and imine C]N stretching frequencies respectively. For the Cu(I)
complexes these bands appear at 1613 and 1599 cm (for 1); 1613
and 1573 cm (for 2). The IR stretching frequency of CH group of
the ligand L appears at 715 cm and that of the complex 2 appears
ꢀ
1
ꢀ
1
3
2
ꢀ1
ꢀ
1
at 720 cm
.
ꢁ
ꢁ
difference in bond angle lies within 1 e3.2 .
Fig. 4. ORTEP diagram of complex 2.

J. Mondal et al. / Journal of Molecular Structure 1108 (2016) 315e324
321
Fig. 5. 3D supramolecular structure of the complex 2.
3
.4. Photoluminescence properties
complexes (Fig. 8). Theoretical analysis reveals that HOMOs are
focused on the Cu and Iodide and the LUMOs are focused on di-
imine ligands.
The emission spectra of both complexes were studied in solid
state at room temperature. The complex 1 shows emission maxima
at ca. 435 nm with shoulder at ca. 481 nm (Fig. 6) upon excitation at
So, it can be concluded that for complex 1 the emission spectra
is produced due to charge transfer from CueI core to the bidentate
ligand and for complex 2 the emission spectra is produced due to
2
90 nm. The complex 2 shows emission maxima at ca. 422 nm with
shoulders at ca. 398 nm and ca. 460 nm (Fig. 7) upon excitation at
90 nm. To gain insight into the photophysical properties of the
charge transfer from the {Cu
2
(m-I)
2
} core to the bis-bidentate ligand,
2
2 2
similar to the complexes with {Cu X } diamond cores with di-imine
ligands.
complexes, we have optimized the structures at ground state of
these complexes, using DFT method. This calculations may be
instructive to analyze the highest occupied molecular orbital
(
HOMO) and lowest unoccupied molecular orbital (LUMO) of the
Fig. 6. Photoluminescence spectra of complex 1.
Fig. 7. Photoluminescence spectra of complex 2.

322
J. Mondal et al. / Journal of Molecular Structure 1108 (2016) 315e324
Fig. 8. HOMO and LUMO of the complexes 1 and 2.
Scheme 3. 1 and 2 catalysed synthesis of 1,3-Benzoxazole.
Table 6
Synthesis of 2-aryl 1,3-benzoxazole.
ꢁ
Entry
Ar-CHO
Time (min)
21
Product
Complex
Yield (%)
Melting point
Observed
C
Ref.
54
Reported
1.
1a
1
2
48
52
110e113
112e114
2.
3.
4.
5.
19
16
22
25
1b
1c
1d
1e
1
2
62
63
129e131
113e116
285e287
103e106
130e131
114e116
287e289
102e104
55
54
56
54
1
2
69
69
1
2
73
76
1
2
65
64
3
.5. Catalytic activity
heterocycles with a diverse spectrum of biological properties [44].
More particularly, 2-substituted benzoxazoles are of great interest
owing to their potent utility as antirheumatic agent [45], H37Rv
inhibitor [46], elastase inhibitor [47,48] HT3 receptor agonist [49],
Cu(I)-complexes-catalyzed cyclopropanation of alkenes has
attracted enormous research interest. Benzoxazoles are a class of

J. Mondal et al. / Journal of Molecular Structure 1108 (2016) 315e324
323
cytotoxic compound toward P338 cell [50] and chemiluminescent
agents [51]. Moreover, benzoxazoles derivatives are isosteres of
naturally occurring cyclic nucleotides and they interact with the
biopolymers of organisms [52]. This broad utility has prompted
significant efforts toward the synthesis of these heterocycles
and 1405109 respectively. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html.
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I
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[
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2
1
[
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[
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