A. Parween et al. / Polyhedron 99 (2015) 34–46
35
3
stabilised conjugate base through intramolecular hydrogen bond-
ing between phenolic-OH and imidazole-N.
1-(4,5-Diphenyl-1H-imidazol-2-yl)naphthalene-2-ol (L H): 1-
(4,5-diphenyl-1H-imidazol-2 yl)naphthalene-2-ol was synthesized
by the reaction of Benzil (1.05 g, 5 mmol), 2-Hydroxy-1-
napthaldeyde (0.86 g, 5 mmol) and Ammonium Acetate (7.70 g,
2
. Experimental
1
(
00 mmol) in 5 ml acetic acid. A light yellow colored precipitate
L H) was prepared by similar procedure as for, ligand (L H).
Yield: (1.3 g) 72%, NMR ( H, 500 MHz, CDCl3): d 7.26–7.63 (m,
3
1
2.1. Materials
1
1
3H, ArH), 7.79 (d, 1H, ArH), 7.86 (d, 1H, ArH), 8.21 (d, 1H, ArH);
All reagents and chemicals were purchased from commercial
Elemental Anal. Calc. for C25
Found: C, 82.51; H, 4.98; N, 7.68%. IR (KBr, cm ):
2
H
18
N
2
O: C, 82.85; H, 5.01; N, 7.73.
sources like E. Merck, Fluka and Aldrich and used without further
purification. HPLC grade MeCN, DMF, DMSO and DCM were used
for spectroscopic and electrochemical studies. All solvents were
A.R. grade and used as received for synthetic work. Tetra ethyl
ammonium perchlorate (TEAP), used for the electrochemical stud-
ies was prepared according to the literature [19].
ꢃ1
m 3246, 3053,
663, 1707, 1589, 1479, 1334, 1249, 758, 699. MS: m/z 363 {M+1}.
2.4. Synthesis of the complexes
2
General procedure for the synthesis of [Cu(L) ] compounds
The 2 equivalent of prepared ligand was completely dissolved in
methanol. 2 equivalent of Et N were added followed by 1 equiva-
lent of Cu(ClO O. The reaction mixture was refluxed for 5 h
3
2
.2. Physical measurements
4
) ꢀ6H
2 2
and the product was isolated and purified according to the partic-
Elemental analyses were performed on an Elementar Vario EL III
ular procedure described below.
C, H, N, S & O analyzer. Infrared spectra were recorded as KBr
pellets on a Shimadzu IR-Prestige21 spectrometer. Electronic spec-
tra were recorded on
Spectrophotometer. To determine the pK
and complexes, a series of DMF–aqueous buffer (Robinson–
1
[Cu(L H)
2
]
(1): Cu(ClO
4
)
2
2
ꢀ6H O
(185.2 mg, 0.5 mmol) in
1
MeOH (10 ml) and L H (312 mg, 1 mmol) in MeOH (15 ml) were
reacted as described above. A brown precipitate of complex 1
was washed by methanol and ether, finally dried in vacuum.
Yield: (205.8 mg) 60%; Elemental Anal. Calc. for Cu-C42H32N O : C,
a
Perkin Elmer Lambda 750
value of the ligands
a
ꢃ5
4
2
Britton) solution (1:1) of 7.5 ꢂ 10 M of analyte having different
7
3.29; H, 4.69; N, 8.14. Found: C, 73.28; H, 4.13; N, 7.42%. IR
pH (range 3–13) were prepared for spectrophotometric titration.
The pH values were measured in a Thermo Scientific Orion 4 star
pH Benchtop.
ꢃ1
(
KBr, cm ):
m
3057, 1604, 1479, 1315, 1255, 769, 696. MS: m/z
ꢃ1
ꢃ1
7
08 {M+Na}, 686 {M+}. UV–Vis (DMF): kmax/nm (e/M cm ):
2
90 (49818), 320 (61678), 364sh (12545), 490 (643), 716 (310).
Electrochemical measurements of all the ligands and complexes
2
[Cu(L H)
2
] (2): Cu(ClO
4
)
2
2
ꢀ6H O (185.2 mg, 0.5 mmol) in MeOH
were recorded in the presence of different pH in DMF:H
containing 0.1 M TEAP as supporting electrolyte, using
CHI6003E potentiostat, glassy carbon working electrode, Pt wire
2
O (8:2)
2
(
10 ml) and L H (391 mg, 1 mmol) in MeOH (15 ml) were reacted
a
as described above. A brown precipitate of complex 2 was washed
by methanol and ether, finally dried in vacuum. Yield: (286.2 mg)
68%; single crystals, suitable for X-ray crystallography was
obtained from DMF solution. Elemental Anal. Calc. for Cu-
as a counter electrode and Ag/AgCl non aqueous reference elec-
trode. The ferrocene/ferrocenium couple was observed at E0
(D
Ep) = 0.4 V (100 mV) under these experimental conditions.
1
C42H30Br N O : C, 59.62; H, 3.57; N, 6.62. Found: C, 59.31; H,
2
4 2
H NMR spectra were recorded on a Bruker AVANCE DPX
ꢃ1
3
.51; N, 6.14%. IR (KBr, cm ):
m 3055, 2868, 1596, 1477, 1301,
5
3 4
00 MHz spectrometer using, Si(CH ) as internal standard. ESI-
1
251, 815, 771, 696. MS: m/z 843 {M+}. UV–Vis (DMF): kmax/nm
/M cm ): 296 (29773), 335 (24322), 344 (26785), 374sh
MS spectra of the samples were recorded on JEOL JMS 600
instrument.
ꢃ1
ꢃ1
(e
(
14588), 500 (752), 712 (378).
2.3. Synthesis of the ligands
Table 1
Crystal data and details of the structure determination for 2ꢀDMF.
1
2
-(4,5-Diphenyl-1H-imidazol-2-yl)phenol (L H): 2-(4,5-diphe-
nyl-1H-imidazol-2 yl)phenol was synthesized by the reaction of
Benzil (1.05 g, 5 mmol), Salicylaldehyde (0.61 g, 5 mmol) and
Ammonium Acetate (7.70 g, 100 mmol) in 5 ml acetic acid. The
reaction mixture was refluxed for 4 h. A white color precipitate
L H) obtained, it was filtered in vacuum, washed with distilled
Empirical formula
Formula weight
Crystal system
Crystal size (mm)
Space group
a (Å)
C
42
H
28Br
917.14
monoclinic
0.32 ꢂ 0.09 ꢂ 0.01
P2 /c
2 4 2 3 7
CuN O , C H NO
1
1
(
18.8571(13)
15.9999(11)
13.3625(8)
90
96.2360(10)
90
b (Å)
c (Å)
water (4 ꢂ 5 ml) and dried at room temperature.
1
Yield: (0.96 g) 62%, NMR ( H, 500 MHz, CDCl
3
): d 12.72 (s, 1H,
a
(°)
b (°)
(°)
N-H), 9.37 (s, 1H, O-H), 6.90–7.47 (m, 14H, ArH); Elemental Anal.
Calc. for C21
H, 5.73; N, 8.13%. IR (KBr, cm ):
261, 763, 692. MS: m/z 313 {M+1}.
4
H
16
N
2
O: C, 80.75; H, 5.16; N, 8.97. Found: C, 79.60;
c
ꢃ1
3
m
3201, 3057, 1593, 1492, 1381,
Cell volume (Å )
4007.8(5)
4
Z
1
2
T (K)
100(1)
-Bromo 2-(4,5-diphenyl-1H-imidazol-2-yl)phenol (L H): 4-
Bromo 2-(4,5-diphenyl-1H-imidazol-2-yl)phenol was synthesized
by the reaction of Benzil (1.05 g, 5 mmol), 5-Br-Salicyaldeyde
F(000)
1852
2.526
ꢃ1
l
(mm
)
h range (°)
Reflection collected
1.09–30.54
48695
(
5
1.00 g, 5 mmol) and Ammonium Acetate (7.70 g, 100 mmol) in
2
Reflections unique
12079
ml acetic acid. A white colored precipitate (L H) was prepared
R
GOF
int
0.1425
0.976
1
by similar procedure as for, ligand (L H).
1
Yield: (1.38 g) 71%, NMR ( H, 500 MHz, CDCl
3
): d 6.949 (d, 1H,
Refl. obs. (I > 2
r
(I))
5103
ArH), 7.260–7.770 (m, 11H, ArH), 7.78 (m, 1H, ArH); Elemental
Parameters
507
wR
R value (I > 2
Largest diff. peak and hole (e
2
(all data)
0.1456
0.0239
ꢃ1.183; 1.237
Anal. Calc. for C21
H
15BrN
2
O: C, 64.46; H, 3.86; N, 7.16. Found: C,
ꢃ1
r(I))
6
1
4.06; H, 3.22; N, 6.91%. IR (KBr, cm ):
m
3195, 3057, 1577,
ꢃ
ꢃ3
Å
)
487, 1371, 1251, 810, 769, 696. MS: m/z 391 {M+}.