Synthesis, spectral characterization, properties and structures of copper(I) complexes containing novel bidentate iminopyridine ligands

Article abstract of DOI:10.1016/j.poly.2006.08.011

Four new ligands, (4-methyl-phenyl)-pyridin-2-ylmethylene-amine (A), (2,3-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (B), (2,4-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (C) and (2,5-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (D), and their correspo

Full text of DOI:10.1016/j.poly.2006.08.011

Polyhedron 26 (2007) 154–162
www.elsevier.com/locate/poly
Synthesis, spectral characterization, properties and structures of
copper(I) complexes containing novel bidentate
iminopyridine ligands
a,
b
b
c
Saeed Dehghanpour *, Nouri Bouslimani , Richard Welter , Fresia Mojahed
a
Department of Chemistry, Alzahra University, P.O. Box 1993891176, Tehran, Iran
Laboratoire DECOMET, LC003 7177 CNRS-ULP, Louis Pasteur University, Strasbourg I, F-67070 Strasbourg Cedex, France
b
c
Department of Chemistry, Faculty of Science, Tarbiat Modares University, P.O. Box 14115-175, Tehran, Iran
Received 4 July 2006; accepted 7 August 2006
Available online 18 August 2006
Abstract
Four new ligands, (4-methyl-phenyl)-pyridin-2-ylmethylene-amine (A), (2,3-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (B),
(2,4-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (C) and (2,5-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (D), and their corre-
sponding copper(I) complexes, [Cu(A)2]ClO4 (1a), [Cu(B)2]ClO4 (1b), [Cu(C)2]ClO4 (1c), [Cu(D)2]ClO4 (1d), [Cu(A)(PPh3)2]ClO4 (2a),
[Cu(B)(PPh3)2]ClO4 (2b), [Cu(C)(PPh3)2]ClO4 (2c) and [Cu(D)(PPh3)2]ClO4 (2d), have been synthesized and characterized by CHN anal-
yses, 1H and 13C NMR, IR and UV–Vis spectroscopy. The crystal structures of [Cu(B)2]ClO4 (1b), [Cu(C)2]ClO4 (1c) and
[Cu(A)(PPh3)2]ClO4 Æ 1/2CH3CN (2a) were determined from single crystal X-ray diffraction. The coordination polyhedron about the
copper(I) center in the three complexes is best described as a distorted tetrahedron. A quasireversible redox behavior is observed for
the complexes.
Ó 2006 Elsevier Ltd. All rights reserved.
Keywords: 2-Pyridinecarbaldehyde; Diimine ligands; Copper(I) complexes; Distorted tetrahedral structure
1. Introduction
designed ligand are the most important prerequisites for
the stability of copper(I) complexes and their redox, photo-
physical and photochemical behavior [13–16].
Although the coordination chemistry of symmetrical
chelating diimines [e.g., 2,2-bipyridine, 1,10-phenanthro-
line and 2,9-dimethyl-1,10-phenanthroline] with copper(I)
has been extensively studied [9,17–20], there are few data
on complexes with unsymmetrical diimine ligands contain-
ing iminopyridine [21–26].
In a continuation of our work on the preparation of
copper(I) diimine complexes with low lying MLCT transi-
tions [27–29], here we report the synthesis and characteriza-
tion of four ligands with extended conjugation, and their
copper(I) complexes (Fig. 1). The structures, spectral prop-
erties and redox chemistry of these complexes are also
discussed.
Monovalent copper (d10) chemistry has drawn special
attention because of its instability, unusual structural fea-
tures, utility in solar energy and supramolecular devices,
catalytic activity in photoredox reactions and the biological
relevance of high potential copper complexes [1–8]. Most
of the studies have been on four-coordinated tetrahedral
Cu(I) complexes of the type [Cu(LL)2]+ or [Cu(LL)(P)2]+
where LL is a diimine and P is a phosphine, because of
interdependence of their coordination geometry and their
redox and photochemical behavior [9–12]. Recent reports
have indicated that steric crowding and p-acidity in a well
*
Corresponding author. Tel./fax: +98 21 88041344.
E-mail address: dehghanpour_farasha@yahoo.com (S. Dehghanpour).
0277-5387/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.08.011

S. Dehghanpour et al. / Polyhedron 26 (2007) 154–162
155
2.2. Synthesis
H3
H2
H1
H4
R2
R4
R1
H5
N
2.2.1. (4-Methyl-phenyl)-pyridin-2-ylmethylene-amine (A)
N
R3
To a solution of pyridine-2-carbaldehyde (107 mg,
1 mmol) in 10 ml diethylether was added a solution of 4-
methylaniline (107 mg, 1 mmol) in 10 ml diethylether and
the resulting mixture was stirred for 2 h. The ligand
(4-methyl-phenyl)-pyridin-2-ylmethylene-amine was obta-
ined as a white microcrystalline precipitate. It was then fil-
tered off, washed with cold diethylether, and dried in air.
Ligand
R1
H
R2
R3
R4
H
A
B
C
D
H
CH3
H
CH3
H
Yield: 172 mg (90%). IR (KBr): 1623 cmꢀ1 m(C@N). H
1
CH3
CH3
CH3
H
NMR (500 MHz, CDCl3): 2.31 (s, 6H, 2CH3), 6.85–7.15
(m, 3H, ArH, amine ring), 7.32 (dd, 1H, JH1,2 = 4.75,
JH2,3 = 7.50, H2), 7.79 (t, 1H, JH3,2 = 7.50, JH3,4 = 7.75,
H3), 8.19 (d, 1H, JH4,3 = 7.75, H4), 8.62 (s, 1H, H5), 8.69
(d, 1H, JH2,1 = 4.75, H1). 13C {1H} NMR (500 MHz,
CDCl3): 21.04 (13CH3), 121.12, 121.74, 124.91, 129.85,
136.54, 136.69, 148.37, 149.63, 154.77, 159.62 (13C@N).
Anal. Calc. for C13H12N2: C, 79.56; H, 6.16; N, 14.27.
Found: C, 79.55; H, 6.17; N, 14.28%.
CH3
H
H
H
CH3
[CuL2]ClO4
Complex Ligand (L)
[CuL(PPh3)2]ClO4
Complex Ligand (L)
1a
1b
1c
1d
A
B
C
D
2a
2b
2c
2d
A
B
C
D
2.2.2. (2,3-Dimethyl-phenyl)-pyridin-2-ylmethylene-amine
(B)
This ligand was prepared by a procedure similar to 1
using 121 mg (1 mmol) of 2,3-dimethylaniline. Yield:
1
190 mg (90%). IR (KBr): 1630 cmꢀ1 m(C@N). H NMR
(500 MHz, CDCl3): 2.31 (s, 6H, 2CH3), 6.85–7.15 (m,
3H, ArH, amine ring), 7.32 (dd, 1H, JH1,2 = 4.12,
JH2,3 = 7.30, H2), 7.76 (t, 1H, JH3,2 = 7.30, JH3,4 = 7.90,
H3), 8.24 (d, 1H, JH4,3 = 7.90, H4), 8.50 (s, 1H, H5), 8.68
(d, 1H, JH2,1 = 4.12, H1). 13C {1H} NMR (500 MHz,
CDCl3): 13.90 (3-13CH3), 21.12 (2-13CH3), 115.43, 121.62,
124.98, 126.16, 127.98, 130.77, 136.58, 137.56, 149.56,
150.10, 155.01, 159.77 (13C@N). Anal. Calc. for
C14H14N2: C, 79.97; H, 6.71; N, 13.32. Found: C, 79.99;
H, 6.70; N, 13.35%.
Fig. 1. Chemical formula of ligands (A–D), and Cu(I) complexes 1a–2d.
2. Experimental
2.1. General
Caution! Perchlorate salts of metal complexes with
organic ligands are potentially explosive and should be
handled with care.
All chemicals used were reagent grade and used as
received. Solvents used for the reactions were purified by
literature methods [30]. [Cu(CH3CN)4]ClO4 was prepared
according to the literature procedure [31].
2.2.3. (2,4-Dimethyl-phenyl)-pyridin-2-ylmethylene-amine
(C)
This ligand was prepared by a procedure similar to 1
using 121 mg (1 mmol) of 2,4-dimethylaniline. Yield:
1
185 mg (88%). IR (KBr): 1629 cmꢀ1 m(C@N). H NMR
Elemental analyses were performed by using a Heraeus
CHN-O-RAPID elemental analyzer. Infrared spectra were
recorded on a Bruker Tensor 27 instrument. Electronic
absorption spectra were recorded on a JASCO V-570 spec-
trophotometer; kmax (loge). NMR spectra were obtained
on a BRUKER AVANCE DRX500 (500 MHz) spectrom-
eter. Proton chemical shifts are reported in part per million
(ppm) relative to an internal standard of Me4Si. All vol-
tammograms were recorded with a three electrodes system
consisting of an Ag/AgCl reference electrode, a platinum
wire counter electrode, and Au as a working electrode. A
Metrohm multipurpose instrument model 693 VA proces-
sor with 694A Va stand was used. In all electrochemical
experiments the test solution was purged with argon gas
for at least 5 min.
(CDCl3; d): 2.33 (s, 3H, 4-CH3), 2.37 (s, 3H, 2-CH3),
6.93–7.05 (m, 3H, ArH, amine ring), 7.33 (dd, 1H,
JH1,2 = 4.5, JH2,3 = 7.50, H2), 7.76 (t, 1H, JH3,2 = 7.50,
JH3,4 = 8.00, H3), 8.24 (d, 1H, JH4,3 = 8.00, H4), 8.50 (s,
1H, H5), 8.68 (d, 1H, JH2,1 = 4.12, H1). 13C {1H} NMR
(500 MHz, CDCl3): 17.78 (4-13CH3), 20.96 (2-13CH3),
117.28, 121.54, 124.86, 127.3, 131.21, 132.49, 136.26,
136.55, 147.43, 149.53, 155.08, 159.03 (13C@N). Anal. Calc.
for C14H14N2: C, 79.97; H, 6.71; N, 13.32. Found: C, 79.96;
H, 6.70; N, 13.35%.
2.2.4. (2,5-Dimethyl-phenyl)-pyridin-2-ylmethylene-amine
(D)
This ligand was prepared by a procedure similar to 1
using 121 mg (1 mmol) of 2,5-dimethylaniline. Yield:

156
S. Dehghanpour et al. / Polyhedron 26 (2007) 154–162
1
200 mg (95%). IR (KBr): 1629 cmꢀ1 m(C@N). H NMR
(CDCl3; d): 2.34 (s, 3H, 2CH3), 6.83–7.13 (m, 3H, ArH,
amine ring), 7.34 (dd, 1H, JH1,2 = 4.8, JH2,3 = 7.65, H2),
7.79 (t, 1H, JH3,2 = 7.65, JH3,4 = 7.90, H3), 8.24 (d, 1H,
JH4,3 = 7.90, H4), 8.50 (s, 1H, H5), 8.69 (d, 1H,
JH2,1 = 4.80, H1). 13C {1H} NMR (500 MHz, CDCl3):
17.70 (5-13CH3), 20.99 (2-13CH3), 118.31, 121.57, 124.97,
127.09, 129.08, 130.25, 136.35, 136.60, 149.50, 149.92,
154.91, 159.59 (13C@N). Anal. Calc. for C14H14N2: C,
79.97; H, 6.71; N, 13.32. Found: C, 79.96; H, 6.70; N,
13.34%.
(s, 1H, H5). 13C {1H} NMR (500 MHz, CDCl3): 17.80
(4-13CH3), 20.90 (2-13CH3), 120.54, 127.65, 128.14, 128.88,
130.57, 131.66, 137.67, 138.53, 154.52, 149.21, 150.47,
159.91 (13C@N). Anal. Calc. for C28H28ClCuN4O4: C,
57.63; H, 4.84; N, 9.60. Found: C, 57.62; H, 4.85; N, 9.59%.
2.2.8. [CuI(D)2]ClO4 (1d)
This complex was prepared by a procedure similar to 1a
using 21 mg (0.1 mmol) of (2,5-dimethyl-phenyl)-pyridin-2-
ylmethylene-amine, D. Dark-red crystals were collected by
filtration and dried in vacuo. Yield: 26 mg (89%). IR (KBr):
1590 cmꢀ1 m(C@N), 1091 cmꢀ1 m(Cl–O). 1H NMR (CDCl3;
d): 2.05 (s, 3H, 3-CH3), 2.12 (s, 3H, 2-CH3), 6.50–7.16 (m,
3H, ArH, amine ring), 7.65 (t, 1H, H2), 7.99–8.10 (m, 2H,
2.2.5. [CuI(A)2]ClO4 (1a)
To a stirring solution of (4-methyl-phenyl)-pyridin-2-
ylmethylene-amine, A (19.6 mg, 0.1 mmol) in 5 ml acetoni-
trile was added [Cu(CH3CN)4]ClO4 (16.4 mg, 0.05 mmol)
in 5 ml acetonitrile and the resulting mixture was stirred
for 10 min. The solution turned dark red rapidly. The vol-
ume of the solvent was reduced under vacuum to about
4 ml. The diffusion of diethyl ether vapor into the concen-
trated solution gave dark-red crystals. The resulting
crystals were filtered off, washed with a mixture of diethy-
lether–acetonitrile (9:1 v/v), and dried under vacuum.
Yield: 25 mg (92%). IR (KBr): 1582 cmꢀ1 m(C@N),
1090 cmꢀ1 m(Cl–O). 1H NMR (CDCl3; d): 2.28 (s, 3H,
CH3), 7.09–7.40 (m, 4H, ArH, amine ring), 7.60 (t, 1H,
H2), 8.04–8.21 (m, 2H, H3, H4), 8.48 (d, 1H, JH2,1 = 4.0,
H1), 9.20 (s, 1H, H5). 13C {1H} NMR (500 MHz, CDCl3):
21.10 (13CH3), 118.21, 122.48, 123.49, 128.60, 130.40,
131.25, 138.47, 139.93, 144.05, 149.09, 151.28, 156.28
(13C@N). Anal. Calc. for C26H24ClCuN4O4: C, 56.22; H,
4.35; N, 10.09. Found: C, 56.23; H, 4.34; N, 10.10%.
H3, H4), 8.59 (s, 1H, H5), 8.68 (d, 1H, JH2,1 = 4.5, H1). 13
C
{1H} NMR (500 MHz, CDCl3): 13.85 (5-13CH3), 20.10
(2-13CH3), 116.86, 122.21, 125.98, 126.18, 128.17, 131.70,
135.49, 139.01, 151.10, 153.99, 156.88, 160.00 (13C@N).
Anal. Calc. for C28H28ClCuN4O4: C, 57.63; H, 4.84; N,
9.60. Found: C, 57.62; H, 4.83; N, 9.59%.
2.2.9. [CuI(A)(PPh3)2]ClO4 (2a)
To a 3 ml MeCN solution of [Cu(CH3CN)4]ClO4
(32.8 mg, 0.1 mmol), 2 equivalent of Ph3P (52.2 mg,
0.2 mmol) were added, and the solution was stirred for
15 min. The solvent was evaporated under vacuum at room
temperature. The dry product [Cu(CH3CN)2(PPh3)2]ClO4
was added to a stirring solution of 19.6 mg (0.1 mmol)
pyridin-2-ylmethylene-p-tolyl-amine, A, in 3 ml MeCN.
The solution rapidly turned yellow and it was stirred for
20 min at room temperature. The reaction medium was
concentrated under vacuum, until the first crystals
appeared in the liquid phase. Bright-yellow crystals were
obtained by diffusion of Et2O vapor into the concentrated
solution. Yield: 80 mg (91%). IR (KBr): 1580 cmꢀ1
m(C@N), 1092 cmꢀ1 m(Cl–O), 1H NMR (500 MHz, CDCl3):
1H NMR (CDCl3; d): 2.33 (s, 3H, CH3), 6.96–7.40 (m,
35H, ArH, amine ring, PPh3), 8.04 (m, 2H, H3, H4), 8.38
(d, 1H, JH2,1 = 7.5, H1), 9.01 (s, 1H, H5). 13C {1H} NMR
(500 MHz, CDCl3): 21.1 (13CH3), 122.71, 126.25, 127.59,
128.32 (d, J = 4.2, ipso-C of PPh3), 128.94, 130.04,
130.32, 133.15, 138.48, 139.55, 148.70, 149.12, 150.12,
162.69 (13C@N). Anal. Calc. for C49H42ClCuN2O4P2: C,
66.59; H, 4.79; N, 3.17. Found: C, 66.58; H, 4.80; N, 3.16%.
2.2.6. [CuI(B)2]ClO4 (1b)
This complex was prepared by a procedure similar to 1a
using 21 mg (0.1 mmol) of (2,3-dimethyl-phenyl)-pyridin-2-
ylmethylene-amine, B. Dark-red crystals were collected by
filtration and dried in vacuo. Yield: 27 mg (93%). IR (KBr):
1578 cmꢀ1 m(C@N), 1095 cmꢀ1 m(Cl–O). 1H NMR (CDCl3;
d): 2.03 (s, 3H, 3-CH3), 2.22 (s, 3H, 2-CH3), 6.58–7.06 (m,
3H, ArH, amine ring), 7.74 (t, 1H, H2), 7.98–8.12 (m, 2H,
H3, H4), 8.59 (s, 1H, H5), 8.65 (d, 1H, JH2,1 = 4.5, H1). 13
C
{1H} NMR (500 MHz, CDCl3): 14.90 (3-13CH3), 20.12
(2-13CH3), 116.52, 122.01, 126.98, 127.14, 128.08, 132.78,
136.58, 138.56, 150.50, 154.12, 156.32, 159.90 (13C@N).
Anal. Calc. for C28H28ClCuN4O4: C, 57.63; H, 4.84; N,
9.60. Found: C, 57.62; H, 4.86; N, 9.61%.
2.2.10. [CuI(B)(PPh3)2]ClO4 (2b)
This complex was prepared by a procedure similar to 1
using 21 mg (1 mmol) of (2,3-dimethyl-phenyl)-pyridin-2-
ylmethylene-amine, B. Yellow-orange crystals were col-
lected by filtration and dried in vacuo. Yield: 70 mg
(79%). IR (KBr): 1591 cmꢀ1 m(C@N), 1088 cmꢀ1 m(Cl–O),
2.2.7. [CuI(C)2]ClO4 (1c)
This complex was prepared by a procedure similar to 1a
using 21 mg (0.1 mmol) of (2,4-dimethyl-phenyl)-pyridin-
2-ylmethylene-amine, C. Dark-red crystals were collected
by filtration and dried in vacuo. Yield: 25 mg (86%). IR
1
1H NMR (500 MHz, CDCl3): H NMR (CDCl3; d): 1.55
(s, 3H, CH3), 2.17 (s, 3H, CH3), 6.74–7.39 (m, 34H, ArH,
amine ring, PPh3), 7.53 (t, 1H, H2), 8.23 (m, 2H, H3, H4),
8.42 (d, 1H, JH2,1 = 7.75, H1), 8.60 (s, 1H, H5). 13C {1H}
NMR (500 MHz, CDCl3): 14.12 (4-13CH3), 21.1
(2-13CH3), 119.45, 126.02, 127.50, 128.47 (d, J = 4.2,
1
(KBr): 1585 cmꢀ1 m(C@N), 1090 cmꢀ1 m(Cl–O). H NMR
(CDCl3; d): 2.09 (s, 3H, 4-CH3), 2.28 (s, 3H, 2-CH3), 6.69-
6.91 (m, 3H, ArH, amine ring), 7.68 (t, 1H, H2), 8.01–8.11
(m, 2H, H3, H4), 8.54 (d, 1H, JH2,1 = 4.75, H1), 8.60

S. Dehghanpour et al. / Polyhedron 26 (2007) 154–162
157
1
ipso-C of PPh3), 128.94, 130.24, 130.38, 133.14, 138.57,
139.87, 148.77, 149.66, 150.08, 162.98 (13C@N). Anal. Calc.
for C50H44ClCuN2O4P2: C, 66.89; H, 4.94; N, 3.12. Found:
C, 66.87; H 4.95; N, 3.11%.
1H NMR (500 MHz, CDCl3): H NMR (CDCl3; d): 1.68
(s, 3H, CH3), 1.92 (s, 3H, CH3), 6.90–7.40 (m, 34H, ArH,
amine ring, PPh3), 7.53 (t, 1H, H2), 8.24 (m, 2H, H3, H4),
8.43 (d, 1H, JH2,1 = 7.25, H1), 8.63 (s, 1H, H5). 13C {1H}
NMR (500 MHz, CDCl3): 17.30 (5-13CH3), 20.54
(2-13CH3), 123.00, 125.55, 127.84, 128.42 (d, J = 4.1, ipso-
C of PPh3), 128.99, 130.40, 131.42, 133.12, 136.58,
139.87, 148.15, 149.64, 150.14, 162.70 (13C@N). Anal. Calc.
for C50H44ClCuN2O4P2: C, 66.89; H, 4.94; N, 3.12. Found:
C, 66.90; H, 4.93; N, 3.11%.
2.2.11. [CuI(C)(PPh3)2]ClO4 (2c)
This complex was prepared by a procedure similar to 1
using 21 mg (0.1 mmol) of (2,4-dimethyl-phenyl)-pyridin-2-
ylmethylene-amine, C. Yellow-orange crystals were col-
lected by filtration and dried in vacuo. Yield: 80 mg
(90%). IR (KBr): 1595 cmꢀ1 m(C@N), 1091 cmꢀ1 m(Cl–O),
1H NMR (500 MHz, CDCl3): 1.45 (s, 3H, CH3), 2.10 (s,
3H, CH3), 6.70–7.59 (m, 34H, ArH, amine ring, PPh3),
7.50 (t, 1H, H2), 8.20 (m, 2H, H3, H4), 8.41 (d, 1H,
JH2,1 = 7.8, H1), 8.63 (s, 1H, H5). 13C {1H} NMR
(500 MHz, CDCl3): 18.35 (4-13CH3), 20.30 (2-13CH3),
123.60, 124.30, 126.63, 128.28 (d, J = 4.0, ipso-C of
PPh3), 129.12, 130.56, 132.32, 133.23, 137.60, 139.12,
147.91, 149.56, 150.24, 162.55 (13C@N). Anal. Calc. for
C50H44ClCuN2O4P2: C, 66.89; H, 4.94; N, 3.12. Found:
C, 66.88; H, 4.95; N, 3.12%.
2.3. X-ray analysis
Crystals of 1b, 1c and 2a suitable for X-ray analysis were
obtained as described above. The single crystals were
mounted on a Nonius Kappa-CCD area detector diffrac-
˚
tometer (Mo Ka k = 0.71073 A). The complete conditions
of data collection (Denzo software) and structure refine-
ments are given below. The cell parameters were deter-
mined from reflections taken from one set of 10 frames
(1.0° steps in phi angle), each at 20 s exposure. The struc-
tures were solved using direct methods (SHELXS97) and
refined against F2 using the SHELXL97 software [32]. The
absorption was not corrected. All non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were gener-
ated according to stereochemistry and refined using a rid-
ing model in SHELXL97. The crystal data and refinement
details are summarized in Table 1.
2.2.12. [CuI(D)(PPh3)2]ClO4 (2d)
This complex was prepared by a procedure similar to 1
using 21 mg (0.1 mmol) of (2,5-dimethyl-phenyl)-pyridin-2-
ylmethylene-amine, D. Yellow-orange crystals were col-
lected by filtration and dried in vacuo. Yield: 75 mg
(84%). IR (KBr): 1590 cmꢀ1 m(C@N), 1091 cmꢀ1 m(Cl–O),
Table 1
Crystal data and single crystal X-ray diffraction refinement details for compounds 1b, 1c and 2a
Formula
C
28H28ClCuN4O4
C28H28ClCuN4O4
C100H87Cl2Cu2N5O8P4
Formula weight
Crystal system
Space group
583.53
monoclinic
P2/n
12.350(4)
8.238(3)
13.201(4)
90.00
91.348(2)
90.00
1342.7(8)
2
583.53
monoclinic
C2/c
34.062(5)
8.938(2)
22.760(5)
90.00
128.33(5)
90.00
5435.6(42)
8
1808.61
triclinic
ꢀ
P1
˚
a (A)
11.0500(10)
12.676(2)
32.847(5)
79.13(5)
81.31(4)
85.21(7)
4459.3(14)
2
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
V (A3)
Z
Density (g cmꢀ3
)
1.443
0.954
604
1.426
0.943
2416
1.347
0.669
1876
l(Mo Ka) (mmꢀ1
F(000)
)
Data collection
Temperature (K)
173(2)
173(2)
173(2)
h minimum–maximum
Dataset [h,k,l]
Total, unique data, Rint
Observed data
2.91–30.02
1.52–27.45
1.27–27.49
ꢀ17/11, ꢀ11/11, ꢀ18/18
3920, 2479, 0.0503
>2r(I)
ꢀ43/44, ꢀ11/10, ꢀ25/29
6206, 3739, 0.0955
>2r(I)
ꢀ9/14, ꢀ16/16, ꢀ42/42
19850, 10524, 0.0956
>2r(I)
Refinement
No. of reflections, no. of parameters
R1, R2
wR1, wR2
Goodness-of-fit
3920, 173
6207, 370
19850, 1075
0.0860, 0.1931
0.1809, 0.2144
1.070
0.0437, 0.0892
0.0994, 0.1126
1.078
0.0685, 0.1877
0.1526, 0.1963
1.040
Maximum and average shift/error
Minimum, maximum resolved density (e/A3)
0.001, 0.000
ꢀ0.484, 0.390
0.003, 0.000
ꢀ0.708, 0.696
0.002, 0.000
ꢀ1.403, 1.518

158
S. Dehghanpour et al. / Polyhedron 26 (2007) 154–162
3. Results and discussion
3.1. General characterization
determined by X-ray crystal structure analysis. The 1H res-
onances of the coordinated ligands are commonly observed
in complexes 1a–2d. In complexes 2a–2d, however, the aro-
matic H atoms of the coordinated Ph3P ligands overlap to
some extent with those of the phenyl H atoms of ligands
A–D. Aside from the aromatic H-atoms, which appear at
7.00–8.15 ppm in the complexes, the imine protons appear
as a singlet at 8.60–9.50 ppm in the complexes. The down-
field shift of the iminic protons relative to the free ligands
can be attributed to the deshielding effect resulting from
the coordination of the ligands [29]. The singlet at about
2 ppm in the compounds is assigned to the CH3 substitu-
tions of the phenyl ring.
The IR spectra of the free ligands exhibit the character-
istic band of the imine group, which appears in the region
1623–1630 cmꢀ1. This band is shifted to lower frequencies
in the IR spectra of the corresponding complexes due to
the coordination of the imine nitrogen [33], and appears
in the region 1580–1595 cmꢀ1. A strong band at about
1085 cmꢀ1 in the IR spectra of the complexes is character-
istic of the asymmetric Cl–O stretching mode of the per-
chlorate anion [34].
The electronic absorption spectra of the ligands and the
corresponding complexes are presented in Table 2. Since no
d–d transitions are expected for a d10 complex, the UV–Vis
bands are assigned to metal to ligand charge transfer
(MLCT) or ligand-centered p ! p* transitions [35].
The absorption spectrum of [Cu(A)2]ClO4 (1a), in chlo-
roform features a band with a true maximum at 518 nm,
whereas [Cu(A)(PPh3)2]ClO4 (2a), shows a clear shoulder
at 419 nm, which is shifted considerably (ca. 99 nm) rela-
tive to that of complex 1a. A similar shift (90 nm) has been
reported in going from [Cu(dmp)2]+ (kMLCT = 454 nm) to
[Cu(dmp)(PPh3)2]+ (kMLCT = 365 nm) [3þ6] and also similar
shifts were observed in the other CuðLÞ2 complexes 1b–1d
The sharp NMR peaks are indicative of diamagnetic
Cu(I) complexes. The appearance of a unique signal for
each type of proton in CDCl3 solution indicates that the
symmetry of the molecules is retained in solution, and only
one isomer or exchange processes within the NMR time-
scale are present.
3.2. X-ray structures of [Cu(B)2]ClO4 (1b),
[Cu(C)2]ClO4 (1c) and [Cu(A)(PPh3)2]ClO4 Æ
1/2CH3CN (2a)
The crystallographic data are summarized in Table 1
and selected bond distances and angles are given in Table
3. No classical H-bonding occurs in these three crystal
structures.
þ
relative to the CuðLÞðPPh3Þ2 complexes 2b–2d (Table 2).
The considerable red shift in the position of the first
MLCT band of complexes 1a–1d as compared to that of
other bis(diimine) copper(I) complexes is quite interesting
and points to the possible application of these complexes
as more efficient charge transfer photosensitizers in the vis-
ible region. Additional absorption bands are also observed
in the spectra of 1a–2d in chloroform in the UV region
(Table 2). The intensity of these bands are consistent with
being assigned as ligand-centered p ! p* or/and charge-
transfer transitions.
A view of the cation of complex 1b, including the atom-
numbering scheme is illustrated in Fig. 2. While a tetrahe-
dral geometry might be expected for a four coordinated
copper(I) center, the coordination sphere around the metal
ion in this complex is distorted by the restricting bite angles
of the chelating ligand. The intraligand N1–Cu–N2 angle is
much less than 109.5°, being only 81.07(7)°. On the
contrary the N2–Cu–N2b and N1–Cu–N2b angles
(134.31(10)°, 122.41(7)°) are much larger than those of a
tetrahedral complex. The average Cu–N bond distance
1
The H NMR spectra and peak assignments are pre-
+
˚
sented in the experimental section in each complex. These
peaks are assigned based on the splitting of the resonance
signals, spin coupling constants and the literature, and
are clearly in accordance with the molecular structure
(2.037 A) is similar to that found in the [Cu(dpdmp)2] cat-
˚
ion (2.047 A) at room temperature [37], and other Cu(I)
pseudotetrahedral complexes (typical Cu–Nav = 2.055 A)
˚
[38].
Table 2
IR, UV–Vis spectral data and cyclic voltammetric data of ligands and complexes
m(C@N)/cmꢀ1
m(Cl–O)/cmꢀ1
k
max/nm (Loge/Mꢀ1 cmꢀ1
)
Ep
Ep
a
c
Compound
A
B
C
1623
1630
1629
1629
1582
1578
1585
1580
1580
1591
1595
1590
241 (4.05), 283 (3.97), 329 (3.92)
245 (4.29), 281 (4.20), 332 (3.90)
239 (4.68), 275 (4.58), 341 (4.44)
241 (4.86), 273 (4.75), 339 (4.45)
249 (4.52), 339 (4.55), 518 (3.74)
255 (4.49), 328 (4.17), 500 (3.59)
248 (4.54), 341 (4.23), 500 (3.61)
254 (4.37), 315 (4.08), 485 (3.51)
243 (4.09), 342 (4.37), 419 (4.01)
243 (4.53), 273 (4.41), 414 (3.54)
241 (4.60), 275 (4.31), 418 (3.65)
243 (4.66), 268 (3.57), 414 (3.72)
D
1a
1b
1c
1d
2a
2b
2c
2d
1090
1095
1090
1091
1092
1088
1091
1091
0.41
0.46
0.46
0.48
0.29
0.41
0.39
0.37
0.84
0.67
0.66
0.67
1.73
1.71
1.69
1.68

S. Dehghanpour et al. / Polyhedron 26 (2007) 154–162
159
Table 3
Selected bond lengths (A) and bond angles ° for 1b, 1c and 2a
˚
1b
1c
2a
I
II
Cu–N1
Cu–N2
Cu–N1b
N1–C1
N1–C7
C1–C2
2.0180(16)
2.0564(16)
2.0179(16)
1.279(2)
1.439(3)
1.460(3)
Cu1–N1
Cu1–N2
Cu1–N3
Cu1–N4
N2–C1
N2–C7
N4–C15
N4–C21
2.021(4)
2.067(4)
2.039(4)
2.018(4)
1.283(6)
1.427(6)
1.284(6)
1.427(6)
1.453(7)
1.386(7)
82.06(17)
125.27(16)
126.21(18)
105.68(17)
140.10(16)
81.65(17)
111.3(4)
130.2(4)
110.3(3)
126.1(3)
119.3(4)
118.3(5)
Cu1–N1
Cu1–N2
Cu1–P1
Cu1–P2
N1–C5
N1–C8
N2–C9
N2–C13
2.064(4)
2.103(5)
2.2447(18)
2.2489(19)
1.438(6)
1.285(7)
1.343(7)
1.349(7)
1.456(8)
Cu2–N3
Cu2–N4
Cu2–P3
Cu2–P4
N3–C54
N3–C57
N4–C58
N4–C62
2.085(6)
2.142(5)
2.2359(19)
2.275(2)
1.407(8)
1.320(8)
1.346(9)
1.330(9)
1.417(10)
1.830(7)
79.6(2)
120.04(15)
104.66(14)
115.11(15)
98.79(14)
126.99(8)
128.7(4)
112.2(5)
110.1(5)
131.1(6)
119.1(6)
118.0(7)
C1–C2
C2–C3
C8–C9
P1–C14
C57–C58
P3–C75
1.825(6)
N1–Cu–N2
N1–Cu–N1b
N1–Cu–N2b
N2–Cu–N2b
Cu–N1–C1
Cu–N1–C7
Cu–N2–C2
Cu–N2–C6
C1–N1–C7
C2–N2–C6
81.07(7)
121.27(10)
122.41(7)
134.31(10)
113.79(14)
126.23(11)
111.30(13)
131.61(13)
119.97(16)
117.08(16)
N1–Cu1–N2
N1–Cu1–N3
N1–Cu1–N4
N2–Cu1–N3
N2–Cu1–N4
N3–Cu1–N4
Cu1–N1–C2
Cu1–N1–C6
Cu1–N2–C1
Cu1–N2–C7
C1–N2–C7
C2–N1–C6
N1–Cu–N2
N1–Cu–P1
N1–Cu–P2
N2–Cu–P1
N2–Cu–P2
P1–Cu–P2
Cu1–N1–C5
Cu1–N1–C8
Cu1–N2–C9
Cu1–N2–C13
C5–N1–C8
C9–N2–C13
79.39(18)
118.13(14)
114.76(13)
105.35(14)
111.81(13)
119.22(7)
126.1(3)
113.9(4)
112.0(4)
129.7(4)
119.4(5)
N3–Cu–N4
N3–Cu–P3
N3–Cu–P4
N4–Cu–P3
N4–Cu–P4
P3–Cu–P4
Cu2–N3–C54
Cu2–N3–C57
Cu2–N4–C58
Cu2–N4–C62
C54–N3–C57
C58–N4–C62
118.2(5)
Fig. 2. ORTEP view of the crystal structure of [Cu(B)2]ClO4 (1b) showing the atom labelling scheme. The thermal ellipsoids enclose 50% of the electronic
density. Hydrogen atoms are omitted for clarity.
The dihedral angle between the two chelate rings is
85(1)°. The value for the dihedral angle of N1–C1–C2–
N2 is 0.00(3)°, and comparison of the dihedral angles
between the chelate rings and pyridine groups indicate
the coplanarity of these moieties, resulting in a bite size
environment of the imine and pyridine nitrogen atoms is
planar. The planarity is measured by three N atom bond
P
angles ( N). For 1b, the sum of these angles is 359.99°
for N1 and N2. Despite the fact that the nitrogen atoms
in 1b are sp2 hybridized, some strain in the chelate ring is
suggested by the deviation from the 120° angle about the
˚
of 3.233 A of d(N(1)–N(2)) for the chelating ligand. The

160
S. Dehghanpour et al. / Polyhedron 26 (2007) 154–162
nitrogen,
Cu–N1–C1
(113.79(14)°),
Cu–N1–C7
that the chelate ring are planar, the sum of three N atom
(126.23(11)°), C1–N1–C7 (119.97(16)°), Cu–N2–C2
(111.30(13)°), Cu–N2–C6 (131.61(13)°) and C2–N2–C6
(117.08(16)°). The dihedral angle of the chelate ring and
phenyl ring (C7 ! C12) is 69.4(3)°.
bond angles is 359.4° for N1, 359.9 for N2, 360 for N3,
and 359.3 N4, however, some strain in the chelate ring is
suggested by the deviation from the 120° angle about the
nitrogen, for example; Cu1–N1–C6 (130.2(4)°), Cu1–N2–
C7 (126.3(4)°) and Cu1–N3–C20 (130.2(4)°). The planarity
The cation of complex 1c, along with the atom-number-
ing scheme, is shown in Fig. 3. As in complex 1b, the geom-
etry about Cu(I) in 1c is also distorted by the restricting bite
angles of the chelating ligand. The N1–Cu1–N2 and N3–
Cu1–N4 angles are 82.1(2)° and 81.7(2)°, respectively. How-
ever, the N2–Cu1–N4, N1–Cu1–N4 and N1–Cu1–N3
angles are 140.0(2)°, 126.3(2)° and 125.3(2)° respectively.
˚
of the chelate rings results in a bite size of 3.233 A for
d(N(1)–N(2)) and 3.248 for d(N(3)–N(4)) for the two che-
lating ligands.
The cation of complex 2a, along with the atom-number-
ing scheme, is shown in Fig. 4, and selected bond distances
and angles are listed in Table 3. The compound 2a crystal-
lizes with two molecules per asymmetric unit, probably due
to some small conformational differences. As in complex 1b
and 1c, the coordination environment around the metal ion
in this complex is pseudotetrahedral with large angular dis-
tortion arising from the low intraligand N1–Cu–N2 chelate
angle, 79.39(18)° in I and N3–Cu–N4 chelate angle,
79.6(2)° in II. However, the P1–Cu–P2, 119.22(7)° angle
in I and the P3–Cu–P4, 126.99(8)° angle in II have opened
˚
The average Cu–N bond distance (2.0375 A) is similar
to that found in other Cu(I)(diimine) pseudotetrahedral
complexes [37–39].
The dihedral angle between the two chelate rings is
83(1)°. Torsion angles in the chelating rings and the pyri-
dine groups are listed in Table 4. This result demonstrates
that the chelating rings are nearly planar and the pyridine
groups are coplanar with the chelate rings. Despite the fact
Fig. 3. ORTEP view of the crystal structure of [Cu(C)2]ClO4 (1c) showing the atom labelling scheme. The thermal ellipsoids enclose 50% of the electronic
density. Hydrogen atoms are omitted for clarity.
Table 4
Torsion angles for chelating rings
1b
1c
2a
I
II
N1–C1–C2–N2
N1–C1–C2–C3
Cu–N1–C1–C2
C1–C2–C3–C4
Cu–N2–C2–C1
N1–Cu–N2–C2
0.0(3)
178.3(2)
3.6(3)
N2–C1–C2–N1
N2–C1–C2–C3
Cu1–N1–C2–C1
C1–C2–C3–C4
Cu1–N2–C1–C2
N2–Cu1–N1–C2
ꢀ12.8(7)
169.1(5)
4.3(5)
N1–C8–C9–C10
N1–C8–C9–C10
Cu1–N1–C8–C9
C1–C2–C3–C4
Cu1–N2–C9–C8
N1–Cu1–N2–C9
174.4(5)
174.4(5)
4.1(6)
179.8(6)
2.7(6)
N3–C57–C58–N4
N3–C57–C58–C59
Cu2–N3–C57–C58
C57–C58–C59–C60
Cu2–N4–C58–C59
Cu2–N3–C57–C58
4.2(9)
ꢀ171.4(6)
0.1(7)
175.9(7)
169.7(6)
0.1(7)
ꢀ177.0(2)
ꢀ179.2(5)
ꢀ3.4(2)
13.7(6)
4.01(14)
2.03(3)
ꢀ0.5(4)

S. Dehghanpour et al. / Polyhedron 26 (2007) 154–162
161
Fig. 4. ORTEP view of the crystal structure of [Cu(A)(PPh3)2]ClO4 (2a) showing the atom labelling scheme. The thermal ellipsoids enclose 50% of the
electronic density. Solvent molecules and hydrogen atoms are omitted for clarity.
up due to the steric effects from the bulky Ph3P ligands.
The average Cu–N and Cu–P bond distances are 2.098
and 2.251 A, respectively, and are comparable to those
resistance to tetrahedral distortion occurring in the corre-
sponding CuIIN4 chromophore [20,41]. Although, a higher
degree of conjugation exists in 1a–1d relative to 2a–2d, the
existence of bulkier ligands in 2a–2d which prevent the
inner-sphere reorganization to a flattened tetrahedral, more
appropriate to Cu(II) oxidation state, play a key role in
shifting the oxidation potential to higher values for com-
plexes 2a–2d relative to 1a–1d. However, the potential is
approximately insensitive to the methyl substituents on
the phenyl ring of ligands in the complexes 1a–1d and/or
2a–2d.
˚
reported for [Cu(dmp)(PPh3)2]NO3 (2.117(6) and
˚
2.294(2) A) [29,40].
The chelate ring in complex 2a is also nearly planar
(Table 4) with some strain caused by the deviation from
120° angle about the N-atom (Cu1–N1–C5 126.1(3)°;
Cu1–N2–C13 129.7(4)° in I; Cu2–N3–C54 128.7(4)°;
Cu2–N4–C62 131.1(6)° in II). The dihedral angle between
the chelate ring (Cu–N–C–C–N) and the plane defined by
P1–Cu1–P2 is 75(1)° (and 73(1)° in the other molecule of
the asymmetric unit) and agrees well with the 82.2° value
for [Cu(dmp)(PPh3)2]NO3 [25,36].
Acknowledgement
S. D. would like to acknowledge the Alzahra University
Research Council for partial support of this work.
3.3. Electrochemistry
The electrochemical behavior of the complexes was
examined by means of cyclic voltammetry in CH2Cl2.
The four ligands are electroinactive in the working poten-
tial region. The complexes show a quasireversible CuII/I
couple (Table 2) and the ratio of the anodic and cathodic
peak currents (ipa/ipc), approaches 1 as the scan rate
increases. The peak-to-peak separations increase as the
scan rate is changed from 50 mV/s to 500 mV/s.
Appendix A. Supplementary material
Crystallographic data (excluding structure factors) for
the structures 1b, 1c and 2a reported in this paper have been
deposited with the Cambridge Crystallographic Data Cen-
ter, no. CCDC 612098–612100, respectively. Copies of the
data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223
336033; e-mail: deposit@ccdc.cam.ac.uk or http://www.
ccdc.cam.ac.uk/conts/retrieving.html). Supplementary data
The CuII/I potential in a CuIN4 chromophore is believed
to increase with increasing p-acidity of the ligands and the

162
S. Dehghanpour et al. / Polyhedron 26 (2007) 154–162
[21] V. Desvergnes-Breuil, V. Hebbe, C. Dietrich-Buchecker, J-P. Sau-
vage, J. Lacour, Inorg. Chem. 42 (2003) 255.
[22] G.C. Van Stein, G. van Koten, B. Debok, L.C. Taylor, K. Vrieze, C.
Brevard, Inorg. Chim. Acta 89 (1984) 29.
[23] X.H. Zhou, T. Wu, D. Li, Inorg. Chim. Acta 359 (2006) 1442.
[24] J.A. Garciavazquez, M. Lopezbecerra, J.R. Masaguer, Polyhedron 10
(1983) 1081.
[25] P.R. Shukla, R. Takroo, J. Indian Chem. Soc. 57 (1980) 556.
[26] R.E. Rulke, J.G.P. Delis, A.M. Groot, C.J. Elsevier, P.W.N.M. van
Leeuwen, K. Vrieze, K. Goubitz, H. Schenk, J. Organomet. Chem.
508 (1996) 109.
associated with this article can be found, in the online ver-
sion, at doi:10.1016/j.poly.2006.08.011.
References
[1] N. Armaroli, Chem. Soc. Rev. 30 (2001) 113.
[2] D.R. McMillan, J.R. Kirchhoff, K.V. Goodwin, Coord. Chem. Rev.
64 (1985) 83.
[3] Y. Lei, Z. Tyeklar (Eds.), Bioinorganic Chemistry of Copper,
Chapman & Hall, New York, 1993.
[4] B.G. Malmstrom, in: R.J.P. Williams, J.R.R.F. De Silva (Eds.), New
Trends in Bioinorganic Chemistry, Academic Press, New York, 1978,
p. 59.
[5] S. Sakaki, T. Kuroki, T. Hamada, J. Chem Soc., Dalton Trans. (2002)
840.
[6] G.A. Hogan, A.A. Gallo, K.M. Nicholas, R.S. Srivastava, Tetrahe-
dron Lett. 43 (2002) 9505.
[7] S. Mahadevan, M. Palaniandavar, Inorg. Chem. 37 (1998) 693.
[8] F. Liu, K.A. Meadows, D.R. McMillin, J. Am. Chem. Soc. 115 (1993)
6699.
[27] S. Meghdadi, M. Amirnasr, K.J. Schenk, S. Dehghanpour, Helv.
Chim. Acta 85 (2002) 2807.
[28] R. Hadjikhani, S. Dehghanpour, A. Mahmoudi, F. Mojahed, Z.
Anorg. Allg. Chem. 632 (2006) 723.
[29] M. Amirnasr, G. Kickelbick, S. Dehghanpour, Helv. Chim. Acta 89
(2006) 274.
[30] D.D. Perrin, W.L. Armarego, D.R. Perrin, Purification of Laboratory
Chemicals, 2nd ed., Pergamon, New York, 1990.
[31] P. Hemmerich, C. Sigwart, Experientia 15.IX (1963) 488.
[32] G.M. Sheldrick, in: SHELXL-93, Program for Crystal Structure
Refinement, University of Go¨ttingen, Go¨ttingen, 1993.
[33] C.T. Cunnighum, J.J. Moore, K.L.H. Cunningham, P.E. Fanwick,
D.R. McMillin, Inorg. Chem. 39 (2000) 3638.
[9] M. Ruthkosky, C.A. Kelly, F.N. Castellano, G.J. Meyer, Coord.
Chem. Rev. 171 (1998) 309.
[10] M. Ruthkosky, F.N. Castellano, G.J. Meyer, Inorg. Chem. 35 (1996)
6406.
[34] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
[11] A.K.I. Gushurst, D.R. McMillin, C.O. Dietrich-Buchecker, J.P.
Sauvage, Inorg. Chem. 28 (1989) 4070.
Coordination Complexes, 4th ed., John Wiley
1992.
& Sons, USA,
[12] A.K. Ichinaga, J.R. Kirchhof, D.R. McMillin, C.O. Dietrich-
Buchecker, P.A. Marnot, J.P. Sauvage, Inorg. Chem. 26 (1987) 4290.
[13] M. Ruthkosky, C.A. Kelly, M.C. Zaros, G.J. Meyer, J. Am. Chem.
Soc. 119 (1997) 12004.
[35] A.A. Del Paggio, D.R. McMillin, Inorg. Chem. 22 (1983) 691.
[36] R.A. Rader, D.R. McMillin, M.T. Buckner, T.G. Matthews, D.J.
Casadonte, R.K. Lengel, S.B. Whittaker, L.M. Darmon, F.E. Lytle,
J. Am. Chem. Soc. 103 (1981) 5906.
[14] D.R. McMillin, M.T. Buckner, B.T. Ahn, Inorg. Chem. 16 (1977) 943.
[15] C.O. Dietrich-Buchecker, J.-P. Sauvage, Chem. Rev. 87 (1987) 795.
[16] C.C. Phifer, D.R. McMillin, Inorg. Chem. 25 (1986) 1329.
[17] A.K. Ichinaga, J.R. Kirchhoff, D.R. McMillin, C.O. Dietrich-
Buchecker, P.A. Marnot, J.-P. Sauvage, Inorg. Chem. 26 (1987) 4290.
[18] R.M. Everly, D.R. McMillin, J. Phys. Chem. 95 (1991) 9071.
[19] C.T. Cunningham, K.L.H. Cunningham, J.F. Michalec, D.R.
McMillin, Inorg. Chem. 38 (1999) 4388.
[37] M.T. Miller, P.K. Gantzel, T.B. Karpishin, Inorg. Chem. 37 (1998)
2285.
[38] D.A. Bradwell, J.C. Jeffery, C.A. Otter, M.D. Ward, Polyhedron 15
(1996) 191.
[39] P.K. Santra, D. Das, T.K. Misra, R. Roy, C. Sinha, S.-M. Peng,
Polyhedron 18 (1999) 1909.
[40] J.R. Kirchhoff, D.R. McMillin, W.R. Robinson, D.R. Powell, A.T.
McKenzie, S. Chen, Inorg. Chem. 24 (1985) 3928.
[41] M.T. Miller, P.K. Gantzel, T.B. Karpishin, Angew. Chem., Int. Ed.
37 (1998) 1556.
[20] M.T. Miller, P.K. Gantzel, T.B. Karpishin, Inorg. Chem. 38 (1999)
3414.