Synthesis, crystal structure, magnetic and redox properties of copper(II) complexes of N-alkyl(aryl) tBu-salicylaldimines

Article abstract of DOI:10.1016/j.ica.2010.11.017

A series of novel copper(II) complexes, L₂Cu with newly synthesized 3,5-Bu2t-salicylaldimine (or 5-Bu2t-salicylaldimine) ligands derived from 2,4-di-tert-butyl phenol (or 4-tert-butyl phenol) and alkyl (aryl) amines have been prepared and their

Full text of DOI:10.1016/j.ica.2010.11.017

Inorganica Chimica Acta 366 (2011) 275–282
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis, crystal structure, magnetic and redox properties of copper(II)
complexes of N-alkyl(aryl) tBu-salicylaldimines
a
b
ˇ ´ c
Elham Safaei a, , Masoume Mohseni Kabir , Andrzej Wojtczak , Zvonko Jaglicic ,
⇑
Anna Kozakiewicz b, Yong-Ill Lee d
a Institute for Advanced Studies in Basic Sciences (IASBS), 45195 Zanjan, Iran
b Nicolaus Copernicus University, Department of Chemistry, 87-100 Torun, Poland
c Institute of Mathematics, Physics and Mechanics and Faculty of Civil and Geodetic Engineering, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana, Slovenia
d Department of Chemistry, Changwon National University, Changwon 641-773, South Korea
a r t i c l e i n f o
a b s t r a c t
A series of novel copper(II) complexes, L2Cu with newly synthesized 3,5-But -salicylaldimine (or 5-But -
Article history:
2
2
Received 9 September 2010
Received in revised form 6 November 2010
Accepted 10 November 2010
Available online 20 November 2010
salicylaldimine) ligands derived from 2,4-di-tert-butyl phenol (or 4-tert-butyl phenol) and alkyl (aryl)
amines have been prepared and their spectroscopic (IR, UV–Vis, ESI-MS), X-ray, magnetic and redox prop-
erties have been investigated. The X-ray crystallography analysis shows that all complexes are mono-
meric and their copper(II) centers are surrounded by phenolate oxygens and imine nitrogen atoms.
Therefore, the coordination sphere around the copper atoms is N2O2 as seen in galactose oxidase active
site. In addition, the geometric configurations of all complexes are square planar or slightly distorted
square planar. The crystal system for all complexes is monoclinic, except for L12Cu which is orthorhombic.
The temperature dependence of magnetic susceptibility of complexes confirms the mononuclear struc-
ture of complexes. Oxidation of the Cu(II) complexes yielded the corresponding Cu(II)-phenoxyl radical
species during the cyclic voltammetry experiments.
Keywords:
Copper complexes
Phenoxyl
Enzyme models
5-But2-salicylaldimine
3,5-But2-salicylaldimine
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
research groups have synthesized the biomimetic model com-
plexes with O,N,O coordination sphere (usually amine nitrogen
Metalloenzymes control a wide range of functions in the biolog-
ical systems. Galactose oxidases (GOA), cytochrome c oxidase
(Cco), iron-containing ribonucleotide reductase (RR) are typical
examples of these enzymes [1–4]. Galactose oxidase (GOA) is an
enzyme containing single Cu ion (Scheme 1) which belongs to
the family of oxidoreductases. It contains a cysteine-modified phe-
nol moiety of Tyr 272 (Y272) and a phenol group of tyrosine 495
(Y495) coordinated to a copper(II) center. This enzyme catalyzes
and phenolic oxygen atoms) [23–27].
We focused our interest on copper complexes of iminopheno-
late ligands involving easily oxidizable bulky 3,5-But2-phenols pro-
ducing more stable phenoxyl radical complexes due to their
structural similarities to galactose oxidase active site. In the
present work, we have synthesized several N-alkyl (aryl) salicyl-
aldimine ligands, H2L, with O and N donor atoms bearing alkyl or
aryl groups and their copper(II) complexes (Scheme 3). The coordi-
nation, magnetic and redox properties of these complexes are
described.
the oxidation of D-galactose and wide range of primary alcohols
with concomitant reduction of dioxygen to hydrogen peroxide
[5–22].
The proposed mechanism (Scheme 2) of oxidation by GOase in-
volves a cycle of the three distinct oxidation states: the fully
oxidized form (Cu2+-Tyrꢀ), fully reduced form (Cu+-Tyr) and semi
form (Cu2+-Tyr) which is catalytically inactive [22].
2. Experimental
2.1. Materials and physical measurements
Extensive efforts have been made to provide a valuable insight
into the structure and reactivity of GOA active site. Salen and tripo-
dal ligands have been widely employed to provide a coordination
sphere as models for the active site of this enzyme. Several
Reagents or analytical grade materials were obtained from com-
mercial suppliers and used without further purification, except
those for electrochemical measurements. 3,5-But2-salicylaldehyde
(3,5-DTBS) and 5-But2-salicylaldehyde (5-TBS) were prepared by
the literature method [28,29].
⇑
Elemental analyses (C. H. N.) were performed by the Research
Institute of Petroleum Industry (RIPI). Fourier transform infrared
Corresponding author. Tel.: +98 241 4153200; fax: +98 241 4153232.
E-mail address: safaei@iasbs.ac.ir (E. Safaei).
0020-1693/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2010.11.017

276
E. Safaei et al. / Inorganica Chimica Acta 366 (2011) 275–282
O
N
O
N
Y
X
Cu
Cu
Y
X
N
O
N
O
(a)
(b)
Scheme 1. Structure of the GOA catalytic center [22].
(X)
Ligand
HL1
-CH3
HL2
-(CH2)3CH3
-CH2C6H5
-C6H5
HL3
HL4
HL5
-C6H5OCH3
-C10H7
HL6
(Y)
Ligand
HL'1
HL'2
-CH3
-(CH2)3CH3
Scheme 3. The structure of bis(N-Y-5-But2-salicylaldiminate) copper complex (a)
and bis(N-X- 3,5-But2-salicylaldiminate) copper complex (b).
SQUID susceptometer (Quantum Design MPMS-XL-5) in a mag-
netic field of 1000 Oe.
Voltammetric measurements were made with a computer con-
trolled Auto Lab electrochemical system (ECO Chemie, Ultrecht,
The Netherlands) equipped with a PGSTA 30 model and driven
by GPES (ECO Chemie). A glassy carbon electrode with a surface
area of 0.035 cm2 was used as a working electrode and a platinum
wire served as the counter electrode. The reference electrode was
an Ag wire as the quasi reference electrode. Ferrocene was added
as an internal standard after completion of a set of experiments,
and potentials are referenced vs. the ferrocenium/ferrocene couple
(Fc+/Fc).
Scheme 2. Redox states of GAO [22].
spectroscopy on KBr pellets was performed on a FT IR Bruker
Vector 22 instrument. NMR measurements were performed on a
Bruker 250 instrument. UV–Vis absorbance digitized spectra were
collected using a CARY 100 spectrophotometer. The electronic
spectra of all complexes recorded in CH3CN.
The X-ray data for the reported complexes were collected with
an Oxford Sapphire CCD diffractometer using Mo K
a radiation
The ligand samples were dissolved in acetonitrile (1.0 ꢀ
10ꢁ4 M) and mixed with deionized water (1:1) just before the mass
spectroscopic measurements. The identification of interaction
products was performed using Thermo Finigan LCQ Advantage
ion trap mass spectrometer equipped with electrospray ionization.
For sample injections, the instrument syringe pump was used at
flow rate of 2 L/min. The instrumental operation conditions were
as follows; spray voltage, 4.58 kV; source current, 0.48 A; sheath
gas flow rate, 19.43 L/min; capillary voltage; 9.44 V, capillary tem-
perature 100 °C, tube lens voltage; 55 V. Experiments were per-
formed in positive-ion mode and optimized by Xcalibur software
before the experiments. All MS experiments in this work have been
carried out under the optimized instrument conditions. All re-
ported mass spectra are the average of at least 30 consecutive
scans.
k = 0.71073 Å, at 293(2) or 292(2) K, by -2h method. Structures
x
have been solved by direct methods and refined with the full-
matrix least-squares method on F2 with the use of SHELX97 [30] pro-
gram package. The numerical absorption correction was applied
(RED171 package of programs [31] Oxford Diffraction, 2000). No
extinction correction was applied. Positions of hydrogen atom have
been found from the electron density maps, and hydrogen atoms
were constrained in the refinement.
2.2. Preparations
2.2.1. Synthesis of ligands
All salicylaldimines HL, N-(1-methyl)-5-But2-salicylaldimine,
N-(1-butyl)-5-But2-salicylaldimine, N-(1-benzyl)-5-But2-salicylaldi-
mine, N-(1-phenyl)-5-But2-salicylaldimine, N-(1-methoxy-phe-
nyl)-5-But2-salicylaldimine, N-(1-naphthyl)-5-Bu2t -salicylaldimine,
Magnetic susceptibility were measured from powder samples
of solid material in the temperature range 2–300 K by using a

E. Safaei et al. / Inorganica Chimica Acta 366 (2011) 275–282
277
and HL0, N-(1-methyl)-3,5-But2-salicylaldimine, N-(1-butyl)-3,5-
But2-salicylaldimine were prepared with good yields via condensa-
tion of the 3,5-But2-salicylaldehyde (3,5-DTBS) or 5-But2-salicylal-
dehyde (5-TBS) with the corresponding amines (1:1 M ratio) in
methanol at 50 °C for 5 h.
2.2.2.1.1. Complex L12Cu. (15.57% yield). Anal. Calc. for C24H32Cu-
N2O2 (443.19 g/mol): C, 64.9; H, 7.2; N, 6.3. Found: C, 66.2; H,
8.4; N, 7%. IR(KBr, cmꢁ1): 3450w, 2956s, 1628s, 1535 m, 1484sh,
1417 m, 1374 m, 1326 m, 1258 m, 1182w, 1098w, 1021w, 873s,
828sh, 715w, 604w, 529w, 457w. ESI MS: m/z = 443.
2.2.2.1.2. Complex L22Cu. (53.13% yield). Anal. Calc. for C30H44Cu-
N2O2 (527.28.19 g/mol): C, 68.2; H, 8.4; N, 5.3. Found: C, 69.1; H,
8.6; N, 5.5%. IR(KBr, cmꢁ1): 3452w, 2956s, 2863sh, 1625s,
1532sh, 1479s, 1388sh, 1328 m, 1257 m, 1214 m, 1177 m,
1140w, 1028w, 880s, 829sh, 720w, 605w, 514w, 454w. ESI MS:
m/z = 527.
2.2.1.1. Synthesis of ligands HL. A solution of 5-But2-salicylaldehyde
(1 mmol, 0.17 g) and amine (1 mmol) in 5 ml methanol was stirred
for 3 h at 50 °C. After cooling, obtained yellow product was filtered
and re-crystallized from dichloromethane/methanol (2:1). The
solution remaining after the removal of the solid was left to give
more products.
2.2.2.1.3. Complex L23Cu. (31.93% yield). Anal. Calc. for C36H40Cu-
N2O2 (595.25 g/mol): C, 72.6; H, 6.3; N, 4.7. Found: C, 71.2; H,
6.9; N, 4.4%. IR(KBr, cmꢁ1): 2955s, 2914sh, 2864sh, 1616s, 1531
m, 1464s, 1388 m, 1322s, 1257 m, 1173 m, 1141w, 1102w, 1015
m, 890s, 826sh, 747 m, 688 m, 614 m, 584sh, 487 m. ESI MS: m/
z = 595.
2.2.1.1.1. Ligand HL1. (20.15% yield). 1H NMR (CDCl3): d 13.232 (s,
1H), 8.345 (s, 1H), 7.325 (m, 3H), 3.746 (s, 3H), 1.292 (s, 9H).
IR(KBr, cmꢁ1): 3424w, 2958s, 1638s, 1491 m, 1399 m, 1266s,
1109w, 1019w, 827s.
2.2.1.1.2. Ligand HL2. (18.02% yield). M.P. 100.7, 1H NMR (CDCl3): d
13.998 (s, 1H), 8.356 (s, 1H), 7.221(m, 3H), 3.588 (s, 3H), 2.596 (s,
4H), 2.316 (s, 2H) 1.289 (s, 9H). IR(KBr, cmꢁ1): 3432s, 2957 m,
2362w, 1623s, 1587sh, 1489s, 1365w, 1264 m, 1178 m, 818 m,
694w. m.p. 100.7.
2.2.2.1.4. Complex L42Cu. (55.20% yield). Anal. Calc. for C34H38Cu-
N2O2 (567.22 g/mol): C, 71.6; H, 6.7; N, 4.9. Found: C, 72.8; H,
6.6; N, 5.1%. IR(KBr, cmꢁ1): 3447w, 3018s, 2953sh, 1615s,
1585sh, 1523 m, 1468s, 1413 m, 1374 m, 1324 m, 1258 m,
1170s, 1019w, 877 m, 832sh, 754 m, 701 m, 606w, 531 m, 446w.
ESI MS: m/z = 567.
2.2.1.1.3. Ligand HL3. (82.77% yield). M.P. 102.4, 1H NMR (CDCl3): d
13.195 (s, 1H), 8.466 (s, 1H), 7.344 (m, 8H), 4.827 (s, 2H), 1.323 (s,
9H). IR(KBr, cmꢁ1): 3428w, 3024s, 2957sh, 1631s, 1583sh, 1487s,
1445sh, 1372sh, 1261 m, 1181 m, 1124sh, 1054sh, 964w, 924sh,
886sh, 828sh, 728sh, 704sh, 657sh, 621sh, 453sh. m.p. 102.4.
2.2.1.1.4. Ligand HL4. (20.75% yield). M.P. 96.9, 1H NMR (CDCl3): d
13.040 (s, 1H), 8.649 (s, 1H), 7.282 (m, 8H), 1.361(s, 9H). IR(KBr,
cmꢁ1): 3429w, 2957 m, 2354 m, 1619s, 1575sh, 1490s, 1359w,
1258 m, 1178s, 1138sh, 1027w, 982w, 927w, 889w, 823s, 696 m,
650w, 621w. m.p. 96.9.
2.2.2.1.5. Complex L52Cu. (32.85% yield). Anal. Calc. for C36H42Cu-
N2O2 (627.24 g/mol): C, 68.8; H, 6.7; N, 4.4. Found: C, 67.6; H,
6.3; N, 4.5%. IR(KBr, cmꢁ1): 3430w, 3005s, 2954sh, 2359w, 1616s,
1511sh, 1463s, 1376 m, 1315 m, 1253s, 1168s, 1107sh, 1026 m,
1021w, 882s, 828sh, 688w, 600 m, 526w. ESI MS: m/z = 627.
2.2.2.1.6. Complex L62Cu. (24.59% yield). Anal. Calc. for C42H42Cu-
N2O2 (667.25 g/mol): C, 75.5; H, 5.3; N, 4.1. Found: C, 74.9; H,
6.2; N, 3.7%. IR(KBr, cmꢁ1): 3446w, 3052s, 2955sh, 1605s, 1525
m, 1467s, 1382 m, 1325 m, 1257 m, 1175 m, 1085w, 1028w, 831
m, 778 ms, 694w, 550w, 508w. ESI MS: m/z = 681.
2.2.1.1.5. Ligand HL5. (14.13% yield). M.P. 98.7, 1H NMR (CDCl3): d
13.209 (s, 1H), 8.633 (s, 1H), 7.252 (m, 7H), 3.848 (s, 3H), 1.328
(s, 9H). IR(KBr, cmꢁ1): 3430 m, 2956s, 2544w, 2049w, 1620s,
1498s, 1362w, 1293sh, 1252s, 1180 m, 1110w, 1031 m, 965w,
828s, 531 m. m.p. 98.7.
0
2.2.2.2. Synthesis of complexes L2 Cu. To the solution of synthesized
imines (HL0) (1 mmol), dry triethylamine (1 mmol, 0.138 ml) and
copper acetate monohydrate (1 mmol, 0.199 g) was added and
the mixture was stirred for 2 h in room temperature. Then the
brown solution was obtained, filtered and re-crystallized from
dichloromethane:methanol (2:1).
2.2.1.1.6. Ligand HL6. (38.11% yield). M.P. 115.1, 1H NMR (CDCl3): d
13.037 (s, 1H), 8.736 (s, 1H), 7.557 (m, 10H), 1.353 (s, 9H). IR(KBr,
cmꢁ1): 3420w, 3047w, 2955s, 2866sh, 1617s, 1566sh, 1488s,
1450sh, 1388s, 1257s, 1192sh, 1081w, 1031w, 971w, 937w, 882
m, 819sh, 775s, 650w, 623w, 579w. m.p. 115.1.
2.2.2.2.1. Complex L201Cu. (16.39% yield). Anal. Calc. for C32H48Cu-
N2O2 (555.31 g/mol): C, 71.3; H, 9.3; N, 4.4. Found: C, 68.6; H,
8.6; N, 5.5%. IR(KBr, cmꢁ1): 3421w, 2955s, 1627s, 1537 m, 1428s,
1353sh, 1316 m, 1262 m, 1166 m, 1098w, 1027 m, 914 m, 870
m, 829w, 795sh, 740 m, 635 m, 536sh, 461 m. ESI MS: m/z = 556.
2.2.2.2.2. Complex L202Cu. (31.14% yield). Anal. Calc. for C38H60Cu-
N2O2 (639.41 g/mol): C, 71.2; H, 9.4; N, 4.3. Found: C, 71.5; H,
9.3; N, 4.4%. IR(KBr, cmꢁ1): 3447w, 2957s, 1622s, 1536 m, 1444
m, 1398sh, 1317w, 1261 m, 1167w, 1116w, 1028w, 873w, 797w,
744w, 538w. ESI MS: m/z = 639.
2.2.1.2. Synthesis of ligands HL0. In a round bottom flask, a solution
of 3,5-But2-salicylaldehyde (1 mmol, 0.234 g) and amine (1 mmol)
in 5 ml methanol was stirred for 5 h at 50 °C. After cooling, ob-
tained yellow product was filtered and re-crystallized from dichlo-
romethane/ethanol (2:1).
1
2.2.1.2.1. Ligand HL0 . (38.25% yield). 1H NMR (CDCl3): d 13.020 (s,
1H), 8.349 (s, 1H), 7.263 (m, 2H), 3.760 (s, 3H), 1.564 (s, 9H), 1.658
(s, 9H). IR(KBr, cmꢁ1): 3439s, 2896sh, 2779w, 1639s, 1493s, 1400
m, 1365sh, 1263s, 1188w, 1134w, 1017 m, 965w, 927w, 878w,
828s, 716w, 655w, 616w, 484w.
2
2.2.1.2.2. Ligand HL0 . (59.86% yield). 1H NMR (CDCl3): d 14.002 (s,
3. Results and discussion
1H), 8.346 (s, 1H), 7.216 (m, 2H), 3.596 (s, 3H), 2.583 (s, 4H), 2.321
(s, 2H), 1.563 (s, 9H), 1.659 (s, 9H). IR(KBr, cmꢁ1): 3422w, 2959s,
1632s, 1470s, 1367 m, 1241 m, 1173sh, 1121w, 1025w, 941 m,
870w, 815w, 737w, 648w, 602w, 455 m.
All salicylaldimines ligands, HL, were synthesized from 3,5-But2-
salicylaldehyde (3,5-DTBS) or 5-But2-salicylaldehyde (5-TBS) with
the corresponding amines in a single-step condensation.
The ligands HL or HL0 in methanol were treated with copper
acetate, triethylamine in suitable ratio and the solution was re-
2.2.2. Synthesis of complexes
2.2.2.1. Synthesis of complexes L2Cu. To the solution of synthesized
imines (HL) (1 mmol), dry triethylamine (1 mmol, 0.138 ml) and
copper acetate monohydrate (1 mmol, 0.199 g) was added and
the mixture was stirred for 2 h in reflux conditions. Then the
brown solution was obtained, filtered and re-crystallized from
dichloromethane:methanol (2:1) and in one instance from dichlo-
romethane:ethanol (2:1).
fluxed to yield L2Cu and L0 Cu complexes, with relatively high
2
yields.
In IR spectra of all ligands (HL), mOH stretch is observed in the
range 2900–3000 cmꢁ1. The occurrence of this band at such a
relatively low wave number is characteristic of these ligands and
is an indication of extensive hydrogen bonding. The
m(C@N)
band in the spectra of the free ligands is observed in the region

278
E. Safaei et al. / Inorganica Chimica Acta 366 (2011) 275–282
1620–1640 cmꢁ1. In IR spectra of the complexes, the strong and
sharp band at frequencies around 3000 cmꢁ1 for the mOH stretch
of ligands disappeared, proving the coordination of phenol groups
The ESI-MS spectrum gave a relatively weak ML2H+ ion peaks, a
proton attached molecule, what clearly indicated the formation of
2:1 complexes, and intense peaks related to protonated ligands
(L + H)+. The original spectrum is shown in Supplementary mate-
rial. The molecular peaks of the complex ions are shown in Sections
2.2.2.1 and 2.2.2.2.
to the metal. The m(C@N) band in the complexes IR spectra shifted
to lower frequencies 1600–1630 cmꢁ1, what indicates coordination
of the azomethine nitrogen to the metal.
The electronic spectra of all complexes recorded in CH2Cl2 are
presented in Sections 2.2.2.1 and 2.2.2.2. The intra-ligand absorp-
3.1. X-ray Data collection and structure determination of L2Cu and
tions <400 nm are assigned to
p–
p
* and n–
p
* transitions. The high-
L02Cu
er energy transition is assigned to a phenolate-to-Cu(II) charge
transfer transition, on the basis of comparisons with the UV/Vis
spectra of other Cu(II)-phenolate complexes. The bands observed
around 650 nm are assigned to d–d transitions.
Crystal data for the investigated complexes are tabulated in
Table 1. The selected bond lengths and angles are presented in
Table 2.
Table 1
Crystal data for complex structures L12Cu, L32Cu, L25Cu, L62Cu and L201Cu.
L12Cu
L23C
L52Cu
L62Cu
L021Cu
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
C24H32CuN2O2
444.06
293(2)
0.71073
orthorhombic
Pbcm
C36H40CuN2O2
596.24
293(2)
0.71073
monoclinic
P2(1)/c
C36H40CuN2O4
628.24
292(2)
0.71073
monoclinic
P2(1)/c
C42H40CuN2O2
668.3
292(2)
0.71073 Å
monoclinic
P2(1)/c
C32H48CuN2O2
556.26
293(2)
0.71073
monoclinic
P2(1)/n
Space group
Unit cell dimensions (Å)
a = 18.031 (4)
b = 19.315 (4)
c = 6.6500 (10)
–
2316.0 (8)
4, 1.274
a = 12.4516 (10)
b = 5.9692 (5)
c = 20.5661 (17)
b = 90.349 (7)
1528.6 (2)
a = 17.9630 (4)
b = 6.98550 (10)
c = 26.4128 (7)
b = 90.091 (2)
3314.29 (12)
4, 1.259
a = 12.4325 (17)
b = 7.1542 (13)
c = 19.891 (4)
b = 104.062 (14)
1716.2 (5)
a = 13.823 (3)
b = 17.846 (4)
c = 13.031 (3)
b = 102.05 (3)
3143.7 (12)
4, 1.175
Volume (Å3)
Z, density (calc.) (Mg/m3)
2, 1.295
0.749
2, 1.293
0.675
Absorption coeff. (mmꢁ1
)
0.964
0.699
0.723
Maximum and minimum transmission 0.8934 and 0.6243
0.8528 and 0.7823
630
0.8975 and 0.7205
1324
0.9072 and 0.7025
702
0.9457 and 0.6436
1196
F(0 0 0)
940
Crystal size (mm)
h Range for data collect (°)
Limiting indices
0.54 ꢀ 0.23 ꢀ 0.12
2.11–26.00
ꢁ22 P h 6 22
ꢁ23 P k 6 23
ꢁ7 P l 6 8
0.34 ꢀ 0.23 ꢀ 0.22
2.56–31.18
ꢁ17 P h 6 18
ꢁ7 P k 6 8
26 P l 6 29
14 478
0.50 ꢀ 0.32 ꢀ 0.16
2.27–28.57
ꢁ23 P h 6 22
ꢁ9 P k 6 9
ꢁ35 P l 6 33
33 424
0.56 ꢀ 0.24 ꢀ 0.15
2.36–26.00
ꢁ15 P h 6 15
ꢁ6 P k 6 8
ꢁ24 P l 6 24
12 105
0.67 ꢀ 0.63 ꢀ 0.08
2.26–31.35
ꢁ20 P h 6 19
ꢁ24 P k 6 25
ꢁ14 P l 6 18
30 796
Reflected collected
Independent reflect
Completeness
14 438
2949; R(int) = 0.0334
99.90%
4656; R(int) = 0.0329
99.80%
7746; R(int) = 0.0273
99.90%
3366; R(int) = 0.139
99.80%
9595; R(int) = 0.0850
99.90%
Data/restraints/param.
2490/0/181
1.207
4656/0/190
1.11
7746/0/388
1.054
3366 0/214
1.2095
9595/18 3
1.028
Goodness-of-fit (GOF)on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0541,
wR2 = 0.1391
R1 = 0.0661,
wR2 = 0.1432
0.466 and ꢁ0.945
R1 = 0.0398,
wR2 = 0.0998
R1 = 0.0570,
wR2 = 0.1073
0.330 and ꢁ0.299
R1 = 0.0384,
wR2 = 0.1076
R1 = 0.0557,
wR2 = 0.1132
0.730 and ꢁ0.294
R1 = 0.0710,
wR2 = 0.1797
R1 = 0.0854,
wR2 = 0.1937
0.382 and ꢁ0.742
R1 = 0.0566,
wR2 = 0.1414
R1 = 0.0999,
wR2 = 0.1647
0.559 and ꢁ0.465
Largest difference in peak and hole
(e Åꢁ3
)
Table 2
Selected bond lengths (Å) and angles (°) for complex structures L12Cu, L32Cu, L25Cu, L62Cu and L201Cu.
L’12Cu
L12Cu
L12Cu
L23Cu
L23Cu
L52Cu
L52Cu
L62Cu
L62Cu
L021Cu
Cu1–O21
Cu1–O1
Cu1–N21
Cu1–N1
1.879(3)
1.887(3)
1.994(4)
1.9967(4)
179.44(14)
91.84(15)
88.72(15)
87.54(15)
91.90(15)
179.38(15)
130.0(3)
124.6(3)
119.7(3)
130.5(3)
124.2(3)
120.3(3)
Cu1–O1#1
Cu1–O1
Cu1–N1#1
Cu1–N1
O1#1–Cu1–O1
O1#1–Cu1–N1#1
O1–Cu1–N1#1
O1#1–Cu1–N1
O1–Cu1–N1
N1#1–Cu1–N1
C1–O1–Cu1
C7–N1–Cu1
1.8798(12)
1.8798(12)
1.9999(12)
1.9999(12)
180.00(10)
91.68(5)
88.32(5)
88.32(5)
91.68(5)
180.00(10)
129.41(11)
123.37(10)
121.84(10)
129.41(11)
123.37(10)
121.84(10)
Cu1–O21
Cu1–O1
Cu1–N21
Cu1–N1
1.8760(14)
1.8783(13)
1.9664(14)
1.9758(15)
143.95(6)
95.72(6)
98.11(6)
96.22(6)
94.40(6)
139.69(6)
127.54(12)
123.73(13)
116.97(11)
126.12(12)
122.08(12)
118.24(11)
Cu1–O1#1
Cu1–O1
Cu1–N1#1
Cu1–N1
1.870(3)
1.870(3)
1.994(3)
1.994(3)
180.0
91.79(12)
88.22(12)
88.22(12)
91.79(12)
180.0
128.9(2)
123.7(3)
120.7(2)
128.9(2)
123.7(3)
120.7(2)
Cu1–O2
Cu1–O1
Cu1–N2
Cu1–N1
1.8913(16)
1.9026(18)
1.9442(19)
1.9600(19)
156.97(8)
93.20(8)
92.05(8)
91.19(7)
92.00(8)
158.73(9)
126.34(15)
122.74(16)
119.02(16)
128.54(15)
123.70(17)
119.69(17)
O21–Cu1–O1
O21–Cu1–N21
O1–Cu1–N21
O21–Cu1–N1
O1–Cu1–N1
N21–Cu1–N1
C1–O1–Cu1
C7–N1–Cu1
C8–N1–Cu1
C21–O21–Cu1
C27–N21–Cu1
C28–N21–Cu1
O21–Cu1–O1
O21–Cu1–N21
O1–Cu1–N21
O21–Cu1–N1
O1–Cu1–N1
N21–Cu1–N1
C1–O1–Cu1
C7–N1–Cu1
C8–N1–Cu1
C21–O21–Cu1
C27–N21–Cu1
C28–N21–Cu1
O1#1–Cu1–O1
O2–Cu1–O1
O2–Cu1–N2
O1–Cu1–N2
O2–Cu1–N1
O1–Cu1–N1
N2–Cu1–N1
C1–O1–Cu1
C7–N1–Cu1
C16–N1–Cu1
C21–O2–Cu1
C27–N2–Cu1
C36–N2–Cu1
O1#1–Cu1–N1#1
O1–Cu1–N1#1
O1#1–Cu1–N1
O1–Cu1–N1
N1#1–Cu1–N1
C11–O1–Cu1
C9–N1–Cu1
C1–N1–Cu1
C11#1–O11#1–Cu1
C9#1–N1#1–Cu1
C1#1–N1#1–Cu1
C8–N1–Cu1
C1#1–O1#1–Cu1
C7#1–N1#1–Cu1
C8#1–N1#1–Cu1
Symmetry transformations used to generate equivalent atoms: L23Cu #1ꢁx,ꢁy,ꢁz; L26Cu #1 ꢁx + 1,ꢁy,ꢁz.

E. Safaei et al. / Inorganica Chimica Acta 366 (2011) 275–282
279
the ligand are almost perpendicular to each other, and the dihedral
angle between their best planes is 77.53°.
The asymmetric part of structure of L52Cu contains the whole
complex molecule (Fig. 3). Replacement of benzyl with phenyl
group bound to N atom increases the steric hindrance within the
coordination sphere, when compared to L23Cu. The dihedral angle
between the phenolic ring and the phenyl ring in the ligand differs
significantly for two ligands. It is 50.67° between C1–C6 and C8–
C13 and only 25.69° between C21–C26 and C28–C33 rings. That re-
sults from different inter-molecular interactions of both phenyl
rings. The C8–C13 ring interacts with its equivalent related by
[2ꢁx,1ꢁy,ꢁz] transformation, the distance between the centers of
gravity being 4.291 Å. Contrary, the C28–C33 ring forms the inter-
action to the chelate ring Cu1–O21–C21–C26–C27–N21, with the
distance between their centers of gravity being 3.824 Å.
Fig. 1. ORTEP diagram and atom labeling scheme for complex L12Cu. Atoms denoted
A are related to the basic set by the mirror plane symmetry transformation [x,y,1/
2ꢁz]. Hydrogen atoms in the disordered tert-Bu group are not displayed.
Structure of L12Cu is build up with the complexes molecule posi-
tioned on the mirror plane in the Pbcm space group. Consequently,
the square-planar coordination sphere has no deformations con-
nected to the donor atom displacement from that plane. The struc-
ture analysis revealed the rotational disorder of the tert-Bu group
of one ligand, with all methyl groups positioned out of the mirror
plane (Fig. 1). That resulted in two populations of that group re-
lated by the mirror plane symmetry [x,y,1/2ꢁz], both populated
50%. In the second ligand, one methyl group of tert-Bu is positioned
exactly on the mirror plane, while remaining pair is related by the
mirror plane. The N-bound C8 and C28 methyl groups in both li-
gands are also positioned in the mirror plane. Consequently for
each of them, one H atom is located on that plane, while two other
are related by the mirror plane symmetry. Crystal packing analysis
revealed the parallel orientation of the complex molecules. The
distance between centers of gravity of the Cu1–O1–C1–C6–C7–
N1 chelate ring and its equivalent transformed with [x,1/2ꢁy,ꢁz]
is 3.4809(8) Å, while for chelate Cu1–O21–C21–C26–C27–N21 ring
and its [x,1/2ꢁy,ꢁz] equivalent it is 3.3529(7) Å. In such orientation
of the molecules, there is a short Cu1. . .Cu1[x,1/2ꢁy,ꢁz] distance of
3.3405(7).
The asymmetric part of L62Cu contains a half of the molecule
with the Cu positioned on the center of symmetry (Fig. 4). The
other part is generated by the center of symmetry with [ꢁx + 1,
ꢁy, ꢁz] transformation. The possible steric hindrance caused by
the N-naphtyl moiety is decreased by the rotation around the sin-
gle N1–C1 bond, with the torsion angle C9–N1–C1–C2 of 61.8(5)°.
Analysis of crystal packing reveals the C2–H...
p interaction with
the phenolic C10–C15 ring transformed by [1ꢁx,1ꢁy,ꢁz], the dis-
tance between C–H and center of gravity of the ring being 2.78 Å.
Structure of L23Cu is centrosymmetric, with the Cu(II) positioned
on the center of symmetry (Fig. 2). The ligand contains the N-
benzyl moiety much larger that the N-methyl present in L12Cu. The
steric hindrance between the phenolate in the coordination sphere
and the N-bound benzyl moiety is minimized by the rotation
around N1–C8 and C8–C9 bonds, with the consecutive torsion an-
gles in the C7–N1–C8–C9–C10 fragment being 88.12(16) and
ꢁ123.14(17)°. The C6–C7–N1–C8 fragment is planar, with the tor-
sion angle ꢁ174.94(15). The phenolic ring and the phenyl ring in
Fig. 3. ORTEP diagram and atom labeling scheme for complex L52Cu.
Fig. 2. ORTEP diagram and atom labeling scheme for complex L23Cu. Half of the
molecule constitutes the asymmetric part of the structure. Ligand denoted with A is
generated by the center of symmetry transformation [ꢁx, ꢁy, ꢁz].
Fig. 4. ORTEP diagram and atom labeling scheme for complex L62Cu. Half of the
complex molecule constitutes the asymmetric part of the structure. Ligand denoted
with A is generated by the center of symmetry transformation [ꢁx + 1, ꢁy, ꢁz].

280
E. Safaei et al. / Inorganica Chimica Acta 366 (2011) 275–282
Contrary to the above structures, the L52Cu and L201Cu complexes
reveal significant deviations of the coordination sphere from the
square planar CuN2O2. In the L01Cu structure the significant steric
2
repulsion between N-methyl and tert-Bu substituent in position
2 of the phenolate ring causes the deformation of the Cu coordina-
tion sphere, with the N–Cu–N and O–Cu–O angles being 158.73(9)
and 156.97(8)°, respectively. Also the dihedral angle between the
best planes of two chelate rings is 40.29(7)°. The intra-ligand
O–Cu–N angles of 92.00(8) and 93.20(8)° are larger than the
inter-ligand angles being 92.05(8) and 91.19(7)°.
In L52Cu the bulk of phenyl-OMe bound to imine N results in the
values of O–Cu–O and N–Cu–N angles far from the expected 180°,
and being 143.95(6) and 139.69(6)°, respectively. The dihedral an-
gle between best planes of two chelate rings is 53.38(4)°, and that
is the largest deformation in the investigated series. Opposite to all
other reported complexes, the intra-ligand O–Cu–N angles are
94.40(6) and 95.72(6)°, while the inter-ligand angles are slightly
larger, being 98.11(6) and 96.22(6)°. The largest deviation of the
coordination sphere from planarity and the difference in relation
between the intra- and inter-ligand O–Cu–N angles strongly indi-
cate the effect of the bulky naphthyl moiety affecting the intramo-
lecular geometry.
0
Fig. 5. ORTEP diagram and atom labeling scheme for complex L1 2Cu. Hydrogen
atoms of the disordered tert-Bu groups are omitted for clarity.
In the L021Cu structure the whole complex molecule constitutes
the asymmetric part of the structure (Fig. 5). Two tert-Bu substit-
uents in the phenolic ring reveal different rotational flexibility,
depending on their position relative to the oxygen atom. In both li-
gands, rotation of the group bound in position 2 is limited, while
those positioned para relative to oxygen reveal rotational disorder.
That seems to be characteristic for the investigated series of
complexes, even in L52Cu, where large atomic displacement param-
eters for tert-Bu are observed, although no discrete model for the
disorder can be formulated. The only exception is L23Cu in which
3.2. Magnetic susceptibility measurements
Magnetic susceptibility
v was measured in magnetic field of
1000 Oe as a function of temperature in the range 2–300 K. The
measured data were corrected for the temperature independent
Larmor diamagnetic susceptibility obtained from Pascal’s tables
[34] and for sample holder contribution. Typical magnetic diagram
such disorder does not occur. In L021Cu the C36–H36A...
p interaction
is found with the 2.83 Å distance of C–H to the center of gravity
of C1–C6 phenolic ring related by the [x,1/2ꢁy,ꢁ1/2 + z]
transformation.
For all structures reported here, the coordination sphere geom-
etry is square-planar in all investigated structures and the trans
arrangement of donor atom is found. The search in the CSD
database [32] revealed that for complexes formed with the similar
ligands, most of them has the trans architecture of the CuN2O2
coordination sphere. The only exception is that of bis((2-(20-
(40,60-di-t-butyl)phenoxy))-4,5-diphenylimidazole-N,O)-copper(ii)
reported by Benisvy et al. [33]. In that structure the steric demands
of the imidazole moiety seems to result in the cis arrangement of
the ligands.
is presented in Fig. 6 in the form of
v
and a product
v*T (inset) vs.
T. The variation of the susceptibility
v vs. T for T > 50 K can be well
fitted by a Curie–Weiss law. The obtained Curie constants were
around 0.4 emu K/mol (0.39 emu K/mol < C < 0.42 emu K/mol) and
Curie–Weiss temperatures ꢁ1.3 K ꢂ h ꢂ +0.12 K. The effective
magnetic moments (leff) calculated from the Curie constants are
in the range 1.77–1.83
lB for all complexes indicating one unpaired
electron on the copper center in the monomer complexes (SCu = 1/
2). These values are very close to the spin only value of 1.73 lB
[35–37] what is expected for the copper centers separated by large
distances (>5 Å). Small values of Curie–Weiss temperatures h and
slight downturn of
v*T (T) below 20 K indicate only a very weak
interaction between the cooper monomers.
In the structures reported here, the Cu–O bonds formed by the
phenolic oxygen atoms range between 1.870(3) and 1.9026(18) Å,
and are shorter than those formed by the nitrogen atoms
1.9442(19) and 1.9999(12) Å. That might be attributed to the elec-
trostatic character of the interaction between negatively charged
phenolate O and central Cu(II).
0.4
H = 1000 Oe
0.10
0.05
0.00
0.3
0.2
0.1
0.0
In our research, the mirror plane symmetry of the L12Cu complex
molecule enforces the lack of displacement of atoms from the coor-
dination plane. The O–Cu–O and N–Cu–N angles within the copper
coordination sphere are 179.44(14) and179.35(15)°, respectively.
The intra-ligand N–Cu–O angles [91.80(15) and 91.89(15)°] are sig-
nificantly larger that the inter-ligand angles of 88.75(15) and
87.55(15)°. This effect might be explained by the larger influence
of relative rigidity of the phenolate-imine moiety compared to
the steric effect of N-Met moiety in the ligand.
T
0
100
200
300
T (K)
Due to the centrosymmetric architecture of complexes L23Cu and
L62Cu, only a small deformation of the coordination sphere is found,
with the O–Cu–O and N–Cu–N angles being 180.0°. The intra-li-
gand N–Cu–O angles in these complexes are 91.68(5) and
91.79(12) L23Cu and L62Cu, respectively, and are slightly larger than
the inter-ligand N–Cu–O angles of 88.32(5) and 88.22(12)°. This is
analogous to the difference revealed by the L12Cu structure.
0
100
200
300
T (K)
Fig. 6. Temperature dependence of magnetic susceptibility
v and a product of v*T
(inset) as a function of temperature for the sample L52Cu measured in magnetic field
of 1000 Oe. The full line is a fit with a Curie–Weiss law. For all other samples
(except L12Cu) very similar temperature dependencies were obtained.

E. Safaei et al. / Inorganica Chimica Acta 366 (2011) 275–282
281
H = 1000 Oe
0.04
0.02
0.00
0.04
0.02
0.00
Tmax
0
2 4 6 8 10 12 14 16 18 20
T (K)
0
100
200
300
T (K)
Fig. 7. Temperature dependence of magnetic susceptibility
v as a function of
temperature for the sample L12Cu measured in magnetic field of 1000 Oe. The full
line is a fit with a Curie–Weiss law. Inset shows the position of the maximum of
susceptibility in an extended temperature scale.
Fig. 8. Cyclic voltammogramms of L02Cu at ꢁ40 °C and scan rates of 100, 200, 300
and 400 mV/s.
The only exception from pure paramagnetic behavior is the
sample L12Cu. The magnetic susceptibility
v increases with decreas-
Table 3
ing temperature for T > 50 K as in the other samples (Fig. 7).
However it exhibits a well pronounced cusp at a Tmax = 3.5 K
with a maximal value of vmax ꢃ 0.04 emu/mol. The observed
temperature-dependent magnetic susceptibility demonstrates an
antiferromagnetic coupling between copper centers of neighbor
complexes. This is consistent with the smaller Cu1. . .Cu1[x,1/
2ꢁy,ꢁz] distance of 3.3405(7) Å found in the crystal structure re-
ported here. The Curie constant C for high temperature region
Electrode potentials (in V) for oxidation and reduction of copper complexes measured
at ꢁ40 °C in CH2Cl2 solutions and referenced vs. the Fc+/Fc couple.
Complexes
E1a/V vs. (Fc+/Fc)
E2a/V vs. (Fc+/Fc)
L12Cu
L22Cu
L23Cu
L42Cu
L52Cu
L62Cu
L021Cu
L022Cu
0.95
0.84
1.04
0.68
0.71
0.67
0.67
0.98
1.19
1.29
1.58
1.48
1.32
1.1
(T > 50 K) is 0.39 (leff = 1.77 lB) as in the other samples. However,
the Curie–Weiss temperature h = ꢁ3.9 K is larger compared to
other samples. X-ray crystallography of this complex shows a lay-
ered structure in which copper centers are separated by a distances
of around 3 Å, that favors an antiferromagnetic interaction. The
coupling constant J between Cu2+ ions was estimated from the po-
sition of the Tmax using the relation: Tmax/(|J|ꢄSꢄ(S + 1)) = 2.495
which valid for antiferromagnetic square planar lattice. For Cu2+
ions S = 1/2 and the obtained coupling constant J = ꢁ1.3 cmꢁ1[38].
1.22
a
Irreversible reaction, peak potential is given.
that the second oxidation potential of these complexes are more
positive than that for the first ones probably due to the harder oxi-
dation of radical cation complexes producing biradical ones.
These ligand-centered voltammograms are electrochemically
irreversible, what is seen from the high separation of the peaks
3.3. Electrochemistry
of reduction and re-oxidation (DEp = Epa_Epc). In addition, the cur-
rent relationship (ipa/ipc) is less than unity in each case.
Cyclic, square wave and differential pulse voltammograms (CV,
Comparing the oxidation potentials of mono and di-tert-butyl-
SQW and DPV) of complexes L2Cu and L0 Cu have been recorded in
ated N-alkyl-salicylaldiminato copper complexes (L2Cu and L0 Cu)
2
2
CH2Cl2 solutions containing 0.1 M [(nBu)4N]ClO4 or LiClO4 as sup-
porting electrolyte. Prior to the measurement, the GC electrode
was polished with 0.1 mm alumina powder and washed with dis-
tilled water. The voltage scan rate was set at 50 mV sꢁ1. The solu-
tions were deoxygenated by bubbling nitrogen gas through them.
Ferrocene was added as an internal standard after completion of
a set of experiments, and potentials are referenced versus the fer-
rocenium/ ferrocene couple (Fc+/Fc).
suggesting that anodic oxidation processes are less sensitive to
the involved change in bulkiness on tert-butylated phenolic moie-
ties of the ligands (Table 3).
On the other hand, the lower oxidation potentials of L42Cu, L25Cu
and L62Cu with aromatic groups directly attached to the imine
nitrogens are probably associated with the sensitivity of anodic
oxidation potentials to the involved change in mentioned groups.
The metal-centered voltammograms have been observed in the
negative potential range, what corresponds to the CuII/CuI reduc-
The CV voltammograms (Fig. 8) observed for all complexes re-
vealed two oxidations (E1ox and E2ox) except for L1Cu, which exhibits
tion of L2Cu and L0 Cu. They are chemically irreversible what sug-
2
2
one oxidation. Selected results are collected in Table 3. Typical cyc-
gests the instability of the reduced species.
lic voltammograms (CV) of L02Cu1 are presented in Fig. 8.
Eo1x and Eo2x are nearly similar for mentioned complexes, what
suggests that the oxidation mechanism might be the same for all
complexes. These redox processes were assigned to the ligand-cen-
tered oxidation yielding the phenoxyl radical in the complex. The
second oxidation potential (Eo2x) are most probably arising from
the oxidation of second phenolate moiety of this complexes, but
there is no direct evidence for this interpretation. It is worth noting
4. Conclusion
We have prepared and characterized Cu(II) complexes contain-
ing bulky salicylaldimine ligands. The X-ray crystallography
analysis shows that all complexes are monomer and their cop-
per(II) centers have been surrounded by phenolate oxygens and

282
E. Safaei et al. / Inorganica Chimica Acta 366 (2011) 275–282
[3] J. Stubbe, W.A. van der Donk, Chem. Rev. 98 (1998) 705.
[4] J. Stubbe, Chem. Commun. (2003) 2511.
[5] J.W. Whittaker, Chem. Rev. 103 (2003) 2347.
[6] R. Banerjee, Chem. Rev. 103 (2003) 2081.
[7] H. Sigel, A. Sigel, Metal Ions in Biological Systems, vol. 30, Marcel Dekker, New
York, 1994. pp. 315–403.
imine nitrogen atoms. Therefore, the coordination sphere around
the copper atoms is N2O2 as seen in galactose oxidase active site.
In addition, the geometry around the metal ion of all complexes
are square planar or slightly distorted square planar with the trans
arrangement. The crystal systems of most reported complexes are
monoclinic, except L12Cu for which the orthorhombic crystal sys-
tem was detected.
Oxidation of the Cu(II) complexes yielded the corresponding
Cu(II)- phenoxyl radical species during the cyclic voltammetry
experiments. The steric and electronic effects of substituent con-
nected to phenol and imine groups on oxidation potential have
been investigated.
[8] N. Ito, S.E.V. Phillips, C. Stevens, Z.B. Ogel, M.J. McPherson, J.N. Keen, K.D.S.
Yadav, P.F. Knowles, Nature 350 (1991) 87.
[9] M.J. McPherson, M.R. Parsons, R.K. Spooner, C.M. Wilmot, Galactose oxidase,
in: K. Wieghart, T.L. Poulos, R. Huber, A. Messerschmidt (Eds.), Handbook of
Metalloproteins, vol. 2, Wiley, New York, 2001, pp. 1245–1257.
[10] M.M. Whittaker, J.W. Whittaker, Biophys. J. 64 (1993) 762.
[11] J.P. Klinman, Chem. Rev. 96 (1996) 2541.
[12] J.W. Whittaker, in: K.D. Karlin, Z. Tyeklar (Eds.), Bioinorganic Chemistry of
Copper, Chapman Hall, New York, 1993, pp. 447–458.
[13] M.M. Whittaker, P.J. Kersten, N. Nakamura, J. Sanders-Loehr, E.S. Schweizer,
J.W. Whittaker, J. Biol. Chem. 271 (1996) 681.
The observed temperature dependent magnetic susceptibility
(v
) for L12Cu was consistent with antiferromagnetic coupling be-
[14] M.M. Whittaker, V.L. DeVito, S.A. Asher, J.W. Whittaker, J. Biol. Chem. 264
(1989) 7104.
tween copper centers of neighbor complexes. The effective mag-
netic moment ( eff) for all other complexes are lie in the range
1.77–1.83 B, indicative of an unpaired electron on copper center
[15] P.F. Knowles, N. Ito, in: R.W. Hay, J.R. Dilworth, K.B. Nolan (Eds.), Perspectives
in Bio-inorganic Chemistry, vol. 2, Jai, London, 1994.
[16] Y.K. Lee, M.M. Whittaker, J.W. Whittaker, Biochemistry 47 (2008) 6637.
[17] N. Ito, S.E.V. Phillips, K.D.S. Yadav, P.F. Knowles, J. Mol. Biol. 238 (1994) 794.
[18] R.M. Wachter, M.P. Montague-Smith, B.P. Branchaud, J. Am. Chem. Soc. 119
(1997) 7743.
l
l
in monomer complexes(SCu = 1/2). The effects of the structural fac-
tors of bulky tBu groups contributing to the effective magnetic mo-
ment have been described.
[19] B.P. Branchaud, M.P. Montague-Smith, D.J. Kosman, F.R. McLaren, J. Am. Chem.
Soc. 115 (1993) 798.
[20] R.M. Wachter, B.P. Branchaud, J. Am. Chem. Soc. 118 (1996) 2782.
[21] M.M. Whittaker, J.W. Whittaker, J. Am. Chem. Soc. 114 (1992) 3727.
[22] Brian A. Jazdzewski, William B. Tolman, Coord. Chem. Rev. 200-202 (2000)
633.
[23] A.L. Philibert, F. Thomas, C. Philouze, S. Hamman, E. Saint-Aman, J.L. Pierre,
Chem. Eur. J. 9 (2003) 3803.
[24] P. Chaudhuri, M. Hess, U. Flörke, K. Wieghardt, Angew. Chem., Int. Ed. 37
(1998) 2217.
[25] Y. Wang, J.L. DuBois, B. Hedman, K.O. Hodgson, T.D.P. Stack, Science 279 (1998)
537.
[26] S. Itoh, M. Taki, S. Fukuzumi, Coord. Chem. Rev. 198 (2000) 3.
[27] F. Michel, F. Thomas, S. Hamman, C. Philouze, E. Saint-Aman, J.L. Pierre, Eur. J.
Inorg. Chem. (2006) 3684.
[28] J.F. Larrow, E.N. Jacobsen, Y. Gao, Y. Hong, X. Nie, C.M. Zepp, J. Org. Chem. 59
(1994) 1939.
Acknowledgments
The Authors are grateful to the Institute for Advanced Studies in
Basic Sciences (IASBS) Nicolaus Copernicus University, University
of Ljubljana, and Changwon National University, for their valuable
helps. E. Safaei gratefully acknowledges support by the Institute for
Advanced Studies in 514 Basic Sciences (IASBS) Research Council
under Grant No. G2010IASBS127.
Appendix A. Supplementary material
[29] I. Sylvestre, J. Wolowska, C.A. Kilner, E.J. McInnes, M.A. Halcrow, Dalton Trans.
19 (2005) 3241.
[30] G.M. Sheldrick, SHELXS97 and SHELXL97, University of Gottingen, Germany,
Supplementary data CCDC, 784748, 784749, 784750, 784751,
and 784752 contain the supplementary crystallographic data for
L12Cu, L32Cu, L52Cu, L62Cu and L1’2Cu, respectively. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.ica.2010.11.017.
}
1997.
[31] CrysAlis CCD171 and RED171 Package of Programs, Oxford Diffraction, 2000.
[32] F.H. Allen, Acta Cryst. B58 (2002) 380.
[33] L. Benisvy, A.J. Blake, D. Collison, E.S. Davies, C.D. Garner, E.J.L. McInnes, J. Mc
Master, G. Whittaker, C. Wilson, Dalton Trans. (2003) 1975.
[34] R.L. Dutta, A. Syamal, Elements of Magnetochemistry, Affiliated East-West
Press PVT Ltd., 1993. p. 8.
[35] L. Sacconi, Coord. Chem. Rev. 1 (1966) 126.
References
[36] L. Sacconi, M. Ciampolini, J. Chem. Soc. (1964) 276.
[37] B.J. Hathaway, A.A.G. Tomlinson, Coord. Chem. Rev. 5 (1970) 1.
[38] L.J. De Jongh, Magnetic Properties of Layered Transition Metal Compounds,
Kluwer Academic Publishers, 1990. p. 143.
[1] R.H. Holm, P. Kennepohl, E. Solomon, Chem. Rev. 96 (1996) 2239.
[2] H.C. Liang, M. Dahan, K.D. Karlin, Science 3 (1999) 168.