Syntheses and characterization of copper(II) complexes of the new ligands N-[(2-pyridyl)methyl]-2,2′-dipyridylamine and N-[bis(2-pyridyl)methyl]-2-pyridylamine

Article abstract of DOI:10.1002/1099-0682(20021)2002:1<111::AID-EJIC111>3.0.CO;2-7

The two new ligands N-[(2-pyridyl)methyl]-2,2′-dipyridylamine (L1) and N-[bis(2-pyridyl)methyl]-2-pyridylamine (L2) have been synthesized and the copper(II) complexes [Cu(L1)₂(CH₃OH)₂] (ClO₄)₂, [Cu(L1

Full text of DOI:10.1002/1099-0682(20021)2002:1<111::AID-EJIC111>3.0.CO;2-7

FULL PAPER
Syntheses and Characterization of Copper(II) Complexes of the New Ligands
N-[(2-Pyridyl)methyl]-2,2Ј-dipyridylamine and N-[Bis(2-pyridyl)methyl]-
2-pyridylamine
Simon P. Foxon,[a] Olaf Walter,[b] and Siegfried Schindler*[a]
Keywords: Copper / Oxygen / Coordination chemistry / Ligand effects / Tripodal ligands
The two new ligands N-[(2-pyridyl)methyl]-2,2Ј-dipyridyl-
amine (L1) and N-[bis(2-pyridyl)methyl]-2-pyridylamine
(L2) have been synthesized and the copper(II) complexes
[Cu(L1)2(CH3OH)2](ClO4)2, [Cu(L1)2(H2O)2](ClO4)2, [Cu3-
(L1)2(DMF)2Cl6], [Cu(L1)Cl2]n, [Cu(L2)(Cl)(ClO4)], and
[Cu(L2)Cl2] have been structurally characterised. The reac-
tions of dioxygen with the copper(I) complexes with ligands
L1 and L2 were investigated, but no copper−dioxygen inter-
mediates could be detected spectrophotometrically.
Introduction
the copper ion, the CuII/CuI redox couple, and spectro-
scopic features (UV/Vis, EPR).
The properties of these complexes were found to be
strongly affected by changing the chelate ring size and,
therefore, we also became interested in performing a similar
investigation in which the tripodal ligand, tmpa, had each
‘‘arm’’ systematically shortened (Scheme 1). The tripodal
amine, tris(2-pyridyl)amine (tpa; unfortunately tmpa has
also been abbreviated as tpa in the literature) has been
known for a long time,[24] but the two ligands -[(2-pyridyl)-
methyl]-2,2Ј-dipyridylamine (L1) and -[bis(2-pyridyl)me-
thyl]-2-pyridylamine (L2), intermediate between tmpa and
tpa, are as yet unknown in the literature.
A large number of biologically important metalloproteins
utilise copper ions in their active sites for the redox-pro-
cessing of molecular dioxygen.[1Ϫ6] Examples include hemo-
cyanin (O2 carrier in the blood of arthropods and mol-
luscs), tyrosinase ( -phenol monooxygenase), and other ox-
idases, which couple oxidation of the substrate with copper-
mediated reduction of dioxygen to hydrogen peroxide or
water.[7Ϫ11]
The function of the metalloprotein is closely related to
the structure of its active site, i.e. the geometrical arrange-
ment of amino acid residues around the copper ions. There
has been considerable interest in the design of ligands and
the characterisation of copper complexes that may consti-
tute models of the active site structure in such
metalloproteins.[1,4Ϫ6,12Ϫ16] In particular, copper complexes
of tris(2-pyridylmethyl)amine (tmpa) and closely related li-
gands have been widely employed in order to explore and
understand the thermodynamic and kinetic aspects of the
reaction of copper(I) compounds with dioxygen.[1,17Ϫ22]
We recently carried out a detailed study on a family of
three ligands closely related to tmpa, in which each ‘‘arm’’
of the tripodal parent ligand tmpa was systematically
lengthened by the insertion of a methylene spacer group.[23]
This systematic approach allowed an evaluation of the ef-
fect of the chelate ring size on the following properties: cop-
per(I)-oxygen reactivity, the coordination geometry around
[a]
Institute of Inorganic Chemistry, University of Erlangen-
Nürnberg,
Scheme 1. The ligands tpa, L1, L2, and tmpa
Egerlandstraße 1, 91058 Erlangen, Germany
Fax: (internat.) ϩ 49-(0)9131Ϫ85 27 387
E-mail: schindls@anorganik.uni-erlangen.de
Herein, we report the synthesis of these two new ligands
and the characterisation of their copper(II) complexes, as
[b]
ITC-CPV, Forschungszentrum Karlsruhe GmbH, ITC-CPV,
Postfach 3640, 76021 Karlsruhe, Germany
2002, 111Ϫ121
WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002
1434Ϫ1948/02/0101Ϫ0111 $ 17.50ϩ.50/0
111

S. P. Foxon, O. Walter, S. Schindler
FULL PAPER
well as some preliminary studies of the reactivity of the cop-
per(I) complexes with dioxygen.
It should be noted that the proposed formulae obtained
on the basis of elemental analyses of the copper(II) com-
plexes differ from the structures obtained by single-crystal
X-ray diffraction studies. This is due to the removal of solv-
ent molecules from the crystal lattices in preparing samples
for elemental analysis.
Results and Discussion
The ligands
-[(2-pyridyl)methyl]-2,2Ј-dipyridylamine
X-ray Structures
(L1) and -[bis(2-pyridyl)methyl]-2-pyridylamine (L2) were
synthesized by nucleophilic substitution reactions of the
precursor amines with 2-picolyl chloride (Scheme 2). The
resulting ligands were isolated in multigram quantities in
modest yields. The two ligands are crystalline solids and
were obtained in a highly pure state by recrystallisation
from an appropriate solvent (see Exp. Sect.).
A summary of the crystallographic data and refinement
parameters for the structures reported in this study can be
found in Table 1. Selected bond lengths and angles for the
copper(II) complexes are reported in Table 2.
Ligand L1
Crystals of L1 were obtained by slow evaporation of the
solvent from a solution of the ligand in acetonitrile at room
temperature. An ORTEP representation of the crystal struc-
ture of ligand L1 is shown in Figure 1. The crystal structure
of L1 shows no extraordinary features and is comparable
to the reported structures of tpa and its derivatives.[25,26]
[Cu(L1)2(CH3OH)2](ClO4)2 (1a)
Blue block-shaped crystals of 1a were grown by slow dif-
fusion of diethyl ether into a solution of the complex in
DMF/methanol. The structure of the cation of 1a is shown
in Figure 2, while the coordination parameters around the
copper(II) centre are listed in Table 2.
The structure of 1a (Figure 2) reveals that two molecules
of L1 coordinate to the central copper(II) ion. Each L1 mo-
lecule coordinates to the copper(II) centre through the two
pyridine nitrogen atoms, N(2) and N(3), of the dipyridyl
moiety. Due to the copper ion occupying a crystallographic
inversion centre, the coordinated pyridyl nitrogen atoms
and the copper(II) ion are rigorously coplanar. The equat-
orial ligands form a rectangular rather than a square basal
Scheme 2. Synthesis of the ligands L1 and L2; reagents and condi-
tions: a: KOH/DMSO, room temp., 2 h. b: i. benzene, reflux, 18 h,
ii. NaBH4, 18 h. c: i. NaH, DMF, room temp., 1 h, ii. picolyl chlor-
ide, DMF, room temp., 18 h
The copper(II) complexes used in this study were pre- plane around the copper(II) ion, as is evident from the
i
˚
pared by adding a copper(II) salt to the appropriate ligand. NϪN distances [N(2)ϪN(3) ϭ 2.9627(13) A, N(2)ϪN(3) ϭ
˚
Crystals suitable for single-crystal X-ray diffraction studies 2.7365(13) A]. Two methanol molecules are coordinated to
were obtained either by slow evaporation of the solvent(s) the copper(II) ion in the axial positions. The resulting geo-
from solutions in methanol, water, acetonitrile, or mixtures metry around the copper(II) coordination sphere in 1a can
thereof, or by slow diffusion of diethyl ether into solutions be described as elongated tetragonal [Cu(1)ϪN(2) ϭ
˚
˚
˚
9
of the complexes in DMF or acetonitrile.
2.0181(13) A, Cu(1)ϪN(3) ϭ 2.0150(13) A, Cu(1)ϪO(1) ϭ
L1 is a versatile ligand. It incorporates rigidity in the 2.4187(13) A], which is characteristic of d hexacoordinate
form of the dipyridyl moiety, while ‘‘flexibility’’ is provided copper(II) complexes. Furthermore, the methanol molec-
by the pendant pyridyl ‘‘arm’’. The dipyridyl moiety of L1 ules are not perpendicular to the equatorial plane, which
acts as a rigid bidentate donor to the copper(II) centres and is evident from the angles [N(3)ϪCu(1)ϪO(1) ϭ 94.41(5)°,
it is observed that in the structures presented herein, the N(3)iϪCu(1)ϪO(1) ϭ 85.59(5)°], with each methanol mole-
third pyridyl nitrogen atom does not coordinate to the same cule being
tilted towards the uncoordinated pyridyl
copper(II) centre. We demonstrate in this work that by moiety. This is perhaps unsurprising, considering the inter-
changing the solvent and counteranions a variety of unique esting and unexpected observation of a strong
and different structures incorporating the common motif of
hydrogen bonding interaction between the ‘‘pendant’’
ligand L1 can readily be prepared.
Ligand L2 is closely related to bis(2-pyridylmethyl)amine in the structure of 1a [O(1)···N(4) ϭ 2.7472(13) A].
pyridyl nitrogen N(4) and O(1) of the methanol molecule
˚
(dipica), but has been derivatised by the incorporation of
Although methanol is not a particularly good ligand, es-
an extra pyridine moiety. This introduces the possibility of pecially when bound at the axial coordination positions of
additional coordination and hence the formation of new the JahnϪTeller sensitive copper(II) ion, metal-bound
coordination compounds.
methanol molecules have been observed in transition metal
112
2002, 111Ϫ121

Copper(II) Complexes of New Ligands
FULL PAPER
Table 1. Crystallographic data from the X-ray diffraction studies of L1, 1aϪ1d, 2a, and 2b
L1
1a
1b
1c
1d
2a
2b
Empirical formula
C16H14N4
262.31
200(2)
C34H36Cl2CuN8O10 C38H46Cl2CuN10O12 C44H56Cl6Cu3N12O4 C16H14Cl2CuN4
C17H16Cl2CuN4O4 C17H18Cl2CuN4O
851.14
200(2)
969.28
200(2)
1220.32
200(2)
396.75
200(2)
474.78
200(2)
428.79
200(2)
r
Temperature [K]
˚
Radiation used (λ [A])
Crystal description
Crystal size [mm]
Crystal system
Mo- (0.71073) Mo- (0.71073)
Mo- (0.71073)
Mo- (0.71073)
Mo- (0.71073) Mo- (0.71073)
Mo- (0.71073)
α
α
α
α
α
α
α
colourless block
blue block
0.6 ϫ 0.6 ϫ 0.4
triclinic
blue block
0.8 ϫ 0.8 ϫ 0.5
monoclinic
2/ (No. 15)
23.377(2)
13.6502(13)
14.4648(14)
90
108.3600(10)
90
4380.7(7)
4
blue block
0.3 ϫ 0.2 ϫ 0.2
triclinic
green plates
green block
green plates
0.3 ϫ 0.3 ϫ 0.2
monoclinic
21/ (No. 14)
8.6690(8)
11.8603(11)
17.1999(16)
90
0.6 ϫ 0.6 ϫ 0.3
monoclinic
21/ (No. 14)
8.976(3)
15.083(6)
10.354(2)
90
111.61(2)
90
1303.3(7)
4
0.4 ϫ 0.1 ϫ 0.1
monoclinic
2(1) (No. 4)
7.6273(12)
13.947(2)
7.9549(13)
90
111.556(2)
90
787.1(2)
0.2 ϫ 0.2 ϫ 0.2
monoclinic
21/ (No. 14)
8.2210(5)
14.6760(9)
15.4302(9)
90
¯
¯
Space group
1 (No. 2)
1 (No. 2)
˚
[A]
9.1818(5)
9.9260(6)
11.2268(6)
71.3840(10)
78.2960(10)
69.0490(10)
900.99(9)
1
8.9545(19)
12.024(2)
13.303(3)
82.53(2)
81.60(2)
69.17(2)
˚
[A]
˚
[A]
α [°]
β [°]
γ [°]
[A ]
Z
102.1950(10)
90
91.7060(13)
90
3
˚
1319.6(5)
1
1819.67(19)
4
1767.7(3)
4
2
(000)
552
1.337
0.083
439
1.569
0.825
2012
1.470
0.693
625
1.536
1.555
402
1.674
1.730
964
1.733
1.528
876
1.611
1.551
ρcalcd. [g·cmϪ3
]
µ [mmϪ1
]
Total reflections
Unique reflections
(int)
13336
3128
0.0275
9534
4231
0.0105
22317
5315
0.0166
14042
6240
0.0260
8461
3740
0.0477
19367
4444
0.0512
18264
4314
0.0370
Scan range θ [ °]
Completeness to θmax. [%]
Index ranges
2.51 to 28.32
93.0
1.92 to 28.24
94.9
1.75 to 28.32
93.4
1.82 to 28.29
95.3
2.75 to 28.30
98.5
1.94 to 28.28
94.8
2.09 to 28.29
93.9
Ϫ11 Յ Յ 11
Ϫ19 Յ Յ 19
Ϫ13 Յ Յ 13
3128/0/185
0.0477, 0.1314
0.0540, 0.1377
1.039
Ϫ12 Յ Յ 12
Ϫ12 Յ Յ 12
Ϫ14 Յ Յ 14
4231/0/260
0.0318, 0.0883
0.0340, 0.0902
1.051
Ϫ30 Յ Յ 30
Ϫ18 Յ Յ 18
Ϫ19 Յ Յ 19
5315/0/295
0.0298, 0.0827
0.0323, 0.0852
1.076
Ϫ11 Յ Յ 11
Ϫ16 Յ Յ 16
Ϫ17 Յ Յ 17
6240/0/325
0.0361, 0.0783
0.0545, 0.0835
1.042
Ϫ9 Յ Յ 10
Ϫ18 Յ Յ 18
Ϫ10 Յ Յ 10
3740/1/213
0.0930, 0.2637
0.1191, 0.2836
1.083
Ϫ10 Յ Յ 10
Ϫ19 Յ Յ 19
Ϫ19 Յ Յ 20
4444/0/258
0.0367, 0.0758
0.0618, 0.0846
1.018
Ϫ11 Յ Յ 11
Ϫ14 Յ Յ 15
Ϫ22 Յ Յ 22
4314/0/233
0.0333, 0.0826
0.0412, 0.0875
1.079
Data/restraints/parameters
1,[a][b]
1,[a][d]
Goodness-of-fit on
[
Ͼ 4σ( )][c]
[c] [d]
2 (all data)
2
[e]
Ϫ3
˚
Max./min. el. dens. [e.A
]
0.360, Ϫ0.425
0.749, Ϫ0.429
0.354, Ϫ0.495
0.382, Ϫ0.484
3.918, Ϫ0.665
0.553, Ϫ0.456
0.496, Ϫ0.694
[a]
[b]
[c]
2
1 ϭ Σ|| o| Ϫ | c||/Σ| o|.
Denotes the value of the residual considering only the reflections with Ͼ 4σ( ).
2 ϭ {Σ[ (
Ϫ
o
2)2]/Σ[ ( 2)2]}1/2
;
ϭ 1/[σ2( 2) ϩ ( )2 ϩ
], ϭ [max(
or 0) ϩ 2( 2)]/3. Denotes the value of the residual considering all
2
[d]
c
o
o
Ϫ
o c
[e]
2
the reflections.
ϭ [Σ (
2)2]/[( 1/2], : number of data, : parameters used.
Ϫ )
c
o
complexes, particularly when stabilized by hydrogen bond-
ing within solvated ‘‘cavities’’.[27] A similar observation of there have been surprisingly few structurally characterised
an hydrogen bond between copper(II)-bound copper(II) complexes of tris(2-pyridyl)amine (tpa) reported
In contrast to the well-known ligand tmpa (Scheme 1),
solvent molecules and pendant pyridyl moieties has been in the literature; a search of the Cambridge Structural Data
demonstrated by Mascharak et al. in the case of a ligand Base[29] reveals there to be only four.[30Ϫ33] In three of these
system incorporating an amide functionality.[28]
four examples, two tpa ligands are found to be ligated to
the copper(II) centre, while the other example is a larger
tetrameric array.[33] In all the characterised structures, only
two of the three pyridine nitrogen atoms are found to co-
ordinate to the copper(II) centre. The single-crystal X-ray
structures of the cations of 1a and 1b display similar fea-
tures to those reported for the copper(II) complex [Cu(tpa)2-
(MeCN)2](SO3CF3)2.[32] In this structure, the copper(II) ion
is also found to occupy a crystallographic inversion centre.
The tpa moiety coordinates to the copper(II) centre in an
identical manner as observed for L1, and the two axial sites
are occupied by acetonitrile solvent molecules. The third
pyridine moiety of tpa remains uncoordinated. However,
the crystal structures of 1a and 1b show one notable and
[Cu(L1)2(H2O)2](ClO4)2·2DMF (1b)
The crystal structure of 1b (Figure 3) displays similarities
to that of 1a. The geometry around the copper(II) coor-
dination sphere in 1b can also be described as elongated
˚
tetragonal [Cu(1)Ϫ(N2) ϭ 2.0156(11) A, Cu(1)ϪN(3) ϭ
˚
˚
2.0175(11) A, Cu(1)ϪO(1) ϭ 2.3847(11) A]. In this struc-
ture, there is a dihedral angle of 55.22° between the coord-
inated pyridyl rings of the two L1 ligands. Furthermore,
two water molecules occupy the axial sites of the copper(II)
centre. They each form two strong hydrogen bonds; one
hydrogen bond to the pendant pyridyl ‘‘arm’’
˚
[O(1)ϪN(4) ϭ 2.8396(11) A] and an
hydro-
interesting
difference
from
that
of
[Cu(tpa)2-
gen bond to a DMF solvent molecule [O(1)ϪO(2)DMF ϭ
(MeCN)2](SO3CF3)2. The coordination of methanol molec-
ules to the copper(II) centre of 1a and of water molecules
to the copper(II) centre in 1b is stabilised by
˚
2.7969(11) A]. The copper(II) centre does not lie on an in-
version centre and therefore the basal plane of the four
equatorial nitrogen atoms does not form a perfect square
basal plane.
hydrogen bonds formed between the coordinated solvent
2002, 111Ϫ121
113

S. P. Foxon, O. Walter, S. Schindler
FULL PAPER
˚
Table 2. Selected bond lengths (A) and angles (deg.) for compounds 1a؊1d, 2a, and 2b
1a
Cu(1)ϪN(2)
2.0181(13)
2.0182(13)
180.0
89.29(5)
94.41(5)
Cu(1)ϪN(3)i
2.0150(13)
2.0150(13)
180.0
90.71(5)
85.59(5)
Cu(1)ϪO(1)
2.4187(13)
2.4187(13)
85.45(5)
94.55(5)
90.71(5)
Cu(1)ϪN(2)i
Cu(1)ϪN(3)
Cu(1)ϪO(1)i
N(3)ϪCu(1)ϪN(3)i
N(2)ϪCu(1)ϪO(1)i
N(3)ϪCu(1)ϪO(1)
O(1)ϪCu(1)ϪO(1)i
N(2)ϪCu(1)ϪO(1)
N(3)ϪCu(1)ϪO(1)i
N(3)ϪCu(1)ϪN(2)
N(3)ϪCu(1)ϪN(2)i
N(2)iϪCu(1)ϪO(1)i
Symmetry transformations used to generate equivalent atoms: Ϫ , , Ϫ
1b
Cu(1)ϪN(2)
2.0156(11)
2.0156(11)
92.10(6)
175.56(4)
87.03(4)
Cu(1)ϪN(3)i
2.0174(11)
2.0175(11)
96.86(6)
85.64(5)
96.64(4)
Cu(1)ϪO(1)i
2.3847(11)
2.3847(11)
176.12(6)
86.06(4)
Cu(1)ϪN(2)i
Cu(1)ϪN(3)
Cu(1)ϪO(1)
N(2)iϪCu(1)ϪN(2)
N(2)ϪCu(1)ϪN(3)i
N(3)ϪCu(1)ϪO(1)i
N(3)ϪCu(1)ϪO(1)
N(3)iϪCu(1)ϪN(3)
N(2)ϪCu(1)ϪN(3)
N(2)ϪCu(1)ϪO(1)
O(1)iϪCu(1)ϪO(1)
N(2)ϪCu(1)ϪO(1)i
N(3)iϪCu(1)ϪO(1)
87.03(4)
90.40(4)
Symmetry transformations used to generate equivalent atoms: Ϫ , , Ϫ ϩ 1/2
1c
Cu(1)ϪN(1)
Cu(1)ϪCl(2)
Cu(2)ϪN(4)
N(2)ϪCu(1)ϪN(1)
N(2)ϪCu(1)ϪCl(1)
Cl(2)ϪCu(1)ϪO(1)
N(4)ϪCu(2)ϪCl(3)i
2.0307(19)
2.2687(9)
1.988(2)
Cu(1)ϪCl(1)
Cu(1)ϪO(1)
Cu(2)ϪCl(3)
N(2)ϪCu(1)ϪCl(2)
Cl(2)ϪCu(1)ϪCl(1)
N(4)ϪCu(2)ϪN(4)i
2.2769(8)
2.2870(18)
2.2396(9)
90.05(6)
93.20(3)
180.0
Cu(1)ϪN(2)
Cu(2)ϪN(4)i
2.0161(19)
1.988(2)
84.31(8)
N(1)ϪCu(1)ϪCl(2)
N(2)ϪCu(1)ϪO(1)
N(4)ϪCu(2)ϪCl(3)
168.79(5)
93.57(8)
89.78(6)
170.07(6)
100.93(6)
90.22(6)
Symmetry transformations used to generate equivalent atoms: Ϫ , Ϫ , Ϫ
1d
Cu(1)ϪN(1)
Cu(1)ϪCl(1)
2.421(7)
Cu(1)ϪN(3)
2.027(5)
Cu(1)ϪN(3)i
2.027(5)
84.5(3)
91.03(15)
2.2762(17)
84.64(19)
91.20(10)
Cu(1)ϪCl(1)i
2.2762(17)
168.04(16)
106.01(12)
N(3)ϪCu(1)ϪN(3)i
N(3)ϪCu(1)ϪCl(1)
N(3)ϪCu(1)ϪN(1)
N(3)ϪCu(1)ϪCl(1)i
Cl(1)ϪCu(1)ϪN(1)
Cl(1)iϪCu(1)ϪCl(1)
Symmetry transformations used to generate equivalent atoms: , Ϫ ϩ 1/2,
2a
Cu(1)ϪN(2)
Cu(1)ϪCl(1)
N(2)ϪCu(1)ϪN(1)
N(3)ϪCu(1)ϪCl(1)
O(1)ϪCu(1)ϪN(2)
1.982(2)
2.2265(7)
83.89(8)
99.47(6)
82.88(7)
Cu(1)ϪN(3)
Cu(1)ϪO(1)
N(3)ϪCu(1)ϪN(1)
N(1)ϪCu(1)ϪCl(1)
O(1)ϪCu(1)ϪN(3)
1.991(2)
2.4837(7)
81.39(8)
154.73(6)
89.43(7)
Cu(1)ϪN(1)
2.073(2)
161.15(9)
98.87(7)
104.39(6)
100.87(7)
N(2)ϪCu(1)ϪN(3)
N(2)ϪCu(1)ϪCl(1)
O(1)ϪCu(1)ϪN(1)
O(1)ϪCu(1)ϪCl(1)
2b
Cu(1)ϪN(2)
Cu(1)ϪCl(2)
N(2)ϪCu(1)ϪN(3)
N(2)ϪCu(1)ϪCl(2)
N(2)ϪCu(1)ϪN(1)
Cl(2)ϪCu(1)ϪN(1)
1.9798(17)
2.3271(6)
160.70(7)
91.12(5)
80.89(6)
99.35(4)
Cu(1)ϪN(3)
Cu(1)ϪN(1)
N(2)ϪCu(1)ϪCl(1)
N(3)ϪCu(1)ϪCl(2)
N(3)ϪCu(1)ϪN(1)
1.9836(17)
2.3399(17)
95.39(5)
89.76(5)
79.94(6)
Cu(1)ϪCl(1)
2.2619(6)
N(3)ϪCu(1)ϪCl(1)
Cl(1)ϪCu(1)ϪCl(2)
Cl(1)ϪCu(1)ϪN(1)
96.61(6)
138.82(2)
121.83(4)
molecules and each pendant pyridyl ‘‘arm’’ as discussed analysis revealed that 1c crystallises in the triclinic space
¯
above.
group 1. The structure is shown in Figure 4, while the co-
ordination parameters around the copper(II) centres are
listed in Table 2.
[Cu3(L1)2(DMF)2Cl6]·2DMF (1c)
Crystals of 1c suitable for single-crystal X-ray diffraction
The first striking observation is that the coordination
analysis were grown over a period of a few days by slow complex contains more than one copper ion. The crystal
diffusion of diethyl ether into a solution of the complex in structure reveals a ratio of three copper(II) ions to two L1
DMF at room temperature. Single-crystal X-ray diffraction molecules (Figure 4). The coordination geometry around
114
2002, 111Ϫ121

Copper(II) Complexes of New Ligands
FULL PAPER
Figure 1. ORTEP representation (50% thermal probability ellips-
oids) of the crystal structure of L1
Figure 3. ORTEP representation (50% thermal probability ellips-
oids) of the crystal structure of the cation of 1b; perchlorate anions
have been omitted for clarity
Figure 4. ORTEP representation (50% thermal probability ellips-
oids) of the crystal structure of 1c; two DMF solvent molecules
have been omitted for clarity
centre. In contrast to the two previous structures, however,
Figure 2. ORTEP representation (50% thermal probability ellips-
oids) of the crystal structure of the cation of 1a; perchlorate anions
have been omitted for clarity
N(4) is unable to take part in
hydrogen
bonding interactions with the coordinated anions and solv-
ent molecule. Instead, N(4) coordinates to a second cop-
Cu(1) can be described as being close to square pyramidal, per(II) ion in the structure, Cu(2) [Cu(2)ϪN(4)
with N(1) and N(2) of the dipyridyl moiety of L1 and two 1.988(2) A]. Cu(2) is found to occupy the crystallographic
chloride anions, Cl(1) and Cl(2), forming the square basal inversion centre of the unit cell. Another ligand of L1 is
ϭ
˚
plane [Cu(1)ϪN(2)
ϭ
2.0161(19) A, Cu(1)ϪN(1)
ϭ
coordinated through N(4)i [related to N(4) by the operation
˚
˚
˚
2.0307(19) A, Cu(1)ϪCl(2) ϭ 2.2687(9) A, Cu(1)ϪCl(1) ϭ of inversion at Cu(2)] to Cu(2). A chloride ion Cl(3) and its
2.2769(8) A]. The oxygen atom O(1) of a DMF solvent mo- symmetry-equivalent Cl(3)i complete the coordination
˚
˚
lecule occupies the axial position [Cu(1)ϪO(1)
2.2870(18) A]. The Cu(1) ion is found to be displaced from other anions or DMF solvent molecules are found to oc-
the basal plane by 0.179 A. In common with the two previ- cupy the vacant axial coordination sites of the Cu(2) centre.
ϭ
sphere around Cu(2) [Cu(2)ϪCl(3) ϭ 2.2396(9) A]. No
˚
˚
ously described structures incorporating L1, N(4) of the Due to the crystallographic restraint imposed on Cu(2), the
third pyridyl arm is found not to coordinate to the Cu(1) coordination geometry around the Cu(2) ion can be rigor-
2002, 111Ϫ121
115

S. P. Foxon, O. Walter, S. Schindler
FULL PAPER
ously defined as square planar. Two DMF solvent molec- vealed that no solvent molecules are coordinated to the
ules (not shown) complete the structure.
copper(II) centres. The structure of 1d shows similarities to
that of 1c in that N(4) of the pendant pyridyl ‘‘arm’’ coord-
inates to a neighbouring copper(II) centre. However, in con-
trast to the structure of 1c, the N(4) atom in 1d is found to
occupy the axial coordination position around the square-
pyramidal copper(II) centres, previously occupied by a
DMF molecule in 1c. It is interesting to note that no
bridging by the chloride ion takes place, a common occur-
rence in copper halide polymeric structures.
[Cu(L1)Cl2]n (1d)
Thin plate-like crystals of 1d were grown by slow evap-
oration of the solvents from a solution of the complex in
aqueous acetonitrile. The crystal structure is shown in Fig-
ure 5, while the coordination parameters around the cop-
per(II) centre are listed in Table 2. During the refinement
procedure, high residual electron densities were observed in
the Fourier difference map. This is a direct result of the low
crystal quality (possibly due to extremely thin plates being
stuck together) resulting in high residual electron densities
along the crystallographic twofold screw axis.
[Cu(L2)(Cl)(ClO4)] (2a)
Blue block-shaped crystals of 2a suitable for single-crys-
tal X-ray analysis were grown by slow diffusion of diethyl
ether into a solution in acetonitrile. An ORTEP plot of the
crystal structure is presented in Figure 6. Selected crystallo-
graphic data and bond angles and distances are listed in
Table 1 and 2, respectively.
Figure 5. ORTEP representation (50% thermal probability ellips-
oids) of the crystal structure of 1d
The most striking feature is that 1d has an infinite poly-
meric structure in the solid state. The ORTEP plot in Fig-
ure 5 shows three of the repeating units. The asymmetric
unit cell consists of one half of a molecule of the formula
‘‘[Cu(L1)Cl2]’’. The other symmetry-equivalent ‘‘half’’ of
the structure is generated by reflecting the asymmetric unit
contents through a mirror-plane consisting of the atoms
Cu(1), N(1), N(2), and C(1)ϪC(6). The basal plane around
each copper(II) centre in this structure is identical and is
comprised of two pyridine nitrogen atoms of the dipyridyl
moiety, N(1) and N(2), and two chloride anions, Cl(1) and
˚
Cl(2) [Cu(1)ϪN(1)
ϭ
2.033(14) A, Cu(1)ϪN(2)
ϭ
˚
˚
2.014(14) A, Cu(1)ϪCl(2) ϭ 2.275(5) A, Cu(1)ϪCl(1) ϭ
2.276(5) A]. The third pyridyl ‘‘arm’’ of L1, containing
˚
N(4), is not found to coordinate to the same copper(II)
centre, as was seen in the structure of 1c, but rather to a
neighbouring copper(II) centre occupying the vacant axial
Figure 6. ORTEP representation (50% thermal probability ellip-
soids) of the crystal structure of 2a
˚
position [N(4)ϪCu(2) ϭ 2.427(6) A] and thus completing
the distorted square-pyramidal coordination geometry
around the copper(II) centre. No solvent molecules were
found within the crystal lattice.
As shown in Figure 6, two of the pyridyl rings of L2 co-
ordinate to the copper(II) centre in 2a. The copper(II)
The two copper(II) chloride complexes of L1 included in centre is pentacoordinate, being coordinated by the pyridyl
our study, 1c and 1d, show the effect of solvent coordina- nitrogen atoms N(2) and N(3), the tertiary amine nitrogen
tion upon the nature of the final copper(II) complex ob- N(1), chloride ion Cl(1), and O(1) of the perchlorate anion.
tained. Crystals of 1c, the structure presented in Figure 4, The coordination environment around the copper(II) centre
were grown from a DMF-containing solution. In the crystal is best described as distorted square-pyramidal, with N(1),
structure, DMF was found to occupy the axial site of the N(2), N(3), and Cl(1) forming the basal plane
˚
˚
˚
distorted square-pyramidal coordination environment of [Cu(1)ϪN(2) ϭ 1.982(2) A, Cu(1)ϪN(3) ϭ 1.991(2) A,
Cu(1) and consequently of its symmetry-equivalent Cu(1)i Cu(1)ϪN(1) ϭ 2.073(2) A, Cu(1)ϪCl(1) ϭ 2.2265(7) A]
˚
as well.
and O(1) of the perchlorate anion occupying the axial posi-
˚
On moving to a medium containing predominantly ace- tion [Cu(1)ϪO(1) ϭ 2.4837(7) A]. The coordination of the
tonitrile, crystals of 1d were obtained, the structure of perchlorate anion in 2a is also evident from the IR spec-
which is shown in Figure 5. Here, the crystal structure re- trum recorded from a Nujol mull. The strong band at
116
2002, 111Ϫ121

Copper(II) Complexes of New Ligands
FULL PAPER
1089 cmϪ1 can be assigned as the coordinated perchlorate described as trigonal-bipyramidal distorted square-based
anion.
pyramidal (TBDSBP).
Ligand L2 is a derivative of the parent amine (dipica)
[dipica ϭ bis(2-pyridylmethyl)amine] and shows a similar
mode of coordination to copper(II) ions.[35Ϫ37] L2 differs in
that it possesses an additional pyridyl ring on the secondary
aliphatic amine nitrogen atom, increasing the potential for
additional coordination. There are numerous examples of
derivatives of dipica, and the resulting ligands and metal
complexes show interesting and novel properties.[38,39]
The structure of 2b is similar to that reported for a cop-
per complex of a derivatised dipica ligand.[38] This ligand
was prepared by converting the secondary amine functional
group of the precursor amine dipica into a tertiary amide
group. The coordination parameters around the copper(II)
centre are close to those seen in 2b. In the structure, the
tertiary amido nitrogen atom occupies the apical position
at the copper(II) centre, with the other four ligating atoms
(two pyridyl nitrogen atoms and two chloride ions) forming
a distorted square plane in a similar manner to that shown
in Figure 7. The coordination environment around the cop-
per(II) centre is best described as trigonal-bipyramidal dis-
torted square-based pyramidal (TBDSBP), having a tri-
gonality index τ of 0.30.
[Cu(L2)Cl2]·H2O (2b)
Green crystals suitable for single-crystal X-ray analysis
were grown by slow evaporation of the solvents from a solu-
tion in aqueous methanol. An ORTEP plot of the crystal
structure is displayed in Figure 7. Selected crystallographic
data and bond lengths and angles are listed in Table 1 and
2, respectively.
UV/Vis Spectroscopy
Figure 7. ORTEP representation (50% thermal probability ellips-
oids) of the crystal structure of 2b; a solvating water molecule has
been omitted for clarity
The copper(II) complexes of L2 are characterised by a
rather broad dϪd absorption band (ca. 650Ϫ1000 nm) in
As shown in Figure 7, and as was observed for 2a, only their solution (acetonitrile) electronic spectra; a low- or
two of the pyridyl rings of L2 coordinate to the copper(II) high-energy shoulder is often present as well, or occasion-
centre in 2b. The copper(II) centre is five-coordinate, being ally two distinct absorption maxima are observed. In many
ligated by the pyridyl nitrogen atoms N(2) and N(3), the cases, it has been demonstrated that the presence of a single
tertiary amine nitrogen N(1), and two chloride ions dϪd band with a low-energy shoulder is typical of a tri-
˚
˚
˚
˚
˚
[Cu(1)ϪN(2) ϭ 1.9798(17) A, Cu(1)ϪN(3) ϭ 1.9836(17) A, gonal-bipyramidal geometry at copper, whereas an absorp-
Cu(1)ϪCl(1) ϭ 2.2619(6) A, Cu(1)ϪCl(2) ϭ 2.3271(6) A, tion with a high-energy shoulder indicates a square-pyram-
Cu(1)ϪN(1) ϭ 2.3399(17) A]. At first sight, the geometry idal geometry. Examination of the electronic spectroscopic
around the copper(II) centre might appear to be distorted data of the copper(II) complexes of L2 (see Exp. Sect.) in-
trigonal bipyramidal, with the pyridyl nitrogen atoms N(2) dicates that, on the basis of this criterion, 2a adopts a
and N(3) occupying the axial positions and the two chloride square-pyramidal geometry, whereas 2b can best be de-
ions and N(1) occupying the equatorial plane. However, scribed as having a geometry around the copper(II) centre
closer inspection reveals that the coordination environment close to trigonal bipyramidal. Complexes of L1 are charac-
around the Cu(1) centre is nearer to that found in square- terised by a rather broad absorption band at around
pyramidal coordination complexes, with N(2), N(3), Cl(1), 650 nm, indicating a square-pyramidal geometry in solu-
and Cl(2) forming the basal plane and the apical position tion.
being occupied by N(1). This is substantiated by examining
the bond angles around the Cu(1) centre involving the
atoms Cl(1), Cl(2), and N(1) [122°, 99°, 139° (sum ϭ 360°)],
which deviate from the value of 120° expected for a regular
trigonal-bipyramidal geometry. Furthermore, the bond
Electrochemistry
The half-wave potentials of complexes 1a, 1d, 2a, and 2b
angle N(2)ϪCu(1)ϪN(3) ϭ 160.70(7)° is clearly less than were determined by cyclic voltammetry in acetonitrile; the
180°. This bond angle is a result of the small bite angles in results are summarised in Table 3. All compounds displayed
each of the two five-membered chelate rings involving a reversible cyclic voltammogram, demonstrating that stable
Cu(1), N(1), N(2), or N(3). These distortions and the value copper(I) complexes of the two ligands can be formed. Fig-
of the trigonality index τ of 0.36 (the index τ is zero for a ure 8 shows the cyclic voltammogram of 2b. Complexes
square pyramid and unity for a trigonal bipyramid)[34] sug- with L1 as a ligand are more easily reduced than those with
gest that the coordination environment around Cu(1) is best L2 as a ligand.
2002, 111Ϫ121
117

S. P. Foxon, O. Walter, S. Schindler
FULL PAPER
peroxo nor a peroxo intermediate was observable during the
reaction of [Cu(pmap)]ϩ with dioxygen. [Cu(tepa)]ϩ was
found not to react with dioxygen. It was thus concluded
that increasing the chelate ring size suppresses the forma-
tion of stable dioxygen adduct complexes in this series.
Unfortunately, reducing the chelate ring size by using L1
or L2 as described herein did not lead to a more stable
copper superoxo or peroxo complex because intramolecular
coordination of one of the pyridine donors was suppressed.
The reaction of the copper(I) complex of tpa with dioxygen
has been investigated previously and a cubane-like cluster
was obtained as a product.[33] The authors did not report
any dioxygen adduct complex as an intermediate during the
course of this reaction.
Table 3. Cyclic voltammetry of 1a, 1d, 2a, and 2b in acetonitrile
Compound[a]
(V)
(V)
(V)
1/2
∆
(mV)
red
ox
p
p
1a
1d
2a
2b
ϩ0.31
ϩ0.31
ϩ0.11
ϩ0.07
ϩ0.57
ϩ0.58
ϩ0.24
ϩ0.23
ϩ0.44
ϩ0.45
ϩ0.18
ϩ0.15
260
270
130
160
[a]
All potentials measured with a glassy carbon electrode vs. Ag/
AgCl using [NBu4]PF6 (0.1 ) as electrolyte; scan rate: 100 mV sϪ1
in MeCN [
red
ox
ϭ (
ϩ
ox)/2; ∆
ϭ
Ϫ
red].
p
1/2
p
p
p
Conclusions
We have reported the synthesis and characterisation of
two new ligands, L1 and L2, together with a series of cop-
per(II) complexes derived from these ligands. The crystal
structures of the complexes of L1 demonstrate that in each
case one of the three pyridyl donors remains uncoordin-
ated, as observed in the copper complexes of tpa. However,
the crystal structures of 1a and 1b show an important dif-
ference to copper tpa complexes: the coordination of meth-
anol molecules to the copper(II) centre of 1a and of water
molecules in 1b is stabilised by
hydrogen
Figure 8. Cyclic voltammogram of 2b in acetonitrile at 298 K; scan
rate ϭ 100 mV sϪ1; concentration of complex ϭ 1 m; concentra-
tion of the supporting electrolyte [NBu4]PF6 ϭ 0.1 
bonding between the coordinated solvent molecules and
each pendant pyridyl ‘‘arm’’. Furthermore, using chloride
as an anion in the syntheses of the copper(II) complexes of
L1 demonstrated an interesting solvent effect. In DMF, the
trinuclear complex 1c, incorporating coordinated DMF
molecules is obtained, thus preventing the formation of a
polymeric material. In contrast, in acetonitrile, no solvent
molecules are coordinated and a polymeric complex 1d is
formed instead.
Ligand L2 can be regarded as a derivative of bis(2-pyrid-
ylmethyl)amine (dipica) and the two complexes 2a and 2b
are related to the complexes with dipica as ligand. L2 differs
from dipica in that it possesses a third pyridyl ring (not
coordinated in 2a and 2b), increasing the potential for addi-
tional coordination.
As yet, it has not been possible to obtain copper(I) com-
plexes of ligands L1 or L2 in a solid form, but reactions
of dioxygen with these compounds formed in situ from a
copper(I) salt and the ligand have been investigated. In con-
trast to the reaction of dioxygen with the copper(I) complex
of tmpa, no dioxygen adducts could be observed as inter-
mediates. Instead, complexes of both ligands were slowly
oxidized to the copper(II) complexes, in line with their ra-
ther positive redox potentials.
Reactions of Dioxygen with Copper(I) Complexes of L1 and
L2
As yet, we have been unable to isolate solid copper(I)
complexes of L1 or L2; only yellow-orange oils have been
obtained. Therefore, to gain information on the reactions
of dioxygen with the copper(I) complexes of L1 or L2, these
compounds were prepared in situ by mixing stoichiometric
amounts of copper(I) salts with the ligands in acetone or
propionitrile. Reactions of these solutions with dioxygen
were investigated under the same conditions as employed
for [Cu(tmpa)(CH3CN)]ϩ and its derivatives, using low-
temperature stopped-flow techniques.[23] We observed that
the copper complexes of both ligands were slowly oxidised,
but in contrast to [Cu(tmpa)(CH3CN)]ϩ no ‘‘dioxygen ad-
ducts’’ were observed as intermediates.
Our earlier findings clearly demonstrated the influence of
chelate ring size on the stability (or inertness) of copper
‘‘dioxygen’’ complexes.[23] [Cu(tmpa)(CH3CN)]ϩ reacts very
rapidly with dioxygen to first form a superoxo complex,
which reacts further to form a peroxo complex that is stable
at low temperatures. Only one chelate ring is enlarged in
[Cu(pmea)]ϩ, but we found that no superoxo complex could
be detected in the course of its reaction with dioxygen; the
initially formed peroxo complex rapidly underwent further
reactions. In contrast to the findings for [Cu(pmea)]ϩ, a
Experimental Section
General Remarks: Reagents and solvents used were of commercially
stopped-flow kinetic investigation showed that neither a su- available reagent quality. Acetonitrile, propionitrile, diethyl ether,
118 2002, 111Ϫ121

Copper(II) Complexes of New Ligands
FULL PAPER
and acetone were dried by standard methods. [Cu(CH3CN)4]ClO4
N,N-(2-Pyridyl)(2-pyridylmethyl)amine: A solution of 2-pyridine-
and [Cu(CH3CN)4]PF6 were synthesized according to literature carboxaldehyde (9.2 mL, 96 mmol) and 2-aminopyridine (7.5 g,
procedures.[40] The purities of the ligands were assessed by TLC,
80 mmol) in benzene (150 mL) was refluxed for 18 h with the con-
elemental analysis, and 1H and 13C NMR. UV/Vis spectra were tinuous removal of water by means of a DeanϪStark trap. The
measured on a HewlettϪPackard 8452 A spectrophotometer using
solvent was subsequently removed in vacuo and the residue was
taken up in absolute ethanol (200 mL). To this yellow solution,
NaBH4 (4.0 g, 105.8 mmol) was added and the solution was stirred
1
standard 1 cm quartz cuvettes. H and 13C NMR spectra were re-
corded on a Bruker DXP 300 AVANCE spectrometer. Infrared
spectra were recorded from samples in either Nujol mulls or KBr at room temperature for 18 h. The excess NaBH4 was then cau-
pellets on an ATJ Mattson Infinity 60 AR FT-IR instrument. Cyc-
lic voltammetry was performed using an EG&G Model 263 po-
tiously quenched by adding first water (100 mL) and then saturated
aqueous NH4Cl solution (100 mL) at 70 °C. Thereafter, the volat-
tentiostat at 25 °C at a scan rate of 100 mV sϪ1. The solutions iles were removed in vacuo and the residue was redissolved in water
under investigation contained 1 m copper complex and 0.1 
[NBu4]PF6 in acetonitrile that had been deoxygenated by bubbling acetate (3 ϫ 150 mL) and the combined organic fractions were
nitrogen through it. A conventional H-type cell was used, with dried over anhydrous magnesium sulfate. Upon removal of the
glassy carbon, Pt, and Ag/AgCl as working, counter, and reference solvent, a viscous yellow oil was obtained. The product was puri-
(200 mL). The resulting aqueous solution was extracted with ethyl
electrodes, respectively.
fied by vacuum distillation to yield a pale-yellow viscous liquid
(6.0 g, 41%, 32.4 mmol). FDI-MS:
(CDCl3, 300 MHz): δ ϭ 4.65 (d, 2 H, ϪCH2Ϫ,
/
ϭ 185 [Mϩ]. 1H NMR
3
Variable-Temperature Stopped-Flow Measurements: Solutions of
the complexes for the collection of time-resolved UV/Vis spectra
were prepared in a glovebox and transferred to the low-temperature
stopped-flow instrument by means of syringes. Dioxygen-saturated
solutions were prepared by bubbling dioxygen through propionitr-
ile or acetone in syringes (solubility of dioxygen in propionitrile at
25 °C is 0.0088 ,[20] while in acetone it is 0.0102 [41]). The reac-
tions were studied under pseudo-first-order conditions ([complex]
Ͻ [O2]), and time-resolved UV/Vis spectra of the reactions of di-
oxygen with copper(I) complexes were recorded with a modified
Hi-Tech SF-3 L low-temperature stopped-flow unit (Salisbury,
U.K.) equipped with a J&M TIDAS 16Ϫ500 photodiode-array
spectrophotometer (J&M, Aalen, Germany).
ϭ 5.3 Hz),
H,H
5.86 (br, 1 H, NH), 6.43Ϫ6.45 (m, 1 H, ArH), 6.53Ϫ6.58 (m, 1 H,
ArH), 7.13Ϫ7.17 (m, 1 H, ArH), 7.30Ϫ7.40 (m, 2 H, ArH),
7.58Ϫ7.63 (m, 1 H, ArH), 8.09Ϫ8.11 (m, 1 H, ArH), 8.54Ϫ8.55
(m, 1 H, ArH). 13C NMR (CDCl3, 75 MHz): δ ϭ 47.2, 107.7,
112.9, 121.6, 122.0, 136.6, 137.3, 147.9, 149.0, 158.3, 158.5. IR
˜
(KBr): ν ϭ 3278 (br, m), 3084 (m), 3056 (m), 3018 (m), 2927 (w),
2865 (w), 1603 (s), 1571 (s), 1506 (s), 1490 (s), 1438 (m), 1332 (m),
1293 (m), 1254 (w), 1151 (m), 1120 (w), 1084 (w), 1049 (w), 983
(m), 771 (m), 686 (m), 611 (m), 527 cmϪ1 (m).
N-[Bis(2-pyridyl)methyl]-2-pyridylamine (L2): Sodium hydride (60%
dispersion in mineral oil; 1.3 g, 32.5 mmol) was added to anhydrous
DMF (100 mL) under nitrogen. The resulting grey slurry was
stirred at room temperature until hydrogen evolution had ceased
Syntheses of Ligands and Complexes
(ca. 0.5 h). A solution of
-(2-pyridyl)(2-pyridylmethyl)amine
Caution! Perchlorate salts are potentially explosive and should be
handled with great care.
(5.0 g, 27 mmol) in anhydrous DMF (60 mL) was then added drop-
wise to the sodium hydride slurry. The resulting orange solution
was stirred until hydrogen evolution had ceased (ca. 1 h). To the
N-[(2-Pyridyl)methyl]-2,2Ј-dipyridylamine (L1): Powdered potas-
sium hydroxide (5.2 g, 93 mmol) was added to DMSO (40 mL). amine carbanion, a solution of 2-picolyl chloride (free base)
2,2Ј-Dipyridylamine (3.42 g, 20 mmol) was added to this mixture.
The resulting deep-orange coloured solution was stirred at room
(3.79 g, 30 mmol) in anhydrous DMF (50 mL) was added dropwise
and the brown solution was stirred overnight at room temperature.
temperature for 45 min. 2-Picolyl chloride hydrochloride (3.28 g, The light-orange solution obtained was then cautiously quenched
20 mmol) was then added and the orange solution was stirred at by the addition of water (200 mL), and brine (50 mL) was also
room temperature for 1 h. It was then diluted with water (50 mL), added. The aqueous solution was exhaustively extracted with
which led to the immediate deposition of a fine yellow precipitate. dichloromethane (4 ϫ 150 mL). The combined organic phases were
This precipitate was collected by filtration, washed with water (3
ϫ 30 mL), and the yellow solid was recrystallised from hexane
washed with brine (200 mL) and dried over anhydrous magnesium
sulfate. Removal of the solvent in vacuo yielded the crude product
(75 mL) containing the minimum volume of dichloromethane. On as a light-tan coloured solid. It was taken up in warm diethyl ether
cooling to 0 °C, fine yellow crystals formed. These were collected (100 mL), which led to the separation of a brown oil. The ethereal
by filtration, washed with a little cold hexane, and dried to yield
L1 as a pale-yellow solid (2.9 g, 55%, 11 mmol). C16H14N4: calcd.
solution was decanted and the solvent was removed in vacuo. The
crude cream-coloured product was recrystallised once from diethyl
C 73.26, H 5.38, N 21.36; found C 73.31, H 5.50, N 21.23. M.p. ether. On cooling to 0 °C, a fine white precipitate appeared, which
106Ϫ108 °C. FDI-MS:
/
ϭ 262 [Mϩ]. 1H NMR (CDCl3, was collected by filtration and dried in vacuo (5.3 g, 70%,
300 MHz): δ ϭ 5.60 (s, 2 H, ϪCH2Ϫ), 6.82Ϫ6.86 (m, 2 H, ArH), 19.2 mmol). C17H16N4: calcd. C 73.89, H 5.84, N 20.27; found C
7.05Ϫ7.09 (m, 1 H, ArH), 7.24Ϫ7.32 (m, 3 H, ArH), 7.48Ϫ7.55 73.94, H 5.97, N 20.03. M.p. 92Ϫ94 °C. FDI-MS: / ϭ 276 [Mϩ].
(m, 3 H, ArH), 8.28Ϫ8.30 (m, 2 H, ArH), 8.52 (d, 1 H, ArH). 13C 1H NMR (CDCl3, 300 MHz): δ ϭ 4.99 (s, 4 H, ϪCH2Ϫ),
NMR (CDCl3, 75 MHz): δ ϭ 53.6, 114.4, 117.3, 121.2, 121.6,
136.5, 137.3, 148.2, 149.0, 156.8, 159.5. IR (KBr): ν˜ ϭ 3059 (w),
6.47Ϫ6.61 (m, 2 H, ArH), 7.11Ϫ7.15 (m, 2 H, ArH), 7.22Ϫ7.25
(m, 2 H, ArH), 7.34Ϫ7.40 (m, 1 H, ArH), 7.55Ϫ7.60 (m, 2 H,
3004 (w), 2961 (w), 2925 (w), 2362 (w), 2337 (w), 1967 (w), 1943 ArH), 8.18 (d, 1 H, ArH), 8.54 (d, 2 H, ArH). 13C NMR (CDCl3,
(w), 1915 (w), 1893 (w), 1874 (w), 1845 (w), 1829 (w), 1796 (w), 75 MHz): δ ϭ 54.1, 106.1, 112.7, 121.1, 122.0, 136.6, 137.5, 148.0,
1778 (w), 1737 (w), 1717 (w), 1701 (w), 1651 (w), 1585 (s), 1564 149.4, 158.1, 158.7. IR (KBr): ν˜ ϭ 3046 (w), 3006 (w), 2964 (w),
(m), 1470 (s), 1427 (s), 1379 (m), 1349 (m), 1325 (m), 1281 (m), 2924 (w), 2924 (w), 2362 (w), 2338 (w), 1965 (w), 1916 (w), 1867
1260 (m), 1245 (m), 1225 (m), 1209 (m), 1173 (w), 1149 (m), 1130 (w), 1843 (w), 1831 (w), 1768 (w), 1736 (w), 1719 (w), 1701 (w),
(w), 1088 (m), 1044 (w), 983 (w), 901 (w), 873 (w), 772 (m), 753
1596 (m), 1564 (m), 1492 (m), 1434 (m), 1391 (w), 1351 (m), 1283
(w), 1241 (w), 1180 (w), 1152 (w), 1094 (w), 1069 (w), 1047 (w),
(m), 737 (m), 661 (w), 612 (w), 585 cmϪ1 (w).
2002, 111Ϫ121
119

S. P. Foxon, O. Walter, S. Schindler
FULL PAPER
976 (w), 938 (w), 884 (w), 848 (w), 779 (w), 753 (m), 664 (w), 635 diffractometer using graphite-monochromated Mo-
˚
radiation
α
(w), 615 (w), 589 (w), 568 (w), 545 cmϪ1 (w).
(λ ϭ 0.71073 A). Exposure times were 10 s per frame for L1, 1a,
1b, and 1c and 20 s per frame for 1d, 2a, and 2b, collected using
the ω-scan technique (∆ω ϭ 0.45° for L1, 1a, 1b, and 1c and 0.4°
for 1d, 2a, and 2b). The collected reflections were corrected for
Lorentz, polarization, and absorption effects. The structures were
[Cu(L1)2(CH3OH)2](ClO4)2 (1a): To a solution of L1 (0.1 g,
0.38 mmol) in methanol (3 mL) was added
a solution of
Cu(ClO4)2·6H2O (0.071 g, 0.19 mmol) in methanol (3 mL). Diethyl
ether (100 mL) was then added, which led to the deposition of a
fine blue precipitate. The mixture was stirred for a few minutes and
then filtered. Dark-blue block-shaped crystals suitable for X-ray
analysis were grown by slow evaporation of the solvents from a
solution in aqueous methanol.
solved by direct methods and refined by full-matrix least-squares
2 [42Ϫ44]
methods on
.
Crystallographic data (excluding structure factors) for the struc-
tures reported in this paper have been deposited with the Cam-
bridge Crystallographic Data Centre as supplementary publication
nos. CCDC-167124Ϫ167130. Copies of the data can be obtained
free of charge on application to the CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, U.K. [Fax: (internat.) ϩ44 (0)1223 336033;
E-mail: deposit@ccdc.cam.ac.uk].
[Cu(L1)2(H2O)2](ClO4)2·2DMF (1b): To a solution of L1 (0.1 g,
0.38 mmol) in methanol (3 mL) was added
a solution of
Cu(ClO4)2·6H2O (0.071 g, 0.19 mmol) in methanol (3 mL). Diethyl
ether (100 mL) was then added, which led to the deposition of a
fine blue precipitate. The mixture was stirred for a few minutes and
then filtered. The precipitate was collected by filtration to give the
crude product as a light-blue solid (0.135 g, 86%). Dark-blue block-
shaped crystals suitable for X-ray analysis were grown by vapour
diffusion of diethyl ether into a solution in DMF. C32H32N8Cu-
Cl2O10: calcd. C 46.70, H 3.92, N 13.61; found C 46.49, H 3.83, N
13.36. UV/Vis [CH3CN; λmax, nm (ε, Ϫ1 cmϪ1)]: 210 (8970), 250
(8847), 294 (8048), 410 (109), 656 (79).
Acknowledgments
The authors gratefully acknowledge financial support from the
DFG (S. Schindler) and the DAAD (S. P. Foxon), and Prof. Rudi
van Eldik (University of Erlangen-Nürnberg) for his support of
this work.
[Cu3(L1)2(DMF)2Cl6] (1c): Ligand L1 (0.10 g, 0.38 mmol) in DMF
and CuCl2·2H2O (0.065 g, 0.38 mmol) in DMF (2 mL) were com-
bined. Diethyl ether was then slowly allowed to diffuse into the
resulting solution of 1c. After a few days, blue/green block-shaped
crystals of 1c were formed.
[1]
K. D. Karlin, A. D. Zuberbühler, in
Edition (Eds.: J. Reedijk, E. Bouwman), Marcel Dekker, New
York, 1999, pp. 469Ϫ534.
S. Fox, K. D. Karlin, in
S. Valentine, C. S. Foote, A. Greenberg, J. F. Liebman), Blackie
Academic and Professional, Chapman & Hall, Glasgow, 1995,
pp. 188Ϫ231.
, 2nd
[2]
(Eds.: J.
[Cu(L1)Cl2] (1d): To a solution of L1 (0.1 g, 0.38 mmol) in aceton-
itrile (3 mL) was added a solution of CuCl2·2H2O (0.066 g,
0.38 mmol) in methanol (5 mL). The mixture was stirred for a few
minutes and then filtered. Crystals suitable for X-ray analysis
formed soon thereafter (0.65 g, 50%).
[3]
W. Kaim, J. Rall,
1996,
1996, , 43Ϫ60.
1992, , 1Ϫ77.
1994, , 737Ϫ757.
, 47Ϫ64;
[4]
[5]
[6]
N. Kitajima,
N. Kitajima, Y. Moro-oka,
K. D. Karlin, Z. Tyeklar (Eds.),
, Chapman & Hall, New York, 1993.
´
[Cu(L2)Cl]ClO4 (2a): To a solution of L2 (0.1 g, 0.36 mmol) in
methanol (10 mL) was added a solution of Cu(ClO4)2·6H2O
(0.067 g, 0.18 mmol) and CuCl2·2H2O (0.036 g, 0.18 mmol) in
methanol (5 mL). The mixture was stirred for a few minutes and
then filtered. Diethyl ether (100 mL) was quickly added to the fil-
trate, which led to the deposition of a sky-blue precipitate. This
precipitate was collected by filtration and dried in vacuo to yield a
light-green solid (0.16 g, 90%, 0.33 mmol). Crystals suitable for X-
ray analysis were grown by vapour diffusion of diethyl ether into a
solution in DMF. C17H16N4CuCl2O4: calcd. C 43.01, H 3.82, N
11.80; found C 43.04, H 3.43, N 11.64. UV/Vis [CH3CN, (ε, Ϫ1
cmϪ1)]: λmax ϭ 214 (14372), 260 (20809), 366 (417), 708 nm (125).
[7]
[8]
E. I. Solomon, U. M. Sundaram, T. E. Machonkin,
1996, , 2563Ϫ2605.
K. A. Magnus, H. Ton-That, J. E. Carpenter,
, 727Ϫ735.
1994,
[9]
M. E. Cuff, K. I. Miller, K. E. van Holde, W. A. Hendrickson,
, 855Ϫ870.
1998,
[10]
H. Decker, R. Dillinger, F. Tuczek,
2000,
, 1591Ϫ1595.
J. P. Klinman,
E. Spodine, J. Manzur,
H.-C. Liang, M. Dahan, K. D. Karlin,
[11]
[12]
[13]
1996, , 2541Ϫ2561.
1992,
, 171Ϫ198.
1999,
, 168Ϫ175.
K. D. Karlin,
A. G. Blackman, W. B. Tolman, in
[14]
[15]
1993,
, 701Ϫ708.
[Cu(L2)Cl2] (2b): To a solution of L2 (0.1 g, 0.36 mmol) in meth-
anol (10 mL) was added a solution of CuCl2·2H2O (0.062 g,
0.36 mmol) in methanol (5 mL). The mixture was stirred for a few
minutes and then filtered. Diethyl ether (100 mL) was quickly ad-
ded to the filtrate, which led to the deposition of a green precipitate.
This precipitate was collected by filtration and dried in vacuo to
yield a light-green solid (0.13 g, 86%, 0.31 mmol). Crystals suitable
for X-ray analysis were grown from methanol/water (2:1; 10 mL).
C17H16N4CuCl2: calcd. C 49.71, H 4.42, N 13.64; found C 49.87,
H 4.15, N 13.50. UV/Vis [CH3CN (ε, Ϫ1 cmϪ1)]: λmax ϭ 212
(12735), 228 (11593), 260 (12801), 800 nm (320).
(Ed.: B.
Meunier), Springer, Berlin, 2000, vol. 97, pp. 179Ϫ211.
[16]
[17]
S. Schindler,
R. R. Jacobson, Z. Tyeklar, A. Farooq, K. D. Karlin, S. Liu,
J. Zubieta, 1988, , 3690Ϫ3692.
Z. Tyeklar, R. R. Jakobson, N. Wei, N. N. Murthy, J. Zubieta,
K. D. Karlin, 1993, , 2677Ϫ2689.
M. J. Baldwin, P. K. Ross, J. E. Pate, Z. Tyeklar, K. D. Karlin,
E. I. Solomon, 1991, , 8671Ϫ8679.
K. D. Karlin, N. Wei, B. Jung, S. Kaderli, P. Niklaus, A. D.
Zuberbühler, 1993, , 9506Ϫ9514.
2000, 2311Ϫ2326.
´
[18]
[19]
[20]
[21]
[22]
[23]
´
´
K. D. Karlin, S. Kaderli, A. D. Zuberbühler,
1997, , 139Ϫ147.
K. D. Karlin, D.-H. Lee, S. Kaderli, A. D. Zuberbühler,
1997, 475Ϫ476.
M. Schatz, M. Becker, F. Thaler, F. Hampel, S. Schindler, R.
X-ray Crystallographic Study: Crystal data and experimental condi-
tions are listed in Table 1. Selected bond lengths and bond angles
with standard deviations in parentheses are presented in Table 2.
Intensity data were collected on a Siemens SMART 1000 CCD
120
2002, 111Ϫ121

Copper(II) Complexes of New Ligands
FULL PAPER
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
´
R. Jacobsen, Z. Tyeklar, N. N. Murthy, P. Ghosh, Q. Chen, J.
A. W. Addison, T. N. Rao, J. Reedijk, J. van Rijn, G. C. Ver-
Zubieta, K. D. Karlin,
2001, , 2312Ϫ2322.
schoor,
H. J. Hoorn, P. de Joode, W. L. Driessen, J. Reedijk,
1996, , 191Ϫ197.
1984, 1349Ϫ1356.
[24]
J. P. Wibaut, G. L. La Bastide,
1933, , 493Ϫ498.
W. Yang, L. Chen, S. Wang,
W. Yang, H. Schmider, Q. Wu, Y. Zhang, S. Wang,
2000, , 2397Ϫ2404.
C. J. Boxwell, P. H. Walton,
[25]
[26]
2001, , 507Ϫ515.
M. Palaniandavar, R. J. Butcher, A. W. Addison,
1996, , 467Ϫ471.
M. Palaniandavar, S. Mahadevan, M. Köckerling, G. Henkel,
2000, 1151Ϫ1154.
C. Cox, D. Ferraris, N. N. Murthy, T. Lectka,
[27]
[28]
1999, 1647Ϫ1648.
J. M. Rowland, M. M. Olmstead, P. K. Mascharak,
2000, , 5326Ϫ5332.
1996,
, 5332Ϫ5333.
[29]
F. H. Allen, J. E. Davies, J. J. Galloy, O. Johnson, O. Kennard,
C. F. Macrae, E. M. Mitchell, G. F. Mitchell, D. G. Watson,
1991, , 187Ϫ204.
N. Niklas, O. Walter, R. Alsfasser,
1723Ϫ1731.
2000,
1979,
G. J. Kubas, B. Monzyk, A. L. Crumbliss,
, 90Ϫ92.
[30]
[31]
[32]
[33]
P. A. Anderson, F. R. Keene, J. M. Gulbis, E. R. T. Tiekink,
1993,
, 275Ϫ278.
D. Boys, C. Escobar, W. Zamudio,
1992, , 1118Ϫ1120.
P. L. Dedert, J. S. Thompson, J. A. Ibers, T. M. Marks,
1982, , 969Ϫ977.
P. L. Dedert, T. Sorrell, J. A. Ibers, T. M. Marks,
1982, , 3506Ϫ3517.
P. Lühring, A. Schumpe,
250Ϫ252.
1989,
,
[42]
[43]
[44]
G. M. Sheldrick,
L. Zsolnai,
, Universität Göttingen, 1997.
, Universität Heidelberg, 1997.
Received July 24, 2001
[I01276]
2002, 111Ϫ121
121