Oligo-m-phenyleneoxalamide copper(II) Mesocates as electro-switchable ferromagnetic metalorganic wires

DOI: 10.1002/chem.201001737

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Chemistry - A European Journal p. 12838 - 12851 (2010)

Update date:2022-08-04

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Authors:

Pardo, Emilio

Ferrando-Soria, Jess

Dul, Marie-Claire

Lescouezec, Rodrigue

Journaux, Yves

Ruiz-Garcia, Rafael

Cano, Joan

Julve, Miguel

Lloret, Francesc

Canadillas-Delgado, Laura

Pasan, Jorge

Ruiz-Perez, Catalina

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Article abstract of DOI:10.1002/chem.201001737

Double-stranded copper(II) string complexes of varying nuclearity, from di- to tetranuclear species, have been prepared by the Cu^II-mediated self-assembly of a novel family of linear homo- and heteropolytopic ligands that contain two outer oxam

Full text of DOI:10.1002/chem.201001737

DOI: 10.1002/chem.201001737

Oligo-m-phenyleneoxalamide Copper(II) Mesocates as Electro-Switchable

Ferromagnetic Metal–Organic Wires

Emilio Pardo,^{[a, c]}Jesﬄs Ferrando-Soria,^[c]Marie-Claire Dul,^{[a, f]}Rodrigue Lescouzec,^[a]

Yves Journaux,*^{[a, b]}Rafael Ruiz-García,^{[c, d]}Joan Cano,^{[c, d]}Miguel Julve,^[c]

Francesc Lloret,*^[c]Laura CaÇadillas-Delgado,^{[e, g, h]}Jorge Pasµn,^[e]and

Catalina Ruiz-PØrez^[e]

Abstract: Double-stranded copper(II)

string complexes of varying nuclearity,

from di- to tetranuclear species, have

been prepared by the Cu^II-mediated

for 1d–3d. Variable-temperature (2.0–

300 K) magnetic susceptibility and vari-

along the linear metal array with over-

all intermetallic distances between ter-

minal metal centers in the range of

0.7–2.2 nm. Cyclic voltammetry (CV)

and rotating-disk electrode (RDE)

electrochemical measurements for 1d–

3d show several reversible or quasire-

versible one- or two-electron steps that

involve the consecutive metal-centered

oxidation of the inner and outer Cu^II

able-field

(0–5.0 T)

magnetization

measurements for 1d–3d show the oc-

currence of S=nS_Cu(n=2–4) high-spin

ground states that arise from the mod-

erate ferromagnetic coupling between

the unpaired electrons of the linearly

self-assembly of

a novel family of

linear homo- and heteropolytopic li-

gands that contain two outer oxamato

and either zero (1b), one (2b), or two

(3b) inner oxamidato donor groups

separated by rigid 2-methyl-1,3-phenyl-

ene spacers. The X-ray crystal struc-

disposed Cu^IIions (S_Cu=¹= ) through

the two anti m-phenylenediamidate-

type bridges (J values in the range of

+15.0 to 16.8 cm^ꢀ1). Density functional

theory (DFT) calculations for 1d–3d

evidence a sign alternation of the spin

density in the meta-substituted phenyl-

ene spacers in agreement with a spin

ions (S_Cu=¹= ) to diamagnetic Cu^III

tures of these Cu^IIcomplexes (n=2

ones (S_Cu=0) at relatively low formal

potentials (E values in the range of

+0.14 to 0.25 V and of +0.43 to 0.67 V

vs. SCE, respectively). Further devel-

opments may be envisaged for this

family of oligo-m-phenyleneoxalamide

copper(II) double mesocates as electro-

switchable ferromagnetic ꢀmetal–organ-

ic wiresꢁ (MOWs) on the basis of their

unique ferromagnetic and multicenter

redox behaviors.

(1d), 3 (2d), and 4 (3d)) show a linear

array of metal atoms with an overall

twisted coordination geometry for both

the outer CuN₂O₂and inner CuN₄

chromophores. Two such nonplanar all-

syn bridging ligands 1b–3b in an anti

arrangement clamp around the metal

centers with alternating M and P heli-

cal chiralities to afford an overall

double meso-helicate-type architecture

polarization

exchange

mechanism

Keywords: copper · density func-

tional calculations · magnetic prop-

erties · mesocates · redox properties

[a] Dr. E. Pardo, Dr. M.-C. Dul, Dr. R. Lescouꢂzec, Dr. Y. Journaux

Institut Parisien de Chimie Molꢃculaire

UPMC Univ Paris 06, Paris, 75252 (France)

Fax : (+33)144273841

[e] Dr. L. CaÇadillas-Delgado, Dr. J. Pasꢈn, Prof. Dr. C. Ruiz-Pꢃrez

Laboratorio de Rayos X y Materiales Moleculares

Departamento de Fꢄsica Fundamental II, Facultad de Fꢄsica

Universidad de la Laguna, La Laguna, Tenerife, 38201 (Spain)

E-mail: jour@ccr.jussieu.fr

[f] Dr. M.-C. Dul

[b] Dr. Y. Journaux

Department of Chemistry, Memorial University

St. Johnꢁs, Newfoundland, A1B 3X7 (Canada)

CNRS, UMR 7201, Paris, 75005 (France)

[c] Dr. E. Pardo, J. Ferrando-Soria, Dr. R. Ruiz-Garcꢄa, Dr. J. Cano,

Prof. Dr. M. Julve, Prof. Dr. F. Lloret

[g] Dr. L. CaÇadillas-Delgado

Instituto de Ciencia de Materiales de Aragꢇn

CSIC-Universidad de Zaragoza, Zaragoza, 50009 (Spain)

Departament de Quꢄmica Inorgꢅnica/

Instituto de Ciencia Molecular (ICMol)

Universitat de Valꢆncia, Paterna, Valencia, 46980 (Spain)

Fax : (+34)963-544-322

[h] Dr. L. CaÇadillas-Delgado

Institut Laue Langevin, Grenoble, 38042 (France)

Supporting information for this article is available on the WWW

under http://dx.doi.org/10.1002/chem.201001737.

E-mail: francisco.lloret@uv.es

[d] Dr. R. Ruiz-Garcꢄa, Dr. J. Cano

Fundaciꢇ General de la Universitat de Valꢆncia (FGUV)

Universitat de Valꢆncia, Valencia, 46002 (Spain)

12838

ꢉ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 2010, 16, 12838 – 12851

FULL PAPER

Introduction

Similar studies on the EE properties between distant

metal centers through extended organic bridges in oligonu-

clear transition-metal helicates and mesocates beyond dinu-

clear species are relatively scarce.^[22]For example, a tetra-

copper(II) triple helicate with a bis(a-pyridylazine)pyrida-

zine ligand and a hexacopper(II) double helicate with an

oligo-a-pyridylcarboxamido ligand have been reported by

the groups of Matthews and Huc, respectively.^[22]However,

the magnetic behavior (whenever reported) of these oligo-

nuclear helicates with a string of four and six Cu^IIions is

that of the isolated spins, with negligible or very weak anti-

ferromagnetic interactions between the metal centers

through the organic bridging ligands.^[22a]

Supramolecular coordination chemistry has been an out-

standing area of research in the field of supramolecular

chemistry,^[1]which has set up the guiding principles for the

self-assembly of well-defined multimetallic coordination ar-

chitectures of increasing structural complexity based on

metal–ligand interactions.^[2]The focus of the current re-

search in supramolecular coordination chemistry (so-called

metallosupramolecular chemistry) moves toward the intro-

duction of functionality into these polymetallic systems.^[3–9]

The main reason for the interest in these nanosized, self-as-

sembling functional metallosupramolecular complexes is the

very unusual electronic (magnetic and redox) properties

that they can exhibit, which could be exploited in the relat-

ed fields of molecular magnetism and electronics.^[10]

Linear multiple-stranded polynuclear helicates and relat-

ed meso-helicates, so-called mesocates, were the object of

much attention as model systems for the study of metal-di-

rected self-assembling processes.^[11]Since the seminal re-

search on double-stranded di- and trinuclear helicates with

oligobipyridine ligands and tetrahedral Cu^Iions by Lehn

et al.,^[12]much work has been devoted to the search for the

structure and function of helicates and mesocates.^[13,14]Al-

though their redox behavior has attracted great interest,^[13]it

was not until recently that several groups have focused on

the magnetic properties of helicates and mesocates.^[14]Be-

sides their actual interest as models for the fundamental re-

search on electron-exchange (EE) and electron-transfer

(ET) phenomena, homo- and heterovalent exchange-cou-

pled helicates and mesocates will be of great importance in

the “bottom-up” approach to molecular-level spintronic de-

vices. Molecular wires and molecular switches are two repre-

sentative examples of the potential applications of such a

class of ligand-supported, linear metallosupramolecular

complexes in information storage and processing nanotech-

nology.^[15]

In our research on ligand design as a means to control the

molecular and electronic structure of oxalamide-based tran-

sition-metal complexes,^[23–25]we report a new double-strand-

ed dicopper(II) complex of the meso-helicate-type that re-

sults from the side-by-side self-assembly of two N,N’-1,3-

phenylenebisACTHNUTRGNEUNG

(oxamate) bridging ligands by two Cu^IIions.^[25a]

Ligand design is crucial in the pursuit of functional heli-

cates and mesocates, both to organize the paramagnetic

metal ions in the desired linear topology and to efficiently

transmit the electronic interactions between the metal

ions—either directly, through metal–metal bonds, or indi-

rectly, through the organic bridging ligands. This basic prin-

ciple is illustrated by the impressive work carried out by the

groups of Cotton and Peng on the redox and magnetic prop-

erties of self-assembled transition-metal complexes of vary-

ing nuclearities that extend from tri- to nonanuclear species,

with linear oligo-a-pyridylamine and related pyrazine-, pyri-

midine-, and naphthyridine-modified ligands.^[16–21]This series

of moderately strong, antiferromagnetically coupled quadru-

ple mesocates with a string of three to nine shortly spaced

M^IIions (M=Cu, Ni, Co, Cr, Pd, Pt, Ru, and Rh) have at-

tracted considerable attention for fundamental research on

the effect of metal–metal bonding interactions on ET prop-

erties, because they will probably allow them to function as

molecular electronic wires and switches.^[15]

Notably, this dinuclear double mesocate is among the first

transition-metal complexes for which the ferromagnetic cou-

pling between the two metal ions is due to spin polarization

effects that arise from the alternation of the spin density at

the double meta-phenylenediamidate bridge within the re-

sulting metallacyclophane core, as evidenced by density

functional theory (DFT) calculations.^[25a]Through a sequen-

tial addition of oxamidato binding sites to this parent homo-

topic dioxamato ligand, it would be possible to prepare

higher-nuclearity copper(II) analogues with a linear topolo-

gy that exhibit ferromagnetic coupling between the metal

centers as well as metal-centered redox activity because of

the well-known strong donor ability (basicity) of the oxami-

dato donor groups.^[23a,d,e]They therefore constitute a new

class of molecular magnetic wires and switches for the trans-

mission of ꢀthrough-bondꢁ metal–metal EE interactions, by

analogy with the aforementioned molecular electronic wires

and switches that were based on direct ꢀthrough-spaceꢁ

metal–metal ET interactions.^[25b–d]In contrast to convention-

al molecular electronic wires and switches, these molecular

Chem. Eur. J. 2010, 16, 12838 – 12851

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12839

F. Lloret, Y. Journaux et al.

magnetic wires and switches may offer a new design concept

for the transfer of information over long distances based on

purely EE (Coulomb) interactions and with no current flow.

We report here the syntheses, crystal structures, redox,

and magnetic properties of this novel series of double-

stranded copper(II) complexes of the general formula

[Cu^II_nL₂]^2nꢀ(n=2–4), in which L is the 2-methyl-substituted

The anionic oligonuclear copper(II) complexes [Cu_nL₂]^2nꢀ

(n=2–4) were isolated as either the alkaline or tetra(aryl/

alkyl) ammonium and phosphonium salts of formula Na₄-

[Cu

[Cu₄-

(1d),

[Cu₄-

AHCTUNGTRENNUNG

derivative of the N,N’-1,3-phenylenebisACTHNUGRTENUNG(oxamate) ligand

(L=1b) and its corresponding longer heterotopic analogues

with one (L=2b) and two (L=3b) additional oxamidato

binding sites, respectively. DFT calculations on this unique

family of oligonuclear double mesocates with linear oligo-

m-phenyleneoxalamide ligands, which extends from di- to

tetranuclear species, were also performed to support the oc-

currence of a spin polarization mechanism for the propaga-

tion of an EE interaction of a ferromagnetic nature between

the metal centers through the methyl-substituted meta-phen-

ylene spacers.

copper(II) nitrate in the appropriate 2:n molar ratio by

using either sodium(I) hydroxide or hydride as base in

water or dimethylformamide, respectively (Scheme 2a and

b). The former method was employed for the shorter ligands

(L=1b and 2b) with rather good results, whereas the latter

method was used for the longest one (L=3b) because of

ligand insolubility and/or deprotonation problems. Complex

1d was similarly synthesized by the one-step reaction of the

corresponding proACHTNUGTRNNEUGliACHTUNTGRENNUGgand H₂Et₂1b with copper(II) chloride

in the appropriate 2:2 molar ratio by using tetra-n-butylam-

monium hydroxide as base in water followed by extraction

with dichloromethane (Scheme 2c). Alternatively, complexes

2d and 3d were synthesized by two successive steps after

metathesis of the corresponding sodium(I) salts 2c and 3c

with ethyltriphenylphosphonium bromide in water/acetoni-

trile through the intermediacy of the silver(I) salts

(Scheme 2d and e). The inorganic salts (1c–3c) were soluble

in water, whereas the organic ones (1d–3d) were sparingly

soluble in organic solvents like acetonitrile.

Results and Discussion

Syntheses of the ligands and complexes: The ligands were

synthesized from the straightforward condensation of the

corresponding diamine precursors H_2nꢀ41a–H_2nꢀ43a (n=2–4)

with ethyl oxalyl chloride ester (1:2 ratio) in tetrahydrofuran

in the presence of triethylamine, and they were isolated as

the diethyl ester acid derivatives H_2nꢀ2Et₂L (L=1b–3b; n=

2–4) in pure form and very good yields (90–97%)

(Scheme 1a, c, and e). The parent 2-methyl-1,3-phenylenedi-

amine (1a) was commercially available, whereas the two

other diamine precursors, namely, N,N’-bis(2-methyl-3-phe-

nylamine)oxamide (H₂2a) and 2-methyl-1,3-phenylenebis-

The chemical identity of the ligands and complexes was

established by elemental analysis and H NMR, FTIR, and

UV/Vis spectroscopies (see the Experimental Section). The

structures of 1d–3d were further confirmed by single-crystal

X-ray diffraction using the synchrotron radiation. A summa-

ry of the crystallographic data for 1d–3d is given in Table 1.

ACHTUNGTRENNUNG[N’-(2-methyl-3-phenylamine)oxamide] (H₄3a), were in turn

prepared from the reaction of the diethyl ester derivative of

either oxalic acid or N,N’-2-methyl-1,3-phenylenebis(oxamic

acid) (H₂Et₂1b) with an excess amount of fused 2-methyl-

1,3-phenylenediamine (1:10 ratio) in moderate to good

yields (67–72%) (Scheme 1b and d, respectively).

Description of the structures: The structures of 1d–3d con-

sist of double-stranded di-, tri-, and tetranuclear copper(II)

anions, [Cu^II(m₂-k²:k²-1b)₂]^4ꢀ, [Cu^II(m₃-k²:k²:k²-2b)₂]^6ꢀ, and

[Cu^II(m₄-k²:k²:k²:k²-3b)₂]^8ꢀ, respectively (Figures 1–3), tetra-

Scheme 1. Synthetic procedure for the diethyl ester acid derivatives of the oligo-m-phenylene oxalamide ligands H_2nꢀ2Et₂L (L=1b–3b; n=2–4) from the

corresponding diamine precursors H_2nꢀ41a–3a. Reaction conditions: a) C₂O₂Cl(OEt), Et₃N, THF (808C); b) C₂O₂A(OEt)₂(1208C); c) C₂O₂Cl(OEt), Et₃N,

THF (808C); d) 2-Me-1,3-C₆H₄NH₂(1208C); and e) C₂O₂Cl(OEt), Et₃N, THF (808C).

ACHTUNGTRENNUNG

AHCTUNGTRENNUNG

12840

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ꢉ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 2010, 16, 12838 – 12851

Copper(II) Mesocates

FULL PAPER

Scheme 2. Synthetic procedure for the tetra(alkyl/aryl) ammonium and phosphonium salts of the anionic oligo-m-phenylene oxalamide copper(II) com-

plexes [Cu_nL₂]^2nꢀ(L=1b–3b; n=2–4) from the corresponding sodium salts. Reaction conditions: a) NaOH, Cu

DMF (RT); c) nBu₄NOH, CuCl₂, H₂O/CH₂Cl₂(RT); d) AgNO₃, H₂O (RT); and e) EtPh₃PBr, H₂O/CH₃CN (RT).

ACHUTNTGERN(NUG NO₃)₂, H₂O (RT); b) NaH, CuACHTUNGTRENNUNG(NO₃)₂,

Table 1. Summary of crystallographic data for 1d–3d.

formula

M_r[gmol^ꢀ1

crystal

C₈₆H₁₆₄Cu₂N₈O₁₆C₁₆₀H_197.4Cu₃N₈O_42.7P₆C₂₁₈H₂₂₈Cu₄N₁₂O₃₆P₈

]

1693.27

3292.67

4094.17

triclinic

monoclinic

orthorhombic

system

space group C2/c

Pbcn

a [ꢊ]

b [ꢊ]

c [ꢊ]

a [8]

b [8]

23.959(5)

24.9780(10)

21.9780(10)

31.6890(10)

90.0

17396.2(12)

1.237

18.140(4)

18.340(4)

19.150(4)

117.86(3)

107.74(3)

90.84(3)

5271(2)

19.353(4)

22.494(5)

90.0

115.59(3)

90.0

9407(3)

1.190

Figure 1. a) Perspective view of the anionic dicopper(II) unit of 1d with

the atom-numbering scheme for the metal environments (symmetry

code: (I)=ꢀx, ꢀy, 1ꢀz). b) Top and c) side views of the dicopper(II)

double mesocate of 1d showing each ligand strand with a different tonali-

ty.

g [8]

V [ꢊ³]

1_calcd

[gcm^ꢀ3

1.287

]

m [mm^ꢀ1

T [K]

]

0.515

100(2)

0.494

100(2)

9454

0.531

100(2)

16440

independent 10151

reflns

obsd reflns

[I>2s(I)]

R^[a]

8527

8845

13161

0.0856

0.2653

0.0928

0.2334

1.066

0.0785

0.2308

1.048

(I>2s(I))

wR^[b]

(I>2s(I))

GOF^[c]

1.027

[a] R=ꢀ(jF_ojꢀjF_cj)/ꢀjF_oj. [b] wR=[ꢀw(jF_ojꢀjF_cj)²/ꢀwjF_oj ] ⁼

. [c] GOF=

[ꢀw(jF_ojꢀjF_cj)²/

n-butylammonium or ethyltriphenylphosphonium cations,

and crystallization water molecules. The di- and tetracop-

per(II) anions of 1d and 3d are centrosymmetric, whereas

the tricopper(II) anions of 2d have a crystallographically

imposed twofold symmetry. A summary of the structural

data for 1d–3d is given in Table 2. Selected bond lengths

and interbond angles for 1d–3d are listed in Tables 3–5.

Each pseudo C_h-(1b and 3b) or C₂-symmetric (2b) bridg-

ing ligand in 1d–3d possesses a nonplanar, almost orthogo-

Figure 2. a) Perspective view of the anionic tricopper(II) unit of 2d with

the atom-numbering scheme for the metal environments (symmetry

code: (I)=ꢀx, y, ¹= ꢀz). b) Top and c) side views of the tricopper(II)

double mesocate of 2d showing each ligand strand with a different tonali-

ty.

Chem. Eur. J. 2010, 16, 12838 – 12851

ꢉ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

12841

F. Lloret, Y. Journaux et al.

methyl substituents, which precludes the occurrence of ap-

preciable p–p interactions between the two parallel-dis-

placed benzene rings within the resulting metallacyclophane

cores (Figure 1b, Figure 2b, Figure 3b, and Figure 1c, Fig-

ure 2c, Figure 3c). The values of the centroid–centroid dis-

tance (h) are 4.442(1) (1d), 4.168(3) (2d), 3.776(3), and

4.317(3) ꢊ (3d), and those of the offset angle (f) between

the centroid–centroid vector and the normal to the plane of

the benzene ring are 42.33(9) (1d), 34.7(4) (2d), 29.3(4).

and 41.7(4)8 (3d) (Table 2). This situation contrasts with

that found in the previously reported dicopper(II) complex

with the parent unsubstituted bridging ligand N,N’-1,3-

phenylenebisACHTUNTRGNEUNG(oxamate), in which the two facing benzene

rings are disposed in an eclipsed syn configuration so as to

maximize the p–p interactions within the resulting metalla-

cyclophane core (h=3.3773(5) ꢊ and f=5.36(8)8).^[25a]

Figure 3. a) Perspective view of the anionic tetracopper(II) unit of 3d

with the atom-numbering scheme for the metal environments (symmetry

code: (I)=ꢀx, 1ꢀy, ꢀz). b) Top and c) side views of the tetracopper(II)

double mesocate of 3d showing each ligand strand with a different tonali-

ty.

Within the binuclear metallacyclophane cores of 1d–3d,

Cu₂(m-N₂C₆H₃Me)₂, the values of the Cu-N-C angle (a) are

in the range of 126.5(2)–127.0(2) (1d), 123.1(3)–125.6(4)

(2d), and 125.5(3)–126.7(4)8 (3d) (Table 2), which are simi-

lar to those reported for the related syn dicopper(II) double

mesocate (a=126.9(4)–132.1(4)8).^[25a]These values remain

close to that expected for trigonal sp²(a=120.08) rather

than tetrahedral sp³hybridization (a=109.48) for the ami-

date nitrogen atoms. The values of the torsion angle (f)

around the Cu-N-C-C bonds are in the range of 103.4(4)–

105.9(4) (1d), 100.7(6)–117.8(5) (2d), and 105.5(5)–121.5(5)8

(3d) (Table 2), which are farther from 908 than those report-

ed for the related syn dicopper(II) double mesocate (f=

73.6(2)–97.9(2)8).^[25a]Moreover, they deviate appreciably

more from 908 for the central metallacyclophane core (f=

117.2(5)–121.5(5)8) than for the two peripheral ones (f=

105.5(6)–112.4(6)8) in 3d (Table 2), thereby reflecting a

larger distortion from orthogonality between the mean

metal basal planes and the benzene rings.

Table 2. Summary of structural data for 1d–3d.

^[a][8]

73.5(3)

82.4(3)

4.442(1)

62.1(3)

84.0(4)

4.168(3)

65.0(2)

82.3(4)

3.776(3)

4.317(3)

29.3(4)

41.7(4)

125.5(3)

126.7(4)

105.5(5)

112.4(6)

117.2(5)

121.5(5)

38.7(2)

41.2(2)

h^[b][ꢊ]

f^[c][8]

a^[d][8]

42.33(9)

34.7(4)

126.5(2)

127.0(2)

103.4(4)

123.1(3)

125.6(4)

100.7(6)

^[e][8]

105.9(4)

117.8(5)

t^[f][8]

36.55(14)

39.3(2)

43.6(2)

Both the outer Cu(1) and inner Cu(2) atoms in 1d–3d

adopt a unique four-coordinated twisted geometry, which is

built by either two amidate nitrogen and two carboxylate

oxygen atoms from two bidentate oxamato donor groups,

Cu(1)N₂O₂, or by four amidate nitrogen atoms from two bi-

dentate oxamidato donor groups, Cu(2)N₄, respectively.

Thus, the values of the twist angle (t) of 36.55(14)8 for the

Cu(1) atom in 1d (Table 2) are intermediate between those

expected for square planar (t=08) and tetrahedral (t=908)

geometries, in contrast with the related syn dicopper(II)

double mesocate, which possesses a geometry close to

square planar (t=12.3(2)8).^[25a]The t values of 43.6(2) (2d)

and 41.2(2)8 (3d) for the Cu(2) atom are even greater than

those of 39.3(2) (2d) and 38.7(2)8 (3d) for the Cu(1) atom

(Table 2), thus indicating a stronger tetrahedral distortion

for the inner metal coordination site than for the outer one

in 2d and 3d, most likely because of the steric requirements

[a] Dihedral angle between the oxalamide and the benzene planes.

[b] Centroid–centroid distance between the benzene planes. [c] Offset

angle between the centroid–centroid vector and the normal to the ben-

zene plane. [d] Interbond Cu-N-C angle. [e] Torsion Cu-N-C-C angle.

[f] Twist angle at the metal atoms.

nal all-syn conformation of the oxamato and/or oxamidato

donor groups with respect to the 2-methyl-1,3-phenylene

spacers. The values of the dihedral angle (y) between the

oxalamide and the benzene planes are in the range of

73.5(3)–82.4(3) (1d), 62.1(3)–84.0(4) (2d), and 65.0(2)–

82.3(4)8 (3d) (Table 2). Two such linear bis- (1b), tris- (2b),

and tetrakis(bidentate) (3b) ligands clamp around the two,

three, and four copper atoms of 1d–3d in a side-by-side anti

arrangement. This side-by-side coordination binding mode

gives rise to an overall meso-helicate-type structure for the

anionic di-, tri, and tetracopper(II) units with approximate

C_2i(1d), D₂(2d), and C_2h(3d) molecular symmetries, re-

spectively (Figure 1a, Figure 2a, and Figure 3a). More likely,

the anti configuration of the oligonuclear copper(II) double

mesocates in 1d–3d obeys the steric requirements of the 2-

ꢀ

of the rigid mesocate structure. The values of the Cu(1) N-

(amidate) bond lengths in the range of 1.925(3)–1.944(3)

(1d), 1.947(5)–1.965(6) (2d), and 1.938(5)–1.943(5) ꢊ (3d)

ꢀ

are shorter than those of the Cu(1) O(carboxylate) ones,

which are in the range of 1.946(3)–1.961(3) (1d), 2.035(6)–

12842

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Chem. Eur. J. 2010, 16, 12838 – 12851

Copper(II) Mesocates

FULL PAPER

2.065(5) (2d), and 1.952(4)–1.956(5) ꢊ (3d) (Table 3,

Table 4, and Table 5), as previously found in the related syn

3d (Cu(1)-Cu(2)-Cu(2^I)=176.91(2)8) also have alternating

helical chiralities, thus leading to an overall achiral double

mesocate (M,P,M,P configuration), as in 1d. This series of

heterochiral double mesocates contrasts with the more

abundant homochiral double helicates reported in the litera-

ture, which result instead from helical wrapping of the li-

gands around the metal centers.^[12]The values of the inter-

metallic distance (r) between adjacent copper atoms across

the two 2-methyl-substituted 1,3-phenylenediamidate

ꢀ

dicopper(II) double mesocate (Cu N=1.925(5)–1.969(5) ꢊ

Table 3. Selected bond lengths [ꢊ] and interbond angles [8] for 1d.^[a]

ꢀ

Cu(1) N(1)

1.944(3)

Cu(1) N(2)

1.925(3)

ꢀ

Cu(1) O(1)

1.946(3)

Cu(1) O(4)

1.961(3)

84.29(14)

153.0(2)

97.69(13)

N(1)-Cu(1)-N(2)

N(1)-Cu(1)-O(4)

N(2)-Cu(1)-O(4)

107.58(13)

149.64(15)

84.18(12)

N(1)-Cu(1)-O(1)

N(2)-Cu(1)-O(1)

O(1)-Cu(1)-O(4)

bridges in an anti conformation for 1d–3d are comparable

ꢀ

(Cu(1) Cu(1 )=7.2019(12) ꢊ

(1d),

Cu(1) Cu(2)=

[a] The estimated standard deviations are given in parentheses.

ꢀ

7.3536(10) ꢊ (2d), Cu(1) Cu(2)=7.294(2) ꢊ, and Cu(2)

Cu(2^I)=7.395(2) ꢊ (3d)), which are somewhat greater than

that of the related syn dicopper(II) double mesocate (r=

6.822(2) ꢊ).^[25a]Otherwise, the values of the intermetallic

distance between the terminal copper atoms for 1d–3d in-

crease progressively along this series of anti oligocopper(II)

Table 4. Selected bond lengths [ꢊ] and interbond angles [8] for 2d.^[a,b]

ꢀ

Cu(1) N(1)

1.965(6)

Cu(1) N(3)

1.947(5)

ꢀ

Cu(1) O(1)

2.035(6)

1.960(4)

110.0(2)

151.2(2)

82.3(2)

Cu(1) O(5)

2.065(5)

1.986(4)

82.6(2)

155.8(2)

96.5(2)

ꢀ

Cu(2) N(2)

Cu(2) N(4)

ꢀ

double

mesocates

14.7037(15) (2d), and 21.975(5) ꢊ (3d)).

(Cu(1) Cu(1 )=7.2019(12)

(1d),

N(1)-Cu(1)-N(3)

N(1)-Cu(1)-O(5)

N(3)-Cu(1)-O(5)

N(2)-Cu(2)-N(4)

N(2)-Cu(2)-N(4^I)

N(1)-Cu(1)-O(1)

N(3)-Cu(1)-O(1)

O(1)-Cu(1)-O(5)

N(2)-Cu(2)-N(2^I)

N(4)-Cu(2)-N(4^I)

In the crystal lattice of 1d–3d, the anionic oligonuclear

copper(II) units establish diverse hydrogen bonds with the

crystallization water molecules through the carbonyl and/or

carboxylate oxygen atoms from the oxamato and/or oxami-

dato groups (O···Ow=2.762(5)–2.819(7) (1d), 2.701(5)–

2.881(6) ꢊ (2d), and 2.714(15)–2.868(11) ꢊ (3d)) (Fig-

103.85(18)

83.18(18)

153.2(3)

149.8(3)

[a] The estimated standard deviations are given in parentheses. [b] Sym-

metry code: (I)=ꢀx, y, ¹= ꢀz.

AHCTUNGTREGuNNNU res S1–S3 in the Supporting Information). Discrete dicop-

Table 5. Selected bond lengths [ꢊ] and interbond angles [8] for 3d.^[a]

per(II) anions are aligned along the c axis in 1d (Fig-

ure S1a), which are well separated from each other by the

bulky tetra-n-butylammonium cations (Figure S1b). In con-

trast, the tri- and tetracopper(II) anions of 2d and 3d, re-

spectively, are connected with each other through a variety

of hydrogen bonds that involve the hydrogen-bonded crys-

tallization water molecules (Ow···Ow=2.64(2)–2.91(2) (2d)

and 2.730(18)–2.894(12) ꢊ (3d)). This situation gives rise to

either extended layers of hydrogen-bonded tricopper(II)

anions that grow in the ac plane for 2d (Figure S2a) or

chains of hydrogen-bonded tetracopper(II) anions along the

[101] direction for 3d (Figure S3a), which are well separated

from each other by the bulky ethyltriphenylphosphonium

cations (Figure S2b and S3b). The value of the shortest in-

ꢀ

Cu(1) N(1)

1.938(5)

Cu(1) N(4)

1.943(5)

ꢀ

Cu(1) O(1)

1.956(5)

1.967(4)

1.973(4)

106.47(19)

152.2(2)

84.06(18)

82.58(17)

153.85(19)

102.79(16)

Cu(1) O(6)

1.952(4)

1.965(4)

84.1(2)

155.5(2)

96.8(2)

104.67(17)

152.29(18)

82.58(17)

ꢀ

Cu(2) N(2)

Cu(2) N(3)

ꢀ

Cu(2) N(5)

Cu(2) N(6)

N(1)-Cu(1)-N(4)

N(1)-Cu(1)-O(6)

N(4)-Cu(1)-O(6)

N(2)-Cu(2)-N(3)

N(2)-Cu(2)-N(6)

N(3)-Cu(2)-N(6)

N(1)-Cu(1)-O(1)

N(4)-Cu(1)-O(1)

O(1)-Cu(1)-O(6)

N(2)-Cu(2)-N(5)

N(3)-Cu(2)-N(5)

N(5)-Cu(2)-N(6)

[a] The estimated standard deviations are given in parentheses.

[25a]

ꢀ

and Cu O=1.928(4)–1.995(4) ꢊ).

from the well-known stronger ligand field of the amidate ni-

This is as expected

trogen donor atoms compared to the carboxylate oxygen

termolecular Cu(1) CuACTHNGUTERNNUG

(1^II) distance in 1d is 8.184(2) ꢊ,

ꢀ

ones.^[23a]The values of the Cu(2) N

(amidate) bond lengths

whereas those of the shortest intermolecular Cu(1) CuACHTUNGTRENNUNG

(1^II)

ꢀ

in the range of 1.960(4)–1.986(4) (2d) and 1.965(4)–

1.973(4) ꢊ (3d) (Tables 4 and 5) are, however, slightly

and Cu(1) Cu

(2^II) distances across the hydrogen-bonded

crystallization water molecules in 2d and 3d are 11.3909(15)

ꢀ

longer than those of the Cu(1) N

flecting the stronger tetrahedral distortion of the inner

copper atoms compared to the outer ones.

and 16.672(7) ꢊ, respectively (Figures S1a–S3a).

Redox properties: The cyclic voltammograms of 1d–3d in

acetonitrile (258C, 0.1m nBu₄NPF₆) are shown in Figure 4.

A summary of the electrochemical data for 1d–3d is given

in Table 6.

Complex 1d shows two closely spaced, quasireversible

one-electron oxidation waves at formal potentials of E₁=

+0.43 V and E₂=+0.65 V versus SCE, with anodic to catho-

dic peak separation values of DE₁=80 mV and DE₂=

100 mV, respectively (solid line in Figure 4a). Complex 2d

shows a reversible one-electron oxidation wave at a much

lower formal potential value of E₁=+0.17 V versus SCE

The two centrosymmetrically related Cu(1) and Cu(1^I)

atoms in 1d possess alternating helical chiralities (M,P con-

figuration), thus leading to an overall achiral dicopper(II)

double mesocate. Alternatively, there exists a racemic mix-

ture of tricopper(II) double mesocates in 2d with alternating

M,P,M and P,M,P helical chiralities at the twofold symmetri-

cally related Cu(1) and Cu(1^I) atoms and the Cu(2) atom,

which

are

almost

collinear

177.53(1)8). The two pairs of almost collinear, centrosym-

metrically related Cu(1)/Cu(1^I) and Cu(2)/Cu(2^I) atoms in

Chem. Eur. J. 2010, 16, 12838 – 12851

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12843

F. Lloret, Y. Journaux et al.

according to a metal-centered redox model that involves the

oxidation of the paramagnetic d⁹Cu^IIions (S_Cu=¹= ) to the

diamagnetic low-spin d⁸Cu^IIIions (S_Cu=0) (Scheme 3).

Thus, the two quasireversible, one-electron redox processes

for 1d correspond to the stepwise oxidation of the two outer

Cu^IIions to give the mixed-valent Cu^IICu^IIIand the high-

valent Cu^IIIspecies, respectively (Scheme 3a). Alternatively,

the first reversible, one-electron redox process of 2d is as-

cribed to the oxidation of the inner Cu^IIion to give the

stable (on the voltammetric timescale), singly oxidized

mixed-valent Cu^IICu^IIIspecies (Scheme 3b), whereas the

two first reversible, one-electron redox processes of 3d are

accordingly ascribed to the stepwise oxidation of the two

inner Cu^IIions to give the stable, singly- and doubly-oxi-

dized mixed-valent species Cu^IICu^IIIand Cu^IICu^III₂, respec-

tively (Scheme 3c). The second and the third quasireversi-

ble, two-electron redox processes of 2d and 3d are then as-

signed to the simultaneous oxidation of the two noninteract-

ing outer Cu^IIions to render the triply oxidized high-valent

Cu^IIIand the quadruply oxidized high-valent Cu^IIIspecies,

Figure 4. CV and RDE voltammograms (solid and dotted lines, respec-

respectively (Scheme 3b and c).

tively) of a) 1d, b) 2d, and c) 3d in acetonitrile (258C, 0.1m nBu₄NPF₆).

The separation in the formal potential values between the

two first one-electron oxidation waves (DE₁₂=E₂ꢀE₁) of

220 (1d) and 110 mV (3d) is related to the ability of the 2-

methyl-substituted 1,3-phenylene spacers to transmit elec-

tronic interactions between the metal centers. The observed

difference in the DE₁₂values for 1d and 3d gives an estima-

tion of the relative magnitude of the outer–outer and inner–

inner pairwise electronic interactions in the corresponding

Table 6. Selected electrochemical data for 1d–3d.^[a]

[b]

[c]

Complex E₁[V]

E₂[V]

E₃[V]

DE₁₂[mV] K_c^[d]

+0.43 (80) +0.65 (100)

+0.17 (70) +0.67 (90)

+0.14 (70) +0.25 (70)

220

0.5ꢋ10⁴

+0.66 (90) 110

0.7ꢋ10²

[a] In acetonitrile (258C, 0.1m nBu₄NPF₆). [b] All formal potential values

were taken as the half-wave potentials versus SCE. The peak-to-peak

separations (DE) between the anodic (E_a) and cathodic (E_c) peak poten-

tials are given in parentheses [mV]. [c] Difference in the formal potential

values between the two first one-electron oxidation waves. [d] The com-

proportionation constant values were calculated through the expression

logK_c=DE₁₂/59.

mixed-valent Cu^IICu^IIIand Cu^IICu^IIIintermediates, respec-

tively. Thus, the calculated values of the comproportionation

constant (K_c) of 5000 (1d) and 70 (3d) clearly evidence the

lower thermodynamic stability of the mixed-valent Cu^IICu^III

(DE₁=70 mV), which is well

separated from a pseudoreversi-

ble two-electron oxidation wave

at E₂=+0.67 V versus SCE

(DE₂=90 mV) (solid line in

Figure 4b). Complex 3d shows

instead not one but two closely

spaced reversible one-electron

oxidation waves at low formal

potential

+0.14 V (DE₁=70 mV) and

E₂=+0.25 V versus SCE

values

E₁=

Scheme 3. Metal-centered redox model for a) 1d, b) 2d, and c) 3d.

(DE₂=70 mV), which are also

well-separated from a pseudo-

reversible two-electron oxidation wave at E₃=+0.66 V

versus SCE (DE₃=90 mV) (solid line in Figure 4c). The

intermediate compared with the Cu^IICu^IIIone (Table 6). The

relatively weaker electronic coupling between the inner

mono- or bi

metal centers in the mixed-valent Cu^IICu^IIIintermediate

3d has been confirmed by rotating-disk electrode (RDE)

measurements (dotted lines in Figure 4).

The rich redox behavior for 1d–3d depending on the dif-

ferent nuclearity and the distinct metal coordination envi-

ronments of each species can be appropriately interpreted

can be attributed, at least in part, to the steric hindrance of

the rigid tetranuclear mesocate structure in 3d that prevents

the orthogonality between the bis(oxamidato)metal moieties

and the methyl-substituted meta-phenylene spacers (f=

119.3(5)8) (Table 2).

12844

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Chem. Eur. J. 2010, 16, 12838 – 12851

Copper(II) Mesocates

FULL PAPER

The trend in both the thermodynamic and the kinetic sta-

temperature, c_MT is equal to 0.84 (1d), 1.27 (2d), and

1.69 cm³mol^ꢀ1K (3d), values that are close to those expect-

ed for either two, three, or four magnetically noninteracting

bility of the oxidized, mixed-valent copper

ACHTUNGTREN(NUGN II,III) and high-

valent copper(III) species along this series is as expected on

ACHTUNGTRENNUNG

the basis of ligand field-stabilization effects. In fact, the rela-

tive gain in crystal-field stabilization energy for the change

from a square planar d⁹Cu^IIto a low-spin d⁸Cu^IIIelectronic

configuration is the main factor in the overall thermody-

Cu^IIions, respectively [c_MT=nꢋ(Nb²g_Cu²/3k)S

_CuACHTUNGTRENNU(G S_Cu+1)=

0.83 (n=2), 1.26 (n=3), and 1.69 cm³mol^ꢀ1K (n=4) with b

is the Bohr magneton, k is the Boltzman constant, g_Cuis the

Zeeman factor for the Cu^IIion, with a value of 2.1, and

namic stability of related mononuclear copper

_Cu=¹= ]. The value of c_MT continuously increases upon

plexes with oxamidato and/or oxamato donor groups.^[23a]

Thus, lower potentials and higher reversibility are associated

with the oxidation of the inner Cu^IIions with a CuN₄chro-

mophore (E values in the range of +0.14 to 0.25 V vs. SCE

and DE values of 70 mV) when compared with those of the

outer Cu^IIions with a CuN₂O₂chromophore (E values in

the range of +0.43 to 0.67 V vs. SCE and DE values in the

range of 80 to 100 mV), as previously reported.^[23a]In this

case, the stabilization of the trivalent oxidation state of

copper is explained in terms of the stronger ligand field af-

forded by the N,N’-oxamidato groups compared to that of

the N,O-oxamato ones, as evidenced by the visible absorp-

tion maxima of the corresponding oligonuclear copper(II)

complexes 1d–3d (see the Experimental Section).

cooling to reach maximum c_MT values of 1.07 (1d), 2.07

(2d), and 3.26 cm³mol^ꢀ1K (3d) (Figure 5a). This magnetic

behavior is characteristic of an overall intramolecular ferro-

magnetic coupling between the local spin doublets (S_Cu=¹= )

of each Cu^IIion to give a resultant high-spin S=nꢋS_Cu

ground state for the Cu^II_nlinear entity. In fact, the maximum

c_MT values at 6.5 (1d) and 2.0 K (2d and 3d) are close to

those expected for S=1 Cu^II, S=³= Cu^II, and S=2 Cu^II

ground states, respectively (c_MT=(Nb²g²/3k)S

ACHTUNGTRENNUNG

slightly decreases, likely due to zero-field splitting (ZFS) ef-

fects of the S=1 Cu^II₂ground state (inset of Figure 5a).

The overall ferromagnetic behavior for 1d–3d is con-

firmed by the M versus H plots at 2.0 K, M being the molar

Magnetic properties: The c_MT versus T plots of 1d–3d, c_M

magnetization per Cu^II(n=2–4) unit and H the applied

being the molar magnetic susceptibility per Cu^II(n=2–4)

field (Figure 5b). Thus, the maximum M values at H=5.0 T

are 1.94 (1d), 3.10 (2d), and 4.13 Nb (3d), values that are

close to the calculated saturation magnetization values for

the parallel (ꢀspin-upꢁ) alignment of the local spin doublets

unit and T the temperature, are shown in Figure 5. At room

of each Cu^IIion within the Cu^IIlinear entity (M_s=nꢋ

g_CuS_CuNb =2.10 (n=2), 3.15 (n=3), and 4.20 Nb (n=4)

with g_Cu=2.1 and S_Cu=¹= ). Moreover, the isothermal mag-

netization curves of 2d and 3d are well matched by the Bril-

louin functions for a quartet (S=³= ) and a quintet (S=2)

spin state, respectively, with g=2.1 (solid lines in Figure 5b).

The isothermal magnetization curve of 1d is, however,

slightly below the Brillouin function for a triplet (S=1) spin

state with g=2.1, thus indicating the nonnegligible role of

the ZFS effects (dotted line in Figure 5b).

The temperature dependence of the magnetic susceptibili-

ty data of 1d–3d was analyzed according to the spin Hamil-

tonian for di- (1d), tri- (2d), and tetranuclear (3d) linear

models [Eqs. (1)–(3)] with S_i=S_Cu=¹= for i=1ꢀn with n=

2–4, respectively:

H ¼ ꢀJS₁ꢁ S₂þ DS²_zþ gðS₁þ S₂ÞbH

ð1Þ

H ¼ ꢀJ⁰ðS₁ꢁ S₂þ S₂ꢁ S₃ÞꢀjS₁ꢁ S₃þ gðS₁þ S₃ÞbH þ g⁰S₂bH

ð2Þ

H ¼ ꢀJ⁰ðS₁ꢁ S₂þ S₃ꢁ S₄ÞꢀJ⁰⁰ðS₂ꢁ S₃Þꢀj⁰ðS₁ꢁ S₃þ S₂ꢁ S₄Þ

þgðS₁þ S₄ÞbH þ g⁰ðS₂þ S₃ÞbH

ð3Þ

in which J, J’, and J’’ are the magnetic coupling parameters

that correspond to the outer–outer, inner–outer, and inner–

inner pairwise interactions between the next-neighbor Cu^II

ions, respectively, whereas j and j’ are the magnetic coupling

Figure 5. a) c_MT versus T and b) M versus H plots at 2.0 K of 1d ( ), 2d

(

), and 3d (&). The inset shows the c_MT versus T plot of 1d in the low-

temperature region. The solid and dotted lines are the best-fit curves

(see text).

Chem. Eur. J. 2010, 16, 12838 – 12851

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www.chemeurj.org

12845

F. Lloret, Y. Journaux et al.

c_MT ¼ ðNb²g_Cu²=4k_BÞ½10 þ expðꢀJ⁰=2k_BTÞ þ expðꢀ3J⁰=2k_BTÞꢂ

parameters that correspond to the outer–outer and inner–

outer pairwise interactions between the next-nearest-neigh-

bor Cu^IIions, respectively (solid and dotted lines, respective-

ly, in Scheme 4). In Equations (1)–(3), D is the axial mag-

netic anisotropy parameter for the ground S=1 state of 1d,

whereas g and g’ are the Zeeman factors for the outer and

inner Cu^IIions of 2d and 3d, respectively.

=½2 þ expðꢀJ⁰=2k_BTÞ þ expðꢀ3J⁰=2k_BTÞꢂ

ð5Þ

c_MT ¼ ð2Nb²g_Cu²=k_BÞ½5 þ expðꢀJ⁰=k_BTÞ þ expfꢀ½J⁰þ J⁰⁰ꢀ

ðJ⁰²þ J⁰⁰²Þ ꢂ=2k_BTg þ expfꢀ½J þ J þ ðJ þ J⁰⁰²Þ ꢂ=2k_BTgꢂ

=½5 þ 3expðꢀJ⁰=k_BTÞ þ 3expfꢀ½J⁰þ J⁰⁰ꢀðJ⁰²þ J⁰⁰²Þ ꢂ=2k_BTÞg

þ3expfꢀ½J⁰þ J⁰⁰þ ðJ⁰²þ J⁰⁰²Þ ꢂ=2k_BTg

002

þexpfꢀ½2J þ J ꢀð4J ꢀ2J J þ J Þ ꢂ=2k_BTÞg

þexpfꢀ½2J þ J þ ð4J ꢀ2J J þ J Þ ꢂ=2k_BTgꢂ

002

ð6Þ

Scheme 4. Spin-coupling model for a) 1d, b) 2d, and c) 3d.

The moderate ferromagnetic coupling between the Cu^IIions

A summary of the least-squares fitting magnetic data

through the appropriate analytical expressions [Eqs. (4)–(6)]

derived from the above spin Hamiltonians for 1d–3d is

given in Table 7.^[26–28]For 2d and 3d, the next-nearest-neigh-

within the Cu^II(n=2–4) linear entity for 1d (J=

+16.4 cm^ꢀ1), 2d (J’=+16.6 cm^ꢀ1), and 3d (J’=+15.0 cm^ꢀ1

and J’’=+16.8 cm^ꢀ1) suggests that the EE interaction

through the two 2-methyl-substituted 1,3-phenylenediami-

date bridges in an anti configuration involves a spin-polari-

zation mechanism, as previously found in the parent syn di-

copper(II) double mesocate with the unsubstituted bridging

Table 7. Selected magnetic data for 1d–3d.

[c]

Complex J^[a]

[cm^ꢀ1

J’^[a]

J’’^[a]

D^[b]

g_Cu

R^[d]ꢋ10⁵

ligand N,N’-1,3-phenylenebisACHTUNGTRNEUNG

(oxamate) (J=+16.8 cm^ꢀ1).^[25a]

]

[cm^ꢀ1

]

[cm^ꢀ1

]

[cm^ꢀ1

]

In fact, a moderate ferromagnetic coupling has been report-

ed for two related dicopper(II) double mesocates with di-

verse coordinating-group-substituted m-phenylenediamidate

bridging ligands in an anti configuration, independently of

the nature of the donor groups.^[14k,l]In general, there is no

simple correlation between the magnitude of the ferromag-

netic coupling and the structural and electronic factors for

these anti dicopper(II) complexes that possess an overall

twisted coordination geometry of the Cu^IIions and a pro-

nounced distortion from orthogonality between the mean

metal basal planes and the benzene rings as those observed

in 1d. Yet the J value is remarkably stronger for the dicop-

per(II) complex with the N,N’-1,3-phenylenebis(pyridine-2-

carboxamidate) ligand (J=+21.1 cm^ꢀ1)^[14l]than that found

+16.4

+1.7

2.10 2.5

2.10 2.6

2.10 2.4

+16.6

+15.0

+16.8

[a] Magnetic coupling parameters in Equations (1)–(3) (see text).

[b] Axial magnetic anisotropy parameter in Equation (1) (see text).

[c] Zeeman factor in Equations (1)–(3) (see text). [d] Agreement factor

defined as R=ꢀ

ꢀ

bor interactions between the Cu^IIions within the Cu^II(n=3

and 4) linear entity were assumed to be negligible (see the

theoretical calculations below) and the Zeeman factors of

the outer and inner Cu^IIions were imposed to be identical

[Eqs. (2) and (3) with j=j’=0 and g=g’=g_Cu]. The theoreti-

cal curves for 1d–3d closely follow the experimental data

over the whole temperature range (solid lines in Figure 5a).

In particular, the theoretical curve for 1d reproduces well

the maximum of c_MT that results from the negative axial

ZFS of the S=1 ground state (D=1.7 cm^ꢀ1) when compared

with that which results by neglecting the axial ZFS (D=0),

which would exhibit a plateau at low temperatures (solid

and dotted lines, respectively, in the inset of Figure 5a). In

fact, the isothermal magnetization curve of 1d is well repro-

duced by the theoretical curve for a triplet spin state with

g=2.1 and D=+1.7 cm^ꢀ1obtained by the fit of the magnet-

ic susceptibility data (solid line in Figure 5b).

with

N,N’-1,3-phenylenebis(acetylacetonecarboxamidate)

(J=+14.6 cm^ꢀ1),^[14k]which is similar to that found for 1d

(J=+16.4 cm^ꢀ1). It thus appears that the strength of the fer-

romagnetic coupling along this series of anti dicopper(II)

double mesocates with meta-substituted phenylene spacers

may be tuned by the electronic nature of the donor groups

of the bridging ligand. In this regard, a relatively stronger

ferromagnetic coupling between the inner Cu^IIions (J’’=

+16.8 cm^ꢀ1) with respect to that between the outer and

inner Cu^IIions (J’=+15.0 cm^ꢀ1) is observed for 3d, in spite

of the larger distortion from planarity of the inner metal

atoms compared to the outer ones (t=41.2(2) and 38.7(2)8,

respectively) and the larger deviation from orthogonality of

the mean metal basal planes and the benzene rings (f=

119.3(5) and 108.9(6)8, respectively) (Table 2). This situation

may be also explained by electronic factors associated with

the greater spin delocalization from the inner Cu^IIions

(CuN₄chromophore) toward the N,N’-oxamidato donor

c_MT ¼ ð2Nb²g_Cu²=3k_BÞ ½ð2T=DÞexpð2D=3kTÞ þ ð1ꢀ2T=DÞexp

ðꢀD=3kTÞꢂ=½expð2D=3k_BTÞ þ 2 expðꢀD=3k_BTÞ þ expðꢀJ=k_BTÞꢂ

ð4Þ

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Chem. Eur. J. 2010, 16, 12838 – 12851

Copper(II) Mesocates

FULL PAPER

groups compared to that of the outer Cu^IIions (CuN₂O₂

chromophore) toward the N,O-oxamato ones.

Theoretical calculations: DFT energy calculations on 1d–3d

show highest-multiplicity, triplet (1d), quartet (2d), and

quintet (3d) spin ground states, which are in agreement with

the overall ferromagnetic coupling observed experimentally.

A summary of the calculated magnetic coupling parameters

for 1d–3d determined from the energy levels of the relevant

spin states is given in Table 8 (see the computational meth-

Table 8. Selected theoretical data for 1d–3d.

Complex J^[a][cm^ꢀ1

]

J’^[a][cm^ꢀ1

]

J’’^[a][cm^ꢀ1

]

j^[a][cm^ꢀ1

]

j’^[a][cm^ꢀ1

ꢀ0.01

]

+15.8

+16.1

+15.2

+0.01

Figure 6. a) Front and b) top projection views of the calculated spin-den-

sity distribution for the ground spin quintet configuration of 3d. Gray

and black contours represent positive and negative spin densities, respec-

+16.5

[a] Magnetic coupling parameters in Equations (1)–(3) (see text).

tively. The isodensity surface corresponds to a value of 0.0025 ebohr^ꢀ3

ods below). The calculated values of the magnetic coupling

parameters that correspond to the outer–outer (J), inner–

outer (J’), and inner–inner (J’’) pairwise interactions be-

tween the next-neighbor Cu^IIions for 1d (J=+15.8 cm^ꢀ1),

2d (J’=+16.1 cm^ꢀ1), and 3d (J’=+15.2 cm^ꢀ1and J’’=

+16.5 cm^ꢀ1) agree perfectly well with the experimental ones

obtained from the fit of the experimental magnetic suscepti-

bility data (Table 7). In particular, the calculated trend as

J’<J’’ found for 3d follows that observed experimentally,

which is in agreement with the larger electron donor capaci-

ty of the N,N’-oxamidato donor groups relative to that of

the N,O-oxamato ones. Moreover, the calculated values of

the magnetic coupling parameters that correspond to the

outer–outer (j) and inner–outer (j’) pairwise interactions be-

tween the next-nearest-neighbor Cu^IIions for 2d (j=

+0.01 cm^ꢀ1) and 3d (j’=ꢀ0.01 cm^ꢀ1) are negligible, thereby

ensuring the validity of the model used to fit the experimen-

tal magnetic susceptibility data.

The natural bond orbital (NBO) analysis of the calculated

atomic spin densities for the longer member of this series, as

an illustrative example, conforms to a spin polarization

mechanism for the propagation of the EE interaction be-

tween the linear array of metal centers through the p-type

orbital pathways of the two oligo-m-phenyleneoxalamide

bridging ligands. Despite the significant distortion from pla-

narity of the metal atoms in 3d (t=38.7(2) and 41.2(2)8)

(Table 2), the calculated spin-density distribution for the

ground-spin quintet configuration of 3d shows that the orbi-

tals that contain the unpaired

with the available p-type orbitals of the 2-methyl-1,3-phen-

ylene spacers, which are mainly made up by the p_z(C) orbi-

tals from the benzene rings with an almost negligible contri-

bution from the p_z(C) orbital from the methyl substituent.

This situation leads to the operation of a s–p interaction

ꢀ

(N C hyperconjugation) within the p-system of the 2-

methyl-1,3-phenylenediamidate bridges that involves the

sp²-type orbitals of the nitrogen atoms that are oriented

nearly parallel to the p_z-type orbitals of the carbon atoms

because of the almost orthogonal disposition of the metal

basal plane of each twisted Cu^IIion with respect to the

mean plane of the benzene rings in 3d (f=108.9(6)8)

(Table 2).^[26]

The calculated values of the atomic spin density (1) along

the metal–organic backbone in 3d provide a precise picture

of the relative importance of the spin-delocalization and

spin-polarization effects (Scheme 5). Thus, the values of the

spin density at the amidate nitrogen donor atoms are large

(1_Nin the range of +0.09 to 0.11 e) and are slightly greater

than that at the carboxylate-oxygen ones (1_O=+0.08 e).

More importantly, they have the same sign as those for the

copper atoms, which are slightly smaller for the inner than

for the outer ones (1_Cu=+0.55 and 0.56 e, respectively).

Overall, this situation indicates that the spin delocalization

from the metals towards the N,N’-oxamidato donor groups

dominates over that of the N,O-oxamato ones because of

ꢀ

the stronger covalency of the Cu NACTHNUTRGNEUNG(amidate) bonds com-

electron (ꢀmagnetic orbitalsꢁ) at

each Cu^IIion are mainly s-type

d_x₂_ꢀy₂(Cu) orbitals. In fact, these

orbitals that point toward the

ꢀ

Cu N/O bonds from the oxa-

mato and/or oxamidato donor

groups are largely delocalized

into the sp²

ACHTUNGTRENNUNG(N/O) orbitals

Scheme 5. Spin-density distribution on the metal–organic backbone for 3d with calculated average atomic spin

(Figure 6). They partly overlap densities. Empty and full contours represent positive and negative spin densities, respectively.

Chem. Eur. J. 2010, 16, 12838 – 12851

ꢉ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

12847

F. Lloret, Y. Journaux et al.

ꢀ

pared to the Cu O(carboxylate) ones. On the other hand,

organic spacers act as ferromagnetic coupling units (FCUs)

between the outer copper(II)-bisACHTGNUTERNNU(G oxamato) and the inner

copper(II)-bis(oxamidato) moieties, which serve in turn as

mere spin-containing and redox-switchable spin-containing

units, respectively (Scheme 6). In fact, future applications

the sign alternation of the spin density at the benzene

carbon atoms of the 2-methyl-1,3-phenylene spacers agrees

with a spin polarization by the amidate nitrogen donor

atoms (Scheme 5), thus leading to nonnegligible values of

the spin density of the opposite sign at the carbon atoms to

which they are directly attached (1_C=ꢀ0.02 e). Because of

the meta-substitution pattern of the 2-methyl-1,3-phenylene

spacers, with an odd number of carbon atoms between the

two amidate nitrogen donor atoms, the spin densities at the

adjacent copper atoms have identical signs. Hence, a net fer-

romagnetic exchange interaction results along the linear

metal array in 3d, as expected for the peculiar topology of

the oligo-m-phenyleneoxalamide bridging ligands.

Scheme 6. Spin model of the electroswitchable ferromagnetic coupling in

linear oligo-m-phenylene oxalamide copper(II) double mesocates.

Conclusion

may be envisaged for this new class of electroswitchable mo-

lecular magnetic wires, referred to as ꢀmetal–organic wiresꢁ

(MOWs), in the emerging field of molecular spintronics as

multiple spin-quantum bits (Qubits) and spin-quantum dots.

A novel family of oligonuclear copper(II) string complexes

with unique structural and electronic (magnetic and redox)

properties have been prepared by following a molecular-

programmed approach based on ligand design. In fact, the

side-by-side self-assembly of a new generation of linear

homo- and heterotopic oligo(2-methyl-1,3-phenyleneoxala-

mide) ligands by Cu^IIions leads to double-stranded, di-, tri-,

and tetracopper(II) species of meso-helicate type (so-called

mesocates) depending on the number of oxalamide metal-

binding sites, from two to three and four, respectively. In

this case, the unique formation of copper(II) double meso-

cates is favored because the relatively short and rigid char-

acter of the methyl-substituted phenylene spacer prevents

the helical twisting of each ligand around the metal centers

to give the more common helicates.

Experimental Section

Materials: All chemicals were of reagent grade quality and they were

purchased from commercial sources and used as received, except those

for the electrochemical measurements. The nBu₄NPF₆salt was recrystal-

lized twice from ethyl acetate/diethyl ether, dried at 808C under vacuum,

and kept in an oven at 1108C. Acetonitrile was purified by distillation

from calcium hydride onto activated 3 ꢊ molecular sieves and stored

under argon.

Compound H₂Et₂1b: Ethyl oxalyl chloride ester (14.0 mL, 120 mmol)

was poured into a solution of 2-methyl-1,3-phenylenediamine 1a (7.32 g,

60 mmol) in THF (250 mL) under vigorous stirring at 08C in an ice bath.

The reaction mixture was charged with triethylamine (16.8 mL,

120 mmol) and it was heated to reflux for 1 h. The white solid was col-

lected by filtration after cooling, washed thoroughly with water to

remove the impurity of Et₃NHCl, and dried under vacuum. Yield: 17.4 g,

90%; ¹H NMR (200 MHz, [D₆]DMSO, 258C, TMS): d=1.31 (t, 6H;

2CH₃), 2.03 (s, 3H; CH₃of (2-CH₃)C₆H₃), 4.30 (q, 4H; 2CH₂O), 7.23 (s,

3H; 4-H, 5-H, and 6-H of (2-CH₃)C₆_ꢀH_{1 3}), 10.42 ppm (s, 2H; 2NH); IR

These di-, tri-, and tetracopper(II) double mesocates ex-

hibit ferromagnetic and multicenter redox behaviors. There-

fore a moderate ferromagnetic coupling between the un-

paired electrons of the linearly disposed Cu^IIions (S_Cu=¹= )

through the two 2-methyl-1,3-phenylene spacers of meta-

substitution pattern is operative along the linear metal array

with overall intermetallic distances between the outer metal

centers in the range of 0.7–2.2 nm. Moreover, by taking ad-

vantage of the distinct electron-donating ability (basicity) of

the outer oxamato and the inner oxamidato donor groups,

ꢀ

(KBr): n˜ =3249 (N H), 1734, 1683 cm (C=O); elemental analysis calcd

(%) for C₁₅H₁₈N₂O₆: C 55.90, H 5.59, N 8.70; found: C 55.77, H 5.09, N

9.01.

Compound H₂2a: Diethyl oxalyl ester (16.0 mL, 80 mmol) was mixed

with an excess amount of 1a (48.8 g, 400 mmol), and the resulting mix-

ture was fused at 1208C and allowed to react for 24 h under Ar. The gray

solid that appeared was collected by filtration, washed thoroughly with

methanol to remove the unreacted 1a, and dried under vacuum. Yield:

17.0 g, 72%; ¹H NMR (200 MHz, [D₆]DMSO, 258C, TMS): d=2.11 (s,

6H; 2CH₃of (2-CH₃)C₆H₃), 4.95 (s, 4H; 2NH₂), 7.25 (t, 2H; 5-H of (2-

stable mixed-valent tri- and tetracopperACTHNUTRGENUG(N II,III) oxidized spe-

cies are available through the site-selective oxidation of the

inner metal centers. That being so, the ferromagnetic cou-

pling between the unpaired electrons of the outer d⁹Cu^II

ions (S_Cu=¹= ) can be interrupted or restored by a reversible

CH₃)C₆H₃), 7.35 (d, 4H; 4-H and 6-H of (2-CH₃)C₆H₃), 10.30 ppm (s,

ꢀ1

ꢀ

2H; 2NH); IR (KBr): n˜ =3446, 3362, 3267 (N H), 1691, 1621, 1611 cm

redox process that involves the consecutive one-electron ox-

(C=O); elemental analysis calcd (%) for C₁₆H₁₈N₄O₂: C 64.43, H 6.04, N

idation of the inner d⁹Cu^IIions (S_Cu=¹= ) to low-spin d⁸

18.7; found: C 65.67, H 5.29, N 19.08.

Cu^IIIions (S_Cu=0).

Compound H₄Et₂2b: Ethyl oxalyl chloride ester (7.0 mL, 60 mmol) was

poured into a solution of H₂2a (8.9 g, 30 mmol) in THF (250 mL) under

vigorous stirring at 08C in an ice bath. The reaction mixture was charged

with triethylamine (8.4 mL, 60 mmol) and it was heated to reflux for 1 h.

The white solid was collected by filtration after cooling, washed thor-

oughly with water to remove the impurity of Et₃NHCl, and dried under

vacuum. Yield: 14.4 g, 97%;¹H NMR (200 MHz, [D₆]DMSO, 258C,

TMS): d=1.32 (t, 6H; 2CH₃), 2.11 (s, 6H; 2CH₃of (2-CH₃)C₆H₃), 4.31

This series of redox-active, ferromagnetically coupled oli-

gonuclear copper(II) double mesocates with high-multiplici-

ty S=nꢋ¹= (n=2–4) ground states would thus behave as ef-

fective electroswitchable molecular magnetic wires for the

transmission of EE interactions of ferromagnetic nature

over long distances. In this case, the two m-phenylene-type

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Chem. Eur. J. 2010, 16, 12838 – 12851

Copper(II) Mesocates

FULL PAPER

(q, 4H; 2CH₂O), 7.26 (t, 2H; 5-H of (2-CH₃)C₆H₃), 7.37 (d, 4H; 4-H and

(0.80 g, 0.5 mmol) in water (20 mL) under stirring at room temperature.

The dark green solid that appeared was collected by filtration, suspended

in water (10 mL), and then charged with a solution of PPh₃EtBr (1.10 g,

3 mmol) in acetonitrile (5 mL). The reaction mixture was further stirred

for 30 min under gentle warming and then filtered to remove the precipi-

tate of AgCl. Large dark green cubes of 2d suitable for X-ray diffraction

were obtained by slow evaporation of the filtered solution after several

days in air at room temperature. Yield: 1.2 g, 90%; IR (KBr): n˜ =1656,

1612 cm^ꢀ1(C=O); UV/Vis (CH₃CN): l_max(e)=225 (189000), 265

(53000), 390 (3400), 590 nm (405m^ꢀ1cm^ꢀ1); elemental analysis calcd (%)

for C₁₆₀H_197.4Cu₃N₈O_42.7P₆: C 58.37, H 6.04, N 3.40; found: C 58.81, H

6.01, N 3.33.

6-H of (2-CH₃)C₆H₃), 10.44 ppm (s, 4H; 4NH); IR (KBr): n˜ =3364, 3229

(N H), 1737, 1687 cm^ꢀ1(C=O); elemental analysis calcd (%) for

ꢀ

C₂₄H₂₆N₄O₈: C 57.83, H 5.22, N 11.24; found: C 59.34, H 5.01, N 10.91.

Compound H₄3a: H₂Et₂1b (6.4 g, 20 mmol) was mixed with an excess

amount of 1a (24.4 g, 200 mmol), and the resulting mixture was fused at

1208C and allowed to react for 48 h under Ar. The gray solid that ap-

peared was collected by filtration, washed thoroughly with methanol to

remove the unreacted 1a, and dried under vacuum. Yield: 6.4 g, 67%;

¹H NMR (200 MHz, [D₆]DMSO, 258C, TMS): d=2.08 (s, 6H; 2CH₃of

(2-CH₃)C₆H₃), 2.12 (s, 3H; CH₃of (2-CH₃)C₆H₃), 4.94 (s, 4H; 2NH₂),

7.26 (t, 3H; 5-H of (2-CH₃)C₆H₃), 7.39 (d, 6H; 4-H and 6-H of (2-

ꢀ

CH₃)C₆H₃), 10.24 ppm (s, 2H; 4NH); IR (KBr): n˜ =3349, 3254 (N H),

Compound Na₈CAHTUGNTNERNN[GU Cu₄ACHUTNRTEGUNNG(N 3b)₂]·16H₂O (3c): A solution of CuACHTUNGTREN(UNNG NO₃)₂·3H₂O

1711, 1698 cm^ꢀ1(C=O); elemental analysis calcd (%) for C₂₅H₂₆N₆O₄: C

(0.96 g, 4 mmol) in DMF (5 mL) was added dropwise to a solution of

H₆Et₂3b (1.34 g, 2 mmol) and NaH (0.38 g, 16 mmol) in DMF (25 mL)

under stirring at room temperature. The deep green solid of 3c that ap-

peared was collected by filtration, washed with methanol, acetone, and

diethyl ether, and dried under vacuum. Yield: 1.8 g, 95%; IR (KBr): n˜ =

1625, 1600 cm^ꢀ1(C=O); UV/Vis (H₂O): l_max(e)=245 (77500), 310

(23300), 380 (9980), 593 nm (700m^ꢀ1cm^ꢀ1); elemental analysis calcd (%)

for C₅₈H₆₈Cu₄N₁₂Na₈O₃₆: C 35.77, H 3.49, N 8.63; found: C 35.15, H 3.23,

N 8.81.

63.29, H 5.49, N 17.72; found: C 63.87, H 5.33, N 18.02.

Compound H₆Et₂3b: Ethyl oxalyl chloride ester (2.3 mL, 20 mmol) was

poured into a solution of H₄3a (4.7 g, 10 mmol) in THF (250 mL) under

vigorous stirring at 08C in an ice-bath. The reaction mixture was charged

with triethylamine (2.8 mL, 20 mmol) and it was heated to reflux for 1 h.

The white solid was collected by filtration after cooling, washed thor-

oughly with water to remove the impurity of Et₃NHCl, and dried under

vacuum. Yield: 6.3 g, 93%; ¹H NMR (200 MHz, [D₆]DMSO, 258C,

TMS): d=1.32 (t, 6H; 2CH₃), 2.09 (s, 6H; 2CH₃of (2-CH₃)C₆H₃), 2.14

(s, 3H; CH₃of (2-CH₃)C₆H₃), 4.31 (q, 4H; 2CH₂O), 7.26 (t, 3H; 5-H of

(2-CH₃)C₆H₃), 7.39 (d, 6H; 4-H and 6-H of (2-CH₃)C₆H₃), 10.45 ppm (s,

Compound (EtPh₃P)₈ACTHUNRGTNNEUG[Cu₄CAHTUNGTREN(NUGN 3b)₂]·16H₂O (3d): An aqueous solution

(10 mL) of AgNO₃(0.66 g, 4 mmol) was added to a solution of 3c

(0.97 g, 0.5 mmol) in water (20 mL) under stirring at room temperature.

The dark green solid that appeared was collected by filtration, suspended

in water (10 mL), and then charged with a solution of PPh₃EtBr (1.47 g,

4 mmol) in acetonitrile (5 mL). The reaction mixture was further stirred

for 30 min under gentle warming and then filtered to remove the precipi-

tate of AgCl. Small dark green cubes of 3d suitable for X-ray diffraction

were obtained by slow evaporation of the filtered solution after several

days in air at room temperature. Yield: 1.7 g, 85%; IR (KBr): n˜ =1633,

1602 cm^ꢀ1(C=O); UV/Vis (CH₃CN): l_max(e)=225 (246000), 265

(69500), 400 (8200), 592 nm (735m^ꢀ1cm^ꢀ1); elemental analysis calcd (%)

for C₂₁₈H₂₂₈Cu₄N₁₂O₃₆P₈: C 63.95, H 5.61, N 4.11; found: C 63.08, H 5.68,

N 4.02.

6H; 6NH); IR (KBr): n˜ =3368, 3265 (N H), 1696, 1679 cm^ꢀ1(C=O); ele-

mental analysis calcd (%) for C₃₃H₃₄N₆O₁₀: C 58.75, H 5.04, N 12.46;

found: C 57.33, H 5.54, N 12.94.

ꢀ

Compound Na

ACHTUNGTRENNUNG

₄ACHTUNGTRENNUNG[Cu₂ACHTUNGTRENNUNG(1b)₂]·6H₂O (1c): An aqueous solution (5 mL) of

Cu(NO₃)₂·3H₂O (0.48 g, 2 mmol) was added dropwise to a solution of

H₂Et₂1b (0.64 g, 2 mmol) and NaOH (0.32 g, 8 mmol) in water (25 mL)

under stirring at room temperature. The resulting deep green solution

was then filtered, and the solvent was reduced under vacuum until a dark

green solid appeared. The solid 1c was collected by filtration, washed

with acetone and diethyl ether, and dried under vacuum. Yield: 0.8 g,

90%; IR (KBr): n˜ =1638, 1613 cm^ꢀ1(C=O); UV/Vis (H₂O): l_max(e)=230

(30800), 300 (7500), 370 (3020), 645 nm (210m^ꢀ1cm^ꢀ1); elemental analysis

calcd (%) for C₂₂H₂₄Cu₂Na₄N₄O₁₈: C 31.03, H 2.84, N 6.58; found: C

30.87, H 2.89, N 6.50.

Physical techniques: Elemental analyses (C, H, N) were performed at the

Service Central d’Analyse du CNRS in Vernaison (France). ¹H NMR

spectra were recorded at room temperature using a Bruker AC 200

(200 MHz) spectrometer. Chemical shifts are reported in d (ppm) versus

TMS with the deuterated DMSO solvent proton residuals as internal

standard. FTIR spectra were recorded using Bio-Rad FTS165 spectro-

photometers with KBr pellets. UV/Vis solution spectra were recorded at

room temperature using an Agilent Technologies 8453 spectrophotome-

ter. Variable-temperature (2.0–300 K) magnetic susceptibility under an

applied field of 1 T (Tꢃ25 K) and 250 G (T<25 K) and variable-field

(0–5.0 T) magnetization measurements at T=2.0 K were carried out on

powdered samples of 1d–3d using a SQUID magnetometer. The magnet-

ic susceptibility data were corrected for the diamagnetism of the constitu-

ent atoms and the sample holder. Cyclic voltammetry (CV) and rotating-

disk electrode (RDE) electrochemical measurements were carried out in

acetonitrile using 0.1m nBu₄NPF₆as supporting electrolyte and 1.0 mm of

1d–3d. The working electrode in the CV measurements was a glassy

carbon disk (0.32 cm²), which was polished with 1.0 mm diamond powder,

washed with absolute ethanol and acetone, and air dried. The reference

electrode was AgClO₄/Ag separated from the test solution by a salt

bridge that contained the solvent/supporting electrolyte, with platinum as

auxiliary electrode. All experiments were performed in standard electro-

chemical cells at 258C under argon. The potential range investigated was

between ꢀ2.0 and 2.0 V versus SCE. The formal potentials were mea-

sured at a scan rate of 100 mVs^ꢀ1and they were referred to the SCE.

Compound (nBu₄N)

1.0m solution of

nBu₄NOH in methanol (8.0 mL, 8.0 mmol) was added all at once to an

aqueous suspension of H₂Et₂1b (0.64 g, 2 mmol) in water (25 mL). An

aqueous solution (5 mL) of CuCl₂·2H₂O (0.34 g, 2 mmol) was then added

dropwise under stirring at room temperature to the reaction mixture. The

resulting deep green solution was extracted with dichloromethane. The

organic phase was separated from the mixture, washed twice with water,

and dried over molecular sieves. The solvent was removed under vacuum

and the green solid was recuperated with acetone, collected by filtration,

and dried under vacuum. Large dark green cubes of 1d suitable for X-

ray diffraction were obtained by recrystallization in acetonitrile after sev-

eral days of slow evaporation in air at room temperature. Yield: 1.4 g,

85%; IR (KBr): n˜ =1647, 1614 cm^ꢀ1(C=O); UV/Vis (CH₃CN): l_max(e)=

230 (28900), 300 (6000), 385 (2150), 600 nm (220m^ꢀ1cm^ꢀ1); elemental

analysis calcd (%) for C₈₆H₁₆₄Cu₂N₈O₁₆: C 61.00, H 9.76, N 6.62; found:

C 61.55, H 9.67, N 6.55.

Compound Na

ACHTUNGTRENNUNG

₆ACHTUNGTRENNUNG[Cu₃ACHTUNGTRENNUNG(2b)₂]·20H₂O (2c): An aqueous solution (5 mL) of

Cu(NO₃)₂·3H₂O (0.78 g, 3 mmol) was added dropwise to a solution of

H₄Et₂2b (1.0 g, 2 mmol) and NaOH (0.48 g, 12 mmol) in water (25 mL)

under stirring at room temperature. The resulting deep green solution

was then filtered, and the solvent was reduced under vacuum until a dark

green solid appeared. The solid 2c was collected by filtration, washed

with acetone and diethyl ether, and dried under vacuum. Yield: 1.4 g,

85%; IR (KBr): n˜ =1654, 1611 cm^ꢀ1(C=O); UV/Vis (H₂O): l_max(e)=240

(51200), 305 (17900), 375 (7180), 588 nm (440m^ꢀ1cm^ꢀ1); elemental analy-

sis calcd (%) for C₄₀H₆₄Cu₃N₈Na₆O₃₆: C 30.75, H 4.10, N 7.17; found: C

30.15, H 4.00, N 7.04.

Crystal-structure data collection and refinement: The X-ray diffraction

data of 1d–3d were collected at 100(2) K with synchrotron radiation (l=

0.7380 (1d) and 0.7513 ꢊ (2d and 3d)) at the BM16-CRG beamline in

the ESRF (Grenoble, France). The data for 1d–3d were indexed, inte-

grated, and scaled using the HKL2000 program.^[29]All calculations for

data reduction, structure solution, and refinement were done by standard

procedures (WINGX).^[30]The structures of 1d–3d were solved by direct

Compound (EtPh₃P)

₆ACHTUNGTRENNUNG[Cu₃CAHTUNTGERN(NGUN 2b)₂]·26.7H₂O (2d): An aqueous solution

(10 mL) of AgNO₃(0.50 g, 3 mmol) was added to a solution of 2c

Chem. Eur. J. 2010, 16, 12838 – 12851

ꢉ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

12849

F. Lloret, Y. Journaux et al.

methods and refined with full-matrix least-squares technique on F²using

the SHELXS-97 and SHELXL-97 programs.^[31]Some disorder was found

for one of the two crystallographically independent tetra-n-butylammoni-

um cations in 1d, for which two positions were refined anisotropically

using the partition (PART) instruction with occupation factors of 0.648

and 0.352 (equal anisotropic displacement parameter (EADP) instruc-

tions were used between identical atoms in the two positions to reduce

the number of parameters). In 2d, residual electronic density was as-

[8] a) L. K. Thompson, Coord. Chem. Rev. 2002 , 233–234 , 193; b) L. N.

Dawe, T. S. M. Abedin, L. K. Thompson, Dalton Trans. 2008 , 1661.

[9] a) J. M. Lehn, Angew. Chem. 2004, 116, 3728; Angew. Chem. Int. Ed.

2004, 43, 3644; b) M. Ruben, J. M. Lehn, P. Mꢌller, Chem. Soc. Rev.

2006 , 35 , 1056.

[10] a) O. Kahn, Molecular Magnetism, VCH, Weinheim, 1993; b) Molec-

ular Magnetism: From Molecular Assemblies to the Devices, Vol. 321

(Eds.: E. Coronado, P. Delhaꢆs, D. Gatteschi, J. S. Miller), NATO

ASI Ser. E, Kluwer, 1995; c) Molecular Electronics (Eds.: J. Jorner,

M. Ratner), Blackwell, Oxford, 1997; d) Molecular Electronics: Sci-

ence and Technology (Eds.: A. Aviram, M. Ratner), New York

Academy of Sciences, New York, 1998.

signed to not-fully-occupied positions for OACHTUNGTREN(UNNG 13w), OACHNUTRTGEG(NNUN 14w), and OACHTNGUTREN(NUGN 15w)

atoms from crystallization water molecules (site of occupation (s.o.f.) was

refined and, once converged, it was fixed to that value for subsequent re-

finements). The hydrogen atoms from the organic ligands were calculated

and refined with isotropic thermal parameters, whereas those from the

water molecules were neither found nor calculated. The final geometrical

calculations and the graphical manipulations were carried out with

PARST97 and CRYSTAL MAKER programs, respectively.^[32]

[11] a) C. Piguet, G. Bernardinelli, G. Hopfgartner, Chem. Rev. 1997 , 97 ,

2005; b) M. Albrecht, Chem. Eur. J. 2000 , 6 , 3485.

[12] J. M. Lehn, A. Rigault, J. Siegel, J. Harrowfield, B. Chevrier, D.

Moras, Proc. Natl. Acad. Sci. USA 1987 , 84 , 2565.

[13] a) K. T. Potts, M. K. Keshavarz, F. S. Tham, K. A. G. Raiford, C.

Arana, H. D. AbruÇa, Inorg. Chem. 1993 , 32 , 5477; b) L. Zelikovich,

J. Libman, A. Shanzer, Nature 1995 , 374 , 790; c) P. K. K. Ho, S. M.

Peng, K. Y. Wong, C. M. Che, J. Chem. Soc. Dalton Trans. 1996 ,

1829; d) M. Greenwald, M. Easa, E. Katz, I. Willner, Y. Cohen, J.

Electroanal. Chem. 1997 , 434 , 77; e) R. W. Saalfrank, A. Dresel, V.

Seitz, S. Trummer, F. Hampel, M. Teichert, D. Stalke, C. Stadler, J.

Daub, V. Schꢌnemann, A. X. Trautwein, Chem. Eur. J. 1997 , 3 , 2058;

f) L. J. Charbonniꢆre, A. F. Williams, C. Piguet, G. Bernardelli, E.

Rivara-Minten, Chem. Eur. J. 1998, 4, 485; g) A. El-Ghayouy, A.

Harriman, A. De Cian, J. Fischer, R. Ziessel, J. Am. Chem. Soc.

1998 , 120 , 9973; h) M. R. Bermejo, M. Fondo, A. M. Gonzales, O. L.

Hoyos, A. Sousa, C. A. McAuliffe, W. Hussain, R. Pritchard, V. M.

Novotorsev, J. Chem. Soc. Dalton Trans. 1999 , 2211; i) K. T. Potts,

M. P. Wentland, D. Canguly, G. D. Storrier, S. K. Cha, J. Cha, H. D.

AbruÇa, Inorg. Chim. Acta 1999 , 288 , 189.

[14] a) M. Vꢈzquez, M. R. Bermejo, M. Fondo, A. M. Gonzꢈlez, J. Lahꢄa,

L. Sorace, D. Gatteschi, Eur. J. Inorg. Chem. 2001, 1863; b) G.

Aromꢄ, P. C. Berzal, P. Gamez, O. Roubeau, H. Kooijman, A. L.

Spek, W. L. Driessen, J. Reedijk, Angew. Chem. 2001, 113, 3552;

Angew. Chem. Int. Ed. 2001, 40, 3444; c) G. Aromꢄ, P. Gamez, O.

Roubeau, P. C. Berzal, H. Kooijman, A. L. Spek, W. L. Driessen, J.

Reedijk, Inorg. Chem. 2002, 41, 3673; d) R. Krꢍmer, I. O. Fritsky, H.

Pritzkow, L. A. Kovbasyuk, J. Chem. Soc. Dalton Trans. 2002 , 1307;

e) A. Dei, D. Gatteschi, C. Sangregorio, L. Sorace, M. G. F. Vaz,

Inorg. Chem. 2003 , 42 , 1701; f) S. Mukherjee, E. Rentschler, T. Wey-

hermꢌller, K. Wieghardt, P. Chaudhuri, Chem. Commun. 2003 ,

1828; g) M. Vꢈzquez, A. Taglietti, D. Gatteschi, L. Sorace, C. San-

gregorio, A. M. Gonzꢈlez, M. Maneiro, R. M. Pedrido, M. R. Ber-

mejo, Chem. Commun. 2003, 1840; h) S. Mukherjee, T. Weyhermꢌl-

ler, E. Bothe, K. Wieghardt, P. Chaudhuri, Dalton Trans. 2004 , 3842;

i) F. Tuna, M. R. Lees, G. J. Clarkson, M. J. Hannon, Chem. Eur. J.

2004 , 10 , 5737; j) A. R. Paital, T. Mitra, D. Ray, W. T. Wong, J.

Ribas-AriÇo, J. J. Novoa, J. Ribas, G. Aromꢄ, Chem. Commun. 2005 ,

5172; k) G. Aromi, H. Stoeckli-Evans, S. J. Teat, J. Cano, J. Ribas, J.

Mater. Chem. 2006 , 16 , 2635; l) M. A. Palacios, A. Rodrꢄguez-Diꢃ-

guez, A. Sironi, J. M. Herrera, A. J. Mota, J. Cano, E. Colacio,

Dalton Trans. 2009 , 8538; m) M. A. Palacios, A. Rodrꢄguez-Diꢃguez,

A. Sironi, J. M. Herrera, A. J. Mota, V. Moreno, J. Cano, E. Colacio,

New J. Chem. 2009 , 33 , 1901; n) L. A. Barrios, D. Aguilꢅ, O. Rou-

beau, P. Gamez, J. Ribas-AriÇo, S. J. Teat, G. Aromi, Chem. Eur. J.

2009 , 15 , 11235.

CCDC-777548 (1d), 777549 (2d), and 777550 (3d) contain the supple-

mentary crystallographic data for this paper. These data can be obtained

free of charge from The Cambridge Crystallographic Data Centre via

www.ccdc.cam.ac.uk/data_request/cif.

Computational methods: The molecular geometries of the model com-

plexes for 1d–3d were not optimized and their bond lengths and inter-

bond angles were taken from the actual crystal structures. The energy for

all possible symmetrically independent spin distributions were evaluated.

These spin distributions are a high-spin M_S=1 and a M_S=0 ({1}) state

for 1d, a high-spin M_S=³= and two M_S=¹= ({1} and {2}) states for 2d,

and a high-spin M_S=2, two M_S=1 ({1} and {2}), and three M_S=0 ({1,2},

({1,3}, and {1,4}) for 3d (in this representation, only the center with a

spin-down is noted). Electronic structure calculations were carried out

with the hybrid density functional B3LYP method^[33]combined with the

broken-symmetry (BS) approach^[34]as implemented in the GAUSSI-

AN 03 program^[35]using the triple-z (TZV) quality basis sets proposed by

Ahlrichs and co-workers.^[36]The electronic density data were obtained

using natural bond orbital (NBO) analysis.^[37]

Acknowledgements

This work was supported by the MICINN (Spain) (projects CTQ2007-

61690, MAT2007-60660, CSD2007-00010, and CSD2006-00015), the Gen-

eralitat Valenciana (Spain) (Project PROMETEO/2009/108), the Gobier-

no Autꢇnomo de Canarias (Spain) (Project PI2002/175), the MESR and

the CNRS (France). E.P. acknowledges the MICINN for a postdoctoral

(“Juan de la Cierva”) grant. J.F.-S. and M.-C. Dul thank the Generalitat

Valenciana and the MESR respectively, for predoctoral grants.

[1] a) J. M. Lehn, Supramolecular Chemistry: Concepts and Perspectives,

VCH, Weinheim, 1995; b) Transition Metals in Supramolecular

Chemistry, Vol. 5 (Ed.: J. P. Sauvage), Wiley, New York, 1999.

[2] a) S. Leininger, B. Olenyuk, P. J. Stang, Chem. Rev. 2000 , 100 , 853;

b) G. F. Swiegers, T. J. Malefetse, Chem. Rev. 2000 , 100 , 3483; c) P. J.

Steel, Acc. Chem. Res. 2005 , 38 , 243.

[3] a) P. J. Stang, B. Olenyuk, Acc. Chem. Res. 1997 , 30 , 502; b) S. R.

Seidel, P. J. Stang, Acc. Chem. Res. 2002 , 35 , 972.

[15] a) J. K. Bera, K. R. Dunbar, Angew. Chem. 2002 , 114 , 4633; Angew.

Chem. Int. Ed. 2002 , 41 , 4453; b) S. Y. Lin, I. W. P. Chen, C. H.

Chen, M. H. Hsieh, C. Y. Yeh, T. W. Lin, Y. H. Chen, S. M. Peng, J.

Phys. Chem. B 2004 , 108 , 959; c) I. P. C. Liu, W. Z. Wang, S. M.

Peng, Dalton Trans. 2009, 4323.

[16] a) R. Clꢃrac, F. A. Cotton, L. M. Daniels, K. R. Dunbar, C. A. Mu-

rillo, I. Pascual, Inorg. Chem. 2000, 39, 752; b) J. F. Berry, F. A.

Cotton, L. M. Daniels, C. A. Murillo, J. Am. Chem. Soc. 2002 , 124 ,

3212; c) J. F. Berry, F. A. Cotton, L. M. Daniels, C. A. Murillo, X.

Wang, Inorg. Chem. 2003 , 42 , 2418; d) J. F. Berry, F. A. Cotton, T.

Lu, C. A. Murillo, B. K. Roberts, X. Wang, J. Am. Chem. Soc. 2004 ,

[4] a) M. Albrecht, Chem. Soc. Rev. 1998 , 27 , 281; b) M. Albrecht, I.

Janser, R. Frçhlich, Chem. Commun. 2005 , 157.

[5] a) M. Fujita, Acc. Chem. Res. 1999 , 32 , 53; b) M. Fujita, M. Tomina-

ga, A. Hori, B. Therrien, Acc. Chem. Res. 2005 , 38 , 369.

[6] a) D. L. Caulder, K. N Raymond, Acc. Chem. Res. 1999 , 32 , 975;

b) D. Fiedler, D. H. Leung, R. G. Bergman, K. N. Raymond, Acc.

Chem. Res. 2005 , 38 , 349.

[7] a) R. Ruiz, J. Faus, F. Lloret, M. Julve, Y. Journaux, Coord. Chem.

Rev. 1999 , 193–195 , 1069; b) E. Pardo, R. Ruiz-Garcꢄa, J. Cano, X.

Ottenwaelder, R. Lescouꢂzec, Y. Journaux, F. Lloret, M. Julve,

Dalton Trans. 2008 , 2780.

12850

www.chemeurj.org

ꢉ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Chem. Eur. J. 2010, 16, 12838 – 12851

Copper(II) Mesocates

FULL PAPER

126 , 7082; e) C. K. Kuo, J. C. Chang, C. Y. Yeh, G. H. Lee, C. C.

Wang, S. M. Peng, Dalton Trans. 2005 , 3696; f) B. Bꢃnard, J. F.

Berry, F. A. Cotton, C. Gaudin, X. Lꢇpez, C. A. Murillo, M. M.

Rohmer, Inorg. Chem. 2006, 45, 3932; g) G. C. Huang, M. Bꢃnard,

M. M. Rohmer, L. A. Li, M. J. Chiu, C. Y. Yeh, G. H. Lee, S. M.

Peng, Eur. J. Inorg. Chem. 2008 , 1767; h) F. A. Cotton, C. A. Muril-

lo, Q. Wang, M. D. Young, Eur. J. Inorg. Chem. 2008 , 5257; i) X.

Lꢇpez, M. M. Rohmer, M. Bꢃnard, J. Mol. Struct. 2008, 890, 18;

j) I. P. C. Liu, C. H. Chen, C. F. Chen, G. H. Lee, S. M. Peng, Chem.

Commun. 2009 , 577; k) Z. Tabookht, X. Lꢇpez, C. De Graaf, J.

Phys. Chem. B 2010, 114, 2028.

[25] a) I. Fernꢈndez, R. Ruiz, J. Faus, M. Julve, F. Lloret, J. Cano, X. Ot-

tenwaelder, Y. Journaux, M. C. MuÇoz, Angew. Chem. 2001, 113,

3129; Angew. Chem. Int. Ed. 2001, 40, 3039; b) E. Pardo, J. Faus, M.

Julve, F. Lloret, M. C. MuÇoz, J. Cano, X. Ottenwaelder, Y. Jour-

naux, R. Carrasco, G. Blay, I. Fernꢈndez, R. Ruiz-Garcꢄa, J. Am.

Chem. Soc. 2003 , 125 , 10770; c) E. Pardo, R. Carrasco, R. Ruiz-

Garcꢄa, M. Julve, F. Lloret, M. C. MuÇoz, Y. Journaux, E. Ruiz, J.

Cano, J. Am. Chem. Soc. 2008 , 130 , 576; d) M. C. Dul, E. Pardo, R.

Lezcouꢂzec, L. M. Chamoreau, F. Villain, Y. Journaux, R. Ruiz-

Garcꢄa, J. Cano, M. Julve, F. Lloret, J. Pasꢈn, C. Ruiz-Pꢃrez, J. Am.

Chem. Soc. 2009 , 131 , 14614; e) M. C. Dul, X. Ottenwaelder, E.

Pardo, R. Lezcouꢂzec, Y. Journaux, L. M. Chamoreau, R. Ruiz-

Garcꢄa, J. Cano, M. Julve, F. Lloret, Inorg. Chem. 2009 , 48 , 5244.

[26] a) J. Ferrando-Soria, M. Castellano, C. Yuste, F. Lloret, M. Julve, O.

Fabelo, C. Ruiz-Pꢃrez, S.-E. Stiriba, R. Ruiz-Garcꢄa, J. Cano, Inorg.

Chim. Acta 2010 , 363 , 1666; b) C. Yuste, J. Ferrando-Soria, D. Can-

gussu, O. Fabelo, C. Ruiz-Pꢃrez, N. Marino, G. De Munno, S.-E. Stir-

iba, R. Ruiz-Garcꢄa, J. Cano, F. Lloret, M. Julve, Inorg. Chim. Acta

2010 , 363 , 1984.

[27] a) Y. Journaux, J. Sletten, O. Kahn, Inorg. Chem. 1986 , 25 , 439;

b) J. L. Sanz, B. Cervera, R. Ruiz, C. Bois, J. Faus, F. Lloret, M.

Julve, J. Chem. Soc. Dalton Trans. 1996 , 1359.

[28] a) G. V. Rubenacker, J. E. Drumheller, K. Emerson, R. D. Willet, J.

Magn. Magn. Mater. 1986 , 54–57 , 1483; b) R. Ruiz, F. Lloret, M.

Julve, J. Faus, M. C. MuÇoz, X. Solans, Inorg. Chim. Acta 1998 , 268 ,

263.

[29] Z. Otwinowski, W. Minor, Processing of X-ray Diffraction Data Col-

lected in Oscillation Mode in Methods in Enzymology: Macromolec-

ular Crystallography, Part A, Vol. 276 (Eds.: C. W. Carter, Jr., R. M.

Sweet), Academic Press, New York, 1997, p. 307.

[30] WINGX: L. J. Farrugia, J. Appl. Crystallogr. 1999 , 32 , 837.

[31] SHELX97, Programs for Crystal Structure Analysis, release 97–2,

G. M. Sheldrick, Institꢌt fꢌr Anorganische Chemie der Universitꢍt

Gçttingen, Gçttingen, 1998.

[17] a) F. A. Cotton, L. M. Daniels, C. A. Murillo, X. Wang, Chem.

Commun. 1998, 39; b) S. Y. Lai, T. W. Lin, Y. H. Chen, C. C. Wang,

G. H. Lee, M. H. Yang, M. K. Leung, S. M. Peng, J. Am. Chem. Soc.

1999 , 121 , 250.

[18] a) S. J. Shieh, C. C. Chou, G. H. Lee, C. C. Wang, S. M. Peng,

Angew. Chem. 1997 , 109 , 57; Angew. Chem. Int. Ed. Engl. 1997 , 36 ,

56; b) H. C. Chang, J. T. Li, C. C. Wang, T. W. Lin, H. C. Lee, G. H.

Lee, S. M. Peng, Eur. J. Inorg. Chem. 1999 , 1243; c) C. Y. Yeh, Y. L.

Chiang, G. H. Lee, S. M. Peng, Inorg. Chem. 2002 , 41 , 4096; d) C. Y.

Yeh, C. H. Chou, K. C. Pan, C. C. Wang, G. H. Lee, Y. O. Su, S. M.

Peng, J. Chem. Soc. Dalton Trans. 2002 , 2670; e) J. F. Berry, F. A.

Cotton, P. Lei, T. Lu, C. A. Murillo, Inorg. Chem. 2003 , 42 , 3534;

f) J. F. Berry, F. A. Cotton, C. S. Fewox, T. Lu, C. A. Murillo, X.

Wang, Dalton Trans. 2004 , 2297; g) W. Z. Wang, R. H. Ismayilov,

R. R. Wang, Y. L. Huang, C. Y. Yeh, G. H. Lee, S. M. Peng, Dalton

Trans. 2008 , 6808; h) C. X. Yin, J. Su, F. J. Huo, R. H. Ismayilov,

W. Z. Wang, G. H. Lee, C. Y. Yeh, S. M. Peng, J. Coord. Chem. 2009 ,

62 , 2974; i) C. X. Yin, F. J. Huo, W. Z. Wang, R. H. Ismayilov, G. H.

Lee, C. Y. Yeh, S. M. Peng, P. Yang, Chin. J. Chem. 2009 , 27 , 1295.

[19] a) C. H. Chien, J. C. Chang, C. Y. Yeh, G. H. Lee, J. M. Fang, S. M.

Peng, Dalton Trans. 2006 , 2106; b) C. H. Chien, J. C. Chang, C. Y.

Yeh, J. M. Fang, Y. Song, S. M. Peng, Dalton Trans. 2006 , 3249;

c) I. P. C. Liu, C. F. Chen, S. A. Hua, C. H. Chen, H. T. Wang, G. H.

Lee, S. M. Peng, Dalton Trans. 2009 , 3571.

[20] a) Y. H. Chen, C. C. Lee, C. C. Wang, G. H. Lee, S. Y. Lai, S. M.

Peng, Chem. Commun. 1999 , 1667; b) S. Y. Lai, C. C. Wang, Y. H.

Chen, C. C. Lee, Y. H. Liu, S. M. Peng, J. Chin. Chem. Soc. 1999, 46,

477; c) R. H. Ismayilov, W. Z. Wang, G. H. Lee, C. H. Chien, C. H.

Jiang, C. L. Chiu, C. Y. Yeh, S. M. Peng, Eur. J. Inorg. Chem. 2009 ,

2110.

[21] a) S. M. Peng, C. C. Wang, Y. L. Jang, Y. H. Chen, F. Y. Li, C. Y.

Mou, M. K. Leung, J. Magn. Magn. Mater. 2000 , 209 , 80; b) R. H. Is-

mayilov, W. Z. Wang, R. R. Wang, C. Y. Yeh, G. H. Lee, S. M. Peng,

Chem. Commun. 2007 , 1121; c) R. H. Ismayilov, W. Z. Wang, R. R.

Wang, Y. L. Huang, C. Y. Yeh, G. H. Lee, S. M. Peng, Eur. J. Inorg.

Chem. 2008 , 4290.

[32] a) M. Nardelli, J. Appl. Crystallogr. 1995 , 28 , 659; b) CRYSTAL

MAKE, D. Palmer, Cambridge University Technical Services, Cam-

bridge, 1996.

[33] A. D. Becke, J. Chem. Phys. 1993 , 98 , 5648.

[34] a) E. Ruiz, J. Cano, S. Alvarez, P. Alemany, J. Am. Chem. Soc. 1998 ,

120 , 11122; b) E. Ruiz, J. Cano, S. Alvarez, P. Alemany, J. Comput.

Chem. 1999 , 20 , 1391; c) E. Ruiz, A. Rodriguez-Fortea, J. Cano, S.

Alvarez, P. Alemany, J. Comput. Chem. 2003 , 24 , 982; d) E. Ruiz, V.

Polo, J. Cano, S. Alvarez, J. Chem. Phys. 2005 , 123 , 164110.

[35] Gaussian 03, Revision C.02, M. J. Frisch, G. W. Trucks, H. B. Schle-

gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. J. A. Montgom-

ery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S.

Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani,

N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.

Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,

O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,

J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E.

Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W.

Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J.

Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C.

Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari,

J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cio-

slowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaro-

mi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng,

A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W.

Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian, Inc., Wall-

ingford CT, 2004.

[22] a) C. J. Matthews, S. J. Onions, G. Morata, L. J. Davis, S. L. Heath,

D. J. Price, Angew. Chem. 2003 , 115 , 3274; Angew. Chem. Int. Ed.

2003 , 42 , 3166; b) V. Maurizot, G. Linti, I. Huc, Chem. Commun.

2004, 920.

[23] a) R. Ruiz, C. Surville-Barland, A. Aukauloo, E. Anxolabꢆhere-Mal-

lart, Y. Journaux, J. Cano, M. C. MuÇoz, J. Chem. Soc. Dalton Trans.

1997 , 745; b) B. Cervera, J. L. Sanz, M. J. IbaÇez, G. Vila, F. Lloret,

M. Julve, R. Ruiz, X. Ottenwaelder, A. Aukauloo, S. Poussereau, Y.

Journaux, M. C. MuÇoz, J. Chem. Soc. Dalton Trans. 1998 , 781; c) X.

Ottenwaelder, R. Ruiz-Garcꢄa, G. Blondin, R. Carrasco, J. Cano, D.

Lexa, Y. Journaux, A. Aukauloo, Chem. Commun. 2004 , 504; d) X.

Ottenwaelder, A. Aukauloo, Y. Journaux, R. Carrasco, J. Cano, B.

Cervera, I. Castro, S. Curreli, M. C. MuÇoz, A. L. Rosellꢇ, B. Soto,

R. Ruiz-Garcꢄa, J. Chem. Soc. Dalton Trans. 2005, 2516; e) R. Carra-

sco, J. Cano, X. Ottenwaelder, A. Aukauloo, Y. Journaux, R. Ruiz-

Garcꢄa, Dalton Trans. 2005 , 2527.

[24] a) A. Aukauloo, X. Ottenwaelder, R. Ruiz, Y. Journaux, Y. Pei, E.

Riviꢆre, B. Cervera, M. C. MuÇoz, Eur. J. Inorg. Chem. 1999 , 209;

b) A. Aukauloo, X. Ottenwaelder, R. Ruiz, S. Poussereau, Y. Pei, Y.

Journaux, P. Fleurat, F. Volatron, B. Cervera, M. C. MuÇoz, Eur. J.

Inorg. Chem. 1999 , 1067.

[36] a) A. Schꢍfer, H. Horn, R. Ahlrichs, J. Chem. Phys. 1992, 97, 2571;

b) A. Schꢍfer, C. Huber, R. Ahlrichs, J. Chem. Phys. 1994, 100, 5829.

[37] a) J. E. Carpenter, F. Weinhold, J. Mol. Struct. 1988, 172–191, 41;

b) A. E. Reed, L. A. Curtis, F. Weinhold, Chem. Rev. 1988 , 88 , 899;

c) F. Weinhold, J. E. Carpenter, The Structure of Small Molecules

and Ions, Plenum, New York, 1988, p. 227.

Received: June 18, 2010

Published online: October 22, 2010

Chem. Eur. J. 2010, 16, 12838 – 12851

ꢉ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemeurj.org

12851

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