Magnetic and structural properties of dinuclear singly bridged-phenoxido metal(II) complexes

Article abstract of DOI:10.1039/c4dt03508a

The reaction of a methanolic solution containing the bi-compartmental phenolic ligand 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-chlorophenol (L^Cl-OH) with MCl₂·nH₂O in the presence of NH₄PF₆ or NaClO₄ afforded the dinuclear bridged-phenoxido dichlorido-metal(ii) complexes [Co₂(μ-L^ClO)(H₂O)₂Cl₂][Co₂(μ-L^ClO)(MeOH)₂Cl₂](PF₆)₂ (1), [Ni₂(μ-L^ClO)(MeOH)₂Cl₂]PF₆ (2), [Ni₂(μ-L^ClO)(MeOH)(H₂O)Cl₂]ClO₄·1.25H₂O (3), [Cu₂(μ-L^ClO)Cl₂]PF₆·1/2MeOH (4) and [Zn₂(μ-L^ClO)Cl₂]PF₆·MeOH (5). The complexes were characterized by elemental microanalyses, conductivity measurements, IR and UV-Vis spectroscopy, mass spectrometry and single crystal X-ray crystallography. Each M(ii) center within the dinuclear complex cations is octahedrally coordinated in complexes 1-3, and five-coordinated distorted square pyramidal in 4 and 5. Magnetic susceptibility measurements at variable temperature of the complexes 1-4 revealed weak to moderate antiferromagnetic coupling with |J| values = 8.38, 39.0, 30.2 and 0.79 cm^-1, respectively. The results of DFT calculations correlate well with the experimentally determined antiferromagnetic coupling and show that the magnetic exchange coupling occurs mainly through the phenoxido bridge M-O-M. Implications of geometry around the central metal ion, M...M distance, M-O-M bond angle and overlapping of magnetic orbitals on the magnetic exchange coupling are discussed.

Full text of DOI:10.1039/c4dt03508a

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Graphical Abstract
Magnetic and Structural Properties of Dinuclear Singly Bridged-Phenoxido
Metal(II) Complexes†
Salah S. Massoud,*a Mark Spell,a,‡ Catherine C. Ledet,a Thomas Junk,a Radovan Herchel,b Roland
C. Fischer,c Zdeněk Trávníček,*b Franz A. Mautner,*d
a Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA 70504, U.S.A.
bDepartment of Inorganic Chemistry & Regional Centre of Advanced Technologies and Materials, Faculty of
Science, Palacký University, 17. listopadu 12, CZ-77146 Olomouc, Czech Republic
cInstitut für Anorganische Chemische, Technische Universität Graz, Stremayrgasse 9/V, A-8010 Graz, Austria
d Institut für Physikalische and Theoretische Chemie, Technische Universität Graz, Stremayrgasse 9/II, A-8010,
Graz, Austria
Received:
Accepted:
Keywords:
Dinuclear complexes / Bridged phenolate / Crystal structures /Magnetic properties /
DFT calculations
Five new dinuclear bridged-phenoxido dichlorido-metal(II) complexes [M2(µ-LClO)(X)2Cl2]PF6/ClO4
complexes, where M(II) = Co, Ni, Cu (1-4) and Zn (5); X = CH3OH, H2O or 0 were synthesized and
structurally characterized by spectroscopic techniques and X-Ray single crystal crystallography. The
complexes 1-4 revealed weak to moderate antiferromagneic coupling.
______________________
* To whom correspondence should be addressed. E-mail: ssmassoud@louisiana.edu,Tel. +01 337-482-5672,
Fax: +01 337-482-5676 (S. S. Massoud); E-mail: zdenek.travnicek@upol.cz, Tel. +420 585-634-352, Fax:
+420 585-634-954 (Z. Trávníček); E-mail: mautner@ptc.tu-graz.ac.at, Tel. ++43 316-4873-8234, fax: ++43
316-4873-8225 (F.A. Mautner).

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Graphical Abstract (Pictogram)

Page 3 of 32
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DOI: 10.1039/C4DT03508A
Magnetic and Structural Properties of Dinuclear Singly
Bridged-Phenoxido Metal(II) Complexes†
Salah S. Massoud,*a Mark Spell,a,‡ Catherine C. Ledet,a Thomas Junk,a Radovan
Herchel,b Roland C. Fischer,c Zdeněk Trávníček,*b Franz A. Mautner,*d
a Department of Chemistry, University of Louisiana at Lafayette, Lafayette, LA 70504, U.S.A.
bDepartment of Inorganic Chemistry & Regional Centre of Advanced Technologies and
Materials, Faculty of Science, Palacký University, 17. listopadu 12, CZꢀ77146 Olomouc, Czech
Republic
cInstitut für Anorganische Chemische, Technische Universität Graz, Stremayrgasse 9/V, Aꢀ8010
Graz, Austria
d Institut für Physikalische and Theoretische Chemie, Technische Universität Graz, Stremayrgasse
9/II, Aꢀ8010, Graz, Austria
Received:
Accepted:
Keywords:
Dinuclear complexes / Bridged phenolate / Crystal structures /Magnetic properties /
DFT calculations
†
Electronic supplementary information (ESI) available: The mass spectra of the complexes 1 – 5
are shown in Figures S1ꢀS5, respectively. Packing plots for crystal structures of compounds 1 – 5
are presented in Figures S6 – S10 and the corresponding selected bond parameters are
summarized in Tables S1 – S5, respectively. Figures S11 and S12 represent the formation of the
supramolecular tetramer of complex 1 and magnetic data for complex 3. CCDC 1034090,
1034091, 1034092, 1034093 and 1034094 contain the crystallographic data for complexes 1 – 5,
respectively. These data can be obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif. For ESI and crystallographic data or other
electronic format see DOI: ?????????????????
________________________
* To whom correspondence should be addressed. Eꢀmail: ssmassoud@louisiana.edu,Tel. +01 337ꢀ482ꢀ
5672, Fax: +01 337ꢀ482ꢀ5676 (S. S. Massoud); Eꢀmail: zdenek.travnicek@upol.cz, Tel. +420 585ꢀ634ꢀ352,
Fax: +420 585ꢀ634ꢀ954 (Z. Trávníček); Eꢀmail: mautner@ptc.tuꢀgraz.ac.at, Tel. ++43 316ꢀ4873ꢀ8234, fax:
++43 316ꢀ4873ꢀ8225 (F.A. Mautner).
‡ Present address: Department of Chemistry, Louisiana State University, Choppin Hall, Baton Rouge LA,
70803, U.S.A.

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Abstract
The reaction of a methanolic solution containing the biꢀcompartmental phenolic ligand 2,6ꢀ
bis[bis(2ꢀpyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenol (LClꢀOH) with MCl2·nH2O in the presence
of NH4PF6 or NaClO4 afforded the dinuclear bridgedꢀphenoxido dichloridoꢀmetal(II) complexes
[Co2(µꢀLClO)(H2O)2Cl2][Co2(µꢀLClO)(MeOH)2Cl2](PF6)2 (1), [Ni2(µꢀLClO)(MeOH)2Cl2]PF6 (2),
[Ni2(µꢀLClO)(MeOH)(H2O)Cl2]ClO4·1.25H2O (3), [Cu2(µꢀLClO)Cl2]PF6·½MeOH (4) and [Zn2(µꢀ
LClO)Cl2]PF6·MeOH (5). The complexes were characterized by elemental microanalyses,
conductivity measurements, IR and UVꢀVis spectroscopy, mass spectrometry and single crystal Xꢀ
ray crystallography. Each M(II) center within the dinuclear complex cations is octahedrally
coordinated in complexes 1–3, and fiveꢀcoordinated distorted square pyramidal in 4 and 5.
Magnetic susceptibility measurements at variable temperature of the complexes 1–4 revealed weak
to moderate antiferromagnetic coupling with ǀJǀ values = 8.38, 39.0, 30.2 and 0.79 cmꢀ1,
respectively. The results of DFT calculations correlate well with the experimentally determined
antiferromagnetic coupling and show that the magnetic exchange coupling occurs mainly through
the phenoxido bridge M–O–M. Implications of geometry around the central metal ion, M···M
distance, M–O–M bond angle and overlapping of magnetic orbitals on the magnetic exchange
coupling are discussed.
+
Cl
X = H2O, CH3OH, 0
M = Co, Ni, Cu, Zn
Cl
Cl
M
O
N
N
M
X
X
N
N
N
N
2

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Introduction
The design of compartmental ligands capable of providing symmetrical and asymmetrical
bimetallic cores is a growing topic. The metal complexes constructed from these ligands have
been used as successful devices to mimic the active sites of a variety metalloenzymes.1ꢀ13 With
focus on compartmental ligands that are derived from phenolic containing compounds, these
ligands have been launched to study the phosphodiester hydrolysis and DNA cleavage1ꢀ4 and to
model purple acid phosphatases,5,6 Zn phosphesterases,7,8 Mn catalases,9 catecholase oxidases,10,11
metalloꢀβꢀlactamases (MβL)12 and hemocyanin.13 The use of these model compounds was very
helpful to gain insight into biological systems and to elucidate some structural features about these
systems. Recently, it has been reported that heteronuclear transition metalꢀlanthanide, 3dꢀ4f metal
complexes derived from multidentate Schiff bases containing phenolic and alkoxy groups have the
capability of fixing atmospheric CO2 to produce carbonatoꢀbridged polynuclear compounds.14ꢀ18
The resulting carbonatoꢀbridged complexes showed interesting magnetic properties that open
possibilities for their use as magnetic devices for single molecule magnets (SMM).14ꢀ18
Among many different types of binucleating compounds are phenolꢀbased compartmental
ligands, which possess two pendant chelating arms attached to the 2ꢀ and 6ꢀpositions of the phenol
ring. These two arms, which can be symmetric or asymmetric, can accommodate two similar or
dissimilar metal ions and hence produce dinuclear metal complexes bridged by the endogeneous
deprotonated phenolic group and one or two exogeneous groups leading to unsaturated
coordination environment around the central metal ions, or in some cases coordinate to weakly
bound ligand(s).1ꢀ13,19ꢀ51 The distance between the two metal ions bridged via the phenoxido group
is a crucial parameter in mediating the magnetic interaction between the two paramagnetic metallic
centers. Also, their close proximity allows the cooperation between metal ions, where the distance
between the two bridged metal ions are within the range of 2.9ꢀ4.0 Ǻ, providing an excellent
pathway for a strong antiferromagnetic coupling between 3d7ꢀ9 centers. In addition, the benzene
ring present in these systems allows great synthetic flexibility, especially in tuning the solubility of
the compounds.
As it was indicated above, the phenolꢀbased compounds with 2,6ꢀpendant chelating
coordinating arms have the tendency to bind two similar or dissimilar metal ions through the
deprotonated phenolic group. In the presence of aliphatic and aromatic carboxylate compounds
extra bridge(s) via the carboxylate moiety may be obtained.35ꢀ43 Similarly, bridged hydroxoꢀ,
methoxoꢀ and phosphoꢀester compounds were also observed.22,44ꢀ48 However, it came to our
attention that a few examples exist in literature for dinuclear bridgedꢀphenoxido complexes with
3

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the formulas [M2(LRO)Cl2]Y and [M2(LMeO)(X)2]Y3, where X = H2O and CH3CN; Y = ClO4 , PF6
ꢀ
ꢀ
or BF4 and LROH = binucleating phenol.34,52ꢀ54 Therefore, this study was undertaken to explore
ꢀ
the
coordination
properties
of
this
class
of
compounds
using
bis[bis(2ꢀ
pyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenol (LClꢀOH) (Chart 1) with Co(II), Ni(II), Cu(II) and
Zn(II) metal ions.
Chart 1. Structure formulas of bis[bis(2ꢀpyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenol (LClꢀOH)
and related compounds
R
R
H3CO
OCH3
n
n
N
OH
N
N
N
N
OH
N
N
N
N
N
R = Cl, n = 1, LCl-OH
R = CH3, n = 1, LMe-OH
R = CH3, n = 2, L`Me-OH
R = Br, L1Br-OH
R = NO2,L1NO2-OH
Results and discussion
Syntheses
The biꢀcompartmental phenolic ligand 2,6ꢀbis[bis(2ꢀpyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenol
(LClꢀOH) was synthesized in about 80% by the reaction of 2,6ꢀbis(2ꢀchloromethyl)ꢀ4ꢀ
chlorophenol with bis(2ꢀpyridylmethyl)amine (DPA) in anhydrous CH3CN and in the presence of
a slight excess of anhydrous K2CO3. The compound 2,6ꢀbis(2ꢀchloromethyl)ꢀ4ꢀchlorophenol was
obtained through the hydroxoformylation of 4ꢀchlorophenol by 30% aqueous solution of
formaldehyde in aqueous NaOH solution followed by acidification with acetic acid (pH < 6) to
produce 2,6ꢀbis(2ꢀhydroxomethyl)ꢀ4ꢀchlorophenol. The later compound was then converted to the
corresponding 2,6ꢀbis(2ꢀchloromethyl)ꢀ4ꢀchlorophenol via the reaction with concentrated
1
13
hydrochloric acid. The ligand LClꢀOH (Chart 1) was characterized by H and C NMR, ESIꢀMS
and IR (see experimental section).
The reaction of a methanolic solution of 2,6ꢀbis[bis(2ꢀpyridylmethyl)aminomethyl]ꢀ4ꢀ
chlorophenol (LClꢀOH) with two equivalents of MCl2·nH2O (M = Co, n = 6; M = Ni, n = 6; M =
Cu, n = 2; M = Zn, n = 0) in the presence of NH4PF6 or NaClO4 afforded the dinuclear dichlorideꢀ
metal(II) complexes [Co2(µꢀLClO)(H2O)2Cl2][Co2(µꢀLClO)(MeOH)2Cl2](PF6)2 (1), [Ni2(µꢀ
LClO)(MeOH)2Cl2]PF6
(2),
[Ni2(µꢀLClO)(MeOH)(H2O)Cl2]ClO4·1.25H2O
(3),
[Cu2(µꢀ
4

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LClO)Cl2]PF6·½MeOH (4) and [Zn2(µꢀLClO)Cl2]PF6·MeOH (5) in moderate to high yields (60–
90%) in which the ligand was deprotonated. The isolated complexes were characterized by
elemental microanalyses, IR and UVꢀVis spectroscopy, ESIꢀMS and single crystal Xꢀray
crystallography. The magnetic properties of the complexes 1–4 were determined. The molar
conductivity of the complexes as measured in CH3CN revealed their typical 1:1 electrolytic nature
(ΛM = 132ꢀ140 Ωꢀ1 cm2 molꢀ1).
IR spectra of the complexes
The IR spectra of the complexes display some general characteristic features: 1) Medium broad
absorption band in the 4430ꢀ4450 cmꢀ1 region due to the stretching frequency ν(OꢀH) of the
coordinated and/or solvent of crystallization CH3OH and H2O. 2) A series of strong to medium
absorption bands over the 1610ꢀ1430 cmꢀ1 region attributable to the pyridyl groups {ν(C=C) and
ν(C=N)}. 3) The very sharp strong absorption band observed in complexes 1, 2, 4 and 5 around
ꢀ
840 cmꢀ1 is assigned to the ν(PꢀF) of PF6 anion, whereas Ni(II) complex 3 displays two strong
absorption bands at 1120 and 1097 cmꢀ1 due to the stretching frequency ν(ClꢀO) of the perchlorate
counter anion. The split of the perchlorate band in [Ni2(µꢀLClO)(MeOH)(H2O)Cl2]ClO4·1.25H2O
−
(3) may be attributed to the strong involvement of the ClO4 ions in Hꢀbonding with the aqua or
−
MeOH molecules (see Xꢀray section). This interaction reduces the symmetry of the ClO4 ion from
Td to C3υ or C2υ.
UVꢀVis spectra of the complexes
The UVꢀVis spectra of the complexes 1–4 were measured in CH3CN. The spectrum of [Co2(µꢀ
LClO)(H2O)2Cl2][Co2(µꢀLClO)(MeOH)2Cl2](PF6)2 (1) displays three distinct bands at around 564,
500 and 463 nm. These bands are typical for sixꢀcoordinate high spin Co(II) complexes and they
4
4
4
4
can be assigned to the spinꢀallowed transitions T2g(F) ← T1g(F), T1g(P) ← T1g(F) and 4A2g(F)
← 4T1g(F), respectively. Similarly, three bands were also detected for the complex cations [Ni2(µꢀ
LClO)(MeOH)2Cl2]+ and [Ni2(µꢀLClO)(MeOH)(H2O)Cl2]+ in complexes 2 and 3, respectively.
These bands are located at 1050, 795 and 640 nm indicating octahedral geometry around 3d8 Ni(II)
ion and result from the dꢀd electronic transitions 3T2g(F) ← 3A2g(F), 3T1g(F) ← 3A2g(F) and 3T1g(P)
← 3A2g(F), respectively.57
The spectrum of copper complex [Cu2(µꢀLClO)Cl2]PF6·½MeOH (4) reveals the presence of
two maxima at 457 and 695 nm. The broad single band at 695 nm suggests a distorted square
pyramidal (SP) environment around the central Cu2+ ion.58 In general, the visible spectra of the
fiveꢀcoordinate SP Cu(II) complexes are most likely producing a broad band over the 550–700 nm
range (dxz, dyz → dx2 y2) which occasionally may or may not be associated with a lowꢀenergy
−
5

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shoulder at λ > 800 nm, whereas the presence of a single d–d band at λ > 800 nm (dxy, dx2−y2 →
dz2) with a highꢀenergy shoulder is typical for trigonal bipyramidal (TBP) stereochemistry.58,59
Interestingly, the geometries of the complexes 1–4, as determined by UVꢀVis spectroscopy in
CH3CN solution, were in complete agreement with those obtained by single crystal Xꢀray
crystallography.
Mass spectral characterization of complexes
ESIꢀMass spectra of the five complexes were recorded in acetonitrile and all are shown in the ESI
section (Figs S1ꢀS5†). The mass spectrum of [Co2(LClO)(H2O)2Cl2][Co2(LClO)(MeOH)2Cl2](PF6)2
(1) showed a peak at m/z = 757.04 that corresponds to [Co2(LClO)(H2O)Cl2]+ (calcd m/z = 756.87).
In addition, another peak for a species was detected at m/z 825.04 which may result from
additional coordination of H2O/MeOH to the Co(II) centers, [Co2(LClO)(H2O)3(MeOH)Cl2]+ (calcd
m/z 824.94). Nickel(II) complexes 2 and 3 showed one major peak with m/z 757.08 which could be
assigned to [Ni2(LClO)(H2O)Cl2]+ (calcd m/z
=
756.40).
The complexes
[Cu2(LClO)Cl2]PF6·½MeOH (4) and [Zn2(LClO)Cl2]PF6·MeOH (5) revealed peaks at m/z = 767.03
and 771.07, respectively. These suggested the presence of protonated fragment
[M2(LClOH)(H2O)Cl2]2+ (calcd m/z: M = Cu, 767.10; M = Zn, 770.80) that is related to those
observed in complexes 1–3. The mass spectrum of Cu(II) complex 4 showed two more distinct
fragments at m/z 903.03 and 835.03. The former fragment may arise from additional coordination
of three acetonitrile molecules, [Cu2(LClO)(MeOH)(MeCN)3Cl2]+ (calcd m/z 903.28), whereas the
second fragment may indicate the formation of [Cu2(LClOH)(MeOH)(H2O)3Cl2]2+ (calcd m/z
835.17). Species with additional coordination such as [Cu2(LClO)(MeOH)(MeCN)3Cl2]+, which
observed above in complex 4 when CH3CN was used as a solvent in measuring mass spectra, have
been recently reported in some dinuclear cobalt(II) complexes.2 Complexes 1–5 reveal also the
presence of peaks at m/z 356.03, 356.04, 356.04, 356.01 and 278.17, respectively. Although we
were unable to identify the origin of these species most likely they are attributed to ligand
fragments. The acetonitrile mass spectrometry of [Cu2(LMeꢀO)2(OCH3)](ClO4)2 revealed a peak at
m/z 357.1, which is located at about the same positions as for complexes 1–4 was incorrectly
assigned for [Cu2(LMeꢀO)2(OH)]2+ ion.27 In addition to these peaks, the hexafluorophosphate
ꢀ
complexes 1, 2, 4 and 5 displayed an m/z peak at 144.97 (100%) for PF6 (calcd m/z 144.97),
ꢀ
whereas the corresponding perchlorate complex 3 showed a peak at m/z 98.95 (100%) (calcd ClO4
m/z 99.45).
Crystal structures of the complexes (1–5)
6

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[Co2(µꢀLClO)(H2O)2Cl2][Co2(µꢀLClO)(MeOH)2Cl2](PF6)2 (1). The crystal structure of 1 consists
of two dinuclear complex cations [Co2(LClO)(X)2Cl2]+ (X = H2O [Co(1)/Co(2)] or MeOH
ꢀ
[Co(3)/Co(4)] and PF6 counter ions. Perspective views of the complex cations together with
partial atom numbering schemes are given in Figures 1a and 1b, and selected bond parameters are
summarized in Table S1†. Each Co(II) center within a dinuclear complex cation is octahedrally
coordinated by three Nꢀdonor atoms of one bis(2ꢀpyridylmethyl)aminomethy group in a facꢀ
arrangement, a terminal chloride ligands trans to N(amine) of bis(2ꢀpyridylmethyl)aminomethyl
group, the bridging Oꢀatom of central 4ꢀchlorophenolate moiety and an oxygen atom of aqua
[Co(1)/Co(2)] or MeOH [Co(3)/Co(4)]. Both dinuclear subunits have a pseudoꢀ2ꢀfold axis passing
through the O and Cl atoms of the central 4ꢀchlorophenolate moiety. The Co–N bond distances are
in the range 2.085(5)ꢀ2.187(5) Å, the Co–Cl bond lengths are 2.3700(18) and 2.4298(16) Å, and
the Co–O bond lengths range from 2.087(4) to 2.178(5) Å. The Co(1)–O(1)–Co(2) and Co(3)–
O(2)–Co(4) bond angles of the ꢀꢀphenoxido bridges are 134.2(2) and 133.65(19)°, respectively.
The intraꢀdimeric Co(1)···Co(2) and Co(3)···Co(4) distances are 3.8840(12) and 3.9108(13) Å,
respectively, and the shortest interꢀdimer metalꢀmetal separation is 6.3536(11) Å. Hydrogen bonds
of type O–H···Cl are observed between aqua or MeOH donor ligands and chlorido acceptor
ligands [O···Cl separations from 3.0145(5) to 3.262(4) Å] (Fig. S6).
Please insert Fig. 1 close to here (Co complex 1)
[Ni2(µꢀLClO)(MeOH)2Cl2]PF6 (2) and [Ni2(µꢀLClO)(MeOH)(H2O)Cl2]ClO4ꢁ1.25H2O (3).
The crystal structures of 2 and 3 consist of dinuclear complex cations [Ni2(µꢀLClO)(X)2Cl2]+ (X =
ꢀ
ꢀ
MeOH for 2, H2O and MeOH for 3), PF6 or ClO4 counter ions and additional disordered lattice
water molecules in case of 3. Perspective views of the complex cations together with partial atom
numbering schemes are given in Figures 2 and 3, and selected bond parameters are summarized in
Tables S2 and S3†, respectively. Each Ni(II) center within a dinuclear complex cation is
octahedrally coordinated by three N donor atoms of one bis(2ꢀpyridylmethyl)amino group in a facꢀ
arrangement,
a
terminal chloride ligand anion trans to N(amine) of bis(2ꢀ
pyridylmethyl)aminomethyl group, the bridging O atom of the central 4ꢀchlorophenolate moiety
and oxygen atom of a terminal MeOH, except for Ni(2) of 3, where MeOH is replaced by a aqua
ligand. The dinuclear subunits also have a pseudoꢀ2ꢀfold axis passing through the O(1) and Cl(1)
atoms of the central 4ꢀchlorophenolate moiety. The Ni–N bond distances range from 2.042(3) to
2.111(3) Å, the Ni–Cl bond lengths from 2.3614(7) to 2.3826(9) Å, and the Ni–O bond lengths
from 2.0690(17) to 2.174(2) Å. The Ni(1)–O(1)–Ni(2) bond angles of the
ꢀꢀphenoxido bridges are
7

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136.63(7) and 132.64(11)° for 2 and 3, respectively. The intraꢀdimeric Ni(1)···Ni(2) distances are
3.9682(5) and 3.9728(6) Å, and the shortest interꢀdimer metalꢀmetal separations are 7.6769(5) and
7.0198(7) Å, for 2 and 3, respectively. Hydrogen bonds of type O–H···Cl are observed between
aqua or MeOH donor ligands and chlorido acceptor ligands [O···Cl separations range from
3.0145(5) to 3.262(4) Å]. Intraꢀdimer hydrogen bonds of type O–H···Cl were observed in both
crystal structures [O···Cl separations from 2.9747(19) to 3.047(3) Å] (Figs S7 and S8†). In case of
3, further hydrogen bonds of type O–H···O were observed [O(3)···O(5)(1/2ꢀx,1/2ꢀy,1/2+z) =
2.957(4) Å].
Please insert Figs. 2 and 3 close to here (Ni complexes 2 & 3)
[Cu2(µꢀLClO)Cl2]PF6ꢁ½MeOH (4) and [Zn2(µꢀLClO)Cl2]PF6ꢁMeOH (5). The crystal
structures of 4 and 5 consist of dinuclear complex cations [M2(LClO)Cl2]+ (M = Cu for 4, and Zn
ꢀ
for 5), PF6 counter ions and MeOH lattice solvent molecules. Perspective views of the crystal
structures together with partial atom numbering schemes are depicted in Figures 4 and 5, and
selected bond parameters are presented in Tables S4 and S5†, respectively. The dinuclear subunits
have also a pseudoꢀ2ꢀfold axis passing through O(1) and Cl(1) atoms of the central 4ꢀ
chlorophenolate moiety. Each copper(II) or zinc(II) center within a dinuclear complex cation is
pentaꢀcoordinated by three N–donor atoms of one bis(2ꢀpyridylmethyl)aminomethyl group, a
terminal chloride ligand in basal sites, and the bridging O(1) atom of central 4ꢀchlorophenolate
moiety, which occupies the axial position of the distorted square pyramids [τꢀvalues: 0.20 and 0.19
for Cu(1)and Cu(2); 0.28 and 0.32 for Zn(1) and Zn(2), respectively.60 The axial Cu–O(1) and Zn–
O(1) bond distances are 2.1915(11), 2.2089(11), 2.0518(11) and 2.0166(11) Å, respectively. The
Cu/Zn–N bond distances are in the range from 1.9951(15) to 2.2730(14) Å, the Cu/Zn–Cl bond
lengths vary from 2.2704(5) to 2.2995(4) Å. The metal centers deviate from their basal N3Cl plane
by 0.217 Å for Cu(1), 0.192 Å for Cu(2), 0.328 Å for Zn(1), and 0.406 Å for Zn(2). The Cu(1)–
O(1)–Cu(2) and Zn(1)–O(1)–Zn(2) bridging bond angles are 140.74(6) and 135.18(6)°,
respectively. The corresponding intraꢀdimeric metal···metal distances are 4.1447(4) and 3.7612(4)
Å, and the corresponding shortest interꢀdimer metalꢀmetal separations are 3.9446(4) and 4.1131(4)
Å. Hydrogen bonds of type O–H···F are observed between O atoms of MeOH solvent molecules
ꢀ
and F atoms of adjacent PF6 counter ions [O···F separations range from 2.886(4) to 3.029(2) Å]
(Figs S9 and S10†).
Please insert Figs. 4 and 5 close to here (Cu & Zn complexes 4 & 5)
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Magnetic properties of complexes 1ꢀ4
The experimental magnetic data of 1, depicted in Fig. 6, shows dominant antiferromagnetic
exchange within the Co(II) dimer as evidenced by a decrease of the effective magnetic moment
from 6.46 ꢀB (300 K) to 0.88 ꢀB (1.9 K) and also by the maximum of Mmol vs. T curve located at
21 K, which serves as a fingerprint for antiferromagnetically coupled homospin dimers.61
Furthermore, the significant zeroꢀfield splitting (ZFS) is expected in hexaꢀcoordinate Co(II)
complexes62 and therefore the following spin Hamiltonian was postulated
2
r r
2
i,z
2
i
ˆ
ˆ
ˆ
ˆ
H = −J S ⋅S
+
D (S − S / 3) +
ꢀ
BBgiSi,a
(1)
(
)
∑
1
2
i
i=1
where the isotropic exchange (J), the zeroꢀfield splitting (D) and Zeeman term (g) are included.
Then, the molar magnetization in a given direction of magnetic field Ba = Bꢁ(sin cos , sin sinϕ,
θ
ϕ
θ
cos
θ
) was calculated as
d ln Z
Ma = NAkT
(2)
dBa
Z is the partition function resulting from diagonalization of the spin Hamiltonian matrix. Finally,
the integral (orientational) average of molar magnetization was calculated by Eq. 3 in order to
properly simulate experimental powder magnetization data.
2
π
Mmol =1/ 4
π Ma sin
θ
d
θ
d
ϕ
(3)
π ∫0 ∫0
Moreover, the small amount of monomeric paramagnetic impurity (PI) which accounts for
an increase of molar magnetization (mean susceptibility) below 3 K was taken into consideration
by Eq. 4
Msample = (1− xPI )Mmol + 2⋅ xPIMPI
where MPI was calculated using the Brillouin function. Both temperature and field dependent
magnetic data were included into fitting procedure which resulted in these parameters for : J = ꢀ
8.38 cmꢀ1, D = 25.7 cmꢀ1, g = 2.39, χTIP = 4.9 10ꢀ9 m3molꢀ1, xPI = 0.79% (χTIP stands for the
(4)
1
x
temperatureꢀindependent paramagnetism). The results confirmed the moderate antiferromagnetic
exchange between Co(II) atoms and the substantial role of magnetic anisotropy as deduced from
the axial zeroꢀfield splitting parameter D. The small discrepancies between experimental and
calculated data are ascribed to the existence of two dimeric units within the asymmetric unit and
also to the fact that one of the dimers forms supramolecular tetramers through O–H⋅⋅⋅Cl hydrogen
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bonds (Fig. S11†). This probably creates more complex magnetic exchange pathways in the solid
state.
Please insert Fig 6 close to here (Co)
The magnetic data for the dinuclear nickel(II) complexes
2 and 3 are plotted in Fig. 7, and
Fig. S12†, respectively. In complex
2, the effective magnetic moment drops on cooling from 4.17
ꢀB (300 K) to 0.26 ꢀB (1.9 K) and the maximum of Mmol vs. T curve was found at 57 K, thus
confirming strong antiferromagnetic exchange with S = 0 ground state. Such strong
antiferromagnetic exchange means that excited molecular spin states S = 1 and S = 2, which bear
information about magnetic anisotropy (D), are too high in energy, and therefore low temperature
isothermal magnetization data (Mmol/NA
Therefore, only temperature data were used during the fitting procedure, which resulted in J = ꢀ
39.0 cmꢀ1, g = 2.19, χTIP = 2.2 10ꢀ9 m3molꢀ1, xPI = 0.51%. Compound
shows very similar
magnetic properties and the same magnetic analysis resulted in J = ꢀ30.2 cmꢀ1, g = 2.24, χTIP = 3.4
10ꢀ9 m3molꢀ1, xPI = 0.37% (Fig. S12†).
ꢀB < 0.1, Fig. 7) are nonꢀinformative concerning this issue.
x
3
x
Please insert Fig 7close to here (Ni-PF6)
In contrast to the above discussed results, the copper(II) complex
magnetic behaviour (Fig. 8). The effective magnetic moment is almost constant in whole
temperature range (ꢀeff ≈ 2.57 B) and only below 10 K the small drop of ꢀeff is observed (ꢀeff
2.32 B at T = 1.9 K). Moreover, there is no maximum on Mmol vs. T curve. Consequently, we can
presume only a very weak antiferromagnetic exchange in . The magnetic analysis of both
temperature and field dependent data resulted in J = ꢀ0.79 cmꢀ1, g = 2.10, χTIP = 0.24 10ꢀ9 m3molꢀ
4 exhibited different
ꢀ
=
ꢀ
4
x
1, thus confirming a very weak magnetic exchange between Cu(II) atoms of the antiferromagnetic
nature.
Please insert Fig 8 close to here (Cu-PF6)
Evaluation of magnetic properties using DFT calculations
In order to support the data of magnetic results which are showing large differences in the isotropic
exchange mediated by the LCl–OH ligand for various metal atoms and possibly to get insight into
the exchange mechanism, ab initio calculations based on DFT theory were used to calculate the J
parameters in the dinuclear moieties [Co2(µꢀLClꢀO)Cl2(H2O)2]+ of
1
, [Ni2(µꢀLClO)(CH3OH)2Cl2]+
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of
2
, [Ni2(µꢀLClO)(CH3OH)(H2O)Cl2]+ of
3
, and [Cu2(µꢀLClO)Cl2]+ of
4
. The ORCA 3.0.1
computational package was used for all the calculations.63 Well established B3LYP functional64
and def2ꢀTZVP(ꢀf) basis set65 were used to calculate the energy difference ꢁ, between high spin
(HS) and brokenꢀsymmetry (BS) spin states:
ꢂ = EBS ꢀ EHS
(5)
For the above mentioned structurally characterized dinuclear molecular fragments of 1ꢀ4
complexes, the following spin Hamiltonian for a dinuclear was used
r
r
2
ˆ
H = −J S ⋅ S
(
)
1
(6)
All the calculations utilized the RI approximation with the decontracted auxiliary def2ꢀ
TZV/J Coulomb fitting basis set and the chainꢀofꢀspheres (RIJCOSX) approximation to exact
exchange.66 Increased integration grids (Grid5 and GridX5in ORCA convention) and tight SCF
convergence criteria were also used. The isotropic exchange J values were calculated by Ruiz’s
approach (Eq. 7)67 and also by a more general Yamaguchi’s approach (Eq. 8)68:
J Ruiz = 2ꢁ / (S + S )(S + S +1)
(7)
(8)
[
]
1
2
1
2
J Yam = 2ꢁ / S2
− S2



HS
BS

The results of DFT calculations are summarized in Table 1. The J values calculated by
DFT correlate well with the experimentally determined antiferromagnetic exchange in , and in
1–4
the case of Co(II) and Ni(II) complexes the J’s calculated by the Ruiz’s approach are also very
close to those found from magnetic analysis, whereas in Cu(II) compound, the experimentally
determined J value is between JRuiz and JYam values.
Please insert Table 1 close to here
In case of [Co2(µꢀLClO)(H2O)2Cl2]+ of
1 2 and [Cu2(µꢀ
, [Ni2(µꢀLClO)(CH3OH)2Cl2]+ of
LClO)Cl2]+ of
4, the spin densities (Fig. 9) and also the nonꢀorthogonal magnetic orbitals (Fig. 10)
were visualized with the help of software Gabedit.69. Evidently, the unpaired electron of each
Cu(II) atom is localized in the dx2ꢀy2 orbital, which lies within the CuN3Cl plane. Therefore, there is
a very weak overlap between magnetic orbitals of Cu(II) atoms, which results in such very weak
antiferromagnetic exchange. On the contrary, the two unpaired electrons of Ni(II) atom are
localized in the dx2ꢀy2 and dz2 orbitals, leading to efficient overlap between magnetic orbitals
through the bridged phenoxido Ni–O–Ni bond resulting in a strong antiferromagnetic exchange.
Also, a consensus between DFT and magnetic analysis results in Ni(II) compounds
2 and 3 was
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acquired, showing that antiferromagnetic exchange is weaker in the case of
3
. This trend can be
related to the increase of Ni–O–Ni bond angle from 132.64° in
3 to 136.63° in 2, in such a way
that overlap of magnetic orbitals between Ni(II) atoms is increasing from the right angle to straight
angle. Thus, the larger Ni–O–Ni bond angle should result in a stronger antiferromagnetic exchange
as it is actually observed. The situation concerning the Co(II) complex is similar to the Ni(II)
complex meaning that superꢀexchange pathway is defined by Co–O–Co atoms and there is
efficient overlap of magnetic orbitals leading to moderate antiferromagnetic exchange (Fig. 10).
Also, there is nonꢀnegligible variation of DFTꢀderived Jꢀvalues vs. Co–O–Co bond angle in 1,
where larger Co–O–Co angle (134.15°) resulted in stronger antiferromagnetic exchange: JRuiz = ꢀ
8.82 cmꢀ1 for 133.66° angle in [Co2(µꢀLClO)(CH3OH)2Cl2]+ and JRuiz = ꢀ9.46 cmꢀ1 for 134.15° in
[Co2(µꢀLClO)(H2O)2Cl2]+ (Table 1). However, the effect of different solvent molecules (methanol
or water) on magnetic exchange cannot be excluded.
Please insert Figures. 9 & 10 close to here
Structure parameters and magnetic coupling
In general, bridgedꢀphenoxido dinuclear metal(II) complexes, which are derived from ligands with
pendant pyridyl and/or pyridyl derivative arms (Chart 1) exhibit weak to moderate
antiferromagnetic coupling.8,37,53,54,70ꢀ73 Copper(II) complexes in which a singly bridged
phenoxido group is the only bridge exhibit very weak antiferromagnetic coupling as this was the
case in complex
4
(J = ꢀ0.79 cmꢀ1). This has been observed in a number of related complexes such
as [Cu2(µꢀLMeꢀO)Cl2]ClO4 (J = 0 cmꢀ1),53 [Cu2(µꢀLMeꢀO)(OAc)2]ClO4·H2O (J = ꢀ0.6 cmꢀ1)37 and
[Cu2(µꢀLMeꢀO)(H2O)Cl](ClO4)2 (J = ꢀ1.7 cmꢀ1)73 and was attributed to the weak overlap between
the phenolate apical oxygen orbitals and the unpaired electron at each Cu(II) center which is
located in the equatorial plane (magnetic orbitals). Similar magnetic trends were reported with
other 3d metal ions such as in [Ni2(µꢀLMeꢀO)(µꢀOAc)2]BF4·2MeOH (J = ꢀ2.3 cmꢀ1) and [Mn2(µꢀ
L`MeꢀO)(µꢀOAc)2]ClO4 (J = ꢀ4.3 cmꢀ1) (see chart 1).2,8,70ꢀ72
Interestingly, nickel(II) complexes
2 and 3 revealed relatively high to moderate
antiferrmagnet coupling with J values of ꢀ39.0 and ꢀ30.2 cmꢀ1, respectively. As indicated above,
this was attributed to the efficient overlap between the Ni(II) magnetic orbitals dx2ꢀy2 and dz2 and
the oxygen 2p orbitals of the phenolate oxygen atom and to an increase of the Ni–O–Ni bond
angle. The paucity of the number of structurally and magnetically characterized Ni(II) compounds
did not allow us to compare our results with literature data.
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Although weak antiferromagnetic coupling was determined in Co(II) complex 1, [Co2(µꢀ
LClO)(H2O)2Cl2][Co2(µꢀLClO)(MeOH)2Cl2](PF6)2 (J = ꢀ8.38 cmꢀ1), still this coupling is relatively
stronger than those observed in related bridged phenoxido dinuclear Co(II) complexes based
pyridyl and substituted pyridyl arms (J ranges from ꢀ0.1 to ꢀ5.4 cmꢀ1).2,70,74 However, weak
ferromagnetic coupling was also reported in some related systems: [Co2(µꢀL1NO2ꢀO)(µꢀOAc)2]PF6
(J = +3.09 cmꢀ1) and [Co2(µꢀLBrꢀO)(µꢀOAc)2]PF6 (J = +0.78 cmꢀ1) (see Chart 1).75 No obvious
correlation was found between the magnitude or sign of J and the nature of the substituents at the
phenolic ring.75 In dicobalt(II) compounds, several factors were addressed to account for this weak
interactions. These include the Co(II)–Co(II) and Co–O(phenoxido) bond distances as well as Co–
O–Co bond angle,2,71,74,76,77 but unlike coupled dicopper and dinickel(II) complexes,78ꢀ80 the
magnetoꢀstructural relationship for dicobalt(II) is not well resolved. The results of dicobalt(II) and
dicopper(II) compounds clearly indicate that the µꢀphenoxido bridge is a poor mediator for
exchange magnetic interaction in this series of complexes.
Experimental
Materials and physical measurements
The compound bis(2ꢀpyridylmethyl)amine (DPA) was purchased from TCIꢀAmerica. All other
chemicals were commercially available and used without further purification. Infrared spectra
were recorded on a JASCO FTIRꢀ480 plus spectrometer as KBr pellets. Electronic spectra were
1
recorded using an Agilent 8453 HP diode array UVꢀVis spectrophotometer. H and 13C NMR
spectra were obtained at room temperature on a Varian 400 NMR spectrometer operating at 400
MHz (1H) and 100 MHz (13C). 1H and 13C NMR chemical shifts (δ) are reported in ppm and were
referenced internally to residual solvent resonances (DMSOꢀd6: δH = 2.49, δC = 39.4 ppm). ESIꢀ
MS were measured on LCꢀMS Varian Saturn 2200 Spectrometer. The conductivity measurements
were performed using Mettler Toledo Seven Easy conductivity meter and the cell constant was
determined by the aid of 1413 ꢃS/cm conductivity standard. The molar conductivity of the
complexes were determined from ΛM = (1.0x103 κ)/M, where κ = cell constant and M is the molar
concentration of the complex. Elemental analyses were carried out by the Atlantic
Microlaboratory, Norcross, Georgia U.S.A. Magnetic measurements of cobalt(II) (
compounds ( and ) were performed with a PPMS Dynacool VSM magnetometer (Quantum
Design, Inc.) (T = 1.9–300 K at B = 1 T; B = 0–9 T at T = 2, 5 and 10 K), while the copper(II)
1) and nickel(II)
2
3
complex
4
was measured on an MPMS XL7 SQUID magnetometer (Quantum Design, Inc.) (T =
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1.9–300 K at B = 1 T; B = 0–5 T at T = 2 and 5 K). The magnetic data were corrected for
diamagnetic susceptibilities and the signal of the sample holder.
Caution: Salts of perchlorate and their metal complexes are potentially explosive and should be
handled with great care and in small quantities.
Synthesis of the ligand
The ligand 2,6ꢀbis[bis(2ꢀpyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenol (LClꢀOH, Chart 1) was
synthesized via 2,6ꢀbis(chloromethyl)ꢀ4ꢀchlorophenol, which in turn was obtained by the
conversion of 4ꢀchlorophenol to 2,6ꢀbis(2ꢀhydroxomethyl)ꢀ4ꢀchlorophenol.
2,6ꢀBis(2ꢀhydroxomethyl)ꢀ4ꢀchlorophenol. This compound was prepared based on
published procedures,55,56 with modifications. An aqueous solution of NaOH (20.0 g, 0.5 mol in 20
mL of water) was added with stirring to a suspension of 4ꢀchlorophenol (12.8 g, 0.1 mol) in 30 mL
of 30% aqueous formaldehyde (0.3 mol). The mixture was kept at 30ꢀ40 °C for five days without
further stirring, at which time the sodium salt of the target compound had precipitated. This was
collected by filtration, washed with six 5 mL portions of saturated NaCl solution, and dissolved in
100 mL of boiling water. This solution was acidified by acetic acid until a pH of < 6 had been
reached and chilled in a refrigerator. The pale yellow product, which was collected by filtration
was washed with 10 mL of H2O and then dried in air (yield: 18.6 g, 63%, based on 4ꢀ
chlorophenol). Further recrystallization from ethyl acetate afforded offꢀwhite needles.
Characterization: mp 166ꢀ167 °C (Lit.: 165 °C),56 1H NMR (Na salt, D2O): 4.22 (s, exchangeable
proton), 4.73 (s, 4H; H2Cꢀ), 6.74 (s, 2H; protons at C3 and C5 of the phenyl group). 13C NMR (Na
salt, D2O): 60.20 (CH2ꢀ), 116.33 (C4), 125.80 (C4 and C6), 130.94 (C3 and C5), 161.15 (C1). The
compound was considered pure enough for further conversion to 2,6ꢀbis(chloromethyl)ꢀ4ꢀ
chlorophenol.
2,6ꢀBis(chloromethyl)ꢀ4ꢀchlorophenol. This compound was prepared by adapting a
procedure for preparing 2,6ꢀbis(chloromethyl)ꢀ4ꢀmethylphenol.81
bis(hydroxymethyl)ꢀ4ꢀchlorophenol (5.3 g, 0.028 mol), and 60 mL of aqueous 36% HCl (0.7 mol)
in CH2Cl2 (20 mL), charged into a 250 mL round bottom flask, was magnetically stirred
A
mixture of 2,6ꢀ
overnight at room temperature. The resulting two phases were separated and the aqueous phase
was extracted with CH2Cl2 (2 x 25 mL). The combined organic phases were vacuum evaporated
and the crude light brown solid was collected and extracted with hot heptane (2 × 30 mL).
Evaporation of heptane afforded the desired product as a white solid (yield, 4.2 g, 66%). Further
recrystallization from heptane resulted in the formation of colorless needles. Characterization: mp.
92ꢀ93 °C (Lit. 92ꢀ92.5 °C).82 1H NMR (CDCl3): 4.56 (s, 4H; CH2ꢀ), 5.66 (s, 1H; exchangeable
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phenolic proton), 7.21 (s, 2H; phenyl protons at C3 and C5). 13C NMR (CDCl3): 41.60 (CH2ꢀ),
125.64 (C4), 126.31 (C1 and C6), 130.58 (C3 and C5), 151.74 (C1).
Synthesis of 2,6ꢀbis[bis(2ꢀpyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenol (LClꢀOH). To 2,6ꢀ
bis(chloromethyl)ꢀ4ꢀchlorophenol (1.12 g, 5 mmol) dissolved in anhydrous CH3CN (50 mL),
bis(2ꢀpyridylmethyl)amine (2.00 g, 10 mmol) was added. The mixture was treated with anhydrous
K2CO3 (2.10 g, 15 mmol) and magnetically stirred under gentle reflux for 3 days, during which the
color turned light yellow and a white precipitate was formed. This mixture was cooled in the
refrigerator and then filtered off to remove KCl and unreacted K2CO3. The solvent was removed
with a rotary evaporator under reduced pressure and the resulting dark brown liquid was solidified
when stored over P2O5 in a desiccator under vacuum. Several crystallizations from Et2O with the
aid of activated charcoal afforded yellow oil which was then solidified to produce the desired
product as a pale yellow solid (yield: 2.2 g, 80%). Characterization: mp = 102ꢀ104 ºC, Selected IR
(KBr, cmꢀ1): 3421 (mb) ν(OꢀH); 3060 (w), 3022 (w) (pyridyl/phenyl CꢀH stretching); 2925 (w),
2832 (w), (aliphatic CꢀH stretching), 1589 (vs), 1569 (s), 1475 (s), 1433 (s) (C=C, C=N
pyridyl/phenyl ring stretching); 760 (vs) (CꢀH out of plane bending). ESIꢀMS in MeOH (100%)
m/z = 551.232 (Calcd for [M+H]+ = 552.103), 573.214 (Calcd for [M+Na]+ = 574.095), 589.188
(Calcd for [M+K]+ = 590.193). 1H NMR (DMSOꢀd6, 400 MHz, δ in ppm): δ = 8.50, 8.49 (2H,
phenyl protons), 7.73, 7.44 (m,4H), 7.40, 7.24 (m,4H) (pyridyl protons); 3.77 (s, 2H), 3.70 (s, 2H)
(CH2ꢀpy); 3.33 (s, 2H, CH2ꢀph).13C NMR: (DMSOꢀd6, 100 MHz) δ = 158.4, 154.3, 148.7, 136.7,
128.0, 126.1, 122.7, 122.4, 121.6 (pyridyl and phenyl carbons); 58.9, 53.3 (CH2ꢀph and CH2ꢀpy).
Syntheses of metal(II) complexes (1ꢀ5)
.
A general method was used to synthesize the dinuclear dichloro metal(II) complexes (1ꢀ5). To a
mixture containing MCl2·nH2O (M = Co, n = 6; M = Ni, n = 6; M = Cu, n = 2; M = Zn, n = 0)
(0.40 mmol) and 2,6ꢀbis[bis(2ꢀpyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenol (LClꢀOH) (0.110 g,
0.20 mmol) dissolved in MeOH (20 mL), NH4PF6 (80 mg, 0.50 mmol) or NaClO4 (61 mg, 0.50
mmol) in case of complex
3 was added and the resulting solution was heated on a steamꢀbath for
5ꢀ10 min. The resulting solution was filtered while hot through celite and then allowed to
crystallize at room temperature. The precipitate which was obtained over a period of 1ꢀ6 h was
collected by filtration, washed with propanꢀ2ꢀol and Et2O, and then dried at room temperature.
Long needles (pink for Co, bluish green for Ni, light green for Cu and colorless for Zn) suitable for
Xꢀray structure determination were obtained from dilute methanolic solutions of complexes
and . In case of
crystals of XꢀRay quality.
1
, 3, 4
5
2, recrystallization of the complex from CH3CN afforded bluish green single
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[Co2(LClꢀO)Cl2(H2O)2][Co2((LClꢀO)Cl2(CH2OH)2](PF6)2 (
1
).
The complex was isolated as
shiny pink long needles (overall yield: 163 mg, 87%). Characterization: Anal. Calcd for
C66H72Cl6Co4F12N12O6P2 (MM = 1867.76 g/mol): C, 42.44; H, 3.89; N, 9.00%. Found: C, 42.10;
H, 3.91; N, 9.06%. Selected IR bands (cmꢀ1): 3441 (s) ν(OꢀH), 1607 (vs) ν(C=C); 1573 (m), 1482
(m), 1463 (m), 1447 (m) ν(C=N); 844 (vs) ν(PꢀF). UVꢀ Vis. {λmax, nm (ε per Co atom, Mꢀ1cmꢀ1)}
in CH3CN: 463 (64.0), 500 (57.2), 543 (sh), 564 (83.4), ~701 (17.6 b). ESIꢀMS (CH3CN) for
positive
[Co2(C32H30ClN6O)Cl2(H2O)]+; 356.03, and for negative ions: m/z = 144.97 (100%), PF6 . Molar
conductivity in CH3CN, ΛM
136 Ωꢀ1 cm2 molꢀ1.
[Ni2((LClꢀO)Cl2(CH3OH)2]PF6 (
). This complex was isolated as bluishꢀgreen long needles
(overall yield: 135 mg, 71%). Characterization Anal. Calcd for C34H38Cl3F6Ni2N6O3P (MM =
ions:
m/z
=
825.04,
[Co2(C32H30ClN6O)Cl2(H2O)3(CH3OH)]+;
757.04,
ꢀ
=
2
:
947.43 g/mol): C, 43.10; H, 4.04; N, 8.87%. Found: C, 43.25; H, 4.13; N, 9.10%. Selected IR
bands (cmꢀ1): 3430 (mb), 1607 (m) ν(C=C); 1481 (w), 1463 (w), 1446 (m), 1435 (m) ν(C=N); 842
(vs) ν(PꢀF). UVꢀVis. {λmax, nm (ε per Ni atom, Mꢀ1cmꢀ1)} in CH3CN: 641 (11.7), 795 (5.3), 1050
(20.4, b). ESIꢀMS (CH3CN) for positive ions: m/z = 757.08, [Ni2(C32H30ClN6O)Cl2(H2O)]+;
ꢀ
356.04, and for negative ions: m/z = 144.97 (100%), PF6 . Molar conductivity in CH3CN, ΛM
137 Ωꢀ1 cm2 molꢀ1.
=
[Ni2((LClꢀO)Cl2(H2O)(CH3OH)]ClO4ꢁ1.25H2O (
3). This was isolated as light bluishꢀgreen
crystalline compound (overall yield: 168 mg, 71%). Characterization: Anal. Calcd for
C33H38.5Cl4Ni2N6O8.25 (MM = 907.86 g/mol): C, 42.66; H, 4.00; N, 9.26%. Found: C, 42.25; H,
4.23; N, 9.30%. Selected IR bands (cmꢀ1): 3452 (mb), 1607 (s) ν(C=C); 1573 (m), 1479 (m), 1450
(s), 1433 (s) ν(C=N); 1120 (s), 1097 (vs) ν(ClꢀO). UVꢀ Vis. {λmax, nm (ε per Ni atom, Mꢀ1cmꢀ1)} in
CH3CN: 640 (8.2), 795 (3.7), ~1050 (14.3,b). ESIꢀMS (CH3CN) for positive ions: m/z = 757.08,
ꢀ
[Ni2(C32H30ClN6O)Cl2(H2O)]+; 356.04, and for negative ions: m/z = 99.45 (100%), ClO4 = 99.45.
Molar conductivity, ΛM
(
CH3CN) = 132 Ωꢀ1 cm2 molꢀ1.
). The complex was isolated as light green crystalline
[Cu2(LClꢀO)Cl2]PF6ꢁ½CH3OH (
4
compound (overall yield: 110 mg, 59%). Characterization: Anal. Calcd for
C32.5H32Cl3Cu2F6N6O1.5P (MM = 909.06 g/mol): C, 42.94; H, 3.55; N, 9.24%. Found: C, 42.45; H,
3.78; N, 9.06%. Selected IR bands (cmꢀ1): 3442 (w,b) ν(OꢀH), 1611 (s) ν(C=C); 1575 (w), 1482
(m), 1462 (m), 1440 (s) ν(C=N); 844 (vs) ν(PꢀF). UVꢀVis. {λmax, nm (ε per Cu atom, Mꢀ1cmꢀ1)} in
CH3CN: 457 (103.8), 695 (128, b). ESIꢀMS (CH3CN) for positive ions: m/z = 903.03,
[Cu2(C32H30ClN6O)Cl2(MeOH)(MeCN)3]+; 835.03, [Cu2(C32H31ClN6O)Cl2(MeOH)(H2O)3]2+;
ꢀ
767.03, [Cu2(C32H31ClN6O)Cl2(H2O)]+; 356.01, and for negative ions: m/z = 144.97 (100%), PF6 .
Molar conductivity, ΛM (
CH3CN) = 140 Ωꢀ1 cm2 molꢀ1.
16

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[Zn2(LClꢀO)Cl2]PF6ꢁCH3OH (
5). This complex was isolated as colorless long needles
(overall yield: 140 mg, 75%). Characterization: Anal. Calcd for C33H34Cl3F6N6O2PZn2 (MM =
928.78 g/mol): C, 42.67; H, 3.69; N, 9.05%. Found: C, 43.01; H, 3.71; N, 9.17%. Selected IR
bands (cmꢀ1): 3445 (m,b) ν(OꢀH), 1609 (vs) ν(C=C); 1576 (m), 1468 (m), 1463 (s), 1443 ν(C=N);
846 (vs) ν(PꢀF). ESIꢀMS (CH3CN) for positive ions: m/z = 771.07, [Zn2(C32H31ClN6O)Cl2(H2O)]+,
ꢀ
278.17, and for negative ions: m/z = 144.96 (100%), PF6 . Molar conductivity, ΛM (CH3CN)
132 Ωꢀ1 cm2 molꢀ1.
=
Xꢀray crystal structure analysis
The Xꢀray singleꢀcrystal data of compounds 1ꢀ5 were collected on a BrukerꢀAXS APEX CCD
diffractometer at 100(2) K. The crystallographic data, conditions retained for the intensity data
collection and some features of the structure refinements are listed in Table 2. The intensities were
collected with MoꢀKα radiation (λ= 0.71073 Å). Data processing, Lorentzꢀpolarization and
absorption corrections were performed using APEX, and the SADABS computer programs.83 The
structures were solved by direct methods and refined by fullꢀmatrix leastꢀsquares methods on F2,
using the SHELXTL program package.84 All nonꢀhydrogen atoms were refined anisotropically.
The hydrogen atoms were located from difference Fourier maps, assigned with isotropic
displacement factors and included in the final refinement cycles by use of HFIX (parent C atom) or
DFIX (parent O atom) utility of the SHELXTL program. Molecular plots were performed with the
Mercury program.85 In case of
refinement. In case of , Uij constraints were applied for disordered water oxygen molecules and
their hydrogen atoms excluded from refinements.
1, data affected by twin components (8.6%) were excluded from
3
Please insert Table 2 close to here
Acknowledgements
This research was financially supported by the Department of ChemistryꢀUniversity of Louisiana
at Lafayette. FAM acknowledges support by NAWI Graz.
Electronic Supplementary Information (ESI)
CCDC 1034090ꢀ1034094 contain the supplementary crystallographic data for
These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. The mass spectra of the complexes are shown in
Figures S1ꢀS5, respectively and packing plots for crystal structures of compounds are
1 – 5, respectively.
1
– 5
1
– 5
17

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presented in Figures S6 – S10 and the corresponding selected bond parameters are summarized in
Tables S1 – S5, respectively. Figures S11 and S12 represent the formation of the supramolecular
tetramer of complex 1 and magnetic data for complex 3. For ESI and crystallographic data or other
electronic format see DOI: ?????????????????
Conclusion
Five dinuclear bridgedꢀphenoxido dichloroꢀmetal(II) complexes [Co2(µꢀLClO)(H2O)2Cl2][Co2(µꢀ
LClO)(MeOH)2Cl2](PF6)2 [Ni2(µꢀLClO)(MeOH)2Cl2]PF6
(1) (2) [Ni2(µꢀ
LClO)(MeOH)(H2O)Cl2]ClO4·1.25H2O (3), [Cu2(µꢀLClO)Cl2]PF6·½MeOH (4) and [Zn2(µꢀ
LClO)Cl2]PF6·MeOH
have been synthesized based on 2,6ꢀbis[bis(2ꢀ
pyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenolate ion (LClꢀOꢀ) and structurally characterized. The
complexes exhibit weak to moderate antiferromagnetic coupling. Attempts were made to
,
,
(5)
1–4
correlate the experimental coupling constants, J of the complexes to their structural parameters
and to the metal 3d and intervening oxygen 2p orbitals. The dicopper(II) and dicobalt(II)
complexes exhibit weak antiferromagnetic coupling, whereas the corresponding dinickel(II)
compounds reveal moderate to relatively strong magnetic coupling.
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TABLES
Table 1. DFTꢀcalculated net Mulliken spin densities (ρ), expected values <S2>, and isotropic
exchange parameters (J) from highꢀspin (HS) and broken symmetry spin (BS) states of the
dinuclear molecular fragments based on Xꢀray structures of 1ꢀ4
.
<S2
>
HS
<S2
>
BS
JRuiz/cmꢀ1 JYam/cmꢀ1
ꢁ/cmꢀ1
HS
BS
ρ
ρ
ρ
ρ
(Co1) = 2.71
(Co2) = 2.71
(Co3) = 2.70
(Co4) = 2.71
ρ
ρ
ρ
ρ
(Co1) = ꢀ2.71
[Co2(LClO)Cl2(H2O)2]+
[Co2(LClO)Cl2(CH3OH)2]+
[Ni2(LClO)(CH3OH)2Cl2]+
[Ni2(LClO)(CH3OH)(H2O)Cl2]+
[Cu2(LClO)Cl2]+
12.01
12.01
6.01
3.01
3.01
2.00
2.00
1.01
ꢀ56.728
ꢀ9.46
ꢀ8.82
ꢀ12.6
ꢀ11.76
ꢀ56.06
ꢀ39.16
ꢀ0.99
1
ρ(Co2) = 2.71
(Co3) = ꢀ2.70
ꢀ52.939
ρ(Co4) = 2.70
ρ
ρ
ρ
ρ
(Ni1) = 1.63
(Ni2) = 1.63
(Ni1) = 1.63
(Ni2) = 1.63
(Ni1) = ꢀ1.62
ꢀ
ꢀ37.44
ꢀ26.14
ꢀ0.49
2
3
4
112.338
ρ(Ni2) = 1.62
(Ni1) = ꢀ1.62
6.01
ꢀ78.427
ꢀ0.494
ρ
(Ni2) = 1.63
(Cu1) = ꢀ0.58
(Cu2) = 0.58
ρ
(Cu1) = 0.58
(Cu2) = 0.58
ρ
2.01
ρ
ρ
22

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Table 2. Crystallographic data and processing parameters for complexes
1 – .
5 a)
Compound
1
2
3
C66H72Cl6Co4F12N12O6P2 C34H38Cl3F6N6Ni2O3P C33H36Cl4N6Ni2O8.25
Empirical formula
Formula mass
System
1867.72
Triclinic
Pꢀ1
947.40
907.86
Monoclinic
C2/c
Monoclinic
P21/n
Space group
a (Å)
10.7772(10)
13.4024(5)
10.3560(5)
b (Å)
11.8843(11)
32.324(3)
97.470(6)
94.477(6)
106.833(5)
3899.7(6)
2
18.0346(7)
32.6751(12)
90
19.7894(9)
19.0876(9)
90
c (Å)
α (°)
β (°)
98.282(2)
90
96.752(2)
90
γ (°)
V (Å3)
7815.4(5)
8
3884.7(3)
4
Z
T (K)
ꢀ (mmꢀ1)
Dcalc (Mg/m3)
100(2)
100(2)
100(2)
1.168
1.282
1.301
1.519
1.610
1.552
Crystal size (mm)
θ max (°)
0.33 x 0.26 x 0.21
25.50
0.26 x 0.22 x 0.15
27.00
0.33 x 0.27 x 0.22
29.04
Data collected
Unique refl. / Rint
23532
64869
50341
23532 / ꢀꢀꢀꢀ
8523 / 0.0304
504 / 2
10297 / 0.0392
515 / 27
1.046
Parameters / Restraints 994 / 6
GoodnessꢀofꢀFit on F2 1.047
0.993
R1 / wR2 (all data)
Residual extrema (e/Å3) 1.41 / ꢀ0.85
0.0705 / 0.2168
0.0344 / 0.1086
1.00 / ꢀ0.62
0.0481 / 0.1381
1.62 / ꢀ0.88
23

Dalton Transactions
Page 26 of 32
View Article Online
DOI: 10.1039/C4DT03508A
Table 2. cont.
Compound
4
5
C
32.5H32Cl3Cu2F6N6O1.5P C33H34Cl3F6N6O2PZn2
Empirical formula
Formula mass
System
909.06
928.76
Monoclinic
P21/n
Monoclinic
P21/n
Space group
a (Å)
12.0536(5)
12.1205(4)
b (Å)
24.9462(11)
12.0840(5)
90
24.9231(8)
12.2116(3)
90
c (Å)
α (°)
β (°)
103.631(2)
90
103.081(2)
90
γ (°)
V (Å3)
3531.2(3)
4
3593.16(19)
4
Z
T (K)
ꢀ (mmꢀ1)
Dcalc (Mg/m3)
100(2)
100(2)
1.549
1.676
1.710
1.717
Crystal size (mm)
θ max (°)
0.30 x 0.25 x 0.18
29.090
0.26 x 0.22 x 0.15
30.010
Data collected
Unique refl. / Rint
108528
9419 / 0.0382
122582
2090 / 0.0434
483 / 1
Parameters / Restraints 483 / 1
GoodnessꢀofꢀFit on F2 1.137
1.103
R1 / wR2 (all data)
Residual extrema (e/Å3) 0.82 / ꢀ0.47
0.0322 / 0.0940
0.0276 / 0.0819
0.58 / ꢀ0.49
a) CCDC 1034090, 1034091, 1034092, 1034093 and 1034094 contain the crystallographic data
and the CIF format for the complexes, 1, 2, 3, 4 and 5, respectively.
24

Page 27 of 32
Dalton Transactions
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DOI: 10.1039/C4DT03508A
Figures and their Legends
a
)
b)
Fig. 1. a) Perspective views of Co1/Co2 and b) Co3/Co4 of the dinuclear subunits of 1.
25

Dalton Transactions
Page 28 of 32
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DOI: 10.1039/C4DT03508A
Fig. 2. Perspective view of 2.
Fig. 3. Perspective view of 3. Disordered lattice water molecules are omitted.
26

Page 29 of 32
Dalton Transactions
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DOI: 10.1039/C4DT03508A
Fig. 4. Perspective view of 4.
Fig. 5. Perspective view of 5.
27