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

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Spell, C. C. Ledet, T. Junk, R. Herchel, R. Fischer, Z. Travnicek and F. A. Mautner, Dalton Trans., 2014,

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Graphical Abstract

Magnetic and Structural Properties of Dinuclear Singly Bridged-Phenoxido

Metal(II) Complexes^†

Salah S. Massoud,^*aMark Spell,^a,‡Catherine C. Ledet,^aThomas Junk,^aRadovan Herchel,^bRoland

C. Fischer,^cZdeněk Trávníček,*^bFranz A. Mautner,*^d

^aDepartment 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

^dInstitut 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-L^ClO)(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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Magnetic and Structural Properties of Dinuclear Singly

Bridged-Phenoxido Metal(II) Complexes^†

Salah S. Massoud,^*aMark Spell,^a,‡Catherine C. Ledet,^aThomas Junk,^aRadovan

Herchel,^bRoland C. Fischer,^cZdeněk Trávníček,*^bFranz A. Mautner,*^d

^aDepartment 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

^dInstitut 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 (L^ClꢀOH) with MCl₂·nH₂O in the presence

of NH₄PF₆or NaClO₄afforded the dinuclear bridgedꢀphenoxido dichloridoꢀmetal(II) complexes

[Co₂(µꢀL^ClO)(H₂O)₂Cl₂][Co₂(µꢀL^ClO)(MeOH)₂Cl₂](PF₆)₂(1), [Ni₂(µꢀL^ClO)(MeOH)₂Cl₂]PF₆(2),

[Ni₂(µꢀL^ClO)(MeOH)(H₂O)Cl₂]ClO₄·1.25H₂O (3), [Cu₂(µꢀL^ClO)Cl₂]PF₆·½MeOH (4) and [Zn₂(µꢀ

L^ClO)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 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.

+

Cl

X = H₂O, CH₃OH, 0

M = Co, Ni, Cu, Zn

Cl

M

O

N

M

X

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.^1ꢀ13With

focus on compartmental ligands that are derived from phenolic containing compounds, these

ligands have been launched to study the phosphodiester hydrolysis and DNA cleavage^1ꢀ4and to

model purple acid phosphatases,^5,6Zn phosphesterases,^7,8Mn catalases,⁹catecholase oxidases,^10,11

metalloꢀβꢀlactamases (MβL)¹²and hemocyanin.¹³The 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 CO₂to 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 3d^7ꢀ9centers. 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.^35ꢀ43Similarly, bridged hydroxoꢀ,

methoxoꢀ and phosphoꢀester compounds were also observed.^22,44ꢀ48However, 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(L^RO)Cl₂]Y and [M₂(L^MeO)(X)₂]Y₃, where X = H₂O and CH₃CN; Y = ClO₄, PF₆

ꢀ

or BF₄and L^ROH = binucleating phenol.^34,52ꢀ54Therefore, this study was undertaken to explore

ꢀ

the

coordination

properties

of

this

class

of

compounds

using

bis[bis(2ꢀ

pyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenol (L^ClꢀOH) (Chart 1) with Co(II), Ni(II), Cu(II) and

Zn(II) metal ions.

Chart 1. Structure formulas of bis[bis(2ꢀpyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenol (L^ClꢀOH)

and related compounds

R

H₃CO

OCH₃

n

N

OH

N

OH

N

R = Cl, n = 1, L^Cl-OH

R = CH₃, n = 1, L^Me-OH

R = CH₃, n = 2, L`^Me-OH

R = Br, L1^Br-OH

R = NO₂,L1^NO2-OH

Results and discussion

Syntheses

The biꢀcompartmental phenolic ligand 2,6ꢀbis[bis(2ꢀpyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenol

(L^ClꢀOH) 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 L^ClꢀOH (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 (L^ClꢀOH) 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 NH₄PF₆or NaClO₄afforded the dinuclear dichlorideꢀ

metal(II) complexes [Co₂(µꢀL^ClO)(H₂O)₂Cl₂][Co₂(µꢀL^ClO)(MeOH)₂Cl₂](PF₆)₂(1), [Ni₂(µꢀ

L^ClO)(MeOH)₂Cl₂]PF₆

(2),

[Ni₂(µꢀL^ClO)(MeOH)(H₂O)Cl₂]ClO₄·1.25H₂O

(3),

[Cu₂(µꢀ

4

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L^ClO)Cl₂]PF₆·½MeOH (4) and [Zn₂(µꢀL^ClO)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

(Λ_M= 132ꢀ140 Ω^ꢀ1cm²mol^ꢀ1).

IR spectra of the complexes

The IR spectra of the complexes display some general characteristic features: 1) Medium broad

absorption band in the 4430ꢀ4450 cm^ꢀ1region 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 cm^ꢀ1region 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 cm^ꢀ1is assigned to the ν(PꢀF) of PF₆anion, whereas Ni(II) complex 3 displays two strong

absorption bands at 1120 and 1097 cm^ꢀ1due to the stretching frequency ν(ClꢀO) of the perchlorate

counter anion. The split of the perchlorate band in [Ni₂(µꢀL^ClO)(MeOH)(H₂O)Cl₂]ClO₄·1.25H₂O

−

(3) may be attributed to the strong involvement of the ClO₄ions in Hꢀbonding with the aqua or

−

MeOH molecules (see Xꢀray section). This interaction reduces the symmetry of the ClO₄ion from

T_dto C_3υor C_2υ.

UVꢀVis spectra of the complexes

The UVꢀVis spectra of the complexes 1–4 were measured in CH₃CN. The spectrum of [Co₂(µꢀ

L^ClO)(H₂O)₂Cl₂][Co₂(µꢀL^ClO)(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

can be assigned to the spinꢀallowed transitions T_2g(F) ← T_1g(F), T_1g(P) ← T_1g(F) and ⁴A_2g(F)

← ⁴T_1g(F), respectively. Similarly, three bands were also detected for the complex cations [Ni₂(µꢀ

L^ClO)(MeOH)₂Cl₂]⁺and [Ni₂(µꢀL^ClO)(MeOH)(H₂O)Cl₂]⁺in complexes 2 and 3, respectively.

These bands are located at 1050, 795 and 640 nm indicating octahedral geometry around 3d⁸Ni(II)

ion and result from the dꢀd electronic transitions ³T_2g(F) ← ³A_2g(F), ³T_1g(F) ← ³A_2g(F) and ³T_1g(P)

← ³A_2g(F), respectively.⁵⁷

The spectrum of copper complex [Cu₂(µꢀL^ClO)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.⁵⁸In 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 → dx²y²) 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(L^ClO)(H₂O)₂Cl₂][Co₂(L^ClO)(MeOH)₂Cl₂](PF₆)₂

(1) showed a peak at m/z = 757.04 that corresponds to [Co₂(L^ClO)(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(L^ClO)(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(L^ClO)(H₂O)Cl₂]⁺(calcd m/z

=

756.40).

The complexes

[Cu₂(L^ClO)Cl₂]PF₆·½MeOH (4) and [Zn₂(L^ClO)Cl₂]PF₆·MeOH (5) revealed peaks at m/z = 767.03

and 771.07, respectively. These suggested the presence of protonated fragment

[M₂(L^ClOH)(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(L^ClO)(MeOH)(MeCN)₃Cl₂]⁺(calcd m/z 903.28), whereas the

second fragment may indicate the formation of [Cu₂(L^ClOH)(MeOH)(H₂O)₃Cl₂]²⁺(calcd m/z

835.17). Species with additional coordination such as [Cu₂(L^ClO)(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.²Complexes 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(L^MeꢀO)₂(OCH₃)](ClO₄)₂revealed 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(L^MeꢀO)₂(OH)]²⁺ion.²⁷In 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(µꢀL^ClO)(H₂O)₂Cl₂][Co₂(µꢀL^ClO)(MeOH)₂Cl₂](PF₆)₂(1). The crystal structure of 1 consists

of two dinuclear complex cations [Co₂(L^ClO)(X)₂Cl₂]⁺(X = H₂O [Co(1)/Co(2)] or MeOH

ꢀ

[Co(3)/Co(4)] and PF₆counter 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(µꢀL^ClO)(MeOH)₂Cl₂]PF₆(2) and [Ni₂(µꢀL^ClO)(MeOH)(H₂O)Cl₂]ClO₄ꢁ1.25H₂O (3).

The crystal structures of 2 and 3 consist of dinuclear complex cations [Ni₂(µꢀL^ClO)(X)₂Cl₂]⁺(X =

ꢀ

MeOH for 2, H₂O and MeOH for 3), PF₆or ClO₄counter 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

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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(µꢀL^ClO)Cl₂]PF₆ꢁ½MeOH (4) and [Zn₂(µꢀL^ClO)Cl₂]PF₆ꢁMeOH (5). The crystal

structures of 4 and 5 consist of dinuclear complex cations [M₂(L^ClO)Cl₂]⁺(M = Cu for 4, and Zn

ꢀ

for 5), PF₆counter 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.⁶⁰The 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 PF₆counter 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 M_molvs. 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)

complexes⁶²and therefore the following spin Hamiltonian was postulated

2

r r

2

i,z

2

i

ˆ

H = −J S ⋅S

+

D (S − S / 3) +

ꢀ

_BBg_iS_i,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 B_a= Bꢁ(sin cos , sin sinϕ,

θ

ϕ

θ

cos

θ

) was calculated as

d ln Z

M_a= N_AkT

(2)

dB_a

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

M_mol=1/ 4

^πM_asin

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

M_sample= (1− x_PI)M_mol+ 2⋅ x_PIM_PI

where M_PIwas 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 cm^ꢀ1, D = 25.7 cm^ꢀ1, g = 2.39, χ_TIP= 4.9 10^ꢀ9m³mol^ꢀ1, x_PI= 0.79% (χ_TIPstands 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 M_molvs. 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 (M_mol/N_A

Therefore, only temperature data were used during the fitting procedure, which resulted in J = ꢀ

39.0 cm^ꢀ1, g = 2.19, χ_TIP= 2.2 10^ꢀ9m³mol^ꢀ1, x_PI= 0.51%. Compound

shows very similar

magnetic properties and the same magnetic analysis resulted in J = ꢀ30.2 cm^ꢀ1, g = 2.24, χ_TIP= 3.4

10^ꢀ9m³mol^ꢀ1, x_PI= 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 ꢀ_effis observed (ꢀ_eff

2.32 _Bat T = 1.9 K). Moreover, there is no maximum on M_molvs. 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 cm^ꢀ1, g = 2.10, χ_TIP= 0.24 10^ꢀ9m³mol^ꢀ

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 L^Cl–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(µꢀL^ClꢀO)Cl₂(H₂O)₂]⁺of

1

, [Ni₂(µꢀL^ClO)(CH₃OH)₂Cl₂]⁺

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of

2

, [Ni₂(µꢀL^ClO)(CH₃OH)(H₂O)Cl₂]⁺of

3

, and [Cu₂(µꢀL^ClO)Cl₂]⁺of

4

. The ORCA 3.0.1

computational package was used for all the calculations.⁶³Well established B3LYP functional⁶⁴

and def2ꢀTZVP(ꢀf) basis set⁶⁵were used to calculate the energy difference ꢁ, between high spin

(HS) and brokenꢀsymmetry (BS) spin states:

ꢂ = E_BSꢀ E_HS

(5)

For the above mentioned structurally characterized dinuclear molecular fragments of 1ꢀ4

complexes, the following spin Hamiltonian for a dinuclear was used

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.⁶⁶Increased 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)⁶⁷and 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 J^Ruizand J^Yamvalues.

Please insert Table 1 close to here

In case of [Co₂(µꢀL^ClO)(H₂O)₂Cl₂]⁺of

1 2 and [Cu₂(µꢀ

, [Ni₂(µꢀL^ClO)(CH₃OH)₂Cl₂]⁺of

L^ClO)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 d_x2ꢀy2orbital, 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 d_x2ꢀy2and d_z2orbitals, 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: J^Ruiz= ꢀ

8.82 cm^ꢀ1for 133.66° angle in [Co₂(µꢀL^ClO)(CH₃OH)₂Cl₂]⁺and J^Ruiz= ꢀ9.46 cm^ꢀ1for 134.15° in

[Co₂(µꢀL^ClO)(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 cm^ꢀ1). This has been observed in a number of related complexes such

as [Cu₂(µꢀL^MeꢀO)Cl₂]ClO₄(J = 0 cm^ꢀ1),⁵³[Cu₂(µꢀL^MeꢀO)(OAc)₂]ClO₄·H₂O (J = ꢀ0.6 cm^ꢀ1)³⁷and

[Cu₂(µꢀL^MeꢀO)(H₂O)Cl](ClO₄)₂(J = ꢀ1.7 cm^ꢀ1)⁷³and 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(µꢀL^MeꢀO)(µꢀOAc)₂]BF₄·2MeOH (J = ꢀ2.3 cm^ꢀ1) and [Mn₂(µꢀ

L`^MeꢀO)(µꢀOAc)₂]ClO₄(J = ꢀ4.3 cm^ꢀ1) (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 cm^ꢀ1, respectively. As indicated above,

this was attributed to the efficient overlap between the Ni(II) magnetic orbitals d_x2ꢀy2and d_z2and

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

L^ClO)(H₂O)₂Cl₂][Co₂(µꢀL^ClO)(MeOH)₂Cl₂](PF₆)₂(J = ꢀ8.38 cm^ꢀ1), 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 cm^ꢀ1).^2,70,74However, weak

ferromagnetic coupling was also reported in some related systems: [Co₂(µꢀL1^NO2ꢀO)(µꢀOAc)₂]PF₆

(J = +3.09 cm^ꢀ1) and [Co₂(µꢀL^BrꢀO)(µꢀOAc)₂]PF₆(J = +0.78 cm^ꢀ1) (see Chart 1).⁷⁵No obvious

correlation was found between the magnitude or sign of J and the nature of the substituents at the

phenolic ring.⁷⁵In 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,^78ꢀ80the

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: δ_H= 2.49, δ_C= 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 Λ_M= (1.0x10³κ)/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 (L^ClꢀOH, 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,^55,56with 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 1}H 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 1}H 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 (L^ClꢀOH). 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 P₂O₅in 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, cm^ꢀ1): 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 (L^ClꢀOH) (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(L^ClꢀO)Cl₂(H₂O)₂][Co₂((L^ClꢀO)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 (cm^ꢀ1): 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. {λ_max, nm (ε per Co atom, M^ꢀ1cm^ꢀ1)}

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, Λ_M

136 Ω^ꢀ1cm²mol^ꢀ1.

[Ni₂((L^ClꢀO)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 (cm^ꢀ1): 3430 (mb), 1607 (m) ν(C=C); 1481 (w), 1463 (w), 1446 (m), 1435 (m) ν(C=N); 842

(vs) ν(PꢀF). UVꢀVis. {λ_max, nm (ε per Ni atom, M^ꢀ1cm^ꢀ1)} 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, Λ_M

137 Ω^ꢀ1cm²mol^ꢀ1.

=

[Ni₂((L^ClꢀO)Cl₂(H₂O)(CH₃OH)]ClO₄ꢁ1.25H₂O (

3). This was isolated as light bluishꢀgreen

crystalline compound (overall yield: 168 mg, 71%). Characterization: Anal. Calcd for

C₃₃H_38.5Cl₄Ni₂N₆O_8.25(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 (cm^ꢀ1): 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. {λ_max, nm (ε per Ni atom, M^ꢀ1cm^ꢀ1)} 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, Λ_M

(

CH₃CN) = 132 Ω^ꢀ1cm²mol^ꢀ1.

). The complex was isolated as light green crystalline

[Cu₂(L^ClꢀO)Cl₂]PF₆ꢁ½CH₃OH (

4

compound (overall yield: 110 mg, 59%). Characterization: Anal. Calcd for

C_32.5H₃₂Cl₃Cu₂F₆N₆O_1.5P (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 (cm^ꢀ1): 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. {λ_max, nm (ε per Cu atom, M^ꢀ1cm^ꢀ1)} 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, Λ_M(

CH₃CN) = 140 Ω^ꢀ1cm²mol^ꢀ1.

16

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[Zn₂(L^ClꢀO)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 (cm^ꢀ1): 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, Λ_M(CH₃CN)

132 Ω^ꢀ1cm²mol^ꢀ1.

=

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.⁸³The

structures were solved by direct methods and refined by fullꢀmatrix leastꢀsquares methods on F²,

using the SHELXTL program package.⁸⁴All 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.⁸⁵In case of

refinement. In case of , U_ijconstraints 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(µꢀL^ClO)(H₂O)₂Cl₂][Co₂(µꢀ

L^ClO)(MeOH)₂Cl₂](PF₆)₂[Ni₂(µꢀL^ClO)(MeOH)₂Cl₂]PF₆

(1) (2) [Ni₂(µꢀ

L^ClO)(MeOH)(H₂O)Cl₂]ClO₄·1.25H₂O (3), [Cu₂(µꢀL^ClO)Cl₂]PF₆·½MeOH (4) and [Zn₂(µꢀ

L^ClO)Cl₂]PF₆·MeOH

have been synthesized based on 2,6ꢀbis[bis(2ꢀ

pyridylmethyl)aminomethyl]ꢀ4ꢀchlorophenolate ion (L^ClꢀO^ꢀ) 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

J^Ruiz/cm^ꢀ1J^Yam/cm^ꢀ1

ꢁ/cm^ꢀ1

HS

BS

ρ

(Co1) = 2.71

(Co2) = 2.71

(Co3) = 2.70

(Co4) = 2.71

ρ

(Co1) = ꢀ2.71

[Co₂(L^ClO)Cl₂(H₂O)₂]⁺

[Co₂(L^ClO)Cl₂(CH₃OH)₂]⁺

[Ni₂(L^ClO)(CH₃OH)₂Cl₂]⁺

[Ni₂(L^ClO)(CH₃OH)(H₂O)Cl₂]⁺

[Cu₂(L^ClO)Cl₂]⁺

12.01

6.01

3.01

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

(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

22

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DOI: 10.1039/C4DT03508A

Table 2. Crystallographic data and processing parameters for complexes

1 – .

5 ^a)

Compound

1

2

3

C₆₆H₇₂Cl₆Co₄F₁₂N₁₂O₆P₂C₃₄H₃₈Cl₃F₆N₆Ni₂O₃P C₃₃H₃₆Cl₄N₆Ni₂O_8.25

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)

ꢀ (mm^ꢀ1)

D_calc(Mg/m³)

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. / R_int

23532

64869

50341

23532 / ꢀꢀꢀꢀ

8523 / 0.0304

504 / 2

10297 / 0.0392

515 / 27

1.046

Parameters / Restraints 994 / 6

GoodnessꢀofꢀFit on F²1.047

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

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Table 2. cont.

Compound

4

5

C

_32.5H₃₂Cl₃Cu₂F₆N₆O_1.5P 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)

ꢀ (mm^ꢀ1)

D_calc(Mg/m³)

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. / R_int

108528

9419 / 0.0382

122582

2090 / 0.0434

483 / 1

Parameters / Restraints 483 / 1

GoodnessꢀofꢀFit on F²1.137

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

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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

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Fig. 2. Perspective view of 2.

Fig. 3. Perspective view of 3. Disordered lattice water molecules are omitted.

26

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Fig. 4. Perspective view of 4.

Fig. 5. Perspective view of 5.

27

Article Doi

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

DOI: 10.1039/c4dt03508a

Source and publish data:

Authors:

Article abstract of DOI:10.1039/c4dt03508a

Full text of DOI:10.1039/c4dt03508a

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