Polymeric and monomeric copper(II) thiophene- and furancarboxylato complexes. Bridging and terminal coordination of 3-pyridylmethanol

Accepted Manuscript Polymer ic and monomer ic copper (I I ) thiophene- and fur ancar boxylato complexes. Br idging and ter minal coor dination of 3-pyr idylmethanol Vladimír Kuchtanin, Jozef Švorec, Jan Moncol, Zdeňka Rů žičková, Milan Mazúr, Peter Segľa PII: DOI: Reference:

S0277-5387(16)30505-8 http://dx.doi.org/10.1016/j.poly.2016.10.009 POLY 12261

To appear in:

Polyhedron

Received Date: Revised Date: Accepted Date:

22 July 2016 5 October 2016 6 October 2016

Please cite this article as: V. Kuchtanin, J. Švorec, J. Moncol, Z. Rů žičková, M. Mazúr, P. Segľa, Polymer ic and monomer ic copper (I I ) thiophene- and fur ancar boxylato complexes. Br idging and ter minal coor dination of 3-pyr idylmethanol, Polyhedron (2016), doi: http://dx.doi.org/10.1016/j.poly.2016.10.009

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Polymeric and monomeric copper(II) thiophene- and furancarboxylato complexes. Bridging and terminal coordination of 3-pyridylmethanol. Vladimír Kuchtanina, Jozef Švoreca, Jan Moncola, Zdeňka Růžičkováb, Milan Mazúrc and Peter Segľa*a a

Department of Inorganic Chemistry, Faculty of Chemical and Food Technology, Slovak

Technical University, SK-81237 Bratislava, Slovakia b

Department of General and Inorganic Chemistry, Faculty of Chemical Technology,

University of Pardubice, CZ-532 10 Pardubice, Czech Republic c

Department of Physical Chemistry, Faculty of Chemical and Food Technology, Slovak

Technical University, SK-81237 Bratislava, Slovakia Keywords: Copper(II), pyridylmethanol, bridging ligands, crystal structure, hydrogen bonds, thiophenecarboxylato, furancarboxylato * Corresponding author. Tel.: +421 2593 25 209; fax: +421 2524 93 198. E-mail address: [email protected] (P. Segla).

Abstract The synthesis and characterization of eight new coordination compounds [Cu(2-tpc)2(µ-3pyme)2]n (1), [Cu(3-Me-2-tpc)2(µ-3-pyme)2]n (2), [Cu(5-Me-2-tpc)2(µ-3-pyme)2]n (3), [Cu(5-Cl-2tpc)2(3-pyme)2] (4), [Cu(2-fuc)2(µ-3-pyme)2]n (5), [Cu(3-fuc)2(µ-3-pyme)2]n (6), [Cu(2,5-Me2-3fuc)2(µ-3-pyme)2]n

(7),

and

[Cu(5-NO2-2-fuc)2(µ-3-pyme)2]n

(8)

(where

2-tpc

is

2-

thiophenecarboxylato, 3-Me-2-tpc is 3-methyl-2-thiophenecarboxylato, 5-Me-2-tpc is 5-methyl2-thiophenecarboxylato,

5-Cl-2-tpc

is

5-chloro-2-thiophenecarboxylato,

2-fuc

is

2-

furancarboxylato, 3-fuc is 3-furancarboxylato, 2,5-Me2-3-fuc is 2,5-dimethyl-3-furancarboxylato, 5-NO2-2-fuc is 5-nitro-2-furancarboxylato and 3-pyme is 3-pyridylmethanol) is reported and their X-ray structures were determined. X-ray analysis revealed samples 1–3 and 5–8 to be coordination polymers, whereas the complex 4 is monomeric. The polymeric extension is achieved through bridging N,O -3-pyridylmethanol molecules, resulting in the observation of 2-D (1–3, 5−7) or 1−D polymeric chains (8). In addition, the coordination polymers are also stabilized by strong intramolecular hydrogen bonds. On the other hand, the monomeric compound 4 with monodentate N-coordinated 3-pyridylmethanol ligands forms 1-D supramolecular chain due to

strong intermolecular hydrogen bonds. Electronic, IR, EPR spectra and magnetic susceptibility measurements over the temperature range 1.8–300 K are discussed in terms of known crystal and molecular structure. Based on the IR spectra it can be concluded that the type of coordination of 3-pyridylmethanol as well as hydrogen bonds strongly influence the position and the shape of the stretch vibrations bands assigned to hydroxyl group.

Introduction The coordination bonds between transition metal ions and nitrogen containing heterocyclic ligands are often utilized in the construction of solid-state architectures and inorganic crystal engineering [1]. The field of coordination polymers represents growing area of solid-state coordination chemistry [2, 3]. It is well known that 3-pyme as bridging ligand usually prefers formation of copper(II) carboxylate coordination polymers [Cu(RCO2)2(µ-3-pyme)2]n with tetragonal bipyramidal geometry around the Cu(II) atom [4,5]. The structures of the complex polymers are one-dimensional chain-like [4–8], or two-dimensional sheet-like [4, 9–15]. On the other hand, only a few copper(II) coordination compounds with 3pyridylmethanol as monodentate N-coordinated terminal ligand exist. For example, the coordination compound [Cu2(CH3CO2)4(3-pyme)2]·CH2Cl2 has a paddle-wheel dinuclear molecular structure with two terminal 3-pyridylmethanol ligands [16]. The copper(II) carboxylato

complexes

[Cu(2-NO2bz)2(3-pyme)2(H2O)2]

[5],

[Cu(3-pyac)2(3-

pyme)2(H2O)] (3-pyac = 3-pyridylacrylato) [17] exhibit monomeric molecular structures with two terminal 3-pyridylmethanol ligands and square planar complex [Cu(2,6pydicarb)(3-pyme)] (2,6-pydicarb = 2,6-pyridyldicarboxylato) [18] with one terminal 3pyme ligand. Terminal 3-pyridylmethanol ligands were also found in the mononuclear [CuCl2(3-pyme)4] [19] and in the oxalato-bridged coordination polymer [Cu(µ-C2O4)(3pyme)2]n

[20].

Eventually,

two

other

copper(II)

coordination

polymers

[Cu3(C2H5CO2)6(µ-3-pyme)2(3-pyme)2]n [21] and [Cu3(2-Clnic)6-(µ-3-pyme)4(3-pyme)2]n (2-Clnic = 2-chloronicotinato) [4] are known in which the 3-pyridylmethanol molecules act as bridging as well as terminal ligands. Our previous studies on structural and magnetic properties of copper(II) furanand thiophenecarboxylates containing solvent molecules (water and dimetylsulfoxide) or

N-heterocyclic ligands such as nicotinamide, N-methylnicotinamide or ethylnicotinate showed great variability of a structural type: monomeric [22,23], dimeric [23−25] or polymeric [23]. However, in these coordination compounds N-heterocyclic ligands act as a N-donor terminal ligand coordinated to the central copper atom exclusively through a nitrogen atom of a pyridine ring. In this paper, we describe the synthesis, spectral and magnetic properties as well as crystal and molecular structures of eight new complexes with formulas [Cu(2-tpc)2(µ3-pyme)2]n (1), where 2-tpc is 2-thiophenecarboxylato; [Cu(3-Me-2-tpc)2(µ-3-pyme)2]n (2), where 3-Me-2-tpc is 3-methyl-2-thiophenecarboxylato; [Cu(5-Me-2-tpc)2(µ-3pyme)2]n (3), where 5-Me-2-tpc is 5-methyl-2-thiophenecarboxylato; [Cu(5-Cl-2-tpc)2(3pyme)2] (4), where 5-Cl-2-tpc is 5-chloro-2-thiophenecarboxylato; [Cu(2-fuc)2(µ-3pyme)2]n (5),where 2-fuc is 2-furancarboxylato; [Cu(3-fuc)2(µ-3-pyme)2]n (6), where 3fuc is 3-furancarboxylato; [Cu(2,5-Me2-3-fuc)2(µ-3-pyme)2]n (7), where 2,5-Me2-3-fuc is 2,5-dimethyl-3-furancarboxylato and [Cu(5-NO2-2-fuc)2(µ-3-pyme)2]n (8), where 5-NO22-fuc is 5-nitro-2-furancarboxylato. Moreover, the IR spectrum of our previously prepared coordination polymer [Cu3(2-Clnic)6-(µ-3-pyme)4(3-pyme)2]n (9) [4] has been interpreted in more detail. Topological structures and abbreviations of ligands under study are given in Fig.1.

O

S

O

S

2-thiophenecarboxylato (2-tpc)

5-methyl-2-thiophenecarboxylato (5-Me-2-tpc)

3-methyl-2-thiophenecarboxylato (3-Me-2-tpc)

O

O

S

O

O

O

Cl

O

S

O

O O

O

O O

5-chlor-2-thiophenecarboxylato (5-Cl-2-tpc)

2-furancarboxylato (2-fuc)

O O2N

O

3-furancarboxylato (3-fuc)

O

CH2OH O

O

N

O 2,5-dimethyl-3-furancarboxylato (2,5-Me2-3-fuc)

5-nitro-2-furancarboxylato (5-NO2-2-fuc)

3-pyridylmethanol (3-pyme)

Fig. 1. Structures and abbreviations of the ligands.

Experimental

2.1. Chemical reagents and analysis The chemicals used were of reagent grade (Aldrich or Sigma) and used without further purification. The organic reagents were purchased from Aldrich; their purity was checked by IR spectra. Copper content was determined by electrolysis after mineralization of the complexes; carbon, hydrogen, nitrogen and sulphur contents were determined by microanalytical methods (Thermo Electron Flash EA 1112). Analytical data and yields for the solid compounds are given in Table 1.

Table 1 Analytical dataa for the complexes. Compounds

Yield %

Found (Calcd.) % Cu C H N S 80 11.95 49.09 3.60 5.10 12.15 [Cu(2-tpc)2(µ-3-pyme)2]n (1) (11.85) (49.29) (3.76) (5.23) (11.96) 83 11.02 50.92 4.12 4.84 10.90 [Cu(3-Me-2-tpc)2(µ-3-pyme)2]n (2) (11.26) (51.10) (4.29) (4.97) (11.37) 85 10.99 51.17 4.16 4.88 10.97 [Cu(5-Me-2-tpc)2(µ-3-pyme)2]n (3) (11.26) (51.10) (4.29) (4.97) (11.37) [Cu(5-Cl-2-tpc)2(3-pyme)2] (4) 78 10.45 43,52 3,01 4.48 10.90 (10.50) (43.68) (3.30) (4.63) (10.60) 80 12.37 52.08 3.95 5.77 – [Cu(2-fuc)2(µ-3-pyme)2]n (5) (12.61) (52.43) (4.00) (5.56) 75 12.44 52.29 3.88 5.48 – [Cu(3-fuc)2(µ-3-pyme)2]n (6) (12.61) (52.43) (4.00) (5.56) 85 11.10 55.86 4.83 5.07 – [Cu(2,5-Me2-3-fuc)2(µ-3-pyme)2]n (7) (11.35) (55.76) (5.04) (5.00) 85 10.60 44.72 3.14 9.56 – [Cu(5-NO2-2-fuc)2(µ-3-pyme)2]n (8) (10.70) (44.49) (3.05) (9.43) a Microanalysis results obtained with maximum deviations: Cu, ±0.27; C±0.35; H±0.32; N±0.21; S±0.47.

2.2. Synthesis 2.2.1. [Cu(2-tpc)2(µ-3-pyme)2]n (1) The blue crystals were obtained by dissolving copper(II) nitrate (2.5 mmol), 2thiophenecarboxylic acid (5 mmol) and excess of 3-pyridylmethanol (12.5 mmol) in 50 cm3 of methanol. The resulting solution was refluxed for 2 h and then left to slowly evaporate at ambient temperature. Well-shaped crystals of 1, suitable for X-ray structure analysis, were collected after a few days by filtration, washed with methanol and finally dried at ambient temperature (yield in Table 1). 2.2.2. [Cu(3-Me-2-tpc)2(µ-3-pyme)2]n (2), [Cu(5-Cl-2-tpc)2(3-pyme)2] (4), [Cu(2,5-Me23-fuc)2(µ-3-pyme)2]n (7) Copper(II) nitrate (2.5 mmol), 3-methyl-2-thiophenecarboxylic acid (5 mmol), 5chloro-2-thiophenecarboxylic acid (5 mmol) or 2,5-dimethyl-3-furancarboxylic acid (5 mmol) and excess of 3-pyridylmethanol (12.5 mmol) were dissolved in 50 cm3 of acetonitrile. The reaction mixture was refluxed for 2 h. Blue crystals of 2, 4 or 7 were collected after several days by filtration, washed with acetonitrile and dried at ambient temperature.

2.2.3. [Cu(5-Me-2-tpc)2(µ-3-pyme)2] (3), [Cu(2-fuc)2(µ-3-pyme)2]n (5), [Cu(3-fuc)2(µ-3pyme)2]n (6) Copper(II) nitrate (2.5 mmol), 5-methyl-2-thiophenecarboxylic acid (5 mmol), 2furancarboxylic acid (5 mmol) or 3-furancarboxylic acid (5 mmol) with sodium hydroxide (5 mmol) and 3-pyridylmethanol (12.5 mmol) were dissolved in 50 cm3 of methanol. The reaction mixture was refluxed for 2 h. Blue crystals of 3, 5 or 6 were collected after several days by filtration, washed with methanol and dried at ambient temperature. 2.2.4. [Cu(5-NO2-2-fuc)2(µ-3-pyme)2]n (8) The blue crystals of 8 were obtained by dissolving of copper(II) acetate (2.5 mmol), 2-furancarboxylic acid (5 mmol) and excess of 3-pyridylmethanol (12.5 mmol) in 50 cm3 of methanol. The resulting solution was refluxed for 2 h and then left to slowly evaporate at ambient temperature. Blue crystals were collected after several days by filtration, washed with methanol and dried at ambient temperature.

2.3. Physical measurements Spectral measurements Electronic spectra (9000 – 50 000 cm–1) of the powdered samples in nujol mulls were recorded at room temperature (r.t.) on Specord 200 spectrophotometer (Carl Zeiss Jena). Infrared spectra in the region of 400 – 4000 cm–1 were recorded on a Nicolet 5700 FT-IR spectrometer (Thermo Scientific). Spectra of the solid samples were obtained by ATR or KBr technique at room temperature. EPR spectra of polycrystalline samples were recorded at room temperature with a spectrometer Bruker EMX series operating at X-band (~9.4 GHz). EPR spectra were simulated using EPR simulation package EasySpin [26].

Magnetic measurements Variable-temperature magnetic measurements of polycrystalline samples were carried out with a Quantum Design SQUID magnetometer (MPMSXL–5-type) at a

magnetic field of B = 1 T over the temperature range 1.8–300 K. Corrections are based on subtracting the sample-holder signal, contribution χDia estimated from Pascal constants [27] and temperature independent paramagnetism of Cu(II) centers (60 × 10–6 cm3 mol–1) [28]. Magnetization versus magnetic field was measured at the temperature 2 and 4.6 K in the magnetic field range 0-7 Tesla. The effective magnetic moment was calculated from the equation: µeff = 2.83( χ M T )1 / 2 ( B.M .)

2.4. X-ray crystallography Data collection for single crystal crystallography and cell refinement was carried out using kappa-axis four-circle diffractometers Bruker Kappa APEX-II CCD or BrukerNonius KappaCCD with graphite monochromated MoKα radiation. The diffraction intensities were corrected for Lorentz and polarization factors. The structures were solved using charge-flipping method SUPERFLIP [29] or direct methods with programs SHELXT [30] or SIR-2011 [31], and refined by the full-matrix least squares procedure with SHELXL (ver. 2016/4) [32] or CRYSTALS (ver. 14.40) [33]. The semi-empirical absorption corrections were made by using multi-scans method [34]. Geometrical analyses were performed using SHELXL or CRYSTALS and the structures were drawn using the OLEX2 [35] program. Final crystal data and structure refinement parameters are given in Table 2. The selected bond distances are given in Table 3. The positions of all hydrogen atoms have been constrained for all compound using AFIX (SHELXL) or RIDE (CRYSTALS) commands.

Table 2 Crystallographic data for compounds 1–8.

Chemical formula

1 C22H20CuN2O6S2

2 C24H24CuN2O6S2

3 C24H24CuN2O6S2

4 C22H18Cl2CuN2O6S2

Mr

536.09

564.14

564.14

604.97

Cell setting, space group T (K)

Orthorhombic, Pbca

Orthorhombic, Pbca

Orthorhombic, Pbca

Triclinic, P-1

a (Å) b (Å) c (Å) α (°) β (°) γ (°) V (Å3)

150 12.7960(5) 9.3710(9) 18.9870(13) 90 90 90 2276.8(3)

150 13.2080(4) 9.1700(7) 19.9320(10) 90 90 90 2414.1(2)

150 12.3990(8) 9.1890(8) 21.9590(10) 90 90 90 2501.9(3)

293 6.6470(10) 9.0610(10) 11.2650(10) 88.530(10) 75.060(10) 72.560(10) 615.03(13)

Z

4

4

4

1

S

1.063

1.039

1.000

1.028

0.0362, 0.0959

0.0375, 0.0906

0.0329, 0.0676

0.0454, 0.1154

2306/26/152

2450/26/179

1735/0/160

2491/3/164

0.37, -0.39 910188 5 C22H20CuN2O8 503.94

0.51, -0.44 910189 6 C22H20CuN2O8 503.94

0.37, -0.28 910190 7 C26H28CuN2O8 560.06

0.52, -0.39 910191 8 C22H18CuN4O12 593.95

Orthorhombic, Pbca

Orthorhombic, Pbca

Monoclinic, P21/c

Monoclinic, P21/c

a (Å) b (Å) c (Å) α (°) β (°) γ (°) V (Å3)

150 12.5450(8) 9.4440(5) 18.3120(9) 90 90 90 2169.5(2)

150 12.5750(5) 9.3240(7) 18.8410(9) 90 90 90 2209.1(2)

150 11.0610(3) 9.1570(2) 13.6010(7) 90 107.74(3) 90 1312.0(2)

150 6.7690(2) 14.5600(8) 12.7270(6) 90 109.557(4) 90 1181.97(10)

Z

4

4

2

2

S

1.024

1.075

1.070

1.049

R1[F2 > 2σ(F2)], wR2(F2) Data / restrains / parameters ∆ρmax, ∆ρmin (e Å−3)

0.0367, 0.0903

0.0339, 0.0833

0.0325, 0.0865

0.0254, 0.0501

2196/0/152

2222/0/152

2653/0/171

1938/9/178

0.28, -0.30 910192

0.38, -0.36 910193

0.23, -0.42 910194

0.29, -0.21 910195

2

2

R1[F > 2σ(F )], wR2(F2) Data / restrains / parameters ∆ρmax, ∆ρmin (e Å−3) CCDC Chemical formula

Mr Cell setting, space group T (K)

CCDC

Results and Discussion

3.1. Crystal structures The molecular structures of compounds 1–8 with atomic numbering schemes of independent parts are shown in Figure 2. All compounds crystallize in centrosymmetric space groups. The isostructural compounds 1–3, 5 and 6 crystallize in orthorhombic system in space group Pbca. The copper(II) atoms in these five complexes lie in centre of symmetry and their coordination environment is tetragonal-bipyramidal. The tetragonal plane is built up by a pair of unidentate thiophenecarboxylato or furancarboxylato anions using carboxylato oxygen atoms (O1) and a pair of neutral 3-pyridylmethanol ligands using nitrogen atoms of pyridine rings (N1) in trans positions. The bond lengths Cu1–O1 and Cu1–N1 are in the narrow ranges 1.945(2)–1.955(2) Ǻ and 2.015(2)–2.025(2) Ǻ (Table 3), respectively. The axial positions are occupied by two hydroxyl oxygen atoms (O3) of the neighbouring 3-pyridylmethanol hydroxyl groups with bond lengths Cu1–O3ii and Cu1–O3iii in the range 2.447(2)–2.648(2) Ǻ (Table 3). The hydroxyl hydrogen atoms of 3-pyridylmethanol are "fixed" to the uncoordinated carboxylato oxygen atoms O2ix by hydrogen bonds O3–H3O···O2ix with interatomic O3···O2ix distances in the range 2.652(2)–2.671(4) Ǻ (Table 3) and form supramolecular synthon S(6). [42]. The crystal structures of 1–3, 5 and 6 consist of 2-D layers (Fig. 3A), which are situated parallel with ab plane.

1)

2)

4)

3)

5)

7)

6)

8) Fig. 2. Molecular structure of 1–8.

Table 3 Selected bond lengths (Å) and hydrogen bond parameters (Å,°) for complexes 1–8. Cu1–O1 Cu1–O1a Cu1–N1 Cu1–N1a Cu1–O3a Cu1–O3a Cu1–O2 Cu1–O2a T

1 1.950(2) 1.950(2) (i) 2.018(2) 2.018(2) (i) 2.583(2) (ii) 2.583(2) (iii)

2 1.949(2) 1.949(2) (i) 2.020(2) 2.020(2) (i) 2.649(2) (ii) 2.649(2) (iii)

3 1.945(2) 1.945(2) (i) 2.025(2) 2.025(2) (i) 2.447(2) (ii) 2.447(2) (iii)

0.768

0.749

0.811

O3–H3O···O2ix 1.86 2.657(3)

O3–H3O···O2ix 1.84 2.658(3)

O3–H3O···O2ix 1.87 2.671(4)

4 1.995(2) 1.995(2) (iv) 1.992(3) 1.992(3) (iv) 2.524(3) 2.524(3) (iv) 0.790

5 1.955(2) 1.955(2) (i) 2.015(2) 2.015(2) (i) 2.533(2) (ii) 2.533(2) (iii)

6 1.954(2) 1.954(2) (i) 2.016(2) 2.016(2) (i) 2.548(2) (ii) 2.548(2) (iii)

7 1.927(1) 1.927(1) (i) 2.020(2) 2.020(2) (i) 2.682(2) (v) 2.682(2) (vi)

8 1.965(1) 1.965(1) (i) 2.036(1) 2.036(1) (i) 2.466(1) (vii) 2.466(1) (viii)

0.784

0.779

0.775

0.811

O3–H3···O2x b O3–H3O···O2ix O3–H3O···O2ix O3–H3O···O2xi O3–H3O···O2xii 1.96, 1.81 1.85 1.82 1.85 1.87 2.744(7), 2.660(3) 2.652(2) 2.669(2) 2.676(3) 2.631(15) <( D–H···A) 162 166 160 159, 177 162 170 165 160 a Symmetry codes: (i) -x, -y, -z; (ii) -x+1/2, y+1/2, z; (iii) x-1/2, -y-1/2, -z; (iv) -x+1, -y+1, -z+1; (v) x, -y+1/2, z-1/2; (vi) -x, y-1/2, -z+1/2; (vii) -x-1, -y, -z; (viii) x+1, y, z; (ix) x+1/2, -y-1/2, -z; (x) -x+1, -y, -z+1; (xi) -x, y+1/2, -z+1/2; (xii) x-1, y, z. b The group is disordered and hydrogen bond has two forms: O3A– H3A···O2x and O3B–H3B···O2x. D–H···A d(H···A) d(D···A)

The coordination polymer 7 forms similar crystal structure as complexes 1–3, 5 and 6 containing 2-D sheets, but compound crystallizes in monoclinic centrosymmetric space group P21/c. The 2-D layers of 7 are situated parallel with bc plane. The coordination environment around Cu2+ cation of 7 is also square-bipyramidal (Fig. 2). The equatorial plane of 7 consists of a pair of monodentate 2,5-dimethyl-3-furanecarboxylato ligands bound through their carboxylato oxygen atoms [Cu1–O1 = 1.927(1) Å] and pair of neutral 3-pyridylmethanol molecules coordinated through their pyridine nitrogen atoms [Cu1–N1 = 2.020(2) Å] (Table 3) in trans positions. The axial positions are occupied by two hydroxyl oxygen atoms O3 [Cu1–O3v = Cu1–O3vi = 2.682(2) Å] from adjacent two molecules of 3-pyridylmethanol. The hydroxyl hydrogen atoms of 3-pyridylmethanol are bonded to the uncoordinated carboxylato oxygen atoms O2xi by hydrogen bonds O3– H3O···O2xi with interatomic O3···O2xi distance of 2.669(2) Ǻ (Table 3). The isostructural compounds 1–3, 5 and 6 and complex 7 form (4,4) networks. The bridging 3-pyridylmethanol ligand has been also observed in crystal structure of 1-D chain coordination polymer of 8 (Fig. 3B), which crystallizes in monoclinic centrosymmetric space group P21/c. The molecular structure of 8 with atomic-numbering scheme of independent part is shown in (Fig. 2). The copper(II) atom is bonded centrosymmetrically to two monodentate 5-nitro-2-furanecarboxylato anions through the oxygen atoms O1 [Cu1–O1 = 1.965(1) Å] and two 3-pyridylmethanol molecules bonded through the pyridine nitrogen atoms N1 [Cu1–N1 = 2.036(1) Å]. The coordination polyhedron of the copper(II) atom is completed by two oxygen atoms O3 of the neighbouring 3-pyridylmethanol hydroxyl groups [Cu1–O3vii = Cu1–O3viii = 2.466(1) Å] giving the distorted octahedral arrangement. A pair of 3-pyridylmethanol molecules bridges two of adjacent copper atoms (Fig. 2, 3B). As a result an infinite linear chain like “iron chain” of double bridges copper atoms parallel to a axis is formed in crystal structure of 8. The strong hydrogen bonds between each 3-pyridylmethanol hydroxyl group and the oxygen atom O2 of the uncoordinated carboxylato group of 5-nitro-2furanecarboxylato anions O3–H3O···O2xii with interatomic O3···O2xii distance of 2.676(3) Ǻ are observed (Table 3) in supramolecular synthon S(6) [36].

A)

B)

C) Fig. 3. Crystal structures: 2-D coordination network of 1–3, 5 and 6 (A), 1-D coordination chain of 8 (B) and 1-D supramolecular chain of 4 (C). On the other hand, the compound 4 crystallizes in triclinic space group P-1 and its crystal structure consists of centrosymmetric complex molecules of 4 (Fig. 2). The copper(II) atom of 4 is located on inversion centre and has elongated tetragonal bipyramidal (4+2) coordination geometry. The copper(II) atoms in basal plane are

bonded in a trans square-planar arrangement to two nitrogen atoms of two terminal 3pyridylmethanol molecules [Cu1–N1 = 1.992(3) Å] and one carboxylato oxygen atom from each of two 5-chloro-2-tiophenecarboxylato anions [Cu1–O1 = 1.995(2) Å]. The remaining two carboxylato oxygen atoms are somewhat weakly bonded to the copper(II) atom [Cu1–O2 = 2.524(3) Å] and lie at 57.18(9)ο from the normal to the CuO2N2 plane completing a tetragonal-bipyramidal stereochemistry around the copper centre. The complex molecules of 4 are linked through hydrogen bonds between disordered hydroxyl oxygen atoms O3A/O3B and carboxylato oxygen atoms O2x [O3A– H3A···O2x and O3A–H3A···O2x, with distances O3···O2 of 2.744(7) and 2.631(15) Å, respectively (Table 3)] into supramolecular infinite linear chain of double hydrogenbonding bridges in supramolecular rings R22(16) [42]. The 1-D hydrogen bonding supramolecular chain of 4 is depicted in Fig. 3C. The values of the tetragonality parameter T = RS/RL [37] for all complexes 1–8 are in the range 0.75–0.81 (Table 3), that indicates on the presence of tetragonal elongation of octahedron with further rhombic distortion around copper(II) atoms as a consequence of the Jahn-Teller distortion [37].

3.2. IR and electronic data Some characteristic bands in IR mid region of the sodium salts (2-tpcNa and 5Me-2-tpcNa), 3-pyme as well as the Cu(II) carboxylato complexes under study are given in Table 4. The broad bands assigned to antisymmetric and symmetric stretching vibration of carboxyl group for sodium salts as well as for thiophene- and furancarboxylate complexes are in the expected regions below 1600 and 1400 cm–1, respectively [38]. Antisymmetric νas(COO–) and symmetric νs(COO–) stretching vibration for copper(II) complexes in comparison with sodium salts are shifted to higher and lower wavenumbers, respectively. Very significant shift of νas(COO–) to higher wavenumber (1635 cm–1) for complex 8 is caused by the presence of electron-withdrawing nitro group.

Table 4 Infrared and electronic dataa (cm–1) for complexes 1–9. No.

Compound

1

2-tpcNa 5-Me-2-tpcNa 3-pyme [Cu(2-tpc)2(µ-3-pyme)2]n

2

Infrared data Carboxyl group COO νas(COO-) νs(COO-) 1552vs,br 1379vs,br 1558vs,br 1395vs,br

Electronic data

∆ (νas - νs)

Hydroxymethyl group CH2OH ν (O–H) ν (C–O)

Band I

16500

1567vs,brb

1377vs,br

190

3207vs, br 3100s, brb

[Cu(3-Me-2-tpc)2(µ-3-pyme)2]n

1557s

1351vs,br

206

3100s, brb

3

[Cu(5-Me-2-tpc)2(µ-3-pyme)2]n

1573vs,brb

1363vs,br

210

3080s,brb

4

[Cu(5-Cl-2-tpc)2(3-pyme)2]

1556s

1377vs,br

179

3311s,br

5

[Cu(2-fuc)2(µ-3-pyme)2]n

1558vs

1360vs,br

198

6

[Cu(3-fuc)2(µ-3-pyme)2]n

1571vs,brb

1367vs

7

[Cu(2,5-Me2-3-fuc)2(µ-3-pyme)2]n

1552vs

8

[Cu(5-NO2-2-fuc)2(µ-3-pyme)2]n

1635vs,br

9

[Cu3(2-Clnic)6-(µ-3-pyme)4(3-pyme)2]nc

1629s 1382vs,br 247 3334s,br 15800 1605vs 223 3116s,brb b Mixed bands or some of the observed bands belonging to another vibrational mode.

a

vs, very strong; s, strong; br, broad, sh, shoulder.

c

Reference [4].

Band II

173 163

3110s,brb

1022vs,br 1048s 1032s 1049s 1032s 1040s 1032s 1056s 1032m 1042s,br

17700 14300sh 16100

204

3110s,brb

1050s,br

16700

1324vs

228

3130s,brb

1021vs,br

17100

1343vs,brb

292

3120s,brb

1048s 1020s 1065vs

15400

16950

29400sh

16200

26000sh

26300sh

Moreover, the relationship between ∆ (the difference between the wavenumbers of the asymmetric – νas and the symmetric – νs stretches of the carboxylato group from IR spectra) and the type of coordination of the COO− group to metal ions is well known [38, 39]. For sodium 2-thiophencarboxylato as well as for sodium 5-methyl-2thiophencarboxylato the ∆ values are 173 and 163 cm–1, respectively. The much greater ∆ values from 190 to 292 (Table 4) for all complexes (except for coordination compound 4) are typical for unidentate coordination of the carboxyl groups. On the other hand, the lower value of ∆ (179 cm–1) for coordination compound 4 indicates that both carboxyl groups are probably coordinated asymmetrically in a chelating manner. The suggested unidentate O-coordination as well as asymmetrically chelating O,O’-coordination of carboxylato groups is in agreement with the structures determined by X-ray analysis. The most characteristic bands in the IR spectra of primary alcohols are stretch vibration bands assigned to ν(O–H) and ν(C–O). For primary alcohols in which O–H group is not involved in hydrogen bonds, the band assigned to ν(OH) is observed above 3630 cm [40]. Polymeric self-association through hydrogen bonds which is normally found in hydroxyl compounds gives rise to absorption bands in the range 3400 – 3200 cm-1. In fact, in the IR spectrum of liquid 3-pyme (Table 4 and Fig. 4) a broad band at 3207 cm-1 is assigned to ν(OH). In the IR spectra of all polymeric complexes 1-3 and 5-9, we observe the shift of bands assigned to O–H valence vibration to lower wavenumbers by about 100 cm–1 in comparison to “free” 3-pyme (Table 4 and Fig. 4). This shift is caused by the coordination of the oxygen atom of the hydroxymethyl group to CuII atom of bridging ligand 3-pyme. Moreover, a hydrogen atom of the hydroxymethyl group is involved in intramolecular hydrogen bond with the non-coordinated oxygen atom of the carboxyl group (see crystal structures). On the other hand, position of band assigned to O–H valence vibration at 3311 cm-1 (Table 4 and Fig. 4) for mononuclear complex [Cu(5-Cl-2-tpc)2(3-pyme)2] (4) indicates that monodentate 3-pyme is not coordinated through oxygen atom but only through nitrogen atom of pyridine ring. In the IR spectrum of polymeric complex [Cu3(2Clnic)6-(µ-3-pyme)4(3-pyme)2]n (9), we observe the broad bands at 3334 cm-1 and 3116 cm-1 assigned to O–H valence vibration of non-coordinated as well as coordinated hydroxymethyl

group

of

monodentate

and

bridging

3-pyme,

respectively.

Fig. 4 IR spectra for the 3-pyridinemethanol (3-pyme), [Cu(2-tpc)2(µ-3-pyme)2]n (1), [Cu(5-Cl-2-tpc)2(3-pyme)2] (4) and [Cu3(2-Clnic)6-(µ-3-pyme)4(3-pyme)2]n (9) ν(OH) – stretching vibration of the hydroxyl group.

Moreover, there is a shift of bands corresponding to pyridine ring deformation o 3-pyme (in plane as well as out of plane) to higher wavenumbers. This shows that 3pyme is coordinated via the nitrogen atom of the pyridine ring in all coordination compounds under study [38]. The solid state electronic spectra of the copper(II) complexes exhibit a broad ligand field band with a maximum range from 17 700 cm-1 to 15 400 cm-1 (Table 4). These types of d–d spectra are typical for tetragonally distorted octahedral arrangement around copper(II), corresponding to electron transfer from the one-electron orbital ground state dx2-y2 [41]. For coordination polymers 2, 5 and 7, there is also a charge transfer band (band II), attributed to a charge transfer band of the LMCT transition [41, 42].

3.3. EPR and magnetic data EPR powder data of all complexes under study were measured at room temperature and are collected in Table 5. Powder EPR spectra of presented coordination polymers revealed EPR signals that are typical for S = ½ system of either pseudoisotropic (1‒3 and 5) or axial symmetry (6‒8). Table 5 Room temperature EPR parameters for complexes 1-8. Complex 1 2 3 4 5 6 7 8

type of EPR signal Axial single asymmetric line single asymmetric line Axial single asymmetric line Axial Axial Axial with resolved hyperfine splitting G = (gǀǀ ‒ 2) / (g⊥ ‒ 2)

g tensor g⊥ =2.072 gǀǀ = 2.298 G = 4.14 gi =2.077 δHpp = 7,5 mT δHpp = 8,8 mT gi =2.074 g⊥ =2.062 gǀǀ2.288 G = 4.65 δHpp = 10,8 mT gi =2.052 g⊥ =2.079 gǀǀ = 2.305 G = 3.86 g⊥ =2.067 gǀǀ = 2.265 G = 3.96 g⊥ =2.059 gǀǀ = 2.297 A|| = 15,6 mT G = 5.03

Representative examples of observed spectra are presented on Fig. 5. Pseudoisotropic spectra of coordination polymers 1-3 and 5 show rather broad asymmetric EPR line characterised by only one g value (Fig. 5a). When a computer simulation of pseudoisotropic spectrum of 1 was done using the axial symmetry model (g⊥ =2.072, gǀǀ =

2.298), we have obtained relatively good agreement with experiment indicating that the real symmetry of EPR signal is an axial (Fig. 5a). The presence of unresolved pseudoisotropic EPR signal in polymeric copper (II) complexes is relatively typical [43]. a)

b)

exp

exp sim

sim

240

280

c)

320

360

400

B / mT

240

280

320

360

400

B / mT

exp

sim

240

280

320

360

400

B / mT

Fig. 5. Experimental room temperature powder EPR spectrum of a) 1 b) 4 c)

8

paired

with their simulations. For polymeric complexes 6-8 as well as for monomeric complex 4 the axial character of EPR spectra is observed (Fig. 5b) giving the values of g⊥, g|| within range 2.059 ‒ 2.305 that are consistent with slightly elongated tetragonal-bipyramidal stereochemistry around copper atom. Also the values of parameter G which varied within range 3.86 ‒ 5.03 correlate well with this stereochemistry showing only negligible exchange interaction between copper atoms. In addition, in case of coordination polymer 8, copper hyperfine splitting (ICu = 3/2) in parallel part of EPR signal is observed (Fig. 5c).

Magnetic investigations

The magnetic behavior of polymeric complexes composed from infinite chains 1-3, 5-7 as well as monomeric complex 4 were investigated in this study. Experimental magnetic data of representative examples 1 and 4 are depicted in Fig. 6. a) 2

3 2

0.5

-6

1

Mmol/(NA µB)

3

-1

χmol /(10 m mol )

µeff/µB

1.0

1 0 0

20

40

0

0.0 0

50

100

150

200

250

300

0

1

2

3

4

5

6

7

5

6

7

B/T

T/K

b) 2

Mmol/(NAµB )

0.4 χmol/(NA µB)

µeff/µB

1.0

1

0.3

0.5

0.2 0.1 0.0 0

20

40

0

0.0 0

50

100

150 T/K

200

250

300

0

1

2

3

4

B/T

Fig. 6. Magnetic data for a) 1 and b) 4. Left: Temperature dependence of the effective magnetic moment. Inset: temperature dependence of molar susceptibility. Right: field dependence of magnetization at T = 2.0 and 4.6 K. Empty circles: experimental points. Full line: the Brillouin law for isolated copper(II) ion. As can be seen from Fig. 6, magnetic behavior of coordination compounds under study is very similar in both cases. The room temperature values of the effective magnetic moment µeff are equal to 1.893 for polymeric 1 µB and 1.862 µB for monomeric 4. These values are close to the theoretical spin only value of 1.73 µB corresponding to

noninteracting copper centers with S = ½. The values of effective magnetic moment remain almost constant down to 6 K for 1 and 4 K for 4, when it starts to decrease to reach 1.78 µB for 1 and 1.82 µB for 4 respectively. Magnetic data obey the Curie-Weiss law perfectly in the whole temperature range (Table 6) as can be seen from the fitting of inverse susceptibility (not shown). Negligible and negative values of the Weiss constant are in accordance with the decrease of effective magnetic moment below 6 K, resp 4 K in case of 1 resp. 4. Table 6 Magnetic parameters and magnetization data. Effective magnetic momentsb µ B (B.M.)

Curie constantc C 3 (cm K mol–1)

Weiss constantc

Magnetizationd

Complex

DiaMa (×106 cm3 mol–1)

Θ

(B.M.)

1

–182

1.89

0.415

‒ 0.03

0.99

2

–207

1.81

0.420

‒ 0.03

1.00

3

–207

1.82

0.428

‒ 0.05

1.02

4

–212

1.86

0.394

‒ 0.10

0.97

5

–179

1.80

0.418

‒ 0.04

1.00

7

–204

1.80

0.406

‒ 0.05

0.98

a d

(K)

Diamagnetic corrections. b At 300 K. c In the temperature range 1.8 - 300 K. At the magnetic field 1 T and temperature 2 K.

Magnetic data for monomeric complex 4 were evaluated using monomeric model with molecular field correction using Hamiltonian in the form Hˆ = µ B gBSˆz − zj Sˆz Sˆz . Best fit parameters resulted in following parameters: g = 2.15 and zj/hc = –0.032 cm-1.

4. Conclusions Ambidentate 3-pyridylmethanol can be used in the synthesis of coordination compounds as a flexible N,O − bridging ligand that can directly form a polymeric structure or as a “ terminal N − donor ligand. In the latter case 3-pyridylmethanol

simultaneously act as “supramolecular reagent”, that is able to create supramolecular frameworks through the combination of coordination and hydrogen bonds. We report here the preparation and characterization 8 new polymeric (1–3, 5− −8) and monomeric (4) copper(II) thiophene- and furancarboxylato complexes with 3-pyridylmethanol. The crystal structures of coordination polymers contain either 2-D (1–3, 5 and 6, 7) or 1-D (8) layers with strong intramolecular bonds. In case of monomeric 4, molecular units are organized into to 1-D supramolecular chains due to the strong intermolecular hydrogen bonds. The complexes were studied by single crystal X-ray diffraction, IR, Uv-VIS, elemental, EPR and magnetic measurements. IR spectral analysis of polymeric and monomeric complexes revealed that position and shape of O–H valence vibration of 3pyridylmethanol allow us to distinguish between N,O − bridging motif (polymeric structure) and N−monodentate (monomeric structure) coordination of 3-pyme.

Appendix A. Supplementary data Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication nos. CCDC-910188–910195. Copies of the data can be obtained free of charge on application to the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: (internat.) +44 1223/336033; e-mail:[email protected]].

Acknowledgements Financial support received from Slovak Grant Agencies under grant no. APVV14-0078 and VEGA 1/0056/13, 1/0388/14 and 1/0765/14.

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