Synthesis and crystal structure of Mn(II) complexes with novel macrocyclic Schiff-base ligands containing piperazine moiety

Polyhedron 27 (2008) 3172–3176

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Synthesis and crystal structure of Mn(II) complexes with novel macrocyclic Schiff-base ligands containing piperazine moiety Hassan Keypour a,*, Majid Rezaeivala a, Laura Valencia b, Paulo Pérez-Lourido b a b

Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran Departamento de Química Inorgánica, Facultad de Química, Universidade de Vigo, 36310 Vigo, Pontevedra, Spain

a r t i c l e

i n f o

Article history: Received 12 June 2008 Accepted 8 July 2008 Available online 25 August 2008 Keywords: Piperazine Asymmetric macrocyclic Schiff base Manganese(II) complexes X-ray crystal structure

a b s t r a c t A series of Mn(II) macrocyclic Schiff-base complexes [MnLnCl]+ (n = 1–4) have been prepared via the Mn(II) templated [1+1] cyclocondensation of 2,6-diacetylpyridine or 2,6-pyridinedicarbaldehyde with the symmetrical 1,4-bis(3-aminopropyl)piperazine or the novel asymmetrical N,N0 (2-aminoethyl)(3-aminopropyl)piperazine linear amines containing piperazine moiety. The complexes have been characterized by elemental analyses, IR, FAB-MS, magnetic studies and conductivity measurements. The crystal structure of [MnL2(CH3OH)Cl](ClO4) and [MnL4Cl](PF6) complexes have also been determined showing the metal ion in a N4OCl pentagonal bipyramidal or N4Cl highly distorted octahedral geometry, respectively. Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction During last decades, considerable interest in coordination chemistry has been centered on the role of metal ions as templates in the cyclization and condensation reactions which produce complexes of macrocyclic ligands [1]. The stability of macrocyclic metal complexes depends upon a number of factors, including the number and type of the donor atoms present in the ligand and their relative positions within the macrocyclic skeleton, as well as the number and size of the chelate rings formed on complexation. For transition metal ions, features such as the nature and magnitude of crystal-field effects play also an important role [2]. In recent years, asymmetric macrocyclic ligands have been extensively studied, as these systems present sometimes two dissimilar metal-binding sites with respect to the cavity size, coordination number or the nature of donor atoms, so they can form heterodinuclear complexes with suitable metal ions [3,4]. These systems can be used in the selective coordination of two different metal ions. Studies on the magnetic properties of these complexes have significantly helped in advancing the understanding of spin-exchange mechanisms, relating them to the geometries and to the ground state electronic configurations of the constituting metal ions [5]. The coordination chemistry of manganese macrocyclic complexes has achieved remarkable progress due to the increased recognition of the Mn(II) function in biological systems [6,7]. The * Corresponding author. Tel.: +98 811 8282807; fax: +98 811 8257407. E-mail address: [email protected] (H. Keypour). 0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2008.07.012

importance of manganese in photosynthesis is well known [8]. Although its detailed function in the photosynthetic process remains obscure, it has been established that the metal plays an important role in the oxygen evolution part of the cycle. On this basis, Calvin proposed that a manganese porphyrin complex having the metal in a high oxidation state –Mn(IV)– may be involved in dioxygen binding in photo system II. With the emphasis on a manganese–dioxygen interaction and the attainment of a high oxidation state of the metal a number of model systems have been explored [9,10]. On the other hand, the piperazine offers an aliphatic nitrogen-containing building block [11–19]. Piperazine itself is a good hydrogen-bond acceptor, which, together with its metal complexing capabilities, makes it an interesting moiety for supramolecular complex chemistry [20]. We have been interested for some time in the design and synthesis of new macrocyclic Schiff-base complexes, particularly in the synthesis of CR-type ones [21,25]. These complexes are mainly formed by metal ion templated cyclocondensation of 2,6-diacetylpyridine and a [1+1] linear triamine or tripodal tetraamine [22–24]. We have also recently reported a number of new manganese(II) Schiff-base macrocyclic complexes, by the Mn(II) templated [1+1] cyclocondensation of 2,9-dicarboxaldehyde-1,10-phenantroline and different polyamines [26]. As an extension of this idea, we report in this work the Mn(II) templated [1+1] cyclocondensation of 2,6-diacetylpyridine or 2,6pyridinedicarbaldehyde with two different linear tetraamines having a piperazine moiety, the new asymmetrical N,N0 (2-aminoethyl)(3-aminopropyl)piperazine and the 1,4-bis(3-aminopropyl)piperazine.

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R O

H2N

R

(CH2)m

Mn2+

+

N

(CH2)m

N

N

N

Mn2+

N

MeOH N O

H2N

N

(CH2)n

N

(CH2)n

R

R

L1 L2 L3 L4

m 2 2 3 3

n 3 3 3 3

R H CH 3 H CH3

Scheme 1. The template condensation between 2,6-diacetylpyridine or 2,6-pyridinedicarbaldehyde and two linear tetraamines with piperazine moiety in the presence of Mn(II).

In all cases, the [1+1] template cyclocondensation occurs and the metal complexes of the 16-, and 17-membered pentaaza macrocycles L1–L4 were obtained. The template cyclocondensation involving the N,N0 (2-aminoethyl)(3-aminopropyl)piperazine precursor give rise to Mn(II) complexes of the asymmetrical macrocycles L1 and L2, whilst with the 1,4-bis(3-aminopropyl)piperazine amine, the Mn(II) complexes of L3 and L4 were obtained. The Mn(II) complexes recorded in Scheme 1 have been obtained. The crystal structures of [MnL2Cl(CH3OH)](ClO4) and [MnL4Cl](PF6) are also reported.

O

O O

O

N

NH

NH

160 º C O

7

NH2

i) Br H2N 4

6

5'

O

·4HCl 4'

N

N

1

5

N

2,6-Pyridinedicarbaldehyde was prepared according to the literature method [27]. 2,6-Diacetylpyridine, 1,4-bis(3-aminopropyl)piperazine and the metal salts were commercial products (from Merck, Aldrich and Fluka, respectively) and were used without further purification. Solvents were of reagent grade purified by the usual methods. Caution: Perchlorate salts are potentially explosive. While we have not experienced any problems with the compounds described, they should be treated with caution and handled in small quantities.

O

180 Ο C

N

2. Experimental 2.1. Chemical and starting materials

N

NH2

2

ii) HCl

3

Scheme 2. The processes of synthesis of N,N0 (2-aminoethyl)(3-aminopropyl)piperazine. 1 H NMR (D2O, ppm) d = 2.26 (m, 2H, 2-H); 3.18 (t, 2H, 3-H); 3.50 (t, 2H, 1-H); 3.58 (t, 2H, 6-H); 3.73 (t, 2H, 7-H); 3.85 (br, 8H, 4,40 and 5,50 -H). 13C NMR (D2O, ppm) d = 21.75 (C-2); 33.8 (C-6); 36.40 (C-3); 49.01, 49.35 (C-4,40 and 5,50 ); 52.81 (C-7); 53.64 (C-1).

2.3. Synthesis of the metal complexes – general procedure 2.2. Synthesis of N,N0 (2-aminoethyl)(3-aminopropyl)piperazine 2-Aminoethylpiperazine (2.58 g, 20 mmol) and phthalic anhydride (2.96 g, 20 mmol) were mixed in appropriate beaker and fused at 180 °C with constant stirring for 15 min. After lowering the temperature (at about 160 °C), N-(3-bromopropyl) phthalimide (5.36 g , 20 mmol) was also added and fused together at with constant stirring for 30 min. The resulting solid was washed two steps with hot ethanol, pulverized and heated under reflux with HCl (300 ml, 25%) for 12 h. The phthalic acid which formed on cooling was filtered off and the filtrate evaporated to small bulk and poured into absolute ethanol. The resulting viscous precipitate was recrystallized from EtOH/H2O, washed with a small amount of cooled absolute ethanol and diethyl ether, and the resulting yellow powder was dried and characterized as the pure compound (Scheme 2). Yield: 3.15 g (45%). Anal. Calc. for C9H28Cl4N4O (MW: 348.1): C, 30.9; H, 8.1; N, 16.0. Found: C, 30.7; H, 8.2; N, 16.1%. FAB-MS (m/z): 187 [M+1]+.

All macrocyclic complexes were prepared according to the literature method [28]. A solution of NaOH (2 mmol) in absolute ethanol (10 ml) was added to a suspension of the appropriate tetramine salt (0.5 mmol) in absolute ethanol (10 ml). The mixture was stirred at room temperature for a few minutes then filtered, and the precipitate was washed well with absolute ethanol (10 ml). The washings and the filtrate were combined and this solution was added dropwise to a hot solution of Mn(ClO4)2  xH2O (0.5 mmol) and 2,6-diacetylpyridine or 2,6-pyridinedicarbaldehyde (0.5 mmol) in absolute methanol (20 ml), over a period of 2 h. After refluxing the solution for 24 h it was filtered. Crystalline compound was obtained by slow diffusion of diethyl ether vapour into the MeOH/MeCN solution of the above solid. 2.3.1. [MnL1Cl (CH3OH)](ClO4) Anal. Calc. for C16H25Cl2MnN5O5 (MW: 492.06): C, 39.0; H, 5.1; N, 14.2. Found: C, 39.2; H, 5.0; N, 14.1%. Yield: 45%. IR (KBr,

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cm1) 3444, 1650, 1632 [m(C@N)], 1588, 1465 [m(C@C) and m(C@N)]py, 1107, 625 m(ClO4  ). FAB-MS (m/z, %): 375 (100%), [MnL1Cl]+. KM/X1 cm2 mol1 (in DMF): 157 (2:1). 2.3.2. [MnL2Cl(CH3OH)](ClO4) Anal. Calc. for C18H29Cl2MnN5O5 (MW: 520.09): C, 41.5; H, 5.6; N, 13.5. Found: C, 41.2; H, 5.5; N, 13.3%. Yield: 50%. IR (KBr, cm1) 3463, 1648, 1633 [m(C@N)], 1585, 1487 [m(C@C) and m(C@N)]py, 1110, 625 m(ClO4  ). FAB-MS (m/z, %): 403(100%), [MnL2Cl]+. KM/X1 cm2 mol1 (in DMF): 172 (2:1). 2.3.3. [MnL3Cl](ClO4) Anal. Calc. for C17H25Cl2MnN5O4 (MW: 488.07): C, 41.7; H, 5.1; N, 14.3. Found: C, 41.3; H, 5.2; N, 14.1%. Yield: 47%. IR (KBr, cm1) 3418, 1643 [m(C@N)], 1592, 1462 [m(C@C) and m(C@N)]py, 1110, 625 m(ClO4  ). FAB-MS (m/z, %): 389(100%), [MnL3Cl]+. KM/ X1 cm2 mol1 (in DMF): 120 (2:1). 2.3.4. [MnL4Cl](ClO4)  2H2O, [MnL4Cl](PF6) Anal. Calc. for C19H33Cl2MnN5O6 (MW: 552.12): C, 41.3; H, 6.0; N, 12.7. Found: C, 41.4; H, 5.9; N, 12.7%. Yield: 40%. IR (KBr, cm1) 3441, 1634 [m(C@N)], 1589, 1451 [m(C@C) and m(C@N)]py, 1089, 624 m(ClO4  ). FAB-MS (m/z, %): 477(100%), [MnL4Cl]+. KM/ X1 cm2 mol1 (in DMF): 143 (2:1). Recrystallization of 0.5 g of the above compound in methanol in the presence of an excess of NH4PF6 gave brown needle orange crystals of [MnL4Cl](PF6). Anal. Calc. for C19H31ClF6MnN5OP (MW: 580.12): C, 39.3; H, 5.4; N, 12.1. Found: C, 39.5; H, 5.3; N, 11.9%. Yield: 75%. 2.4. Physical measurements Elemental analyses were performed in a Carlo-Erba EA microanalyser. FT-IR spectra in the 4000–400 cm1 region were recorded from KBr pellets on Bruker VECTOR 22 and Perkin–Elmer GX spectrophotometers. FAB mass spectra were recorded using a Kratos-MS-50T spectrometer connected to a DS90 data system using 3-nitrobenzyl alcohol as the matrix. Magnetic susceptibility measurements were performed at 25 °C using a Johnson Matthey Alfa MSBMKI Gouy balance. Conductivity measurements were carried out in 103 mol dm3 dimethylformamide solutions at 20 °C using a CARISON GLP32 conductivimeter. 1H and 13C NMR spectra were recorded on a Bruker 500 MHz using D2O as solvent. 2.5. X-ray crystal structure determination Vapour diffusion of diethyl ether into a solution of [MnLnCl]+ (n = 2 and 4) in mixture of acetonitrile and methanol, afforded crystal suitable for study by X-ray crystallography. The details of the Xray crystal data, and of the structure resolution and refinement, are given in Table 1. Measurements were made on a Bruker SMART CCD area diffractometer. All data were corrected for Lorentz and polarization effects. Empirical absorption corrections were also applied for all the crystal structures obtained [29]. Complex scattering factors were taken from the program package SHELXTL [30]. The structures were solved by direct methods which revealed the position of all non-hydrogen atoms. All the structures were refined on F2 by a full-matrix least-squares procedure using anisotropic displacement parameters for all non-hydrogen atoms. The hydrogen atoms were located in their calculated positions and refined using a riding model. Molecular graphics were generated using ORTEP-3 [31]. 3. Results and discussion The new asymmetric amine N,N0 (2-aminoethyl)(3-aminopropyl)piperazine was readily prepared starting from 2-aminoethyl-

Table 1 Crystal data and structure refinement for [MnL2Cl(CH3OH)](ClO4) and [MnL4Cl]PF6

Empirical formula Formula weight Temperature (K) Wavelength (Å) Crystal system Space group Unit cell dimensions a (Å) b (Å) c (Å) a (°) b (°) c (°) V (Å3) Z Dcalc (Mg/m3) Absorption coefficient (mm1) F(0 0 0) Crystal size (mm3) h Range for data collection (°) Index ranges

Reflections collected Independent reflections (Rint) Completeness to h Absorption correction Maximum and minimum transmission Refinement method Data/restraints/parameters Goodness-of-fit on F2 Final R indices [I > 2r(I)] R indices (all data) Largest difference in peak and hole (e Å3)

[MnL2Cl(CH3OH)]ClO4

[MnL4Cl]PF6

C19H30N5O5Cl2Mn 534.32 293(2) 0.71073 triclinic  P1

C19H29N5PF6ClMn 562.83 293(2) 0.71073 monoclinic P21/c

7.1963(15) 11.437(2) 14.829(3) 79.894(4) 83.110(4) 81.545(4) 1182.9(4) 2 1.500 0.824 556 0.43  0.36  0.19 1.40–28.06 9 6 h 6 5, 14 6 k 6 14, 18 6 l 6 19 7812 5445 (0.0308) 94.7% (28.06°)

12.6286(15) 15.4112(19) 12.5828(16) 103.797(3) 2378.2(5) 4 1.572 0.799 1156 0.37  0.35  0.30 1.66–28.03 16 6 h 6 12, 18 6 k 6 20, 11 6 l 6 16 15 349 5648 (0.0579) 98.0% (28.03°)

SADABS

SADABS

0.8592 and 0.7183

0.7955 and 0.7564

full-matrix leastsquares on F2 5445/0/292 1.024 R1 = 0.0808, wR2 = 0.2269 R1 = 0.1458, wR2 = 0.2780 1.386 and 0.998

full-matrix leastsquares on F2 5648/24/340 1.005 R1 = 0.0487, wR2 = 0.1115 R1 = 0.1379, wR2 = 0.1482 0.426 and 0.307

piperazine, phthalic anhydride and N-(3-bromopropyl) phthalimide in a 45% yield. The FAB mass spectra confirm the presence of the desired final product as it shows a peack at m/z 187 belonging to the protonated amine. The Schiff-base macrocyclic complexes [MnLnCl]+ (n = 1–4) were prepared from [1+1] cyclocondensation of 2,6-diacetypyridine or 2,6-pyridinedicarbaldehyde and the amine salts of 1,4-bis(3-aminopropyl)piperazine or N,N0 (2-aminoethyl)(3-aminopropyl)piperazine. The complexes were characterised by elemental analyses, IR, FAB-MS, magnetic properties and conductivimetry measurements. The solid compounds are air stable and elemental analyses are consistent with the formulations given in Section 2. All of the complexes exhibit a m(C@N) vibration in the range 1633–1650 cm1 and also bands at approximately 1600 and 1450 cm1 associated with m(C@N)py and m(C@C) vibrations from the pyridine and phenyl rings [32]. However no bands are observed for the free carbonyls or primary diamines, indicating that complete condensation has occurred. The IR spectrum of [MnL4Cl](ClO4)  2H2O is consistent with the presence of water molecules accordingly with the microanalytical data. For the perchlorate complexes, absorptions attributable to perchlorate ions were found at approximately 1100 and 625 cm1 [33]. The lack of splitting of these bands suggests that the perchlorate anions are not coordinated [34]. The molar conductance values of the complexes measured in dimethylformamide lie in the range reported for 2:1 electrolytes in this solvent [35].

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Positive-ion FAB mass spectrometry provided further evidence for cyclocondensation and the formation of di-imine complexes. The spectra show that most intense peaks are observed at m/z 375, 403, 389 and 477 a.m.u. corresponding to [MnLn(Cl)]+ (n = 1–4), respectively. The values of the room temperature magnetic moment of the complexes, 5.44, 5.53, 5.59 and 5.54 BM for [MnL1Cl]+, [MnL2Cl]+ , [MnL3Cl]+and [MnL4Cl]+, respectively are indicative of high-spin Mn(II) in all cases [36]. The high-spin Mn(II) ion possesses a halffilled 3d-shell and thus the coordination geometries of its complexes are not subject to ligand field effects and are determined mainly by the chelating power and geometrical arrangement of the ligands. 3.1. Crystal structures The crystal structure of the two Mn(II) complexes with formula [MnL2Cl(CH3OH)](ClO4) and [MnL4Cl](PF6) have been determined by X-ray diffraction. The projection view of the molecular structures of the cationic unit present in the complexes with nonhydrogen atoms represented by 50% thermal ellipsoids are shown in Figs. 1 and 2, respectively, together with selected bond lengths and angles relating to the coordination environment of the metal (Table 2). The [MnL2Cl(CH3OH)](ClO4) complex crystallizes in the triclinic  space group and shows that the metal atom is seven coordiP1 nated in a pentagonal bipyramidal geometry, arising from coordination by the five N atoms of the macrocycle, one chloride ion and one oxygen atom from a methanol molecule. A similar seven coordinate geometry has been found for other Mn(II) complexes with N5 macrocyclic ligands [37,38]. The ligand shows a nearly plane conformation, and the rms of the plane formed by the five N atoms is 0.0756, showing that these atoms are almost coplanar, with the Mn(II) ion 0.0942 Å out of this plane. The sum of the five N–Mn–N chelate angles (359.96°) is almost 360° for an ideal planar structure. The Cl and O donor atoms are sited trans to the macrocyclic plane, with an angle Cl–Mn–O of 170.19(13)°, near to 180°. The five Mn–N bond lengths are in the range 2.246–2.346 Å, affording an average Mn–N bond distance of 2.321 Å. The Mn–Cl and Mn–

Fig. 1. Crystal structure of the cation [MnL2Cl(CH3OH)]+.

Fig. 2. Crystal structure of the cation [MnL4Cl]+.

Table 2 Selected bond lengths (Å) and bond angles (°) for [MnL2Cl(CH3OH)]+ (1) and [MnL4Cl]+ (2) Bond lengths (Å)

1

Bond lengths (Å)

2

Mn(1)–N(1) Mn(1)–N(2) Mn(1)–N(3) Mn(1)–N(4) Mn(1)–N(5) Mn(1)–O(1) Mn(1)–Cl(1)

2.246(4) 2.337(5) 2.346(6) 2.334(6) 2.344(5) 2.332(4) 2.521(17)

Mn(1)–N(1) Mn(1)–N(2) Mn(1)–N(3) Mn(1)–N(4) Mn(1)–N(5) Mn(1)–Cl(1)

2.250(3) 2.276(3) 2.352(3) 2.387(3) 2.286(3) 2.364(11)

Bond angle (°) N(1)–Mn(1)–N(2) N(1)–Mn(1)–N(3) N(1)–Mn(1)–N(4) N(1)–Mn(1)–N(5) N(2)–Mn(1)–N(3) N(2)–Mn(1)–N(4) N(2)–Mn(1)–N(5) N(3)–Mn(1)–N(4) N(3)–Mn(1)–N(5) N(4)–Mn(1)–N(5) O(1)–Mn(1)–N(1) O(1)–Mn(1)–N(2) O(1)–Mn(1)–N(3) O(1)–Mn(1)–N(4) O(1)–Mn(1)–N(5) O(1)–Mn(1)–Cl(1) N(1)–Mn(1)–Cl(1) N(2)–Mn(1)–Cl(1) N(3)–Mn(1)–Cl(1) N(4)–Mn(1)–Cl(1) N(5)–Mn(1)–Cl(1)

69.92(16) 147.2(3) 150.0(2) 139.29(19) 77.3(3) 138.4(2) 139.29(19) 62.1(3) 143.2(3) 81.1(2) 81.45(15) 85.34(17) 96.6(2) 90.1(2) 85.12(18) 170.19(13) 88.84(11) 92.69(12) 92.3(2) 97.70(19) 90.18(13)

Bond angle (°) N(1)–Mn(1)–N(2) N(1)–Mn(1)–N(3) N(1)–Mn(1)–N(4) N(1)–Mn(1)–N(5) N(2)–Mn(1)–N(3) N(2)–Mn(1)–N(4) N(2)–Mn(1)–N(5) N(3)–Mn(1)–N(4) N(3)–Mn(1)–N(5) N(4)–Mn(1)–N(5) N(1)–Mn(1)–Cl(1) N(2)–Mn(1)–Cl(1) N(3)–Mn(1)–Cl(1) N(4)–Mn(1)–Cl(1) N(5)–Mn(1)–Cl(1)

69.51(11) 127.48(10) 104.53(10) 68.94(11) 80.23(10) 130.03(11) 136.04(11) 64.47(10) 138.46(11) 740.70(10) 129.62(8) 99.71(8) 96.36(8) 117.53(8) 95.73(8)

O distances of 2.5214 and 2.332 Å, respectively, are within the range observed previously for this sort of complexes. The perchlorate ion is non-coordinating reflecting the low coordination ability of this anion. No intra- or intermolecular p,p-interactions have been observed in the net. The [MnL4Cl](PF6) complex crystallizes in the monoclinic P2(1)/ c space group, and the [MnL4Cl]+ cation shows the Mn(II) ion in a six coordinated environment into the macrocycle hole interacting

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with the five N donor atom of the ligand, whilst the sixth coordination position is occupied by one chloride ion. The geometry can be described as highly distorted octahedral, where the equatorial plane is comprised by N(1) N(2) N(3) N(5) donor atoms, being the apical positions occupied by the chloride ion and the N(4) donor atom. In this case, the [MnL4Cl]+ cation shows that the ligand is folded due to the presence of two propylene chains between the tertiary amine groups of the molecule, which give rise to a higher flexibility of L4 compared with L2. The rms of the equatorial plane is 0.4716 and the Mn(II) ion is 0.6838 Å out of this plane. The five Mn–N bond lengths vary from 2.250 to 2.286 Å, with average Mn-N bond distance of 2.310 Å, similar to previously reported six-coordinate manganese(II) complexes with this kind of ligands, and only 0.01 Å shorter than the average distance in the sevencoordinate complex [39]. The Mn(II) to chlorine distance [Mn(1)–Cl(1) 2.3646 Å], is slightly shorter than the Mn–Cl distances found previously in this sort of complex. The PF6  anion is disordered in four of the six fluoride ions of the counter ion with occupancies of 65% and 35% for the two components present. As in the previous complex no intra- or intermolecular p,pinteractions have been observed. 4. Conclusion The Mn(II) ion is effective as a template for the Schiff-base condensation of 2,6-diacetylpyridine or 2,6-pyridinedicarbaldehyde with two different tetraamines having a piperazine moiety. In spite of presence of steric hindrance due to structural restriction of piperazine, cyclocondensation has occurred and pentaaza macrocyclic complexes based on the [X]piperazine N5 rings (X = 16 and 17) were obtained. The crystal structures of [MnL2Cl(CH3OH)] (ClO4) and [MnL4Cl](PF6) were determined and indicate that in the solid state the complexes adopt a pentagonal bipyramidal and a highly distorted octahedral geometry, respectively. 5 Supplementary data CCDC 649842 and 686394 contain the supplementary crystallographic data for [MnL2Cl(CH3OH)](ClO4) and [MnL4Cl](PF6). These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: [email protected]. Acknowledgements We are grateful to the Faculty of Chemistry of Bu-Ali Sina University, Ministry of Science, Research and Technology of Iran, for financial support and to The University of Vigo for a Visiting Fellowship to M.R.

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