научная статья по теме SYNTHESIS, CRYSTAL STRUCTURES, AND ANTIBACTERIAL PROPERTY OF TRIS[2-(5-BROMOSALICYLIDENEAMINO)ETHYL]AMINE AND ITS MANGANESE(III) COMPLEX Химия

Текст научной статьи на тему «SYNTHESIS, CRYSTAL STRUCTURES, AND ANTIBACTERIAL PROPERTY OF TRIS[2-(5-BROMOSALICYLIDENEAMINO)ETHYL]AMINE AND ITS MANGANESE(III) COMPLEX»

КООРДИНАЦИОННАЯ ХИМИЯ, 2015, том 41, № 1, с. 28-33

УДК 541.49

SYNTHESIS, CRYSTAL STRUCTURES, AND ANTIBACTERIAL PROPERTY OF Tra[2-(5-BROMOSALICYLIDENEAMINO)ETHYL]AMINE AND ITS MANGANESE(III) COMPLEX © 2015 Y. M. Hao

Department of Chemistry, Baicheng Normal University, Baicheng, 137000 P.R. China

E-mail: jyxygzb@163.com Received June 13, 2014

A tripodal Schiff base tris [2-(5-bromosalicylideneamino)ethyl]amine (H3L) was prepared by the reaction of 5-bromosalicylaldehyde with ftis(2-aminoethyl)amine. Reaction with the Schiff base with manganese perchlorate in methanol resulted a mononuclear manganese(III) complex (I). The crystal structures of the Schiff base and the complex have been determined by single crystal X-ray diffraction (CIF files CCDC nos. 1007902 (H3L); 1007983 (I)). The Schiff base coordinates to the Mn atom through all the phenolate O and imino N atoms. The Mn atom of the complex is in octahedral coordination. The antibacterial properties have been tested on some bacteria and yeast.

DOI: 10.7868/S0132344X1501003X

INTRODUCTION

Schiff bases have been extensively used as ligands to construct complexes with various metal ions. In the last decades, numerous Schiff bases and their complexes have been prepared and studied their properties, such as magnetic [1—5], catalytic [6—10], luminescence [11], as well as biological applications [12—15]. Among the complexes, most are derived from mono- or bisSchiff bases. Tris(2-aminoethyl)amine is an interesting primary amine, which can react with aldehydes to form tripodal Schiff bases. During the search of literature, we find that the complexes derived from tri-Schiff bases are very rare. In this paper, a tripodal Schiff base iHs[2-(5-bromosalicyideneamino)ethyl]amine (H3L) and its manganese complex (I) were prepared, and studied on their antibacterial properties.

Br

Br

OH

(H3L)

EXPERIMENTAL

Materials and methods. Tris(2-aminoethy1)amine, 5-bromosalicylaldehyde, and manganese perchlorate were obtained from commercial sources and were used as received without further purification. Elemental analyses of C, H, and N were performed using a Perk-inElmer 240C elemental analyzer. IR spectra were recorded as KBr pellets using a Magna 750 FTIR spectrophotometer. 1H NMR was recorded on a Bruker 300 instrument.

Caution! Although we did not experience any problem with the compounds reported in this work, per-chlorate salts are potentially explosive. Only a small amount of material should be prepared, and it should be handled with care.

Synthesis of the tripodal Schiff base (H3L). 5-Bro-mosalicylaldehyde (6.03 g, 0.3 mol) was dissolved in 30 mL methanol, to which was added dropwise a metha-nolic solution (20 mL) of tris(2-aminoethyl)amine (1.46 g, 0.1 mol). The color changed from colorless to orange during the reaction procedure. The reaction was continued for 30 min, and the solvent was allowed to slow evaporate in air. Yellow single crystals were obtained in 5 days. The yield was 73%. IR (KBr; v, cm-1): 1645 v (C=N). 1H NMR data (300 MHz; DMSO; 8, ppm): 13.61 (s., 3H), 8.37 (s., 3H), 7.73 (s, 3H), 7.38 (d.d., J = 8.8, 2.4 Hz, 3H), 6.77 (d., 3H), 3.62 (t., 6H), 2.76 (t., 6H).

For C27H27N4O3Br3

anal. calcd., %: Found, %:

C, 46.64; C, 46.83;

H, 3.91; H, 4.00;

N, 8.06. N, 7.95.

Table 1. Crystallographic data and refinement parameters for the Schiff base (H3L) and complex I

Table 2. Selected bond distances (A) and angles (deg) for the Schiff base (H3L) and complex I

Value Bond d, Â Bond d, Â

Parameter

H3L I H3L

Fw 695.26 747.17 C(7)—N(1) 1.279(3) C(16)-N(2) 1.275(3)

Crystal system Triclinic Triclinic C(25)-N(3) 1.274(3) C(9)-N(4) 1.466(3)

Space group P1 p1 C(18)-N(4) 1.469(3) C(27)-N(4) 1.464(3)

a, A 9.8562(3) 9.5479(5) I

b, A 11.9170(5) 11.7796(6) C(7)-N(1) 1.283(9) C(16)-N(2) 1.283(9)

c, A 13.2324(4) 13.3841(8) C(25)-N(3) 1.282(8) C(9)-N(4) 1.468(10)

a, deg 89.269(3) 79.750(2) C(18)-N(4) 1.442(9) C(27)-N(4) 1.438(9)

P, deg 77.229(3) 78.680(2)

Mn(1)-O(1) 1.908(5) Mn(1)-O(2) 2.098(5)

Y, deg 67.500(3) 88.647(2)

1395.94(8) 1452.4(1) Mn(1)-O(3) 1.882(4) Mn(1)-N(1) 2.355(6)

V, A3

Z 2 2 Mn(1)-N(2) 2.068(5) Mn(1)-N(3) 2.069(5)

P calcd g cm-3 1.654 1.709 Angle ro, deg Angle ro, deg

p., mm-1 4.370 4.616 I

X, A 0.71073 0.71073 O(3)Mn(1)O(1) 89.5(2) O(3)Mn(1)N(2) 169.6(2)

F(000) 692 736

O(1)Mn(1)N(2) 84.2(2) O(3)Mn(1)N(3) 88.7(2)

Measured reflections 22872 13153

O(1)Mn(1)N(3) 171.3(2) N(2)Mn(1)N(3) 98.8(2)

Unique reflections 5720 5112

Observed reflections 4790 3786 O(3)Mn(1)O(2) 86.8(2) O(1)Mn(1)O(2) 100.8(2)

GOOF (F2) 1.017 1.049 N(2)Mn(1)O(2) 86.3(2) N(3)Mn(1)O(2) 87.6(2)

Parameters 343 343 O(3)Mn(1)N(1) 83.7(2) O(1)Mn(1)N(1) 82.5(2)

Restraints 0 0 N(2)Mn(1)N(1) 103.6(2) N(3)Mn(1)N(1) 88.8(2)

R1, wR2 (all data) 0.0271, 0.0544 0.0865, 0.2141 O(2)Mn(1)N(1) 169.9(2)

R1, wR2 (I> 2ct(I)) 0.0376, 0.0583 0.0624, 0.1958

Synthesis of I. Manganese perchlorate hexahydrate (1.81 g, 0.05 mol) and the tripodal Schiff base (3.48 g, 0.05 mol) were mixed in methanol, and stirred at room temperature for 30 min to give brown solution. The solution was kept still to slow evaporate in air for several days, to form well block-shaped single crystals. The yield was 41%. IR (KBr; v, cm-1): 1615 v(C=N).

For C27H24N4O3Br3Mn

anal. calcd., %: Found, %:

C, 43.40; C, 43.23;

H, 3.24; H, 3.31;

N, 7.50. N, 7.62.

X-ray crystallography. Single crystal X-ray data for the tripodal Schiff base and the manganese complex

were collected on a Bruker SMART APEX CCD dif-fractometer using the SMART/SAINT software [16]. Intensity data were collected using graphite-mono-chromatized MoKa radiation (0.71073 A) at 293(2) K. The structures were solved by direct methods using the SHELX-97 program [17]. Empirical absorption corrections were applied with SADABS [18]. All non-hydrogen atoms were refined with anisotropic displacement coefficients. The hydrogen atoms bonded to carbon and nitrogen were included in geometric positions and given thermal parameters equivalent to 1.2 times those of the atom to which they were attached. Crys-tallographic data and refinement parameters are given in Table 1, and important interatomic distances and angles are given in Table 2.

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30

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Table 3. Geometrical parameters for hydrogen bonds for H3L and I*

D H-A Distance, A Angle D H-A, deg

D-H H-A D-A

H3L

O(1)-H(1)-N(1) 0.80(3) 1.81(3) 2.553(2) 153(3)

O(2)-H(2)-N(2) 0.82(3) 1.84(3) 2.593(3) 151(3)

O(3)-H(3)-N(3) 0.78(3) 1.91(3) I 2.51 2.611(2) 150(3)

C(16)-H(16)-O(1) 0.93 3.338(5) 148

* Symmetry transformation used to generate the symmetry related atoms: i - x, -y, - z.

Supplementary material for structures H3L and I have been deposited with the Cambridge Crystallographic Data Centre (nos. 1007902 (H3L); 1007983 (I); depos-it@ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk).

Biological assay. The antibacterial property of the Schiff base and the complex was evaluated by a macrodilution method using Staphylococcus aureus, Escherichia coli, and the yeasts Candida parapsilosis. The cultures of bacteria and yeasts were incubated under vigorous shaking. The compounds were dissolved in small amount of DMSO. Concentration of the tested compounds ranging from 0.01 to 2.50 mmol L-1 for the bacteria and yeasts was used in all experiments. The antibacterial activity was characterized by IC50 and MIC values. MIC experiments on subculture dishes were used to assess the minimal microbicidal concentration (MMC). Subcultures were prepared separately in Petri dishes containing competent agar medium and

incubated at 30°C for 48 h. The MMC value was taken as the lowest concentration, which showed no visible growth of microbial colonies in the subculture dishes.

RESULTS AND DISCUSSION

The tripodal Schiff base H3L was obtained from the reaction of 1 : 3 molar quantities of tris(2-amino-ethyl)amine and 5-bromosalicylaldehyde in methanol. Complex I was prepared by the reaction of the Schiff base with manganese perchlorate in methanol. The Schiff base H3L is soluble in DMSO, but not very soluble in methanol and ethanol. The complex is soluble in methanol, ethanol, and DMSO.

The molecule of the Schiff base is shown in Fig. 1a. The bond lengths and angles related to the N(4), C(9), C(18) and C(27) atoms indicate that the apical N4 atom is s^3-hybridized. The bond lengths of C(7)—N(1), C(16)—N(2), and C(25)—N(3) in the Schiff base are in the range of 1.27—1.28 A, indicates they are typical double bonds. The intramolecular O—H---N hydrogen bonds (Table 3) in the Schiff base molecule make S(6) ring motifs [19]. Moreover, there exists tc—tc interactions (Table 4) in the crystal packing (Fig. 2a).

The Schiff base coordinates to the Mn atom through the three phenolate O and three imino N atoms, while the tertiary amine group does not take place in the coordination (Fig. 1b). The central Mn atom is in an octahedral coordination. The bond lengths of C(7)—N(1), C(16)—N(2), and C(25)-N(3) in the complex are about 1.28 A, which are longer than those in the free Schiff base. The coordination through the imino N atoms decreased the electron density of the C=N bonds, thus lengthened the bonds. The coordinate bonds related to the Mn atoms are similar to those observed in the literature [20, 21]. The axial O(1)Mn(1)N(3), O(2)Mn(1)N(1) and O(3)Mn(1)N(2) bond angles are 171.3(2)°, 169.9(2)° and 169.6(2)°, respectively. In the crystal structure of the complex,

Table 4. Parameters between the planes for the Schiff base*

Cg Distance between ring centroids, Ä Dihedral angle, deg Perpendicular distance of Cg(T) on Cg(J), A ß angle, deg Y angle, deg Slippage Perpendicular distance of Cg(J) on Cg(T), A

Q(1)- -Cg(1)#1 4.645 0 -3.540 40.4 40.4 3.007 -3.540

Cg(1)- -Cg(3) 3.746 9 -3.339 18.6 27.0 3.552

Cg(2)- -Cg(2)#2 4.319 0 -3.352 39.1 39.1 2.723 -3.352

* Symmetry codes: #1 1 - x, 1 - y, 1 - z; #2 1 - x, 1 - y, -z. Cg(

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