王卷剛 尚云麗

(淮北師范大學化學與材料科學學院，淮北 235000)

Tremendous interest has been attracted to Shiff base complexes because they not only have a lot of application prospect in analytical chemistry, medicine,catalysis, function materials and metal corrosion, but also exhibit diversity in structure. In addition, some of Shiff base complexes are used as nonlinear optical materials[1-2], models of reaction centers of metalloenzymes[3]and excellent catalytic activitives for aziridination, epoxidation, etc[4-9]. Although many welldocumented and stable structures of 1,1′-[3,6-diazaoctane-1,8-diylbis (nitrilomethylidyne)]-di-2-naphtholato complexes have been reported[10], the structures of this selan-type compounds with their transition metal Co(Ⅲ)complexes have not been determined and reported. In this paper, a new salen-type mononuclear Co (Ⅲ)complex [Co(L)]NO3·2EtOH were synthesized, characterized structurally by X-ray crystallography. Furthermore, the antibacteria activities of the complex were determined in vivo[11].

Structural formula of the ligand

1 Experimental

1.1 Materials and instruments

All chemicals were purchased from Alfa Aesar fine chemical Co., LTD and were used without further purification. The IR spectrum in the 400～4 000 cm-1region was determined on VERTEX70 FT-IR spectrophotometer using KBr pellets. C, H and N analyses were carried out with GmbH VarioEL V3.00 automatic elemental analysis instrument and X-ray single-crystal structure determination was obtained with Bruker Smart Apex(Ⅱ)-CCD area detector.

1.2 Synthesis of [Co(L)]NO3·2EtOH

N1-(2-(2-aminoethylamino)ethyl)ethane-1,2-diamine(0.29 g, 2.0 mmol) in EtOH (8 mL) was added to a stirring solution of 2-hydroxy-1-naphthaldehyde (0.68 g, 4.0 mmol) in EtOH (50 mL), yielding a yellow solution. The solution was stirred at room temperature for 40 min. Solutions of NaOH (0.16 g, 4.0 mmol) in MeOH (45 mL), Co(NO3)2·6H2O (0.58 g, 2.0 mmol) in EtOH (30 mL) were then sequentially added dropwise to the above stirred solution. The purple mixture was cooled to room temperature, filtered and removed under reduced pressure to give a purple solid, then washed with diethyl ether. The crude solid was recrystallisation with warm water afforded purple microcrystals, then the crystals were collected and dried in vacuo over P2O5. Yield： 0.85 g, 63%. Anal.Calcd. For C32H40CoN5O7(%)： C, 57.72; H, 6.01; N,10.52. Found(%)： C, 57.76; H, 6.04; N,10.59. IR data(cm-1, KBr pellet)： 1 592 (νC-N), 1 216(νAr-O), 463(νCo-O), 425(νCo-N).

1.3 Determination of the single-crystal structure

A purple crystal with dimensions of 0.38 mm×0.35 mm×0.31 mm was selected and mounted on a Bruker Smart Apex CCD area detector.The data were collected with a graphite-monochromatic Mo Kα radiation (λ=0.071 073 nm)at 93 (2)K.A total of 28 414 reflections were collected in the range of 3.07°≤θ≤27.42° by using a multi-scan mode with 7 049 independent ones(Rint=0.064 3), of which 5 858 with I＞2σ(I) were considered with the succeeding refinements. The structure was solved by direct methods and refined by fullmatrix least-squares techniques on F2using the SHELXL 97 program. The final refinement converged at R1=0.064 3, wR2=0.207 6 (w=1/[σ2(Fo2)+(0.130 3P)2+1.987 3P], where P=(Fo2+2Fc2)/3), S=1.128, (Δ/σ)max=0.001, (Δρ)min=-533 e·nm-3and (Δρ)max=1 563 e·nm-3.

CCDC： 856755.

2 Results and discussion

2.1 Crystal structure of the title complex

The crystal data and structure refinements for the title compound and the selected bond lengths, angles are listed in Table 1 and Table 2, respectively.

Table 1 Crystal data and structure refinements for the title compound

As shown in Fig.1, the cobalt atom (Co(1)) is sixcoordinated by four nitrogen (N(1), N(2), N(3), N(4))atoms and two oxygen atoms (O(1), O(2)) of the L2-ligand. The interatomic distances of Co(1)-N(2)(0.194 3(3) nm) and Co(1)-N(3) (0.195 3(3) nm) are longer than those of Co(1)-O(1) (0.190 3(2) nm), Co(1)-O(2) (0.189 4(2) nm), Co(1)-N(1) (0.189 4(3) nm) and Co(1)-N(4) (0.190 2(3) nm), indicating slight distortion toward octahedral geometry. The bond angles of N(1)-Co(1)-O(2), N(2)-Co(1)-N(1), N(1)-Co(1)-O(1), O(1)-Co(1)-O(2), N(2)-Co(1)-O(2), N(4)-Co(1)-N(2) and O(2)-Co(1)-N(4) are 89.31(10)°, 85.99(11)°, 93.30(10)°,91.59(11)°, 90.19(11)°, 90.87(11)° and 93.95(10)°,respectively. As shown in Fig.2, the nitrogen atoms of coordinated L2-and uncoordinated EtOH oxygen atoms are linked together by the N-H…O hydrogen bonds N(2)-H(2)…O(6) 0.289 1 nm and N(3)-H(3)…O(7)0.285 6 nm (Table 3). The uncoordinated EtOH molecules and uncoordinated nitrate ion oxygen atoms provide O-H…O hydrogen bonds (O(7)-H(7)…O(4)0.281 7 nm and O(6)-H(6A)…O(3)0.298 3 nm).Thus,through extensive hydrogen bonding interactions,[Co(L)]+fragments, free EtOH molecules and nitrate ions are linked into a supramolecular framework.

Table 2 Selected bond lengths (nm) and bond angles (°) of the title compound

Table 3 Hydrogen bonds in the title complex

Fig.1 Crystal structure of the title complex

Fig.2 Hydrogen bonding interactions in the complex

2.2 Electrochemical study

The cyclic voltammograms of the complex [Co(L)]NO3·2(EtOH) was examined at a scan rate 50 mV·s-1using Ag|AgCl electrode at 1 μmol·L-1in DMF solvent with 0.05 mol·L-1tetrabutyl-ammonium hexafluorophosphate as supporting electrolyte (Fig.3). The one-electron reduction process Ⅰat E1/2=-0.41 V,was assigned to the metal centre Co (Ⅲ)/Co (Ⅱ)wave couple.The another one-electron reduction process Ⅱat E1/2=-0.65 V, was assigned to the metal centre Co(Ⅱ)/Coガwave couple.

Fig.3 Cyclic voltammograms of the complex

Table 4 Antibacterial activity of the ligand and the complex

2.3 Antibacterial activity

The results of antibacterial activity of ligand and complex are listed in Table 4. The measured data are lethal rate. For comparison, the antibacteria activities of Co(NO3)3were determined by the same way. We can see that ligands and Co(NO3)3have low antibacterial activities from the data in Table 4. The antibacterial activities were enhanced (activity increased by 20% to 90% comparising to the ligand) when using the[Co(L)]NO3·2EtOH, indicating that Co(Ⅲ)metal ions play a role in promoting biological activity of ligands.

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