A New 3d-4f Heterobimetallic Complex Based on 4,4?-Dicarboxybiphenyl Sulfone: Synthesis, Crystal Structure and Antifungal Activity①

LI Bing WU Huan-Ping TIAN Xiao-Yan WANG Jia-Kai ZHOU Zheng QIN Shuai-Yu YANG Chan QIN Ting

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A New 3-4Heterobimetallic Complex Based on 4,4?-Dicarboxybiphenyl Sulfone: Synthesis, Crystal Structure and Antifungal Activity①

LI Bing②WU Huan-Ping TIAN Xiao-Yan WANG Jia-Kai ZHOU Zheng QIN Shuai-Yu YANG Chan QIN Ting

(750021)

A new 3-4heterobimetallic complex [PrCu(sba)2(Hsba)(H2O)3]·H2O (1)based on a versatile ligand H2sba (H2sba = 4,4?-dicarboxybiphenyl sulfone) was prepared andcharacterized by single-crystal X-ray diffraction, elemental analysis, IR spectroscopy andthermogravimetric analysis.Single-crystal X-ray diffraction indicates that complex 1 belongs to the monoclinic system, space group21/with= 12.4642(11),= 16.0586(16),= 21.9678(19) ?,= 92.888(1)o,= 4391.4(7) ?3,= 4,D= 1.800 g·cm-3,= 1.812mm-1,M= 1190.31,(000) = 2388, the final= 0.0663 and= 0.1539 for 7737 observed reflections with> 2().Complex 1 exhibits 2network skeletons which are linked by hydrogen-bonding interactions to give a 3supramolecular architecture.In addition, the antifungal effects of H2sba, metal salts and the title complex have also been studied by disc diffusion method against.Complex 1 has better antifungal activity than H2sba and the corresponding metal salts.Complex 1 has potential applications in the antifungal activity.

complex, crystal structure, antifungal activity;

1 INTRODUCTION

Over the last few decades, metal-organic hybrid materials found extensive applications in biological science, such as antimicrobial[1], antifungal[2], anti-inflammatory[3]and anticancer activities[4].Some complexeseven entered into clinical trials[5, 6].The developments of fungal resistances to antibiotics are major health problems, leading to treatment drawbacks for a large number of drugs[7].Therefore, it is urgent to develop new types of antifungal agents with efficiency and broad-spectrum to meet the need of agriculture[8, 9].It is well known that the structures of metalorganicframeworks have great influence on theirproperties, dependent on the metal and li-gand[10, 11].At present, a large number of transition metal and rare earth compoundshave been screened against bacteria andfungi for their special electronic configuration[12-14].In addition, multidentate O-donor ligands are widely employed in inhibitory against food poisoning and spore forming bacteria which can act synergistically with several components against a variety of micro-organisms[15].As one of the deriva- tives ofmultidentate O-donor ligands, H2sba not only makes the ligand more flexible, but also provides various coordination modes and antimicrobial activi- ties[16-19].

In view of these facts mentioned above, a new 3-4heterobimetallic complex[PrCu(sba)2(Hsba)(H2O)3]·H2O as antibacterial agent was synthesized by using the V-shaped H2sba.The complex was characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectra and thermogravimetric analysis.The antifungal activities of the ligand, metal salt and synthesized complex have been determined in vitro againstby disc diffusion method.

2 EXPERIMENTAL

2.1 Materials and measurements

All chemicals were purchased from commercial sources and used without further purification.The C, H and N microanalyses were carried out with a Vario EL III elemental analyzer.The Infrared spectra were recorded on a BEQ VZNDX 550 FTIR Instrument with KBr pellets in the 400～4000 cm-1region.Thermogravimetric analysis was carried out on a TA Instruments NETZSCH STA 449 C simultaneous TGA at a heating rate of 10 ℃·min-1under hydrosta- tic air.

2.2 X-ray crystallography

All diffraction data of complex 1 were collected on a Bruker/Siemens Smart Apex II CCD diffractometer with graphite-monochromated Moradiation (= 0.71073 ?) at 298(2) K.Cell parameters were retrieved using SMART software and refined using SAINTPLUS for all observed reflections.Data reduction and correction forand decay were performed using the SAINTPLUS software.Absorp- tion corrections were applied using SADABS[20].All structures were solved by direct methods using SHELXS-97[21]and refined with full-matrix least-squares refinement based on2using SHELXL-97.For 1, a total of 21971 reflections were collected in the range of 2.23°≤≤25.02°, of which 7737 were independent (int= 0.1043).The final= 0.0663 and= 0.1539 for 7737 observed reflections with> 2(),= 0.1054 and= 0.1700 for all data with (Δ)max= 5.660 and (Δ)min= –1.174 e·?–3.Selected bond lengths and bond angles of complex 1 are shown in Table 1.Hydrogen bonding geometry for the title complex is collected in Table 2.

Table 1. Selected Bond Lengths (?) and Bond Angles (°)

Symmetry code: #1: –+1/2,+1/2, –+3/2

Table 2. Hydrogen Bond Lengths (?) and Bond Angles (°)

Symmetry codes: #1: –+1/2,+1/2, –+3/2; #2: –+1/2,–1/2, –+3/2; #3:+1/2, –+3/2,–1/2; #4:–1/2, –+3/2,+1/2;

#5:,–1,+1; #6:+1/2, –+3/2,+1/2; #7: –+3/2,+1/2, –+3/2; #8:–1/2, –+3/2,–1/2; #9: –+2, –+1, –+1

2.3 Antifungal activity assays

Antifungal activities of the tested ligand, CuCl2·2H2O, Pr(NO3)3·6H2O, H2sba and complex 1 againstwere determined using a modified Kirby-Bauer disc diffusion method[22].

2.4 Synthesis of compound 1

A mixture containing CuCl2·2H2O (10.2 mg, 0.06 mmol), Pr(NO3)3·6H2O (13.0 mg, 0.04 mmol), H2sba (6.1 mg, 0.02 mmol) and water (6 mL) was sealed in a 10 mL Teflon-lined stainless-steel vessel and heated at 160 ℃ for 3 days, and then cooled to room temperature at a rate of 5 ℃·h-1.Blue bulk crystals of 1 were collected in a yield of 63% (based on H2sba).Anal.Calcd.(%) for 1 (C42H33CuO22PrS3): C, 42.39; H, 2.80; S, 8.07.Found (%): C, 41.87; H, 2.93; S, 7.96.IR (cm-1, KBr): 3450, 3340 (w), 1637(s), 1616 (s), 1417 (w), 991 (m), 891 (w), 621(s), 480 (w), 470 (w), 453 (w), 408 (w).1H NMR(400 MHz, DMSO-d6,ppm): 8.102～8.146 (12H, d,= 17.6 Hz), 8.437～8.466 (12H, d,= 11.6 Hz), 10.389 (1H, s).

3 RESULTS AND DISCUSSION

3.1 Crystal structure of [PrCu(sba)2(Hsba)(H2O)3]·H2O

Single-crystal X-ray diffraction analysis reveals that the title compound crystallizes in the monoclinic system with21/space group.The asymmetric unit contains one Pr(III) ion, one Cu(II) ion, two sba2?ligands, one Hsba-ligand, three coordinated water molecules and one lattice water molecules.As shown in Fig.1, the Pr(III) ion is eight-coordinated with five carboxylate oxygen atoms from distinct H2sba ligands and three oxygen atoms from coordinated water molecules, forming a distorted bi-capped triangular prism coordination geometry.The Cu(II) ion is five-coordinated with carboxylate oxygen atoms from different H2sba ligands, forming a distorted tetragonal pyramidal geometry.As shown in Table 1, the Pr–O distances range from 2.347(6) to 2.589(6) ?.The Cu–O distances range from 1.943(5) to 2.267(5) ?.

The fully deprotonated H2sba ligand adopts a bidentate-chelated coordination mode to link the adjacent Pr(III) ions Cu(II) ions to form a dinuclear double chain with the distance of 3.5871(12) ? between Pr(III) and Cu(II) ions.Then the neigh- boring 1chains are bridged by Hsba-to generate 2network skeletons (Fig.2), which are further extended into a 3supramolecular frameworkhydrogen-bonding, fromwhich O(16), O(19), O(20), O(21) and O(22) atoms act as hydrogen-bonding donors, interacting with the acceptors of O(2), O(5), O(12), O(13), O(15), O(17), O(18), O(20) and O(22) atoms from the adjacent molecule, with 1.804 ? for O(20)–H(20D)···O(13)#1, 1.841 ?for O(16)–H(16)···O(22)#5, 1.965 ?for O(22)– H(22D)···O(15)#9, 2.068 ?for O(20)–H(20C)···O(12)#7, 2.083 ?forO(21)– H(21C)···O(17)#7, 2.104 ? for O(22)–H(22C)···O(2)#3, 2.117 ? for O(19)–H(19C)···O(5)#6, 2.142 ?for O(21)–H(21D)···O(18)#8, 2.258 ? for O(19)– H(19D)···O(12)#7, 2.504 ? for O(19)–H(19D)···O(20) and 2.621 ? for O(20)–H(20D)···O(2)#1(Fig.3).

Fig.1. Coordination environment of complex 1 (Hydrogen atoms are omitted for clarity)

Fig.2. 2structure diagram of complex 1

Fig.3. A 3framework directed by hydrogen bonding interaction (green dashed lines)

3.2 FT-IR spectra

FT-IR measurement has been performed between 400～4000 cm-1.The IR spectrum of 1 shows an intense peak at about 3450 cm-1, corresponding to the O–H stretching band of the coordinated and lattice water molecules.The C=C stretching vibration of benzene ring can be observed at 1616 cm-1.The characteristic bands of carboxylate group in the complex are shown at 1637 cm-1for the antisym- metric stretching and 1417 cm-1for the symmetric stretching.The absence of expected bands at 1715 cm-1for the protonated carboxylate group illustrates its deprotonation when reacting with the Pr(III) and Cu(II) ions.

3.3 Thermogravimetric analysis

Thermogravimetric experiments were conducted to study the thermal stability of complex 1, which is an important parameter for energetic materials.As shown in Fig.4, the TGA curve of 1 suggests the first weight loss of 5.8% in the range of 87.7～177.0 ℃with an exothermic peak at 130.4 ℃, corresponding to the expulsion of coordinated and lattice water molecules (calcd.5.9%).The main framework remains intact until it is heated to 260.1 ℃, and then releases one ligand in the range of 260.1～349.6 ℃ with an exothermic peak at 283.6 ℃(found 24.8%, calcd.25.2%).After that, the complex loses the other ligands and ends at 800 ℃.

Fig.4. TGA curve of complex 1

3.4 Antifungal activity

The test samples were screened in vitro for their antifungal activities againstof fungal strains by the disc diffusion method.The antifungal effect ofcomplex 1 was revealed by clear inhibition zones on the contact surface between the impregnated disks andfungal lawn.

The zones of inhibition of the complex, DMF, CuCl2, Pr (NO3)3·6H2O and H2sba are shown in Fig.5.The solvent DMF has no effect on the antifungal activity.The inhibition diameters of complex 1 are 5, 9, 12, 15, 20 and 25 mm under different incubation time, which indicates that complex 1 has good antifungal properties compared to the corresponding ligand and metal salts against the tested fungus.And the inhibition diameters of 1 increased with pro- longing the incubation time.Based on the concentra- tion test (Fig.6), the diameters of zones of the inhibition ofH2sba are 10～17 mm, while complex 1is 15～28 mm, which is larger than H2sba.And complex 1 has concentration-dependent antifungal activity.The results of our study are in accordance with the reports of earlier workers[7,19, 23], which showed that the antibacterial activity of ligand is greatly enhanced whencoordinating to metal ions.Such an increased activity of the complex can be explained on the basis of Overtone’s concept[24]and Tweedy’s Chelation theory[25].What’s more, the positive control tests were explored with prochloraz as positive substance at the same experimental conditions.The result shows that the inhibition diameter of prochloraz is nearly 31 mm at 72 h, which is slightly larger than that of complex 1 (25 mm).It indicates that the title complex has potential applications in antifungal.

Fig.5. Mean inhibition diameters (mm) for the antifungal activity of complex 1, ligand and metal salts with different incubation time

Fig.6.Mean inhibition diameters (mm) of complex 1 againstin the range of 1～5 mg/mL

4 CONCLUSION

A new 3-4heterobimetallic complex based on the versatile ligand 4,4?-dicarboxybiphenyl sulfone was prepared.The complex exhibits 2network skele- tons, which are linked by hydrogen-bonding inter- actions to give a 3supramolecular architecture.In addition, the antifungal activity was preliminarily evaluated, which exhibits good activity against.Therefore, this study provides a new idea to synthesize metal-organic complex containing bacteriostatic ligand for a potential antibacterial agent.

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29 January 2018;

28 May 2018 (CCDC 1819184)

① Supported by the Natural Science Foundation of Ningxia (No.NZ15006) and College Students’ Innovation and Entrepreneurship Training Program (201710749004)

.E-mail: nxdaxue@126.com

10.14102/j.cnki.0254-5861.2011-1966