Syntheses, structures, and photocatalytic properties of two new one-dimensional chain transition metal complexes with mixed N,O-donor ligands

Accepted Manuscript Research paper Syntheses, Structures, and Photocatalytic Properties of Two New One-Dimensional Chain Transition Metal Complexes with Mixed N,O-donor Ligands Yu Qiao, Yan-Feng Zhou, Wei-Sheng Guan, Li-Hui Liu, Bo Liu, Guang-Bo Che, Chun-Bo Liu, Xue Lin, En-Wei Zhu PII: DOI: Reference:

S0020-1693(17)30768-5 http://dx.doi.org/10.1016/j.ica.2017.06.018 ICA 17666

To appear in:

Inorganica Chimica Acta

Received Date: Revised Date: Accepted Date:

16 May 2017 3 June 2017 7 June 2017

Please cite this article as: Y. Qiao, Y-F. Zhou, W-S. Guan, L-H. Liu, B. Liu, G-B. Che, C-B. Liu, X. Lin, E-W. Zhu, Syntheses, Structures, and Photocatalytic Properties of Two New One-Dimensional Chain Transition Metal Complexes with Mixed N,O-donor Ligands, Inorganica Chimica Acta (2017), doi: http://dx.doi.org/10.1016/j.ica. 2017.06.018

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Syntheses,

Structures,

and

Photocatalytic

Properties

of

Two

New

One-Dimensional Chain Transition Metal Complexes with Mixed N,O-donor Ligands

Yu Qiao a,b,*, Yan-Feng Zhouc, Wei-Sheng Guanb, Li-Hui Liua,c, Bo Liu a,c, Guang-Bo Chea,*, Chun-Bo Liud, Xue Lina,c, En-Wei Zhua,c

a

Key Laboratory of Preparation and Applications of Environmental Friendly

Materials (Jilin Normal University) Ministry of Education, Changchun 130103, P. R. China b

School of Environmental Science and Engineering, Chang’an University, Xi’an

710054, P. R. China c

College of Chemistry, Jilin Normal University, Siping 136000, P. R. China

d

Institute of Green Chemistry & Chemical Technology, Jiangsu University, Zhenjiang

212013, P. R. China *Corresponding Authors: E-Mail: [email protected]; [email protected] Tel: +86-434-3295100

Abstract Two transition metal complexes [M(2-NCP)(3-pyc)]n (M = Zn (1), Cu(2), 2-HNCP =

2-(2-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline,

3-Hpyc

=

pyridine-3-carboxylic acid) have been hydrothermally synthesized and characterized via elemental analysis, infrared spectrometry and single crystal X-ray diffraction. Structural analyses revealed that two complexes all exhibit double-stranded chain structures, which are further linked by the π···π stacking to furnish three-dimensional supramolecular network structures. Moreover, the complexes 1 and 2 were characterized via diffuse-reflectance UV-vis spectrum investigation. The degradation of organic dyes under visible light irradiation with complexes as the heterogeneous

photocatalyst has been investigated and two complexes show good photocatalytic properties. Transition

Keywords:

metal

complex;

2-(2-Carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline; Pyridine-3-carboxylic acid; Crystal structure; Photocatalytic activity

1. Introduction The research in the area of coordination polymers (CPs) continues to be interesting for their unique structures and tunable properties [1-3]. Recently, much effort has also been tried to develop new photocatalytic materials based on CPs, which is prompted largely by a demand for solving pollution problems owing to their potential applications in the degradation of organic pollutants. The construction by design of CPs using various multifunctional ligands connected through coordination bonds, weak intermolecular forces (hydrogen bonding, π···π stacking, dipole-dipole attractions and van der Waals interactions), or their combination, has been an increasingly active research area [4-6]. Among the reported CPs, N,O-donor multifunctional ligands such as pyridine carboxylic acids [7,8], pyrazine carboxylic acids[9], imidazole-4,5-dicarboxylic acids [10,11] and carboxyl derivatives of 1,10-phenanthroline [12,13] are particularly interesting because of their various coordination modes to metal ions. Recently, we are interested in the CPs constructed from

the

carboxyl

derivatives

of

(dipyrido[3,2-a:2’,3’-c]-phenazine-2-carboxylic (2,3-f)-pyrazino-(1,10)phenanthroline-

2,3-dicarboxylic

2-(4-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline

1,10-phenanthroline acid

[14], acid

[15], [16],

2-(2-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline [17,18] (2-HNCP)) with large π-conjugated system. They contain two potential coordination domains, one from terminal carboxyl group and one from bidentate phen moiety, thus they can function as either bridging or chelating ligands. Moreover, this type of ligands has a large number of conjunctive aromatic rings that make them very easy to generate π···π interactions and extend the structure into higher dimensionality. As an extension

of our study of CPs based on the carboxyl derivatives of 1,10-phenanthroline, we choose 2-HNCP and pyridine-3-carboxylic acid (3-Hpyc) mixed N,O-donor ligands to prepare the complexes. Because mixed N,O-donor ligands can assume many kinds of bridging or chelating modes to construct thrilling CPs with novel structural motifs and interesting properties. Fortunately, during the course of our research, two new transition metal complexes [M(2-NCP)(3-pyc)]n (M = Zn (1), Cu(2)) were successfully isolated by hydrothermal method. Complexes 1 and 2 represent the interesting one

dimensional double-stranded

chain structures.

In addition,

thermogravimetric analyses and photodegradation of organic dyes of two complexes have been investigated in detail. 2. Experimental Section 2.1. General All of the chemical reagents were obtained commercially and used without further purification. Elemental analyses were performed on a Perkin-Elmer 240 analyzer. The infrared (IR) spectrum was recorded as KBr pellets on a Nicolet iS50 FT-IR Spectrometer in the 4000-400 cm-1 region. Powder X-ray diffraction (PXRD) pattern of the sample was collected on a D/MAX-3C diffractometer with the Cu Ka radiation (λ = 1.5406 Å) at room temperature and 2θ ranging from 5 to 50 o. UV-vis diffuse reflectance spectrum (UV-vis DRS) was obtained for the dry-pressed disk samples using a Specord 2450 spectrometer (Shimadzu, Japan) equipped with the integrated sphere accessory for diffuse reflectance spectra, using BaSO4 as the reference reflectance sample. Thermogravimetric analysis (TGA) was performed on a STA 449 F3 Jupiter Synchronous thermal analyzer with a heating rate of 10 oC min-1 under air atmosphere. The photodegradation test was performed by using photocatalytic reactor (DW-01, xenon light source, Yangzhou University teaching instrument factory). 2.2. Synthesis and characterization 2.2.1. Synthesis of complex 1 A mixture of Zn(NO3)2·6H2O (0.0296 g，0.1 mmol), 2-HNCP(0.0170 g，0.05 mmol), 3-Hpyc(0.0123g, 0.1 mmol) and 10 mL of H2O was stirred for 10 min, then the pH value was adjusted to 6.5 by addition of NaOH solution (1 mol·L-1). The

resultant solution was heated at 443 K in a 25 mL Teflon-lined stainless steel autoclave under autogenous pressure for 3 days. Afterwards, the reaction system was cooled slowly to room temperature. The obtained solid is a mixture of yellow block crystals and powder. The crystals of complex 1 are picked out from the solid mixture in 56% yield based on Zn(NO3)2·6H2O. Anal. Calc. for C26H15N5O4Zn (1) (%): C, 59.27; H, 2.87; N, 13.29. Found (%): C, 59.22; H, 2.99; N, 13.25. IR (KBr pellet, cm-1): Complex 1: υ = 1616 (s), 1568 (s), 1402 (s), 1348 (s), 1192 (w), 1080 (m), 946 (w), 826 (m), 734 (m), 648 (w), 560 (w), 416 (w). Fig. S1a exhibits the IR spectrum of the complex 1. 2.2.2. Synthesis of complex 2 An identical procedure with 1 was followed to prepare 2 except Zn(NO3)2·6H2O was replaced by Cu(NO3)2·3H2O (0.0241g, 0.1 mmol). Green block crystals of 2 formed in 48% yield (based on Cu(NO3)2·3H2O). Anal. Calc. for C26H15N5O4Cu (2) (%): C, 59.48; H, 2.88; N, 13.34. Found (%): C, 59.40; H, 2.91; N, 13.30. IR (KBr pellet, cm-1): Complex 2: υ = 1610 (s), 1564 (s), 1402 (s), 1330 (s), 1192 (w), 1080 (m), 946 (w), 826 (m), 730 (m), 646 (w), 580 (w), 430 (w). Fig. S1b exhibits the IR spectrum of the complex 2. 2.3. Single-crystal X-ray diffraction Crystal data for the complexes 1 and 2 were collected on Bruker SMART APEX II CCD diffractometer with graphite monochromated Mo-Kα radiation (λ = 0.71073 Å) in the ω scan mode, respectively. All the structures were solved by direct methods using the program SHELXS-97 [19] and refined by full-matrix least-squares techniques against F2 using the SHELXTL-97 [20] crystallographic software package. All of the non-hydrogen atoms were easily found from the different Fourier map and refined anisotropically, whereas the hydrogen atoms of the complexes were placed by geometrical considerations and were added to the structure factor calculation. The crystallographic data of two complexes are summarized in Table 1 and the selected bond distances and angles in Table 2. 3. Results and discussion 3.1. Description of the crystal structure

X-ray single crystal diffraction reveals that the complexes 1 and 2 are isostructural, therefore, the complex 1 was selected and described here representatively to illustrate their detailed structures, respectively. As shown in Fig. 1, the complex 1 is composed of one crystallographic unique Zn2+ ion, one 2-NCP- ligand and one 3-pyc- ligand in the asymmetric unit. Zn2+ center is five-coordinated with three nitrogen atoms (N1, N2, N5) from one 2-NCP- and one 3-pyc- ligands, two oxygen atoms (O1#1, O3#2, symmetry code: #1: -x+2, -y+1, -z+2; #2: -x+2, -y+1, -z+1.) from other two different 2-NCP- and 3-pyc- ligands (Fig. 1), showing a slightly distorted tetragonal pyramid geometry. The base plane is formed by O1 #1, O3#2, N1 and N2, and the axial position is occupied by N5. The average Zn-O (2.004(17) Å) and Zn-N (2.125(2) Å) distances for 1 are near to those of reported [21]. Adjacent two metal centers are bridged by 2-NCP- and 3-pyc- mixed ligands in 1. Each 2-NCP- ligand links two metal ions in bis-chelating and monodentate bridging mode while each 3-pyc- ligand also links two metal centers in monodentate bridging mode in complex 1 (Scheme 1), respectively, and 1D double chains are constructed (Fig. 2). The 1D chain structure of the complex 1 can be viewed as a series of alternating grids containing a 12-membered ring (Zn2C6N2O2) and a 26-membered ring (Zn2C18N4O2), respectively. Within the Zn2C6N2O2 ring, the distance between Zn···Zn atoms is 6.438 Å, while in the Zn2C18N4O2 ring, the Zn···Zn distance is 7.396 Å, respectively. The neighboring 1D chains

interact

through

π···π

stackings

between

the

3-pyc-

ligands

(centroid-to-centroid distance ca. 3.703 Å, Fig. 3) to yield a 2D layer structure. Besides, the adjacent layers are stacked to furnish a 3D supramolecular network structure (Fig. 4) via π···π interactions between the pyridine and benzene rings of 2-NCP- ligands (atom-to-centroid distance ca. 3.604 Å). The coordination mode of 2-NCP- ligand in complex 1 is different from in reference 18. 2-NCP- only exhibits one bis-chelating coordination mode as bridging ligand to link two Nd 3+ ions for the complex [Nd(O–NCP)2(NO3)]n in reference 18. The structural differences of two complexes illustrate that the influence of coordination modes of bridging ligand 2-NCP- in the self-assembly of polymeric coordination architectures.

3.2. PXRD and TGA In order to substantiate the phase purity of the measured complexes 1 and 2, their PXRD were performed before the TGA and photocatalytic properties were measured (Fig. S2a and 2b). The experimental PXRD patterns are in good agreement with the corresponding simulated patterns except for the relative intensity variation because of preferred orientation of the crystal. Thermal behaviours of two complexes were studied by TGA. As shown in Fig. 5, the TGA curves of complexes 1 and 2 were much similar, probably due to their analogue's structural nature. The complexes loss their mixed ligands from 340 oC for 1 and 345 oC for 2, respectively. The remaining weight may be attributed to the formation of ZnO (found: 13.0%, calcd: 12.38%) and CuO (found: 12.29%, calcd: 12.11%), respectively. Two complexes had exhibited excellent thermal stabilities. 3.3. Photocatalytic studies Photocatalysts have attracted much attention due to their potential applications in purifying water and air by thoroughly decomposing organic pollutants [22,23]. The UV-vis DRS of the complexes 1 and 2 are demonstrated in Fig. 6. It is obvious that the absorption is in the ultraviolet and visible spectrum region, so the reactions were carried out at 500 W in a GHX-2 photocatalytic reactor under Xe lamp. Photocatalytic degradation of four commonly used dyes, MV, MO, MB and RhB, was investigated. As the optical band gap was one principal factor on judging whether the complexes have potential application in photocatalytic materials, the band gaps of complexes 1 and 2 were investigated through the measurements of their diffuse reflectivity. The band gaps were defined as the intersection point between the energy axis and the line extrapolated from the linear portion of the adsorption edge in a plot of Kubelka-Munk function F versus energy E [24]. The K-M function, F= (1-R)2/2R, is converted from the measured diffuse reflectance data. The Eg values are 2.98 eV and 2.76 eV for 1 and 2, respectively (Fig. S3). At the same time, the kinetic behaviors of photocatalytic degradation using the composite photocatalysts were further investigated, and the results are shown in Fig. 7.

All of them fit well with the pseudo-first-order correlation: ln (C0/C) = kt, where C was the concentration of organic dye remaining in the solution at irradiation time of t, C0 was the initial concentration at t=0, and k was the degradation apparent rate constant. It can be seen that approximately 25% of MV, 60% of MO, 68.21% of MB and 20% of RhB have been decomposed after 190 min of irradiation for 1, respectively. In contrast, it can be seen that approximately 82% of MV, 80.41% of MO, 84.35% of MB and 70.86% of RhB have been decomposed after 190 min of irradiation for 2, respectively. These results indicated that two complexes are more active for the decomposition of MB under visible light irradiation. There are good candidates for photocatalytic degradation of MB. The order of different organic pollutions degradation rate for as-prepared photocatalyst 1 was MB (0.0062 min 1) > −

MO (0.0043 min 1) > MV (0.0011 min 1) > RhB (0.0008 min 1) > blank (0.00030 −

−

−

min-1, 0.00028 min 1, 0.00027 min 1, 0.00023 min 1, respectively). And photocatalyst −

−

−

2 was MB (0.010 min 1) > MV (0.0089 min 1) > MO (0.0086 min 1) > RhB (0.0061 −

−

−

min 1) > blank (0.00030 min 1, 0.00028 min 1, 0.00027 min 1, 0.00023 min 1, −

−

−

−

−

respectively). In addition, the stabilities of 1 and 2 were monitored using PXRD during the photocatalytic process. After photocatalysis, two complexes display similar PXRD patterns to the original, implying that the stabilities toward photocatalytic reactions for 1 and 2 are excellent (Fig. S2a and 2b). 3.4. Photocatalytic mechanism Based on the above results, the two complexes have good photocatalytic activity for MB. In order to clarify the photocatalytic mechanism of MB, trapping experiments of radicals were used to detect the main oxidative species in the photocatalytic process [25]. Taking the photodegradation of MB as an example, the degradation rate of complexes 1 and 2 under visible light without the addition of scavenger can reach 68.21% and 84.35%, respectively. As shown in Fig. 8 for the as-prepared sample, it can be seen that when the radical scavenger isopropyl alcohol (IPA) was added into reaction solution, the degradation rate of MB obviously inhibited (41.83% for 1 and 57.18% for 2). Therefore, combined with the above discussion, the possible photocatalytic mechanism for degradation of MB with two photocatalyst was

proposed as shown in Fig. 9. The •OH plays an important role in the photocatalytic process, which possesses strong oxidation ability and can oxidize the organic pollutants. On the basis of the above-mentioned photocatalytic mechanism, the efficiency of the photocatalyst relates to the balance between charges separation, interfacial electron transfer and charge recombination. Generally speaking, the ease of the charge separation depends on a narrow band gap. The smaller Eg value is in favor of the electron transition, which may be beneficial to catalysis. So it is noted that the catalytic activities of two complexes follow the sequences 1<2 in agreement with the Eg values. 4. Conclusions In summary, two new double-stranded chain complexes have been synthesized by using Zn(II)/Cu(II) ions, 2-HNCP and 3-Hpyc ligands under hydrothermal conditions. The complexes 1 and 2 appear to be active for the photocatalytic decomposition of common organic dyes (MV, MO, MB and RhB) used in textile industries. Moreover, photocatalytic experiment results manifest that the copper complex is more photocatalytically active for degrading four dyes under xenon lamp irradiation, which is an excellent candidate for in photocatalytic degradation of organic pollutants. This work opens a new prospective and a feasible strategy for the application of CPs in photocatalytic degradation of organic dye pollutants by utilizing solar energy. 5. Supplementary data The crystallographic data have been deposited at the Cambridge Crystallographic Data Centre, CCDC 1488987 for 1 and 1488988 for 2. Copies of this information may be obtained free of charge from the director, CCDC, 12 Union Road, Cambridge, CB2 IEZ,

UK

(E-mail:

[email protected];

Fax:

44-1223-336-033;

http://

www.ccdc.cam.ac.uk). Acknowledgements This work is supported by the National Natural Science Foundation (No. 21576112),

Natural

Science

Foundation

Project

of

Jilin

Province

(No.

20150623024TC-19 and 20170520147JH) and the Science and Technology

Development Plan of Siping City (2015049). References [1] A. L. Balch, K. Winkler, Chem. Rev. 116 (2008) 3812. [2] M. Eddaoudi, D. F. Sava, J. F. Eubank, K. Adil, V. Guillerm, Chem. Soc. Rev. 44 (2015) 228. [3] J.-W. Liu, L.-F. Chen, H. Cui, J.-Y. Zhang, L. Zhang, C.-Y. Su, Chem. Soc. Rev. 43 (2014) 6011. [4] Y.-B. He, B. Li, M. O'Keeffe, B.-L. Chen, Chem. Soc. Rev. 43 (2014) 5618. [5] N. Stock, S. Biswas, Chem. Rev. 112 (2012) 933. [6] X.-C. Wang, C.-B. Liu, J. Chen, X.-Y. Li, C.-B. Che, Y.-S. Yan, Z. Anorg. Allg. Chem. 637 (2011) 698. [7] C.-B. Liu, Y. Cong, H.-Y. Sun, G.-B. Che, Inorg. Chem. Commun. 47 (2012) 71. [8] T.-H. Yang, A. R. Silva, F.-N. Shi, CrystEngComm. 17 (2015) 3852. [9] B. Masci, P. Thuéry, Cryst. Growth Des. 8 (2008) 1689. [10] Y. Zhang, B.-B. Guo, L.-Li, S.-F. Liu, G.-Li, Cryst. Growth Des. 13 (2013) 367. [11] G. Yuan, K.-Z. Shao, D.-Y. Du, X.-L. Wang, Z.-M. Su, J.-F. Ma, CrystEngComm. 14 (2012) 1865. [12] C.-B. Liu, J. Chen, H.-Y. Bai, S.-T. Wang, Q.-W. Wang, G.-B. Che, Chinese J. Struct. Chem. 31 (2012) 1182. [13] X.-J. Zhang, W.-K. Li, W.-T. Zhang, G.-B. Che, X.-Y. Li, Y. Qiao, C.-C. Zhao, Inorg. Chem. Commun. 51 (2015) 122. [14] G.-B. Che, J. Chen, X.-C. Wang, C.-B. Liu, C.-J. Wang, S.-T. Wang, Y.-S. Yan, Inorg. Chem. Commun. 14 (2011) 1086. [15] Z.-H. Weng, D.-C. Liu, Z.-L. Chen, H.-H. Zou, S.-N. Qin, F.-P. Liang, Cryst. Growth Des. 9 (2009) 4163. [16] H.-Y. Sun, C.-B. Liu, Y. Cong, M.-H. Yu, H.-Y. Bai, G.-B. Che, Inorg. Chem. Commun. 35 (2013) 130. [17] Y.-Q. Wei, K.-C. Wu, J.-G. He, W.-X. Zheng, X.-Y. Xiao, CrystEngComm. 13 (2011) 52.

[18] G.-B. Che, S.-Y. Liu, Q. Zhang, C.-B. Liu, X.-J. Zhang, J. Solid State Chem. 225 (2015) 378. [19] G. M. Sheldrick, SHELXS-97, Programs for X-ray Crystal Structure Solution, University of Göttingen, Germany, 1997. [20] G. M. Sheldrick, SHELXL-97, Programs for X-ray Crystal Structure Refinement, University of Göttingen, Germany, 1997. [21] Z.-H. Yang, X.-F. Xiong, H.-M. Hu, Y. Luo, L.-H. Zhang, Q.-H. Bao, G.-L. Xue, Inorg. Chem. Commun. 14 (2011) 1406. [22] (a) D.-S. Li, Y.-P. Wu, J. Zhao, J. Zhang, J.-Y. Lu, Coord. Chem. Rev. 261 (2014) 1; (b) C. Zhang, F.-G. Ye, S.-F. Shen, Y.-H. Xiong, L.-J. Su, S.-L. Zhao, RSC Adv. 11 (2015) 8228; (c) C.-C. Wang, J.-R. Li, X.-L. Lv, Y.-Q. Zhang and G.-S. Guo, Energy Environ. Sci. 7 (2014) 2831; (d) T. Wen, D. X. Zhang, and J. Zhang, Inorg. Chem. 52 (2013) 12. [23] (a) T. Wen, D.-X. Zhang, J. Liu, R. Lin, J. Zhang, Chem. Commun., 49 (2013) 5660; (b) T. Zhang, W.-B. Lin. Chem. Soc. Rev. 16 (2014) 5982; (c) Y.-P. Wu, X.-Q. Wu, J.-F. Wang, J. Zhao, W.-W. Dong, D.-S. Li, Q.-C. Zhang, Cryst. Growth Des. 16 (2016) 2309. [24] Y. Gong, Z. Hao, J.-L. Sun, H.-F. Shi, P.-G. Jiang, J. Lin, H. Dalton Trans. 42 (2013) 13241. [25] H. Zhang, R.-L. Zong, J.-C. Zhao, Y.-F. Zhu, Environ. Sci. Technol. 42 (2008) 3803.

Table 1. Selected crystallographic data for complexes 1 and 2 Complex

1

2

Empirical formula

C26H15N5O4Zn

C 26H 15N5O4Cu

Formula weight

526.80

524.97

Crystal system

Triclinic

Triclinic

Space group

P-1

P-1

a (Å)

8.4374(5)

8.4248(9)

b (Å)

9.9196(6)

9.8540(11)

c (Å)

13.3618(8)

13.3428(15)

α (°)

92.1600(10)

91.639(2)

β (°)

104.2720(10)

104.505(2)

γ (°)

103.0910(10)

102.580(2)

V (Å 3)

1050.45(11)

1042.6(2)

2

2

1.666

1.672

µ (Mo Kα) (mm )

1.218

1.097

F(000)

536

534

Reflections collected

5835

5786

Independent reflections

4109

4052

Parameters

325

325

Goodness-of-fit

1.039

1.038

R1 [I > 2σ(I)]

0.0355

0.0514

wR2 (all data)

0.0890

0.1203

Z -3

Dcalc(g cm ) −1

Table 2. Selected bond lengths and bond angles for complexes 1 and 2 1

2

Bond lengths

Bond lengths

Zn-N(1)

2.116(2)

Cu-N(1)

2.057(3)

Zn-N(2)

2.198(2)

Cu-N(2)

2.018(3)

Zn-N(5)

2.064(2)

Cu-N(5)

2.190(3)

Zn-O(1)#1

1.9911(19)

Cu-O(2)#1

1.927(3)

Zn-O(3)#2

2.0178(18)

Cu-O(4)#2

1.975(3)

Bond angles

Bond angles

O(1)#1-Zn-O(3)#2

96.31(8)

O(2)#1-Cu-O(4)#2

95.38(12)

O(1)#1-Zn-N(5)

104.69(8)

O(2)#1-Cu-N(5)

99.66(12)

O(1)#1-Zn-N(1)

94.42(8)

O(2)#1-Cu-N(1)

93.35(12)

O(3)#2-Zn-N(5)

108.22(9)

O(4)#2-Cu-N(5)

102.94(12)

O(3)#2-Zn-N(1)

137.88(8)

O(4)#2-Cu-N(1)

150.35(13)

N(5)-Zn-N(1)

108.13(8)

N(1)-Cu-N(5)

103.43(12)

Symmetry transformations used to generate equivalent atoms: 1: #1 -x+2, -y+1, -z+2; #2 -x+2, -y+1, -z+1. 2: #1 -x+1, -y, -z+1; #2 -x+1, -y, -z+2.

Scheme 1. Coordination modes of 2-NCP- and 3-pyc- ligands (M = Zn(1), Cu(2))

Captions: Fig. 1. ORTEP drawing of complex 1 showing Zn2+ coordination environment with thermal ellipsoids at 30% probability (hydrogen atoms have been removed for clarity). Symmetry code: #1: -x+2, -y+1, -z+2; #2: -x+2, -y+1, -z+1. Fig. 2. The 1D double-stranded chain structure of complex 1 with hydrogen atoms omitted for clarity. Fig. 3. The 2D layer structure of complex 1 constructed by the π···π stacking interactions. Hydrogen atoms have been omitted for clarity. Fig. 4. The 3D supramolecular structure of complex 1 constructed by the π···π stacking interactions. Hydrogen atoms have been omitted for clarity. Fig. 5. TG curves of the complexes 1 and 2. Fig. 6. UV-vis diffuse-reflectance spectra of complexes 1-2, 2-HNCP and 3-Hpyc ligands with BaSO4 as background. Fig. 7. (a, b) The photocatalytic activities of 1 and 2 for different organic dyes of degradation under visible-light; (c, d) the first-kinetic of the photocatalytic degradation of four organic dyes. Fig. 8. Plots of radicals trapping in the system of photodegradation of MB by compound 1 and 2 under visible light irradiation. Fig. 9. Possible mechanism for the photo-induced charge transfer route of two photocatalysts. Figure S1. IR spectra of the complexes 1 (a) and 2 (b). Figure S2. Simulated、as-synthesized and after photocatalysis powder XRD patterns of the complexes 1 (a) and 2 (b). Figure S3. Kubelka-Munk-transformed diffuse reflectance of the complexes 1 (a) and 2 (b).

Research Highlights Metal-organic frameworks (MOFs)-metal ions interconnected by organic ligands -are porous crystals suitable for applications such as adsorption, catalysis, chirality, fluorescence and magnetism. Phenanthroline derivatives and polycarboxylate ligands are common building blocks for the construction of MOFs. Yu Qiao and Guang-Bo Che at Jilin Normal University in Siping and co-workers1-4 have explored their crystal-making options and constructed two MOFs using both rigid phenanthroline-containing and carboxylate ligands. Recently, much effort has also been tried to develop new photocatalytic materials based on MOFs, which is prompted largely by a demand for solving pollution problems owing to their potential applications in the degradation of organic pollutants. The construction by design of MOFs has been an increasingly active research area. The researchers obtained the MOF crystals by cooling a heated mixture of rigid phenanthroline-containing ligands, carboxylate ligands, metal ions (including copper and zinc), sodium hydroxide and water. They characterized the structures of the MOFs and found two of the samples exhibit double-stranded chain structures, which are further linked by the π-π stacking to furnish three-dimensional supramolecular network structures. (pictured). The researchers also found that two complexes possess excellent photocatalytic properties. The researchers suggest that the novel MOF may be promising for candidates as photocatalytic materials. The authors of this work are from: Key Laboratory of Preparation and Applications of Environmental Friendly Materials (Jilin Normal University) Ministry of Education, Changchun 130103, P. R. China; School of Environmental Science and Engineering, Chang an University, Xi an 710054, China; College of Chemistry, Jilin Normal University, Siping 136000, P. R. China; Institute of Green Chemistry & Chemical Technology, Jiangsu University, Zhenjiang 212013, P. R. China Reference [1] Y. Qiao, B. Wei, X.-Y. Li, G.-B. Che, C.-B. Liu, X.-J. Zhang, E.-W. Zhu, F. Liu, Chinese J. Struct. Chem. 36 (2017) 73. [2] G.-B. Che, C.-B. Liu, B. Liu, Q.-W. Wang, Z.-L. Xu, CrystEngComm 10 (2008) 184. [3] X.-Y. Li, C.-B. Liu, G.-B. Che, X.-C. Wang, C.-X. Li, Y.-S. Yan, Q.-F. Guan, Inorg. Chim. Acta 363 (2010) 1359. [4] G.-B. Che, J. Wang, C.-B. Liu, X.-Y. Li, B. Liu, J. Sun, Y. Liu, L. Lu, Inorg. Chim. Acta 362 (2009) 2756.

Graphical Abstract Syntheses, Structures, and Photocatalytic Properties of Two New One-Dimensional Chain Transition Metal Complexes with Mixed N,O-donor Ligands Yu Qiao, Yan-Feng Zhou, Wei-Sheng Guan, Li-Hui Liu, Bo Liu, Guang-Bo Che, Chun-Bo Liu, Xue Lin, En-Wei Zhu

Two transition metal complexes with one-dimensional chain structures based on mixed N,O-donor ligands have been hydrothermally synthesized. The degradation of organic dyes under visible light irradiation with complexes as the heterogeneous photocatalyst has been investigated and two complexes show good photocatalytic properties.