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Polycarboxylate-directed Various Cd(II) Coordination Polymers Based on a Semi-rigid Bis-pyridyl-bis-amide Ligand: Construction, Fluorescent and Photocatalytic Properties Xiu-Li Wang, Ying Xiong, Xiaoting Sha, Guocheng Liu, and Hongyan Lin Cryst. Growth Des., Just Accepted Manuscript • Publication Date (Web): 22 Dec 2016 Downloaded from http://pubs.acs.org on December 23, 2016

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Crystal Growth & Design

Polycarboxylate-directed Various Cd(II) Coordination Polymers Based on a Semi-rigid Bis-pyridyl-bis-amide Ligand: Construction, Fluorescent and Photocatalytic Properties Xiu-Li Wang∗, Ying Xiong, Xiao-Ting Sha, Guo-Cheng Liu, and Hong-Yan Lin Department of Chemistry, Liaoning Province Silicon Materials Engineering Technology Research Centre, Bohai University, Jinzhou 121013, P. R. China

Abstract Nine new Cd(II) coordination polymers (CPs) including [Cd3(4-bmbpd)4Cl6(H2O)2] (1),

[Cd(4-bmbpd)(2,2′-BDC)(H2O)]

(2),

[Cd(4-bmbpd)(OBA)]·H2O

(3),

[Cd(4-bmbpd)0.5(ADTZ)(H2O)]·H2O (4), [Cd4(4-bmbpd)(1,3-ATDC)4(H2O)6]·2H2O (5),

[Cd(4-bmbpd)(3-NPH)(H2O)]·H2O

[Cd(4-bmbpd)0.5(HIP)]·H2O (4-bmbpd

=

(8),

(6,)

[Cd(4-bmbpd)0.5(NIP)(H2O)]

(7),

[Cd3(4-bmbpd)2(1,3,5-BTC)(H2O)4]·4H2O

(9)

N,N’-bis(4-methylenepyridin-4-yl)-1,4-benzenedicarboxamide,

2,2′-H2BDC =2,2'-biphenyldicarboxylic acid, H2OBA = 4,4'-oxybis(benzoic acid, H2ADTZ

=

2,5-(s-acetic

acid)dimercapto-1,3,4-thiadiazole,

1,3-H2ATDC

=

1,3-adamantanedicarboxylic acid, 3-H2NPH = 3-nitrophthalic acid, H2NIP = 5-nitroisophthalic acid, H2HIP = 5-hydroxyisophthalic acid and 1,3,5- H3BTC = 1,3,5-benzenetricarboxylic

acid),

have

been

presented

with

hydrothermal/solvothermal technique and structurally characterized by single-crystal X-ray diffraction, powder XRD, TG analysis and IR spectra. Complex 1 exhibits a one-dimension

(1D)

wave-like

double

chain

constructed

from

[Cd3(4-bmbpd)2Cl6(H2O)2] subunits and µ2-bridging 4-bmbpd ligands. 2 is a 2D 4-connected layer consisted of 1D [Cd-4-bmbpd]n zigzag chains and 1D [Cd-2,2′-BDC]n single-strand helix chains. Complex 3 is also a 2D 4-connected network constituted of 1D [Cd-OBA]n linear chains and [Cd(4-bmbpd)]n wave-like

∗ Corresponding author. Tel.: +86-416-3400158 E-mail address: [email protected] (X.-L. Wang)

ACS Paragon Plus Environment


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chains. Complex 4 holds a (2,4,4)-connected 2D architecture based on [Cd2(ADTZ)2] rings and µ4-bridging 4-bmbpd ligands with {42·82·102}{ 42·84}2{4}2 topology. Complex 5 exhibits an intriguing 1D chain constructed from [Cd4(1,3-ATDC)4] rings and µ2/µ4-bridging 4-bmbpd ligands. Complex 6 presents a 1D ladder-shaped chain. Complex 7 displays a 3D (4,4)-connected framework giving an interesting self-penetrating structure. Complex 8 is a 3D (4,5)-connected architecture with {44·62}{44·66} topology. 9 shows a 3D (2,3,4,4)-connected framework, which contains [Cd-1,3,5-BTC]n 1D double chains. The versatile structures reveal the impact of the carboxyl position and number, the flexibility, as well as the functional groups of polycarboxylate auxiliary ligands on the architectures. Furthermore, the effects of different organic solvents on the fluorescent behaviors of 1–4 and 7–9, and the photocatalytic properties of 1–9 under UV irradiation were studied.

Introduction The overwhelming interest in the rational construction of original coordination polymers (CPs) lies on not only their fascinating structures and functional properties, but also their very rapid development during last two decades.1–3 CPs as multifunctional materials have potential applications in many fields, such as catalysis, gas absorption, magnetism, chirality, nonlinear optics, luminescence and so on.4–8 As is generally known, applications of CPs depend largely on their architectures,9 so design and construction of the CPs with desired structures and functions are quite critical. The variety of the self-assembling structures depend on many factors, such as the nature of ligands, metal-to-ligand ratio, geometric requirement of central metals and extrinsic experimental conditions.10–13 Among the factors above, organic ligands play a significant role in constructing CPs.14, 15 Dipyridyl-based acylamide as a type of excellent organic ligands can meet the coordination requirements of central metals with their pyridyl groups and interact with each other through hydrogen bonding interactions from the amide groups, which have attracted considerable attention over the past years. Chen et al. and our group have obtained a lot of transition metal (ZnII, CdII, CuII) CPs based on the flexible 2


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bis-pyridyl-bis-amide ligands containing -(CH2)n- backbones.16, synthesized

several

ZnII

CPs

derived

from

17

Lu’s group also

the

semi-rigid

N,N’-bis(pyridine-4-yl)-1,4-benzenedicarboxamide with benzene backbone.18 In the family of dipyridyl-based acylamide ligands, if the two pyridyl amide groups of the ligands are separated by two or more −CH2−, the pyridyl rings may irregularly rotate. On the contrary, if phenyl ring is used instead of the −CH2−, the pyridyl rings are fixed and turned rigid to some extent. Therefore, we designed and synthesized a new N,N′-bis(4-methylenepyridin-4-yl)benzene-1,4-dicarboxamide (4-bmpbd) separated by −CH2−acylamino−phenyl−acylamino−CH2− groups as ligand, which is expected to exhibit both flexible and semi-rigid properties in the assembly of CPs. On the other hand, polycarboxylic acids with multiple coordination modes as O-donor ligands can satisfy the coordination requirements of the central metals by their “breathing” behavior in the solid state, which make them a kind of excellent co-ligands in the construction of CPs.19 Therefore, the mixed ligand assembly system combining pyridyl-amide-based ligands with polycarboxylate anions has been applied for the construction of novel CPs with different dimensionalities.20 In recent years, our group

also

investigated

the

pyridylacylamide-based

CPs

with

Nevertheless,

on

mixed

reports

assembly various ligand

of

polycarboxylate-assisted

dimensionalities assembly

and

system

functions.21 of

special

bis-pyridyl-bis-amide and polycarboxylates with different substitute groups, carboxyl position and number are still limited. Thus, we selected nine different kinds of aromatic polycarboxylates as the co-ligands, namely, 4-hydroxybenzoic acid (4-HHBC), 2,2'-biphenyldicarboxylic acid (2,2′-H2BDC), 4,4'-oxybis(benzoic acid) (H2OBA),

2,5-(s-acetic

acid)dimercapto-1,3,4-thiadiazole

(H2ADTZ),

1,3-adamantanedicarboxylic acid (1,3-H2ATDC), 3-nitrophthalic acid (3-H2NPH), 5-nitroisophthalic

acid

(H2NIP),

5-hydroxyisophthalic

acid

(H2HIP)

and

1,3,5-benzenetricarboxylic acid (1,3,5-H3BTC), to combine with 4-bmpbd ligand, aiming at constructing new target CPs and investigating the effect of carboxyl position and number, as well as the functional groups of polycarboxylates on the 3



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structures of CPs (Scheme 1). In this paper, nine new CdII complexes, namely, [Cd3(4-bmbpd)4Cl6(H2O)2] (1), [Cd(4-bmbpd)(2,2′-BDC)(H2O)]

(2),

[Cd(4-bmbpd)(OBA)]·H2O

(3),

[Cd(4-bmbpd)0.5(ADTZ)(H2O)]·H2O (4), [Cd4(4-bmbpd)(1,3-ATDC)4(H2O)6]·2H2O (5),

[Cd(4-bmbpd)(3-NPH)(H2O)]·H2O

(6),

[Cd(4-bmbpd)0.5(NIP)(H2O)]

(7),

[Cd(4-bmbpd)0.5(HIP)]·H2O (8), [Cd3(4-bmbpd)2(1,3,5-BTC)(H2O)4]·4H2O (9), have been synthesized with hydrothermal/solvothermal technique. We have discussed the effect of polycarboxylate co-ligands on the frameworks of the title CPs. Moreover, complexes 2–4 and 7–9 were selected as representative examples to study the effects of different organic solvents on the fluorescent behaviors, and the photocatalytic properties of 1–9 under UV irradiation have also been investigated. (Insert Scheme 1)

Experimental Section Materials and general methods: All the materials and reagents were purchased from commercial

sources

and

employed

without

N,N′-bis(4-methlenepyridin-4-yl)benzene-1,4-dicarboxamide

further

purification.

(4-bmpbd)

and

2,5-(s-acetic acid)dimercapto-1,3,4-thiadiazole (H2ADTZ) were prepared according to the literature.22, 23 FT-IR spectra were recorded on a Varian-640 spectrometer (KBr pellets). Thermogravimetric analyses (TGA) were measured on a Pyris Diamond TG instrument. Powder X-ray diffraction (PXRD) data were measured with a Ultima IV with D/teX Ultra diffractometer at 40 kV, 40 mA with Cu-Kα (λ = 1.5406 Å) radiation. Fluorescence spectra were taken on a Hitachi F-4500 fluorescence/phosphorescence spectrometer. Diffuse reflectance spectra were measured with Lambda-750 spectrometer. Electrochemical measurements were performed using a CHI 750E B14657 Electrochemical Workstation. UV-Vis absorption spectra were carried out with a SP-1901 UV-Vis spectrophotometer. Electrochemical measurements Electrochemical tests were carried out with a conventional three-electrode system in a quartz cell filled with 0.5 M Na2SO4 aqueous solution as the electrolyte, with the complex 2/glassy carbon electrode serving as the 4


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working electrode, a platinum electrode as the counter electrode, and a saturated calomel electrode (SCE) as the reference electrode. The working electrode was made by the spin coating method. Preparation of complexes 1–9 Synthesis of [Cd3(4-bmbpd)4Cl6(H2O)2] (1). A mixture containing CdCl2·6H2O (0.046 g, 0.2 mmol), 4-bmpbd (0.035 g, 0.10 mmol), 4-HHBC (0.041 g, 0.30 mmol) and NaOH (0.012 g, 0.30 mmol) in H2O (12 mL) was sealed in a 25 mL Teflon reactor, which was heated at 120 °C for 6 days. After cooling to room temperature, colorless block crystals of 1 were obtained in about 12% yield (based on Cd). IR (KBr, cm−1): 3479w, 3359w, 3261m, 2360w, 1639s, 1544s, 1427s, 1311s, 1226w, 1165w, 1070m, 1020m, 987m, 866m, 777m, 704s, 592w. Synthesis of [Cd(4-bmbpd)(2,2′-BDC)(H2O)] (2). Colorless crystals of 2 was synthesized by a similar procedure to that used for 1, starting from CdCl2·6H2O (0.046 g, 0.2 mmol), 4-bmpbd (0.035 g, 0.10 mmol), 2,2′-H2BDC (0.048 g, 0.20 mmol), NaOH (0.016 g, 0.40 mmol) and H2O (12 mL). Yield: 25% (based on Cd). IR (KBr, cm−1): 3307w, 2364w, 1660s, 1543s, 1411s, 1290s, 1224w, 1149w, 1112w, 1066w, 1016m, 856s, 779m, 744m, 682m, 621m. Synthesis of [Cd(4-bmbpd)(OBA)]·H2O (3). Complex 3 was obtained as colorless crystals by a similar route to that used for 2, except that 2,2′-H2BDC was replaced by H2OBA (0.052 g, 0.20 mmol). Yield: 30% (based on Cd). IR (KBr, cm−1): 3531w, 3265w, 2364w, 1651s, 1595s, 1544s, 1325w, 1224s, 1159s, 1064m, 1020, 875s, 785s, 659s, 543w. Synthesis of [Cd(4-bmbpd)0.5(ADTZ)(H2O)]·H2O (4). Complex 4 was gained as colorless crystals by a similar route to that used for 2, except that 2,2′-H2BDC was replaced with H2ADTZ (0.054 g, 0.20 mmol) and different composition of solvent H2O-DMF (12 mL, v/v = 5 : 1). Yield: 28% (based on Cd). IR (KBr, cm−1): 3342w, 2368w, 1651s, 1558s, 1396s, 1317m, 1234s, 1168m, 1060s, 1016m, 989m, 927m, 873s, 790s, 746s, 717m, 659s, 545w. Synthesis of [Cd4(4-bmbpd)(1,3-ATDC)4(H2O)6]·2H2O (5). Colorless block 5



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crystals of pure 5 was prepared with the similar procedure to 2, except 1,3-H2ATDC (0.044 g, 0.2 mmol) replacing 2,2′-H2BDC. Yield: 26% based on Cd. IR (KBr, cm−1): 3369w, 2906w, 2366w, 1643s, 1535s, 1411s, 1311s, 1126m, 1064m, 1022m, 989m, 866w, 821m, 781m, 713s, 646w. Synthesis of [Cd(4-bmbpd)(3-NPH)(H2O)]·H2O (6). The synthetic procedure of 6 (colorless blocks) was same as complex 2 except that 3-H2NPH (0.042 g, 0.20 mmol) was used to replace 2,2′-H2BDC. Yield: 18% based on Cd. IR (KBr, cm−1): 3628w, 3267w, 2360w, 1652s, 1556s, 1431s, 1386s, 1348s, 1301s, 1228m, 1155m, 1066m, 1020m, 923s, 846s, 788m, 713s, 623m, 534m, 472m. Synthesis of [Cd(4-bmbpd)0.5(NIP)(H2O)] (7). Colorless block crystals of 7 was synthesized by a similar route to that of 2, except that H2NIP (0.042 g, 0.20 mmol) was used to replace 2,2′-H2BDC. Yield: 20% based on Cd. IR (KBr, cm−1): 3365w, 2362w, 1618s, 1541s, 1429s, 1371s, 1224w, 1157w, 1074m, 1018m, 923m, 862m, 786s, 732s, 721m. Synthesis of [Cd(4-bmbpd)0.5(HIP)]·H2O (8). Complex 8 was gained as colorless crystals by a similar route to that used for 2, except that H2HIP (0.036 g, 0.20 mmol) was employed to replace 2,2′-H2BDC. Yield: 24% (based on Cd). IR (KBr, cm−1): 3479w, 3265w, 2362w, 1652s, 1616m, 1541s, 1429m, 1386s, 1303w, 1265w, 1105w, 1064w, 972w, 896w, 783s, 732s, 678w, 547w. Synthesis of [Cd3(4-bmbpd)2(1,3,5-BTC)(H2O)4]·4H2O (9). Complex 9 was synthesized as colorless crystals by a similar route to that used for 2, except that 1,3,5-H3BTC (0.042 g, 0.2 mmol) was employed to replace 2,2′-H2BDC and different amount of NaOH (0.024 g, 0.60 mmol). Yield: about 23% based on Cd. IR (KBr, cm−1): 3275w, 2362w, 1647s, 1614s, 1541s, 1425m, 1363s, 1294w, 1226w, 1109w, 1062w, 1018m, 867w, 729s, 690m, 617w, 516m. X-ray crystallography: Crystal data for 1−9 were collected at 296(2) K on a Bruker SMART APEX II diffractometer equipped with a CCD area detector and graphite-monochromated Mo-Kα (λ = 0.71073 A˚) with the φ-ω scan technique. All the structures were solved and refined anisotropically using the programs SHELXS 6


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and SHELXL.24 All non-hydrogen atoms were refined with anisotropic thermal parameters. The H atoms of the organic ligands were placed theoretically and treated isotropically. The H atoms of the coordinated or lattice water molecules in 3, 5, 6 and 9 were not located in the different Fourier maps but were added to their formulas. The O2 in complex 5 was restricted by the ‘isor’ command. Crystallographic data and details of structure refinement for 1−9 are summarized in Table 1. Selected bond lengths and angles of the title complexes were listed in Tables S1a−S1i in the Supporting Information. The H-bonding parameters of complexes 2, 3, 5 and 6 are listed in Tables S2a−S2d. The CCDC numbers 1445598-1445606 for compounds 1−9 as the supplementary crystallographic data can be got free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB21EZ, UK ; fax: (+44) 1223−336−033; or [email protected]]. Results and Discussion Description of crystal structures of complexes 1–9 Crystal Structure of [Cd3(4-bmbpd)4Cl6(H2O)2] (1). Complex 1 belongs to the P21/c space group, and its unit contains three CdII cations, four 4-bmbpd ligands, six chloride anions and two coordinated water molecules. In 1, there are two crystallographically independent CdII centers (Fig. 1a). The Cd1 and Cd2 centers exhibit {CdCl4N2} and {CdCl3N2O} coordination environment, respectively, with distorted octahedral geometries. The Cd1 is six-coordinated by four chloride ions [Cd1–Cl = 2.593(7)–2.628(7) Å] and two nitrogen atoms from the pyridyl of two 4-bmbpd molecules [Cd1–N1 = Cd1–N1#1 = 2.376(2) Å]. The Cd2 is also six-coordinated by three chloride ions [Cd2–Cl = 2.557 (7)–2.673 (7) Å], two nitrogen atoms [Cd2–N5 = 2.304(2) Å, Cd2–N4#2 = 2.338(2) Å] from pyridyl groups of two 4-bmbpd and one oxygen atom of the coordinated water molecule with the distance of Cd2–O1W = 2.381(2) Å. In complex 1, the chloride anions and 4-bmbpd ligands display two kinds of coordination fashions: The Cl3 anion in a µ1-mode only coordinates to the Cd2 ion. 7



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Two pairs of Cl- (Cl1 and Cl2) in a µ2-bridging mode join three CdII ions (one Cd1 and two Cd2 ions) to form a trimetallic unit [Cd3Cl6]. Two 4-bmbpd ligands with a µ1-coordination mode, as well as two water molecules hang on the trinuclear unit by sharing with Cd2 ions to form a [Cd3(4-bmbpd)2Cl6(H2O)2] subunit, which are further connected by µ2-bridging 4-bmbpd to generate a 1D wave-like double chain (Fig. 1b). In our previous studies, we have obtained a complex [Cd(4-bpcb)1.5Cl2(H2O)]25 containing

dinuclear

subunit

[Cd2Cl4(4-bpcb)2(H2O)2]n

(4-bpcb=N,N-bis(4-pyridinecarboxamide)-1,4-benzene). While complex 1 consists of trinuclear subunits [Cd3(4-bmbpd)2Cl6(H2O)2]. Such trinuclear subunit is rarely reported to the best of our knowledge. (Insert Fig. 1) The

X-ray

crystallographic studies shows that compound 2 also belongs to the P21/c

space

Crystal

Structure

of

[Cd(4-bmbpd)(2,2′-BDC)(H2O)]

(2).

group. Its asymmetric unit is comprised of one CdII center, one 4-bmbpd, one 2,2′-BDC2- anion and one coordinated water molecule. As shown in Fig. 2a, the CdII center is surrounded by two pyridyl nitrogen atoms from two 4-bmbpd molecules [Cd1–N1 = 2.358(3) Å, Cd1–N4 = 2.374(3) Å], five oxygen atoms of two carboxyl groups from two 2,2′-BDC2- anions and one coordination water molecule with Cd–O bond lengths of 2.281(3)–2.530(3) Å, displaying a distorted pentagonal bipyramid geometry {CdN2O5}. In 2, 4-bmbpd take a bidentate bridging mode linking the adjacent CdII ions, giving a 1D [Cd-4-bmbpd]n zigzag chain. Meanwhile, two carboxyl groups of 2,2′-BDC2present a bidentate chelating mode linking the neighbouring CdII centers to generate 1D [Cd-2,2′-BDC]n single-strand helix chains (Fig. 2b). The [Cd-4-bmbpd]n and [Cd-2,2′-BDC]n chains connect to each other leading to a 2D 4-connected network (Fig. 2c and 2d). Moreover, the parallel sheets are gathered together through hydrogen bond between O atoms from 2,2′-BDC2- and coordination water molecules and N atoms from 4-bmbpd ligands [O(1W)–H(1WA)···O(1) = 2.749(4) Å and N(3)–H(3B)···O(2) = 2.956(4) Å], to construct a 3D supramolecular architecture (Fig. 8


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S1). (Insert Fig. 2) Crystal Structure of [Cd(4-bmbpd)(OBA)]·H2O (3). Complex 3 also crystallizes in P21/c space group, which is composed of a CdII center, a 4-bmbpd, an OBA2- anion and a lattice water molecule. As illustrated in Fig. 3a, the Cd1 center shows a six-coordinated {CdN2O4} octahedral geometry with two N atoms from pyridyl groups of two 4-bmbpd molecules [Cd1–N1 = 2.296(4) Å, Cd1–N3 = 2.252(3) Å] and four carboxyl oxygens from two OBA2- anions with Cd–O bond lengths from 2.301(3) to 2.263(3) Å. In 3, the carboxyl groups of OBA2- ligand adopting a µ1-η0:η1 mode link the neighbouring CdII centers to yield a 1D [Cd-OBA]n linear chain. Two types of µ2-bridging 4-bmbpd ligands connect the CdII ions alternately with the Cd···Cd distances of 18.390(10) and 20.029(1) Å, respectively, forming a 1D [Cd-4-bmbpd]n wave chain (Fig. 3b). These two kinds of 1D chains are alternatively interlaced by sharing CdII ions, generating a 2D 4-connected network (Fig. 3c and 3d). In addition, the final 3D supramolecular framework is obtained due to the nitrogen atoms of 4-bmbpd ligands via hydrogen bonds to the carboxyl oxygens of OBA2- anions [N(4)–H(4B)···O(2), N···O = 2.892(5) Å] (Fig. S2). Chen group has reported a 2D network {[Cd(OBA)(L1)]·2H2O}n [L1 = N,N′-di(4-pyridyl)adipoamide]20, in which the CdII centers are interconnected by two L1 and two OBA2- anions. Thus a 1D infinite helical channels formed, which is polycatenated by two others, resulting in a 1D → 2D polycatenated framework. Obviously, the structure is different from 3, which indicates that the N-containing ligands play a critical role in the formation of final architecture. (Insert Fig. 3) Crystal Structure of [Cd(4-bmbpd)0.5(ADTZ)(H2O)]·H2O (4). Complex 4 belongs to Pī space group. Its asymmetric unit is composed of a CdII cation, half 4-bmbpd, one ADTZ2- anion, one coordinated water and one crystal water molecule. Fig.

4a

shows

the

coordination

environment

of

CdII

center,

which

is 9



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seven-coordinated in distorted pentagonal bipyramid geometry with one pyridyl N atom of one 4-bmbpd, four carboxyl oxygens of two ADTZ2- anions, one amido oxygen of one 4-bmbpd and one oxygen atom from coordinated water molecule. The Cd–N bond length is 2.334(4) Å and Cd–O bond lengths are 2.265(4)–2.574(4) Å. In 4, a pair of ADTZ2- anions bind to two CdII centers to form a [Cd2(ADTZ)2] rectangle unit with a dimension of 8.448 Å × 8.105 Å, which were linked by the pyridyl groups from the 4-bmbpd molecules to construct a 1D “paddlewheel” chain (Fig. 4b). Such 1D “paddlewheel” chains are further joined together through the amide groups of 4-bmbpd ligands, giving rise to a novel 2D architecture (Fig. 4c). A better understanding of the nature of the 2D network can be supplied by topology analysis. In the whole structure of 4, the CdII ion can be considered as a 4-connected node, the ADTZ2- anion and the 4-bmbpd ligand can be regarded as 2-/4-connectors, respectively. Hence, the structure of 4 can be reduced to a trinodal (2,4,4)-connected network with {42·82·102}{42·84}2{4}2 topology (Fig. 4d). (Insert Fig. 4) Crystal

Structure

of

[Cd4(4-bmbpd)(1,3-ATDC)4(H2O)6]·2H2O

(5).

Single-crystal diffraction analysis indicates that the crystallographic space group of complex 5 is P21/c. The asymmetric unit contains four CdII cations, one 4-bmbpd ligand, four 1,3-ATDC2- anions, six coordinated water molecules and two crystal water molecules. As depicted in Fig. 5a, there are four crystallographically independent CdII centers. The Cd1 and Cd3 centers exhibit a {CdNO5} distorted octahedral geometry constructed from one pyridyl nitrogen atom of one 4-bmbpd ligand [Cd1–N1 = 2.272(2) Å, Cd3–N4 = 2.273(2) Å] and five oxygen atoms from two carboxyls of two 1,3-ATDC2- ions [Cd–O = 2.240(2)–2.413(3) Å] and one coordinated water molecule. Equally, the Cd4 cation also shows a distorted octahedral coordination geometry, coordinating to five carboxyl oxygens from two 1,3-ATDC2anions and two oxygens from coordinated water, respectively [Cd–O = 2.223(2)–2.406(2) Å]. The Cd2 center is seven-coordinated by seven oxygen atoms from one 4-bmbpd ligand, two 1,3-ATDC2- ions and two coordinated water molecules 10


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with the Cd–O distances in the range of 2.249(19)–2.539(2) Å. In case of 5, the completely deprotonated 1,3-ATDC2- ions exhibits a bis(bidentate) bridging mode. Two pairs of CdII ions coordinate with four 1,3-ATDC2- anions to generate a [Cd4(1,3-ATDC)4] loop. It is worth to mention that the 4-bmbpd ligand shows two kinds of coordination modes: bidentate (with two pyridyl groups) and tetradentate (with two pyridyl groups and two amide groups) coordination modes. Such two types of ligands connect the [Cd4(1,3-ATDC)4] rings alternately with ···ABAB··· mode, resulting in the construction of a 1D rotiform chain (Fig. 5b and 5c). Adjacent infinite 1D chains are expanded into the 2D supramolecular network due to the oxygen atoms from 4-bmbpd ligands via the hydrogen bonding interactions to coordinated water molecules [O(6W)–H(6WB)···O(17), O···O = 2.896(3) Å] (Fig. S3). (Insert Fig. 5) Crystal Structure of [Cd(4-bmbpd)(3-NPH)(H2O)]·H2O (6). The complex 6 is crystallized in Pī space group, which is constituted by one CdII ion, one 4-bmbpd ligand, one 3-NPH2- ion, one coordination water molecule, along with a free water molecule. The CdII center exhibits an octahedral geometry, which is composed of two pyridyl nitrogens of two 4-bmbpd molecules [Cd1–N4 = 2.303(15) Å, Cd1–N1 = 2.340(15) Å] and four O atoms from three carboxylate groups of two 3-NPH2- anions and one coordination water molecule, respectively [Cd–O = 2.260(12)–2.330(12) Å] (Fig. 6a). In complex 6, the carboxyl from 3-NPH2- ion adopt different coordination fashions: one takes a µ2-η1:η1 bridging mode to connect two CdII ions, while the other one furnish a µ1-η0:η1 monodentate mode. As shown in Fig. 6b, two 3-NPH2- anions join a pair of CdII cations constructing a binuclear [Cd2(3-NPH)2] unit. A pair of 4-bmbpd as bidentate ligands with a µ2-bridging mode link the adjacent [Cd2(3-NPH)2] units, generating a 1D ladder-shaped chain. These 1D chains are further linked into a 2D supramolecular structure by Owater–H···O bonds [O(1W)–H(1WA)···O(1), O···O = 2.702(19) Å] between carboxylate groups of 3-NPH2- anions and coordinated water molecules (Fig. 6c). Finally, a 3D supramolecular framework is constructed also 11



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Page 12 of 25

through N–H···O bonds [N(3)–H(3A)···O(3), N···O = 2.831(2) Å] between 4-bmbpd ligands and 3-NPH2- anions (Fig. S4). (Insert Fig. 6) Crystal Structure of [Cd(4-bmbpd)0.5(NIP)(H2O)] (7). Complex 7 belongs to the C2/c space group with one CdII ion, half 4-bmbpd molecule, one NIP2- ion and a coordinated water molecule. Each CdII cation is square-pyramidally surrounded by a pyridyl N atom of the 4-bmbpd molecule with the Cd–N bond length of 2.325(3) Å and four oxygens from one 4-bmbpd ligand, two NIP2- and a coordinated water molecule, respectively [Cd–O = 2.262(3)–2.289(3) Å] (Fig. 7a). In case of 7, the NIP2- ion taking a bis(monodentate) bridging mode integrates with neighboring CdII centers to generate a 1D zigzag chain (Fig. 7b). Interestingly, these zigzag chains are bridged by 4-bmbpd ligands to furnish a 1D ladder-like double chain with rectangular windows (Fig. S5), which further interwoven with each other to generate a 2D sheet (Fig. 7c). Finally, these 2D sheets are connected through the amide groups of 4-bmbpd to construct a 3D self-penetrating framework (Fig. 7d). From the topological perspective, both CdII ion and the 4-bmbpd ligand are regarded as 4-connected nodes and the NIP2- anions can be defined as junctors. Therefore, the whole structure of 7 can be topologically described as a (4,4)-connected framework with the Schläfli symbol {4·64·8}2{42·84} (Fig. 7e). We have reported an 8-connected 3D

framework

[Cd(bbbm)(NIP)]

(bbbm

=

1,1-(1,4-butanediyl)bis-1H-benzimidazole).26 Different from 7, in this complex the CdII ion is six-coordinated and the NIP2- anion shows a bridging/chelating mode. (Insert Fig. 7) Crystal Structure of [Cd(4-bmbpd)0.5(HIP)]·H2O (8). Complex 8 shows the Pī space group. The asymmetric unit contains one CdII center, half 4-bmbpd molecule, one HIP2- ion and a free water molecule. In Fig. 8a, each CdII center exhibits six-coordinated {CdNO5} distorted octahedron geometry, firmly bonded by a N atom from one 4-bmbpd ligand, four carboxyl oxygen atoms and one –OH oxygen atom from four HIP2- anions. The Cd–N bond length is 2.298(17) Å and the Cd–O bond 12


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lengths are from 2.180(14) to 2.574(15) Å. In 8, the two carboxyl groups of HIP2- anions presenting a chelating and a bis(monodentate) bridging mode, respectively, coordinated to the CdII ions, resulting in an infinite 1D [Cd-HIP]n double chain. These 1D chains are further linked through oxygen atoms of –OH from HIP2- anions, affording an interesting 2D layered motif (Fig. 8b). Finally, the adjoining 2D layers are connected by 4-bmbpd ligands with µ2-bridging mode, generating a 3D framework (Fig. 8c). From the point view of topology, the CdII ion center and the HIP2- are regarded as a 5-/4-connected node, and 4-bmbpd is considered as linkers. So the whole framework of 8 can be topologically described as a binodal (4,5)-connected framework with the Schläfli symbol {44·62}{44·66} (Fig. 8d). The architecture of 8 is very different from the reported complexes:

{[Cd(L1)(hip)]·4H2O}n

and

{[Cd(L2)(hip)]·3H2O}n21

N,N-di(pyridin-3-yl)pyridine-2,6-dicarboxamide,

L2

([L1

= =

N,N-di(pyridin-3-yl)pyridine-3,5-dicarboxamide), which are based on the same metal center and auxiliary carboxylate. It can be seen that the different pyridyl-amide-based ligands show significant influence on the structural differences. (Insert Fig. 8) Crystal Structure of [Cd3(4-bmbpd)2(1,3,5-BTC)(H2O)4]·4H2O (9). X-ray diffraction result indicates that 9 also belongs to the Pī space group. The asymmetric unit consists of two crystallographically independent CdII cations, which exhibit the similar octahedron geometry. As shown in Fig. 9a, the Cd1 center is firmly bonded by two pyridyl N atoms of two 4-bmbpd molecules, two carboxyl oxygen atoms of two 1,3,5-BTC3- and two oxygen atoms of coordinated water molecules. The Cd2 center is coordinated by two N atoms of two 4-bmbpd molecules, three carboxyl O atoms of two 1,3,5-BTC3- anions and one O atom from coordinated water molecule. The Cd–N bond lengths are of 2.331(4)–2.360(4) Å and the Cd–O bond lengths are from 2.214(3) to 2.496(4) Å. In 9, there are two types of 4-bmbpd ligands described as trans-4-bmbpd and cis-4-bmbpd (Fig. S6a). Two independent cis-4-bmbpd ligands connect CdII cations 13



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Page 14 of 25

giving closed [Cd2(4-bmbpd)2] rings with the Cd···Cd distance of 34.042 Å, which are linked through 1,3,5-BTC3- ions to afford a charming chain (Fig. S6b ). It is noted that the trans-4-bmbpd ligands link these 1D chains to furnish a novel 2D network (Fig. 9b). The Cd···Cd distance separated by trans-4-bmbpd is 20.461 Å. Two carboxyl groups of 1,3,5-BTC3- adopting a chelating and a monodentate mode, respectively, connect with Cd2 centers alternately and the third carboxyl group presenting a monodentate mode links the Cd1 center, giving a 1D ladder-shape double chain (Fig. 9c). Interestingly, the adjacent 2D layers are expanded to a 3D framework through these 1D ladder-like chains (Fig. 9d). In order to better describe the framework of complex 9, Cd1/Cd2 centers are defined as 4-connected nodes, 1,3,5-BTC3- anion and cis-4-bmbpd can be regarded as 3-/2-connectors and trans-4-bmbpd is viewed as linker. Hence, the 3D structure of complex 9 can be simplified as a (2,3,4,4)-connected framework (Fig. 9e). (Insert Fig. 9) Influence of the polycarboxylates on the architectures of complexes 1-9 In this paper, eight polycarboxylates with different flexibility, functional groups as well as carboxyl position and number were selected to assemble with CdII ion and 4-bmbpd ligand, aiming to survey their influence on the final structures of the title complexes. In complex 1, a monocarboxylic acid 4-HHBC was used in the synthesis, but not contained in the final molecular formula. However, we can still successfully obtained complex 1 without 4-HHBC as auxiliary ligand, which indicated that monocarboxylic acid may not play a significant role in the forming process of 1. Complex 1 shows 1D wave chain constructed from CdII ions, 4-bmbpd ligands and Cl anions, in which both the 4-bmbpd ligands and the Cl anions display two kinds of connection modes: µ2-bridging mode and µ1-mode acting as terminal group (Scheme 1). The Cd···Cd distance separated by µ2-4-bmbpd is 19.932(18) Å. In order to generate different structural motifs, we introduced several of polycarboxylates in complexes 2–9. When a rigid aromatic dicarboxylic acid 2,2′-H2BDC was used, complex 2 with 2D grid-like network was obtained. In 2, each carboxyl group from 14


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2,2′-BDC2- anions with µ1-η1:η1 mode link the neighboring CdII centers to generate 1D [Cd-2,2′-BDC]n single-strand helix chains. The 4-bmbpd ligands take a µ2-bridging mode joining the adjacent CdII cations, giving 1D [Cd-4-bmbpd]n zigzag chains with the Cd···Cd length of 19.858(15) Å. This two kinds of chains share CdII centers resulting in the final 2D 4-connected sheet. When a flexible dicarboxylic acid H2OBA was used in complex 3, as expected, a different 2D layer was obtained. In 3, each carboxyl group of the OBA2- ion adopting a µ1-η1:η1 mode link the adjacent CdII cations to yield a 1D [Cd-OBA]n chain. The 4-bmbpd ligands with µ2-bridging mode connect the CdII ions forming a 1D [Cd-4-bmbpd]n wave-like chain, in which there are two kinds Cd···Cd distances of 18.390(10) and 20.029(1) Å, respectively. These two kinds of chains are alternatively interweaved with each other, generating the 2D 4-connected architecture. When another much more flexible dicarboxylic acid H2ADTZ was used instead of H2OBA, complex 4 with a novel 2D architecture was yielded, which is very different from 2 and 3. In 4, a pair of ADTZ2- anions bind to two CdII centers to form a [Cd2(ADTZ)2] rectangle unit, in which the carboxyl groups also adopt µ1-η1:η1 coordination mode. These [Cd2(ADTZ)2] units are further linked by the 4-bmbpd ligands with µ4-bridging mode, leading to the novel 2D structure. The Cd···Cd separation of crosswise and lengthways are 20.831(17) and 10.919(11) Å, respectively. When a “V”-shape dicarboxylic acid 1,3-H2ATDC was used in complex 5, each carboxyl group of the 1,3-ATDC2- anions with µ1-η1:η1 coordination mode joins the CdII cations to generate [Cd4(1,3-ATDC)4] loops. The 4-bmbpd ligands with µ2-/µ4-bridging modes integrate these [Cd4(1,3-ATDC)4] rings alternately, resulting in the 1D rotiform chain, in which the distances of Cd···Cd separated by µ2-4-bmbpd and µ4-4-bmbpd are 20.421(5) Å and 20.190(5) Å, respectively. Obviously, the dimensionality of 5 is decreased compared with 2–4. When two structural relative nitro-containing dicarboxylate 3-H2NPH and H2NIP were selected in complexes 6 and 7 (3-H2NPH for 6 and H2NIP for 7), we got two completely different structures. Complex 6 displays a 1D ladder-shaped chain, while 7 reveals a 3D self-penetrating architecture. In 6, the two carboxylate groups of 3-NPH2- anion take µ2-η1:η1 and 15



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Page 16 of 25

µ1-η0:η1 coordination modes, respectively, bridging the Cd centers to form [Cd2(3-NPH)2] units, which are further connected by the µ2-bridging ligand 4-bmbpd. In 7, the carboxylate groups of the NIP2- anion adopting µ1-η0:η1 coordination mode integrate with adjacent Cd centers to furnish 1D zigzag chains, which are further bridged through 4-bmbpd ligands to form double chains. Adjacent 1D double chains interwoven with each other to generate a 2D layer. These 2D layers are further extended to the final 3D framework by the amide groups of 4-bmbpd molecules. For complexes 6 and 7, the nitryl groups in 3-NPH2- and NIP2- show no obvious effect on the whole structures. However, the location of the carboxyls from 3-NPH2- and NIP2determines the final architectures of 6 and 7. We also tried to increase the coordination site and the carboxyl number of polycarboxylates to improve the dimensionality of target complexes. So the H2HIP with –OH group and the 1,3,5-H3BTC with extra carboxyl group were selected in 8 and 9, respectively. In 8, the carboxyl groups of HIP2- anions presenting µ1-η1:η1 and µ2-η1:η1 modes coordinate with the CdII ions, resulting in infinite 1D [Cd-HIP]n double chains, which are further linked through oxygen atoms of –OH from HIP2- anions to afford 2D layered motifs. Finally, neighboring layered motifs are further stabilized by 4-bmbpd with µ2-bridging mode to yield the 3D framework. In 9, two carboxyl groups of 1,3,5-BTC3- adopting µ1-η1:η1 and µ1-η0:η1 modes connect with Cd2 centers alternately and the third carboxyl groups presenting µ1-η0:η1 mode link the Cd1 centers, giving 1D ladder-like double chains. Two independent cis-4-bmbpd ligands connect CdII cations giving closed [Cd2(4-bmbpd)2] loops, which are infinitely extended through 1,3,5-BTC3- to afford charming 1D chains. These 1D chains are connected by the trans-4-bmbpd to form novel 2D sheets. The adjacent 2D sheets are stacked into a 3D framework through the 1D ladder-like chains. Make a long story short, the structural differences indicate that the location and number of the carboxyl groups, the functional groups and flexibility of polycarboxylates show significant effects on the diverse structures of the title compounds (Scheme 2). 16


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(Insert Scheme 2 ) Powder X-ray Diffraction and Thermal Analyses. To characterize the phase purity of the obtained bulky sample, powder X-ray diffraction (PXRD) experiments have been recorded (Fig. S8). The measured PXRD patterns of title complexes agree well with their corresponding simulated patterns, indicating the pure crystals have been successfully synthesized. To examine the thermostabilities of title complexes, TG analyses were performed (Fig. S9). The TG curves of 1–9 show two separate weight loss steps. The initial weight loss stages are observed in the range of 184–206 for 1, 94–132 for 2, 156–187 for 3, 137–185 for 4, 150–182 for 5, 97–136 for 6, 161–221 for 7, 153–179 for 8 and 159–203 °C for 9, with the weight loss of approximately 1.95, 2.43, 2.52, 6.07, 7.49, 5.03, 3.60, 3.62 and 7.71%, respectively, demonstrating the removal of coordinated and/or free water molecules (calcd. 1.83, 2.51, 2.46, 6.14, 7.87, 5.11, 3.51, 3.73 and 7.47%). The further weight loss occurred in the range of 266–396 °C for 1, 311–620 °C for 2, 267–442 °C for 3, 227–405 °C for 4, 342–493 °C for 5, 252–345 °C for 6, 321–447 °C for 7, 364–482 °C for 8 and 339–426 °C for 9, indicating the decomposition of organic components. Photoluminescent Properties CPs constructed by d10 metal ions have been studied extensively due to their photoluminescent properties and their potential applications as fluorescent materials.27-29 In this work, the fluorescent properties of complexes 1−9 and the free ligand (4-bmpbd) have been studied in the solid state at room temperature. The emission spectra of the title CPs and 4-bmpbd are presented in Fig. 10. It was considered that there is no obvious contribution for the polycarboxylate ligands to the luminescence emission of the CPs in the presence of the N-containing ligands.30 The free 4-bmpbd molecules show intense emission bands with maxima about 398 nm (λex = 280 nm), which is probably ascribed to the π*→π transitions.31, 32 The luminescence of CPs 1–9 was observed in the solid state and their emission spectra also exhibit similar shoulder peaks at ca. 398 nm (λex = 280 nm) (398 for 1, 398 for 2, 397 for 3, 17



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Page 18 of 25

398 for 4, 397 for 5, 400 for 6, 403 for 7, 396 for 8 and 399 for 9), which are very close to that of free 4-bmpbd. The fluorescent emission of 1–9 can be attributed to the intraligand π*→π and n→π* transitions.33, 34 The difference of luminescent intensities among the title complexes might be ascribed to the different flexibility and compactness of the structures and organic components.21 (Insert Fig. 10) Herein complexes 2–4 and 7–9 were selected to further investigate the effects of organic solvent molecules on fluorescent behaviors. We first examined the solid-state photoluminescent properties of 2–4 and 7–9 with diverse solvent molecules (defined as 2-solvent, 3-solvent, 4-solvent, 7-solvent, 8-solvent and 9-solvent, respectively). The simples were prepared as follows: 250 mg of 2 was ground into a fine powder and immersed in 5 mL CH3OH for 3 d. The solvent exchanged samples were evacuated at 60 °C for 1 h and then 120 °C for over 3 h. Following, we dispersed 10 mg of desolvated 2 into 3 mL of solvent (either MeOH, EtOH, DMF, DMA, Benzene, Methylbenzene, nitrobenzene (NB), CH2Cl2, THF, DMSO or CH3CN) for 72 h and the fluorescent sample was collected after drying. The same procedure was used for the preparation of 3–4-solvents and 7–9-solvents. The Fig. 11 and Fig. S10 present the fluorescent intensities of 2–4-solvents and 7–9-solvents, which show difference with different degrees. The results may be due to the solvent effect.35-37 2-EtOH, 3-MeOH, 3-EtOH, 3-CH2Cl2, 4-Methylbenzene, 7-DMSO and 8-DMA are proved to be the strongest enhancers. In contrast, 2-MeOH, 3-DMA, 4-EtOH, 7-MeOH, 8-DMSO and 9-CH3CN are the most effective quenchers. (Insert Fig. 11) Notably, MeOH for 2 and 7, DMA for 3, EtOH for 4, DMSO for 8 and CH3CN for 9 can obviously quench the fluorescence in contrast to other solvents. To gain a deeper insight

into

the

probabilities

of

above

complexes

as

MeOH/

DMA/EtOH/DMSO/CH3CN probes, the fluorescent spectra of 2-MeOH-H2O, 3-DMA-H2O, 4-EtOH-H2O, 7-MeOH-H2O, 8-DMSO-H2O and 9-CH3CN-H2O with various amounts of corresponding solvents were measured. As shown in Fig. 12 and 18


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Fig. S11, a gradual decrease of the fluorescence intensity for 2-MeOH-H2O, 3-DMA-H2O, 4-EtOH-H2O, 8-DMSO-H2O and 9-CH3CN-H2O can be clearly observed along with increasing MeOH, DMA, EtOH, DMSO or CH3CN content. While compared with 2-MeOH-H2O, the fluorescence intensity of 7-MeOH-H2O inconspicuously decreased upon the increasing of MeOH. The quenching mechanism may be related to the interactions between the complexes and the solvent molecules, as well as the donor–acceptor electron-transfer theory.38–40 In aqueous solution, the hydroxyl groups in MeOH/EtOH may interact with complexes 2 and 4 by H-bonding interactions to open the channels for energy transfer from the samples to solvent molecules.38 While DMA, DMSO and CH3CN with the acyl/sulfinyl/cyano groups can act as electron-acceptors. Therefore, the electrons would transfer from the electron-donating complexes 3, 8 and 9 to DMA/DMSO/CH3CN solvents upon excitation, leading to luminescence quenching.39, 40 In addition, the different structures of title complexes may make great influence on such phenomenon of solvent-dependent

luminescence.41

The

results

above

indicate

that

such

solvent-dependent luminescence for complexes 2–4 and 7–9 would be very useful in detecting both MeOH, DMA, EtOH, DMSO or CH3CN molecules and water molecules simultaneously. (Insert Fig. 12) Optical and electronic properties Crystalline solids 2−5 were selected as represents to measure the diffuse reflectance spectra, aiming to evaluate their semiconductor behaviors and photocatalysis activities of title complexes (Fig. 13). The band gaps (Eg) were confirmed by extrapolation from the linear portion of the absorption edges based on the Kubelka−Munk (KM) method.42 The Eg values of 2−5 estimated according to the steep absorption edge are 3.92, 3.96, 3.54 and 3.95 eV, respectively. In order to determine the semiconductor’s type of complex 2, Mott-Schottky measurements

were

performed

by

using

the

impedance

technique.

The

Mott–Schotty-type plot for 2 at different frequency is displayed in Fig. S12a-d. The 19



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positive slope of the obtained C-2/E plot illustrates that complex 2 belongs to typical n-type semiconductor,42 and its conductive band energy is -1.04 V (vs. NHE). The band gap (Eg) of complex 2 can be calculated from the Tauc equation, which is 3.92 eV. Based on the CB energy level and the band gap, obtained with the formula EVB = ECB +Eg, the valence band (VB) energy level of complex 2 is 2.88 V. Morover, the electrochemical impedance analyses were also performed in the dark and under photoirradiation. As shown in Fig. S12e, the arc radius of 2 under photoirradiation is smaller than that in the dark, which indicates the reduction of impedance. The results show complex 2 has a higher photogenerated charge separation efficiency under photoirradiation.42 (Insert Fig. 13) Photocatalysis Properties Methylene blue (MB) as a model of pollutant is commonly used and difficult to decompose in water. 43-45 Thus, we selected MB for degradation experiments under ultraviolet (UV) light irradiation. The photocatalytic activities of complexes 1−9 were assessed by decomposing MB in water through a typical procedure according to the literature.46 Fig. 14 and Fig. S13 illustrate the time dependent absorption spectra and concentration change of the MB solution degraded by the title complexes. If no photocatalyst or only the 4-bmpbd ligand existed under UV irradiation, there is no obviously decrease for the absorption peaks of MB (Fig. S14a and S14b). The calculation results indicate that the degradation ratio of MB is 45% for 1, 46% for 2, 59% for 3, 60% for 4, 44% for 5, 47% for 6, 47% for 7, 49% for 8 and 44% for 9 (Fig. 15). It can be seen that the photocatalytic activity of complex 4 is the best one, which demonstrates that the differences in the structural features and components of the title complexes may affect their photocatalytic performances.47,48 The possible photocatalytic mechanism for the above photocatalytic processes is as follows: Under UV light irradiation, 4-bmpbd and polycarboxylates ligands were induced to produce O–Cd and/or N–Cd charge transfer, resulting in electron from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular 20


Page 21 of 25

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orbital (LUMO). Generally, in order to return to the stable state of HOMO, the charge transfer excited state was oxygenated water molecules into the •OH active species. Therefore, the •OH radicals would degrade the MB to accomplish the photocatalytic process.49 In order to confirm that the color change of MB is caused by the photocatalytic reaction of coordination polymers, not by the physical adsorption, the control experiment of complex 4 in the dark was carried out (Fig. S14c). Complexes 1−9 could be recycled from the catalytic system by filtration. PXRD patterns of the recycled samples have no evident change compared with pure title complexes (Fig. S8). These results demonstrated that complexes 1−9 may be used as stable photocatalysts in the decomposition of some toxic organic dyes in polluted water. (Insert Fig. 14 and Fig. 15) Conclusions In summary, nine Cd-based complexes have been synthesized by using the semi-rigid

dipyridyl-based

acylamide

ligand

4-bmbpd

and

eight

different

polycarboxylic acids under hydrothermal/solvothermal conditions. Compounds 1–9 display various dimensions (1D for 1, 5 and 6, 2D for 2−4 and 3D for 7−9) and architectures, which indicate that the polycarboxylates with different substitute groups, the carboxyl position and number play significant roles in the final diverse complexes. Moreover, the fluorescent selectivities of the 2–4 and 7–9 for some organic solvents ensure their subsequent applications as fluorescent sensor materials. The photocatalytic activities of 1–9 prove their potential applications in the fields of catalysis. Supporting Information X-ray crystallographic files (CIF) for complexes 1–9, selected bond lengths and angles, general characterizations (PXRD, IR, and TGA) and additional figures. This material is available free of charge via the Internet at http://pubs.acs.org. Acknowledgements This work was financially supported by the National Natural Science Foundation of China (No. 21471021, 21401010, 21501013) and Program for Distinguished 21



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Professor of Liaoning Province (No. 2015399). We also thank Prof. Zhen-Hui Kang from Soochow University for helpful work and discussions on photoelectrochemistry. References (1) Blake, A.; Champness, N.; Hubberstey, P.; Li, W.; Withersby, M.; Schröder, M. Coord. Chem. Rev. 1999, 183, 117−138. (2) Wang, S. L.; Hu, F. L.; Zhou, J. Y.; Zhou, Y.; Huang, Q.; Lang, J. P. Growth Des. 2015, 15, 4087–4097. (3) Banerjee, K.; Roy, S.; Kotal, M.; Biradha, K. Cryst. Growth Des. 2015, 15, 5604–5613. (4) Yao, Z. J.; Yu, W. B.; Huang, S. L.; Li, Z. H.; Jin, G. X. J. Am. Chem. Soc. 2014, 136, 2825−2832. (5) Huang, S. L.; Lin, Y. J.; Andy Hor, T. S.; Jin, G. X. J. Am. Chem. Soc. 2013, 135, 8125−8128. (6) Wang, G. Y.; Yang, L. L.; Li, Y.; Song, H.; Ruan, W. J.; Chang, Z.; Bu, X. H. Dalton Trans. 2013, 42, 12865−12868. (7) Shi, Y. X.; Hu, F. L.; Zhang, W. H; Lang, J. P. CrystEngComm 2015, 17, 9404−9412. (8) Hou, L.; Shi, W. J.; Wang, Y. Y.; Guo, Y.; Jin, C.; Shi, Q. Z. Chem. Commun. 2011, 47, 5464–5466. (9) Yang, W. T.; Gao, M.; Yi, F. F; Sun, Z. M. Cryst. Growth Des. 2012, 12, 5529−5534. (10) Zhao, X. L.; Sun, W. Y. CrystEngComm 2014, 16, 3247−3258. (11) Zhang, K. L.; Hou, C. T.; Song, J. J.; Deng, Y.; Li, L.; Ng, S. W.; Diao, G. W. CrystEngComm 2012, 14, 590−600. (12) Ren, C.; Hou, L.; Liu, B.; Yang, G. P.; Wang, Y. Y.; Shi, Q. Z. Dalton Trans. 2011, 40, 793−804. (13) Sun, H. X.; Xie, W. L.; Lv, S. H.; Xu, Y.; Wu, Y.; Zhou, Y. M.; Ma, Z. M.; Fang, M.; Liu, H. K. Dalton Trans. 2012, 14, 7590−7594. (14) Wang, X. L.; Bi, Y. F.; Liu, G. C.; Lin, H. Y.; Hu, T. L.; Bu, X. H. CrystEngComm 2008, 10, 349−356. (15) Lama, P.; Aijaz, A.; Sañudo, E. C.; Bharadwaj, P. K. Cryst. Growth Des. 2010, 10, 283–290. (16) Cheng, J. J.; Chang, Y. T.; Wu, C. J.; Hsu, Y. F.; Lin, C.; Proserpio, D.; Chen, J. D. 22


Page 23 of 25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


CrystEngComm. 2012, 14, 537−543. (17)Wang, X. L.; Luan, J.; Sui, F. F.; Lin, H. Y.; Liu, G. C.; Xu, C. Cryst. Growth Des., 2013, 13, 3561−3576. (18) Lee, C. H.; Wu, J. Y.; Lee, G. H.; Peng, S. M.; Jiang. J. C.; Lu, K. L. Inorg. Chem. Front. 2015, 2, 965−981. (19) Parshamoni, S.; Sanda, S.; Jena, H. M.; Tomar, K.; Konar, S. Cryst. Growth Des. 2014, 14, 2022−2033. (20) Sie, M. J.; Chang, Y. J.; Cheng, P. W.; Kuo, P. T.; Yeh, C. W.; Cheng, C. F.; Chen J. D.; Wang, J. C. CrystEngComm 2012, 14, 5505–5516. (21) Wang, X. L.; Chen, N. L.; Liu, G. C.; Lin, H. Y.; Zhang, J. W. Eur. J. Inorg. Chem. 2015, 11, 1924–1940. (22) Sarkar, M.; Biradha, K. Cryst. Growth Des. 2006, 6, 202−208. (23) Lou, X. H.; Zhu, Y.; Gao, H.; Zhu, A. X.; Fan, Y. T.; Hou, H. W.; Lu, H. J. Chin. J. Inorg. Chem. 2005, 21, 716–720. (24) Sheldrick, G. M.; Acta Crystallogr., Sect. A:Found. Crystallogr. 2008, 64, 112–122. (25) Wang, X. L.; Sha, X. T.; Liu, G. C.; Chen, N. L.; Gong, C. H.; Qu, Yun. Z. Anorg. Allg. Chem. 2015, 641, 1274–1281. (26) Wang, X. L.; Hou, L. L.; Zhang, J. W.; Zhang, J. X.; Liu, G. C.; Yang, S. CrystEngComm 2012, 14, 3936–3944. (27) Zheng, S. L.; Yang, J. H.; Yu, X. L.; Chen, X. M.; Wang, W. T. Inorg. Chem. 2004, 43, 830−838. (28) Liang, X. Q.; Zhou, X. H.; Chen, C.; Xiao, H. P.; Li, Y. Z.; Zou, J. L.; You, X. Z. Cryst. Growth Des. 2009, 9, 1041−1053. (29) Haldar, R.; Matsuda, R.; Kitagawa, S.; George, S. J.; Maji, T. K. Angew. Chem. Int. Ed., 2014, 53, 11772−11777. (30) Huang, S. L.; Li, X. X.; Shi, X. J.; Hou, H. W.; Fan, Y. T. J. Mater. Chem. 2010, 20, 5695–2706. (31) Chen, S. S.; Zhao, Y.; Fan, J.; Okamura, T.; Bai, Z. S.; Chen, Z. H.; Sun, W. Y. CrystEngComm 2012, 14, 3564−3576. (32) Cheng, P. C.; Kuo, P. T.; Liao, Y. H.; Xie, M. Y.; Hsu, W.; Chen, J. D. Cryst. Growth Des. 2013, 13, 623−632. (33) Ma, J.; Chen, L.; Wu, M. Y.; Zhang, S. Q.; Xiong, K. C.; Han, D.; Jiang, F. L.; 23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 25

Hong, M. C. CrystEngComm 2013, 15, 911−921. (34) Huang, F. P.; Yang, Z. M.; Yao, P. F.; Yu, Q.; Tian, J. L.; Bian, H. D.; Yan, S. P.; Liao, D. Z.; Cheng, P. CrystEngComm 2013, 15, 2657−2668. (35) Shi, B. B.; Zhong, Y. H.; Guo, L. L.; Li, G. Dalton Trans. 2015, 44, 4362−4369. (36) Guo, Z. Y.; Song, X. Z.; Lei, H. P.; Wang, H. L.; Su, S. Q.; Xu, H.; Qian, G. D.; Zhang, H. J.; Chen, B. L. Chem. Commun. 2015, 51, 376−379. (37) Haldar, R.; Rao, K. V.; George, S. J.; Maji, T. K. Chem. Eur. J. 2012, 18, 5848−5852. (38) Shustova, N. B.; Cozzolino, A. F.; Reineke, S.; Baldo, M.; Dincă, M. J. Am. Chem. Soc. 2013, 135, 13326−13329. (39) Wang, Y. N.; Zhang, P.; Yu, J. H.; Xu, J. Q. Dalton Trans. 2015, 44, 1655−1663. (40) Shi, B. B.; Zhong, Y. H.; Guo, L. L.; Li, G.; Dalton Trans. 2015, 44, 4362−4369. (41) Fan, T. T.; Li, J. J.; Qu, X. L.; Han, H. L.; Li, X. CrystEngComm 2015, 17, 9443−9451. (42) Xu, X. X.; Yang, H. Y.; Li, Z. Y.; Liu, X. X.; Wang, X. L. Chem. Eur. J. 2015, 21, 3821–3830. (43) Du, P.; Yang, Y.; Yang, J.; Liu, B. K.; Ma, J. F. Dalton Trans. 2013, 42, 1567−1580. (44) Chen, Y. Q.; Li, G. R.; Qu, Y. K.; Zhang, Y. H.; He, K. H.; Gao, Q.; Bu, X. H. Cryst. Growth Des. 2013, 13, 901−907. (45) Guo, J.; Ma, J. F.; Li, J. J.; Yang, J.; Xing, S. X. Cryst. Growth Des. 2012, 12, 6074−6082. (46) Wang, X. L.; Luan, J.; Lin, H. Y.; Xu, C.; Liu, G. C.; Zhang, J. W.; Tian. A. X. CrystEngComm 2013, 15, 9995–10006. (47) Lin, H. S.; Maggard, P. A. Inorg. Chem. 2008, 47, 8044−8052. (48) Kan, W. Q.; Liu, B.; Yang, J.; Liu, Y. Y.; Ma, J. F. Cryst. Growth Des. 2012, 12, 2288−2298. (49) Wang, C. C.; Li, J. R.; Lv, X. L.; Zhang, Y. Q.; Guo, G. S. Energy Environ. Sci. 2014, 7, 2831–2867.

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(For Table of Contents Use Only)

Polycarboxylate-directed Various Cd(II) Coordination Polymers Based

on

a

Semi-rigid

Bis-pyridyl-bis-amide

Ligand:

Construction, Fluorescent and Photocatalytic Properties Xiu-Li Wang∗, Ying Xiong, Xiao-Ting Sha, Guo-Cheng Liu, and Hong-Yan Lin. Nine CdII complexes have been hydrothermally/solvothermally synthesized using N,N’-bis(4-methylenepyridin-4-yl)-1,4-benzenedicarboxamide as the main ligand and eight polycarboxylates as the auxiliary ligands. The effects of the polycarboxylates on the structures of the title complexes have been discussed.

∗ Corresponding author. Tel.: +86-416-3400158 E-mail address: [email protected] (X.-L. Wang) 1


Coordination Polymers Based on a Semirigid Bis ... - ACS Publications

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