Coordination Polymers Based on Substituted Terpyridine Ligands

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Coordination Polymers based on Substituted Terpyridine Ligands: Synthesis, Structural Diversity, and Highly Efficient and Selective Catalytic Oxidation of Benzylic C-H Bonds Ya-Ru Xi, Wei Wei, Yan-Qing Xu, Xianqiang Huang, Fanzhou Zhang, and Changwen Hu Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.5b00008 • Publication Date (Web): 28 Apr 2015 Downloaded from http://pubs.acs.org on May 3, 2015

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Crystal Growth & Design

Coordination Polymers based on Substituted Terpyridine Ligands: Synthesis, Structural Diversity, and Highly Efficient and Selective Catalytic Oxidation of Benzylic C-H Bonds Yaru Xi†, Wei Wei‡, Yanqing Xu†*, Xianqiang Huang†ǁ*,Fanzhou Zhang†, Changwen Hu* †

†

Key Laboratory of Cluster Science, Ministry of Education of China, Department of Chemistry, Beijing

Institute of Technology, Beijing 100081, P. R China. E-mail: [email protected]; [email protected]. Fax: +86-10-68912631; Tel: +86-10-68918468

‡

Department of Chemistry, Capital Normal University, Beijing 100048, P. R. China.

ǁShandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell Technology, School of Chemistry& Chemical Engineering Liaocheng University, Liaocheng, 252059, P. R. China

Abstract Reaction

of

two

related

rigid (L1)

4’-(4-cynaophenyl)-4,2’:6’,4-terpyridine

(L2),

4’-(4-carboxyphenyl)-4,2’:6’,4-terpyridine

terpyridine and

with

its

transition

ligands, derivative metal

ions

(Co2+,Cu2+/Cu+) afforded four novel coordination compounds: Co(L1)Cl2 (1), Co3(L1)3Cl6 (2), CuI9(L1)4.5(CN)9 (3), [CuII3(L2)6(H2O)6]·4H2O (4). Crystal structure analysis reveals that 1 is comprised of single-stranded 21 helical chains and weak interactions involving C-H…Cl weak hydrogen bonding and π-π stacking interactions 1

ACS Paragon Plus Environment


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exist in the structure. The structure of 2 is comprised of 32 helices which is compared with the compound 1. 3 shows a 3D 4-fold interpenetration structure. 4 exhibits a 1D grid-like belt structure, which further builds 3D supramolecular architecture via π-π stacking interactions. These novel coordination compounds show exceptional catalytic activity for the oxidation of benzylic C-H bonds. Notably, compound 4 show the best catalytic properties for the oxidation of benzylic hydrocarbons up to 99% conv. and 99% sele.. Keywords terpyridine compounds, crystal structure, catalytic oxidation

Introduction Functionalization of C-H bonds is a powerful tool to generate high value chemical feedstock from less expensive raw materials, and has become a central challenge in modern organic chemistry.1-3 In this regard, conversion benzylic hydrocarbons into valuable matters have received considerable attention in recent years.4-5 Despite of the high conversion rate, many benzylic C-H bonds oxidation reactions reported to date rely on homogeneous catalysts and thus recyclability and reusability of these specially-designed catalysts can be problematic.6 Design of the heterogeneous molecular catalysts containing catalytic active sites has proved to be the most valuable strategy to solve this problem. Copper and cobalt compounds has been extensively investigated as oxidation catalyst for oxidation of benzylic C-H bonds.7-14In these catalysts, metal 2


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centers,which are usually coordinated to the N-donor or O-donor ligands such as pyrimidine, imidazole, porphyrins, bipyridines, phenanthrolines and polycarboxylic acids and acted as catalytic active sites, played a crucial role in the catalytical reaction. For example, Su et al. report a polycatenated 3D Cu(II) square-grid MOF, [CuII(bped)2(H2O)2(SiF6)](bped=meso-1,2-bis(4-pyridyl)-1,2-ethanediol)

which

display adsorption behaviors and efficient catalytic activities.10 Multipyridyl ligands of 4,2’:6’,4-terpyridine are a well-known class of ligands which have some advantages for constructing metal-organic frameworks (MOFs), especially the ligands with additional function such as (4-X-C6H4) (X: C≡CH, COOH, Br, SMe, NMe2) groups incorporated into the 4’-position. The type of MOF had potential applications in the area of catalysis, luminescence, gas uptake, magnetism and biochemical activities.15-36 In this regard, Constable et al. have reported Co(SCN)2 reacted with 4’-C6H5- and 4’-(4-C≡CH-C6H4)- 4,2’:6’,4-terpyridine to offer two kinds of cobalt frameworks, (4,4) and (6,3) nets, respectively.31 Wen and Ke et al. have reported

two

porous

cadmium(II)

frameworks

with

a

polytopic

4-(4-carboxyphenyl)-4,2´:6´,4´´-terpyridine ligand, which show selective adsorption of CO2 and display strong photoluminescence.32 Then following, this bridging coligands coordinated with Zn(Ⅱ),Co(Ⅱ), Mn(Ⅱ) resulting different kinds of the interpenetration,

polycatenane,

interdigitation,

polythread,

and

other

species.33-36However, coordination compounds with terpyridine ligands have rarely been investigated in the oxidation catalytic reactions.37 3



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Herein, we successfully prepared four coordination polymers Co(L1)Cl2 (1), Co3(L1)3Cl6

(2),

Cu9(L1)4.5(CN)9

(3),

[Cu3(L2)6(H2O)6]•4H2O

(4)

through

hydrothermal method. The dimensionalities of the entire architectures of the four compounds vary from 1D to 3D, and we found that the solvent and subtle temperature changes have a profound impact on the self-assembly of polymeric networks. We also successfully employed the four coordination polymers as highly efficient catalyst for the oxidation of benzylic hydrocarbons up to 99% conv.and 99% sele..

Experimental Section Materials and Methods. All of the chemicals and solvents were commercially available without further purification. L1 was synthesized by a modification of the literature methods.38 And L2 was readily obtained through the hydrolysis of L1. IR spectra were recorded with KBr pellets on a Nicolet 170S Fourier transform infrared spectrometer in 4000-400 cm-1 region. Powder X-ray diffraction data (PXRD) were collected on Bruker SMART APEX-CCD using Cu-Kα radiation (λ = 1.54060 Å). Thermal gravimetric analyses (TGA) were performed in a nitrogen atmosphere on a Q50TGA with a heating rate of 10 °C min−1. The syntheses of compounds 1-4 are shown in Scheme 1. Synthesis of Ligand L1. Ligand L1 was prepared by the procedure of Beves with a little modification.38 4-Acetylpyridine (4.84 g, 40.0 mmol) was added to a solution of 4-cyanobenzaldehyde (2.69 g, 20.5 mmol) in MeOH (100 cm3). KOH (2.70 g, 50 mmol) and aqueous NH3 (60 cm3, 25%) were added to the solution and the mixture 4


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was stirred at room temperature for 0.5 h. After refluxing for 12 h, the formed off-white solid was collected by filtration and washed with EtOH (3 × 15 cm3). Ligand L1 was isolated as white polycrystalline solid after recrystallization from CHCl3-MeOH. Yield: 47.0%. Melting point: >250 °C. Anal.Calcd for C22H14N4 (%): C, 79.02; H, 4.22; N, 16.76. Found: C, 78.03; H, 4.35; N, 16.52. FT-IR (KBr pellet, cm-1): 3037(w), 2228(m), 1595(s), 1560(m), 1543(m), 1510(m), 1429(w), 1396(m),819(s), 631(m), 620(w), 578(w); 1H NMR (d-DMSO, 600 MHz) δ(ppm): 8.10 (d, J = 8.2 Hz, 2H), 8.35(d, J = 8.2 Hz, 2H), 8.36(d, J = 6.0 Hz, 4H), 8.58(s, 2H), 8.79(d, J = 6.0 Hz, 4H). Synthesis of Ligand L2. A mixture of L1 (1.07g, 3.2mmol), KOH (10.0g, 178.6mmol) and H2O (200 mL) were added to a round bottom flask and stirred at 100 ºC until dissolved. After cooled to room temperature, concentrated hydrochloric acid was slowly dropwise added into the mixture under stirring until pH reached about 3. After filtration, the obtained white precipitate was washed with ethanol and then dried in the air at 60ºC. Yield: 97.0%. Melting point: >250 °C. Anal.Calcd for C22H15N3O2 (%): C, 74.78; H, 4.28; N, 11.89. Found: C, 75.05; H, 4.06; N, 11.67. FT-IR (KBr pellet, cm-1): 421 (s), 3071(w), 1707(m), 1631(s), 1598(s), 1508(m), 1395(m), 1120(m), 830(m), 773(m), 740(s), 615(s), 596(s), 530(s); 1H NMR (d-DMSO, 600 MHz) δ(ppm): 8.00 (d, J = 8.4 Hz, 2H), 8.27 (d, J = 8.4 Hz, 2H), 8.35 (s, 2H), 8.40 (d, J = 6.0 Hz, 4H), 8.79 (d, J = 6.0 Hz, 4H).

5



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[Insert Scheme 1] Synthesis of Co (L1)Cl2 (1). A mixture of CoCl2·6H2O (7.14 mg, 0.03 mmol), L1 (10.0 mg, 0.03 mmol) and acetonitrile (5 mL) were sealed in a 10 ml Teflon-lined autoclave and heated to 160 ºC for 3 days, followed by slowly cooling to room temperature. After filtering the solution, blue strip crystalline products 1 were obtained, washed with acetonitrile (2 mL) and dried in air. Yield: 20.0%. Anal.Calcd for C22H14Cl2CoN4 (%): C, 56.89; H, 3.02; N, 12.06. Found: C, 57.02; H, 3.10; N, 12.15. FT-IR (KBr pellet,cm-1): 2990(w), 2226(w), 2065(m), 1637(m), 1617(s), 1489(m), 1397(m), 1174(m), 1137(w), 1002(s), 788(s), 620(m), 530(w). Synthesis of Co3(L1)3Cl6 (2). Blue hexagonal plate crystals 2 were prepared with analogous procedure as 1, except that reaction temperature was decreased to 100 ºC. Yield: 13.1%. Anal.Calcd forC66H42Cl6Co3N12 (%): C, 56.89; H, 3.02; N, 12.06. Found: C, 57.12; H, 3.07; N, 12.11. FT-IR (KBr pellet, cm-1): 2990(w), 2227(m), 2065(m), 1637(m), 1617(s), 1488(m), 1396(m), 1174(m), 1137(w), 1002(s), 788(s), 622(m), 540(w). Synthesis of CuI9(L1)4.5(CN)9 (3). A mixture of Cu(NO3)2·3H2O (7.25 mg, 0.03mmol), L1 (10.0 mg, 0.03mmol) and acetonitrile (8 mL) were sealed in a 16 mL Teflon-lined autoclave and heated at 160 ºC for 3 days, followed by slowly cooling to room temperature. After filtering the solution, long strip orange crystals 3 were obtained. Yield: 24.2%. Anal.Calcd forC108H63Cu9N27 (%): C, 56.09; H, 2.73; N, 16.36. Found: C, 56.51; H, 3.07; N, 16.11. FT-IR (KBr pellet, cm-1): 2973(w), 6


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2225(w), 2126(m), 1599(s), 1541(w), 1394(m), 1061(w), 1011(w), 827(s), 672(m), 642(m), 544(m). Synthesis of [Cu3(L2)6(H2O)6]•4H2O (4). A mixture of Cu(CH3COO)2·H2O (6.0 mg, 0.03mmol), L2 (10.5 mg, 0.03mmol) and H2O (8mL) were sealed in a 16ml Teflon-lined autoclave and heated at 160 ºC for 3 days, then cooled to room temperature. After filtering the solution, blue strip crystals 4 were obtained. Yield: 10.2%. Anal.Calcd for C132H106Cu3N18O22 (%): C, 63.75; H, 4.30; N, 10.14. Found: C, 63.31; H, 4.37; N, 9.95. FT-IR (KBr pellet, cm-1): 3431(s), 1617(w), 1595(m), 1595(s), 1551(m), 1384(s), 1217(w), 1063(m), 847(w), 784(m), 696(m), 633(m), 512(m).

General Procedure for Catalyzed Oxidation of benzylic hydrocarbons. Benzylic hydrocarbons (0.1250 mmol), 70% tert-butyl hydroperoxide (TBHP) (0.3125 mmol) and catalyst (4 µmol) were placed into a Schlenk Tube, and then chlorobenzene (1 mL) was added to the mixture. Subsequently the reaction mixture was heated to 80ºC in a Wattecs Parallel Reactor and maintained 24 h under stirring. After the oxidation reaction, the mixture was cooled down to room temperature. Then the resulting mixture was analyzed by GC-MS and GC using naphthalene as external standard. Crystal structure determination. The X-ray single-crystal data for compounds was carried on a Bruker Smart CCD diffractometer with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å) at 293 K. The data sets were corrected by empirical absorption correction using spherical harmonics, implemented in the ω-scaling 7



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algorithm. The structures of all compounds were solved by direct methods and refined by full-matrix least-squares methods with SHELX-97. All non-hydrogen atoms were refined anisotropically. All the hydrogen atoms are placed in calculated positions. For 2, we used the SQUEEZE command in the refine process as the solvent molecules can’t be accurately determined owing to dispersibility of the electron cloud density. The crystallographic data are collected in Table 1. Important bond lengths and bond angles are listed in Table S1 in the ESI.†.

[Insert Table 1]

Results and Discussion Syntheses. The ligand L1 was synthesized according to the reaction cyanobenzaldehyde with two equivalents of 4-acetylpyridine under the basic condition. Then, L1 was hydrolyzed to the ligand L2 with carboxyl group under acidic conditions. The ligands are poorly soluble in solvent at room temperature so we adopted a solvothermal method which can promote the solubility of ligands. In this system, the self-assembly process is obviously affected by various factors such as reaction temperature, metal ions and coordinated disposition of the ligands. As we expected, the benzonitrile group of L1 is not coordinated in the assembly process, whereas the carboxyphenyl of L2 is connected with metal ions through oxygen atoms, which greatly affects the resulting structures and properties. 8


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Description of the structures Structure description of Co (L1)Cl2(1). Single crystal X-ray diffraction analysis reveals that compound 1 crystallizes in the monoclinic space group P21/n. In the asymmetric unit there are one cobalt ion, one L1 ligand and two bound Cl- anion. As shown by Figure 1a, Co2+ is surround by two nitrogen atoms from two L1 and two chloride anion to furnish a distorted CoN2Cl2 tetrahedral geometry. Significantly, each L1 is connected to two Co2+via the terminal N-donors of pyridyl groups leaving the nitrile group uncoordinated, thus L1 acts as a bidentate-bridging linker, leading to a one-deimensional 21 helical chain with the a pitch of 16.7Å and the distance of Co···Co along the chain being 12.727(1) Å (Figure 1b). Various weak interactions are also found in the packing structure, involving π⋯π interactions among pyridyl rings of L1 from adjacent helices in an offset face-to-face stacking fashion (centroid-to-centroid distances of 3.619 Å and 3.708 Å), weak interactions of the nitrile groups and pyridyl rings of L1 via face-to-face stacking interaction (distance: 3.589 Å) and C-H…N weak hydrogen bonding interaction (distance: 3.260 and 3.284 Å), as are shown in Figure 1c and 1d. [Insert Figure 1] [Insert Figure 2] Structure description of Co1.5(L1)1.5Cl3 (2). Compound 2 crystallizes in the trigonal space group P3221 with its asymmetric unit consisting of two 9



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crystallographically independent cobalt ions, one and a half ligand L2, and three Clanions, shown in Figure 2a. In this structure, the cobalt centers also adopts four coordinated tetragonal geometry defined by two Cl- anions and two pyridyl nitrogen atoms from L1 to form helical chains with the distance of Co···Co 12.540(1) Å (Figure 2c). For the reason that the procedure of 1 and 2 are almost the same expect the temperature, they seem to show the comparable chain-like structure. But in fact they are distinct from each other. Compound 2 shows more complicated helical structure. A 32 axis in 2 instead of 21 axis in 1 runs along oc direction(Figure 2c). In 1, two neighboring L1 arrange in the same orientations and positions, while the spatial directions of alternate L1 in 2 are different, which can be ascribed to two types of crystallographically independent cobalt ions and L2 in 2. Similar to 1, the π⋯π stacking interactions between the pyridyl rings or C≡N (centroid-to-centroid distance of 3.801 and 3.960 Å) in neighboring chains sustain the interdigitated structure (Figure 2b). [Insert Figure 3] Structure description of Cu9(L1)4.5(CN)9 (3). As is shown in Figure 3a, compound 3 crystallizes in the orthorhombic Pbcn space group with its asymmetric unit comprising nine CuI ions, four and a half L1 ligands and nine cyanide ions. The existence of cyanide ions can be proved by 2126 cm-1 of the bridged CN- stretching in IR, which is in agreement with the previously reported result.39 Despite the absence of CN- anions in the reactant system, they probably originate from the decomposition of 10


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solvent acetonitrile and/or L1 at high temperature, and simultaneously reduced Cu2+ to Cu+.40 Similarly, the XPS experiments were carried out for testing the charge of cooper in the compounds 3. Thus, Figure S2 show plots of the Cu2p3/2 (931.14eV) and Cu2p1/2 (950.97eV) photoelectron being in agreement with those previously reported and discussed in the literature for Cu+.41 In this structure, each copper ion is bridged by two C/N of CN- and one pyridyl nitrogen atoms of L1 to form distorted triangular coordination geometry. As a rigid “V” type connector, each L1 ligand combines with two CuI ions via two pyridyl groups, leaving the nitrile group uncoordinated. Also, CN- anion acts as a linear µ2- ligand bridging cuprous ions. As shown by Figure 3b and 3c, µ2-L1/CN- connectors and three-connected cuprous node construct two types of ring motif: tetranuclear and octanuclear cuprous rings. Tetranuclear cuprous ring is comprised of two L1, two CN- and four cuprous ions, and the distance of Cu···Cu is 4.857 Å along the CN- and 13.136 Å along L1. Meanwhile, two L1, six CN- and eight cuprous ions construct an elliptical octanuclear ring, whose longest Cu···Cu distance is 23.485 Å. In this way, the two ring motifs connect with each other to construct a 3D network with large hexagonal channels (see Figure S3).† Notably, the large size void in the layer structure provide the possibility for the ultimate generation of the entanglement. As shown in the Figure 3d, the structure is reinforced by a 4-fold interpenetration to a resultant stable close structures.

[Insert Figure 4] 11



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Structure description of [Cu3(L2)6(H2O)6]•4H2O (4).The reaction between L2 and Cu(CH3COO)2•H2O afforded blue strip crystals 4 that crystallize in the triclinic space group P-1. In the asymmetric unit, there are one and a half cooper ions and three L2. As shown in the Figure 4a, each Cu1 forms a distorted CuN2O3 tetragonal pyramid geometry with two nitrogen atoms and two oxygen atoms from four L2 ligands occupying the equatorial positions and one oxygen atom from a coordinated H2O filling the axial position; While the Cu2 center adopts a distorted octahedral geometry defined by two pyridyl nitrogen atoms and two carboxylate oxygen atoms from two non-equivalent L2 ligands, two oxygen atoms from water molecule occupying the axial position. It’s noted worthy that the axial position is occupied by water molecule via the weak coordination interaction for the Jahn-Tellar effect of Cu (with the Cu-O distance being 2.305 and 2.481 Å), which makes them potential active sites for further catalytic property. In this structure, each L2 ligand acts as a bridging linker to connect Cu(II) centers using one of the pyridine terminal nitrogen atoms and the carboxylate oxygen atom to form a grid-like infinite 1D chain with a minimum Cu…Cu distance of 14.288 Å (Figure 4a). Unlike compound 3, (a) the introduce of -COOH instead of -C≡N bring new bridging mode of this ligand; (b) without the acetonitrile in the reaction system, the oxidation state of Cu is +2 in 4. As depicted in Figure 4b and 4c, although the residual pyridyl rings and phenyl rings are not engaged in coordination, it bears the offset face-to-face π...π stacking interactions with their corresponding rings of 12


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adjacent chains with centroid-to-centroid distance of 3.537, 3.883 and 3.811 Å, which further aggregated 3D network. Thermal stability and Powder XRD. In order to investigate the thermal stability of compounds 1-4, the thermal gravimetric analyses (TGA) were carried out in the temperature range of 25-800 °C under nitrogen atmosphere (in Figure S4) (ESI).† Their main skeletons are stable till 300-500 °C and show excellent thermal stability. The collapse temperature is about 460°C for 1, 440 °C for 2, 360°C for 3, and 290°C for 4, respectively. Specially, for compound 4, there’s a weight loss before 79°C (observed 7.41 %, theoretical 7.85 %), which can be attributed to the release of lattice water molecules. Furthermore, the powder X-ray diffraction patterns of compounds 1-4 are illustrated in Figure S5 (ESI)† which confirm the purities of the bulky crystalline samples 1-4 between the simulated ones and as-synthesized products. Oxidation Catalytic test. With the aim to understand the catalytic property of these coordination polymers for developing a new oxidation system in organic chemistry, the oxidation of diphenylmethane to benzophenone was selected as a model reaction (Scheme 2). [Insert Scheme 2] [Insert Figure 5] The primary results suggest that, all four compounds can promote the catalytic 13



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oxidation of diphenylmethane, leading to benzophenone and diphenylmethanol with preferable selectivity of the carbonyl product. Optimization of the reaction conditions were carried out by selectively evaluating effects of different diphenylmethane-to-4 molar ratios, oxidant-to-4 molar ratios, and solvents (Supporting Information Table S2). As depicted in Table S2, on the basis of the oxidation of diphenylmethane, 2.5 equiv of TBHP and 4 µmol of catalyst in chlorobenzene for 24h are appropriate conditions for all catalytic reactions. Under the same conditions, we note that compounds 1, 2 and 3 showed moderate activities while 4 presented superior activity toward the oxidation reaction, giving a 94.5% conversion and 92.6% selectivity in chlorobenzene at 80°C for 24h (Figure 5). These results exhibit that compound 4 can facilitate the oxidation of diphenylmethane and serve as highly efficient and selective catalyst. And indeed, yield of the compound 4 outperforms many effective catalysts reported to date, i.e. nano-sized coordination cages [CuII(bped)2(H2O)2(SiF6)],10 [Cu4L4]4X (L= 1,3,5-tris(1-benzylbenzimidazol-2-yl)benzene, X= ClO4, OTs, OTf),11 NHPI/Cu@PILC12,

[Co3(BTC)2(HCOO)4(DMF)]•H2O13

and

even

noble

Pd@N-doped carbon14, etc. Furthermore, control catalytic experiments of the catalytic oxidation of diphenylmethane were performed on L2 and Cu(CH3COO)2·H2O under the same reaction conditions, respectively. The conversion was 8.71% for the former and 75.8% for the latter. Based on the above-mentioned facts, we conclude that the introduce of L2 into the catalytic system changes the coordination environment of the Cu ions and 14


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the cooperation between CuII centers and organic ligands in catalyst of 4 probably produces synergistic effect; and thus enhances the oxidative capacity of copper centers in the catalytic process. [Insert Table 2] Following the success of diphenylmethane oxidation and evaluating the scope and limitations of the current procedure, oxidation reactions with an array of benzylic hydrocarbons were examined using compound 4. A compilation of results for the oxidation of various benzyl-alkanes with large molecules, along with the corresponding ketones is presented in Table 2. It is noteworthy that, without any further optimization, the oxidation of fluorene, the derivatives of the fluorene and xanthene proceeded smoothly with a high catalytic activity (>99% conversion, >99% selectivity for ketones). These preliminary results exhibit that these coordination polymers based on substituted terpyridine, especially compound 4, can facilitate the oxidation of benzyl-alkanes and serve as highly efficient and selective catalysts.

Conclusions In this paper, four coordination compounds were successfully synthesized by two types of substituted terpyridine ligands L1 and L2 with transition metal ions of Co and Cu ions under solvothermal conditions. These compounds possess different architectures such as 1D helix or grid-like chain and 3D interpenetration network, whichdemonstrates that a change of temperature and metal ions have played a crucial 15



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role in the self-assembly process. Meanwhile, all the compounds show good thermal stabilities. In addition, the compound 4 exhibits excellent oxidation catalytic properties towards benzyl-alkanes. The good catalytic properties along with the high thermal stability make these compounds potential applicable under more rigorous reactions specially as the heterogeneous catalysts.

Acknowledge We are grateful to the National Natural Science Foundation of China (Project No. 21271025, 11474204; 21401094), Beijing Higher Education Young Elite Teacher Project (Project No. 1209 and 1628) and Beijing Municipal Natural Science Foundation (Project No. 2143039).

Associated content

Supporting Information Available Crystallographic data in CIF format, PXRD for simulated and as-synthesized samples, TG curves for all compounds, XPS for compound 3 and selective oxidation of diphenylmethane by 4 using TBHP oxidant. This material is available free of charge via the Internet at http://pubs.acs.org.

References (1) Brodsky, B. H.; Du Bois, J.J. Am. Chem. Soc. 2005, 127, 15391-15393. (2) Lee, S. M.; Fuchs, P. L. J. Am. Chem. Soc. 2002, 124,13978-13979. 16


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Growth.Des.2012, 12, 4083-4089. (33) Gai, Y.-L.; Jiang, F.-L.; Chen,-L.; Bu, Y.; Wu, M.-Y.; Zhou, K.; Pan, J.; Hong, M.-C. Dalton Trans. 2013, 42, 9954-9965. (34) Yang, J.; Liu, J.; Wang, X.; Chi, X.; Zhang, J.; Zhang, H.; Xiao, D.; Luo, Q. CrystEngComm2013, 15, 10435-10439. (35) Yang, P.; Wang, M.-S.; Shen, J.-J.; Li, M.-X.; Wang, Z.-X.; Shao, M.; He, X. Dalton Trans. 2014, 43, 1460-1470. (36) Xu, B.; Xie, J.; Hu, H.-M.; Yang, X.-L.; Dong, F.-X.; Yang, M.-L.; Xue, G.-L. Cryst.Growth.Des.2014, 14, 1629-1641. (37) Ma, Z.; Wei, L. J.; Alegria, E. C. B. A.; Martins, L. M. D. S.; Guedes da Silva, M. F.; Pombeiro, A. J. L. Dalton Trans. 2014, 43, 4048-4058. (38) Beves, J. E.; Dunphy, E. L.; Constable,E. C.; Housecroft, C. E.; Kepert, C. J.; Neuburger, M.; Price, D. J.; Schaffner, S. Dalton Trans.2008, 386-396. (39) Lang, J.-P.; Xu, Q.-F.; Chen, Z.-N.; Abrahams. B. F. J. Am. Chem. Soc. 2003, 125, 12682-12683. (40) Feng, S. G.; Templeton, J. L.J. Am. Chem. Soc.1989,111, 6477-6478. (41) Espinós, J. P.; Morales, J.; Barranco, A.; Caballero, A.; Holgado, J. P.; González-Elipe, A. R. J. Phys. Chem. B. 2002, 106, 6921-6929.

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Scheme 1. Synthesis of compounds 1− −4

Scheme 2. The oxidation of diphenylmethane

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Table 1.Crystallographic data for compounds 1-4. Compound

1

2

3

4

formula

C22H14Cl2CoN4

C66H42Cl6Co3N12

C108H63Cu9N27

C132H106Cu3N18O22

Formula mass

464.20

1392.61

2310.71

2486.97

Crystal system

Monoclinic

Trigonal

Orthorhombic

Triclinic

Space group

P21/n

P3221

Pbcn

P-1

a/Å

10.150(3)

13.6428(12)

21.238(2)

10.4718(13)

b/Å

16.699(5)

13.6428(12)

14.4083(16)

13.5124(16)

c/Å

12.184(4)

31.625(3)

64.699(7)

21.992(3)

α/°

90

90

90

75.334(2)

β/°

94.644(6)

90

90

86.167(2)

γ/°

90

120

90

71.784(2)

V/Å3

2058.3(11)

5097.6(8)

19798(4)

2859.3(6)

T/K

296(2)

293(2)

296(2)

296(2)

Z

4

3

8

1

µ/mm−1

1.109

1.007

1.957

0.639

F(000)

940

2115

9288

1305

Reflection s collected / unique

10256/3623

25548/5974

95776/17479

14326/9903

Rint

0.1141

0.1221

0.1192

0.0373

R1(I>2δ(I))

0.0448

0.0651

0.0683

0.0843

wR(F2) (I>2δ(I))

0.1116

0.1500

0.1761

0.2252

R1(all data)

0.0746

0.1075

0.1395

0.1473

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wR(F2) (all data)

0.1527

0.1695

0.2099

0.3263

S

1.054

0.927

1.029

1.123

CCDC .No

1033132

1033133

1033134

1033135

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Table 2 The oxidation of various benzyl hydrocarbons catalyzed by 4 Conv.(%)

Sele. (%)b

1

94.5

92.6

2

>99

>99

3

>99

>99

4

96.2

95.8

5

97.1

96.2

Entry

Substrates

Products

[a] Reaction conditions: benzylic hydrocarbons (0.125mmol), compound 4 (4 µmol), TBHP (0.3125mmol), chlorobenzene (1 mL), 80 ºC, 24h. [b] Selectivity to ketones. The by-products are corresponding alcohols.

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FIGURE CAPTIONS

Figure 1. a) The coordination mode of the L1ligand and the coordination geometries of the CoIIcations in compound 1 (Symmetry code: A 3/2-x, y-1/2, 1/2-z). b) Scheme of the one-dimensional helical chain of 1 with 21axis (in yellow). c) The π-π stacking interactions between the pyridyl rings of neighboring ligands. d) the weak interactions of π-π interactions and hydrogen bonding interactions between C≡N and the pyridyl or benzene rings in 1. Color scheme: Co, light blue; N, dark blue; Cl, green; C, black. H atoms are omitted for clarity.

Figure 2. a) The coordination mode of the L1 ligand and the coordination geometries of the CoII cations in compound 2. b) The π-π stacking interactions between the pyridyl rings and C≡N of neighboring ligands. c) The one-dimensional helix topology in 2 runs along the oc axis.Color scheme: Co, light blue; N, blue; Cl, green; C, black. H atoms are omitted for clarity.

Figure 3. a) The scheme of assymetric unit in 3 showing the coordination mode of the L1 ligand and the coordination geometries of the CuIcations in compound 3. b) The tetranuclear cuprous ring. c) The octanuclear cuprous ring. d) A perspective view of the quadruple interdigitated architecture in 3 along the oc axis(The connectivity of neighboring Cu is drawn by a line and the ligands are omitted). Color scheme: Cu, light blue; C, black; H atoms was omitted for clarity. The µ2-CN- bonds are highlighted in pink. 27



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Figure 4. a) The grid-like chain of 4 showing its coordination mode of L2 ligand and the coordination geometries of two types of CuIIcations. b) π-π stacking interactions schematic along the oc axis. c) View of the 1D +1D→3D architecture of 4.(Color scheme: Cu, light blue; N, blue; O, red; C, black; H atoms are omitted for clarity.)

Figure 5. Conversion and selectivity of diphenylmethane to benzophenone with compounds 1-4. Reaction conditions: diphenylmethane (0.125 mmol), as-synthesized compound (4 µmol), TBHP (0.3125 mmol), chlorobenzene (1 mL), 80 ºC, 24h. [b]Selectivity to ketones. The by-product was benzhydrol.

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Figure 1.

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Figure 2.

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Figure 3.

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Figure 4.

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Figure 5.

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For Table of Contents Use Only

Four novel coordination compounds based on the 4,2’:6’,4-terpyridine have been rationally designed and synthesized. They show exceptional catalytic activity for the oxidation of benzylic C-H bonds. Among them, compound 4 fomulated as [Cu3(L2)6(H2O)6]•4H2O show the best catalytic properties for the oxidation of various benzylic hydrocarbons(conv. up to 98.5% , sele. up to 100%).

Coordination Polymers based on Substituted Terpyridine Ligands: Synthesis, Structural Diversity, and Highly Efficient and Selective Catalytic Oxidation of Benzylic C-H Bonds Yaru Xi†, Wei Wei‡, Yanqing Xu†*, Xianqiang Huang†ǁ*,Fanzhou Zhang†, Changwen Hu*

†

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Coordination Polymers Based on Substituted Terpyridine Ligands

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