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Dec 18, 2015 - Fei-Fan Chang , Lei Zhang , Pei-Chen Zhao , and Wei Huang ... Dan Li , Hongbo Tong , Chenglin Wu , Wenyuan Tang , Ping Zhang , Lei Wang...
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Two Types of Anion-Induced Reconstruction of Schiff-Base Macrocyclic Zinc Complexes: Ring-Contraction and Self-Assembly of a Molecular Box Kun Zhang, Lei Zhang, Gen-Feng Feng, Yong Hu, Fei-Fan Chang, and Wei Huang* State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, P. R. China S Supporting Information *

ABSTRACT: Two 46-membered [2 + 2] Schiff-base macrocyclic dinuclear Zn(II) complexes (1a and 1b) were investigated deeply by the postmodification strategy, and two types of supramolecular processes (ring-contraction and self-assembly) have been achieved after the addition of specific anions as stimulus for the equilibrium of Schiff-base macrocyclic complexes. Namely, in the presence of linear three-atom SCN−, 1a was degraded into two 23-membered [1 + 1] Schiffbase macrocyclic complexes simultaneously (mononuclear Zn(II) complex 2 and dinuclear Zn(II) complex 3). In contrast, 1b was only transformed into the macrocyclic mononuclear complex 5. More interestingly, in the case of pseudolinear fiveatom N(CN)2−, supramolecular self-assembly took place instead of the above-mentioned ring-contraction. Finally, 1a was assembled into a unique molecular box 4 with two 46-membered [2 + 2] Schiff-base macrocyclic heteronuclear Zn4Na4 substrates and double μ2-N(CN)2− bridges, while no similar assembly process was observed for 1b. The geometry of anions and pH values slightly adjusted by the pendant arms on the macrocyclic skeletons are believed to be the critical factors for the different supramolecular processes originating from the dynamic covalent chemistry of Schiff-base imine bonds.

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INTRODUCTION Anions are ubiquitous species throughout chemistry research.1 Large numbers of anions with different sizes, charges, and geometries2 from simple spherical halide ions to complex DNA double helical anions have been found and carefully studied in the field of catalysis,3 biology,4 and environment,5 etc. Because of limited examples in early times, chemists could not evaluate the role of anions at a more profound level in some supramolecular processes involving recognition and assembly.6 The anions were merely thought of as counterions at that time to fill the coordination spheres of metal ions and equilibrate the charges of complexes. After some thought-provoking supramolecular aggregations acquired only by the specific anions such as cavitand structures with trapped anions,7 chemists start to recognize that the anions could also play important roles in the supramolecular processes.8,16 In some cases, the selection of different anions can efficiently regulate the resultant products that originated from the same precursors.9 As a challenging area of supramolecular chemistry, anionassisted low-dimensional supramolecular assembly and rearrangement have been used as efficient methods to investigate many complicated supramolecular architectures, such as circular helicates,7,10 molecular cages,11 pseudorotaxanes,12 layer structures,13 interlocks,14 and so on. Herein, we describe the anion-induced reconstruction of two 46-membered [2 + 2] flexible macrocyclic dinuclear Zn(II) complexes (1a and 1b) © XXXX American Chemical Society

containing different pendant arms and reversible Schiff-base imine bonds in ethanol. Induced by the specific anion (SCN− or N(CN)2−), ring-contraction and supramolecular selfassembly can be achieved for 1a and 1b (Scheme 1). Namely, in the presence of SCN− anion, 1a degrades into two 23membered [1 + 1] Schiff-base macrocyclic complexes simultaneously (mononuclear Zn(II) complex 2 and dinuclear Zn(II) complex 3). In contrast, 1b only transforms into the macrocyclic mononuclear complex 5, which is similar to the molecular structure of 2. As for the N(CN)2− anion, supramolecular self-assembly takes place instead of ringcontraction by forming a novel double [2 + 2] macrocyclic heteronuclear Zn4Na4 molecular box 4 with double μ2N(CN)2− bridges. In this structure, a 46-membered [2 + 2] macrocyclic skeleton is retained, but its coordination mode and geometry, nuclearity, and charge are totally different from those in 1a.

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RESULTS AND DISCUSSION Syntheses of 23-Membered [1 + 1] Pendant-Armed Schiff-Base Macrocyclic Complexes (2, 3, and 5) and the Molecular Box (4). As we have reported before, two SchiffReceived: June 27, 2015

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DOI: 10.1021/acs.inorgchem.5b01451 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

combinatorial library, the targeted main products could be selectively obtained. Our experimental results demonstrate that the SCN− anion is an effective driving force to destroy the equilibriums of two [2 + 2] Schiff-base macrocyclic complexes and establish new equilibriums of [1 + 1] macrocyclic complexes as the main products. The presence of −CH2CH2C6H4OH and −CH2CH2C6H5 pendant arms in 1a and 1b is suggested to be another important factor for forming ring-contraction products with different nuclearities. As we have reported before,15 the pH value of 1b is much lower than that of 1a because 1b has two additional phenolic hydroxyl groups in each pendant arm of the macrocyclic ligand, which cannot allow for the formation of a μ2-OH bridge between two Zn(II) centers. Therefore, no analogous dinuclear Zn(II) complex corresponding to 3 is formed in the case of 1b. In contrast, a pseudolinear N(CN)2− anion has also been used for ring-contraction of 1a and 1b, but it was proven to be ineffective. However, this anion could serve as a bridging unit and assemble two molecules of [2 + 2] macrocyclic complex 1a into an interesting molecular box 4 via double μ2-N(CN)2− bridges. It is noted that this self-assembly process is highly efficient with quick and complete conversion in a high yield of 91% even at room temperature. After careful consideration, we have recognized that this successful supramolecular selfassembly instead of the above-mentioned ring-contraction is the results of cooperation of at least several factors, i.e., size, charge, and geometry of anion and cation, coordination status of macrocyclic ligand, and functional pendant arm. Two phenolic protons in the macrocyclic skeleton in 1a are first removed after the addition of NaN(CN)2, which could allow for some other cations with proper charge and size (Na(I) in this case) to enter the macrocyclic skeleton since there are still several uncoordinated N and O donors. As a result, two Na(I) and two Zn(II) cations form a tetranuclear cluster linked by one common μ4-OH bridge, formulated as {Zn2(μ4-OH)Na2}5+. Herein, the formed heterometal cluster core could provide additional chelating sites to act as a new macroyclic substrate for further assembly. In this case, the use of a pseudolinear N(CN)2− anion, which is much longer than SCN−, could overcome the steric hindrance of adjacent tetranuclear macrocyclic units and make possible the building of a double μ2-N(CN)2− bridged molecular box 4, where one weak coordinated and one free NO3− anion in 1a have been replaced according to the electroneutrality principle for the whole molecule. As we have mentioned before, the discrepancy of pH values originating from −CH2CH2C6H4OH and −CH2CH2C6H5 pendant arms in 1a and 1b plays important roles in the SCN− participated ring-contraction process, and similar phenomena have been observed for the construction of the molecular box. In fact, a parallel experiment by using 1b as the starting material to prepare a similar molecular box was unsuccessful. We think the −CH2CH2C6H5 pendant arm in 1a could ensure a favorable pH environment for stabilizing the OH− anion, which is critical for the formation of a μ4-OH bridged tetranuclear cluster core. Other two alkali metal (Li(I) and K(I)) salts and the N3− anion were also used to study the aforementioned ring-contraction and self-assembly processes started from 1a and 1b. Control experiments reveal that the ring-contraction reactions would not be affected by the type of alkali metal ions and the self-assembly process for the molecular box could only be carried out in the presence of Na(I) ion. In

Scheme 1. Synthetic Procedure of Macrocyclic Zn(II) Complexes 2−5a

a

(i) NaSCN/C2H5OH, room temperature, 24 h; (ii) NaN(CN)2/ C2H5OH, room temperature, 24 h.

base macrocyclic dinuclear Zn(II) complexes (1a and 1b) were prepared by the cyclic condensation reactions via a Zn(II) ion template between two pendant-armed dialdehyde precursors (H2hpdd and H2pdd) and 1,2-bis(2-aminoethoxy)ethane.15 Structural analyses reveal that they have the same nitrate counterions, but different coordination fashions (free and/or μ2-bridging). Considering that the nitrate anions in 1a and 1b could be further replaced by other anions with stronger coordination ability and the coordination sites of macrocyclic ligands are unsaturated for metal-ion complexation at the same time, the reconstruction of Schiff-base macrocyclic complexes and further self-assembly are regarded to be possible. In addition, the presence of −CH 2 CH 2 C 6 H 4 OH and −CH2CH2C6H5 pendant arms might result in different macrocyclic products. That is the reason why Schiff-base macrocyclic dinuclear Zn(II) complexes 1a and 1b, bearing [2 + 2] macrocyclic ligands with multiple uncoordinated N and O donors and NO3− counterions, are selected as the starting materials to treat with SCN−/N(CN)2− and Na(I) ions for comparison in this study. It is found that the use of linear SCN− anion with strong coordination ability could drive both [2 + 2] macrocyclic Zn(II) complexes 1a and 1b into related [1 + 1] macrocyclic Zn(II) complexes. In our experiments, complexes 2 and 3 were simultaneously yielded from 1a, while only one ring-contraction product 5 could be obtained from 1b by contrast. Commonly, there are equilibriums between the precursors (dialdehyde and diamine) and their various condensation products in solution via reversible formation and cleavage of Schiff-base imine bonds.16 By using some chemical factors to drive the dynamic B

DOI: 10.1021/acs.inorgchem.5b01451 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry Table 1. Crystal Data and Structural Refinements for Compounds 2, 3, 4, and 5·(C2H5OH·CH3OH)0.5 complex

2

3

4

5·(C2H5OH·CH3OH)0.5

empirical formula formula weight temperature/K wavelength/Å crystal size (mm) crystal system space group a/Å b/Å c/Å α/deg β/deg γ/deg V/Å3 Z/Dcalcd (g/cm3) F(000) μ/mm−1 hmin/hmax kmin/kmax lmin/lmax data/parameters R1, wR2 [I > 2σ(I)]a

C32H33Cl2N5O4S2Zn 752.06 291(2) 0.71073 0.12 × 0.11 × 0.09 triclinic P1̅ 12.218(2) 12.253(2) 13.327(2) 111.035(3) 100.847(3) 103.128(3) 1731.9(5) 2/1.442 776 1.027 −15/14 −15/15 −10/17 7933/415 R1 = 0.0542 wR2 = 0.1478 R1 = 0.0721 wR2 = 0.1609 1.04 1.48/−0.91

C32H33Cl2N5O5S2Zn2 833.45 291(2) 0.71073 0.11 × 0.10 × 0.08 monoclinic P21/c 16.175(1) 14.009(1) 16.746(1) 90 111.370(1) 90 3533.6(5) 4/1.567 1704 1.674 −19/19 −14/16 −19/19 6191/433 R1 = 0.0530 wR2 = 0.1499 R1 = 0.0722 wR2 = 0.1602 1.02 0.87/−0.80

C124H128Cl8N18Na4O18Zn4 2795.48 291(2) 0.71073 0.12 × 0.12 × 0.10 monoclinic P21/c 11.754(2) 28.268(4) 22.695(3) 90 103.714(3) 90 7325.8(18) 2/1.267 2884 0.867 −13/13 −29/33 −26/24 12862/794 R1 = 0.0883 wR2 = 0.2354 R1 = 0.1353 wR2 = 0.2546 1.13 2.32/−0.95

C67H76Cl4N10O12S4Zn2 1614.16 291(2) 0.71073 0.12 × 0.11 × 0.10 monoclinic P21/c 12.347(1) 27.799(2) 23.079(2) 90 102.698(2) 90 7727.7(11) 4/1.388 3344 0.930 −15/15 −36/26 −26/29 17607/893 R1 = 0.0702 wR2 = 0.1751 R1 = 0.1432 wR2 = 0.2105 1.03 0.79/−0.41

R1, wR2 (all data)a S max/min △ρ/e Å−3 a

R1 = ∑||Fo| − |Fc||/∑|Fo|, wR2 = [∑[w(Fo2 − Fc2)2]/∑w(Fo2)2]1/2.

X-ray single-crystal diffraction analyses (Table 1) of four macrocyclic Zn(II) complexes 2−5 (Figures 1 and 2) reveal

addition, neither ring-contraction nor self-assembly processes could occur in the case of the linear N3− anion. Spectral Characterizations and Crystal Structures of Macrocyclic Zn(II) Complexes 2−5. UV−vis spectra of three [1 + 1] macrocyclic zinc complexes (2, 3, and 5) show a common absorption band centered at 372−373 nm (Figure S1), which could be assigned as the characteristic π−π* transition of the azomethine chromophore in the macrocyclic ligands. This absorption band is found to be consistent with that of [2 + 2] macrocyclic complexes 1a and 1b. However, molecular box 4 exhibits a hypsochromic shift of 5 nm compared with that of 1a at 372 nm, which is ascribed to the alteration of electron density of four azomethine chromophores in the macrocyclic backbone after Na(I)-ion complexation. Accordingly, 1H NMR spectral comparison reveals an upfield shift of approximately 0.06 ppm from 1a to 4 in CD3OD, also indicative of the variation of chemical environment for four Schiff-base protons after forming the heterotetranuclear Zn2Na2 subunits in 4. In the FT-IR spectra of complexes 2−5, a series of strong peaks can be found at 1630−1636 cm−1 (Figures S2− S5), indicating the presence of imine bonds in their molecular structures. At the same time, a strong absorption peak of SCN− is observed at 2094−2096 cm−1 in 2, 3, and 5. In contrast, several strong absorption peaks are observed in the range of 2127−2287 cm−1 in 4, corresponding to the characteristic stretching vibrations of N(CN)2− anion. These FT-IR peaks suggest the successful participancy of SCN− and N(CN)2− anions in the anion-induced postmodification of [2 + 2] Schiffbase macrocyclic zinc complexes 1a and 1b, which could be further evidenced by the following X-ray single-crystal structures.

Figure 1. ORTEP drawings of structures of [1 + 1] macrocyclic Zn(II) complexes with the atom-numbering scheme: (a) 2, (b) 3, and (c) 5. Displacement ellipsoids are drawn at the 30% probability level, and the hydroxyl protons are shown as small spheres of arbitrary radii.

that the NO3− counterions have been replaced by SCN− and N(CN)2− as expected, and they have completely different structural features compared with 1a and 1b. Three 23membered [1 + 1] Schiff-base macrocyclic Zn(II) complexes (2, 3, and 5) do not have a folded configuration because of the smaller size of macrocyclic ligands (H2Lc and H2Ld). In two macrocyclic mononuclear Zn(II) complexes 2 and 5 with different pendant arms, the basal coordination planes of two four-coordinate tetrahedral Zn(II) ions are both composed of one phenolic oxygen atom, one imine nitrogen atom, and two nitrogen atoms of SCN − counterions. Two extended dialdehyde components also have the same “tripodal” configuration, and the dihedral angles between two salicylaldehyde rings are 41.7(2)° and 38.8(2)° in 2 and 5, respectively. It is worth mentioning that half of the Schiff-base CN units are C

DOI: 10.1021/acs.inorgchem.5b01451 Inorg. Chem. XXXX, XXX, XXX−XXX

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Two phenolic oxygen atoms, two imine nitrogen atoms, and one oxygen atom of the μ4-OH group make up the coordination sphere of every Zn(II) ion, while two phenolic oxygen atoms, one tertiary nitrogen atom, one oxygen atom of the μ4-OH group, and one terminal nitrogen atom of the N(CN)2− bridge constitute the coordination sphere of every Na(I) ion. In comparison with the structure of starting material 1a, it is found that all the phenolic protons of the macrocyclic ligand in molecular box 4 have been removed and the two tertiary nitrogen atoms (N3 and N6) take part in the Na(I)-ion complexation. At the same time, the separation between two tertiary nitrogen atoms has been extended from 6.096(6) Å in 1a to 12.977(6) Å in 4. In general, the molecular boxes can be assembled by means of weak forces like coordination and hydrogen bonding interactions, where the substrates are often the chemically stable fragments such as macrocyclic compounds18 and heteroaromatic derivatives.19 However, self-assembly of molecular boxes based upon Schiff-base macrocycles is very challenging because of reversible formation and cleavage of Schiff-base imine bonds. In this work, the formation of different anion-induced ring-contraction and self-assembly products (2− 5) is believed to originate from two main factors, namely, anions and pendant arms of the starting materials (Scheme 2). Figure 2. (a) ORTEP drawing of molecular box 4 with the atomnumbering scheme in the absence of a macrocyclic skeleton. Displacement ellipsoids are drawn at the 30% probability level. (b) Perspective view of the octanuclear molecular box 4. (c) Schematic illustration for the change of binding modes in macrocyclic components during the self-assembly.

Scheme 2. Schematic Illustration for the Anion-Induced Ring-Contraction and Self-Assembly Influenced by the Geometry of SCN− and N(CN)2− Anions as Well as the Pendant Arms of 1a and 1b

not coordinated with the metal ions and they are stabilized by strong intramolecular O−H···N hydrogen bonds instead (Table S2). In addition, the tertiary nitrogen atoms are not involved in any coordinative bonds, and both of the phenolic protons are retained, which can be deduced from the electroneutrality principle for the whole molecule. In comparison with macrocyclic mononuclear complex 2, the molecular structure of dinuclear Zn(II) complex 3 is significantly different, although it has the same 23-membered [1 + 1] Schiff-base macrocyclic ligand (H2Ld). Two Schiff-base CN units in 3 are both used to coordinate with the two central Zn(II) ions. The basal coordination plane of each fourcoordinate tetrahedral Zn(II) ion is composed of one phenolic oxygen atom, one imine nitrogen atom, one nitrogen atom of the SCN− counterion, and one oxygen atom of the bridging μ2OH unit. Here, the dihedral angle between two salicylaldehyde rings is much larger at 52.9(2)° compared with those in 2 and 5. Moreover, half of the phenolic protons are removed to balance the charge, and the tertiary nitrogen atom is still not used for metal-ion complexation. Structural analysis of complex 4 indicates that it is a unique octanuclear molecular box consisting of two identical 46membered [2 + 2] macrocyclic subunits and two pseudolinear μ2-N(CN)2− bridges. It is noted that four Na(I) cations have been further coordinated with two 46-membered [2 + 2] Schiffbase macrocyclic ligands (two for each). As a result, two new heterotetranuclear Zn2Na2 clusters have been formed for each [2 + 2] macrocyclic subunits, where four five-coordinated Zn(II) and Na(I) cations are linked by one common μ4-OH bridge. In each macrocyclic subunit, the coordination geometry for Zn(II) and Na(I) ions is distorted trigonal bipyramidal (τ = 0.898, 0.887 for Zn1, Zn2 and 0.942, 0.890 for Na1, Na2).17

The use of a longer five-atom N(CN)2− anion and more suitable −CH2CH2C6H5 pendant arm in 1a is crucial for selfassembling molecular box 4. On the one hand, the N(CN)2− anion reduces the spatial crowding of two neighboring macrocyclic subunits. On the other hand, the −CH2CH2C6H5 pendant arm provides the suitable alkaline for full deprotonation of macrocyclic ligands, allowing for further Na(I)-ion complexation and the formation of the molecular box. In contrast, the shorter three-atom SCN− anion could not serve as an analogous bridging ligand to self-assemble into the corresponding molecular box because of the aforementioned large steric hindrance. Instead, the SCN− anion could promote the equilibrium of reversible formation and cleavage of Schiffbase imine bonds shifting from [2 + 2] to [1 + 1] macrocyclic complexes. As a result, [1 + 1] ring-contraction Schiff-base macrocyclic complexes 2, 3, and 5 have been yielded as the main products, where different pendant arms lead to the formation of mononuclear and dinuclear macrocyclic complexes. D

DOI: 10.1021/acs.inorgchem.5b01451 Inorg. Chem. XXXX, XXX, XXX−XXX

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nm. Yellow green crystals of molecular box 4 were obtained by slow evaporation of a mixture of ethanol/acetonitrile solution (v/v = 6:1) in air at room temperature for 2 weeks. Synthesis of 5. NaSCN (0.033 g, 0.41 mmol) was dissolved in ethanol (10 mL) and added into a solution of 1b (0.143 g, 0.10 mmol) in ethanol (40 mL). The mixture was stirred for 24 h at room temperature and filtered. The filtrate was concentrated to give complex 5 in a yield of 0.129 g (84%). 1H NMR (300 MHz, CD3OD): δ 8.39 (d, J = 4.5 Hz, 2H), 7.32 (ddd, J = 16.5, 9.6, 2.5 Hz, 4H), 6.95 (dd, J = 8.4, 3.8 Hz, 2H), 6.75−6.56 (m, 2H), 3.84 (dd, J = 7.9, 3.9 Hz, 12H), 3.77−3.66 (m, 4H), 2.02 (t, J = 6.4 Hz, 2H), 0.95−0.83 (m, 2H). Anal. Calcd for C32H35Cl2N5O5S2Zn: C, 49.91; H, 4.58; N, 9.09%. Found: C, 49.85; H, 4.55; N, 9.04%. Main FT-IR absorptions (KBr pellets, cm−1): 2868, 2086 (SCN), 1635 (s, CHN), 1455, 1216, 1154, 695. UV−vis (methanol, 100 μM): λmax = 378 nm. Yellow green single crystals of complex 5·(C2H5OH·CH3OH)0.5 were grown from a mixture of ethanol/acetonitrile (v/v = 8:1) by slow evaporation in air at room temperature for 3 weeks.

CONCLUSION In summary, we have demonstrated that the postmodification strategy is achieved for two 46-membered [2 + 2] Schiff-base macrocyclic dinuclear Zn(II) complexes (1a and 1b), where two types of supramolecular processes (ring-contraction and self-assembly) could take place via the replacement of NO3− by linear three-atom SCN− and pseudolinear five-atom N(CN)2− anions with strong coordination ability. As a result, three 23membered [1 + 1] Schiff-base macrocyclic Zn(II) complexes (2, 3, 5) and a molecular box 4 with two 46-membered [2 + 2] Schiff-base macrocyclic heteronuclear Zn4Na4 substrates have been obtained and structurally characterized. Different geometry of anions and pH values slightly adjusted by the pendant arms of starting materials are suggested to play important roles in the ring-contraction and self-assembly processes stemming from the dynamic covalent chemistry of Schiff-base imine bonds.20

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ASSOCIATED CONTENT

S Supporting Information *

EXPERIMENTAL SECTION

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.5b01451. Tables of selected bond distances and angles, hydrogen bonding parameters, UV−vis, FT-IR, 1H NMR spectra (PDF) X-ray crystallographic data (CCDC nos. 1405905− 1405908) (CIF)

Materials and Methods. Unless otherwise specified, solvents of analytical grade were purchased directly from commercial sources and used without any further purification. Schiff-base macrocyclic zinc complexes (1a and 1b) were synthesized following our previously reported procedure.15 1 H NMR spectroscopic measurements were performed on a Bruker DPX 300 MHz spectrometer in CD3OD, using TMS (SiMe4) as an internal reference at room temperature. Elemental analyses were measured with a PerkinElmer 1400C analyzer. Infrared spectra (4000−400 cm−1) were collected on a Nicolet FT-IR 170X spectrophotometer at 25 °C using KBr plates. UV−vis spectra were recorded with a Shimadzu UV-3150 double-beam spectrophotometer using a quartz glass cell with a path length of 10 mm. Syntheses of 2 and 3. NaSCN (0.033 g, 0.41 mmol) was dissolved in ethanol (10 mL) and added into a solution of 1a (0.139 g, 0.10 mmol) in ethanol (40 mL). The mixture was stirred for 24 h at room temperature and filtered. The filtrate was concentrated to give a mixture of 2 and 3. The separation of 2 and 3 was achieved by the gradual crystallization of crystals owing to their different solubility. By slow evaporation in air at room temperature, single crystals of 2 were first grown from a mixture of ethanol/acetonitrile (v/v = 8:1) for 1 week. Single crystals of 2 were collected in a yield of 0.069 g (46%), and the filtrate was evaporated for another 2 weeks to give single crystals of 3 in a yield of 0.027 g (33%). Complex 2, 1H NMR (300 MHz, CD3OD): δ 8.40 (s, 2H), 7.42−7.11 (m, 9H), 4.23−3.99 (m, 4H), 3.87 (t, J = 16.3 Hz, 8H), 3.69 (dd, J = 16.6, 6.2 Hz, 4H), 2.03 (d, J = 6.6 Hz, 2H), 0.95−0.86 (m, 2H). Anal. Calcd for C32H33Cl2N5O4S2Zn: C, 51.10; H, 4.42; N, 9.31%. Found: C, 51.02; H, 4.67; N, 9.23%. Main FT-IR absorptions (KBr pellets, cm−1): 2908, 2094, 1635, 1549, 1458, 1155, 698. UV−vis (methanol, 100 μM): λmax = 372 nm. Complex 3, 1H NMR (300 MHz, CD3OD): δ 8.40 (s, 2H), 7.41−7.12 (m, 9H), 4.21−3.98 (m, 2H), 3.98−3.77 (m, 10H), 3.70 (dd, J = 14.0, 7.8 Hz, 4H), 2.08−1.96 (m, 2H), 0.90 (t, J = 6.0 Hz, 2H). Anal. Calcd for C32H33Cl2N5O5S2Zn2: C, 46.11; H, 3.99; N, 8.40%. Found: C, 46.02; H, 3.85; N, 8.14%. Main FT-IR absorptions (KBr pellets, cm−1): 2910, 2096, 1636, 1549, 1458, 1221, 1153, 698. UV−vis (methanol, 100 μM): λmax = 373 nm. Synthesis of 4. NaN(CN)2 (0.036 g, 0.40 mmol) was dissolved in ethanol (10 mL) and added into a solution of 1a (0.139 g, 0.10 mmol) in ethanol (40 mL). The mixture was stirred for 24 h at room temperature and filtered. The filtrate was concentrated to give 4 in a yield of 0.127 g (91%). 1H NMR (300 MHz, CD3OD): δ 8.28−8.13 (m, 4H), 7.64−7.08 (m, 18H), 3.76−3.63 (m, 8H), 3.56−3.34 (m, 8H), 3.17−3.10 (m, 8H), 3.09−2.93 (m, 8H), 1.30 (dd, J = 7.0, 4.1 Hz, 8H). Anal. Calcd for C124H128Cl8N18Na4O18Zn4: C, 53.27; H, 4.61; N, 9.02%. Found: C, 53.21; H, 4.55; N, 8.97%. Main FT-IR absorptions (KBr pellets, cm−1): 2920, 2287, 2228, 2172, 2127, 1630, 1547, 1437, 1344, 1126, 698. UV−vis (methanol, 100 μM): λmax = 367

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was financially supported by the Major State Basic Research Development Programs (Nos. 2013CB922101 and 2011CB933300), the National Natural Science Foundation of China (No. 21171088), and the Natural Science Foundation of Jiangsu Province (Grant BK20130054).

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REFERENCES

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DOI: 10.1021/acs.inorgchem.5b01451 Inorg. Chem. XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.inorgchem.5b01451 Inorg. Chem. XXXX, XXX, XXX−XXX