Entanglement and Irreversible Structural Transformation in Co(II

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Entanglement and Irreversible Structural Transformation in Co(II) Coordination Polymers Based on Isomeric Bis-pyridyl-bis-amide Ligands Chih-Hsun Hsu, Wei-Chun Huang, Xiang-Kai Yang, ChihTung Yang, Pradhumna Mahat Chhetri, and Jhy-Der Chen Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b01706 • Publication Date (Web): 08 Feb 2019 Downloaded from http://pubs.acs.org on February 8, 2019

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Crystal Growth & Design

Entanglement and Irreversible Structural Transformation in Co(II) Coordination Polymers Based on Isomeric Bis-pyridyl-bis-amide Ligands

Chih-Hsun Hsu,a Wei-Chun Huang,a Xiang-Kai Yang,a Chih-Tung Yang,a Pradhumna Mahat Chhetria,b and Jhy-Der Chen*a aDepartment

of Chemistry, Chung Yuan Christian University, Chung-Li, Taiwan, R.O.C.

bDepartment

of Chemistry, Amrit Science Campus, Tribhuvan University, Kathmandu, Nepal

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Abstract Four coordination polymers constructed from the flexible isomeric bis-pyridyl-bis-amide (bpba) ligands, N,N’-di(3-pyridyl)suberoamide (L1) and

N,N’-di(4-pyridyl)suberoamide

(L2), and

the

auxiliary

1,4-

naphthalenedicarboxylic acid (1,4-H2NDC), including [Co(L1)1.5(1,4NDC)(H2O)]n, 1, [Co3(L1)1.5(1,4-NDC)3(EtOH)]n, 2, {[Co(L2)1.5(1,4NDC)]H2O}n, 3, and {[Co(L2)0.5(1,4-NDC)]·EtOH}n, 4, have been synthesized and structurally characterized by using single crystal X-ray crystallography. Complex 1 forms a 2D layer with double edges and 2 exhibits a unique 3D self-catenated framework with the (48.66.8)-6T60 topology, while 3 displays a 3D framework with the highest five-fold interpenetration for the bnn topology and 4 shows a 3D 2-fold interpenetrated framework with the pcu topology. The donor atom positions of the L1 and L2 ligands and the identity of the solvents play important roles in determining the structural diversity. Moreover, irreversible structural transformation from 2 to 1 has been verified by immersing crystals of 2 into water. The coordination ability of the CH3CH2OH molecule in 2 and the thermal stability of 1 govern the irreversible structural transformation.


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Introduction Coordination polymers (CPs) have received much attention not only for their charming structures and distinctive topologies, but also for their numerous potential applications,1-4 such as gas storage, separation, magnetism, catalysis, and ion exchange.5-7 The structural types of CPs are susceptible to many factors, involving the nature of metal ions, linkers and counter ions, ratio of metal and ligand and coordination and cocrystallization of solvents. Therefore, it has become an important topic to employ the appropriate factors to design and construct the CPs with desired property. Although many interesting CPs have been reported, the control of structural dimensionality and entanglement is still a challenge. The crystal-to-crystal transformations of CPs are infrequent due to the involvement of breaking and forming of coordinate and/or covalent bonds in more than one direction,8-10 which can be initiated by various methods such as removal and uptake of solvents, exchange of solvents and guest molecules, exposure to reactive vapors and external stimuli like heat, light and mechanical forces. Such phenomena are intriguing in CPs due to their potential applications as switches and sensors.11 Moreover, the structural transformations that have been reported generally focused on the change of the initial and the final structures.9 The factors that direct the structural change remain scarcely investigated. Entanglement is a common phenomenon in the crystal engineering of CPs, which may happen in a crystal to maximize its packing efficiency due to the presence of large free voids in a single network.12 Polycatenation that results in network with higher dimension generally contains three discrete rings entangled in a way that they cannot be separated without breaking one of the rings, whereas interpenetration that retains the dimension can be ascribed to the occupation of the voids associated with one framework by one or more 3 ACS Paragon Plus Environment


independent frameworks and they can be disentangled only by breaking all the internal connections. The self-catenated nets are single nets that exhibit the peculiar feature of containing shortest rings through which pass other components of the same network.13 The intriguing bis-pyridyl-bis-amide (bpba) ligands can be tailored to provide diverse CPs with entanglement.14-15 While several onedimensional bpba-based CPs have been verified to show reversible or irreversible structural transformation,16-19 those that involve high dimensions are limited and only one example showing the irreversible transformation from a dinuclear metallocycle to a 2D pleated grid has been reported.20 To investigate the effect of ligand flexibility and isomerism of bpba on the structural types of Co(II) CPs and the impact on their properties, the Co(II) salts were reacted with the flexible isomeric ligands, N,N’-di(3-pyridyl)suberoamide (L1) and N,N’-di(4-pyridyl)suberoamide (L2), and the auxiliary 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) in different solvents, affording [Co(L1)1.5(1,4-NDC)(H2O)]n (1,4-H2NDC = 1,4-naphthalenedicarboxylic acid), 1, [Co3(L1)1.5(1,4-NDC)3(EtOH)]n, 2, {[Co(L2)1.5(1,4-NDC)]H2O}n, 3, and {[Co(L2)0.5(1,4-NDC)]·EtOH}n, 4. While complex 1 displays a single 2D layer, 2 – 4 show entangled structures. Moreover, complexes 1 and 2 display irreversible structural transformation upon solvent exchange. The synthesis and structural characterization of 1 – 4 form the subject of this report and the factors that govern the irreversible structural transformation from 2 to 1 are also discussed.


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Experimental section General Procedures Elemental analyses were performed on a PE 2400 series II CHNS/O or an Elementar Vario EL cube analyzer. IR spectra (KBr disk) were obtained from a JASCO FT/IR-460 plus spectrometer. Thermal gravimetric analyses (TGA) measurements were carried out on a TG/DTA 6200 analyzer. Powder X-ray diffraction patterns were achieved by using a Bruker D2 PHASER diffractometer with a CuKα ( = 1.54 Å) radiation. Materials The reagents Co(OAc)2H2O and 1,4-naphthalenedicarboxylic acid were

purchased

from

Alfa

Aesar.

The

ligands

N,N-di(3-

pyridyl)suberoamide (L1) and N,N’-di(4-pyridyl)suberoamide (L2) were prepared according to published procedures.14 Synthesis [Co(L1)1.5(1,4-NDC)(H2O)]n, 1. A mixture of Co(CH3CO2)2·2H2O (0.025 g, 0.10 mmol), L1 (0.033 g, 0.10 mmol) and 1,4-naphthalenedicarboxylic acid (0.022 g, 0.10 mmol) in 10 ml of H2O was sealed in a 23 mL Teflon-lined stainless steel autoclave which was heated under autogenous pressure to 120 oC for two days. The reaction system was cooled to room temperature at a rate of 2 oC per hour. Pink crystals suitable for single-crystal X-ray diffraction were generated and collected. Yield: 0.043 g (55 %). Anal. Calcd for C39H41CoN6O8 (MW = 780.71): C, 59.98; H, 5.29; N, 10.76 %. Found: C, 59.90; H, 5.23; N, 10.74 %. IR (cm-1): 3425(m), 3319(m), 3246(m), 3189(m), 3124(m), 3059 (m), 3027(m), 2942(m), 2928(m), 2903(m), 2854(m), 1951(w), 1931(w), 5 ACS Paragon Plus Environment


1698(s), 1688(m), 1676(s), 1541(s), 1487(s), 1463(m), 1455(m), 1426(s), 1397(s), 1357(s), 1329(s), 1287(s), 1277(s), 1259(m), 1233(m), 1194(m), 1176(m), 1159(w), 1137(w), 1111(w), 1078(w), 1055(w), 1027(w), 961(w), 937(w), 915(w), 880(w), 807(s), 794(s), 762(m), 712(s), 700(s), 676(m), 661(m), 640(m), 617(m), 582(w), 550(w), 520(w), 470(w), 432(w), 418(w), 409(w). [Co3(L1)1.5(1,4-NDC)3(EtOH)]n, 2. Compound 2 was prepared by following the procedure described for 1, except 10 ml EtOH was used. Purple crystals were obtained. Yield: 0.047 g (35 %). Anal. Anal. Calcd for C65H57Co3N6O16 (MW = 1354.95): C, 57.61; H, 4.24; N, 6.20 %. Found: C, 56.76; H, 4.26; N, 5.85 %. IR (cm1):

3295 (w), 3085(w), 2926 (w), 1698(w), 1680 (w), 1604(m), 1585(m),

1550(m), 1514(m), 1462(m), 1426(s), 1364(s), 1284(m), 1268(m), 1206(w), 1160(w), 1134(w), 1037(w), 961(w), 865(w), 841(w), 828(w), 811(w), 792(w), 778(m), 749(w), 697(w), 665(w), 635(w), 622(w), 586(w), 557(w), 518(w), 498(w), 454(w), 430(w), 419(m), 411(w). {[Co(L2)1.5(1,4-NDC)]·H2O}n, 3. Compound 3 was prepared by following the procedure described for 1, except L2 (0.033 g, 0.10 mmol) was used. Red crystals were obtained. Yield: 0.021 g (27 %). Anal. Calcd for C39H41CoN6O8 (MW = 780.71): C, 59.98; H, 5.29; N, 10.76 %. Found: C, 60.36; H, 5.19; N, 10.96 %. IR (cm1):

3373(w), 3269(w), 3181(w), 3090(w), 2930(m), 2857(w), 1713(m),

1686(m), 1597(s), 1517(s), 1459(m), 1416(m), 1304(m), 1357(m), 1330(m), 1294(m), 1260(w), 1230(w), 1210(m), 1159(m), 1101(w), 1014(m), 964(m), 830(m), 793(m), 777(m), 722(w), 667(w), 618(w), 502(w), 531(m), 496(w), 485(w), 478(w), 465(m), 456(w), 444(w), 434(w), 425(m), 415(m), 402(w). 6 ACS Paragon Plus Environment

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{[Co(L2)0.5(1,4-NDC)]·EtOH}n, 4. Compound 4 was prepared by following the procedure described for 3, except 10 ml EtOH was used. Purple crystals were obtained. Yield: 0.025 g (52 %). Anal. Calcd for C24H26CoN2O6.5 (MW = 505.11, 4 + 0.5 EtOH): C, 57.03; H, 5.19; N, 5.54 %. Anal. Found: C, 56.28; H, 4.59; N, 5.85 %. IR (cm-1): 3174(w), 3073(w), 2933(w), 2856(w), 1708(m), 1592(s), 1513(s), 1460(s), 1413(s), 1362(s), 1262(m), 1210(m), 1156(m), 1089(w), 1064(w), 1029(m), 977(w), 830(m), 787(m), 667(w), 606(w), 562(w), 527(w), 468(w), 458(w), 444(w), 426(w), 419(w), 408(w).

X-ray crystallography The diffraction data for complexes 1 – 4 were collected on a Bruker AXS SMART APEX II CCD diffractometer, which was equipped with a graphite-monochromated MoKα ( = 0.71073 Å) radiation.21 Data reduction was performed by standard methods with use of well-established computational procedures.22 The structure factors were obtained after Lorentz and polarization corrections. An empirical absorption correction based on “multi-scan” was applied to the data for all complexes. The positions of some of the heavier atoms were located by the direct or Patterson method. The remaining atoms were found in a series of alternating difference Fourier maps and least-square refinements, while the hydrogen atoms were added by using the HADD command in SHELXTL 6.1012. Basic information pertaining to crystal parameters and structure refinement for 2 – 4 is summarized in Table 1, and that of 1 is listed in Table S1.



Results and Discussion Structure of 1 Crystals of 1 conforms to the monoclinic space group Pī with one Co(II) ion, three halves of L1 ligand, one 1,4-NDC2- ligand and one coordinated water molecule in the asymmetric unit. Figure 1(a) shows the coordination environment about the Co(II) metal center, which is sixcoordinated by three nitrogen atoms from three L1 ligands [Co-N = 2.165(1) - 2.197(1) Å], two oxygen atoms from two 1,4-NDC2- ligands [Co-O = 2.051(1) - 2.079(1) Å] and one oxygen atom from the water molecule [Co-O = 2.150(1) Å]. The Co(II) cations are linked by the 1,4NDC2- and L1 ligands to form a 2D layer with double edges, Figure 1(b). Figure 1(c) depicts a simplified drawing. Topologically, if all the L1 and 1,4-NDC2- ligands are considered as linkers and each Co(II) atom is regarded as a four-connected node, the structure of 1 can be regarded as a 4-connected net with the (44.62)-sql topology, determined using ToposPro,23 Figure 1(d). The 2D nets are supported by the coordinated water molecules via O-H---O hydrogen bonds (H---O = 1.98 Å, O---O = 2.77 Å, ∠O-H---O = 174o) to the amide carbonyl oxygen atoms of the L1 ligands and to the carboxylate oxygen atoms of the 1,4-NDC2- ligands (H---O = 1.87 Å, O--O = 2.74 Å, ∠O-H---O = 163o), Figure S1. The nets are also linked by the N-H---O hydrogen bonds from amine hydrogen atoms of the of the L1 ligands to the carboxylate oxygen atoms (H---O = 2.23 and 2.01 Å, N---O = 2.93 and 2.73 Å, ∠N-H---O = 139 and 141o) and to the amide oxygen atoms (H---O = 2.20 Å, N---O = 2.97 Å, ∠N-H---O = 150o).

It is noted that a similar structure of complex 1 has been published.24 8 ACS Paragon Plus Environment

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Because that complex 1 makes interesting comparisons with the other complexes and is a stable product of the irreversible transformation of 2, the structural description of 1 is reported herein. Structure of 2 Crystals of 2 conforms to the monoclinic space group P21/c with three Co(II) ions, three halves of L1 ligand, three 1,4-NDC2- ligands and one coordinated ethanol molecule in the asymmetric unit. Figure 2(a) shows the coordination environment about the Co(II) metal center, showing that all the Co(1), Co(2) and Co(3) metal centers are six-coordinated. Co(1) is coordinated by two nitrogen atoms from two L1 ligands [Co(1)-N = 2.121(3) - 2.201(3) Å] and four oxygen atoms from three 1,4-NDC2ligands [Co(1)-O = 2.025(3) - 2.201(3) Å], while Co(2) is coordinated by six oxygen atoms from six 1,4-NDC2- ligands [Co(2)-O = 2.009 (3) 2.211(3) Å] and Co(3) is coordinated by one nitrogen atom from the L1 ligand [Co(3)-N = 2.082 (3) Å], four oxygen atoms from three 1,4-NDC2ligands [Co(3)-O = 1.993(3) - 2.240(3) Å] and one oxygen atom from the ethanol molecule [Co(3)-O = 2.249(3) Å]. The Co(II) cations are linked by the 1,4-NDC2- ligands to form the trinuclear secondary building units, which are further connected by the L1 ligands to form a 3D framework. If each trinuclear secondary building unit is regarded as a six-connected node, the structure of 2 can be simplified as a self-catenated net with the (48.66.8)-6T60 topology, determined using ToposPro,23 Figure 2(b). Complex 2 is the first coordination network reported with such topology. Noticeably, each independent six-membered ring is catenated with the other two rings, Figure 2(c). The self-catenated net is supported by the NH---O (H---O = 2.17, 2.44 and 2.12 Å, N---O = 2.95, 3.25 and 2.87 Å, ∠ N-H---O = 148, 153 and 142o) hydrogen bonds from the amine hydrogen 9 ACS Paragon Plus Environment


atoms of the of the L1 ligands to the carboxylate oxygen atoms of the 1,4NDC2- ligands, Figure S2. Structure of 3 Crystals of 3 conform to the monoclinic space group P21/c with one Co(II) ion, three halves of L2 ligand, one 1,4-NDC2- ligand and one cocrystallized water molecule in the asymmetric unit. Figure 3(a) shows the coordination environment about the Co(II) metal center, which is sixcoordinated by three nitrogen atoms from three L2 ligands [Co-N = 2.107(2) - 2.193(2) Å] and three oxygen atoms from two 1,4-NDC2- ligands [Co-O = 2.0059(17) - 2.2514(17) Å]. The Co(II) cations are linked by the 1,4-NDC2- and L2 ligands to form a 3D framework. Topologically, each Co(II) atom can be regarded as a five-connected node, and the structure of 3 can be simplified as a 5-fold interpenetrated network with the (46.64)-bnn topology, determined using ToposPro,23 Figures 3(b) and 3(c). The five nets are related by a single translation [1,0,0], and belong to class Ia. According to the TTO database of ToposPro, the maximum number of interpenetration that has been reported for bnn in coordination networks is four and there is only one example.25 Complex 3 thus exhibits the highest number of interpenetration presently known for bnn. The five interpenetrated nets are joined in a single net by N-H---O hydrogen bonds from the amine hydrogen atoms of the L2 ligands to the amide carbonyl oxygen atoms of the other L2 ligands [H---O = 2.14 Å, N--O = 2.89 Å N-H---O = 161o] and to the carboxylate oxygen atoms of the 1,4-NDC2- ligands [H---O = 2.34 Å, N---O = 3.10 Å, N-H---O = 146o; H--O = 2.45 Å, N---O = 3.02 Å N-H---O = 124o], Figure S3. The water molecules are also involved in hydrogen bonds with the 1,4-NDC2- ligands through O-H---O (H---O = 2.41 and 2.50 Å, O---O = 2.79 and 2.79 Å, O10 ACS Paragon Plus Environment

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H---O = 108 and 101o. Structure of 4 Crystals of 4 conform to the monoclinic space group C2/c with one Co(II) ion, one half of L2 ligand, one 1,4-NDC2- ligand and one cocrystallized ethanol molecule in the asymmetric unit. Figure 4(a) shows the coordination environment about Co(II) metal center, which is fivecoordinated by one nitrogen atom from one L2 ligand [Co-N = 2.051(3) Å] and four oxygen atoms from four 1,4-NDC2- ligands [Co-O = 2.005(2) 2.135(2) Å]. The adjacent Co(II) ions are connected by 1,4-NDC2- ligands to give dinuclear units with the distance of

Co---Co being 2.8692 Å.

Furthermore, the Co(II) anions are linked by1,4-H2NDC2- and L2 ligands to form a 3D framework. Topologically, each Co(II) atom can be regarded as a five-connected node and the 1,4-NDC2- ligand as a four-connected node,

resulting

in

a

2-fold

interpenetrated

network

with

the

(42,62,82)(46,64)-xah topology (standard representation), determined using ToposPro,23 Figure 4(b). If the dinuclear Co2 units are regarded as a 6connected node, the structure of 4 can be further simplified as a 2-fold interpenetrated

network

with

the

(412,63)-pcu

topology

(cluster

representation), Figure 4(c).26 The 2-fold interpenetrated net is supported by the N-H---O (H---O = 2.22 Å, N---O = 3.03 Å, ∠ N-H---O = 152o) hydrogen bonds from the amine hydrogen atoms of the of the L2 ligands to the carboxylate oxygen atoms of the 1,4-NDC2- ligands, Figure S4. Ligand conformations and bonding modes The long carbon chains in the middle of L1 and L2 make them quite flexible. The L1 and L2 can be arranged in A and G conformations, which are given when the C-C-C-C torsion angle () is 180   > 90o and

0

 90o, respectively. On the basis of the relative orientation of the C=O (or 11 ACS Paragon Plus Environment


N-H) groups, each conformation can adopt cis or trans arrangement.14 Due to the difference in the orientations of the pyridyl nitrogen atom positions, three more orientations, anti-anti, syn-anti and syn-syn, are possible for the ligand. The ligand conformations of complexes 1 – 4 are assigned accordingly and listed in Table 2. The two independent L2 ligands in 3 adopt the same AAAAA-trans conformation, although their C-C-C-C torsional angles are significant different. The 1,4-NDC2- ligands in 1 – 4 adopt various types of bonding modes. While the bonding mode in 1 is μ2-κ1,κ0,κ1,κ0, Figure 5(a), those in 2 show three different bonding modes, which are μ4-κ1,κ1,κ1,κ1, Figure 5(b), μ3κ1,κ1,κ1,κ1, Figure 5(c), and μ4-κ2,κ1,κ1,κ1, Figure 5(d), respectively. The 1,4-NDC2- ligand in 3 adops the μ2-κ1,κ1,κ1,κ0 bonding mode, Figure 5(e), and that in 4 is μ4-κ1,κ1,κ1,κ1. To show the distinctive 3D self-catenated framework with the (48.66.8) topology, the 1,4-NDC2- ligands in 2 adopt three different bonding modes, which is unique for the 1,4-NDC2- ligands in a single structure. Structural diversity Structural comparisons for complexes 1 - 4 reveal the important roles of solvent and ligand-isomerism in the structural diversity. Different donor atom positions of L1 and L2 result in various bonding modes for the 1,4NDC2- ligands and different coordination abilities for the H2O and EtOH molecules. While the H2O and EtOH molecules in 1 and 2 are coordinated to the Co(II) metal centers, those in 3 and 4 are cocrystallized with the metal complexes, resulting in a 2D layer with double edges, a 3D selfcatenated framework with the (48.66.8)-6T60 topology, a 3D 5-fold interpenetrated framework with the bnn topology and a 3D 2-fold interpenetrated framework with the pcu topology, respectively. Other 12 ACS Paragon Plus Environment

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things being equal, the structural differences in the pairs of 1 and 2, and 3 and 4 are subject to the nature of the H2O and EtOH molecules, while in the pairs of 1 and 3, and 2 and 4 the effect of the ligand-isomerism of L1 and L2. Thermal properties In order to estimate the thermal properties of the structures, thermal gravimetric analysis (TGA) of complexes 1 – 4 were carried out in the nitrogen atmosphere from 30 to 1000 oC, Figure S5 – Figure S8 and Table 3. The TGA curve of 1 shows the gradual weight loss of the coordinated water molecules (calculated 2.3 %, observed 2.5 %) in 160 – 250 oC and the weight loss of 86.3 % in 300 – 900 oC corresponds to the decomposition of L1 and 1,4-NDC2- ligands (calculated 90.1 %), while the TGA curve of 2 shows the gradual weight loss of the coordinated ethanol molecules (calculated 3.4 %, observed 2.1 %) in 30 – 204 oC and the weight loss of 86.1 % in 204 – 850 oC can be ascribed to the decomposition of L1 and 1,4-H2NDC2- ligands (calculated 83.6 %). For complex 3, the TGA curve shows the removal of the crystallized water molecules in 30 – 285 oC and weight loss of 89.8 % in 285 – 1000 oC is due to the decomposition of L2 and 1,4-H2NDC2- ligands (calculated 90.1 %). The TGA curve of 4 shows the removal of the crystallized EtOH molecules in 30 – 310 oC and the host framework collapses in 310 - 900 oC

with a weight loss of 81.9 % due to decomposition of L2 and 1,4-

H2NDC2- ligands (calculated 78.2 %).

Irreversible structural transformation due to solvent exchange It is worthwhile to investigate the factors that govern the structural transformation in high dimensional bpba-based CPs since entangled networks of this type have never been found to perform structural 13 ACS Paragon Plus Environment


transformation. To investigate the transformation due to solvent exchange, we first checked the purities of complexes 1 and 2 by measuring their powder X-ray diffraction patterns. Figures S9 and S10 show that the powder patterns of these two complexes match quite well with those simulated from single-crystal X-ray data, indicating the bulk purities of these complexes. We then investigated the feasibility of structural transformation due to solvent exchange for these CPs. Figure 6 shows the irreversible structural transformation between 1 and 2. Complex 1 was first immersed into various organic solvents at room temperature for one week, and it was shown that no change can be observed, as depicted in Figure S13. We then tried to remove the coordinated water molecules of complex 1 by heating it at 250 °C under vacuum to give the dehydrated 1 (1’), Figure S14. Complex 1’ was then allowed to absorb various organic solvents at room temperature for one week to explore the structural change. However, the powder X-ray patterns remain unchanged, Figure S15. Even refluxing or hydrothermally reacting 1’ in EtOH could not change the powder pattern, indicating the stability of 1’, Figure S16 and Figure S17. It is noteworthy that 1’ could only be transformed back to 1 by soaking water for one week, Figure S18. Fortunately, when complex 2 was immersed into water, a vigorous reaction was observed. After standing for 1 day, the color of the complex changed from purple to pink. The solid was then collected and investigated by using the PXRD patterns, Figure 7, which demonstrates the irreversible crystalto-crystal transformation due to solvent exchange. On the other hand, immersing 4 into H2O afforded light yellow solid that displayed PXRD patterns different from those of 3 and 4, Figure S19. The structural transformation in supramolecular isomers27 that 14 ACS Paragon Plus Environment

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comprise network structures that have identical chemical compositions but differ from one another in their structures is feasible because no gain or loss of ligands is demanded.16-20 However, for those that are not supramolecular isomers, decomposition of the complex or rearrangement of the ligands during the process is anticipated. It is thus worthwhile to comment on the irreversible structural transformation between 1 and 2. In complex 1, the ratio of Co : L1 : 1,4-NDC2- is 1 : 1.5 : 1, while that in 2 is 3 : 1.5 : 3. On the basis of the metal to ligand ratio, decomposition of 2 is thus necessary for the formation of 1, which also demonstrates the irreversibility of the structural transformation from 2 to 1. The average yield for the structural transformation is about 71 % based on three experiments, Figure. S20. Figure 8 shows that the removal of the coordinated CH3CH2OH molecules of 2 started from 30 oC and the organic ligands

(L1 and 1,4-

NDC2-) decomposed at 204 oC, while the removal of the coordinated H2O molecules of 1 occurred in 160 – 250 oC and the organic ligands decomposed at 300 oC, indicating the weaker coordination of the CH3CH2OH molecules to the Co(II) metal ions than the H2O molecules and the better stability of the framework of 1 than 2. The irreversible structural transformation from 2 to 1 can thus most probably be ascribed to the weak coordination ability of the CH3CH2OH molecules and weak framework strength of 2 due to the formation of the self-catenated net with a (48.66.8)6T60 topology, which triggered the decomposition of the complex and rearrangement of the ligands upon immersing to water to conform to the structure of 1 that is more thermally stable. Conclusion Four new Co(II) CPs constructed from the flexible bpba, L1 and L2, 15 ACS Paragon Plus Environment


and 1,4-NDC2- ligands have been successfully synthesized. Complex 1 forms a 2D layer with double edges and 2 exhibits a unique 3D selfcatenated framework with the (48.66.8)-6T60 topology, while 3 displays a 3D framework with the highest five-fold interpenetration for the bnn topology and 4 shows a two-fold interpenetrated 3D framework with the pcu topology. The structural diversity is directed by the ligand-isomerism of L1 and L2 as well as the identity of the solvents. Complexes 1 and 2 display irreversible structural transformation upon solvent exchange, which may demonstrate that the 3D self-catenated framework of 2 is thermally less stable than the 2D layer of 1. The weak coordination ability of CH3CH2OH molecules and the weak strength of the self-catenated framework of 2 are responsible for the initiation of the structural transformation. This study provides an insight into understanding the irreversibility of the structural transformation of the entangled CPs. ASSOCIATED CONTENT Supporting information Hydrogen bonds (Figure S1 - Figure S4). TGA curves (Figure S5 - Figure S8). PXRD patterns for 1 – 4 (Figure. S9 – Fig. S19). Experimental data (Figure S20). Crystal data of 1 (Table S1). The supporting information is available free of charge on the ACS Publications website at DOI: xxxx. Accession Codes CCDC no. 1874247 - 1874250 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336 033; or e-mail: [email protected] or www: http://www.ccdc.cam.ac.uk. 16 ACS Paragon Plus Environment

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AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected] (JDC) Notes The authors declare no competing financial interest. ACKNOWLEDGEMENTS We are grateful to the Ministry of Science and Technology of the Republic of China for support. Reference (1) Tiekink, E. R. T.; Vittal, J. J. Frontiers in Crystal Engineering, John Wiley & Sons, Ltd., England, 2006. (2) Li, J. R.; Kuppler, R. J.; Zhou, H. C. Selective gas adsorption and separation in metal–organic frameworks. Chem. Soc. Rev. 2009, 38, 1477–1504. (3) Allendorf, M. D.; Bauer, C. A.; Bhakta, R. K.; Houk, R. J. T. Luminescent metal–organic frameworks. Chem. Soc. Rev. 2009, 38, 1330-1352. (4) Moulton, B; Zaworotko, M. J. From Molecules to Crystal Engineering: Supramolecular Isomerism and Polymorphism in Network Solids. Chem. Rev. 2001, 101, 1629-1658. (5) Morrison, C. N.; Powell, A. K.; Kostakis, G. E. Influence of Metal Ion on Structural Motif in Coordination Polymers of the Pseudopeptidic Ligand Terephthaloyl-bis-beta-alaninate Cryst. Growth Des. 2011, 11, 3653-3662. (6) Dong, L.; Chu, W.; Zhu, Q.; Huang, R. Three Novel Homochiral 17 ACS Paragon Plus Environment


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Helical Metal-Organic Frameworks Based on Amino Acid Ligand: Syntheses, Crystal Structures, and Properties. Cryst. Growth Des. 2011, 11, 93-99. (7) Hao, Y.; Wu, B.; Li, S.; Liu, B.; Jia, C.; Huang, X.; Yang, X. Onedimensional coordination polymers of a flexible bis(pyridylurea) ligand. CrystEngComm 2011, 13, 6285-6292. (8) Vittal, J. J. Supramolecular structural transformations involving coordination polymers in the solid state. Coord, Chem. Rev. 2007, 251, 1781-1795. (9) Kole, G. K.; Vittal, J. J. Solid-state reactivity and structural transformations involving coordination polymers. Chem. Soc. Rev. 2013, 42, 1755-1775. (10) Marti-Rujas, J.; Kawano, M. Kinetic Products in Coordination Networks: Ab Initio X‑ray Powder Diffraction Analysis. Acc. Chem. Res. 2013, 46, 493-505 (11) Chen, X.; Shen, S.; Guo, L.; Mao, S. S. Semiconductor-based Photocatalytic Hydrogen Generation. Chem. Rev. 2010, 110, 65036570 (12) Batten, S. R.; Robson, R. Interpenetrating Nets: Ordered, Periodic Entanglement. Angew. Chem. Int. Ed. 1998, 37, 1460-1494. (13) Carlucci, L.; Ciani, G.; Proserpio, D. M. Polycatenation, polythreading and polyknotting in coordination network chemistry. Coord. Chem. Rev. 2003, 246, 247-289. (14) Thapa, K. B.; Chen, J.-D. Crystal engineering of coordiantion polymers

containing

flexible

bis-pyridyl-bis-amide

ligands.

CrystEngComm 2015, 17, 4611-4626. (15) Zhang, J.-W.; Kan, X.-M.; Li, X.-L.; Luan, J.; Wang, X.-L. Transition metal carboxylate coordination polymers with amidebridged

polypyridine

coligands:

assemblies


and

properties

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CrystEngComm 2015, 17, 3887-3907. (16) Chhetri, P. M.; Yang, X.-K.; Chen, J.-D. Mercury halide coordination

polymers

exhibiting

reversible

structural

transformation. CrystEngComm 2018, 20, 2126-2134. (17) Chhetri, P. M.; Yang, X.-K.; Chen, J.-D. Solvent-Mediated Reversible

Structural

Transformation

of

Mercury

Iodide

Coordination Polymers: Role of Halide Anions. Cryst. Growth Des. 2017, 17, 4801-4809. (18) Thapa, K. B.; Hsu, Y.-F.; Lin, H.-C.; Chen, J.-D. Hg(II) supramolecular

isomers:

structural

transformation

and

photoluminescence change. CrystEngComm 2015, 17, 7574-7582. (19) Hsu, Y.-F.; Hsu, W.; Wu, C.-J.; Cheng, P.-C.; Yeh, C.-W.; Chang, W.-J.; Chen , J.-D.; Wang, J.-C. Roles of halide anions in the structural diversity of Zn(II) complexes containing the flexible N,N’-di(4-pyridyl)adipoamide ligand. CrystEngComm 2010, 12, 702-710. (20) Cheng, P.-C.; Yeh, C.-W.; Hsu, W.; Chen, T.-R.; Wang, H.-W.; Chen, J.-D.; Wang, J.-C. Ag(I) Complexes Containing Flexible N,N’-di(3-pyridyl)adipoamide Ligands: Syntheses, Structures, Ligand Conformations and Crystal to Crystal Transformations. Cryst. Growth Des. 2012, 12, 943-953. (21) Bruker AXS, APEX2, V2008.6; SAD ABS V2008/1; SAINT+ V7.60A; SHELXTL V6.14; Bruker AXS Inc.: Madison, Wisconsin, USA, 2008. (22) Sheldrick, G. M. A Short History of SHELX. Acta Crystallogr. 2008, A64, 112-122. (23) Blatov, V. A.; Shevchenko, A. P.; Proserpio, D. M. Applied Topological Analysis of Crystal Structures with the Program Package ToposPro. Cryst. Growth Des. 2014, 14, 3576-3586. 19 ACS Paragon Plus Environment


(24) Lin, H.; Rong, X.; Liu, G.; Wang, X. Wang, X.; Duan, S. Fluorescent sensing and electrocatalytic properties of three Zn(II)/Co(II) coordination complexes containing two different dicarboxylates and two various bis(pyridyl)-bis(amide) ligands. J. Mol. Struct. 2016, 1119, 396-403. (25) Dai, J.-C.; Wu, X.-T.; Hu, S.-M.; Fu, Z.-Y.; Zhang, J.-J.; Du, W.-X.; Zhang, H.-H.; Sun, R.-Q. Crystal Engineering of the Coordination Architecture of Metal Polycarboxylate Complexes by Hydrothermal Synthesis: Assembly and Characterization of Four Novel Cadmium Polycarboxylate Coordination Polymers Based on Mixed Ligands. Eur. J. Inorg. Chem. 2004, 2096-2106. (26) Bonneau,C.; O’Keeffe, M.; Proserpio, D. M.; Blatov, V. A.; Batten, S. R.; Bourne, S. A. Lah, M. S.; Eon, J.-G.; Hyde, S. T.; Wiggin, S. B.; Öhrström, L. Deconstruction of Crystalline Networks into Underlying Nets: Relevance for Terminology Guidelines and Crystallographic Databases. Cryst. Growth Des. 2018, 18, 34113418. (27) Zhang, J.-P.; Huang, X.-C.; Chen, X.-M. Supramolecular isomerism in coordination polymers. Chem. Soc. Rev. 2009, 38, 2385- 2396.


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Table 1. Crystal data for complexes 2 - 4. compound

2

3

4

Formula

C65H57Co3N6O16

C39H41CoN6O8

C23H2CoN2O6

Formula weight

1354.95

780.71

482.36

crystal system

Monoclinic

Monoclinic

Monoclinic

space group

P21/c

P21/c

C2/c

a, Å

28.8409(3)

12.9851(2)

23.9316(11)

b, Å

16.0971(2)

18.6950(3)

14.0755(7)

c, Å

12.8605(2)

16.2718(3)

16.0407(8)

α,

90

90

90

,

100.355(1)

105.135(1)

121.920(2)

γ,

90

90

90

V, Å3

5873.31(13)

3813.07(11)

4586.2(4)

Z

4

4

8

dcalc, mg/m3

1.532

1.360

1.397

F (000)

2792

1632

2000

µ (MoK), mm-1

0.916

0.510

0.789

Range (2) for data

2.908 2  51.998

3.250 2  56.578

3.520 2  51.990

11544

9466

4500

[R(int) = 0.0382]

[R(int) = 0.0490]

[R(int) = 0.0394]

11544 / 6710 / 815

9466 / 0 / 496

4500 / 4 / 286

quality-of-fit indicator c

1.036

1.013

1.065

final R indices

R1 = 0.0360,

R1 = 0.0509,

R1 = 0.0465,

wR2 = 0.0886

wR2 = 0.1093

wR2 = 0.1224

R1 = 0.0501,

R1 = 0.1193,

R1 = 0.0682,

wR2 = 0.0956

wR2 = 0.1333

wR2 = 0.1355

collection, deg independent reflections

data / restraints / parameters

[I > 2(I)] R indices (all data) aR

1

a,b

= Fo – Fc / Fo. bwR2 = [w(Fo2 – Fc2)2 / w(Fo2)2]1/2.

w = 1 / [2(Fo2) + (ap)2 + (bp)], p = [max(Fo2 or 0) + 2(Fc2)] / 3. a = 0.0392 b = 4.1073 for 2; a = 0.0549 b = 0.7512 for 3; a = 0.0570 b = 12.2788 for 4. cquality-of-fit

= [w(Fo2 – Fc2)2 / Nobserved – Nparameters )]1/2.



Page 22 of 33

Table 2. The ligand conformations of L1 and L2 in 1 – 4.

1

2

-176.426(2), 179.519(2), 177.152(2),

AAAAA-trans

179.269(2), 168.152(2)

syn-anti

178.960(2), 179.944(2), 180.000(2),

AAAAA-trans

-179.944(2), 178.960(2)

syn-syn

-74.943(6), -177.624(4), -180.000(4),

GAAAA-trans

177.624(4), 74.943(6)

syn-syn

77.751(7), -167.076(6), -49.286(1),

GAGGG-cis

-61.532(1), -75.496(1)

syn-syn

176.879(1), -177.646(2), -178.887(2),

AAAAA-trans

179.375(2), -175.435(2)

3

-172.421(2), -90.694(3), 180.000(2),

AAAAA-trans

90.694(3), 172.421(2) 167.418(3), 178.378(3), -180.000(3),

4

178.378(3), -167.419(3)


AAAAA-trans

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Table 3. Thermal properties of complexes 1 – 4 . Complex

Weight loss of solvent, oC (found / calc, %)

Weight loss of ligand, oC (found / calc, %)

1

160 - 250 (2.5/2.3)

300 - 900 (86.3/90.1)

2 3

30 - 204 (2.1/3.4) 30 - 285 (1.0/2.3) 30 - 310 (8.4/9.5)

204 - 850 (86.1/83.6) 285 - 1000 (89.8/90.1) 310 - 900 (81.9/78.2)

4



Captions Figure 1. (a) Coordination environment about the Co(II) ion in 1. (b) A drawing showing the 2D layer with double edges. (c) A drawing showing the simplified 2D layer with 1D channels. (d) A drawing showing the network with the sql topology. Figure 2. (a) Coordination environment about the Co(II) ions in 2. The L1 ligands are represented by pyridyl nitrogen atoms for clarity. (b) A drawing showing self-catenated net with the (48.68.8)-6T60 topology. (c) A drawing showing that one ring is catenated with two rings. Figure 3. (a) Coordination environment about the Co(II) ions in 3. (b) A drawing showing 5-connected net with the bnn topology. (c) A drawing showing the 5-fold interpenetrated network. Figure 4. (a) Coordination environment about the Co(II) ions in 4. (b) A drawing showing the 2-fold interpenetrated network with the xah topopogy. (c) A drawing showing the 2-fold interpenetrated network with the pcu topopogy. Figure 5. The various bonding modes of 1,4-NDC2- ligands in 1 – 4. Figure 6. Crystal-to-Crystal transformation between complexes 1 and 2. Figure 7. The PXRD patterns of complex 2 and 2 in water for 1 day. Figure 8. TGA curves of 1 and 2.


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(a)

(b)

(c)

(d)

Figure 1 25 ACS Paragon Plus Environment


(a)

(b)

(c) Figure 2 26 ACS Paragon Plus Environment

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(a)

(b)

(c)



(a)

(b)

(c) Figure 4 28 ACS Paragon Plus Environment

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Figure 6


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Figure 7



Figure 8


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For Table of Contents Use Only

Entanglement and Irreversible Structural Transformation in Co(II) Coordination Polymers Based on Isomeric Bis-pyridyl-bis-amide Ligands

Chih-Hsun Hsu,a Wei-Chun Huang,a Xiang-Kai Yang,a Chih-Tung Yang,a Pradhumna Mahat Chhetria,b and Jhy-Der Chen*a aDepartment

of Chemistry, Chung-Yuan Christian University, Chung-Li, Taiwan, R.O.C.

bDepartment

of Chemistry, Amrit Science Campus, Tribhuvan University, Kathmandu, Nepal

Co(II) coordination polymers constructed from the flexible isomeric bis-pyridyl-bis-amide and the auxiliary 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) which exhibit interesting entangled structural types and irreversible structural transformation are reported.


Entanglement and Irreversible Structural Transformation in Co(II

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