Solid State and Solution Mediated Multistep Sequential

Article pubs.acs.org/crystal

Solid State and Solution Mediated Multistep Sequential Transformations in Metal−Organic Coordination Networks Published as part of the Crystal Growth & Design virtual special issue In Honor of Prof. G. R. Desiraju Partha Mahata,† Caroline-Mellot Draznieks,‡ Partha Roy,§ and Srinivasan Natarajan*,# †

School of Chemistry and Bio-Chemistry, Thapar University, Patiala 147004, India Laboratoire de Chimie des Processus Biologiques, Collège de France, 11 Place Marcelin Berthelot, 75005 Paris, France § Department of Chemistry, Jadavpur University, Kolkata # Framework Solids Laboratory, Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, India ‡

S Supporting Information *

ABSTRACT: Sequential transformation in a family of metal− organic framework compounds has been investigated employing both a solid-state as well as a solution mediated route. The compounds, cobalt oxy-bis(benzoate) and manganese oxybis(benzoate) having a two-dimensional structure, were reacted with bipyridine forming cobalt oxy-bis(benzoate)4,4′-bipyridine and manganese oxy-bis(benzoate)-4,4′-bipyridine, respectively. The bipyridine containing compounds appear to form sequentially through stable intermediates. For the cobalt system, the transformation from a two-dimensional compound, [Co(H2O)2(OBA)] (OBA = 4,4′-oxy-bis(benzoate)), I, to two different three-dimensional compounds, [Co(bpy)(OBA)]·bpy, II, (bpy = 4,4′-bipyridine) and [Co(bpy)0.5(OBA)], III, and reversibility between II and III have been investigated. In the manganese system, transformation from a two-dimensional compound, [Mn(H2O)2(OBA)], Ia, to two different three-dimensional compounds, [Mn (bpy)(OBA)]·bpy, IIa and IIa to [Mn(bpy)0.5(OBA)], IIIa, has been investigated. It has also been possible to identify intermediate products during these transformation reactions. The possible pathways for the formation of the compounds were postulated.

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kinetic factors. Studies on the formation of cobalt succinates6 and manganese oxybis(benzoate) networks7 revealed the importance of the reaction temperature and suggests that the products may have thermodynamic control locally. The formation of less dense and more open frameworks such as MOF-5, at low temperatures, on the other hand, indicates a possible kinetic control.8 As a continuing effort to further our understanding of the formation of metal−organic coordination network compounds, a multistep sequential transformation could be employed. In this process, a low-dimensional simple precursor could be prepared, which then can be employed as a starting material for the subsequent transformation to higher-dimensional structures.9 The studies involving the transformation of lowdimensional structures to structures of higher dimensionality have been carried out for the formation of open structures. This approach provided important pointers toward our understanding of the formation of open-framework structures.10 Some of the transformation studies have been carried out on simple molecular complexes employing a number of reactants.10 Studies of this nature are not common in inorganic

INTRODUCTION The metal−organic coordination compounds exhibit interesting structures and properties that were only imaginable a few decades ago.1 Metal−organic coordination networks are generally formed from two structural units, viz., the metal ions or metal clusters and the organic linkers.2 Among the various linkers, the aromatic carboxylate (anionic) and the nitrogen containing heterocyclic compounds (neutral/anionic) appear to be the two of most frequently employed linkers during the synthesis of such compounds.3 The often employed, conventional one pot synthesis via solvo/hydrothermal reactions has been remarkably successful, creating many interesting metal−organic coordination networks through careful selection of the organic linkers and the metal ions.4 The formation of such compounds appears to depend on many different parameters such as the reaction temperature, time, pH, the concentration of the starting materials, and the solvent.1,5 Though this synthesis approach is routinely employed and successful, it does not provide sufficient information on the possible pathways leading to the formation of the coordination networks. Thus, the mechanism of formation of these compounds has not been investigated in great detail so far. One of the important issues during the synthesis of the coordination framework compounds could be the possible competition between the thermodynamic and the © 2012 American Chemical Society

Received: September 7, 2012 Revised: November 7, 2012 Published: December 5, 2012 155

dx.doi.org/10.1021/cg301306m | Cryst. Growth Des. 2013, 13, 155−168

Crystal Growth & Design

Article

Table 1. Detailed Hydrothermal Synthesis Conditions and Analysis of Compounds I−III, IIa, and IIIaa synthesis conditions compounds

mole ratio

T (K)

time (h)

pHb

yieldc (%)

[Co(H2O)2{C12H8O(COO)2}], I [Co{C12H8O(COO)2}{C10H8N2}]·C10H8N2, II [Co{C12H8O(COO)2}{C10H8N2}0.5], III [Mn{C12H8O(COO)2}{C10H8N2}]·C10H8N2, IIa [Mn{C12H8O(COO)2}{C10H8N2}0.5], IIIa

Co(OAc)2·4H2O: H2OBAd: 2NaOH: 555H2O Co(OAc)2·4H2O: H2OBAd: 2bpye: 2NaOH: 555H2O Co(OAc)2·4H2O: H2OBAd: bpye: 2NaOH: 555H2O Mn(OAc)2.4H2O: H2OBAd: 2bpye: 2NaOH: 555H2O Mn(OAc)2.4H2O: H2OBAd: bpye: 2NaOH: 555H2O

383 383 453 383 453

48 24 24 24 24

5(5) 6(5) 5(5) 6(5) 5(5)

75 75 70 75 80

a

Elemental analysis: Anal. Calcd for I: C 47.84, H 3.42. Found: C 47.9, H 3.35; Anal. Calcd for II: C 65.02, H 3.82, N 8.92. Found: C 64.9, H 3.9, N 8.85; Anal. Calcd for III: C 57.98, H 3.05, N 3.56 Found: C 57.9, H 3.10, N 3.45; Anal. Calcd for IIa: C 65.43, H 3.85, N 8.98. Found: C 65.4, H 3.9, N 9.02; Anal. Calcd for IIIa: C 58.58, H 3.08, N 3.6. Found: C 58.6, H 3.1, N 3.5. bNumbers in the parentheses denote the final pH. cYield has been calculated based on the metal ions. dH2OBA = 4,4′-oxy bis(benzoic acid). e4,4′-Bipyridine.

chemistry, though sequential transformations/reactions are very routine in organic chemistry. In organic chemistry, multistep sequential syntheses are common, as exemplified during the total synthesis of many natural products of complex biomolecules from simple starting materials.11 On the contrary, multistep syntheses in the preparation of metal−organic coordination networks are relatively rare.12 It is believed that the metal−organic coordination networks can be constructed employing the principles of crystal engineering adumbrated expertly by Desiraju.13 The studies on the transformation of metal−organic coordination networks can be classified into two categories: (1) compounds that are flexible and undergo dehydration/ desolvation or rehydration/resolvation without any major changes in the crystal structures; (2) compounds that undergo changes involving breaking and reforming of framework bonds. Examples of the former type of transformation includes the breathing of metal-organic frameworks (MOFs)14 and others in which the structural changes were brought about by the application of external stimulus,15 such as thermal dehydration/ desolvation.16 The single crystal to single crystal transformation studies have been employed extensively to probe and understand the removal of the solvent molecules from the pore or the removal of terminal ligands such as water, DMF, etc. The examples of such transformation studies are many in the literature.17 The second type of transformations, on the other hand, are relatively rare in metal−organic coordination networks.9 It may be noted that the second type of transformation studies has been undertaken in many amine templated open framework compounds such as phosphates,10 phosphites,18 arsenates,19 and oxalates.20 The metal−organic coordination network compounds provide unique advantages as the coordination environments around the metal centers can be varied with different ions, which would lead to bonds with different strengths. This difference in the bond strengths can be exploited in the breaking and reformation of bonds, which could also provide reasonable topochemical control during the transformation studies. The topochemical control as well as the framework structure would be lost in the absence of such facile bond breaking and formation. In order to facilitate a transformation of this nature, multistep sequential transformations could be employed. The transformation studies of this nature in metal− organic coordination network compounds can be achieved employing two different approaches: (i) the solid state, and (ii) the solution/solvent mediated. Solvent mediated transformation studies9,12 have been attempted in the literature. The solid state transformation studies are not common among the MOFs.21

The solid state transformation studies can be beneficial as the absence of solvent can be considered to be a green approach in the synthesis of crystalline compounds.22 We have been interested in the transformation studies, employing rigid organic linkers, to understand the possible pathway for the formation of the metal−organic coordination compounds both by employing the solid state and the solvent mediated approaches. This paper presents the results of the solid state and the solution mediated transformation studies of cobalt and manganese based carboxylate compounds. In the cobalt system, the transformation from a two-dimensional compound, [Co(H2O)2(OBA)] (OBA = 4,4′-oxy-bis(benzoate)), I, to two different three-dimensional compounds, [Co(bpy)(OBA)].bpy, II, (bpy = 4,4′-bipyridine) and [Co(bpy)0.5(OBA)], III, and reversibility between II and III have been investigated. In the manganese system, transformation from a two-dimensional compound, [Mn(H2O)2(OBA)], Ia, to two different threedimensional compounds, [Mn (bpy)(OBA)].bpy, IIa and IIa to [Mn(bpy)0.5(OBA)], IIIa, have been investigated.

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EXPERIMENTAL SECTION

Materials. The reagents needed for the synthesis are Co(OAc)2·4H2O [Ranbaxy (India), 98%], Mn(OAc)2·4H2O [Ranbaxy (India), 99%], CoCl2·6H2O [Ranbaxy (India), 98%], MnCl2·4H2O [Ranbaxy (India), 99%], 4,4′-oxybis(benzoic acid) [Lancaster (U.K.), 99%], 4,4′-bipyridine [Lancaster (U.K), 99%], and NaOH [CDH (India), 98%]. The water used was double distilled through a Millipore membrane. Synthesis. Compounds I-III, IIa, and IIIa were synthesized under hydrothermal conditions. In a typical synthesis, for I, Co(OAc)2·4H2O (0.249 g, 1 mM) was dissolved in 10 mL of water. To this, 4,4′-oxybis(benzoic acid) (0.26 g, 1 mM) and NaOH (0.08 g, 2 mM) were added under continuous stirring. The mixture was homogenized for 30 min at room temperature. The final mixture was then sealed in a 23 mL PTFE lined autoclave and heated at 110 °C for 2 days under autogenous pressure. The initial pH of the reaction mixture was 5, and there was no change in pH after the reaction. The final product, containing reddish pink colored plate like crystals, was filtered and washed with deionized water under a vacuum, and dried at ambient conditions (yield ∼75% based on Co). The complete synthesis conditions and yields of the products for the compounds I−III, IIa and IIIa are given in Table 1. The synthesis, structure, and characterization of the compounds III and IIa have been reported earlier by us23 and others,24 respectively. For the transformation study, compound I was prepared by a simple solvent evaporation reaction. In this preparation, 0.238 g (1 mM) CoCl2·6H2O was dissolved in 5 mL of water in a 100 mL beaker and 0.261 g (1 mM) of 4,4′-oxy-bis(benzoic) acid and 0.08 g (2 mM) of NaOH was dissolved in 5 mL of water through heating at 100 °C in a separate beaker. Then the dissolved sodium salt of the acid was poured into the cobalt salt solution and the resulting solution was kept in water bath at 80 °C for 2 day. The product of this reaction was found 156



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Table 2. Detailed of the Transformation Studies transformation conditions/observations transformation I to II II to III III to II I to II

0.25I:0.5bpy 0.2II 0.2III:0.3bpy 0.25I:0.5bpy: 222H2O

I to III

0.25I:0.25bpy: 222H2O 0.2III: 0.3bipy:222H2O 0.25Ia:0.5bpy 0.2IIa

III to II Ia to IIa IIa to IIIa a b

mole ratio

nature of products

changes of color

temperature (°C)

powder single crystal/powder powder single crystal

reddish pink to pale pink pale pink to violet violet to pale pink reddish pink to pale pink

150 250 25 180/110

45/360

single crystal

reddish pink to violet

180

180

single crystal

violet to pale pink

110

150

powder single crystal/powder

white to pale yellow pale yellow to pale brown

150 220

120 60

mode of transformation solid state (grindinga + heating) solid state (heating) solid state (grindingb) solution mediated (in 7 mL autoclave) solution mediated (in 7 mL autoclave) solution mediated (in 7 mL autoclave) solid state (grindinga + heating) solid state (heating)

time (min) 60 120

I and 4,4′-bipyridine/Ia and 4,4′-bipyridine (bpy) were mixed and manually ground for 60 min using a mortar and pestle before heating at 150 °C. III and 4,4′-bipyridine (bpy) were mixed and manually ground for 120 min.

to be microcrystalline phase of compound I. Isostructural manganese compound (Ia) was also synthesized employing a similar composition and procedure, but using MnCl2·4H2O in place of CoCl2·6H2O. Transformation Studies. The various sequential transformation studies are given Table 2. All the solid state transformation studies have been carried out in 100 mL beaker, and all the solution mediated transformation studies have been carried out in hydrothermal reaction vessels with a capacity of 7 mL. Initial Characterization and Physical Measurements. Powder X-ray Diffraction. The powder X-ray diffraction (XRD) patterns were recorded on crushed single crystals in the 2θ range 5−50° by using CuKα radiation (Philips X’pert Pro). The XRD patterns of the assynthesized compounds were entirely constituted with the simulated XRD generated from the single-crystal studies. Simulated and experimental PXRD patterns of compound I−III, IIa, and IIIa are given in Figures S1−S5 (see Supporting Information). The different phases that are formed during the transformation studies were also identified by powder X-ray diffraction (XRD). Since the Co and Mn compounds were found to be isostructural in many instances, during the present studies, the PXRD patterns were cross referenced for identification of the product phases. For example, the formation of compound Ia (Mn) was confirmed using the PXRD. The PXRD pattern of the as-synthesized manganese compound (Ia) was compared with the simulated PXRD pattern generated from the singlecrystal studies of I (Co-phase), which clearly indicated the isostructurality between the two compounds (I and Ia) (Figure S6; see Supporting Information). Infrared Spectroscopy. IR spectroscopic studies were carried out in the range 400−4000 cm−1 using the KBr pellet method (Perkin-Elmer, SPECTRUM 1000). IR spectroscopic studies exhibited typical peaks corresponding to the carboxylate group, aromatic CH etc with minor variations among the compounds (Figures S7 and S8; see Supporting Information). The observed bands are 3600−3200(s) cm−1 = ν(H2O) (only for I and Ia), 1610−1630 cm−1 = δsH2O (only for I and Ia), 1570−1500 cm−1 = νas(COO), 1400−1300 cm−1 = νa(COO), 1100− 1170 cm −1 = δ(CH aromatic ) in‑of‑plane , 900−850 cm −1 = δ(CHaromatic)out‑of‑plane, 770−740 cm−1 = δ(COO). Thermogravimetric Analysis. TGA studies have been carried out (Mettler-Toledo, TG850) in oxygen atmosphere (flow rate = 50 mL/ min) in the temperature range 25−800 °C (heating rate = 5 °C/min) (Figures S9 and S10). The detailed of TGA studies are given in Table S1 (see Supporting Information). The TGA studies of I indicate that the coordinated water molecules are removed in the temperature range of 150−170 °C (obsd. 11%, calc. 10.25%) followed by the decomposition of the framework in the range of 250−370 °C in two steps. The total observed weight loss of 78% corresponds well with the loss of the water molecules and the OBA units (calc. 77.14%). The TGA studies of II indicate the compound is stable up to 250 °C, after which the compound shows weight loss up to 390 °C and the decomposition occurs in three steps. The weight loss up to 350 °C

corresponds well with decomposition of the free 4,4′-bipyridine molecules and half of the bonded 4,4′-bipyridine (obsd. 37%, calc. 37.3%). The decomposition in the range of 350−390 °C corresponds to the decomposition of the rest of 4,4′-bipyridine molecules (bonded) and the OBA. The total observed weight loss of 86% corresponds well with the loss of 4,4′-bipyridine and the OBA units (calc. 87.2%). The TGA studies of III show a weight loss in three steps in the range of 250−430 °C. In this case, it is difficult to correlate the each step with the decomposed organic moieties. But the total observed weight loss of 81.5% corresponds well with the loss of 4,4′bipydine and the OBA units (calc. 82%). The TGA studies of IIa indicate the compound is stable up to 250 °C, after which the compound shows weight loss up to 380 °C and the decomposition occurs in three steps. The weight loss up to 270 °C corresponds well with decomposition of the free 4,4′-bipyridine molecules and half of the bonded 4,4′-bipyridine (obsd. 36.5%, calc. 37.5%). The weight loss in the range of 270−350 °C corresponds to the decomposition of the 50% of the remaining 4,4′-bipyridine (obsd. 6.5%, Calc. 6.3%). The decomposition in the range of 350−380 °C corresponds to the decomposition of the rest of 4,4′-bipyridine molecules (bonded) and the OBA. The total observed weight loss of 88% corresponds well with the loss of 4,4′-bipyridine and the OBA units (calc. 87.8%). The TGA studies of IIIa shows a weight loss in three steps in the range of 180− 420 °C. Similar to III, in this case, it is difficult to correlate each step with the decomposed organic moieties. But the total observed weight loss of 80% corresponds well with the loss 4,4′-bipyridine and the OBA units (calc. 80.5%). In all the cases the final calcined (decomposed) product was found to be crystalline by powder XRD and to correspond to the Co3O4 phase (JCPDS: 42-1467) and Mn3O4 phase (JCPDS: 75−0765), respectively, for Co compounds and Mn Compounds. Single-Crystal Structure Determination. Suitable single crystals of each of the compounds (I−III, IIa, and IIIa) were selected carefully under a polarizing microscope and glued carefully to a thin glass fiber. The single crystal data were collected on a Bruker AXS smart Apex CCD diffractometer at 293(2) K. The X-ray generator was operated at 50 kV and 35 mA using Mo Kα (λ = 0.71073 Å) radiation. Data were collected with ω scan width of 0.3°. A total of 606 frames were collected in three different setting of φ (0, 90, 180°) keeping the sample-to-detector distance fixed at 6.03 cm and the detector position (2θ) fixed at −25°. The data were reduced using SAINTPLUS,25 and an empirical absorption correction was applied using the SADABS program.26 The structure was solved and refined using SHELXL9727 present in the WinGx suit of programs (Version 1.63.04a).28 All the hydrogen atoms of the carboxylic acids were initially located in the difference Fourier maps, and for the final refinement, the hydrogen atoms were placed in geometrically ideal positions and held in the riding mode. Final refinement included atomic positions for all the atoms, anisotropic thermal parameters for all the non-hydrogen atoms, and isotropic thermal parameters for all the hydrogen atoms. Full157



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matrix least-squares refinement against |F2| was carried out using the WinGx package of programs.28 Details of the structure solution and final refinements are given in Tables 3 and 4. CCDC: 897211 (I),

Table 4. Crystal Data and Structure Refinement Parameters for [Mn{C12H8O(COO)2}{C10H8N2}]·C10H8N2, IIa, [Mn{C12H8O(COO)2}{C10H8N2}0.5], IIIaa

Table 3. Crystal Data and Structure Refinement Parameters for [Co(H2O)2{C12H8O(COO)2}], I, [Co{C12H8O(COO)2}{C10H8N2}]·C10H8N2, II, [Co{C12H8O(COO)2}{C10H8N2}0.5], IIIa structure parameter empirical formula formula weight crystal system space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) volume (Å3) Z T (K) ρcalc (g cm−3) μ (mm−1) θ range (deg) λ (Mo Kα) (Å) R indices [I > 2σ(I)] R indices (all data)

I

II

III

C14H12O7Co

C34H24N4O5Co

C19H12N1O5Co1

351.17

627.5

393.23

monoclinic P21/c (No. 14) 13.953(3) 9.914(2) 10.176(2) 90.0 104.151(4) 90.0 1364.9(5) 4 293(2) 1.709 1.291 1.51 to 28.00 0.71073

monoclinic P2/c (No. 13) 13.262(3) 11.519(2) 9.2992(18) 90.0 90.913(4) 90.0 1420.4(5) 2 293(2) 1.467 0.656 2.34 to 28.00 0.71073

monoclinic C2/c (No.15) 22.493(3) 13.6914(19) 12.7681(18) 90.0 115.723(3) 90.0 3542.4(9) 8 293(2) 1.475 0.998 1.80 to 27.95 0.71073

R1 = 0.0609, wR2 = 0.1217 R1 = 0.1008, wR2 = 0.1470

R1 = 0.0455, wR2 = 0.0984 R1 = 0.0615, wR2 = 0.1060

R1 = 0.0755, wR2 = 0.1268 R1 = 0.1270, wR2 = 0.1422

structure parameter

IIa

IIIa

empirical formula formula weight crystal system space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) volume (Å3) Z T (K) ρcalc (g cm−3) μ (mm−1) θ range (deg) λ (Mo Kα) (Å) R indices [I > 2σ(I)] R indices (all data)

C34H24N4O5Mn 623.52 monoclinic P2/c (No. 13) 13.257(3) 11.752(2) 9.3260(18) 90.0 90.284(4) 90.0 1452.9(5) 2 293(2) 1.425 0.505 2.32−28.00 0.71073 R1 = 0.0610, wR2 = 0.1015 R1 = 0.1234, wR2 = 0.1220

C19H12N1O5Mn1 389.24 monoclinic P21/c (No. 14) 13.321(2) 13.809(2) 19.818(3) 90.0 101.154(3) 90.0 3576.6(11) 8 293(2) 1.446 0.767 1.81−28.03 0.71073 R1 = 0.0483, wR2 = 0.0971 R1 = 0.0784, wR2 = 0.1094

a R1 = Σ ||F0| − |Fc||/Σ |F0|; wR2 = {Σ[w(F02 − Fc2)2]/Σ[w(F02)2]}1/2. w = 1/[σ2(F0)2 + (aP)2 + bP], P = [max.(F02,0) + 2(Fc)2]/3, where a = 0.0335 and b = 0.2796 for IIa, a = 0.0455 and b = 1.1380 for IIIa.

octahedral geometry formed by four carboxylate oxygen atoms of the OBA anions and two water molecules. The two water molecules are in cis position in the octahedral Co2+ ion. The two carboxylate groups of OBA show differences in the connectivity: one carboxylate has both the oxygens bonded with the same Co2+ ion, while the other carboxylate has the oxygens bonded with two different Co2+ ions. The selected bond distances of I are listed in Table 5. The Co2+ ions are linked through the carboxylate units [(COO)−] forming a onedimensional wire-like structure, which are further connected by the OBA unit forming a two-dimensional layer structure (Figure 1A). The layers are arranged in ABAB.... fashion (Figure 1B). Hydrogen bond interactions between the

R1 = Σ ||F0| − |Fc||/Σ |F0|; wR2 = {Σ[w(F02 − Fc2)2]/Σ[w(F02)2]}1/2. w = 1/[σ2(F0)2 + (aP)2 + bP], P = [max(F02,0) + 2(Fc)2]/3, where a = 0.0672 and b = 0.00 for I, a = 0.0461 and b = 0.7352 for II, a = 0.0564 and b = 0.00 for III. a

897212 (II) and 897213 (IIIa) contain the crystallographic data for this paper. The single crystal structures of compounds III and IIa have been reported earlier [CCDC: 604052 (III)23 and CCDC-293769 (IIa)24]. These data can be obtained free of charge from The Cambridge Crystallographic Data Center (CCDC) via www.ccdc.cam. ac.uk/data_request/cif. The unit cell parameters of Ia (Mn) were obtained from the powder X-ray diffraction patterns by the Le Bail method.29 The atomic coordinates of the I (Co compound) were employed to extract the structure factor amplitudes. The structure refinement cycles included the scale factor, the zero-point shift, the lattice parameters, and the background parameters as variables. The Le Bail method yield the following parameters for Ia: monoclinic, space group P21/c (No. 14), a = 14.020(2), b = 10.014(2), c = 10.200(2) Å, β = 105.19(2) Rp = 0.0498, wRp = 0.0750, χ2 (figure of merit) = 5.79 (for Le Bail fit see Supporting Information, Figure S11).

Table 5. Selected Bond Distances (Å) Observed in [Co(H2O)2{C12H8O(COO)2}], I, [Co{C12H8O(COO)2}{C10H8N2}].C10H8N2, II, [Co{C12H8O(COO)2}{C10H8N2}0.5], IIIa bond

distances, Å

bond

distances, Å

Co(1)−O(4)#2 Co(1)−O(5) Co(1)−O(6)

2.136(3) 2.151(3) 2.180(3)

Co(1)−O(2) Co(1)−N(1) Co(1)−N(2)#2

2.079(2) 2.200(3) 2.201(3)

Co(1)−O(4) Co(1)−N(1)

1.973(3) 2.103(3)

I

■

Co(1)−O(1) Co(1)−O(2)#1 Co(1)−O(3)

2.013(3) 2.028(3) 2.126(3)

Co(1)−O(1) Co(1)−O(1)#1 Co(1)−O(2)#1

2.075(1) 2.075(1) 2.079(2)

Co(1)−O(1) Co(1)−O(2) Co(1)−O(3)

2.012(3) 2.085(3) 2.024(3)

II

RESULTS AND DISCUSSION Structure. The structural features for all the compounds identified as part of this study are given below. This is required to understand the transformation processes/reactions better. As mentioned before, compounds I and Ia appear to have the identical structures, but we could prepare suitable single crystals for the Co compound only. The single crystal X-ray diffraction study of I showed 22 non-hydrogen atoms in its asymmetric unit, of which one cobalt atom is crystallographically independent. The Co2+ ions in I ions have a distorted

III

a Symmetry operations used to generate equivalent atoms for I: #1 x − 1, y, z − 1. #2 x − 1, −y + 1/2, z − 1/2; for II #1 −x + 1, y, −z + 3/2. #2 x, y − 1, z.

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Table 6. Selected Bond Distances (Å) Observed in [Mn{C12H8O(COO)2}{C10H8N2}]·C10H8N2, IIa, [Mn{C12H8O(COO)2}{C10H8N2}0.5], IIIaa bond

distances, Å

Mn(1)−O(1) Mn(1)−O(2) Mn(1)−O(1)#1

2.161(2) 2.147(2) 2.161(2)

Mn(1)−O(1) Mn(1)−O(2) Mn(1)−O(3) Mn(1)−O(4) Mn(1)−N(1)

2.086(2) 2.141(2) 2.157(2) 2.180(2) 2.252(2)

bond

distances, Å

Mn(1)−O(2)#1 Mn(1)−N(1) Mn(1)−N(2)

2.147(2) 2.308(3) 2.334(3)

Mn(2)−O(6) Mn(2)−O(7) Mn(2)−O(8) Mn(2)−O(5) Mn(2)−N(2)

2.071(2) 2.101(2) 2.146(2) 2.204(2) 2.234(2)

IIa

IIIa

Symmetry operations used to generate equivalent atoms for IIa: #1 −x + 1, y, −z + 3/2. a

bipyridine molecules. Thus in these structures, the 4.4′bipyridine molecules act both as a secondary ligand as well as the guest molecules (Figure 2B,C). Compounds III (Co) and IIIa (Mn) also have threedimensional structures, but the structures exhibit subtle differences. The connectivity between the metal ions and the ligands appears to be similar in both the compounds, but the geometry of the metal ions and the twist angle between the two aromatic rings of the bipyridine ligands exhibit differences between the two structures. The asymmetric unit of III consists of 26 non-hydrogen atoms, of which one cobalt atom is crystallographically independent. The Co2+ ions have a distorted trigonal bipyramidal geometry formed by four carboxylate oxygen atoms and a nitrogen atom of the 4,4′-bipyridine. The selected bond distances are listed in Table 5. There is only one OBA anion, which exhibits a bidentate connectivity with the Co2+ cations forming an eight-membered ring, which are connected through their corners forming a one-dimensional chain-like structure. The chains are linked through the OBA anions forming a layer (Figure 3A). The layers are linked by the 4,4′bipyridine molecules giving rise to the three-dimensional structure (Figure 3B). Unlike the structure of II, there are no free bipyridine molecules in this structure. The twist angle between the two pyridine rings of 4,4′-bipyridine was observed to be 0.28°. The asymmetric unit of IIIa consists of two crystallographically independent Mn2+ ions, two OBA anions, and one 4,4′-bipyridine molecule. Though both of the Mn2+ ions are five coordinated, the Mn(1) has a distorted square pyramidal geometry, whereas Mn(2) has a distorted trigonal bipyramidal geometry formed with four carboxylate oxygen atoms and one nitrogen atom of the 4,4′-bipyridine (Figure 4A). The selected bond distances are listed in Table 6. The overall connectivity between the Mn2+ ions and the ligands [OBA and bipyridine] is similar with the connectivity observed between Co2+ and the ligands in III. The presence of two geometrically different Mn2+ ions creates subtle differences in the structure of IIIa (Figure 4B). The twist angle between the two pyridine rings of 4,4′bipyridine was observed to be 8.1°. Transformation Studies. Solid State Transformation Studies on Cobalt Containing Compounds. Solid state transformation studies from compound I to II have been performed by mixing [Co(H2O)2(OBA)], I, and 4,4′-bipyridine in a 1:2 mol ratio followed by grinding the mixture thoroughly

Figure 1. (A) View of the connectivity between the Co2+ ions and the OBA units forming the two-dimensional structure in I. (B) The arrangement of the layers in ABAB... fashion. Dotted lines represent the hydrogen bond interactions.

coordinated water molecules of one layer and the carboxylate oxygens of another layer stabilize the layers three-dimensionally (Figure 1B). The compounds II (Co) and IIa (Mn) are isostructural and isomorphous exhibiting three-dimensionally extended structures with free 4,4′-bipyridine units occupying the channels. The asymmetric unit consists of 25 non-hydrogen atoms, of which one metal atom is crystallographically independent and occupies a special position (2f) with a site multiplicity of 0.5. The metal ions have a octahedral geometry formed by four carboxylate oxygen atoms and two nitrogen atoms from two different 4,4′-bipyridine ligands. The selected bond distances are listed in Table 5 (Co) and Table 6 (Mn). The carboxylate group of the OBA anion exhibits bidentate connectivity with the M2+ ions (M = Co, Mn). The central oxygen atom [O(3)] that connects the two benzene rings of the OBA anions lies on a 2-fold axis. The metal ions are connected through the carboxylate units forming an eight-membered ring. The eightmembered rings are connected through their corners forming a one-dimensional chain, which are further bonded with the OBA anions forming a two-dimensional layer structure (Figure 2A). The two-dimensional layers are connected by the 4,4′bipyridine ligands forming a three-dimensional structure with large one-dimensional channels, which are filled by 4,4′159



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Figure 3. (A) View of the two-dimensional layer structure in III. (B) The connectivity between the layers through 4,4′-bipyridine ligands forming the three-dimensional structure.

coordination around the Co2+ ions of I, two are occupied by the water molecules. During the transformation reactions the water molecules appear to be replaced by the 4,4′-bipyridine molecules to form the three-dimensional structure of II. The possible changes in the coordination environment during the transformation are shown schematically in Figure 6. It is noteworthy that during the solid state transformation studies of I to II, the PXRD patterns did not indicate the presence of any possible intermediate products. It is likely that the removal and the binding of the 4,4-bipyridine ligand with the metal are facile. I was heated at 150 °C for 1 h without the addition of any bipyridine to learn whether there are any changes. Interestingly, the PXRD pattern of the heated sample exhibited similarity with the PXRD pattern for the compound, [Mn(H2O)(OBA)] (Figure 7).7a This observation suggests that [Co(H2O)(OBA)] could be a reactive intermediate in the transformation (Figure S12; see Supporting Information). It is clear that during the transformation the bonding between the carboxylate groups and the Co2+ ions changed. The bidentate carboxylate group of the OBA anions changes the connectivity from nonbridging to bridging mode during the removal of one of the coordinated water molecules giving rise to a distorted square pyramidal

Figure 2. (A) View of the two-dimensional layer structure in II. (B) The three-dimensional structure showing the connectivity between the layers by the 4,4′-bipyridine ligand. The nonbonded 4,4′-bipyridine molecules are shown as space filling model. (C) The zigzag arrangement of the nonbonded 4,4′-bipyridine molecules in the onedimensional channel.

for 1 h. Then the mixture was heated at 150 °C for varying time intervals. The compound [Co(H2O)2(OBA)], I, was found to transform to [Co(bpy)(OBA)]·bpy, II (Figure 5A), on heating for 1 h. The powder X-ray diffraction patterns of the products obtained during different time intervals are presented in Figure 5B. From the PXRD patterns, it is clear that the sample (I) starts to transform in about 15 min, but the transformation appeared to be completed by 1 h. To understand the possible pathway for the structural transition, it is important to note the differences between the two structures (I and II). Out of six 160



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Figure 5. (A) Structure showing a view of the transformation from I to II. Panel at left shows the arrangement of two layers of I (OBA in the two different layers are represented in different colors). Panel at right shows the three-dimensional structure of II with bonded and nonbonded 4,4′-bipyridine molecules. (B) PXRD patterns of the products obtained by solid state transformation by heating I with 4,4′bipyridine at different time intervals: (a) pure I, (b) 4,4′-bipyridine, (c) mixture of I and bipyridine after grinding for 1 h, (d) 15 min, (e) 30 min, (f) 60 min, (g) 120 min, (h) simulated XRD of II. Note the formation of pure phase of II at 60 min.

Figure 4. (A) The distorted square pyramidal [Mn(1)] and the trigonal bipyramidal [Mn(2)] geometry of Mn2+ ions in IIIa. (B) The connectivity between the layers through 4,4′-bipyridine ligands forming the three-dimensional structure.

geometry for the Co2+ ion in the intermediate phase, [Co(H2O)(OBA)]. The removal of the coordinated water molecule and the bonding of 4,4′-bipyridine molecules occur simultaneously. Similar to the transformation of I to II, we have investigated the solid state transformation of [Co(bpy)(OBA)]·bpy, II to [Co(bpy)0.5(OBA)], III, by a simple heating of the sample at 250 °C for 2 h (Figure 8A and Figure S13; see Supporting Information). As described earlier, the coordination environment of Co2+ ions and the nature of the bipyridine molecules exhibit differences in the two structures. The carboxylate oxygen atoms also rearrange during this transformation (Figure 8B). In addition, the nonbonded 4,4′-bipyridine from the channels and half of the bonded 4,4′-bipyridine were removed, resulting in a more condensed three-dimensional structure. The solid-state transformation of II to III did not produce any intermediate phase (Figure 9B). We wanted to explore the possible reversibility of the transformation of III to II as well. To this end, 4,4′-bipyridine was mixed with III in a 2:3 ratio followed by grinding the mixture for different time intervals at room temperature. The PXRD patterns of the ground samples are presented in Figure 9. The PXRD studies show that the compound III transforms partially to compound II by manual grinding (∼50% transformed in 2 h). This study suggests that III is reactive and amenable for transformation. It is likely that the fivecoordination of Co2+ ions makes the Co2+ centers reactive and facilitates the transformation.

Solution Mediated Transformation Studies on Cobalt Containing Compounds. Similar to the solid state transformation studies, I and 4,4′-bipyridine were mixed in a 1:2 ratio along with water in a hydrothermal reaction vessel and heated at two different temperatures, 180 and 110 °C for varying time intervals. The PXRD patterns of the products are presented in Figure 10. The XRD patterns of the products of the reaction at 180 °C indicate that compound I transforms to II in 45 min without any intermediate products (Figure 10A). The reactions carried out at 110 °C, however, indicated the presence of some intermediate products in the time interval between 30 and 240 min. The transformation reaction appears to be complete in 6 h (Figure 10B). In both cases, the final product was found to be II. The above studies suggest that the transformations at 180 °C proceed faster than at 110 °C. A careful examination of the PXRD patterns suggests that one of the intermediates could be [Co(OBA)(H2O)] (Figure 11). To identify other possible intermediates during the transformation, we have carried out theoretical modeling studies by considering the overall structures. The energy minimization studies carried out on the structures clearly indicated the possibility of another closely related structure, [Co(bpy)0.5(OBA)]·0.5bpy (Figure 12A). The crystal structures were geometry optimized30 at constant pressure using the so161



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Figure 6. Schematic of the possible coordination spheres of Co2+ ions during the transformation to II. The coordination sphere (a) and (e) represents the actual observed coordination spheres in I and II. (b), (c) and (d) represent the coordination spheres for the possible intermediates.

Figure 8. (A) Powder XRD patterns of the products obtained on heating II at 250 °C: (a) pure II, (b) 30 min, (c) 60 min, (d) 90 min, (e) 100 min, (f) 110 min, (g) 120 min. The product formed after heating at 250 °C for 2 h is pure phase of III. (B) (a) View of the onedimensional chain in II, (b) The one-dimensional chain in III. Note the difference in the geometry around the Co2+ ions.

ligand giving rise to the three-dimensional structure (Figure 12A). The nonbonded 4,4-bipyridine molecules appear to be half in this structure compared to that observed in II. In addition, it may be noted that the nonbonded bipyridine molecules have a different orientation as well. The various structural parameters of the energy minimized structure of [Co(bpy)0.5(OBA)]·0.5bpy are given in Table 7. A simulated powder X-ray diffraction pattern generated from the theoretically computed structure was compared with the unidentified intermediate phase observed during the solution mediated transformation at 110 °C (Figure 12B). As can be noted, the observed PXRD patterns match very well (Figure 12B). It is likely that the computationally predicted phase, [Co(OBA)(bipy)0.5]·0.5bipy, could indeed be one of the intermediate phases during the transformation from I to II at 110 °C. During the transformation, we have not been able to isolate suitable single crystals to experimentally verify the computationally predicated structure. The formation of such a compound, however, was clearly observed the PXRD patterns of the products of the transformation reactions.

Figure 7. PXRD patterns for (a) compound I, (b) sample heated at 150 °C for 1 h, (c) experimental PXRD pattern of [Mn(H2O)(OBA].

called universal forcefield, uf f,31 treating the metal environment and the organic linker as rigid bodies, while leaving the M−O bonds free to relax and therefore providing the required framework flexibility. The compounds, however, have different chemical compositions, which makes the calculated lattice energies not comparable between the various compounds. In the theoretically predicted structure, the Co2+ ions have a distorted square pyramidal geometry, and the carboxylates have bidentate connectivity with the Co2+ ions similar to that observed in II and [Co(OBA)(H2O)]. The connectivity between Co2+ ions and the OBA anions form a twodimensional layer, which is connected by the 4,4′-bipyridine 162



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Figure 9. PXRD patterns of the products obtained on grinding III and 4,4′-bipyridine: (a) pure III, (b) 30 min, (c) 60 min, (d) 120 min, (e) pure II.

Solution mediated transformation studies from I to III have been performed by heating I with 4,4′-bipyridine in the ratio 2:1 in water at 180 °C. The PXRD of the transformed products obtained in different times are presented in Figure 13. A careful examination of the product PXRD patterns indicated that compound I transformed to compound III within 3 h. During this transformation, compound II appears as the intermediate phase. Transformation studies of compound III to compound II have also been performed by heating III and 4,4′-bipyridine in the ratio 2:3 in water at 110 °C. The PXRD patterns of the transformed products obtained at different time intervals are presented in Figure 14. Compound III transforms to compound II in 150 min. During this transformation, no intermediate phases were obtained. Solid State Transformation Studies on Manganese Containing Compounds. During our investigations on the formation of MOFs of dicarboxylates,7,23 it was observed that manganese forms structures that closely resemble cobalt. As described above, the Mn and Co compounds in the present study also have comparable structures. We wanted to investigate the reactivities of the Mn compounds in the solid state, similar to the studies performed on the Co compounds. Thus, the solid state transformation from [Mn(H2O)2(OBA)], Ia, to [Mn(bpy)(OBA)]·bpy, IIa, and [Mn(bpy)(OBA)]·bpy, IIa, to [Mn(bpy)0.5(OBA)], IIIa, have been investigated employing reaction conditions similar to that used for the corresponding Co compounds. From the PXRD patterns of the product phases, it was observed that [Mn(H2O)2(OBA)], Ia, transformed completely to [Mn(bpy)(OBA)]·bpy, IIa, in 2 h at 150 °C (Figure 15A), without any identifiable intermediates. The solid state transformation of IIa to IIIa was carried out by heating the sample at 200 and 220 °C for varying periods of time (Figure 15B). As can be noted, there were no identifiable intermediate phases during this transformation as well. It may be noted that the octahedral Co2+ ions in II transformed to trigonal bipyramidal geometry, whereas the

Figure 10. PXRD patterns of the products obtained on heating I with 4,4′-bipyridine in water (A) at 180 °C: (a) pure I, (b) 30 min, (c) 45 min, (d) 60 min, and (B) at 110 °C: (a) pure I, (b) 30 min, (c) 60 min, (d) 120 min, (e) 240 min, (f) 360 min. Note the formation of pure phase of II in 45 min at 180 °C and 360 min at 110 °C.

isostructural Mn-compound (IIa) exhibits trigonal bipyramidal as well as square pyramidal geometries for the Mn2+ ions. It is likely that the crystal field stabilization plays an important role in the occurrence of different types of the molecular geometries for the central metal ion. From the crystal field stabilizations energy considerations, the Co2+ ions (d7 system) can take the trigonal bipyramidal geometry, which is the observed one III. On the other-hand, the half filled d-electrons of Mn2+ ions (d5) may not experience any crystal field stabilization energy. Thus, the Mn2+ ions can take any of the other possible geometries driven by the coordination, which would also help in minimizing the unfavorable reorganization of the twist angle of the two pyridine rings of the 4,4′-bipyridine molecules. The twist angle of the two pyridine rings of the 4,4′-bipyridine 163



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Figure 11. (A) Structure of [Co(OBA)(H2O)]. (B) The PXRD patterns of (a) simulated [Mn(OBA)(H2O)], (b) experimental PXRD pattern of the product obtained by heating I with 4,4′-bipyridine in water at 110 °C for 30 min.

molecules are 35.56,23 0.28, and 8.1°, respectively, for 4,4′bipyridine molecules in gas phase, in III and in IIIa. Magnetic Properties. Temperature-dependent magnetic susceptibility measurements for all the three new compounds discovered in the present study (I, II and IIIa) have been performed on powder samples using a SQUID magnetometer (Figure 16). In the case of Co2+ ions (I and II) expectedly the orbital contribution has significant input into the magnetic moment at room temperature.32 The temperature variation of the molar magnetic susceptibility (χM) of I and II under a applied field of 0.1 T are shown in Figure 16, panels A and B, respectively. At room temperature, the observed effective magnetic moments (μeff) are 4.64 μB (I) and 4.72 μB (II), which is the expected magnetic moment value for the noninteracting paramagnetic Co2+ ions with significant orbital contribution, as the spin-only moment of Co2+ ion is 3.87 μB. The 1/χM versus T plots are fitted for a Curie−Weiss behavior in the temperature range 50−300 K (inset of Figure 16A,B), which gave a Weiss constant of −10 and −4.42 K and a Curie constant of 2.86 and 2.95 emu/mol, respectively, for I and II.

Figure 12. (A) The energy minimized three-dimensional structure of [Co(bpy)0.5(OBA)]·0.5bpy. (B) The PXRD patterns: (a) product obtained on heating I with 4,4′-bipyridine in water at 110 °C for 30 min, (b) simulated PXRD pattern of [Co(OBA)(bipy)0.5]·0.5bipy.

Table 7. Crystal Data for [Co{C12H8O(COO)2}{C10H8N2}0.5]·0.5C10H8N2 structure parameter empirical formula crystal system a (Å) c (Å) β (deg) volume (Å3) ρcalc (g cm−3)

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C24H10N2O5Co monoclinic 11.9264 17.0014 80.5991 2481.18 1.259

formula weight space group b (Å) α (deg) γ (deg) Z

470.33 P2/c (No. 13) 12.4033 90.0 90.0 4



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Figure 13. PXRD patterns of the products obtained on heating I with 4,4′-bipyridine in water at 180 °C at different time intervals: (a) pure I, (b) 30 min, (c) 60 min, (d) 100 min, (e) 150 min, (f) 180 min. Note the formation of pure phase of III in 180 min at 180 °C.

Figure 14. PXRD patterns of the products obtained by heating III with 4,4′-bipyridine in water at 110 °C at different time intervals: (a) pure III, (b) 30 min, (c) 60 min, (d) 90 min, (e) 120 min, (f) 150 min. Note the formation of pure phase of III in 150 min at 110 °C.

Figure 15. (A) PXRD patterns of the products obtained by the solid state transformation on heating Ia with 4,4′-bipyridine at different time intervals: (a) pure Ia, (b) 4,4′-bipyridine, (b) 15 min, (c) 30 min, (d) 45 min, (e) 60 min, (f) 120 min, (g) pure IIa. Note that the formation of pure phase of IIa at 120 min. (B) PXRD patterns of the products obtained by heating IIa at 220 and 220 °C for different time intervals: (a) pure IIa, (b) 200 °C/60 min, (c) 200 °C/120 min, (d) 220 °C/30 min, (e) 220 °C/60 min, (f) 220 °C/120 min, (g) simulated XRD pattern of [Mn(bpy)0.5(OBA)]. The product formed after heating at 220 °C for 1 h is pure phase of IIIa.

The small negative Weiss temperature indicates weak antiferromagnetic interactions between the Co2+ ions in I and II.32 The temperature variation of the molar magnetic susceptibility (χM) of IIIa under the applied field of 0.1 T is shown in Figure 16C. At room temperature, the observed effective magnetic moment is 5.7 μB, which is slightly less than the spin only value for the Mn2+ ion (5.92 μB). The 1/χM vs T curve is shown as the inset of Figure 16C. The high

temperature magnetic susceptibility data (100−300 K) can be fitted to the Curie−Weiss behavior with a Weiss constant of −15.4 K and a Curie constant of 4.39 emu/mol. Again, the negative Weiss constant suggests an antiferromagnetic behavior.33 In all three compounds, the metal ions (Co2+ and Mn2+) interact with each other through the carboxylate bridges (O− C−O). In carboxylate bridges (O−C−O), the exchanges generally occur via the 2p orbitals of the oxygen, 2p orbitals 165



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Figure 16. The temperature variation of the molar magnetic susceptibility (χM) (H = 0.1 T). Inset shows the 1/χM vs T plot: (A) I, (B) II, (C) IIIa.

successful synthesis of many inorganic coordination polymers, in recent years, confirm that the crystal engineering principles are universal. The transformation studies described herein may be considered as simple ligand exchange reactions, but one can readily relate to the general guiding principles of crystal engineering. The ligand generally replaces the one already present in the structure with/without a change in the coordination environment of the central metal ion. The coordination changes appear to be brought about by the partial removal of the ligand. The solid state transformation studies suggest that the transformations are facile and proceed without the formation of any intermediate phases. One can readily see the correlation with the investigations on the supramolecular assemblies formed by direct solid state reactions in the organic solid state as well.13,35 The solution route transformations, on the other hand, proceed via intermediate phases. The formation of the intermediates, however, depends on the temperature of the reaction. The

of the carbon, and the metal d orbitals (dM‑pO-pC-pO-dM) with similar symmetries for the participating orbitals. In addition, the bridging modes of the carboxylate oxygens with the transition metal ions also play an important role. The most commonly observed bridging modes of the carbxylate oxygen are syn-syn, syn-anti, and anti-anti arrangements. Among these, the syn-syn and anti-anti bridging modes, generally, exhibit weak antiferromagnetic interaction and syn-anti mode exhibits weak ferromagnetic corrlations.34 In the present compounds (I, II, and IIIa), all the carboxylate bridges are more or less syn-syn conformations resulting in weak antiferromagnetic interactions, which is the observed behavior.

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SUMMARY AND CONCLUSIONS The principles of crystal engineering as well as the idea of synthons have become common in organic solid state chemistry/supramolecular chemistry mainly due to the inspiring work of Desiraju.13 The design approaches and 166



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(8) Li, H.; Eddaoudi, M.; O’Keeffe, M.; Yaghi, O. M. Nature 1999, 402, 276. (9) Burnett, B. J.; Choe, W. Dalton Trans. 2012, 41, 3889. (10) (a) Ayi, A. A.; Choudhury, A.; Natarajan, S.; Neeraj, S.; Rao, C. N. R. J. Mater. Chem. 2001, 11, 1181. (b) Natarajan, S.; Wullen, L. V.; Klein, W.; Jansen, M. Inorg. Chem. 2003, 42, 6265. (c) Choudhury, A.; Neeraj, S.; Natarajan, S.; Rao, C. N. R. J. Mater. Chem. 2001, 11, 1537. (d) Natarajan, S. Chem. Commun. 2002, 780. (11) Downer-Riley, N. K.; Jackson, Y. A. Annu. Rep. Prog. Chem. Sect. B 2011, 107, 157. (12) (a) Kitaura, T.; Iwahori, F.; Matsuda, R.; Kitagawa, S.; Kubota, Y.; Takata, M.; Kobayashi, T. C. Inorg. Chem. 2004, 43, 6522. (b) Chen, Z.; Xiang, S.; Zhao, D.; Chen, B. Cryst. Growth. Des. 2009, 9, 5293. (c) Sun, J.; Zhou, Fang, Q.; Chen, Z.; Weng, L.; Zhu, G.; Qiu, S.; Zhao, D. Inorg. Chem. 2006, 45, 8677. (d) Park, H. J.; Cheon, Y. E.; Suh, M. P. Chem.Eur. J. 2010, 16, 11662. (e) Li, J. R.; Timmons, D. J.; Zhou, H. C. J. Am. Chem. Soc. 2009, 131, 6368. (f) Wang, H. N.; Meng, X.; Yang, G. S.; Wang, X. L.; Shao, K. Z.; Su, Z. M.; Wang, C. G. Chem. Commun. 2011, 47, 7128. (f) Burnett, B. J.; Barron, P. M.; Hu, C.; Choe, W. J. Am. Chem. Soc. 2011, 133, 9984. (g) Wang, X. L.; Qin, C.; Wu, S. X.; Shao, K. Z.; Lan, Y. Q.; Wang, S.; Zhu, D. X.; Su, Z. M.; Wang, B. E. Angew. Chem., Int. Ed. 2009, 48, 5291. (13) Desiraju, G. R. Angew. Chem., Int. Ed. 2007, 46, 8342. (14) Serre, C.; Mellot-Draznieks, C.; Surble, S.; Audebrand, N.; Filinchuk, Y.; Ferey, G. Science 2007, 315, 1828. (15) Zhang, J. P.; Lin, Y. Y.; Zhang, W. X.; Chen, X. M. J. Am. Chem. Soc. 2005, 127, 14162. (16) (a) Hanson, K.; Calin, N.; Bugaris, D.; Scancella, M.; Sevov, S. C. J. Am. Chem. Soc. 2004, 126, 10502. (b) Jia, J.; Lin, X.; Blake, A. J.; Champness, N. R.; Hubberstey, P.; Shao, L.; Walker, G.; Wilson, C.; Schröder, M. Inorg. Chem. 2006, 45, 8838. (17) (a) Sarma, D.; Ramanujachary, K. V.; Lofland, S. E.; Magdaleno, T.; Natarajan, S. Inorg. Chem. 2009, 48, 11660. (b) Aslani, A.; Morsali, A. Chem. Commun. 2008, 3402. (c) Rather, B.; Zaworotko, M. J. Chem. Commun. 2003, 830. (d) Liu, Y. H.; Tsai, H. L.; Lu, Y. L.; Wen, Y. S.; Wang, J. C.; Li, K. L. Inorg. Chem. 2001, 40, 6426. (e) Lu, J. Y.; Babb, A. M. Chem. Commun. 2002, 1340. (f) Cussen, E. J.; Claridge, J. B.; Rosseinsky, M. J.; Kepert, C. J. J. Am. Chem. Soc. 2002, 124, 9574. (g) Ghosh, S. K.; Zhang, J. P.; Kitagawa, S. Angew. Chem., Int. Ed. 2007, 46, 7965. (h) Bradshaw, D.; Warren, J. E.; Rosseinsky, M. J. Science 2007, 315, 977. (18) Mandal, S.; Natarajan, S. Inorg. Chem. 2008, 47, 5304. (19) Rao, V. K.; Chakrabarti, S.; Natarajan, S. Inorg. Chem. 2007, 46, 10781. (20) Dan, M.; Rao, C. N. R. Angew. Chem., Int. Ed. 2006, 45, 281. (21) Ranford, J. D.; Vittal, J. J.; Wu, D. Angew. Chem., Int. Ed. 1998, 37, 1114. (22) (a) Garay, A. L.; Pichon, A.; James, S. L. Chem. Soc. Rev. 2007, 36, 846. (b) Adams, C. J.; Colquhoun, H. M.; Crawford, P. C.; Lusi, M.; Orpen, A. G. Angew. Chem., Int. Ed. 2007, 46, 1124. (23) Mahata, P.; Madras, G.; Natarajan, S. J. Phys. Chem B 2006, 110, 13759. (24) Sun, C. Y.; Gao, S.; Jin, L. P. Eur. J. Inorg. Chem. 2006, 2411. (25) SMART (V 5.628), SAINT (V 6.45a), XPREP, SHELXTL; Bruker AXS Inc.: Madison, Wisconsin, USA, 2004. (26) Sheldrick, G. M. Siemens Area Correction Absorption Correction Program; University of Göttingen: Göttingen, Germany, 1994. (27) Sheldrick, G. M. SHELXL-97 Program for Crystal Structure Solution and Refinement; University of Göttingen, Göttingen, Germany, 1997. (28) Farrugia, J. L. WinGx suite for small-molecule single crystal crystallography. J. Appl. Crystallogr. 1999, 32, 837. (29) Bail, A.; Le.; Duroy, H.; Fourquet, J. L. Mater. Res. Bull. 1998, 23, 447. (30) Materials Studio Suite of Software; Accelrys: San Diego, CA. (31) Rappé, A. K.; Casewit, C. J.; Colwell, K. S.; Goddard, W. A., III; Skiff, W. M. J. Am. Chem. Soc. 1992, 114, 10024. (32) Goodenough, J. B. Magnetism and the Chemical Bond; Interscience Publishers: New York, 1996.

intermediates as well as the transformed phases appear to be related to each other. It is likely that the subtle variations in the crystal-field stabilization energies between the various phases could be important. It is clear that further work is required to probe and propose a more general mechanism for the formation of the inorganic−organic coordination compounds. While doing so, it is also important to validate the guiding principles of crystal engineering and its applicability toward inorganic−organic hybrid compounds. It is hoped that such investigations would be carried out by many researchers in the future so that one can evolve a generalized understanding of the formation of compounds with extended structures.

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ASSOCIATED CONTENT

* Supporting Information S

X-ray crystallographic files (for I, II, and IIIa) in CIF format, bond angle tables, powder X-ray diffraction patterns, IR, TGA and some additional figures. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (S.N.). E-mail: partha. [email protected] (P.M.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS P.M. thanks Department of Science and Technology (DST), Government of India, for the award of Fast Track Scheme for Young Scientists and Thapar University for Seed Grant Scheme. S.N. thanks the Department of Science and Technology (DST), Government of India, for the award of the RAMANNA fellowship and a research grant.

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DEDICATION Dedicated to Professor G. R. Desiraju on his 60th birthday. REFERENCES

(1) (a) Special Issue on MOF. Chem. Rev. 2012, 112, 673−1268. (b) Special Issue on MOF. Chem. Soc. Rev. 2009, 38, 1213−1504. (c) Spcial Issue on MOF. Eur. J. Inorg. Chem. 2010, 3683−3874. (2) (a) Mahata, P.; Natarajan, S. Chem. Soc. Rev. 2009, 38, 2304. (b) Banerjee, R.; Phan, A.; Wang, B.; Knobler, C.; Furukawa, H.; O’Keeffe, M.; Yaghi, O. M. Science 2008, 319, 939. (3) (a) Maspoch, D.; Ruiz-Molina, D.; Veciana, J. Chem. Soc. Rev. 2007, 36, 770. (b) Kitagawa, S.; Kitaura, R.; Noro, S. Angew. Chem., Int. Ed. 2004, 43, 2334. (4) (a) Stock, N.; Biswas, S. Chem. Rev. 2012, 112, 933. (b) Natarajan, S.; Mahata, P.; Sarma, D. J. Chem. Sci. 2012, 124, 339. (5) (a) Kim, H.; Das, S.; Kim, M. G.; Dybtsev, D. N.; Kim, Y.; Kim, K. Inorg. Chem. 2011, 50, 3691. (b) Maniam, P.; Stock, N. Inorg. Chem. 2011, 50, 5085. (c) Ahnfeldt, T.; Moellmer, J.; Guillerm, V.; Staudt, R.; Serre, C.; Stock, N. Chem.Eur. J. 2011, 17, 6462. (d) Lan, Y. Q.; Jiang, H. L.; Li, S. L.; Xu, Q. Inorg. Chem. 2012, 51, 7484. (e) Yaghi, O. M.; O’Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M. Nature 2003, 423, 705. (f) Rao, C. N. R.; Natarajan, S.; Vaidhyanathan, R. Angew. Chem., Int. Ed. 2004, 43, 1466. (g) Foster, P. M.; Cheetham, A. K. Angew. Chem., Int. Ed. 2002, 41, 457. (6) Foster, P. M.; Burbank, A. R.; Livage, C.; Ferey, G.; Cheetham, A. K. Chem. Commun. 2004, 368. (7) (a) Mahata, P.; Sundaresan, A.; Natarajan, S. Chem. Commun. 2007, 4471. (b) Mahata, P.; Prabu, M.; Natarajan, S. Inorg. Chem. 2008, 47, 8451. 167



Article

(33) (a) Tynan, E.; Jensen, P.; Kelly, N. R.; Kruger, P. E.; Lees, A. C.; Moubaraki, B.; Murray, K. S. Dalton Trans. 2004, 3440. (b) Yuan, Y. P.; Wang, R. Y.; Kong, D. Y.; Mao, J. G.; Clearfield, A. J. Solid State Chem. 2005, 178, 2030. (34) Mahata, P.; Sarma, D.; Natarajan, S. J. Chem. Sci. 2010, 122, 19. (35) (a) Aakeroy, C. R.; Champness, N. R.; Janiak, C. CrystEngComm 2010, 12, 22. (b) Trask, A. V.; Jones, W. Top. Curr. Chem. 2005, 254, 41.

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