Single-Crystal-to-Single-Crystal Breathing and Guest Exchange in

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Single-Crystal-to-Single-Crystal Breathing and Guest Exchange in CoII Metal-Organic Freameworks Sumi Ganguly, Sandip Mukherjee, and Parthasarathi Dastidar Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.6b00805 • Publication Date (Web): 15 Jul 2016 Downloaded from http://pubs.acs.org on July 16, 2016

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Crystal Growth & Design

Single-Crystal-to-Single-Crystal Breathing and Guest Exchange in CoII Metal-Organic Frameworks Sumi Ganguly†, Sandip Mukherjee‡ and Parthasarathi Dastidar†* †Department of Organic Chemistry, Indian Association for the Cultivation of Science, Raja S. C. Mullick Road, Kolkata700032, India. ‡Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Raja S. C. Mullick Road, Kolkata700032, India. Supporting Information Placeholder Keywords: Metal-Organic Framework (MOFs) ∙ Breathing MOFs ∙ Single-Crystal to Single-Crystal (SCSC) ∙ Supramolecular chemistry ∙ Magnetic Properties ABSTRACT: Single-crystal-to-single-crystal (SCSC) breathing and guest exchange properties of a series of CoII metal-organic frameworks (MOFs) are reported. A new bis-pyridyl-bis-amide ligand namely 4,4ˊ-oxybis(N-(pyridine-4-yl)benzamide) (LP1) produced two MOFs namely [{Co(LP1)(IPA)}(DMF)2(H2O)]∞ (1) and [{Co2(LP1)2(TPA)2}(DMF)4]∞ (2) under solvothermal conditions (IPA = isophthalate, TPA = terephthlate). While 1 showed excellent SCSC breathing responsive to both heat and guests (acetone, DMSO, MeOH, DEF), 2 displayed no breathing under similar conditions. However, it showed excellent SCSC guests (acetone, DMSO) exchange properties. Single crystal structural analyses revealed that the conformational flexibility of the ligand LP1 played a crucial role both in breathing in 1 and guest exchange in 2. The compound 1 also displayed heat responsive magnetic changes.

the structural changes at the atomic resolution is not so common.

INTRODUCTION

80-91

With the first structurally characterized report of coordination polymers (CPs) and the rapid advancement of single crystal X-ray diffractometry, research on CPs or later defined as metal-organic frameworks (MOFs) gained tremendous impetus. 1-9 The ease of synthesis (usually crystallization), atomic level insights into the structures via X-ray crystallography, relatively easy access to structural modulation by synthetic manipulation of the organic linker and various potential applications make this class of compounds an attractive research target. 10-21 Porous MOFs have attracted remarkable attention because of their potential applications such as in gas adsorption, 22-27 catalysis, 28-33 post-synthetic modification, 34-36 sensing, 37-41 separation 42-48 etc. These porous MOFs are broadly classified into three categories i.e. 1st, 2nd and 3rd generation.49-50While the crystalline network of 1st generation collapses upon removal of guest molecules, the 2nd generation is structurally stable even after removal of the guests. However, the crystalline network in 2nd generation is highly rigid and does not offer any opportunity to tune the porosity. To overcome these problems, efforts are being invested in developing MOFs which are defined as breathing networks i.e. flexible network that allows contraction or expansion upon external stimuli such as heat, light, solvents, vapours etc. Such breathing MOFs are known as 3rd generation.51-65 Breathing is a cooperative effect of both the inorganic node and organic ligand; during breathing, MOFs may undergo several structural changes like formation and disruption of metal-ligand coordination bonds, sub network displacement, sliding of layers etc. 66-79 While the ligand should be conformationally flexible, the metal center should be adaptable to various coordination geometries in order to adjust to the structural changes during breathing. However, breathing of MOFs via single-crystal-tosingle-crystal (SCSC) fashion that allows direct visualization of

In the present study, we set out to develop a MOF based breathing system wherein guest is the stimuli. It is well known that counter anions often occupy the pores in MOF thereby reducing the possibility of guest occlusion. On the other hand, if the counter anion itself is a coordinating ligand, such situation may be avoided. In case of mixed ligand system, effective pore within the MOF may be generated. Keeping these points in mind, we selected the ligand namely 4,4ˊ-oxybis(N-(pyridine-4-yl)benzamide) (LP1), dicarboxylate coligands (isophthalate/terephthalate) and Co(NO3)2 to generate MOFs as potential breathing system; LP1 is flexible and also equipped with hydrogen bonding functionality (amide) which might encourage guest occlusion via hydrogen bonding interactions. The carboxylates are expected to coordinate the metal centers thereby reducing the possibility of occupying the pores within the framework. CoII is known to adapt various coordination geometries because of the relatively low energy barrier among the various coordination geometries.92-93 Reactions of LP1 and Co(NO3)2 with isophthalate and terephthalate in separate experiments under solvothermal conditions resulted in two crystalline compounds namely 1 and 2 (Scheme 1). SXRD analyses revealed that both the compounds were MOFs having formulae [{Co(LP1)(IPA)}(DMF)2(H2O)]∞ (1) and [{Co2(LP1)2(TPA)2}(DMF)4]∞ (2). Further studies established that compound 1 was an excellent breathing MOF responsive to various guest molecules whereas compound 2 displayed interpenetrated 3D framework showing the capability of rapid guest exchange with no breathing under similar guest stimuli. In both the cases, such process took place via SCSC fashion. DFT calculations revealed that the ligand LP1 was indeed flexible facilitating

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Scheme 1. Preparation of MOFs from ligand LP1 and Co(NO3)2.

such structural changes during breathing. Compound 1 showed interesting magnetic properties under heating as well.

Results and Discussion. Single crystals of 1 and 2 suitable for SXRD studies were harvested under solvothermal conditions (see experimental section for details) and subjected to SXRD analyses (Table 1).

Structural Description. Crystal Structure of [{Co(LP1)(IPA)}(DMF)2(H2O)]∞ (1). Compound 1 crystallized in the centrosymmetric triclinic space group P1. The asymmetric unit contained one CoII centre, one ligand LP1, one isophthalate, and two lattice occluded DMF and one water molecules. The ligand LP1 was found to be significantly nonplanar displaying relevant dihedral angles deviated from 0˚ (Table 2). The relative orientation of the amide functionalities was syn. The metal center CoII was coordinated by four O atoms of three isophthalates and two N atoms of LP1 displaying slightly distorted octahedral geometry. The equatorial positions were occupied by the carboxylate O atoms whereas the axial positions were coordinated by pyridyl N atoms. The supramolecular architecture of 1 may best be described as a 2D network wherein a 1D columnar network involving CoII and the isophthalates was threaded by the linear bis-pyridyl ligand LP1 in an extended fashion resulting in an overall 2D network. The lattice occluded water formed hydrogen bonded trimeric cluster wherein the water molecule held two crystallographically independent DMF molecules via O-H…O hydrogen bonding. Such hydrogen bonded cluster was further stabilized within the network by hydrogen bonding interactions with the adjacent amide moieties involving N-H…O interactions. The 2D networks were further packed in parallel fashion, the interstitial space of which was occupied by the DMF molecules whereas the water molecules were located within the 2D network. Topological analyses have been carried out by considering dinuclear CoII units as nodes. The results revealed that it was a 2D net of a uninodal 4-c sql topology with a point symbol {44.62} (Figure 1).94-98 Crystal structure of [{Co2(LP1)2(TPA)2}(DMF)4]∞ (2). Compound 2 also crystallized in the centrosymmetric triclinic space group P1. The asymmetric unit was comprised of two LP1, two CoII metal centers, four half occupied terepthalates (located around center of inversion), four lattice occluded DMF molecules. Both the ligands displayed syn conformation with respect to the

amide moieties and were significantly nonplanar (Table 2). Both CoII metal centers showed slightly distorted octahedral geometry; the equatorial positions were occupied by carboxylate O atoms coming from three terephthalates whereas the axial sites were coordinated by pyridyl N atoms of LP1. The crystal structure may best be described as a 2-fold interpenetrated 3D network; the terephthalate ions formed a 2D sheet via extended coordination with the adjacent metal centers and the linear bis-pyridyl ligand LP1 coordinated further the 2D sheets resulting in a 3D network. Two such similar networks were further interpenetrated presumably to occupy the huge space generated within each 3D network. Out of the four lattice occluded DMF molecules, two were found to form hydrogen bonding via N-H…O interactions with the amide functionality whereas the other two did not participate in hydrogen bonding interactions. The two independent 3D nets were mutually interpenetrating forming 6-c pcu-c topology with point symbol {412.63} (Figure 2); like in compound 1, dinuclear CoII units were considered as nodes. Breathing studies. Thus the foregoing discussions revealed that both the compounds 1 and 2 were lattice occluded MOFs. While 1 was a 2D network, compound 2 displayed an interpenetrated 3D net. Thus, both the compounds are suitable candidates for breathing studies as argued in the previous section (vide supra). To identify the temperature at which desolvation took place, the compunds were subjected to thermogravimetric analysis (TGA). The TGA profile of 1 indicated that the desolvation of the lattice occluded solvents involved two steps; while the water molecules were ejected from the network at ∼100°C, the high boiling DMF molecules were desolvated at higher temperature (∼170˚C). After the loss of both the solvent molecules the TGA profile does not show any further weight loss up to ∼390°C beyond which it appeared to have been degraded (Figure S12 in Supporting Information). However, in the absence of powder X-ray diffraction (PXRD) at such a high temperature, one cannot rule out the possibility of any further phase transition in 1. On the other hand, compound 2 displayed a single step weight loss at ~220˚C indicating desolvation of all the DMF molecules. Further heating established that compound 2 was stable up to ~ 400˚C (Figure S18 in Supporting Information). Variable temperature PXRD studies of compound 1 revealed that there was no phase transition after the removal of water molecules at ~100˚C. However, the PXRD patterns drastically changed soon


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Figure 1. Crystal structure illustration of compound 1: (a) 2D network; (b) coordination geometry of the central metal ion; (c) topological representation displaying 2D net of a uninodal 4-c sql topology; (d) metal-isophthalate dinuclear unit.

Figure. 2. Crystal structure illustration of compound 2: (a) 2-fold interpenetration of 3D network displaying occluded DMF (in space filling model); (b) Coordination geometry of CoII; (c) metal terephthalate cluster; (d) topological representation of 6-c pcu-c topolgy.

after the removal of DMF molecules at ~170˚C (displaying a color change of the sample from pink to purple) indicating the formation of a new phase and such phase remained almost intact up to ~230˚C (Figure 3a). These data encouraged us to study further the breathing behaviour of 1 by hot-stage microscopy with a single crystal (Figure 3b). At 170°C under atmospheric pressure the single crystals of 1 start to crack slowly with a subsequent change in transparency. A small fragment of the heat-treated (170˚C) crystal of 1 (designated as 1a) was then subjected to SXRD analysis (Table 1). The daughter compound 1a displayed identical space group (P1) with that of its mother crystal 1 and it was devoid of any occluded solvents. All the crystallographic axes were significantly reduced resulting in ~1.4 times shrinkage of the cell volume (1885.23 to 1335.59 Å3). PLATON analyses also supported this observation; while 1a had no solvent accessible void volume, the mother compound 1 possessed 31.7% solvent accessible void volume. Most interestingly, the bis-pyridyl ligand changed its conformation from syn (in 1) to anti with respect to the amide functionality. The metal center was transformed from distorted octahedral (in 1) to distorted (5 = 0.57)99-100 trigonal bipyramidal geometry wherein the equatorial positions were occupied by three O atoms of three isophthalate whereas the axial cites were coordinated by the N

atoms of LP1. The coordination network in 1a may be best described as a 2D sheet architecture (similar to what has been observed in its mother compound 1) wherein 1D columnar networks arising due to the extended coordination of CoII with isophthalates were threaded by the bidentate bis-pyridyl ligand LP1 resulting in an overall 2D network (Figure 4). Such 2D sheets were further packed in parallel fashion sustained by inter-sheet hydrogen bonding involving the amide N-H and carboxylate O atoms. Removal of guests at ~170˚C presumably drove the ligand LP1 to adapt anti conformation to get an access to hydrogen bonding interactions with the isophthalate O coming from the neighbouring 2D sheet (Figure S40 in Supporting Information). TGA profile of 1a revealed that it was as stable as 1 i.e. stable up to 390°C with no weight loss (Figure S13 in Supporting Information). Further, it was observed that the transformation of 1 to 1a was reversible; when the crystals of 1a were soaked in DMF/water (3:1), it readily picked up the solvent molecules resulting in the crystals of 1 as established by PXRD (Figure S28 in Supporting Information). Thus, the data described thus far clearly indicate that 1 and 1a are indeed a true breathing system.



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0.53). Interestingly, the occluded solvents (DMF/water in 1) were replaced with only water in 1d. PXRD data indicated that such solvent exchange was mutually reversible among the mother crystal 1 and its daughters (1b, 1c and 1d) (Figure S28-S31 in Supporting Information). TGA data also supported these observations (Figure S14-S17 in Supporting Information).

Figure 4. Crystal structure illustration of 1a: (a) 2D network displaying anti conformation of LP1; (b) trigonal bipyramidal geometry of CoII.

Figure 3. (a) Variable temperature PXRD patterns of compound 1. (b) Optical photograph of a single crystal of 1 under hot-stage microscope displaying a transition from transparent to translucent at higher temperature (heating rate: 10˚C per minute). Since the mother compound 1 displayed appreciable solvent accessible void volume (vide supra) which was further supported by N2 gas adsorption isotherm (Figure S42 in Supporting Information), we thought it was worthwhile to study the breathing of 1 under various solvent stimuli (Figure 5a). Thus, the single crystals of 1 were soaked in various solvents that include aromatic (benzene, toluene, xylenes, halo-benzenes and nitro-benzene) and nonaromatic polar solvents (acetone, DMSO, MeOH, DEF and water). In the cases of aromatic solvents and water, the crystals of 1 became opaque i.e. the daughter compound was crystalline but those crystals were not of SXRD quality. Therefore no SXRD data could be collected for these daughter products. However, SXRD data revealed that 1 produced daughter crystals from acetone, DMSO, MeOH, DEF in separate experiments (designated as 1b, 1c, 1d and 1e, respectively) (Table 1, Figure S38 in Supporting Information). Structural analyses revealed that both 1b and 1c were isostructural with their mother crystal 1 displaying near identical cell dimensions and identical space group (P1) except that in these crystals the lattice occluded solvents were acetone (in 1b) and DMSO/water (in 1c) (Figure 5b, c). These data indicate that breathing is insignificant in these cases. However, in the case of 1d (i.e. MeOH as solvent stimulus), significant breathing was observed; cell volume changed from 1885.23 to 1544.77 Å3 displaying ~1.2 times shrinkage. Ligand (LP1) conformation was transformed from syn to anti and the metal center underwent a transition from octahedral to distorted trigonal bipyramidal (5 =

On the other hand, DEF soaked crystals of 1 (i.e. 1e) was transformed to a C-centered monoclinic crystal having the centrosymmetric space group C2/c. The asymmetric unit contained a highly nonplanar LP1 displaying anti conformation with respect to amide moiety, one CoII metal center, one isophthalate, one lattice occluded DEF and one disordered water molecules. The CoII metal center displayed distorted octahedral geometry wherein the equatorial sites were occupied with four O atoms coming from three isophalates and the axial positions were occupied with N atoms of LP1 resulting in a 3D net of a uninodal 4-c cds topology (Figure 5e and Figure S37 in Supporting Information). The lattice occluded DEF was found to be involved in hydrogen bonding with the amide via N-H…O interactions and the disordered water molecules were just occluded within the void stabilized by van der Waals interactions. Solvent exchange experiments revealed that 1e was not reversible with its mother crystal 1; therefore it is not a case of breathing but a transformation from 2D to 3D structure. PXRD patterns of the soaked crystals of 1e were drastically different than that of the mother (1) indicating that new crystalline phases were generated during soaking (Figure S35 in Supporting Information). However, single crystal structures of this new crystalline phase could not be determined because of the poor quality SXRD data. It is well known that 3D interpenetrated coordination networks are scarcely reported to be breathing crystals as it requires energy expensive breaking and reformation of metal-ligand coordination bond.101-103 Nevertheless, the crystals of 2 were subjected to similar breathing studies. Temperature dependent PXRD experiments on microcrystalline powder sample of 2 revealed that the patterns essentially remained near identical till 180˚C and above that temperature, there seemed to be structural change with significant loss of crystalinity (Figure 6a). Hot stage microscopy of a welldeveloped single crystal of 2 revealed that the crystal started to become opaque above 180˚C and the SXRD data collected from such heat treated crystal of 2 (220˚C) was not indexable indicating poor crystallinity as also observed in PXRD studies (Figure 6b). However, crystals of 2 were subjected to breathing studies with the same set of guests as applied in the case of 1 and suitable Xray quality crystals were obtained only in the cases of acetone and DMSO resulting in daughter compounds 2a and 2b, respectively


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Figure. 5. Breathing studies of 1 under various solvent stimuli; (a) graphical representation of solvent accessible void volume in compound 1 (probe diameter 1.2 Å.); crystal structure illustrations of (b) 1b displaying lattice occluded acetone; (c) 1c showing lattice occluded DMSO, (d) 1d with water as lattice colluded solvent (e) 1e with DEF as lattice occluded solvents.

(Figure S39 in Supporting Information). SXRD analyses revealed that the space group (P1) remained unchanged in the daughter compounds (Table 1). Close inspection of the crystal structures of both the daughter compounds 2a and 2b revealed that they were essentially isostructural with the mother compound 2 i.e. the similar 3D interpenetrated network as observed in 2 was present. There seemed to be just guest exchange without any significant change in the overall network structures. The apparent shrinkage of the cell volume of the daughter compounds (2a and 2b) compared to their mother compound was because of the Zʹ differences (Zʹ = 2 for 2 whereas Zʹ = 1 for 2a and 2b). Closer look at the supramolecular architecture of 2 revealed that the solvent (DMF) molecules were located within the coordination network in the confined voids and there were no continuous open channels. However, the crystals of 2 seemed to exchange solvents (DMSO, acetone) reversibly to produce the daughter crystals and the guests were mutually exchangeable between the daughter crystals as well (Figure S32-34 in Supporting Information). This observation lead us to investigate the system further in order to gain insights into underlying mechanism of such solvent exchange phenomenon.

Thus, the crystals of 2 soaked in acetone and DMSO (in separate experiments) after 10 hrs were subjected to SXRD analyses. The soaked crystals (designated as 2c) in both the cases turned out to be identical displaying a different crystalline phase (monoclinic, space group P21/n) from that of their mother crystal 2 (triclinic P1). The asymmetric unit of 2c contained one molecule of LP1, one CoII metal center, two half occupied terephthalate and two disordered lattice occluded DMF molecules. Overall the crystal structure of this intermediate was isostructural to the mother crystal 2 displaying similar 2-fold 3D interpenetrated network wherein the guests (DMF) were held within the confined voids via N-H…O hydrogen bonding involving the amide backbone of LP1. “To further support the structural changes associated with the SCSC transformation of compound 1 and 2 to various daughter compounds (1a, 1b, 1c, 1d, 1e and 2a , 2b), IR-spectra were recorded (Figure S22-S24 in the supporting information). However, it was quite difficult to assign the IR bands associated with the



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functionalities of the solvents (carbonyl of acetone, DMF, DEF and sulfoxide of DMSO) due to overlap of peaks associated with the MOFs. However, the difference of IR spectra was quite evident (Figure S22-S24 in the supporting information) which indicated possible changes of the daughter compounds during the removal and re-adsorption of solvents.” It may be mentioned here that in all the SXRD experiments performed in guest-induced breathing studies, bulk single crystals were used for soaking. SXRD data were collected by selecting a single crystal from the soaked crystals in each case which did not rule out the possibility of dissolution and recrystallization thereby

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answer to this question lies in the tendency of compound 2 and its daughters (2a and 2b) including the intermediate (2c) to form 3D interpenetrated network which scarcely displays breathing. The main difference between these two structures (i.e. 1 and 2) is in the co-ligand; while terephthalate in 2 has linear ligating topology, isophthalate in 1 displays angular coordinating sites. As a result, a 3D octahedral network was formed in 2 because of the extended coordination by the linear bispyridyl ligand LP1 and terephthalate generating pores of 10.22×10.78Å, 25.02×14.90Å, 25.02×10.24Å for three unique faces of the octahedral network (Figure S41 in Supporting information). Such large opening of the faces facilitated the observed 2-fold interpenetration of the octahedral network in 2. On the other hand, isophthalate in 1 being angularly disposed for coordination was not able to form such 3D octahedral network, instead leading to a 2D network having no effective pore for such network interpenetration. The conformational flexibility of bis-pyridyl ligand LP1 seemed to play a crucial role in breathing in 1 and guest exchange in 2. DFT calculations revealed that the energy barrier of syn and anti conformations of LP1 with respect to the amide functionality was relatively small allowing conformation change under suitable conditions (Figure S27 and Table S5 in Supporting Information). We were fortunate enough to have been able to crystallize LP1 as a free ligand (Table S6, Figure S1). It is interesting to note that it displayed anti conformation with significant molecular nonplanairty. Table 2 records various dihedral angles involving the aromatic backbone and amide functionality and conformation of LP1 in the free ligand as well as its metal coordinated states. It is quite clear from Table 2 that LP1 is quite flexible in 1 and its daughter crystals (1a-e) displaying large differences in the dihedral angles and conformation whereas in case of 2 and its daughters, such differences are not that much. Interestingly, in these cases, the conformation of LP1 is locked at syn displaying relatively less flexibility of LP1 which, we believe, is the consequence of the 3D interpenetrated network. It may be noted that in the case of the intermediate 2c, the terminal dihedral angles (d1 and d3) vary quite a lot from those of the mother crystal 2 plausibly to allow smooth solvent exchange.

Figure 6. (a) Variable temperature PXRD pattern of compound 2; (a) optical photograph of a single crystal of 2 under hot-stage microscope displaying a transition from transparent to opaque crystal. casting a doubt over its SCSC transformation. In order to establish that these transformations were indeed via SCSC, we also collected SXRD data set by soaking one single crystal in each case for all the relevant cases (1b, 1c, 1d, 1e, 2a, 2b). The corresponding structures turned out to be identical with that of the crystals selected in the bulk studies supporting the SCSC transformation in such guest exchange. The optical images of the soaked single crystals of 1b, 1c, 1d, 1e, 2a, 2b are provided in the supporting information (Figure S38, S39). To gain further insights as to why compound 1 is an excellent breathing system whereas compound 2 shows no breathing, we further analyzed the structures in more detail. We believe that the

It may be mentioned that the heat and guest responsive breathing of 1 is one of the scarce examples of SCSC breathing in MOFs. To the best of our knowledge, prior to this report, there are handful of reports that describe breathing of MOFs in SCSC fashion.8091 The volume ratio (Vinitial /Vfinal) in 1 and its daughters (1a-d) is ~1.02-1.39, which is well within the range of the reported SCSC breathing MOFs.80-91 The mutual reversibility of 1 and its daughters (1⇌1a⇌1b⇌1c⇌1d) is also a rare phenomenon in breathing MOFs. Magnetic Studies. MOFs which exhibit reversible SCSC transformations associated with magnetic property change, are very important for applications in magnetic sensors, cooling devices and multifunctional materials.104-108 The structural transitions achieved due to SCSC transformations may lead to reversible changes in the magnetic properties of the flexible frameworks. Herein we reported a reversible SCSC transformation in 1 and 1a upon desolvation. Guest removal from mother crystals of 1 causes ~ 1.4 times shrinkage of the framework which is accompanied by changes in the coordination geometry of central metal ion. When both these two compounds are subjected to magnetic studies difference between their magnetic behaviour is observed.


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Table 1. Crystallographic data and refinement parameters for compounds 1, 2 and their daughter crystals.

CCDC Number

1 1413878

Empirical formula

C38H38CoN6O10 C32H22CoN4O7 C38H34CoN4O9

C36H36CoN4O10S2 C32H26CoN4O9

C74H66Co2N10O17

Formula weight

797.67

807.74

669.5017

1485.23

0.22×0.17×0.10 0.18×0.12×0.10 0.20×0.16×0.07

0.25×0.18×0.10

0.28×0.08×0.18

0.20×0.16×0.07

Triclinic P1

Triclinic P1

Triclinic P1

Triclinic P1

Monoclinic

Space group

Triclinic P1

C2/c

a/Å

10.0895(11)

9.879(9)

10.071(11)

10.126(3)

10.159(2)

17.0207(11)

b/Å

14.0751(16)

11.348(10)

13.132(15)

13.621(3)

12.617(3)

10.7350(6)

Crystal size/mm Crystal system

1a 1413879 633.47

1b 1413880 749.62

1c 1413881

1d 1413882

1e 1413883

c/Å

15.5196(18)

13.386(12)

15.598(18)

15.657(4)

14.438(3)

39.399(3)

α/°

114.925(6)

89.370(15)

107.133(10)

110.175(2)

96.996(14)

90

β/°

99.246(6)

76.595(14)

108.784(10)

108.302(2)

108.948(14)

100.719(4)

γ/°

101.296(6)

68.697(14)

96.932(10)

97.225(3)

112.954(12)

90

Volume/Å3

1885.2(4)

1356(2)

1813(4)

1856.9(8)

1544.8(6)

7073.3(8)

Density

1.405

1.552

1.373

1.445

1.431

1.395

Z

2

2

2

2

2

4

F(000)

830.0

650

778.0

838

682.0

3080.0

µMoKα/mm-1 Mo Kα radiation Temperature/K

0.202 λ=0.71073Å 230(2)

0.202 λ=0.71073Å 223(2)

0.202 λ=0.71073Å 223(2)

0.202 λ=0.71073Å 230(2)

0.202 λ=0.71073Å 223(2)

0.202 λ=0.71073Å 213(2)

Rint

0.0478

0.1388

0.1217

0.0773

0.0825

0.1041

Range of h,k,l

-12/12,-16/16, -18/18

-11/11,-13/13,- -11/11,-14/14,16/16 17/17

-12/12,-16/16,18/18

-12/12,-15/15,-17/17 -20/20,-12/12, -47/47

θmin/max/°

1.504/25.347

1.932/25.349

1.501/25.350

1.556/25.681

Reflections collected/unique/ served [I>2σ(I)]

46975/6890/560 33897/4969/28 23576/5390/3258 32619/6797/4563 29675/5875/3748 5 68

30421/6461/4235

Data/restraints/ parameters

6890/0/503

4969/0/398

5390/0/474

6797/0/485

5875/0/413

6461/1/472

Goodness of fit on F2

0.997

0.981

1.098

1.057

1.120

1.155

Final Rindices[I>2σ(I)]

R1=0.0375 wR2=0.1191

R1= 0.0559 wR2= 0.1148

R1=0.0823 wR2= 0.1963

R1=0.0762 wR2=0.2139

R1=0.0699 wR2=0.1836

R1=0.0864 wR2= 0.2083

Rindices (all data)

R1=0.0525 wR2=0.1388

R1= 0.1249 wR2= 0.1442

R1=0.1392 wR2= 0.2317

R1= 0.1163 wR2= 0.2428

R1=0.1125 wR2=0.2062

R1=0.1317 wR2=0.2335

ob-

1.475/23.534


1.052/25.348


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

Page 8 of 15

Table 1. Continued…… 2 1413884

2a 1413885

2b 1413886

2c 1413887

Empirical formula

C76H69Co2N12O18

C38H34CoN4O9

C36H34CoN4O9S2

C38H36CoN6O9

Formula weight

1556.29

749.62

789.72

779.66

0.32×0.25 ×0.18

0.29×0.12×0.10

0.29×0.16×0.15

0.30×0.25×0.15

Triclinic P1

Triclinic P1

Monoclinic

Space group

Triclinic P1

a/Å

10.2387(11)

10.142(9)

10.119(2)

10.061(3)

b/Å

14.8991(15)

13.222(12)

13.671(3)

25.034(8)

c/Å

25.020(3)

14.872(14)

15.009(3)

14.690(5)

α/°

90.0250(10)

109.018(12)

111.271(3)

90

β/°

93.5110(10)

101.882(12)

101.926(3)

103.081(4)

100.4720(10)

98.999(12)

99.461(3)

90

Volume/Å

3745.9(7)

1790(3)

1826.7(7)

3604.1(19)

Density

1.380

1.391

1.436

1.437

Z

2

2

2

4

F(000)

1614.0

778.0

794.0

1564.0

µMoKα/mm Mo Kα radiation Temperature/K

0.202 λ=0.71073Å 223(2)

0.202 λ=0.71073Å 223(2)

0.202 λ=0.71073Å 223(2)

0.202 λ=0.71073Å 223(2)

Rint

0.0341

0.0797

0.0915

0.0844

Range of h,k,l

-12/12,-17/17, -30/30

-11/11,-14/14, -16/16

-12/12,-16/16, -18/18

-12/12,-30/30, -17/17

θmin/max/°

0.815/ 25.349

1.506/ 23.531

1.521/25.347

1.627/25.348

Reflections collected/unique/observed [I>2σ(I)]

93561/13701/11101

17319/5320/3640

44928/6695/4732

33222/6587/4208

Data/restraints/ parameters

13701/0/981

5320/0/474

6695/0/465

6587/0/482

Goodness of fit on F2

1.111

1.061

1.043

1.031

Final Rindices[I>2σ(I)]

R1=0.0460 wR2=0.1237

R1=0.0731 wR2=0.2014

R1= 0.0853 wR2= 0.2220

R1=0.0536 wR2= 0.1456

Rindices (all data)

R1=0.0600 wR2=0.1355

R1=0.1129 wR2=0.2319

R1=0.1212 wR2=0.2538

R1=0.0990 wR2= 0.1813

CCDC Number

Crystal size/mm Crystal system

γ/° 3

-1


P21/n

Page 9 of 15


Table 2. Dihedral angles and conformation of LP1 in mother compounds 1 and 2 and their daughter products.

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

Compound

d1

d2

d3

conformation

1

42.25

51.39

25.12

syn

1a

38.82

79.62

31.25

anti

1b

34.65

42.71

31.74

syn

1c

28.41

48.68

24.80

syn

1d

16.68

83.87

16.85

anti

1e

17.00

66.86

6.56

anti

2

39.20

44.44

29.28

syn

2a

44.65

49.05

30.40

syn

2b

46.89

51.63

40.38

syn

2c

13.51

54.10

18.88

syn

Magnetic Behaviour of 1. The dc magnetic susceptibility measured on a polycrystalline sample of 1 (applied field of 0.1 T) is shown in Figure 7(a) as of 4.74 cm3 K mol-1 at 100 K. Below this temperature the χMT value decreases rapidly to 3.51 cm3 K mol-1 at 20 K and finally to 1.42 cm3 K mol-1 at 2 K. The 1/χM vs T plots obey the Curie–Weiss (in the temperature range 300–20 K) law (Figure S25 and Table S1, Supporting Information) with a negative Weiss constant of θ = 5.7(7) K, which along with the nature of the χMT vs T plot indicates a dominant antiferromagnetic interaction among the metal ions. The magnetic exchange in the basic dimeric core can be modelled as Co(S1)-J-Co(S2). A reasonable fit can be obtained for noninteracting dinuclear units applying the conventional Hamiltonian: H = - J·S1·S2. Considering this exchange parameter, the analysis of the experimental susceptibility values has been performed using the following expression: 109-110 χM = (Ng2β2/3kT)[A/B]

Therefore, the fitting suggests a weak antiferromagnetic interaction (as expected for CoII-ions bridged by isophalates at distances >4 Å) within the dimeric units. The g value, although a little higher than usual, is well within the acceptable limits. This fitting scheme, however, neglects the effects of spin-orbit coupling, as it is very difficult to reasonably formulate equations for distorted coordinate geometries. In such a situation, one may use the simple phenomenological Equation (2),111-112 where [A + B] equals the Curie constant (C), and E1, E2 can be considered as activation energies for the spin-orbit coupling and the antiferromagnetic exchange interaction, respectively. χMT = A exp (- E1/kT) + B exp (- E2/kT)

………(2).

Using this equation the least square fit (2-300 K) of susceptibility data for 1 gives A + B = 5.07 cm3 K mol-1 (which is very close to the Curie-Weiss fitted value for C = 4.95 cm3 K mol-1), E1/k = 24 K (which is lower than the average values of c.a. 100 K, reported in the literature for CoII-ions in octahedral geometries, indicating a lower orbital contribution) and E2/k = 1.7 K (which is consistent with the antiferromagnetic exchange parameter being very small in magnitude).

………(1) Magnetic Behaviour of 1a.

where A = [6 exp (J/kT) + 30 exp (3J/kT) + 84 exp (6J/kT)] and B = [1 + 3 exp (J/kT) + 5 exp (3J/kT)+ 7 exp (6J/kT)]. The values giving the best fit (20 – 300 K) are J = - 7.25(12) cm-1, and g = 2.302(5) [R = 7.86 × 10-7, Table S2 in Supporting Information].

The Figure 7(b) shows the temperature dependence of χM and χMT values for compound 1a (where χM is the molar magnetic susceptibility per CoII2 unit). The room temperature (300 K) χMT value 4.27 cm3 K mol-1, is again slightly higher than expected for two uncoupled CoII ions and increases very slowly on lowering the temperature and reaches a maxima at 105 K (χMT = 4.62 cm3



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Figure 7. Plots of χM vs. T (inset) and χMT vs. T for (a) compound 1 and (b) compound 1a, in the temperature range of 2–300 K. The red lines indicate the fitting using Equation (1) and the green line using Equation (2).

K mol-1). Below this temperature the χMT value sharply decreases to reach 2.36 cm3 K mol-1 at 2 K. The 1/χM vs T plots, in the temperature range 300–2 K, obey the Curie–Weiss law (Figure S25 and Table S3 in Supporting Information) with a positive Weiss constant of θ = 1.2(8) K [C = 4.40(2) cm3 K mol-1, Radj = 0.99842], but a better fit can be obtained in the temperature range 150-2 K, with a negative Weiss constant θ = -3.4(3) K [C = 4.73(1) cm3 K mol-1, Radj = 0.99963]. The nature of these susceptibility plots suggests dominant antiferromagnetic exchange (especially the low temperature region) among the CoII ions through carboxylato bridges, although the initial increase in χMT values (300 to 105 K) is difficult to explain. This increase may be due to the effects of small orbital contributions for the distorted trigonal bipyramidal CoII ions or small impurities (which is always a possibility, especially for SCSC transformed materials).

netic coupling between the adjacent metal atoms. In this present case, from the structural analysis of 1 and 1a, it is observed that two syn-syn carboxylate bridging is present between two neighbouring magnetically interacting CoII centres for both 1 and 1a. Therefore the observation of antiferromagnetic behaviour in the magnetic susceptibility plots with coupling constant (J) values of - 7.25(12) cm-1 for 1 and - 4.57(12) cm-1 for 1a is perfectly justified. However the extent of antiferromagnetic coupling is found to differ slightly which can be attributed to the difference in Co···Co distances [4.146 Å for 1 and 4.378 Å for 1a] and also perhaps due to the different coordination geometries around the CoII centers [distorted octahedral for 1 and distorted trigonal bipyramidal for 1a] arising due to the temperature driven SCSC transformations.

The data could not be fitted for the Equation (1), with modifications for interacting dimers, while with the simple dimer model only a poor quality fitting could be obtained, with the fitted values as (20 – 300 K) are J = - 4.57(12) cm-1, and g = 2.249(5) [R = 7.90 × 10-7] (Table S4 in Supporting Information). Also, using Equation (2), we obtain (2-300 K), A + B = 4.58 cm3 K mol-1 (which is very close to the Curie-Weiss fitted value for C = 4.73 cm3 K mol-1), E1/k = 7 K (which is very low and consistent with the coordination geometry of the CoII ions) and E2/k = 0.3 K (which is consistent with very small and almost negligible antiferromagnetic exchange). Magneto-structural correlations. Previous studies on the carboxylate bridged dinuclear metal complexes show that syn−syn bridging pattern triggers antiferromagnetic exchange interactions between the metal ions, whereas anti−anti and syn−anti bridging modes often lead to weak ferromagnetic or antiferromagnetic couplings.113-116 Moreover it is also well known that the metal···metal distances as well the coordination geometry around the metal centers affect the extent of mag-

Figure 8. Comparison of the carboxylate bridging modes, Co···Co distances and coordination geometries around the CoII centers that govern the magnetic interaction in 1 (top) and 1a (bottom).


Page 11 of 15

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CONCLUSIONS In conclusion, we have successfully synthesized and structurally characterized two new MOFs namely, 1 and 2 derived from a conformationally flexible amide funtionalized bis-pyridyl ligand LP1 and dicarboxylates (isophthalate and terepthalate). While 1 exhibited stimuli responsive breathing behaviour upon exposure to heat and various exoganeous solvents (acetone, DMSO, MeOH & DEF), 2 readily exchanged solvents when soaked in acetone and DMSO displaying no breathing. The SCSC breathing behaviour of 1 represents one of the scarce examples of SCSC breathing in MOFs.80-91 All these SCSC transformations involving 1 and 2 were mutually reversible between its mother and daughter crystals and such reports are also not very common. SXRD data revealed that 1 was prone to breathing because of its easily adjustable 2D network with flexible amide based ligand backbone whereas 2fold interpenetrated 3D network in 2 presumably prevented breathing. However, 2 was able to exchange solvents because of the conformational flexibility of LP1 as revealed by the SXRD structure of the intermediate 2c. DFT calculations suggested that energy barriers of the various conformations were relatively small supporting the conformational flexibility of LP1. Furthermore, 1 exhibited heat induced magnetic property changes while going from 1 to 1a in SCSC fashion. Experimental Section. Materials and Methods. All reagents and chemicals are purchased from commercial sources and are used without further purification. Characterization data of the ligand LP1 is described in the Supporting Information. FT-IR spectra are obtained on a Nicolate MAGANA-IR 750 spectrometer with samples prepared as KBr pellets. TGA measurements are carried out with a TA instrument SDT Q600. Powder X-ray diffraction patterns are collected on a Bruker D8 AVANCE instrument. C, H and N microanalyses are done with a 2400 Series-II CHN Analyzer. Hot stage microscopy analyses are conducted on Linkam T9-HS hot stage equipped with a Leica MZ16 microscope. Topological Analyses are carried out using TOPOS 4.0 software, following the concept of simplified underlying nets.94-98 Magnetic measurements are performed using a Quantum Design VSM SQUID magnetometer. The measured values are corrected for the experimentally measured contribution of the sample holder, while the derived susceptibilities are corrected for the diamagnetism of the samples, estimated from Pascal’s tables.110 Computational method. Full geometry optimizations and single point energy calculations through the Density Functional Theory (DFT), were carried out using the Gaussian 09 package.117 The calculations were performed using the hybrid B3LYP function 118119 as implemented in the Gaussian 09 program. For the optimizations of the structure of LP1 in the syn and anti conformations, the initial geometry was derived from the structures of 1 and 1a respectively. 631 g(d) basis set was used for all the calculation. Normal convergence criterion (10−4 a.u.) was applied for the optimizations. The ground state geometry optimizations were monitored by the subsequent frequency test and no imaginary frequencies were observed. Gas Adsorption Studies. Low pressure volumetric gas adsorption measurements involved in this work were performed at 77 K for N2 at pressures ranging from 0 to 1 atm on a Quantachrome Quadrasorb automatic volumetric instrument.

Synthesis of 4,4ˊ-oxybis(N-(pyridine-4-yl)benzamide)(LP1): 4,4ˊ-oxydibenzoyl chloride (1.77 g, 6 mmol) was dissolved in 50 mL of dry DCM and to it was added 50 mL dry THF solution of 4-aminopyridine (1.223 g, 13 mmol), giving an immediate white precipitate. The reaction mixture was refluxed for overnight at 60°C, cooled and filtered. The precipitate was washed with 1:1 mixture of DCM / THF and dried under vacuum. To the suspension of this hydrochloride salt in 40 mL MeOH, 2 mL (excess) triethylamine was added dropwise. The reaction mixture was stirred at room temperature for overnight. The solid precipitate was filtered, washed with distilled water and recrystallized from methanol and isolated as white crystalline material. Yield: 1.35 g (55%). 1H-NMR (400 MHz, DMSO-d6, 25°C): δ = 10.57 (s, 2H), 8.48-8.46 (d, J= 8.0, 4H), 8.07-8.05 (d, J= 8.0, 4H), 7.78-7.77 (d, J= 8.0, 4H), 7.24-7.22 (d, J= 8.0, 4H) ppm.13C-NMR (500 MHz, DMSO-d6, 25°C): δ = 165.53, 158.95, 150.26, 145.90, 130.36, 129.70, 118.56, 113.98 ppm. Elemental Analysis: Calculated for C24H18N4O3.CH3OH (%): C, 67.86; H, 5.01; N 12.66; found: C, 67.61; H, 4.76; N, 12.37. FT-IR (KBr pellet, 400-4000 cm-1): 3157 (brs), 3068 (brs), 2948 (s), 1689 (s), 1595 (s), 1506 (s), 1493 (s), 1416 (s), 1329 (s), 1290 (s), 1267 (m), 1163 (s), 1107 (m), 1092 (m), 1001 (m), 899 (w), 833 (m), 756 (w), 582 (w), 509 (w). Synthesis of [{Co(LP1)(IPA)}(DMF)2(H2O)]∞ (1). 1 mL aqueous solution of Co(NO3)2. 6H2O (29.10 mg) was added to the mixed solution of LP1 (20.50 mg) and isophthalic acid (IPA) (16.61 mg) in a mixture of 3 mL DMF and 1 mL MeOH. The reaction was heated to 80°C in a sealed container for 48 h. Upon slow cooling to room temperature pink coloured block shaped crystals were obtained (56% yield based on LP1) which was then filtered and dried in air. IR (400-4000 cm-1): 3375 (brs), 3299 (w), 3061 (w), 1724 (w), 1690 (s), 1672 (s), 1620 (s), 1597 (s), 1527 (m), 1497 (s), 1395 (s), 1299 (s), 1252 (s), 1211 (m), 1168 (m), 1095 (m), 1014 (w), 833 (s), 746 (s), 717 (s), 662 (m), 534 (m). Elemental Analysis: C38H38CoN6O10 (797.67): Calcd. C, 57.29; H, 4.80; N, 10.55; found C, 57.43, H 4.69, N 10.37. Preparation of [{Co(LP1)(IPA)}]∞ (1a). Single crystals of compound 1 were heated to 170°C in an oil bath for about one hour under atmospheric pressure. Then it was slowly cooled to room temperature and 1a has been isolated as purple coloured crystals. IR (400-4000 cm-1): 3301 (brs), 3168 (brs), 3001 (w), 1664 (s), 1666 (m), 1593 (s), 1568 (s), 1499 (s), 1421 (m), 1331 (s), 1252 (s), 1168 (m), 1090 (w), 1014 (w), 837 (m), 743 (m), 711 (m), 534 (m), 501 (w). Elemental Analysis: C32H22CoN4O7 (633.47): Calcd. C, 60.65; H, 3.50; N, 8.84; found C, 60.49, H 3.65, N 8.88. Preparation of [{Co(LP1)(IPA)}((CH3)2CO))2]∞(1b). Crystals of as synthesized compound 1, which were still in the mother liquor, were transferred into a 3 mL sample vial. The mother liquor was decanted and to this 1 mL of acetone solution was added. The sample vial was sealed and kept for 24 hours. During this period acetone was replenished for three times. 1b was isolated as pink crystals. IR (400-4000 cm-1): 3787 (w), 3068 (w), 1703 (m), 1664 (s), 1593 (s), 1485 (m), 1423 (m), 1330 (m), 1252 (s), 1209 (m), 1169 (w), 1093 (w), 1012 (w), 835 (m), 744 (m), 715 (m), 584 (w). Elemental Analysis. C38H34CoN4O9 (749.62): Calcd. C, 60.88; H, 4.57; N, 7.47; found C 60.63, H 4.45, N 7.21. Preparation of [{Co(LP1)(IPA)}(DMSO)2(H2O)]∞ (1c). Solvent exchange with DMSO was carried out following similar procedure as that of 1b. After 24 hours the compound 1c is filtered from DMSO and dried in air. IR (400-4000 cm-1): 3425 (brs), 3199 (brs), 2910 (w), 1688 (s), 1616 (s), 1593 (s), 1508 (s), 1497 (s), 1423 (s), 1395 (s), 1333 (s), 1296 (s), 1252 (s), 1213 (m), 1170 (m), 1096 (m), 839 (m), 751 (s), 586 (m), 527 (w) . Ele-


11


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

mental Analysis. C36H36CoN4O10S2 (807.74): Calcd. C, 53.53; H, 4.49; N, 6.94; found C 53.27, H 4.24, N 6.67. Preparation of [{Co(LP1)(IPA)}(H2O)2]∞ (1d). Solvent exchange with MeOH was carried out following similar procedure as that of 1b. After 24 hours the compound 1c is filtered as purple crystals from MeOH and dried in air. IR (400-4000 cm-1): 3331 (w), 1671 (m), 1609 (s), 1591 (s), 1522 (s), 1489 (s), 1425 (m), 1331 (m), 1252 (s), 1236 (m), 1207 (m), 1167 (m), 1095 (w), 1014 (m), 896 (w), 838 (m), 723 (w), 536(W). Elemental Analysis. C32H26CoN4O9 (669.50): Calcd. C, 57.40; H, 3.91; N, 8.36; found C 57.19, H 3.62, N 8.52. Preparation of [{Co2(LP1)2(IPA)2}(DEF)2(H2O)]∞ (1e). Solvent exchange with DEF was carried out following similar procedure as that of 1b. After 24 hours the compound 1e is filtered from DEF and dried in air. IR (400-4000 cm-1): 3787 (m), 3317 (w), 1658 (s), 1597 (s), 1497 (m), 1487 (m), 1406 (m), 1385 (m), 1329 (s), 1244 (w), 1209 (m), 1066 (w), 837 (s), 745(s), 538 (W). Elemental Analysis. C74H66Co2N10O17 (1485.23): Calcd. C, 59.84; H, 4.48; N, 9.43; found C 59.61, H 4.52, N 9.30. Synthesis of [{Co2(LP1)2(TPA)2}(DMF)4]∞.(2). To 1 mL aqueous solution of Co(NO3)2. 6H2O (29.10 mg) was added a mixture of LP1 (20.50 mg) and terephthalic acid (TPA) (16.61 mg) in 3 mL DMF and 2 mL MeOH. This solution was stirred for 30 minutes and then transferred to sealed container. The reaction was container was heated at 80°C for 48 hours. Upon slow cooling to room temperature pink coloured block shaped crystals were obtained (62% yield based on LP1) which was then filtered and dried in air. IR (400-4000 cm-1): 3342 (brs), 3205 (w), 2997 (w), 1706 (w), 1660 (s), 1595 (s), 1529 (m), 1497 (s), 1395 (s), 1330 (m), 1299 (m), 1252 (s), 1209 (m), 1170 (w), 1095 (w), 1014 (w), 837 (s), 748 (s), 660 (m), 584 (w). Elemental Analysis. C76H69Co2N12O18 (1556.29): Calcd. C, 58.65; H, 4.47; N, 10.80; found C 58.39, H 4.45, N 10.58. Synthesis of [{Co(LP1)(TPA)}((CH3)2CO))2]∞.(2a). Crystals of as synthesized compound 2, which were still in the mother liquor, were transferred into a 3 mL sample vial. The mother liquor was decanted and to this 1 mL of acetone solution was added. The sample vial was sealed and kept for 24 hours. During this period acetone was replenished for three times and pink crystals of 2a were isolated. IR (400-4000 cm-1): 3369 (w), 3303 (w), 1701 (s), 1670 (s), 1612 (s), 1593 (s), 1492 (s), 1493 (s), 1421 (m), 1402 (m), 1332 (s), 1252 (s), 1211 (s), 1172 (m), 1089 (m), 1016 (m), 833(s), 742(m0, 719 (m), 534(m). Elemental Analysis. C38H34CoN4O9 (749.62): Calcd. C, 60.88; H, 4.57; N, 7.47; found C 61.11, H 4.45, N 7.69. Synthesis of [{Co(LP1)(TPA)}(DMSO)2]∞.(2b). Solvent exchange with DMSO was carried out following similar procedure as that of 2a. After 24 hours the compound 2b is filtered as pink crystals from DMSO and dried in air. IR (400-4000 cm-1): 3311 (w), 3079 (w), 1692 (s), 1597 (s), 1496 (s), 1395 (s), 1330 (m), 1295 (w), 1253 (s), 1206 (w), 1177 (m), 1064 (m), 1016 (s), 892 (w), 839 (s), 744 (s), 596 (m), 538 (m) . Elemental Analysis. C36H34CoN4O9S2 (789.72): Calcd. C, 54.75; H, 4.34; N, 7.09; found C 54.59, H 4.31, N 6.99. Synthesis of [{Co(LP1)(TPA)}(DMF)2]∞.(2c). Crystals of as synthesized compound 2, which were still in the mother liquor, were transferred into a 3 mL sample vial. The mother liquor was decanted and to this 1 mL of acetone (or DMSO) solution was added. The sample vial was sealed and kept for 10 hours and intermediate 2c was isolated as pink crystals. IR (400-4000 cm-1): 3363 (brs), 2925 (m), 2854 (w), 1747 (m), 1683 (s), 1668 (s),

Page 12 of 15

1593 (s), 1497 (s), 1394 (s), 1333 (m), 1298 (m), 1252 (s), 1211 (m), 1172 (m), 1095 (w), 821 (m), 748 (s), 637 (w). Elemental Analysis. C38H36CoN6O9 (779.66): Calcd. C, 58.54; H, 4.65; N, 10.78; found C 58.29, H 4.42, N 10.99. X-ray Crystallography. Single-crystal X-ray diffraction data were collected using Mo Kα (λ = 0.7107 Å) radiation on a BRUKER APEX II diffractometer equipped with a CCD area detector. Data collection, data reduction, and structure solution reﬁnement were carried out using APEX II. All the structures were solved by direct methods and refined in a routine manner. In all the cases, the non hydrogen atoms are treated anisotropically except for disordered atoms. Whenever possible, the hydrogen atoms were located on a difference Fourier map and refined. In other cases, the hydrogen atoms were geometrically ﬁxed. In case of compound 1d, 2b and 2c the disordered molecules are refined by constraints using the PART command, with a total occupancy of 1. Crystallographic data are summarized in table 1 in the manuscript and S6 in the supporting information. CIF files for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre (CCDC). CCDC1413878-1413888 contains the supplementary crystallographic data for the paper. Copies of the data can be obtained, free of charge on application to the CCDC, 12 Union Road, Cambridge, CB2 1EZ UK [Fax: 44 (1233) 336 033 e-mail: [email protected]]. ASSOCIATED CONTENT Supporting Information Include details of characterization of ligand LP1, TGA, PXRD, plots of magnetic analysis, DFT calculations, optical images of single crystal before and after SCSC and selected bond angles and bond lengths table for compound 1, 2 and their guest exchanged products. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected].

ACKNOWLEDGMENTS PD thanks Department of Science & Technology (DST), New Delhi, India for financial support. SG thanks Indian Association for the Cultivation of Science , Kolkata for the research fellowship. SCXRD data were collected in the DBT-funded X-ray diffraction facility under the CEIB program (BT/01/CEIB/11/v/13) in the Department of Organic Chemistry, IACS.

REFERENCES (1) Hoskins, B. F.; Robson, R. J. J. Am. Chem. Soc. 1989, 111, 59625954. (2) Biradha, K.; Ramanan, A.; Vittal, J. J. Cryst. Growth Des. 2009, 9, 2969-2970. (3) James, S. L. Chem. Soc. Rev. 2003, 32, 276-288. (4) Perry IV, J. J.; Perman, J. A.; Zaworotko, M. J. Chem. Soc. Rev. 2009, 38, 1400-1417. (5) Adarsh, N. N.; Dastidar, P. Chem. Soc. Rev. 2012, 41, 3039-3060. (6) Banerjee, R.; Phan, A.; Wang, B.; Knobler, C.; Furukawa, H.; O'Keffee, M.; Yaghi, O.M. Science 2008, 319, 939-943. (7) Zhou, H.-C.; Kitagawa, S. Chem. Soc. Rev. 2014, 43, 5415-5418. (8) Janiak, C.; Veith, J. K. New J. Chem. 2010, 34, 2366-2388; (9) Piepenbrock, M. M.; Lloyd, G. O.; Clarke, N.; Steed, J. W. Chem. Rev. 2010, 110, 1960-2004.


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Single-Crystal-to-Single-Crystal Breathing and Guest Exchange in CoII Metal-Organic Frameworks Sumi Ganguly, Sandip Mukherjee and Parthasarathi Dastidar*

Based on structural rationale, new CoII based metal-organic frameworks (MOFs) that displayed breathing responsive to stimuli like heat and guest has been developed. The examples reported herein belong to the handful reports of breathing MOFs via single crystal to single crystal fashion.


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Single-Crystal-to-Single-Crystal Breathing and Guest Exchange in

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