Metallogels and Silver Nanoparticles Generated ... - ACS Publications

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Crystal Growth & Design

Metallogels and Silver Nanoparticles Generated from a Series of Transition Metal Based Coordination Polymers Derived from a New Bis-pyridyl-Bis-amide Ligand and various carboxylates Karabi Nath, Ahmad Husain and Parthasarathi Dastidar*. Department of Organic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata-700032, India. KEYWORDS coordination polymer, metallogel, supramolecular interactions, nanoparticles.

ABSTRACT: A new series of coordination polymer namely; CP2 [{(H2O)Co1.5(µ-3-bpna)1.5(µ-btc)}·3DMF·3H2O]α, CP3 [{Cd(µ3-bpna)(µ-hbtc)}·CH3OH·2H2O]α, CP4 [{Co(µ-3-bpna)(µ-ipa)}·DMF·2H2O]α, CP5 [{Co(µ-3-bpna)(µ-1,3-pda)}·DMF]α, CP6 [Cd(µ-3-bpna)0.5(µ-1,3-pda)]α, CP7 [(H2O)Co0.5(µ-3-bpna)0.5(µ-1,4-pda)0.5]α and CP8 [{Zn(µ-3-bpna)(µ-oba)}·DMF·2H2O]α has been synthesized by reacting a hydrogen bond functionalized bis-pyridyl ligand namely N’,N’’-di(pyridin-3-yl)naphthalene-2,6dicarboxamide with various transition metal salts and different di- or tri-carboxylates (as co-ligand) displaying 2D and 3D network topology having lattice occluded solvents in the majority of the cases. A 1D coordination polymer namely CP1 [{Ag0.5(µ-3bpna)}0.5·0.5BF4·CH3CN]α has also been isolated by reacting 3-bpna with AgBF4 in absence of any carboxylate co-ligand. All the CPs were characterized by single crystal X-ray diffraction. Interestingly, two such CPs namely CP1 and CP2 produced metallogels, which were characterized by rheology, transmission electron microscopy, and X-ray powder diffraction. The metallogel of CP1 produced Ag nanoparticle within the gel-bed upon exposure to light.

Introduction Coordination polymers (CPs) are an important class of metalorganic hybrid compounds that are formed spontaneously when multidentate organic linker(s) (ligand) is allowed to react with an appropriate metal salt(s).1–4 The field really took off when Robson et al. reported a CuII diamondoid network derived from three dimensionally linked rod-like segments, namely 4,4′,4′′,4′′′- tetracyanotetraphenyl methane.5 CPs are usually highly crystalline compounds enabling detailed structural characterization at the atomic level by single crystal Xray diffraction (SXRD). Such sub-molecular level structural information led the researchers to design wide varieties of CPs with potential applications such as in gas storage,6,7 anion8–10 and cation11 separation, catalysis,12–14 magnetic materials,15 drug delivery,16,17 sensors,18 opto-electronics,19,20 etc. As a part of our ongoing research program on CPs,3 we are interested in developing CPs having intriguing structures and functions such as in situ anion and cation separation,11 metallogelation,21 metal-nanoparticle synthesis and catalysis22 etc. For this purpose, we have been focusing on pyridyl or carboxylate based multidentate ligands equipped with hydrogen bonding capable backbone such as amide or urea functionality. Among the various potential applications CPs offer, metallogelation23–29 is extremely important to study because of their potential applications in catalysis,30,31 sensing,18,32,33 photophysics,34,35 synthesis of nanomaterials,27,36–38 magnetic materials,39,40 and so forth. Gel is a soft material displaying both the properties of solid and liquid. It is usually formed by the immobilization of the liquid (gelling solvent) within the gel network that is formed either by purely noncovalent interactions

(hydrogen bonding, π-π stacking, van der Waals interactions etc.) or by polymerization via covalent bond formation.41,42 When metal ion is a part of the gel network, the resulting gel is called metallogel.23 Supramolecular gel containing metal nanoparticle is also called metallogel.43 Discrete coordination compounds,44–46 infinite CP,47 crossed-linked CPs48 – all have shown to be capable of immobilizing (gelling) solvent producing metallogels. Designing CPs is a challenging task. There are several efforts by various groups to meet such a challenge; for example, introducing long alkyl chain (hydrophobic group) on coordination complex,49 installing a well-known aromatic-linkersteroid (ALS) moiety (a well-known gel-forming moiety), on a metallocene,50 utilizing surface modifications with mixed ligands of different lengths,51 slowly crystallizing CPs with flexible ligands,52 exploiting the well-studied supramolecular synthon53,54 etc. In an another approach, we55,56 and others57 have suggested that molecular solids having lattice occluded solvents were good candidate for gelation because of the structural similarity present between gels and solvent occluded molecular solids – in both the cases, a large amount of solvents were occluded. With this background in mind, we set out to synthesize a new series of CPs that are expected to generate lattice occluded solids which, under suitable condition, might display metallogelation behavior. For this purpose, we synthesized a hitherto unexplored bis-pyridyl-bis-amide ligand namely N’,N’’di(pyridin-3-yl)naphthalene-2,6-dicarboxamide (hereafter 3bpna). We envisaged that the amide moieties and relatively large π-cloud of the central naphthyl ring would be of some

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help in the self-assembly process of gelation via hydrogen bonding and π-π stacking interactions, respectively. Moreover, the amide functionality is also expected to invite guest molecules as lattice occluded solvents which in turn might contribute to metallogelation behavior of the resulting CPs. A series of crystalline CPs was indeed isolated when 3-bpna was reacted with various metal salts and different bis- or triscarboxylate co-ligands (Scheme 1). Experimental Section Materials and Methods: All chemicals were commercially available and used without further purification. The elemental analyses were carried out using a PerkinElmer 2400 Series II CHN analyzer. FT-IR spectra were recorded using PerkinElmer Spectrum GX. The mass spectra were recorded on QTOF Micro YA 263 mass spectrometer. NMR spectra (1H and 13 C) were recorded using a 300 MHz Bruker Avance DPX 200 spectrometer. The photoluminescence (PL) spectra were obtained from solid films prepared by drop casting an aqueous suspension of the 3-bpna and CPs on quartz plates using a Nanolog spectrofluorometer from HORIBA Jobin Yvon. Synthesis of the ligand 3-bpna To a solution of 2,6-napthalenedicarboxylic acid (500 mg, 2.3 mmol) in dry dichloromethane (DCM), 2 ml of oxalyl chloride and 4 drops of DMF was added and kept stirring with a gut tube for 12 hours to yield a yellow suspension which was dried under vacuum. The dried powder was stirred in toluene for two hours and the sticky mass of oxalyl chloride was removed by decanting the toluene solution which was further evaporated to isolate the pure acid chloride, as a dried mass (600 mg, 2.37 mmol, yield: 70%). To a solution of the acid chloride (550 mg, 2.1 mmol) and 1 ml of triethylamine in dry DCM, 3-amino pyridine (395 mg, 4.2 mmol) in dry THF was added drop wise. The thick white coloured precipitate thus formed, was kept stirring with refluxing for 12 hours. After filtration, the precipitate was washed with DCM-THF mixture properly; air dried, and treated with 5% NaHCO3 solution and washed with distilled water, dried and recrystallized from DMSO (yield: 650 mg, 70%). Anal. calcd. for C22H16N4O2 (%): C, 71.73; H, 4.38; N, 15.21. Found: C, 71.42; H, 4.14; N, 15.00. 1H NMR (500 MHz, DMSO-d6): δ = 10.73 (2H, s), 8.99 (2H, s), 8.69 (2H, s), 8.358.34 (2H, d, J = 5 Hz), 8.26-8.25 (4H, d, J = 5 Hz), 8.13-8.12 (2H, d, J = 5 Hz), 7.45-7.43 (2H, dd, J = 5, 5 Hz) ppm. ESIMS: calcd for C22H16N4O 369.18 (M+1). Found: [M + Na]+ 391.17. FT-IR (KBr, cm–1): 3346, 3265, 3047, 1670, 1596, 1541, 1479, 1413, 1328, 1307, 1234, 1184, 1134, 1105, 1024, 943, 916, 900, 811, 790, 752, 700, 632, 487, 408. Synthesis and Characterization of CPs CP1: CP1 was synthesized by layering carefully a CH3CN solution of AgBF4 (31 mg, 0.16 mmol) to a DMSO solution of 3-bpna (30 mg, 0.08 mmol) in a thin long glass tube and kept for slow evaporation at room temperature. After three weeks X-ray quality block shaped white crystals were obtained. Calcd. for C24H19AgBF4N5O2 (%): C 47.72, H 3.17, N 11.59. Found: C 47.18, H 3.63, N 10.79. FT-IR (KBr, cm–1): 3398, 3083, 1672, 1596, 1541, 1481, 1413, 1328, 1307, 1263, 1234, 1188, 1134, 1105, 1070, 1026, 945, 916, 790, 700, 632, 487. CP2: CP2 was synthesized under solvothermal condition from a DMF-methanol-water solution (3:1:1) of a mixture of 3bpna (30 mg, 0.08 mmol), Co(NO3)2·6H2O (23.2 mg, 0.08 mmol) and trimesic acid (16.8 mg, 0.08 mmol). The mixture

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was taken in a 25 ml torsion vial, heated at 75 °C for 60 h, and allowed to cool slowly (5 °C per hour in 12 h). After cooling, block-shaped pink crystals were isolated. Anal. calcd. for C40H43Co2N7O11 (%): C 52.47, H 4.73, N 10.71 Found: C 51.97, H 4.54, N 11.03. FT-IR (KBr, cm–1): 3334, 3056, 1662, 1606, 1541, 1485, 1436, 1384, 1301, 1280, 1240, 1134, 1099, 1051, 929, 819, 800, 729, 700, 659, 640, 630, 594, 584. CP3: The synthetic procedure was similar to that of CP2 under solvothermal condition from a DMF-methanol-water solution of a mixture of 3-bpna (30 mg, 0.08 mmol), Cd(NO3)2·4H2O (24.6 mg, 0.08 mmol) and trimesic acid (16.8 mg, 0.08 mmol). After cooling, block-shaped crystals were isolated. Anal. calcd. for C32H30CdN4O11 (%): C 50.64, H 3.98, N 7.38 Found: C 51.05, H 3.14, N 7.73. FT-IR (KBr, cm–1): 3375, 3068, 1676, 1662, 1541, 1487, 1419, 1367, 1330, 1303, 1199, 1182, 1130, 810, 757, 727, 696, 644. CP4: The synthetic procedure was similar to that of CP2 under solvothermal condition from a DMF-methanol-water solution of a mixture of 3-bpna (30 mg, 0.08 mmol), Co(NO3)2·6H2O (23.2 mg, 0.08 mmol) and isophthalic acid (13.28 mg, 0.08 mmol). After cooling, block-shaped pink crystals were isolated. Anal. calcd. for C34H35CoN5O9 (%): C 56.99, H 4.11, N 9.77 Found: C 56.41, H 4.03, N 9.32. FT-IR (KBr, cm–1): 3365, 3062, 1652, 1606, 1541, 1483, 1398, 1328, 1299, 1191, 1107, 918, 806, 742, 721, 696, 418. CP5: The synthetic procedure was similar to that of CP2 under solvothermal condition from a DMF-methanol-water solution of a mixture of 3-bpna (30 mg, 0.08 mmol), Co(NO3)2·6H2O (23.2 mg, 0.08 mmol) and 1,3-phenylene diacetic acid (15.52 mg, 0.08 mmol). After cooling, blockshaped pink crystals were isolated. Anal. calcd. for C35H33CoN5O7 (%): C 60.52, H 4.79, N 10.08 Found: C 59.45, H 4.42, N 9.79. FT-IR (KBr, cm–1): 3296, 3064, 1670, 1608, 1581, 1544, 1485, 1421, 1299, 1267, 1236, 1191, 1134, 1095, 811, 804, 756, 723, 698, 663, 640, 476. CP6: The synthetic procedure was similar to that of CP2 under solvothermal condition from a DMF-methanol-water solution of a mixture of 3-bpna (30 mg, 0.08 mmol), Cd(NO3)2·4H2O (24.6 mg, 0.08 mmol) and 1,3-phenylenediacetic acid (15.52 mg, 0.08 mmol). After cooling, block-shaped crystals were isolated. Anal. calcd. for C32H26CdN4O6 (%): C 52.13, H 3.88, N 6.44 Found: C 52.50, H 3.62, N 5.94. FT-IR (KBr, cm–1): 3278, 3085, 1677, 1614, 1552, 1537, 1517, 1485, 1469, 1404, 1307, 1247, 1195, 1161, 1124, 908, 804, 757, 738, 698, 659, 592, 480. CP7: The synthetic procedure was similar to that of CP2 under solvothermal condition from a DMF-methanol-water solution of a mixture of 3-bpna (30 mg, 0.08 mmol), Co(NO3)2·6H2O (23.2 mg, 0.08 mmol) and 1,4phenylenediacetic acid (15.52 mg, 0.08 mmol). After cooling, block-shaped pink crystals were isolated. Anal. calcd. for C32H26CoN4O6 (%): C 60.02, H 4.22, N 9.01 Found: C 59.31, H 4.62, N 8.62. FT-IR (KBr, cm–1): 3321, 3028, 1670, 1606, 1539, 1487, 1390, 1338, 1303, 1257, 1182, 1134, 894, 813, 790, 757, 703, 624, 599, 584. CP8: The synthetic procedure was similar to that of CP2 under solvothermal condition from a DMF-methanol-water solution of a mixture of 3-bpna (30 mg, 0.08 mmol), Zn(NO3)2·6H2O (24.6 mg, 0.08 mmol) and oxy-bisbenzoic acid (20.6 mg, 0.08 mmol). After cooling, plate-shaped crystals were isolated. Anal. calcd. for C44H46ZnN4O10 (%): C 61.72, H 4.68, N 9.13 Found: C 61.01, H 4.08, N 8.63. FT-IR


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Scheme 1. Schematic representation for the synthesis of CP1-CP8. (KBr, cm–1): 3276, 3078, 1666, 1595, 1544, 1500, 1421, 1400, 1284, 1232, 1188, 1134, 877, 808, 784, 773, 698, 663, 649, 599. Metallogelation: In a typical gelation experiment for CP1, 3bpna (22 mg, 0.06 mmol) was dissolved in 0.4 ml hot DMF to get a clear solution, and mixed with 0.6 ml aqueous solution of AgBF4 (11.7 mg, 0.06 mmol) at room temperature; so that the metal:ligand molar ratio was 1:1 and the resulting DMF or DMSO/water ratio was 2:3 v/v. The gel formed almost instantaneously. Gel formation was confirmed by the test tube inversion method. In a typical gelation experiment for CP2, 3-bpna (17 mg, 0.046 mmol) was dissolved in 0.4 ml hot DMF to get a clear solution and btc (9.7 mg, 0.046mmol) was added; this solution was mixed with 0.6 ml aqueous solution of Co(NO3)2·6H2O (13.4 mg, 0.046 mmol) at room temperature so that the metal:3-bpna:btc, molar ratio was 1:1:1 and the resulting DMF or DMSO/water ratio was 2:3 v/v. The gel formed almost instantaneously. Gel formation was confirmed by test tube inversion method. Transmission electron microscopy: TEM micrographs were recorded using a JEOL JEM-2011 instrument operating at 200 keV. Sample preparation involved drop casting a suspension of gel in water onto a 300 mesh carbon film supported by a copper grid, which was then dried in air. Rheology Studies: The rheological response of both the metallogels was studied under dynamic and steady shear measurement at room temperature (25 °C) on parallel-plate geometry (25 mm diameter, 1 mm gap). Rheological experiments were carried out using Anton Paar Modular Compact Rheometer (MCR 102). Single Crystal X-ray Diffraction Analysis: Suitable, apparently single crystals of 3-bpna and CP1 – CP8 were selected. Data collection was carried out on a Bruker SMART APEX II CCD diffractometer using graphite monochromated Mo Kα (λ =

0.71073 Å) radiation. Data reduction and unit cell refinement were performed using SAINT-Plus.58 The structures were solved by direct method and refinement procedure by fullmatrix least-squares method, based on F2 values against all reflections was performed by SHELXL-2014/7.59 Powder X-ray diffraction: Powder X-ray diffraction (PXRD) measurements were performed on a Bruker AXS D8 Advance X-ray (Cu Kα1 radiation, λ = 1.5406 Å) diffractometer in the 5–35° 2θ range using a 0.02° step size per second. The sample was prepared by making a thin film from the finely powdered sample (~30 mg) over a glass slide. Results and Discussion The acylamide ligand 3-bpna was synthesized by reacting 2,6naphthalenedicarbonyl dichloride with 3-aminopyridine in a dichloromethane (DCM)–THF mixture under refluxing conditions. Blocked shape crystals of 3-bpna were grown by slow evaporation form a DMSO solution. CP1 was crystalized by layering a CH3CN solution of AgBF4 to a DMSO solution containing 3-bpna at room temperature for 3 weeks to afford x-ray quality blocked shape crystals. Crystals for CP2-CP8 were obtained by solvothermal reaction in a DMF-methanolwater solution (3:1:1).We have reacted 3-bpna (in separate experiments) with various polycarboxylates and several metal salts [AgBF4, Co(NO3)2·6H2O, Cd(NO3)2·4H2O and Zn(NO3)2·6H2O] in a 1 : 1 : 1 (metal : 3-bpna : polycarboxylate) molar ratio to generate CPs CP2-CP8. Crystallographic data, bond length and bond angles, and hydrogen bonding parameters for all the crystals were listed in tables 1, S1 and S2, respectively. Crystal structure of N',N''-bis(3-pyridyl)naphthalene-2,6dicarboxamide (3-bpna) Single-crystal X-ray diffraction analysis reveals that 3-bpna crystallizes in the centrosymmetric monoclinic space group P21/n. The asymmetric unit contains half of 3-bpna as the free ligand is located on a center of inversion. Both the amide groups of 3-bpna are in anti-periplanar conformation. The molecule is significantly nonplanar as evident from the dihedral angle of 13.2° involving the terminal pyridyl rings and the



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Table 1. Crystallographic data for compounds 3-bpna and CP1 –CP8. 3-bpna

CP1

CP2

CP3

CP4

CP5

CP6

CP7

CP8

CCDC No.

1017718

1017721

1028834

1017720

1028835

1028836

1017719

1028837

1028838

emp. formula

C22H16N4O2

C26H22AgBF4N6O2

C102H104Co3N18O32

C32H26CdN4O11

C33H27CoN5O9

C35H31CoN5O7

C21H16CdN2O5

C32H28CoN4O8

C39H31N5O10Zn

formula weight

368.39

645.17

2270.82

754.97

696.52

692.58

488.76

655.51

795.06

Temp. (K)

296(2)

296(2)

213(2)

173(2)

296(2)

296(2)

223(2)

298(2)

296(2)

λ (Å)

0.71073

0.71073

0.71073

0.71073

0.71073

0.71073

0.71073

0.71073

0.71073

crystal system

monoclinic

monoclinic

triclinic

triclinic

triclinic

monoclinic

monoclinic

triclinic

triclinic

space group

P 21/n

C 2/c

P -1

P -1

P -1

P 21/n

P 21/n

P -1

P -1

a (Å)

8.590(1)

12.595(4)

10.034(1)

10.247(1)

9.147(1)

16.117(5)

14.018(1)

6.796(1)

11.394(6)

b (Å)

9.162(1)

11.220(4)

15.285(1)

11.786(1)

10.091(1)

8.978(2)

7.025(1)

9.143(2)

14.357(9)

c (Å)

11.199(1)

19.450(7)

18.421(2)

14.209(1)

17.097(3)

22.390(6)

19.466(1)

11.838(3)

14.395(8)

α (°)

90

90

67.73(1)

74.78(12)

93.39(1)

90

90

100.72(1)

101.55(1)

β (°)

96.91(1)

102.05(1)

87.02(1)

76.18(1)

91.55(1)

110.86(1)

104.87(1)

96.44(1)

112.43(1)

λ (°)

90

90

77.36(1)

69.71(1)

99.94(1)

90

90

96.51(1)

101.04(1)

V (Å3)

875.1(3)

2688.1(17)

2549.8(5)

1532.51(18)

1550.7(5)

3027.4(15)

1853.06(17)

711.4(3)

2037(2)

Z

2

4

1

2

2

4

4

1

2

ρcalc. (gcm-3)

1.398

1.594

1.479

1.636

1.492

1.520

1.752

1.530

1.296

µ (mm-1)

0.093

0.814

0.575

0.783

0.619

0.629

1.216

0.665

0.663

F000

384

1296

1179

764

718

1436

976

339

820

cryst. size (mm)

0.26x0.06x0.06

0.34x0.25x0.24

0.20x0.15x0.13

0.25x0.25x0.20

0.30x0.25x0.10

0.35x0.18x0.12

0.15x0.12x0.10

0.70x0.36x0.26

0.28x0.12x0.08

θrange (°)

2.83 - 25.86

2.45 - 25.70

1.19 – 25.67

1.50 - 25.99

2.05 - 25.68

1.35 - 26.00

2.06 - 25.50

1.76 - 25.99

1.84 - 24.71

miller index ranges

-10≤h≤9

-15≤h≤15

-12≤h≤12

-12≤h≤11

-11≤h≤11

-19≤h≤18

-16≤h≤16

-8≤h≤7

-13≤h≤13

-11≤k≤11

-13≤k≤13

-18≤k≤18

-14≤k≤14

-12≤k≤12

-11≤k≤10

-8≤k≤8

-11≤k≤11

-16≤k≤16

-13≤l≤13

-23≤l≤19

-22≤l≤22

-17≤l≤17

0≤l≤20

-27≤l≤27

-23≤l≤22

-14≤l≤14

-16≤l≤16

reflections collected

10902

16430

65266

19780

5862

36846

19865

9138

20348

independent reflections

1701

2562

9679

5959

5862

5930

3447

2772

6891

Rint

0.0338

0.0214

0.0815

0.019

0.0574

0.1669

0.0174

0.0117

0.0929

completeness to θmax (%)

99.90%

99.90

100

99.50

99.70

99.80

100

99.30

99.20

data / restraints /parameters

1701 / 0 / 127

2562 / 0 / 188

9679 / 0 / 686

5959 / 3 / 442

5862 / 407 / 444

5930 / 0 / 436

3447 / 242 / 262

2772 / 8 / 225

6891 / 867 / 498

goodness-of-fit on F2

1.038

1.104

1.103

1.202

1.042

0.954

1.054

1.165

1.076

final R indices [I>2σ(I)]

R1 = 0.0376

R1 = 0.0532

R1 = 0.0571

R1 = 0.0235

R1 = 0.0790

R1 = 0.0830

R1 = 0.018

R1 = 0.0330

R1 = 0.0979

wR2 = 0.0916

wR2 = 0.1547

wR2 = 0.1659

wR2 = 0.0705

wR2 = 0.2103

wR2 = 0.1837

wR2 = 0.0481

wR2 = 0.0981

wR2 = 0.2748

R1 = 0.0627

R1 = 0.0566

R1 = 0.0800

R1 = 0.0278

R1 = 0.0908

R1 = 0.1523

R1 = 0.0198

R1 = 0.0354

R1 = 0.1582

wR2 = 0.1009

wR2 = 0.1572

wR2 = 0.1841

wR2 = 0.0893

wR2 = 0.2240

wR2 = 0.2213

wR2 = 0.488

wR2 = 0.1081

wR2 = 0.3098

0.148 and -0.138

1.039 and -0.781

0.958 and -0.876

0.586 and -0.605

1.756 and -1.152

0.904 and -1.244

0.281 and -0.380

0.386 and -0.419

1.284 and -0.742

R indices (all data) largest diff. peak and hole (e Å-3)


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central naphthyl spacer. The N atoms of the terminal pyridyl rings are disposed in trans conformation. In the crystal structure, the amide functionality is involved in hydrogen bonding via N-H···N interactions with the pyridyl N atoms of the neighboring molecules resulting in a herringbone packing when viewed down c-axis (Fig. 1)

Figure 2. Crystal structure illustration of CP1; (a) ORTEP plot (30% probability level); (b) packing of 1D-chains viewed down aaxis (CH3CN is shown in ball and stick model in pink, AgI – green ball).

Figure 1. Crystal structure illustration of 3-bpna; (a) ORTEP plot (30% probability level); (b) herringbone arrangement due to N– H···N hydrogen bonding interactions, viewing down c-axis.

Crystal structure of [{Ag0.5(µ-3-bpna)}0.5·0.5BF4·CH3CN] α (CP1) The crystal of CP1 belongs to the centrosymmetric monoclinic space group C2/c. The asymmetric unit consists of half of AgI located on an inversion center, half of 3-bpna molecule whose central naphthyl ring resides on an inversion center, half of BF4‾ anion (located on a 2-fold), and a fully occupied CH3CN molecule. The angle between the planes of terminal pyridyl moieties and the central naphthyl spacer is 5.82° indicating that 3-bpna ligand is reasonably planar. The metal center AgI displays a linear coordination geometry wherein the coordinating sites are occupied by the pyridyl N atoms of 3-bpna forming 1D CPic chain propagating approximately along the diagonal of ab plane. One of the fluorine atoms (F2) of BF4‾ anion is disordered and modelled over two positions. The >C=O of amide functionality is not involved in any intermolecular hydrogen bonding interaction. However, the N–H of the amide is involved in hydrogen bonding with the BF4‾ anion that bridges adjacent 1D polymeric chains skewed at 52.8°, and such packing of the 1D chains results in void space occupied by the lattice occluded solvent molecule CH3CN stabilized by weak C–H···N hydrogen bond (table S2). In addition, the 3-bpna also experience π···π interactions, with interplanar distances of 3.611 Å between the pyridine and naphthyl rings (Fig. 2).

Crystal structure of [{(H2O)Co1.5(µ-3-bpna)1.5(µbtc)}·3DMF·3H2O] α (CP2) The CP CP2 crystallizes in the centrosymmetric triclinic space group P-1. The asymmetric unit consists of two CoII metal centers (one fully occupied and the other half occupied as it sits on a center of inversion), one btc, two 3-bpna ligands (one fully occupied and the other half occupied as the central naphthyl moiety sits on an inversion center), one coordinated aqua ligand, three lattice occluded DMF molecules and three solvate water molecules. The ligand 3-bpna is found to be significantly nonplanar as evident from the dihedral angles (50.8° and 58.9°) involving the terminal pyridyl rings and the central naphthyl moiety. Both the metal centers display octahedral geometry; while the fully occupied CoII center displays slightly distorted octahedral geometry, the other one show a perfect octahedral geometry owing to its special position (center of inversion). The axial sites were coordinated by the pyridyl N atoms of the ligand 3-bpna, the equatorial positions are occupied by O atoms of the carboxylate and water molecules. The tricarboxylate co-ligand namely btc coordinates through its carboxylate O atoms to CoII metal centers resulting in a 2D sheets propagating parallel to ac-plane. The 2D sheets are further threaded by the 3-bpna ligands via pyridyl N–Co coordination resulting in an overall 3D network. The void space with the 3D network are occupied by the solvate DMF and water molecules sustained by various hydrogen bonding of the type N–H···O and O–H···O. Topological analysis60 reveals that the network present in CP2 is a 3,4,6-connected net also known as sqc130 topology (Fig. 3). A similar 3,4,6-connected topology based on cadmium phenylenediacetate isonicotinate CP has been reported recently.61



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Figure 3. Crystal structure illustration of CP2; (a) ORTEP plot (50% probability level); (b) coordination mode of btc; (c) topological representation of the 3D network found in CP2 viewing down b-axis (topological figures were drawn using X-Seed62).

Crystal structure of [{Cd(µ-3-bpna)(µ-hbtc)}·CH3OH·2H2O] α (CP3) The CP CP3 crystallizes in the centrosymmetric triclinic space group P-1. The asymmetric unit consists of one CdII, one hbtc2–, one 3-bpna, two lattice occluded water molecules and one methanol. The ligand 3-bpna is found be nearly planar as evident from the dihedral angles involving the pyridyl moieties and the central naphthyl ring (12.45° and 17.82°). The CdII metal center displays distorted octahedral geometry wherein the equatorial positions are occupied by the carboxylate O atoms and the axial sites are coordinated by the pyridyl N atoms. The monoprotonated Hbtc is found to coordinate to the adjacent CdII metal centers resulting a 1D looped chain; such chains are further bridged by the bis-pyridyl ligand 3-bpna resulting in an overall 2D coordination network. The 2D sheets are packed in parallel fashion further sustained by intersheet N–H···O interactions involving the amide N–H and >C=O of the COOH moiety of Hbtc and π···π stacking (3.7933.922 Å, between the pyridyl···pyridyl, naphthyl···naphthyl and naphthyl···pyridyl rings). The solvate CH3OH is found be hydrogen bonded with amide N–H and carboxylate via N– H···O and O–H···O interactions, respectively. Two solvate water molecules are hydrogen bonded with each other via O– H···O interactions; one of the water molecules further forms hydrogen bond with amide carbonyl and COOH of Hbtc. The overall network may best described as 4-connected uninodal framework as suggested by topological analysis60 (Fig. 4).

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Figure 4. Crystal structure illustration of CP3; (a) ORTEP plot (50% probability level); (b) coordination mode of Hbtc for CP3; (c) packing of 2D sheets; (d) topological representation of the 2D network found in CP3 (rods in magenta colour, topological figures were drawn using X-Seed62).

Crystal structure of [{Co(µ-3-bpna)(µ-ipa)}·DMF·2H2O] α (CP4) The CP CP4 crystallizes in the centrosymmetric triclinic space group P-1. The asymmetric unit consists of one CoII, one isophthalate (ipa), one 3-bpna, two lattice occluded water molecules and one unligated DMF. The ligand 3-bpna is found to be significantly nonplanar as evident from the dihedral angles (39.7° and 44.8°) involving the terminal pyridyl rings and the central naphthyl moiety. The CoII metal center displays distorted octahedral geometry wherein the equatorial positions are occupied by the carboxylate O atoms and the axial sites are coordinated by the pyridyl N atoms.

Figure 5. Crystal structure illustration of CP4; (a) ORTEP plot (50% probability level); (b) packing of 2D sheets viewing down b-axis; (c) topological representation of the 2D network found in CP4 (rods in magenta colour, topological figures were drawn using X-Seed62).

The fully deprotonated ipa is found to coordinate to the adjacent CoII metal centers resulting a 1D looped chain; such


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chains are further bridged by the bis-pyridyl ligand 3-bpna resulting in an overall 2D coordination network. The 2D sheets are packed in parallel fashion resulting in voids that were occupied by the solvate water and DMF molecules sustained N–H···O interactions involving the amide N–H. The overall network may best described as 4-connected uninodal framework as suggested by topological analysis60 (Fig. 5). Crystal structural of [{Co(µ-3-bpna)(µ-1,3-pda)}·DMF] α (CP5) The CP CP5 crystallizes in the centrosymmetric monoclinic space group P21/n. The asymmetric unit consists of a CoII, one 1,3-pda, one 3-bpna molecule and one occluded DMF molecule. The ligand 3-bpna is found to be significantly deviated from planarity as evident from the dihedral angles involving the pyridyl moieties and the central naphthyl ring (3.6° and 20.8°). The CoII metal center displays distorted octahedral geometry wherein the equatorial positions are occupied by the carboxylate O atoms and the axial sites are coordinated by the pyridyl N atoms. Remarkably, the dicarboxylate 1,3-pda ligand adopts cis conformations rather than a much more stable and usually observed trans conformation;63,64 1,3-pda displays an tridentate bridging mode with one carboxylate chelating (µ1-η1:η1) to one CoII, whilst the other carboxylate bridges two CoII atoms with each oxygen atom acting as a monodentate donor (µ2-η1:η1). Such coordination mode results in a 1D looped chain topology that are further bridged by the bispyridyl ligand 3-bpna producing an overall 2D coordination network. The 2D sheets are packed in parallel fashion. The interstitial space is occupied by the solvate DMF sustained N– H···O and C–H···π (Cg···H–C=2.787 Å) interactions involving the amide N–H and DMF >C=O, and DMF methyl and the aromatic moiety of 1,3-pda, respectively. The overall network may best be described as 4-connected uninodal framework as suggested by topological analysis60 (Fig. 6).

Figure 6. Crystal structure illustration of CP5; (a) ORTEP plot (30% probability level); (b) 1D looped chain generated due to Co1,3-pda coordination mode; (c) topological representation of the 2D network found in CP5 (rods in magenta colour, topological figures were drawn using X-Seed62).

Crystal structural of [Cd(µ-3-bpna)0.5(µ-1,3-pda)] α (CP6) The CP CP6 crystallizes in the centrosymmetric monoclinic space group P21/n. The asymmetric unit consists of a CdII, one 1,3-pda moiety and half of 3-bpna molecule (located on an inversion center). The ligand 3-bpna is found be nonplanar as evident from the dihedral angles involving the pyridyl moieties and the central naphthyl ring (20.9°). The CdII metal center displays distorted pentagonal bipyramidal geometry wherein the equatorial positions are occupied by the carboxylate O atoms and the axial sites are coordinated by the pyridyl N atom and one of the carboxylate O atoms. 1,3-pda displays the usually observed trans conformation (contrary to that observed

in CP5) and is involved trans-tetradentate bridging mode with one acetate arm chelating (µ1-η1:η1) to one CdII center, whilst the other arm chelates as well as bridges (µ3-η2:η2) three CdII metal centers resulting in 2D network. The bis-pyridyl ligand 3-bpna is found to bridge the 2D sheets packed in parallel fashion resulting in an overall 3D network. The amide N–H is found to be involved in hydrogen bonding with the carboxylate O via N–H···O interactions. The overall network may best be described as 5-connected uninodal new topology as suggested by topological analysis60 (Fig. 7).

Figure 7. Crystal structure illustration of CP6; (a) ORTEP plot (50% probability level) and polyhedral view for CdII coordination environment; (b) coordination modes of 1,3-pda; (c) 2D sheet; (d) topological representation of the 3D network found in CP6 (topological figures were drawn using X-Seed62).

Crystal structure of [(H2O)Co0.5(µ-3-bpna)0.5(µ-1,4-pda)0.5] α (CP7) The CP CP7 crystallizes in the centrosymmetric triclinic space group P-1. The asymmetric unit consists of half of CoII, half of a 1,4-pda and half of a 3-bpna ligand – all reside on inversion center, and a fully occupied aqua ligand. The ligand 3-bpna is found to be almost planar as evident from the dihedral angles involving the pyridyl moieties and the central naphthyl ring 3.7°). The CoII metal center displays a perfect octahedral geometry owing to its special position (center of inversion) wherein the equatorial positions are occupied by the carboxylate O atoms and coordinated water molecules, and the axial sites are coordinated by the pyridyl N atoms. 1,4-pda ligand bridges CoII atoms in trans coordination fashion to form a 1D chain which further tethered by 3-bpna ligands to form 2D corrugated (4,4) rhomboid network. Parallel corrugated 2D sheets64 stack in an interdigitating fashion sustained inter-sheet N–H···O interactions involving the amide N–H and carboxylate O and O–H···O interactions involving the metal bound water and carboxylate. The overall network may best be described as 4-connected uninodal network as suggested by topological analysis60 (Fig. 8).



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Figure 8. Crystal structure illustration of CP7; (a) ORTEP plot (50% probability level); (b) packing 2D sheets; (c) topological representation of the 2D network found in CP7 (topological figures were drawn using X-Seed62).

Crystal structure of [{Zn(µ-3-bpna)(µ-oba)}·DMF·2H2O] α (CP8) The CP CP8 crystallizes in the triclinic space group P-1. The asymmetric unit consists of a ZnII, one 4,4′-oxybis-benzoate (oba), one 3-bpna, two lattice occluded water molecules and one DMF molecule. The ligand 3-bpna is found be nonplanar as evident from the dihedral angles involving the pyridyl moieties and the central naphthyl ring (61.57° and 35.57°). The ZnII metal center displays square pyramidal coordination geometry coordinated by carboxylate O atoms and the pyridyl N atoms. The flexible oba ligand bridges neighboring ZnII metal center resulting in 1D chain which are further threaded by the bispyridyl ligand 3-bpna producing a corrugated 2D sheet. The adjacent sheets are intercalated into three-dimensional layered architecture through strong aromatic π···π stacking interactions between 3-bpna ligands (Cg···Cg = 3.447 Å). Interestingly the adjacent 2D sheets are arranged in ABAB·· fashion. The interstitial space within the network is occupied by the solvate water and DMF molecules sustained by hydrogen bonding interactions; while the water molecule is involved in hydrogen bonding with the amide N–H, the DMF takes part in hydrogen bonding interactions with the water. The overall network may best described as uninodal 4-connected network as suggested by topological analysis60 (Fig. 9).

Figure 9. Crystal structure illustration of CP8; (a) ORTEP plot (50% probability level); (b) schematic diagram for the interdigitated 2d sheets in ABAB… fashion; (c) packing diagram of the 2D sheets with the voids occupied solvents; (d) topological representation of the 2D network found in CP8 (topological figures were drawn using X-Seed62).

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The foregoing structural description of the free ligand and all the CPs reveals the following (Table 2): The bispyridyl ligand displays trans ligating topology with respect to the terminal pyridyl moieties in all the crystal structures of the CPs as well as the free ligand (Figure S1). The amide functionality is found to be anti-periplanar in all structures except for CP6 and CP8 (syn-periplanar). In most of the cases, the dihedral angle involving the terminal pyridyl rings and the central naphthyl moiety indicates significant non-planarity of the ligand 3bpna. In the mixed ligand CPs, the carboxylate co-ligands display various coordination modes that include bidentate, tridentate and tetradentate depending on how the carboxylate O takes part in coordination. Except for CP6, the metal centers displays perfect to distorted octahedral geometry wherein the equatorial positions are mostly occupied the carboxylate O atoms. Threading by the pyridyl N atoms of 3-bpna ligand to the axial sites of the octahedral metal center leads mainly to 2D coordination architecture except in CP2 and CP6; these two CPs display 3D coordination network. The most important feature of the CPs reported herein, as envisaged, is that majority of them occluded solvent in their crystal lattice; only CP6 and CP7 did not occlude any solvent in the crystal structures. It may be mentioned here naphthyl based bis-pyridyl-bisamide ligands having similar structural features to 3-bpna also produced lattice occluded coordination polymers in mixed ligand systems.65,66 Powder X-ray diffraction (PXRD) patterns are provided in the supplementary material for 3-bpna and CP1-CP8 (Figure S2). Except CP1, in all the cases, the experimental patterns agree well with the simulated patterns indicating the phase purity of the bulk material. The experimental PXRD pattern of CP1 does exhibit a few ‘extra’ peaks, which may indicate the presence of a small crystalline impurity. The lattice occluded solvent content in the single crystal structures of all the CPs was further verified by TGA (Figure S3-S10, supporting information). Since the ligand 3-bpna contained a naphthalene moiety which is a known fluorophore,67 we studied the photophysical properties of the free ligand 3-bpna and a few selected CPs namely CP2, CP5 and CP3 in the solid state. The bis-pyridylbis-amide ligand 3-bpna, displays a broad emission band centered around ca. 415 nm (excitation wavelength, λex=330 nm), which can be ascribed to the intra-ligand or ligand-ligand π-π* or n-π* transitions. The emission spectrum of CP3 (excitation wavelength, (λex=300 nm) also appeared to be of similar feature as that of the free ligand displaying a broad emission band centered around ca. 435 nm. Since the photoluminescent d10 metal center CdII is quite far away (ca. 10 Å) from the fluorophore core of 3-bpna in the crystal structure of CP3, it understandably did not affect the overall fluorescence. On the other hand, the emission spectra of CP2 and CP5 (excitation wavelength, (λex=300 nm) appeared to have sharp characteristic displaying a peak centered around ca. 380 nm with satellite peaks at ca. 370 and 400 nm. It is clear that in these cases, the d7 metal center CoII was unable to quench the luminescence68 because of its far away distance (ca. 10 Å) from the naphthyl moiety in the respective crystal structures of the CPs (Fig. S11, supporting information).


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Table 2 Crystallographic and structural information

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Ligand and CPs

Space group

Asymmetric unit content

Relative orientation of pyridyl N atoms

Relative orientation of amide group

Dihedral angle between the terminal pyridyl & central naphthyl rings

3-bpna

P21/n

half of 3-bpna

trans

anti-periplanar

13.20°

CP1

C 2/c

trans

anti-periplanar

5.82°

1D

CP2

P -1

half of 3-bpna, 0.5 AgI, 0.5 BF4‾, 1 solvate CH3CN 1.5 CoII, 1.5 of 3bpna, 1 btc, 1 coord H2O, 3 solvate DMF, 3 solvate H2O

trans

anti-periplanar

50.71°, 58.97°

3D

CP3

P -1

1 CdII, one 3-bpna, 1hbtc, 2 solvate H2O, 1 solvate MeOH

trans

anti-periplanar

17.82°, 12.46°

2D

CP4

P -1

trans

anti-periplanar

39.71°, 35.11°

2D

CP5

P 21/n

1 CoII, 1 of 3-bpna, 1 ipa, 1 solvate DMF, 2 solvate H2O 1 CoII, 1 of 3-bpna, 1 of 1,3-pda, 1 solvate DMF

trans

anti-periplanar

21.42°, 1.82°

2D

CP6

P 21/n

1 CdII, half of 3-bpna, 1 of 1,3-pda,

trans

anti-periplanar

20.93°

3D

0.5 CoII, 0.5 of 3bpna, 0.5 of 1,4-pda, 1 coord H2O 1 ZnII, 1 of 3-bpna, 1 oba, 1 solvate DMF, 2 solvate H2O

trans

anti-periplanar

3.75°

2D

trans

anti-periplanar

61.57°, 35.57°

2D

CP7

P -1

CP8

P -1

Gelation studies Since majority of the CPs turned out to be inclusion materials as envisaged, we decided to scan all the CPs for potential metallogelation. Before that, we scanned the ligand 3-bpna for gelation as the amide functionality is reported to be gel producing moiety. However, 3-bpna turned out to be a nongelator when scanned with various solvents (both polar and nonpolar). Metallogelation scanning revealed that the reactants of majority of the CPs failed to produce metallogels with the target solvent system DMF/water. Only the reactants of CP1 and CP2 did produce metallogels with DMF/water. The minimum gelator concentrations (MGCs) were found to be 3.4 and 4.0 % for CP1 and CP2, respectively considering all the reactants. In a typical experiment, DMF solution of the ligand(s) was mixed with aqueous solution of the metal salt at room temperature so that the metal:ligand molar ratio was 1:1 and the resulting DMF/water ratio was 2:3 v/v. The gel was formed almost instantaneously, which was visually confirmed by the tube inversion test. The visco-elastic nature of the gels was further confirmed by rheology. The amplitude sweep experiments wherein elastic modulus (G') and viscous modulus (G'') were plotted against the strain applied, suggested that a strain of 0.1% was appropriate for the frequency sweep experiments. Both CP1 and CP2 metallogels displayed expected behavior for visco-elastic materials like gels; in both the cases, G' was greater than G'' throughout the frequency range specially, in the longer time scale – typical of visco-elastic materials like gels.

Network topology

Hydrogen bonding involving the amide moiety

Namide–H···F [N···F=3.083(5) Å; ∠N–H···F=162.1°] Namide···Npy [N···N=3.021(1) Å; ∠N–H···N=172.1°] N–H⋯Osolvate [N⋯O = 2.865(5)-2.879(4) Å; ∠N–H⋯O = 144-154.9°] O–H⋯O [O⋯O = 2.77(4)2.803(6) Å; ∠O–H⋯O = 142.6163°] N–H⋯Osolvate [N⋯O = 2.825(3) Å; ∠N–H⋯O = 141.8°] O–H⋯O [O⋯O = 2.556(3)2.729(3) Å; ∠O–H⋯O = 170(4)-176.1°] N–H⋯Osolvate [N⋯O = 2.878(8)-2.981(16) Å; ∠N– H⋯O = 160-161.4°] [N⋯O = N–H⋯Osolvate 3.081(6) Å; ∠N–H⋯O = 157°] N–H⋯Ocarboxy [N⋯O = 3.007(7) Å; ∠N–H⋯O = 162.7°] N–H⋯Ocarboxy [N⋯O = 2.934(2) Å; ∠N–H⋯O = 163.6°] N–H⋯Ocarboxy [N⋯O = 3.057(2) Å; ∠N–H⋯O = 155.7°] N–H⋯Osolvate [N⋯O = 2.970(12) Å; ∠N–H⋯O = 156°] N–H⋯Ocarboxy [N⋯O = 2.908(8) Å; ∠N–H⋯O = 159.7°]

Lattice occluded solvent molecules per asymmetric unit

Nil 1 CH3CN

3 DMF 3 H2O

2 H2O 1 CH3OH

1 DMF 2 H2O 1 DMF

Nil 1 H2O

1 DMF 2 H2O

The morphology of the gel fibers was studied by transition electron microscopy (TEM). The dried gels prepared by drop casting a suspension of gel in water on a TEM grid revealed the existence of highly entangled network of 1D tape type fibers. Understandably these fibers formed by the spontaneous self-assembly involving the organic linkers and the metal centers were capable of immobilizing the solvent molecules resulting in the metallogels. Since AgI is prone to photochemical reduction to produce Ag0 nanoparticle (hereafter AgNP) under suitable conditions, the gel obtained from the reactant of CP1 was exposed to sunlight for a day. It was observed that the color of the gel turned brown from white indicating AgNP formation. The tiny particles (3-10 nm) seen in the TEM image of the dried gel of CP1 presumably were the AgNPs. Selected area electron diffraction (SAED) performed on the TEM machine revealed that these particles were crystalline as they produced well-ordered diffraction spots. Existence of AgNPs was finally confirmed by the surface plasmon resonance peak at ~470 nm in the UV-vis spectrum of the suspended xerogel of CP1 in DMSO. Formation of metal nanoparticle including AgNPs within gel bed has earlier been reported by us22 and others.38 Attempt to gain insights into the gel network structure by powder X-ray diffraction studies was not successful because both the concerned CPs (CP1 and CP2) were lattice occluded molecular solids which were susceptible towards desolvation leading to change and/or collapse of the crystal lattice. Moreover, in the case CP1, Ag nanoparticles were formed which



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meant partial degradation of the coordination network leading to different PXRD patterns (Fig. S12).

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logical approach adopted herein to gain access to metallogels was worthwhile.

ASSOCIATED CONTENT Supporting Information CCDC numbers 1017718-1017721 and 1028834-1028838 contains the supplementary crystallographic data for this paper. This data can be obtained free of charge via www. ccdc.cam.ac.uk/data_request/cif [or from the Cambridge Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge CB2 1EZ, U.K.; fax: +44(0)1223-336033; e-mail: [email protected]]. Additional figures, crystallographic parameters (bond lengths and bond angles), hydrogen bonding table is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *Email: [email protected]. Notes The authors declare no competing financial interest.

Figure 10. Amplitude sweep and frequency sweep experiments of the metallogels for CP1 (a) and CP2 (c). TEM micrograph of the xerogels; (b) for CP1 in DMSO/water (2:3 v/v); (d) for CP2 in DMF/water (2:3 v/v). Inset: optical images of the gels. TEM images were taken on freshly prepared gels after drop casting on 300 mesh carbon coated copper grid followed drying at RT. (e) Selected area electron diffraction (SAED) photograph of AgNPs. (f) Characteristic surface plasmon peak in the UV/Vis spectrum of AgNPs derived from metallogel gel CP1.

Conclusion A new, hitherto unexplored, flexible ligand equipped with hydrogen bonding functionality (amide) namely 3-bpna was explored to get an access to a new series of coordination polymers by reacting it with various metal salts and carboxylate co-ligands. As envisaged, majority of the coordination polymers turned out to be lattice occluded molecular solids; various hydrogen bonding capable solvent molecules (DMF/water/MeOH/MeCN) were found to be occluded within the interstitial space of the coordination networks sustained by hydrogen bonding with the amide functionality and/or metal bound water molecules. Contrary to our expectation, the reactants of the CPs in majority of the cases failed to produce metallogel with DMF/water or DMSO/water; only in the cases of CP1 and CP2, the expected metallogels were formed. Ultimately a gel is formed only when the gel network is able to immobilize the target solvent via capillary force action or surface tension that solely depends on the surface compatibility between the gel network and the solvent molecules. Thus, a gel network characteristics present in the structure of the gelator molecule does not necessarily ensure gelation. The reason for other CPs (CP3-CP8) being nongelator must be because of the surface incompatibility of network structure and the target solvent molecules. These results clearly indicate that much understanding is still needed in the molecular level in order to be able to design metallogelators a priori. Nevertheless, the

ACKNOWLEDGMENT KN thanks CSIR, New Delhi for a Junior Research Fellowship. AH thanks DST for a research associate position. PD thanks DST for financial support. SXRD data were collected at the DBT-funded X-ray diffraction facility under the CEIB program (BT/01/CEIB/11/v/13) in the Department of Organic Chemistry, IACS, Kolkata. REFERENCES (1) Zhou, H.-C.; Long, J. R.; Yaghi, O. M. Chem. Rev. 2012, 112, 673–674. (2) Du, M.; Li, C. P.; Liu, C. Sen; Fang, S. M. Coord. Chem. Rev. 2013, 257, 1282–1305. (3) Adarsh, N. N.; Dastidar, P. Chem. Soc. Rev. 2012, 41, 3039–3060. (4) Batten, S. R.; Champness, N. R.; Chen, X.-M.; GarciaMartinez, J.; Kitagawa, S.; Öhrström, L.; O’Keeffe, M.; Suh, M. P.; Reedijk, J. CrystEngComm 2012, 14, 3001–3004. (5) Hoskins, B. F.; Robson, R. J. Am. Chem. Soc. 1989, 111, 5962–5964. (6) Murray, L. J.; Dincă, M.; Long, J. R. Chem. Soc. Rev. 2009, 38, 1294–1314. (7) Furukawa, H.; Yaghi, O. M. J. Am. Chem. Soc. 2009, 131, 8875–8883. (8) Adarsh, N. N.; Kumar, D. K.; Dastidar, P. CrystEngComm 2009, 11, 796–802. (9) Rajbanshi, A.; Moyer, B. A.; Custelcean, R. Cryst. Growth Des. 2011, 11, 2702–2706. (10) Custelcean, R.; Bock, A.; Moyer, B. A. J. Am. Chem. Soc. 2010, 132, 7177–7185. (11) Banerjee, S.; Dastidar, P. Cryst. Growth Des. 2011, 11, 5592–5597. (12) Corma, A.; Garcia, H.; Llabrés i Xamena, F. X. Chem. Rev. 2010, 110, 4606–4655. (13) Yoon, M.; Srirambalaji, R.; Kim, K. Chem. Rev. 2012, 112, 1196–1231. (14) Lee, J.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S. T.; Hupp, J. T. Chem. Soc. Rev. 2009, 38, 1450–1459. (15) Zhang, W.; Xiong, R. Chem. Rev. 2012, 112, 1163–1195.


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Metallogels and Silver Nanoparticles Generated from a Series of Transition Metal Based Coordination Polymers Derived from a New Bis-pyridyl-Bis-amide Ligand and various carboxylates Karabi Nath, Ahmad Husain and Parthasarathi Dastidar*. SYNOPSIS TOC. A rational approach has been adopted to synthesize a new series of coordination polymers derived from 3-bpna under various conditions. Two such coordination polymers (CP1 and CP2) produced metallogels. Ag nanoparticles have also been isolated from one such metallogel.


Metallogels and Silver Nanoparticles Generated ... - ACS Publications

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