Author's Accepted Manuscript

Electrical conductivity and luminescenceproperties of two silver(I) coordination poly-mers with heterocyclic nitrogen ligands

Abhinandan Rana, Swapan Kumar Jana, TanusriPal, Horst Puschmann, Ennio Zangrando, Su-dipta Dalai

PII: S0022-4596(14)00184-4DOI: http://dx.doi.org/10.1016/j.jssc.2014.04.026Reference: YJSSC18461

To appear in: Journal of Solid State Chemistry

Received date: 3 December 2013Revised date: 25 April 2014Accepted date: 28 April 2014

Cite this article as: Abhinandan Rana, Swapan Kumar Jana, Tanusri Pal, HorstPuschmann, Ennio Zangrando, Sudipta Dalai, Electrical conductivity andluminescence properties of two silver(I) coordination polymers with hetero-cyclic nitrogen ligands, Journal of Solid State Chemistry, http://dx.doi.org/10.1016/j.jssc.2014.04.026

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Electrical conductivity and luminescence properties of two silver(I)

coordination polymers with heterocyclic nitrogen ligands

Abhinandan Rana a, Swapan Kumar Jana a, Tanusri Pal b, Horst Puschmann c,

Ennio Zangrando d, Sudipta Dalai a,*

a Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore 721

102, West Bengal, India

b Department of Physics, Midnapore College, Midnapore 721 101, West Bengal, India

c Department of Chemistry, Durham University, Durham DH1 3LE, UK

d Dipartimento di Scienze Chimiche e Farmaceutiche, University of Trieste, 34127 Trieste, Italy

*Corresponding author.

E-mail address: sudipta@mail.vidyasagar.ac.in / icsdalai@gmail.com; Fax. No.: 91 3222 275297

(S. Dalai)

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ABSTRACT

The synthesis and X-ray structural characterization of two novel silver(I) coordination polymers,

[Ag(NO3)(quin)]n (1) and [Ag8(HL)2(H2O)4(mpyz)].3H2O (2) are reported, where quin = 5,6,7,8-

tetrahydroquinoxaline, H6L=cyclohexane-1,2,3,4,5,6-hexacarboxylic acid and mpyz = 2-methyl

pyrazine. The single crystal diffraction analyses showed that complex 1 is a 2D layered structure,

while 2 presents a 3D polymeric architecture. In complex 2 the network is stabilized by

argentophilic interactions and hydrogen bonding. Electrical conductivity of order 3x10-4 Scm-1

(1) and 1.6x10-4 Scm-1 (2) is measured on thin film specimen at room temperature. The

photoluminescence and thermal properties of the complexes have also been studied.

Keywords: Ag-coordination polymer; electrical conductivity; luminescence; argentophilic

interaction; 5,6,7,8-tetrahydroquinoxaline; cyclohexane-1,2,3,4,5,6-hexacarboxylic acid; 2-

methyl pyrazine.

1 Introduction

In the last two decades, the research and development of metal�organic frameworks

(MOFs), also designated as coordination polymers or coordination networks, have shown a

significant progress. [1] At the beginning, the interest was mainly focused on their exceptional

topologies, but at present, it is mostly associated with their potential applicability in different

technological and industrial areas, like gas adsorption and capture or storage, [2] heterogeneous

catalysis, [3] biomedicine, [4] nanotechnology, [5] sensors [6] etc. MOFs are basically

coordination complexes with infinite one-, two-, or three – dimensional crystalline structures.

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The formation of such complexes, which are of no doubt of technological impact, is mainly

governed by the coordination requirements of metal centers and by the nature of the

multifunctional ligands or counter ions. Consequently the formation of novel MOF materials can

be tuned by adjustment of building blocks. For this reason a large variety of aromatic carboxylate

ligands, such ascyclohexane-1,2- or 1,4-dicarboxylic acid [7-10], cyclohexane-1,2,3,4,5,6-

hexacarboxylic acid [11-13], tetrahydrofuran-2,3,4,5-tetracarboxylic acid [14-15] and

cyclohexane-1,2,4,5-tetracarboxylic acid, [16] has been successfully employed for the

construction of metal coordination polymers. In addition a range of rigid bridging aromatic N-

donors such as pyrazine [17-18], quinoxaline [19] have been included with the aim to modulate

the network topology. In coordination chemistry, silver ion has been widely applied due to its

soft acceptor characteristic as well as for its relatively flexible coordination sphere. Although

Ag(I) metal ion is supposed to have a strong inclination for linear coordination geometry, the

majority of solid-state structures of silver(I) complexes reported exhibits different coordination

numbers, three, four, and even larger in a variety of cases.[20] In this context and in addition for

the ability to form Ag···Ag ligand unsupported interactions, silver(I) is an ideal metal ion to build

coordination polymers of unpredictable topology.[21] A key property is that the d10 configuration

of Ag(I) ion imposes few structural requirements on the surrounding ligands and anion entities.

[22]

In continuation to our study on Ag(I) compounds [23-27] herein we report the synthesis,

crystal structure, thermal, luminescence and electrical property of two new silver(I) coordination

polymers, [Ag(NO3)(quin)]n (1) and [Ag8(HL)2(H2O)4(mpyz)].3H2O (2) where quin = 5,6,7,8-

tetrahydroquinoxaline, H6L = cyclohexane-1,2,3,4,5,6-hexacarboxylic acid and mpyz = 2-methyl

pyrazine. The structures, determined by X-ray single crystal diffraction analysis, show that

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complex 1 is a 2D coordination polymer with a rectangular network having quinoxaline and

nitrate anions as edges. Complex 2 is a 3D architecture stabilized by argentophilic interactions

comprising four crystallographic independent silver ions. It is well-known that electrical

conductivity of classical covalent polymers has attracted the interest of many researchers in

material science. However, this property in MOFs does not appear to be widely studied. [28]

2 Experimental

2.1 Materials and Instrumentation

Silver nitrate was purchased from Merck. 5,6,7,8-Tetrahydroquinoxaline, 2-methyl

pyrazine and cyclohexane-1,2,3,4,5,6-hexacarboxylic acid were purchased from SIGMA-

ALDRICH Inc. All the chemicals were used without any further purification.

2.2 Physical Measurements

IR spectra for 1 and 2 were recorded in a JASCO FT/IR-6200 applying ATR technique in

the range 4,000–400 cm-1. Elemental analyses (C, H, N) were carried out on a 240C Elemental

analyzer. Thermogravimetric analysis (TGA) was done under nitrogen flow (flow rate of 30 ml

min-1) with a Shimatzu DTG-60 simultaneous DTA-TG apparatus. The fluorescence spectra of

the ligand and complex were measured in the solid state at room temperature using a HITACHI

F-7000 spectrofluorimeter. The powder X-ray diffraction (PXRD) were performed with Rigaku

miniflex 600 X-ray diffractometer using CuK� radiation (�=1.5418 Å), operated at 40 kV and 20

mA, using a Cu-target tube and a monochromator. The powder sample was scanned in steps of

0.02º for a time interval of 1 sec over a 2� range of 5-50º.

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2.3 Synthesis

2.3.1 [Ag(NO3)(quin)]n (1):

A mixture of AgNO3 (84.5 mg, 0.5mmol), cyclohexane-1,2,3,4,5,6-hexacarboxylic acid

(183 mg, 0.5 mmol) and 5,6,7,8-tetrahydroquinoxaline (0.06 ml, 0.5 mmol) in 10 ml deionised

water was taken in a conical flask. The reaction mixture was reacted under ultrasonic irradiation

(60 W, 50 Hz) for about 15 min at ambient temperature to get a turbid solution. Aqueous NH3

solution (25%) was added drop-wise into the mixture with constant stirring to get a colourless

transparent solution. The resultant solution was kept in dark for slow evaporation of the solvent.

After ten days diffraction quality colourless single crystals of 1were obtained (yield, 60%). They

were washed with a small volume of cold ethanol and diethyl ether. Anal. Calc. for

C16H20Ag2N6O6(608.11): C, 31.60; H, 3.31; N, 13.82 . Found: C, 31.62; H, 3.30; N, 13.85.

IR(cm-1): 419(w), 436(w), 481(w), 531(w), 609(m), 667(m), 688(w), 719(w), 759(w), 832(w),

855(w), 905(m), 939(w), 989(w), 1073(m),1153(m), 1183(w), 1384(s), 1398(s),1435(m),

1455(w),1469(w),1505(w), 1538(w), 1557(w), 1635(s), 1651(s), 1699(w), 1732(w), 2327(w),

2359(w), 2861(w), 2938(w).

2.3.2 [Ag8(HL)2(H2O)4(mpyz)].3H2O (2)

The synthesis of 2 was performed similarly as for 1(except for the presence of

cyclohexane-1,2,3,4,5,6-hexacarboxylic acid), but 2-methyl pyrazine (0.045 ml, 0.5 mmol) was

used instead of 5,6,7,8-tetrahydroquinoxaline. Diffraction quality colourless crystals of 2 were

obtained after seven days with 58% yield. Anal. Calc. for C29H34Ag8N2O31(1769.54): C, 19.68;

H, 1.93; N, 1.58. Found: C, 19.69; H, 1.95; N, 1.59.

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IR (cm-1): 404(w), 406(w), 490(w), 523(w), 615(m), 667(m), 686(w), 720(w), 764(w), 809(w),

832(w), 904(m), 996(w), 1030(w), 1065(w), 1160(w), 1210(w), 1309(w),1384(s), 1475(w),

1504(w), 1574(s), 1631(w), 1700(w), 2329(w), 2364(m), 3443(broad).

2.4 IR study

The IR spectral analysis of compound 1 and 2 show reveals �as(OCO), �s(OCO) bands

appear at ~1635, ~1435 cm-1 for compound 1 and ~1631, ~1475 cm-1 for compound 2

respectively indicating the carboxylate involved in coordination. A broad band in the region

3200-3500 cm-1 [�(O-H)] in 2 suggesting the presence of H2O molecules [29].

2.5 X-Ray Crystallography

Data collections of 1 and 2 were carried out at 120(2) K on an Oxford Diffraction Gemini

Ultra diffractometer. Cell refinement, indexing and scaling of the data sets were done with

CrysAlisPro package, Version 1.171.35.10. [30] The structures were solved by using the

olex2.solve solution program [31] using the charge flipping algorithm and refined by the full-

matrix least-squares method based on F2 with all observed reflections [32]. In 2 the 2-

methylpyrazine is located on a center of symmetry, thus the methyl group is disordered over two

positions. In addition two residuals separated by 0.7 Å in 2 were successfully refined as water

oxygen atoms with 0.25 occupancy each (no H atoms assigned). Molecular graphics were

performed using programs Cameron [33] and Diamond Crystal Ver 3.1. [34] Crystal data and

details of refinements are given in Table 1. [CCDC number 837272 and 837271]

3. Results and Discussion

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3.1 PXRD Results

To confirm whether the crystal structures are truly representative of the bulk materials

and to check the purity of the complexes, Powder X-ray diffraction (PXRD) were carried out for

1 and 2. Experimental and computer-simulated PXRD patterns of the corresponding complexes

are shown in supplementary data (Fig. 3S). The calculate unit cell parameters of the powdered

samples of 1 and 2 respectively are a = 7.1747 Å, b= 8.9437 Å, c= 15.1414 Å, � = 95.644º, � =

95.001º, � =92.6910º, V= 961 Å3 ; and a= 7.9886 Å, b=10.2404 Å, c=13.9864 Å, � = 96.719 º, �

= 96.639 º, � =111.040 º, V= 1045.12 Å3 and agree well with the cell parameters calculated from

the single crystal data. Although a few un-indexed diffraction lines are present in the

experimental patterns and some of the lines are slightly broadened in compare with those

simulated pattern, still it can be considered that the bulk synthesized materials and the as grown

crystals are homogeneous.

3.2 Crystal structure of 1

The crystal structure of 1 exhibits a corrugated layered structure of formulation

[Ag(NO3)(quin)]n parallel to the crystallographic ab plane. The network of 4,4 topology,

depicted ion Fig. 1, is built of 1D –[Ag(quin)]n– polymers connected by nitrate anions. In the

distorted rectangular grid the metals are separated by 7.154 Å through the tetrahydroquinoxaline,

and alternatively by 6.156 Å and 5.233 Å through the nitrate connections. Table 2 reports a

selection of coordination bond lengths and angles. The two independent Ag ions are digonally

coordinated by the quinoxaline nitrogen donors with Ag-N bond distances in a range 2.2092(16)-

2.2471(16) Å and N-Ag-N bond angles of 165.76(6) and 156.03(6)°. The Ag-O connections

involving nitrate anions are longer in between 2.5707(16) and 2.8780(15) Å.

Fig. 1

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In fact the two independent nitrate anions behave in a different coordination mode: both

are bridging species but one engages all oxygen atoms to connect the metals (Fig 2). As revealed

by Fig. 1 all the cyclohexyl moieties of one layer point in the same direction, while in the

adjacent layers have a reversed orientation. The crystal structure is comparable to the

correspondent quinoxaline derivative, [19] although in that case the authors described the

complex as 1D hybrid polymer due to the Ag-ONO2 distances longer than 2.8 Å. The

intermetallic separation Ag-(quin)-Ag though the bridging connection is here of 7.154 Å, slightly

shorter than that measured in the planar quinoxaline (7.310 Å) [19] and in the 2,3-

diphenylquinoxaline (7.344 Å), [35] although in the latter for the bulky phenyl groups the

packing appears different. No stacking interaction between aromatic rings was detected and, as

evident from Fig. 1a, the pyrazine ring centroids within each layer present a slippage of ca. 2.1

Å.

3.3 Crystal structure of 2

The X-ray structural characterization has established that complex 2 is a 3D MOF

structure and each asymmetric unit comprises four silver ions, one HL molecule, and half 2-

methylpyrazine ligand (located on a center of symmetry) beside coordinated and lattice water

molecules. Each silver ion presents different coordination geometry: Ag1 and Ag2 are

coordinated by four and three HL carboxylate oxygens, respectively, while Ag3 beside three HL

oxygens has in addition two aqua ligands. On the other hand Ag4 ion, bridged by the

Fig. 2

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methylpyrazine, is further connected to three carboxylate oxygen atoms. Table 3 report a

selection of bond lengths and angles.

The Ag-O bond distances are as expected for this type of compound and the values are in

agreement with those in the few structures reported of Ag(L). [36-37] The silver atom Ag1 has

oxygens O(31c) and O(62) forming an O-Ag-O angle of 146.97(9)° and is further chelated by

carboxylate O(51e) and O(52e) at longer distance. Ag2, digonally coordinated by O(41k) and

O(61d) with an O-Ag-O angle of 153.27(9)°, presents the shorter values (2.162(2) and 2.176(2)

Å, respectively) and in addition is bound to O(32) at 2.400(2) Å. The coordination around Ag3

can be best described as a distorted trigonal bi pyramid, with O(42j) and O(51) forming the axial

bonds at 2.295(2) and 2.412(2) Å (O-Ag-O bond angle of 160.47(7)°) while the other Ag3-O

connections are longer (range from 2.515(3) to 2.669(2) Å). Finally Ag4 has a distorted

tetrahedral environment with Ag(4)-N(1) of 2.415(3) Å, and the Ag-O(carboxylate) in between

2.274(2) and 2.383(2) Å. The HL ligand through its multifunctional coordination sites is

responsible to this variety of coordination mode.

The three-dimensional metal-organic framework can be viewed as formed by thick layers

comprising the crystallographic independent silver ions Ag1, Ag2 and Ag3 clustered by the

organic cyclohexane-1-carboxy-2,3,4,5,6-pentacarboxylate anions. These silver atoms are

arranged close to an inversion center forming a cluster of six metal ions Ag1-Ag2-Ag3…Ag3-

Ag2-Ag1 having intermetallic Ag1-Ag2 and Ag2-Ag3 distances of 2.8465(4) Å and 2.9271(4)

Å, respectively. The two symmetry related Ag3 ions are separated by of 3.3140(4) Å. Fig. 3B

depicts the hexa-nuclear clusters arranged in the direction of axis-a. The crystal packing of Fig. 3

Fig. 3

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evidences silver ions Ag4 bridged by the 2,5-dimethylpyrazine forming (Ag4-(mpyz)-Ag4)n

arrays embedded in the 3D network, being the metal atoms additionally connected by

carboxylate atoms O11/O12. In each fragment the Ag4 ions are bridged at a distance of

7.6192(3) Å, while the Ag4…Ag4' distance between two contiguous fragments is of 3.0106(1)

Å. The embedded Ag4-(mpyz)-Ag4 arrays inside the 3D architecture are shown in Fig. 3A,

while the layer supported by the carboxylate groups is depicted in Fig. 4. The Ag-Ag bridging

value is longer than that of 7.278 Å observed in the [Ag(mpyz)(NO3)] compound; [19] however

this is composed of zig-zag chains with N–Ag–N angles of 126.7(1)°.

The polydentate [HL]5– anion has one carboxylate group protonated, all the other

participate in different way to connect eleven silver ions. Three deprotonated carboxylic groups

present a �2:�1:�1 coordination mode, one �3:�2:�1 and the latter �3:�2:�2 (Figure 5). The

carboxyl group of the [HL]5– ligand forms a strong intraligand hydrogen bond with the adjacent

deprotonated carboxylate group, further stabilizing its cis- conformation (O21…O12 = 2.526(3)

Å, Fig. 5). We have to mention that in order to guarantee the electroneutrality of the compound,

one proton, which could not be detected in the Fourier map, is likely disordered on the

carboxylate groups or present as hydronium ion. It is interesting to observe that all the

intermetallic distances here reported are close or slightly longer of the distance measured in the

silver metal of 2.89 Å, indicating argentophilic interactions.

Fig. 4

Fig. 5

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In the crystal packing no stacking interaction between the pyrazine rings was detected,

and these heterocycles act merely as bridging connectors. On the other hand the coordinated

aqua species (O(1w) and O(2w)) and the lattice water molecule O(3w) are engaged in H-bond

interactions with HL carboxylate groups thus reinforcing the overall architecture. However the

O…O distances are in between 2.81-3.05 Å, indicating not appreciable strong interactions. The

hydrogen bond parameters are reported as supporting information (Table 1S).

3.4 TG study

Thermogravimetric analyses of 1 and 2 were carried in the temperature range of 30-600 °C under

flowing N2 atmosphere at a heating rate of 10 °C min-1. The TGA curves are given in Fig. 6. The

TG profile of complex 1 reveals a thermal stability up to 109 °C. Exclusion of both the ligands

occurs in the temperature range 109-300 °C with mass loss of 71 % (calc. 70.56 %) to form

silver as rest mass of 29 % (calc 29.44).

Complex 2 reveals to be stable up to 116 °C. Partial dehydration of complex occurs in the

temperature range of 116-170 °C with mass loss of ca. 3.02% (calculated 3.05%), corresponding

to the loss of three lattice aqua ligands. Then the complex gets collapsed. On further heating,

derivative 2 decomposed completely in the temperature range of 170-402°Cto form silver(I)

oxide as rest mass (exp.ca.52.09%, calc.52.3%). In this temperature range the coordinated aqua,

2-methylpyrazine (mpyz) and hexa-carboxylate ligands get decomposed via indistinguishable

mass loss path, strongly indicating the presence of H-bonding among them in the crystal.

Fig. 6

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3.5 Luminescence Study

The photoluminescence study of compounds 1, 2 and of the free ligands 5,6,7,8-

tetrahydroquinoxaline (quin), 2-methyl pyrazine (mpyz) and cyclohexane-1,2,3,4,5,6-

hexacarboxylic acid (H6L) was investigated at room temperature (Fig. 7). Luminescence study

for

ligands quin and mpyz were performed in solution [0.1 M in methanol] since they exist in liquid

phase at room temperature. Complex 1 shows an emission maxima at 376 nm when excited at

263 nm. The corresponding free quin ligand displays emission band at 353 nm (�ex = 270 nm).

HL and mpyz show emission maxima at 438 and 357 nm, respectively, when excited with

wavelength of 270 nm. On the other hand, complex 2 shows a broad emission band with

maximum at 451 nm (�ex = 290 nm). It is evident from these data that both emission spectra of 1

and 2 are red shifted with respect to the free ligand emission bands. Complex 1 is shifted by 23

nm, while for complex 2 the change is of 13 and 94 nm with respect to HL and mpyz. Such

emission behaviour of 1 may be assigned to intra-ligand �*-� charge transfer transition and for 2

it is due to the cumulative effect of the intra-ligand �*-� CT transition and Ag···Ag interaction.

[38-41].

3.6 Device Fabrication and the measurement of Electrical conductivity

The thin film devices were fabricated on a clean glass substrate by simple drop-casting

method from aqueous solution of the synthesized materials 1 and 2. To prevent crystallization

Fig. 7

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the substrates were placed on a hot plate at 40 ºC for 20 minutes and the solvent was allowed to

evaporate. The average film thickness for 1 and 2 were ~100 and 60 nm, respectively. Pair of

parallel electrodes of channel length and width of 4 x18 mm was drawn by using conducting

silver paint (Ted Pella Inc.). Fig. 8a shows a schematic illustration of the fabricated device and

the electrical transport measurement setup. The room temperature DC charge transport

measurements of the films were carried out in a probe station (Evergreen Int’l, Taiwan)

connected to a Keithley 2611A Source Meter in ambient conditions using standard two probe

method. Data were collected by means of Lab Tracer interfaced with the data acquisition card.

Fig. 8b shows the current-voltage (I-V) characteristics of our devices. The I-V curve

measured for the deposited film of 1 is perfectly symmetrical but nonlinear (Fig 8b), due to

contact problems. After mild thermal annealing at 50 ºC for 10 min this feature was overcome

and the I vs. V curve becomes linear within the bias voltage in the range from –10 to 10 V. The

conduction is Ohmic and the slope of the I-V curves is same before and after thermal annealing,

indicating that the current is limited by the bulk of the polymer rather than by contact bias. The I-

V characteristic of deposited film realized with 2 is perfectly linear (Fig. 8c), and no further

improvement was observed on mild thermal annealing. Measurement of electrical conductivity

of coordination polymers are one of the most important parameters. A few reports on

conductivity are available on coordination polymer in solid state device form. The conductivity,

calculated from the linear portion of the I-V curve, is in the order of 3x10-4 Scm-1 for 1 and of

1.6x10-4 Scm-1 for 2 at room temperature. These values are quite better than those measured in

other metal based co-ordination polymers [42] and in comparison with other silver based co-

Fig. 8

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ordination polymers so far reported [43]. The better conductivity may be due to the presence in

1of NO3– anions connecting the –[Ag(quin)]n– chains. In fact as suggested by Santillan et. al.,

delocalization in bridging nitrates affects the electronic properties of these anions and may

originate in this case a better conductivity. [44] We measured both devices after one month. No

degradation was observed, indicating air stability of the synthesized materials. It is worth of note

that conductivity measurements depend on the compound specimen, namely single crystals,

pressed pellets, thin films or even nanowires, taking into account also thermal variations.

However present results and those of literature [28] indicate that metal-to-metal direct

interactions in coordination polymers are important but not essential for conduction. In this

respect it is obvious that short metal-metal distances may improve conductivity when metals are

close enough to form an intermetallic bond. On the other hand, increasing of metal–metal

distance decreases the conductivity but it does not vanish completely. [28]

4. Conclusion

The paper describes two new coordination polymers of Ag(I) using heterocyclic N-donor

ligands. Compound 1 displays a layered structure of 4,4 topology where –[Ag(quin)]n– polymers

are connected by nitrate anions. On the other hand the polydentatecyclohexane-1,2,3,4,5,6-

hexacarboxylatein complex 2 led to an unpredicted 3D network containing four independent

Ag(I) ions, each of different coordination environment. In 2 Ag···Ag interactions beside intra-

ligand �*-� charge transfer transition are responsible for the emission behavior. Study of

electrical conductivity of thin film deposited on glass surface shows that the conduction is ohmic

and 1shows a better electrical conductivity than 2 at ambient temperature. Thus the behavior of

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the present compounds indicates that the specific use of metal ions and ligands in the design of

coordination polymers are of high relevance in terms of conductivity.

Acknowledgement

This work is financially supported by CSIR, New Delhi, India through grant 01(2536)/11/EMR-

II. SKJ is thankful to UGC for providing research fellowship. TP thanks DST, Govt. of India for

providing electrical measurement setup via grant SR/FTP/PS-113/2010.

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�

17��

[23] M. Bera, S.K. Jana, D. Hazari, A. Rana, D.S. Chowdhuri, H. Puschmann, E. Zangrando, S.

Dalai, J. Inorg. Organomet. Polym. 23 (2013) 325.

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Legend to the figures

Fig. 1. (a) The 2D structure developed in the crystallographic ab plane and (b) a perspective side

view (white spheres = Ag1, black sphere = Ag2) in 1.

Fig. 2. The Ag-NO3 array showing the distinctively different coordination environment around

Ag1 and Ag2 in 1.

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19��

Fig. 3. (a) Crystal packing of 2 viewed down axis-a evidencing the independent crystallographic

silver ions; the Ag4(mpyz)Ag4 units are highlighted in red colour. (b) The hexa-nuclear cluster

of Ag ions along axis a.

Fig. 4. The Ag4-(mpyz)-Ag4 species (indicated in red) connected by the HL anions in compound

2.

Fig. 5. The hapticity of the [HL]5–anion and the intramolecular H-bond in 2 (for symmetry codes

see Table 3).

Fig. 6. TG profile of complex 1 (a) and 2 (b)

Fig. 7. Emission profile of 1 (�ex = 270 nm)(a) and (b) 2 (�ex = 290 nm).

Fig.8 (a) Schematic of the device with electron transport measurement set up, (b) Current-

voltage I/V characteristics of the film realized with compound 1 and (c) with compound 2.

Table 1. Crystal data and details of refinements for 1 and2.

1 2

Empirical formula C16H20Ag2N6O6 C29H34Ag8N2O31

fw 608.11 1769.54

Crystal system Triclinic Triclinic

Space group P1 P1 a, Å 7.15368(18) 7.9407(2)

b, Å 8.9039(2) 10.2061(2)

c, Å 15.2158(4) 13.7769(3)

�, deg 95.330(2) 96.4983(19)

, deg 94.693(2) 96.444(2)

, deg 92.915(2) 110.913(2)

V, Å3 960.09(5) 1022.17(5)

Z 2 1

Dcalcd,g cm–3 2.104 2.875

�, mm–1 2.089 3.862

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F(000) 600 846

� range, deg 2.55 - 28.96 2.78 - 29.23

no. of reflnscollcd 21238 36280

no. of indepreflns 4710 5152

Rint 0.0330 0.0448

no. of reflns (I > 2�(I)) 4387 4471

no. of refined params 279 343

goodness-of-fit (F2) 1.0481 1.051

R1 (I > 2�(I)) 0.0210 0.0247

R1, wR2 (all data) 0.0240, 0.0436 0.0338, 0.0513

residuals, e/Å3 0.559, –0.451 1.247, –1.012

Table 2. Selected bond lengths (Å) and angles (°) of compound 1

Ag(1)-N(1a) 2.2092(16) Ag(2)-N(1b) 2.2294(16)

Ag(1)-N(4a') 2.2134(16) Ag(2)-N(4b') 2.2471(16)

Ag(1)-O(12) 2.5787(14) Ag(2)-O(11) 2.5707(16)

Ag(1)-O(21) 2.7044(15) Ag(2)-O(21'') 2.6087(15)

Ag(1)-O(23) 2.619215) Ag(2)-O(22'') 2.8780(15)

N(1a)-Ag(1)-N(4a') 165.76(6) N(1b)-Ag(2)-N(4b') 156.03(6)

N(1a)-Ag(1)-O(12) 90.71(5) N(1b)-Ag(2)-O(11) 114.10(5)

N(1a)-Ag(1)-O(23) 104.91(5) N(1b)-Ag(2)-O(21'') 96.74(5)

N(1a)-Ag(1)-O(21) 90.97(5) N(1b)-Ag(2)-O(22'') 92.12(5)

N(4a')-Ag(1)-O(12) 90.96(5) N(4b')-Ag(2)-O(11) 85.10(5)

N(4a')-Ag(1)-O(23) 89.32(5) N(4b')-Ag(2)-O(21'') 98.88(5)

N(4a')-Ag(1)-O(21) 98.41(5) N(4b')-Ag(2)-O(22'') 85.74(5)

O(12)-Ag(1)-O(23) 85.30(5) O(11)-Ag(2)-O(21'') 86.07(5)

O(12)-Ag(1)-O(21) 131.88(5) O(11)-Ag(2)-O(22'') 128.93(5)

O(23)-Ag(1)-O(21) 48.06(4) O(21'')-Ag(2)-O(22'') 46.24(4)

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Symmetrycodes (') -1+x, y, z; ('') x, 1+y, z.

Table 3. Selected bond lengths (Å) and angles (°) of compound 2

Ag(1)-O(31c) 2.206(2) Ag(2)-O(32) 2.400(2)

Ag(1)-O(51e) 2.472(2) Ag(2)-O(41k) 2.162(2)

Ag(1)-O(52e) 2.528(2) Ag(2)-O(61d) 2.176(2)

Ag(1)-O(62) 2.266(2)

Ag(3)-O(42j) 2.295(2)

Ag(4)-N(1) 2.415(3) Ag(3)-O(42) 2.669(2)

Ag(4)-O(11b) 2.299(2) Ag(3)-O(51) 2.412(2)

Ag(4)-O(12i) 2.274(2) Ag(3)-O(1wa) 2.616(3)

Ag(4)-O(52) 2.383(2) Ag(3)-O(2w) 2.515(3)

O(31c)-Ag(1)-O(51e) 122.90(8) O(32)-Ag(2)-O(41k) 90.87(8)

O(31c)-Ag(1)-O(52e) 97.38(8) O(32)-Ag(2)-O(61d) 109.04(8)

O(51e)-Ag(1)-O(52e) 52.73(7) O(61d)-Ag(2)-O(41k) 153.27(9)

O(62)-Ag(1)-O(31c) 146.97(9)

O(62)-Ag(1)-O(51e) 90.04(8) O(42)-Ag(3)-O(42j) 96.59(7)

O(62)-Ag(1)-O(52e) 101.66(7) O(42)-Ag(3)-O(51) 71.21(7)

O(42)-Ag(3)-O(1wa) 122.64(7)

N(1)-Ag(4)-O(11b) 87.84(9) O(51)-Ag(3)-O(1wa) 84.12(8)

N(1)-Ag(4)-O(12i) 109.62(9) O(51)-Ag(3)-O(42j) 160.47(7)

N(1)-Ag(4)- O(52) 99.01(8) O(1wa)-Ag(3)-O(42j) 115.41(8)

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O(11b)-Ag(4)-O(12i) 136.42(8) O(2w)-Ag(3)-O(42) 130.10(8)

O(52)-Ag(4)-O(11b) 106.06(8) O(2w)-Ag(3)-O(51) 84.86(9)

O(52)-Ag(4)-O(12i) 109.87(8) O(2w)-Ag(3)-O(42j) 92.23(9)

O(2w)-Ag(3)-O(1wa) 96.43(9)

Symmetrycodes : (a) -1+x, -1+y, z; (b) -1+x, y, z; (c) x, -1+y, z; (d) x, 1+y, z; (e) 1+x, y, z; (i) -x, -y, -1-z; (j) -x, -y, -z; (k) -x, 1-y, -z.

Fig. 1

(a)

(b)

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Fig. 2

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Fig. 3

Fig. 3

(a)

(b)

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Fig. 4

Fig. 5

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Fig. 6

50 100 150 200 250 300 350 400 450

50

60

70

80

90

100

Wei

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%)

Temperature (0C)

100 200 300 400 500 60020

40

60

80

100

Wei

ght(%

)

Temperature(oC)

(a)

(b)

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Fig. 7

(a)

325 350 375 400 425 4500

1

2

3

4

5

6

Inte

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(a.u

)

Wavelength (nm)

2 quin

350 400 450 500 5500

1

2

3

4

5

mpyzHL1

Inte

nsity

(a.u

)

Wave length (nm)

1

(b)2

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-10 -5 0 5 10-8.0x10-8

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8.0x10-8

I(A)

V(V)

Experimental data linear fit

V I

glass

Ag Ag

(a)

-10 -5 0 5 10-1.0x10-7

-5.0x10-8

0.0

5.0x10-8

1.0x10-7

Before annealedAfter annealedAfter one month

I(A)

V(V)

(b) (c)

Fig. 8

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Highlights

� 1 is 2D layered while 2 present a 3D polymeric architecture.

� The network in 2 is stabilized by argentophilic interactions and hydrogen bonding.

� Electrical conductivity measurement is quite interesting.

� Argentophilic interaction and intra-ligand �*-� CT explains emission behavior of 2.

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Two new

by x-ray

w 1D and 3D

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1

D coordinati

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nce and therm

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