Inorganic Chemistry Communications 23 (2012) 103–108

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Inorganic Chemistry Communications

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A novel Co3+-based asymmetrical building block: Heterobimetallic metallacyclesversus coordination networks

Girijesh Kumar, Rajeev Gupta ⁎Department of Chemistry, University of Delhi, Delhi-110007, India

⁎ Corresponding author. Fax: +91 11 27666605.E-mail address: rgupta@chemistry.du.ac.in (R. Gupta

1387-7003/$ – see front matter © 2012 Elsevier B.V. Alldoi:10.1016/j.inoche.2012.06.018

a b s t r a c t

a r t i c l e i n f o

Article history:Received 8 May 2012Accepted 18 June 2012Available online 23 June 2012

Keywords:Asymmetrical building blockCoordination networksHeterobimetallic complexesCrystal structures

A new Co3+-based asymmetrical building block (1) offering both 2-pyridyl and 3-pyridyl appended groupshas been synthesized and utilized for preparing heterobimetallic systems. The reactions of 1 with secondarymetals afforded {Co3+–Zn2+} metallacycle (2), {Co3+–Cd2+} metallacycle‐based coordination polymer (3)and a {Co3+–Hg2+} coordination chain (4). The crystallographic studies reveal the importance of asymmet-rical building block in generating unique structural motifs.

© 2012 Elsevier B.V. All rights reserved.

During the past decade, significant attention has been paid to thedesign and syntheses of coordination networks not only for theirpotential applications in catalysis [1], magnetism [2], gas sorption[3], separation [3], and luminescence [4], but also for their fascinatingstructural topologies [5]. Generally, the structural type and topologyof a coordination network depend on the metal ion, its oxidationstate and coordination geometry as well as on the type and function-ality of ligand [6]. Several homometallic coordination networks withvarious nuclearities, dimensionalities and topologies have been suc-cessfully synthesized and characterized [7]. However, the chemistryof heterometallic coordination networks has received considerablyless attention [8]. This is primarily due to the difficulty in placingtwo different metals in close proximity. To prepare homometallic co-ordination networks with novel structural features, pyridine-amidebased ligands have been successfully used [9]. Interestingly, in allsuch literature precedents; the pyridine-amide based ligands aresymmetrical in nature thus limiting structural diversity.

Our group is interested about designing coordination complexesthose act as the molecular building blocks. Several such buildingblocks have been used for the preparation of heterobimetallic com-plexes and networks of highly ordered nature [10–16]. Notably, ourearlier studies have employed symmetrical building blocks to under-stand the secondary metal mediated self‐assembly (Scheme 1). In allsuch cases, a building block offers only one type of appended pyridinegroup; namely either 2-pyridyl ([Co(L22)2]−), 3-pyridyl ([Co(L33)2]−),or 4-pyridyl ([Co(L44)2]−) rings. Importantly, whereas the buildingblock [Co(L22)2]− affords {M2+–Co3+–M2+} type heterobimetalliccomplexes; [Co(L33)2]− and [Co(L44)2]− produced two- (2D) and/or

).

rights reserved.

three-dimensional (3D) networks. Herein we report a new Co3+

based asymmetrical building block, [Co(L23)2]− where the appendedpyridine groups are different viz. 2-pyridyl and 3-pyridyl. Understand-ably, both 2-pyridyl and 3-pyridyl groups will be positioned to differ-ent directions to potentially coordinate the secondary metals. To thebest of our knowledge, there has not been any report about the synthe-sis of an asymmetrical building block of pyridine-amide based ligandand investigation of its coordination modes. We therefore explore thecoordinating abilities of such an asymmetrical building block towardsfew secondary metal ions and report our preliminary structural andself-assembly observations.

Complex Et4N[Co3+(L23)2] (1) was synthesized starting with anasymmetrical ligand H2L23 containing 2-pyridyl and 3-pyridyl groups(Fig. S1, Supporting information) [17,18]. The 1H and 13C NMR spectraof complex 1 clearly display the asymmetrical nature of two pyridylrings (Fig. S2, Supporting information). The heterobimetallic networks2, 3 and 4were synthesized by treating the building block 1with an ap-propriate MCl2 salt in DMF (Scheme 2) [19–21]. All three networkswere isolated as deep-red crystallinematerial in good yield. The IR spec-tra of networks 2, 3 and 4 show a strong band at ca. 1595cm−1 due tothe νamide stretch. In addition, broad features at ca. 3400cm−1 suggestthe presence of lattice water molecules in all three networks that arewell supported by the microanalysis results as well as thermal studies(vide infra). All three heterobimetallic networks were also character-ized by 1H and 13C NMR spectra owing to their diamagnetic nature(Figs. S3–S4, Supporting information). The NMR spectra were inter-preted in comparison with the building block 1. The coordination ofZn2+or Cd2+ ions in network2 or 3did not significantly alter the chem-ical environment of proton or carbon atoms of the pyridyl rings as thesignals were at similar position as noted for complex 1. Interestingly,however, broad proton signals were obtained for network 4 which is

Scheme 1. Symmetrical building blocks used in our earlier work.

104 G. Kumar, R. Gupta / Inorganic Chemistry Communications 23 (2012) 103–108

most likely due to the large ionic radius of Hg2+ ion that may have pro-moted solvent exchange. The absorption spectra of all three networksshow λmax within 640–645nm that has been assigned to the d–d transi-tion originating from the Co3+ ion (Fig. S5, Supporting information).

To examine the thermal stability and decomposition profile, ther-mogravimetric analysis (TGA) was performed on all three networks(Fig. S6, Supporting information). Network 2 exhibits an initialweight loss of 12.90% in the temperature range of 25–205°C due tothe loss of one Et4N+ ion, one DMF, and three water molecules(calc. 12.26%). For network 3, a weight loss of 10.72% (calc. 10.42%)between 25 and 135°C corresponds to the loss of one water and aDMF molecule. In a similar manner, network 4 also showed the initialweight loss (obs. 15.40%; calc. 15.15%) due to one Et4N+ ion and twowater molecules between 25 and 220°C. The differential scanning ca-lorimetric (DSC) analysis for all three networks corroborates the TGresults and shows combined features for the loss of solvent mole-cule(s) and/or Et4N+ ions (Fig. S7, Supporting information). Further-more, microanalysis results additionally support the presence oflattice solvent molecules and strengthen TGA and DSC studies.

All three {Co3+–M2+} heterobimetallic networks were crystallo-graphically characterized to understand the importance of asymmet-rical nature of building block 1 in secondary metal-assisted self‐assembly [22]. Complex 1 offers two 2-pyridyl and two 3-pyridylappended groups that are available to further coordinate the second-ary metal ions. Thus in all three networks, building block 1 serves as aconnector that further coordinates to the secondary metal ions. In abuilding block, two asymmetrical ligands in their deprotonatedform, [L23]2− coordinate the Co3+ ion meridionally to afford an octa-hedral geometry. The Co3+ ion is coordinated by four deprotonatedNamide groups in the basal plane whereas two Npyridyl atoms occupythe axial positions. In all three cases, the Co\Namide bond distancesare longer than the Co\Npyridine bond distances as observed before[10–12,14,15].

The crystal structure of 2 [22] reveals that it is composed of ametallacycle, where two building blocks are connected through two

Scheme 2. Asymmetrical building block 1 and heterobimetallic complexes 2–4.

Zn(II) ions (Fig. 1). Notably, only 3-pyridyl groups coordinate to theZn(II) ion while the 2-pyridyl groups remain uncoordinated (Fig. 1a).Every Zn(II) ion has tetrahedral geometry where two positions are oc-cupied by the 3-pyridyl nitrogen atoms (N5 and N6) from two differentbuilding blocks whereas the remaining two sites are coordinated tochloride atoms (Fig. 1b). The Zn\Npyridine bond lengths are in therange of 2.041–2.065Å while the Npyridine\Zn\Npyridine and Cl\Zn\Clbond angles were found to be 102.77(15)° to 119.46(8)°, respectively.These bond lengths and angles are comparable to other {Co3+–Zn2+}complexes of similar structural nature [10,14]. The Zn(II) ion is slightlydistorted froman ideal tetrahedral geometry as the τ4 distortionparam-eter has the value of 0.92 [23]. Itmay be noted that for a perfect tetrahe-dral geometry, the ideal value of τ4 is 1 whereas for a perfectsquare-planar geometry the value is zero [23].

For this network, an interesting solid-state packing was observed be-tween the metallacycles (Fig. 1c and d). The {Co3+–Zn2+} metallacyclesare further connected to each other to create a two‐dimensional(2D) network through weak intermolecular C\H⋯Ohydrogen-bonding (H-bonding) interactions between Oamide atomsand the hydrogen atoms attached to Et4N cation (O1⋯H36B\C36,O1⋯H39B\C39, O3⋯H37B\C37); as well as between ODMF atomand pyridine‐H atom (O5⋯H1\C1). The heteroatom separation be-tween O1⋯C36, O1⋯C39, O3⋯C37, and O5⋯C1 was found to be3.583Å, 3.199Å, 3.527Å, and 3.387Å, respectively (Fig. S8,Supporting information). In addition, Cl atoms attached tothe Zn(II) ion weakly interact with the hydrogen atoms attached tothe Et4N cation. A combination of all such weak interactions createsa 2D network with void space being occupied by the Et4N+ cationand solvent molecules.

Network 3 [22] is also composed of a metallacycle due to the partic-ipation of building block 1 with that of Cd2+ ion (Fig. 2). The structureshows a unique arrangement of building block such that both2-pyridyl and 3-pyridyl groups are coordinated to the Cd(II) ions(Fig. 2a). However, in this case, the metallacycles further extend viaCd(II) ions to generate a zig-zag chain (Fig. 2b). These metallacyclescontaining zig-zag chains result in the generation of an interestingsolid-state structure (Fig. 2c and d). In a metallacycle, every Cd(II) ionis in octahedral geometry, coordinated by four Npyridyl atoms (N1, N5,N6, and N10) from two different building blocks; one Oamide atom(O3); and one chloride atom. The Cd\Oamide and Cd\Cl bond lengthsare 2.415(6)Å and 2.481(3)Å, respectively; while the Cd\Npyridine

bond lengths were in the range of 2.316(8)–2.492(10)Å. These bondlengths and angles are comparable to those reported for other Cd2+‐

based heterobimetallic complexes [11,15]. Further, a three‐dimensional(3D) network is created through H-bonding interactions betweenOamide atoms and Cl atom attached to Cd(II) ion to those of pyridine‐H atoms (Fig. S9, Supporting information). The heteroatom separationsbetween interacting pairs are as follows: O2⋯H45\C45 (3.167Å),

N5

N10

N6

Cl1

Cl2

N1

Zn1

a b

Zn1#

Co1

N3O2O1

O4O3N8

N2

N10

N4

N9

N1

Zn1 N5#

Cl1

Cl2

N5

N6#

N6

N7 Cl2#

Cl1#

dc

Fig. 1. (a) Partial molecular structure of network 2 showing coordination environment around the Zn2+ ion and its bonding with the building block 1; thermal ellipsoids are drawnat 30% probability level whereas the hydrogen atoms, cation and solvent molecules have been omitted for clarity; selected bond lengths [Å] and angles [deg]: Zn1\N5 2.041(4),Zn1\N6 2.065(4), Zn1\Cl1 2.2108(17), Zn1\Cl2 2.229(2), N5\Zn1\N6 102.77(15), N5\Zn1\Cl1 108.91(13), N6\Zn1\Cl1 106.27(11), N5\Zn1\Cl2 107.32(14),N6\Zn1\Cl2 110.86(12), Cl1\Zn1\Cl2 119.46(8). (b) {Co3+–Zn2+} based metallacycle. (c) A view of packing along the a-axis. (d) A view along the c-axis.

105G. Kumar, R. Gupta / Inorganic Chemistry Communications 23 (2012) 103–108

O4⋯H16\C16 (3.515Å), O8⋯H59\C59 (3.230Å), and Cl1⋯H63\C63(3.509Å). Notably, PLATON calculation [24] shows that the network3 offers large void volume of ca. 54% per unit cell. This large voidis due to the presence of cavities of dimensions 18.28×13.65Å2

(Fig. 2d) which were partially occupied by the disordered solventmolecules [22].

The crystal structure of network 4 [22] is composed of a one‐dimensional (1D) infinite chain where building blocks are connectedthrough Hg(II) ions (Fig. 3). Every Hg(II) ion has tetrahedral geometrywhere two coordination sites are occupied by the Npyridyl groups (N1and N6) from two different building blocks whereas the remaining po-sitions are filled with chloride atoms (Fig. 3a). The τ4 distortion param-eter for Hg(II) ion is 0.78 [23], thereby suggesting a more distortedgeometry froman ideal tetrahedralwhen compared to Zn(II) ion in net-work 2. The average Hg\Npyridine and Hg\Cl distances were 2.388and 2.365Å, respectively. In this case also, only the 3-pyridy groupsare coordinated to the Hg(II) ions to generate a 1D chain while the2-pyridyl groups remain free (Fig. 3b). The 1D zig-zag chains further in-teract with each other via H-bonding between Oamide atoms and pyri-dine‐H atoms; between Oamide atoms and the hydrogen atomsattached to Et4N cation (Fig. 3c); and between Cl atom to that of pyri-dine‐H atoms and hydrogen atoms attached to Et4N cation (Fig. S10,Supporting information).

A closer look to the building block in all three networks suggeststhat the 2-pyridyl nitrogen atoms are faced inward while the3-pyridyl nitrogen atoms are projected outward. Thus, 3-pyridyl ni-trogen atoms are freely available for coordination and/or extension.As Zn2+ and Hg2+ ions prefer tetrahedral geometry, these metalsare easily coordinated by two 3-pyridyl rings from two differentbuilding blocks whereas the remaining two positions are occupiedby the Cl atoms. Interestingly, Cd2+ ion prefers octahedral geometrythat forces both 3-pyridyl and 2-pyridyl groups to simultaneously co-ordinate the metal. Such an arrangement results in the constitution ofa N4 basal plane around the Cd(II) ion where two positions each areoccupied by the 3-pyridyl and 2-pyridyl groups. The remaining axialpositions are occupied by one Cl atom and an Oamide group. Thus, itcould be concluded that the geometrical preference of secondarymetal ion is one of the decisive factors in controlling the networktopology.

In summary, we have synthesized three new heterobimetallic mo-tifs compose of {Co3+–Zn2+} metallacycle, {Co3+–Cd2+} metallacycle‐based coordination polymer and a {Co3+–Hg2+} coordination chain.These extended structures have been constructed utilizing an asym-metrical building block offering both 2- and 3-pyridyl appended groups.Our results demonstrate the potential role of asymmetrical buildingblock in conjunction with secondary metal's geometrical preference in

O3N1

N5N10

Cd1

Cl1

N6

N10

Cd1

O4 N8

N9

N2Co1

N3

O3

N1 N5#

N10#

Cl1

O1

N6

N7

Cd1#

Cd1N5

O2

N10Cd1#

N4

dc

a b

Fig. 2. (a) Partial molecular structure of network 3 showing coordination environment around the Cd2+ ion and its bonding with the building block 1; thermal ellipsoids are drawnat 30% probability level whereas the hydrogen atoms and water molecules have been omitted for clarity; selected bond lengths [Å] and angles [deg]: Cd1\N1 2.492(10), Cd1\N52.453(8), Cd1\N6 2.316(8), Cd1\N10 2.351(8), Cd1\O3 2.415(6), Cd1\Cl1 2.481(3), N1\Cd1\N6 101.2(3), N1\Cd1\N10 92.5(3), N5\Cd1\N6 82.6(3), N5\Cd1\N1080.5(3), N6\Cd1\N10 157.3(3), N5\Cd1\O3 81.6(2), N6\Cd1\O3 76.1(3) N10\Cd1\O3 86.4(2), N6\Cd1\Cl1 99.5(2), N10\Cd1\Cl1 97.3(2), N5\Cd1\Cl 195.7(2),O3\Cd1\N1 88.1(2), N5\Cd1\N1 167.8(3), Cl1\Cd1\N1 95.1(2), O3\Cd1\Cl1 175.03(19). (b) {Co3+–Cd2+} based metallacycle. (c) A view along a-axis showing the contactbetween two metallacycles. (d) A view along the c-axis showing network generation.

106 G. Kumar, R. Gupta / Inorganic Chemistry Communications 23 (2012) 103–108

controlling the network topology of the resultant material. Future workis directed to synthesize additional asymmetrical building blocks andexplore their coordination chemistrywith long term goal to understandand/or control the network topology.

Acknowledgments

RG gratefully acknowledges the generous financial support from theDepartment of Science and Technology (DST), New Delhi. Crystallo-graphic data and instrumental facilities were provided by the CIF-USICof this university. GK thanks CSIR for the award of SRF fellowship.

Appendix A. Supplementary data

CCDC-879837 (2), 879836 (3) and 879838 (4) contain the supple-mentary crystallographic data for this paper. These data can be obtainedfree of charge at http://www.ccdc.cam.ac.uk/conts/retrieving.html orfrom the Cambridge Crystallographic Data Centre, 12 Union Road, Cam-bridge CB 21EZ, UK; fax: (+44) 1223-336-033; e-mail: deposit@

ccdc.cam.ac.uk. Supplementary data associated with this article can befound online at http://dx.doi.org/10.1016/j.inoche.2012.06.018.

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[17] See the Supplementary Material for full experimental details.[18] (Et4N)[Co(L23)2] (1). Ligand H2L23 (1.0g, 3.10 mmol), Co(OAc)2.4H2O (0.39g,

1.56mmol) and K2CO3 (10.78 g, 77.9 mmol) were taken in CH2Cl2 (50ml) andthe mixture was refluxed for 4h. To the resulting deep red coloured solution,solid Et4NCl.×H2O (1.02g, 6.2mmol) was added and stirred in open air for 2hat room temperature. Exposure to air resulted in a deep green solution. Removalof the solvent was followed by the addition of CH3CN and filtration. On concen-tration and addition of diethyl ether a dark green precipitate resulted that wasfiltered and dried. Recrystallization from CH3CN-Et2O (vapour diffusion) affordeda highly crystalline product also suitable for the diffraction studies. Yield 1.56g(60%). Anal. Calcd. for C42H42N11O4Co.2H2O: C, 58.67%; H, 5.39%; N, 17.92%.Found: C, 58.25%; H, 5.58%; N, 17.93%. FTIR (KBr, selected peaks): 1610, 1463,1423cm−1. Conductivity (CH3CN, ~1mM, 298K): ΛM=120Ω−1cm2mol−1.Absorption spectrum (λmax, nm, CH3CN (ε, M−1cm−1): 640 (120), 470 (sh,1700), 425 (sh, 2575), 391 (sh, 5380). ES-MS (CH3OH, m/z): Obs. 730.96; Calc.731.96 for [{Co(L23)2}+K++H+]. 1H NMR (DMSO-d6, 300MHz): δ=7.98–8.05(m, 4H, H9/H9′+H11/H11′), 7.86 (s, 2H, H15/H15′), 7.55–7.71 (m, 6H,H2/H2′+H17/H17′+H19/H19′), 7.32–7.34 (m, 2H, H10/H10′), 6.92−7.02 (m, 6H,H4/H4′+H5/H5′+H18/H18′), 6.73–6.77 (m, 2H; H3/H3′), 3.2 (q, 8H, \CH2\,Et4N+), 1.17 (t, 12H, \CH3, Et4N+). 13C NMR (DMSO-d6, 400MHz): δ=167.55(C7), 166.92 (C13), 159.17(C6), 156.41 (C8), 156.07 (C12), 147.63 (C14+17),144.26 (C10), 139.50 (C2+15), 135.86 (C5), 133.20 (C19), 123.12 (C9+11), 121.93(C4), 118.37 (C3), 7.09 (\CH3, Et4N+), 51.40 (\CH2\, Et4N+)

[19] (Et4N)2[(1)2Zn2Cl4] (2). To a solution of anhydrous ZnCl2 (0.033 g, 0.243mmol) indry DMF (2ml) was added a solution of complex 1 (0.100g, 0.121 mmol) dissolvedinDMF (4mL). The resultant deep-red solutionwas stirred for 1h. Vapor diffusion ofisopropyl ether to the filtrate afforded deep-red crystalline product also suitable forthe diffraction studies. Yield: 0.072g (57%). Anal. Calcd. for C84H84N22O8Cl4Co2Zn2.-DMF.3H2O: C, 51.04%; H, 4.78%; N, 15.74%. Found: C, 51.51%; H, 4.62%; N, 15.66%.FTIR (KBr, selected peaks): 3410, 1640, 1600, 1560cm−1. Conductivity (DMSO,~1mM, 298K): ΛM=45Ω−1cm2mol−1. Absorption spectrum [λmax, nm, DMSO(ε, M−1cm−1)]: 642 (240), 562 (sh, 290), 541 (sh, 160). 1H NMR (DMSO-d6,400MHz): δ=7.99–8.04 (m, 2H, H10/H10′), 7.95 (s, \CHO, DMF), 7.86 (s, 2H,H15/H15′), 7.67–7.70 (m, 4H, H9/H9′+H11/H11′), 7.56–7.57 (d, 2H, H2/H2′ J=4.0Htz), 7.33–7.37 (m, 4H, H17/H17′+H19/H19′), 6.99–7.03 (m, 4H, H4/H4′+H18/H18′),6.95–6.98 (m, 2H, H3/H3′), 6.75–6.77 (m, 2H, H5/H5′), 2.88 (s, 3H, \CH3, DMF),2.73 (s, 3H,\CH3′, DMF), 3.16 (q, 8H,\CH2\, Et4N+), 1.14 (t, 12H,\CH3, Et4N+).13C NMR (DMSO-d6, 400MHz): δ=167.50 (C7), 166.74 (C13), 162.19 (\CHO, DMF),158.99 C6), 156.27 (C8), 155.96 (C12), 147.54 (C5+14), (144.20 (C17), 142.38 (C10),139.41 (C2), 135.85 (C15), 133.72 (C19), 123.08 (C9+11), 122.78 (C3), 121.88 (C18),118.24 (C4), 35.74 (\CH3, DMF), 30.66 (\CH3′, DMF), 7.09 (\CH3, Et4N+), 51.39(\CH2\, Et4N+)

[20] [(1)2Cd2Cl2]n (3). This network was synthesized in a similar manner as discussedfor 2 using CdCl2.xH2O (0.049g, 0.243mmol) in place of ZnCl2. Yield: 0.036 g(68%). Anal. Calcd. for C68H44N20O8Cl2Cd2Co2.DMF.H2O: C, 48.07%; H, 3.01%; N,16.58%. Found: C, 48.64%; H, 3.13%; N, 16.62%. FTIR (KBr, selected peaks): 3400,1605, 1595cm−1. Conductivity (DMSO ~1mM, 298K): ΛM=20Ω−1cm2mol−1.Absorption spectrum [λmax, nm, DMSO (ε, M−1cm−1)]: 640 (95), 561 (sh, 40),539 (sh, 70). 1H NMR (DMSO-d6, 400MHz): δ=7.98–8.03 (m, 2H, H10/H10′),7.94 (S, \CHO, DMF), 7.86 (s, 2H, H15/H15′), 7.65–7.69 (m, 4H,

H9/H9′+H11/H11′), 7.54–7.55 (d, 2H, H2/H2′ J=4.0 Htz), 7.31–7.34 (m, 4H,H17/H17′+H19/H19′), 6.96–7.00 (m, 4H, H4/H4′+H18/H18′), 6.89–6.92 (m, 2H,H3/H3′), 6.72–6.74 (m, 2H, H5/H5′), 2.87 (s, 3H, \CH3, DMF), 2.71 (s, 3H, \CH3′,

DMF), 3.18 (q, 8H, \CH2\, Et4N+), 1.14 (t, 12H, \CH3, Et4N+). 13C NMR(DMSO-d6, 400MHz): δ=167.58 (C7), 166.87 (C13), 162.26 (\CHO, DMF),159.08 (C6), 156.41 (C8), 156.10 (C12), 147.90 (C5), 147.59 (C14), 144.21 (C17),142.46 (C10), 139.50 (C2), 135.80 (C15), 133.65 (C19), 123.19 (C9+11), 122.78(C3), 121.96 (C18), 118.27 (C4), 35.80 (\CH3, DMF), 30.68 (\CH3′, DMF), 7.09(\CH3, Et4N+), 51.38 (\CH2\, Et4N+)

[21] {(Et4N)[(1)HgCl2]}n (4). This network was also synthesized in a similar manneras noted for 2 using HgCl2 (0.032 g, 0.243 mmol) in place of ZnCl2. Yield:0.045g (66%). Anal. Calcd. for C42H42N11O4Cl2CoHg.2H2O: C, 44.59%; H, 4.10%;N, 13.62%. Found: C, 44.14%; H, 4.21%; N, 13.84%. FTIR (KBr, selected peaks):3420, 1654, 1597 cm−1. Conductivity (DMSO, ~1mM, 298 K): ΛM = 35Ω−1cm2mol−1. Absorption spectrum [λmax, nm, DMSO (ε, M−1cm−1)]: 643(115), 562 (sh, 50), 540 (sh, 105). 1H NMR (DMSO-d6, 400MHz): δ=8.0–8.02(br, 2H, H10/H10′), 7.94 (s, \CHO, DMF), 7.83 (s, 2H, H15/H15′), 7.66–7.69 (m,4H, H9/H9′+H11/H11′), 7.54 (d, 2H, H2/H2′), 7.37 (m, 4H, H17/H17′+H19/H19′),6.96–6.98 (m, H4/H4′+H18/H18′), 6.94 (d, 2H, H3/H3′), 6.72–6.74 (m, 2H,H5/H5′), 2.85 (s, 3H, \CH3, DMF), 2.71 (s, 3H, \CH3′, DMF), 3.18 (q, 8H,\CH2\, Et4N+), 1.14 (t, 12H, \CH3, Et4N+). 13C NMR (DMSO-d6, 400 MHz):δ=167.27 (C7), 166.97 (C13), 162.24 (\CHO, DMF), 158.71 (C6), 155.75 (C8+12),147.97 (C5+10+14+17), 139.75 (C2), 133.49 (C15+19), 123.40 (C3+9+11+18), 122.09(C4), 35.72 (\CH3, DMF), 30.65 (\CH3′, DMF), 7.03 (\CH3, Et4N+), 51.37(\CH2\, Et4N+)

[22] Crystallographic data collection and structure refinement parameters for net-works 2, 3 and 4: Crystal data for 2 (C90H99Cl4Co2N24O12Zn2): monoclinic, spacegroup, P21/n, a=15.184(5) Å, b=16.737(5)Å, c=21.478(5) Å, α=90°,β=94.769(5)°, γ=90°. V=5439(3)Å3, Z=2, R (int)=0.0575, R1=0.0706,wR2=0.1919 [I>2σ(I)], GOF=1.029. Crystal data for 3 (C34H26CdClCoN10O6):hexagonal, space group, P3121, a=21.8582(7)Å, b=21.8582(7)Å,c=23.3331(9)Å, α=90°, β=90°, γ=120°. V=9654(3)Å3, Z=6, R (int)=0.0264,R1=0.0956, wR2=0.2821 [I > 2σ(I)], GOF=1.085. Crystal data for 4 (C42H42Cl2-CoHgN11O4): monoclinic, space group, P1n1, a=9.974(7)Å, b=11.554(5)Å,c=20.031(2)Å, α=90°, β=103.291(9)°, γ=90°. V=2246.5(19)Å3, Z=2, R(int)=0.0225, R1=0.0543, wR2=0.1456 [I>2σ(I)], GOF=1.048. Single-crystalX-ray diffraction data for networks 2, 3 and 4 were collected on a Oxford XCaliburCCD diffractometer equipped with graphite monochromatic Mo-Kα radiation(λ=0.71073Å) [25]. The frames were collected at 180K for 3 and 293K for 2 and4, respectively. Data was processed with XCalibur S SAINT while the empirical ab-sorption correction was applied using spherical harmonics implemented inSCALE3 ABSPACK scaling algorithm [25]. The structures were solved by the directmethods and refined by the full-matrix least-squares refinement techniques on F2

using the program SHELXL-97 incorporated in the WINGX 1.8.05 crystallographiccollective package [26]. The hydrogen atoms were fixed at the calculated positionwith isotropic thermal parameters whereas the non-hydrogen atoms were refinedanisotropically except the uncoordinated water molecules O1W and O2W for net-work 3 and carbon atoms C39, C40, C41, and C42 for network 4. These atoms werealso found to be positionally disordered and were solved using PART command.Their positions were refined isotropically with the site occupancy factors of 0.50 incase of O1W and O2W. Further, the free variables of carbon atoms C39, C40, C41,and C42 for network 4 were refined up to 0.73788. For network 3, a DMF wasfound to be severely disordered and could not be accurately modeled and thuswas squeezed using PLATON [24]. Moreover, for networks 2 and 3, the hydrogenatoms for the lattice watermolecules could not be located; however, their empiricalformulae include these hydrogen atoms

[23] L. Yang, D.R. Powell, R.P. Houser, Structural variation in copper(I) complexes withpyridylmethylamide ligands: structural analysis with a new four-coordinategeometry index, τ4, Dalton Trans. (2007) 955–964.

[24] A.L. Spek, PLATON, A Multipurpose Crystallographic Tool, Utrecht University, TheNetherlands, 2002..

[25] CrysAlisPro, ver. 1.171.33.49b, Oxford Diffraction Ltd., 2009.[26] G.M. Sheldrick, SHELXS97, Program for Crystal Structure Solution, University of

Göttingen, Göttingen, Germany, 1997..