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New CuI2(TCNQ-II) and CuI2(F4TCNQ-II) coordination polymers Brendan F. Abrahams, Robert W. Elliott, Timothy A. Hudson, Richard Robson, and Ashley L. Sutton Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.5b00220 • Publication Date (Web): 24 Mar 2015 Downloaded from http://pubs.acs.org on March 31, 2015

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New CuI2(TCNQ-II) and CuI2(F4TCNQ-II) coordination polymers Brendan F. Abrahams,* Robert W. Elliott, Timothy A. Hudson, Richard Robson* and Ashley L. Sutton School of Chemistry, University of Melbourne, Victoria 3010, Australia. Abstract Coordination polymer strips of composition …Cu+2.lig2-.Cu+2.lig2-.Cu+2.lig2-… (where lig2- = TCNQ2or its 2,3,4,5-tetrafluoro analogue) are observed with a wide range of co-ligands (monodentate, bidentate and tridentate). Interdigitation of “thin”, planar N-heteroaromatic co-ligands on one strip with those on a neighbor is a common structural feature.

Co-ligands too bulky to allow

interdigitation give either non-interdigitating strips or 2D sheet structures. Both strips and sheets have 2-connecting Cu centers and 4-connecting tetracynano ligands. As a consequence of the great flexibility of the Cu/tetracyano ligand association, the geometries of the sheet structures vary widely from almost coplanar to highly corrugated and convoluted, in spite of which the same topology is present in all.

*Corresponding authors: Fax: +61 9347 5180; Phone +61 3 8344 0341 (BFA),+61 3 8344 6469 (RR) Email: [email protected]; [email protected] ACS Paragon Plus Environment

Crystal Growth & Design

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New CuI2(TCNQ-II) and CuI2(F4TCNQ-II) coordination polymers Brendan F. Abrahams,* Robert W. Elliott, Timothy A. Hudson, Richard Robson* and Ashley L. Sutton School of Chemistry, University of Melbourne, Victoria 3010, Australia.

*Corresponding authors: Fax: +61 9347 5180; Phone +61 3 8344 0341 (BFA),+61 3 8344 6469 (RR) Email: [email protected]; [email protected]

Abstract Coordination polymer strips of composition …Cu+2.lig2-.Cu+2.lig2-.Cu+2.lig2-… (where lig2- = TCNQ2- or its 2,3,4,5-tetrafluoro analogue) are observed with a wide range of co-ligands (monodentate, bidentate and tridentate). Interdigitation of “thin”, planar N-heteroaromatic co-ligands on one strip with those on a neighbor is a common structural feature. Co-ligands too bulky to allow interdigitation give either noninterdigitating strips or 2D sheet structures. Both strips and sheets have 2-connecting Cu centers and 4connecting tetracynano ligands. As a consequence of the great flexibility of the Cu/tetracyano ligand association, the geometries of the sheet structures vary widely from almost coplanar to highly corrugated and convoluted, in spite of which the same topology is present in all.

ACS Paragon Plus Environment

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Introduction Tetracyanoquinodimethane, TCNQ, structure I, has attracted strong and continuing interest since its synthesis and properties were first reported half a century ago.1 One reason for this attention arises from the ability of TCNQ to exist with a formal oxidation state (which need not be integral) in the range 0 to –II depending on the components with which it is associated. The following examples provide an indication of unusual electronic/magnetic properties that may be exhibited by solids that contain TCNQ: 1) The first purely organic material to exhibit metallic conductivity was a complex of TCNQ with tetrathiafulvalene.2 2) The electrical resistance of thin films of AgI(TCNQ-I) and CuI(TCNQ-I), when subjected to an increasing electric field, drops dramatically at a certain threshold potential.3 3) A TCNQ/Gd coordination polymer behaves as a magnet at low temperature.4

In our largely fruitless synthetic work of the early 1990’s with metal derivatives of the TCNQ–• radical anion, we had anticipated, on the basis of the successful construction of a number of coordination polymers with intended PtS-like topologies, that this topology would also be a very likely outcome of combining the radical anion (acting as a planar rectangular 4-connecting building block) with Ag+ or Cu+ (acting as tetrahedral 4-connecting building blocks). The structure of AgI(TCNQ-I) was reported by Shields in 19855 and sometime later, close examination of the structure of AgI(TCNQ-I) revealed that it did indeed contain a network with the PtS topology; in fact, two such interpenetrated networks are present.6

Dunbar and co-workers discovered that CuI(TCNQ-I)

crystallised in two forms that they referred to as phase I and phase II.7 Phase I, which is a semiconductor, consists of two interpenetrating diamondoid networks in which each Cu(I) center is bound to four TCNQ-• units and each TCNQ-• unit is linked to four Cu(I) centers. Within this structure TCNQ-• units, belonging to each of the nets, stack on top of one another to form infinite columns. ACS Paragon Plus Environment


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The second CuI(TCNQ-I) phase also acts as a semi-conductor and although it is a poorer conductor than the phase I form, it displays the interesting electric field-dependent resistance referred to above. The phase II form consists of two interpenetrating CuI(TCNQ-I) networks each with the PtS topology and with all TCNQ-• units and Cu(I) centers serving as 4-connecting nodes. Until the introduction of the TCNQH2 synthetic approach described below, it had generally proved difficult to obtain metal derivatives of TCNQ in a form suitable for single crystal X-ray diffraction studies and although the interesting properties of certain TCNQ/metal combinations had been explored, the materials were commonly of indefinite composition and structure.8

Easily

obtained TCNQH2, structure II, affords a very convenient starting material for the synthesis of an extensive range of coordination polymers of the TCNQ2- ligand in a form suitable for single crystal X-ray diffraction studies.9-15 In contrast to earlier coordination polymers of the TCNQ-· radical anion in which the TCNQ moieties are in close contact, the TCNQ2- ligands in the derived coordination polymers are commonly, spatially well separated. One of our longer term objectives is to partially oxidise such TCNQ2--based coordination polymers to a mixed TCNQ1-/TCNQ2- oxidation state. In the present paper we report a range of compounds consisting of [CuI2(TCNQ-II)]0 and [CuI2(F4TCNQ-II)]0 coordination polymers combined with various co-ligands (where F4TCNQ2- is the 2,3,5,6-tetrafluorinated analogue of TCNQ2-).

Experimental General synthesis TCNQH214 and F4TCNQH216 were prepared as previously reported. In the synthesis of all the copper compounds, [Cu(MeCN)4]ClO4 in CH3CN was combined with a solution of the co-ligand in either MeOH or EtOH. This solution was slowly diffused into a solution of TCNQH2 or F4TCNQH2 in either DMF or DMSO. Either the co-ligand or LiOAc was employed as the base used in the deprotonation of the tetracyano ligand. Detailed syntheses are provided in Supporting Information.


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Crystallographic details All data were collected on an Oxford Diffraction SuperNova diffractometer except for [CuI2(TCNQ-II)(2,5-dimethylpyrazine)2], which was collected at the Australian Synchrotron. All compounds were transferred directly from the mother liquor into protective oil and placed under a stream of N2. Structures were solved by direct methods and refined using a full matrix least-squares procedure based on F2 (SHELX97),17 within the WinGX suite of programs.18

Crystal data for Cu2(F4TCNQ)(2,6-lutidine)2: C26H18Cu2F4N6, FW = 617.54, triclinic, P-1, a = 7.6593(5) Å, b = 7.6693(6) Å, c = 11.3462(8) Å, α = 100.363(6)°, β = 101.345(6)°, γ = 101.104(6)°, V = 624.59(8) Å3, Z = 1, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.642 g cm-1, θmax = 68.49°, no. of measured (and independent) reflections: 4172 (2299), µ = 2.613 mm-1, min./max. apparent transmission ratio: 0.945/0.984, no. of parameters: 174, R1 [I > 2σ(I)] = 0.0401, wR2 (all data) = 0.1240, max./min. residual electron density : 0.478 /-0.415 eÅ-3.

Crystal data for [Cu2(F4TCNQ)(quinoline)2]·DMF: C33H21Cu2 F4N7O, FW = 734.65, triclinic, P-1, a = 7.5552(6) Å, b = 10.3372(9) Å, c = 10.6344(10) Å, α = 66.564(9)°, β = 82.474(7)°, γ = 78.086(7)°, V = 744.51(11) Å3, Z = 1, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.639 g cm-1, θmax = 68.00°, no. of measured (and independent) reflections: 4592 (2702), µ = 2.336 mm-1, min./max. apparent transmission ratio: 0.699/0.932, no. of parameters: 190, R1 [I > 2σ(I)] = 0.0306, wR2 (all data) = 0.0884, max./min. residual electron density : 0.291/ -0.505 eÅ-3.

Crystal data for [Cu2(F4TCNQ)(2-picoline)2]·MeCN: C26H17Cu2F4N7, FW = 630.55, triclinic, P-1, a = 7.5063(5) Å, b = 9.2925(7) Å, c = 10.7697(7) Å, α = 65.132(7)°, β = 84.915(5)°, γ = 67.579(6)°, V = 627.73(9) Å3, Z = 1, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.668 g cm-1, θmax = 67.96°, no. of measured (and independent) reflections: 3930 (2270), µ = 2.621 mm-1, min./max. apparent transmission ratio: 0.761/0.949, no. of parameters: 164, R1 [I > 2σ(I)] = 0.0300, wR2 (all data) = 0.0791, max./min. residual electron density: 0.601/-0.328 eÅ-3. ACS Paragon Plus Environment


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Crystal data for [Cu2(F4TCNQ)(2,2’-bipyridine)2]·2MeOH: C34H24Cu2F4N8O2, FW = 779.69, triclinic, P-1, a = 7.3260(7) Å, b = 9.4851(11) Å, c = 12.2439(11) Å, α = 75.849(8)°, β = 80.341(7)°, γ = 77.374(9)°, V = 799.13(15) Å3, Z = 1, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.620 g cm-1, θmax = 67.48°, no. of measured and independent reflections: 5210, µ = 2.266 mm-1, min./max. apparent transmission ratio: 0.716/0.950, no. of parameters: 225, R1 [I > 2σ(I)] = 0.0461, wR2 (all data) = 0.1291, max./min. residual electron density : 0.712/ -0.359 eÅ-3.

Crystal data for [Cu2(TCNQ)(2,2’-bipyridine)2]·2H2O: C32H24Cu2N8O2, FW = 679.67, triclinic, P-1, a = 7.5403(3) Å, b = 9.5112(4) Å, c = 11.6339(6) Å, α = 75.108(4)°, β = 82.444(4)°, γ = 76.994(3)°, V = 783.24(6) Å3, Z = 1, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.441 g cm-1, θmax = 67.48°, no. of measured (and independent) reflections: 4828 (2809), µ = 2.020 mm-1, min./max. apparent transmission ratio: 0.739/0.894, no. of parameters: 206, R1 [I > 2σ(I)] = 0.0405, wR2 (all data) = 0.1309, max./min. residual electron density : 0.940/ -0.256 eÅ-3.

Crystal data for [Cu2(TCNQ)(1,10-phenanthroline)2]·MeOH: C37H24Cu2N8O, FW = 723.72, triclinic, P-1, a = 7.4366(8) Å, b = 10.2836(11) Å, c = 12.2532(9) Å, α = 74.646(9)°, β = 83.290(8)°, γ = 73.618(9)°, V = 866.03(15) Å3, Z = 1, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.388 g cm-1, θmax = 67.49°, no. of measured (and independent) reflections: 5892 (3113), µ = 1.844 mm-1, min./max. apparent transmission ratio: 0.849/0.895, no. of parameters: 224, R1 [I > 2σ(I)] = 0.0994, wR2 (all data) = 0.3206, max./min. residual electron density : 1.737/ -0.549 eÅ-3.

Crystal data for Cu2(F4TCNQ)(PPh3)3 : C66H45Cu2F4N4P3, FW = 1190.05, triclinic, P-1, a = 13.6794(4) Å, b = 15.0604(6) Å, c = 15.7902(6) Å, α = 62.791(4)°, β = 72.902(3)°, γ = 82.785(3)°, V = 2765.07(17) Å3, Z = 2, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.429 g cm-1, θmax = 68.00°, no. of measured (and independent) reflections: 20147 (9968), µ = 2.263 mm-1, min./max. apparent transmission ratio: 0.743/0.933, no. of parameters: 712, R1 [I > 2σ(I)] = 0.0337, wR2 (all data) = 0.0935, max./min. residual electron density : 0.397/ -0.493 eÅ-3. ACS Paragon Plus Environment

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Crystal data for Cu2(F4TCNQ)(PPh3)4: C84H60Cu2F4N4P4, FW = 1452.32, monoclinic, C2/c, a = 20.4237(6) Å, b = 10.9154(2) Å, c = 32.3750(7) Å, β = 100.928(2)°, V = 7086.6(3) Å3, Z = 4, λ = 0.71073 Å, T = 130 K, ρcalcd = 1.361 g cm-1, θmax = 28.26°, no. of measured (and independent) reflections: 17011 (7901), µ = 0.750 mm-1, min./max. apparent transmission ratio 0.855/0.964, no. of parameters: 442, R1 [I > 2σ(I)] = 0.0485, wR2 (all data) = 0.1303, max./min. residual electron density: 0.586/-0.450 eÅ-3.

Crystal data for Cu2(TCNQ)(terpyridine)2: C42H26Cu2N10, FW = 797.81, monoclinic, space group C2/c, a = 19.5393(4) Å, b = 7.38780(10) Å, c = 23.8021(5) Å, β = 96.295(2)°, V = 3415.17(11) Å3, Z = 4, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.552 g cm-1, θmax = 67.48°, no. of measured (and independent) reflections: 5932 (3076), µ = 1.928 mm-1, min./max. apparent transmission ratio: 0.935/1.000, no. of parameters: 244, R1 [I > 2σ(I)] = 0.0843, wR2 (all data) = 0.2814, max./min. residual electron density : 0.747/ -1.620 eÅ-3.

Crystal data for [Cu2(TCNQ)(2-picoline)2]·EtOH: C26H24Cu2N6O, FW = 563.59, triclinic, space group P-1, a = 7.6219(4) Å, b = 9.3173(5) Å, c = 10.5299(6) Å, α = 65.050(6)°, β = 85.345(4)°, γ = 66.686(5)°, V = 619.33(7) Å3, Z = 1, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.511 g cm-1, θmax = 73.911°, no. of measured (and independent) reflections: 4974 (2404), µ = 2.363 mm-1, min./max. apparent transmission ratio: 0.684/1.000, no. of parameters: 148, R1 [I > 2σ(I)] = 0.0343, wR2 (all data) = 0.0910, max./min. residual electron density : 0.364/ -0.506 eÅ-3.

Crystal data for Cu2(TCNQ)(4-phenylpyridine)2: C34H22Cu2N6, FW = 641.65, triclinic, space group P-1, a = 7.7912(5) Å, b = 9.5338(7) Å, c = 9.9023(4) , α = 93.423(5)°, β = 95.079(4)°, γ = 111.742(6)°, V = 677.12(7) Å3, Z = 1, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.574 g cm-1, θmax = 70.00°, no. of measured (and independent) reflections: 4497 (2550), µ = 2.222 mm-1, min./max. apparent



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transmission ratio: 0.573/0.850, no. of parameters: 190, R1 [I > 2σ(I)] = 0.0378, wR2 (all data) = 0.1068, max./min. residual electron density : 0.370/ -0.504 eÅ-3.

Crystal data for Cu2(TCNQ)(isoquinoline)2: C30H18Cu2N6, FW = 589.58, triclinic, space group P-1, a = 7.9934(6) Å, b = 8.3301(7) Å, c = 10.1150(7) Å, α = 109.748(7)°, β = 97.865(6)°, γ = 99.444(6)°, V = 611.76(8) Å3, Z = 1, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.600 g cm-1, θmax = 69.96°, no. of measured (and independent) reflections: 4496 (2314), µ = 2.401 mm-1, min./max. apparent transmission ratio: 0.722/1.000, no. of parameters: 172, R1 [I > 2σ(I)] = 0.0620, wR2 (all data) = 0.1721, max./min. residual electron density : 1.680/ -1.500 eÅ3.

Crystal data for

[Cu2(TCNQ)(5,5’-dimethyl-2,2’-bipyridine)2]•2EtOH: C38H40Cu2N8O2, FW =

767.86, orthorhombic, space group Pnnm, a = 25.521(4) Å, b = 9.9070(15) Å, c = 7.4027(14) Å, V = 1871.7(5) Å3, Z = 2, λ = 1.54184 Å, T = 152.98(10) K, ρcalcd = 1.362 g cm-1, θmax = 73.647°, no. of measured (and independent) reflections: 4369 (1965), µ = 1.750

mm-1, min./max. apparent

transmission ratio: 0.722/1.000, no. of parameters: 130, R1 [I > 2σ(I)] = 0.0671, wR2 (all data) = 0.2095, max./min. residual electron density : 0.510/ -0.802 eÅ-3.

Crystal data for Cu2(TCNQ)(quinuclidine)2: C40H56Cu2N8, FW = 776.00, monoclinic, space group P21/n, a = 10.2839(5) Å, b = 17.1644(7) Å, c = 11.0355(7) Å, β = 102.989(5)°, V = 1898.11(17) Å3, Z = 2, λ = 1.54184 Å, T = 240 K, ρcalcd = 1.358 g cm-1, θmax = 69.99°, no. of measured (and independent) reflections: 7442 (3584), µ = 1.681 mm-1, min./max. apparent transmission ratio: 0.262/0.696, no. of parameters: 281, R1 [I > 2σ(I)] = 0.0323, wR2 (all data) = 0.0882, max./min. residual electron density : 0.213/ -0.384 eÅ-3. One of the quinuclidine ligands is disordered over two positions; refer to Supporting Information for further details.

Crystal data for [Cu2(TCNQ)(aminopyrazine)2]·5MeOH 3DMF: C34H51Cu2N13O8, FW = 896.95, monoclinic, space group P2/m, a = 11.0071(4) Å, b = 7.6667(2) Å, c = 14.9346(4) Å, β = ACS Paragon Plus Environment

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103.846(3)°, V = 1223.68(7) Å3, Z = 2, λ = 1.54184 Å, T = 250 K, ρcalcd = 1.217 g cm-1, θmax = 77.023°, no. of measured (and independent) reflections: 5756 (2742), µ = 1.529 mm-1, no. of parameters: 112, R1 [I > 2σ(I)] = 0.0415, wR2 (all data) = 0.1296, max./min. residual electron density : 0.471 / -0.377 eÅ-3. The aminopyrazine ligands are positionally disordered; refer to Supporting Information for further details.

Crystal data for [Cu6(TCNQ)3(N,N’-tetramethylethylenediamine)6]·4CH3CN: C80H120Cu6N28, FW = 1855.28, monoclinic, space group P21/n, a = 18.6921(4) Å, b = 23.3690(6) Å, c = 22.3956(6) Å, β = 101.899(3)°, V = 9572.5(4) Å3, Z = 4, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.287 g cm-1, θmax = 67.50°, no. of measured (and independent) reflections: 47706 (17235), µ = 1.878 mm-1, min./max. apparent transmission ratio: 0.453/0.913, no. of parameters: 1050, R1 [I > 2σ(I)] = 0.0411, wR2 (all data) = 0.1183, max./min. residual electron density : 0.605/ -0.371 eÅ-3. One of the N,N’tetramethylethylenediamine ligands is disordered over two positions; refer to Supporting Information for further details.

Crystal data for [Cu2(TCNQ)(N,N’-tetramethylethylenediamine)2]·2CH3CN: C28H38Cu2N10, FW = 641.76, monoclinic, space group P21/n, a = 8.2544(6) Å, b = 19.8024(14) Å, c = 10.4400(7) Å, β = 104.249(7)°, V = 1654.0(2) Å3, Z = 2, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.289 g cm-1, θmax = 72.43°, no. of measured (and independent) reflections: 6383 (3228), µ = 1.839 mm-1, min./max. apparent transmission ratio: 0.854/1.000, no. of parameters: 209, R1 [I > 2σ(I)] = 0.0715, wR2 (all data) = 0.2150,

max./min.

residual

electron

density

:

1.023/

-1.518

eÅ-3.

The

N,N’-

tetramethylethylenediamine ligands is disordered over two positions; refer to Supporting Information for further details.

Crystal data for

(dipyridiniumbutene)[Cu2Br2(TCNQ)]·2DMSO: C30H32Br2Cu2N6O2S2,

FW =

859.63, monoclinic, space group I2/m, a = 16.446(5) Å, b = 7.763(5) Å, c = 13.690(5) Å, β = 94.214(5)°, V = 1743.1(14) Å3, Z = 2, λ = 1.54184 Å, T = 130 K, ρcalcd = 1.638 g cm-1, θmax = ACS Paragon Plus Environment


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68.996°, no. of measured (and independent) reflections: 3347 (1746), µ = 5.604 mm-1, min./max. apparent transmission ratio: 0.284/0.704, no. of parameters: 130, R1 [I > 2σ(I)] = 0.0309, wR2 (all data) = 0.0778, max./min. residual electron density : 0.815/ -1.067 eÅ-3. Within the structure both the bromide ligand and the dipyridiniumbutene cation are disordered; refer to Supporting Information for further details.

Crystal data for Cu2(TCNQ)(2,5-dimethylpyrazine): C18H12Cu2N6, FW = 439.42, monoclinic, space group C2/c, a = 7.5420(15) Å, b = 13.738(3) Å, c = 16.532(3) Å, β = 97.15(3)°, V = 1699.6(6) Å3, Z = 4, λ = 0.71073 Å, T = 100 K, ρcalcd = 1.717 g cm-1, θmax = 27.494°, no. of measured (and independent) reflections: 12904 (1898), µ = 2.516 mm-1, no. of parameters: 119, R1 [I > 2σ(I)] = 0.0338, wR2 (all data) = 0.0925, max./min. residual electron density : 0.516/ -0.702 eÅ-3.

Results and discussion We find that the strip-like structure shown in Figure 1 is present in a number of CuI2(TCNQ-II) and CuI2(F4TCNQ-II) coordination polymers with a variety of co-ligands bound to the metal. compounds

CuI2(TCNQ-II)(2-picoline)2,

CuI2(F4TCNQ-II)(2,6-lutidine)2,

CuI2(TCNQ-II)(isoquinoline)2,

The

CuI2(F4TCNQ-II)(2-picoline)2, CuI2(F4TCNQ-II)(quinoline)2,

CuI2(TCNQ-II)(4-phenylpyridine)2, CuI2(F4TCNQ-II)(C2H5CN)215 and [CuI2(TCNQ-II)(Br)2]2-(dpb)2+ {where (dpb)2+ = [(C5H5N)+CH2CH=CHCH2(C5H5N)+]} all have the strip-like structures seen in Figure 1 with one monodentate co-ligand per CuI center which has a coordination number of three. In all of these compounds the strips run parallel with each other and, with the exception of the last example, the co-ligands from one strip interdigitate with those of neighbors. The four Cu(I) centers associated with any particular TCNQ2- or F4TCNQ2- are located at the corners of a rectangle with “long edges” of approximately 10.4 Å and “short edges” of approximately 7.7 Å. It can be seen in Figure 1 that adjacent TCNQ2- or F4TCNQ2- ligands share the long edges of the rectangles. In a hypothetical, idealised polymer of this sort with linear CCNCu moieties and with angles at the ACS Paragon Plus Environment

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methine C atom of 120° the N-Cu-N angles would be 120o – well suited to the requirements of the 3coordinate Cu(I) center. By contrast, hypothetical polymers in which similarly undistorted adjacent ligands share short edges, would have N-Cu-N angles of 60°, much less appropriate for the Cu(I) center.

The ~7.7 Å intervals between the co-ligands along the edges of the strip afford snug

interdigitation with co-ligands from adjacent strips, two examples of which are shown in Figure 2. A closely related form of interdigitation involving monodentate ligands that protrude above and below certain 2D MII(TCNQ-II) sheet coordination polymers at similar intervals has been previously described.15 In all the above examples the normals to the average planes of the strips are parallel. Two strips participating in interdigitation are generally not coplanar, being offset from each other to varying extents.

The C6H4 rings in CuI2(TCNQ-II)(2-picoline)2 and the C6F4 rings

in

CuI2(F4TCNQ-II)(2-picoline)2, are in-plane with their strips, whereas these C6 rings in the other cases are inclined to varying extents relative to the average plane of the strip. The only example of an electrically charged strip containing 3-coordinate CuI reported here is [CuI2(TCNQ-II)Br2]2-(dpb)2+ shown in Figure 3.

One of the pyridinium cationic moieties within

dpb2+ is located above and in close proximity to a dicyanomethanide anionic component of one strip and then the central butene unit within the (dpb)2+ dication snakes downwards to allow the second pyridinium cation of (dpb)2+ to be located below a dicyanomethanide center of a neighboring strip, as can be seen in Figure 3. CuI2(TCNQ-II) or CuI2(F4TCNQ-II) strips very similar to those above, but in which the Cu(I) centers

are

4-coordinate

are

CuI2(TCNQ-II)(2,2’-bipyridine)2,

seen

when

the

co-ligands

CuI2(F4TCNQ-II)(2,2’-bipyridine)2,

are

bidentate,

eg.

in

CuI2(TCNQ-II)(1,10-

phenanthroline)2, CuI2(TCNQ-II)(5,5’-dimethyl-2,2’-bipyridine)2 and CuI2(TCNQ-II)(Me4en)2 (where Me4en = N,N’-tetramethylethylenediamine); in all of these the strips again run parallel.

The

bidentate ligands protrude from the strips at much the same intervals as was seen for the monodentate ligands. When the bidentate ligands are “flat”, “thin” N-aromatics as in 2,2’-bipyridine and 1,10phenanthroline are able to participate in interdigitation very similar to that seen with the monodentate co-ligands; an illustrative example is given in Figure 4 which shows the interdigitating 2,2’ACS Paragon Plus Environment


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bipyridine ligands in CuI2(TCNQ-II)(2,2’-bipyridine)2. In most cases the normals to the strips are parallel, but CuI2(TCNQ-II)(5,5’-dimethyl-2,2’-bipyridine)2

is exceptional in that any strip

interdigitates with four, not two, others and their normals are perpendicular to the normal of the first strip; in this case the gap between any two neighboring 5,5’-dimethyl-2,2’-bipyridine ligands is occupied by parts of 5,5’-dimethyl-2,2’-bipyridine ligands from two separate strips as shown in Figure 5. Reaction of CuI(CH3CN)4+ with tetramethylethylenediamine, Me4en, TCNQH2 in acetonitrile/methanol/DMF yields two visibly different types of crystals.

One type contains

CuI2(TCNQ-II) strips as seen in Figure 1 and the other has the sheet structure described below. The space-filling representation of a CuI2(TCNQ-II)(Me4en)2 strip in Figure 6 clearly indicates that the gap left between two neighboring Me4en co-ligands, which are considerably bulkier than the thin, flat Naromatic bidentates, is too small to allow a co-ligand from a neighboring strip to interdigitate. The strip form of CuI2(TCNQ-II)(Me4en)2 shows no interdigitation. The strips distinctly undulate as can be seen in Figure 7. Acetonitrile molecules occupy some gaps between Me4en ligands. CuI2(TCNQ-II) strips very similar to those above, but in which the Cu(I) centers are 5coordinate are seen when the co-ligand is the tridentate terpyridine (terpy). Two interdigitating strips in this case are shown in Figure 8. It might have been anticipated that the bond between the Cu center and the central N donor of terpy would have been close to in-plane with the strip, but it is immediately apparent in Figure 8 that this is far from the case. There is a pronounced bend at the TCNQ-nitrogen donor centers, as can be seen in Figure 8, so that one of the pyridine moieties of terpy is located close to the plane of the strip. This swivelling of the Cu(terpy) unit presumably maximises the attractive interactions arising from the interdigitation. We note however that the pyridine unit closest to the plane of the strip does not overlap to a significant extent with the interdigitating terpy, as can be seen in Figure 8; this pyridine unit does interact to a smaller extent with the same sort of pyridine from a strip outside the pair under consideration (but for simplicity this additional minor interaction is omitted from Figure 8).


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The same CuI2(TCNQ-II) strips occur as part of a 3D coordination polymer in CuI2(TCNQ-II)(2-aminopyrazine)2, in which the 2-aminopyrazine ligands act as bridges between CuI centers that are 4-coordinate as shown in Figure 9. The Cu centers along one edge of a strip are all attached to two N(1) donors of the 2-aminopyrazine whilst the Cu centers along the other edge are attached to two N(4) donors. Interestingly the network has the same topology as a solvated form of cadmium cyanide [Cd(CN)2(H2O)2/3]·t-BuOH (honeycomb cadmium cyanide) that we reported in 1989.19 Reaction

of

F4TCNQH2

with

Cu(CH3CN)4+,

LiOAc

and

triphenylphosphine

in

methanol/acetonitrile yields crystals of CuI2(F4TCNQ-II)[P(C6H5)3]3 which contains strips of the type seen in Figure 1, together with a second type of crystal of composition CuI2(F4TCNQ-II)[P(C6H5)3]4, which has the 2D sheet structure discussed below. As shown in Figure 10, half the Cu centers in CuI2(F4TCNQ-II)[P(C6H5)3]3 are 4-coordinate bearing two coordinated triphenylphosphines and the others are 3-coordinate with a single triphenylphosphine ligand. Along an edge of the strip the two types of Cu(I) center alternate. Directly opposite a 4-coordinate Cu center on one edge is a 3coordinate Cu on the other edge as can be seen in Figure 10. One of the Cu-P bonds at the 4coordinate Cu center is directed “outwards” away from the strip, whilst the other is oriented so that two of its phenyl substituents are brought into close contact with the F4TCNQ-II “surface” of the strip. Two C6F4 rings that make close contact with one of these phenyl groups, easily discernible in Figure 10, are swivelled around the C-C bonds connecting them to the “methine” C centers presumably so as to minimise the clash with the phenyl group. There are several close C···C and C···F contacts (3.1 3.4 Å) between the phenyl groups and the C6F4 rings in these regions. As can be seen in Figure 10 the C6F4 rings alternate in the direction of their inclination to the average plane of the strip. The second type of crystal of composition CuI2(F4TCNQ-II)[P(C6H5)3]4 has the 2D sheet structure shown in Figure 11. All the C6F4 rings are perpendicular to the average plane of the sheet. The planes of the two C(CN)2 moieties associated with any given F4TCNQ-II ligand are perpendicular to each other and at 45° to the C6F4 rings as can be seen in Figure 11. The sheet resembles a sandwich, the “bread” of which is provided by the phenyl groups of the phosphine ligands and the ACS Paragon Plus Environment


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“meat” by the CuI2(F4TCNQ-II) coordination network, which adopts a far from planar, puckered configuration with the plane containing half the Cu(I) centers well separated from the plane of the other half. As can be seen in Figure 11 one phenyl ring from each triphenylphosphine is directed towards the interior of the CuI2(F4TCNQ-II) coordination network. Reaction of TCNQH2 with Cu(CH3CN)4+, LiOAc and quinuclidine in methanol/acetonitrile yields crystals of CuI2(TCNQ-II)[quinuclidine]4, which has the sheet structure shown in Figure 12. As can be seen in the Figure 12b the 2D CuI2(TCNQ-II) coordination network is highly corrugated with the Cu/quinuclidine components located at the crests and troughs. It was indicated above that when N,N’-tetramethylethylenediamine is used as the co-ligand two types of crystals of composition CuI2(TCNQ-II)(Me4en)2 are formed in the same reaction mixture. One form, considered above, has the strip structure shown in Figures 6 and 7, whilst the other has the 2D sheet structure shown in Figure 13. The 2D CuI2(TCNQ-II) coordination network in this case, in contrast to that in CuI2(TCNQ-II)[quinuclidine]4, is very close to coplanar. As shown in Figure 13b two Me4en ligands are snugly incorporated, into each of the rings in the CuI2(TCNQ-II) sheets, all rings being equivalent. Reaction of CuI(CH3CN)4+ with TCNQH2 and 2,5-dimethylpyrazine (Me2pz) in acetonitrile/DMSO affords crystals of composition CuI2(TCNQ-II)(Me2pz), which have the sheet structure shown in Figure 14. The individual sheets are almost completely planar allowing adjacent sheets to form numerous close contacts (eg. Cu···Cu, 3.204; Cu···ring C of TCNQ, 3.201; Cu···N of TCNQ, 3.233 Å). Despite the very different geometries of the sheet structures in CuI2(F4TCNQ-II)[P(C6H5)3]4, (Figure 11), CuI2(TCNQ-II)[quinuclidine]4, (Figure 12), CuI2(TCNQ-II)(Me4en)2 (Figure 13), and CuI2(TCNQ-II)(Me2pz), (Figure 14), the topologies of the CuI2(TCNQ-II) or CuI2(F4TCNQ-II) coordination networks are identical.

The geometrically most symmetrical possible version

(hypothetical) of this shared topology is shown in Figure 15. The connectivities underlying the strip structures (as in Figure 1) and those underlying the sheet networks (as in Figure 15) merely represent two alternative simple ways of generating ACS Paragon Plus Environment

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electrically neutral CuI2(TCNQ-II) or CuI2(F4TCNQ-II) coordination assemblies in which every tetracyano ligand is bound to four Cu centers which in turn are each attached to two ligands. It appears that “thin”, “flat” co-ligands such as the aromatic N-heterocyclic systems, predispose the system to adopt the strip topology which provides a co-ligand-to-co-ligand separation nicely appropriate for stabilising interdigitation, whereas more congested co-ligands that are sterically unable to interdigitate when attached to the strip (e.g. Me4en, P(C6H5)3), may give either the strip unsupported by interdigitation or the 2D sheet connectivity.

In the particular case of

CuI2(TCNQ-II)(Me2pz), the Me2pz ligand has a length that enables it to bridge diametrically opposed Cu centers in the Cu4(ligand)4 metallocycles in the hypothetical net shown in Figure 15, to give an almost exactly coplanar sheet with 3-connected Cu centers (as seen in Figure 14). In a related way, Me4en is small enough relative to these Cu4(ligand)4 metallocycles for two of these ligands to chelate to diametrically opposed Cu centers, fitting snugly “back to back” within a CuI2(TCNQ-II) network which is able to remain almost coplanar. By contrast it is not possible to accommodate bulky ligands such as quinuclidine and triphenylphosphine within a nearly planar CuI2(TCNQ-II) network which therefore adopts a very convoluted configuration in order to bind the ligands. The ways in which the convolution is achieved are quite different for quinuclidine and triphenylphosphine. The diverse geometries of the 2D CuI2(TCNQ-II) {or CuI2(F4TCNQ-II)} coordination networks seen in Figures 11, 12, 13 and 14 are testament to the ready flexibility of TCNQ2-/metal polymers; only minor bending at the various atoms of the MNCCCNM moieties is required to achieve very different dispositions of the metal centers. The possibility of rotation of one MNCCCNM unit relative to the other within the same ligand, as in CuI2(F4TCNQ-II)[P(C6H5)3]2 (Figure 11), (where the two MNCCCNM systems are in fact perpendicular to each other) provides a very significant additional element of flexibility. We note that the strips seen in Figure 1 are a central feature of the wide range of 3D PtSrelated networks of composition X+[CuI(TCNQ-II)]-1 or X+[CuI(F4TCNQ-II)]-1, in which any one of the Cu centers (all being equivalent) is shared by two strips as shown in Figure 16.12



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Strip structures of the type seen in Figure 1 or sheet structures of the type seen in Figure 15 in which the tetracyano components have been partially oxidised to an average oxidation state somewhere between –I and –II may afford interesting electronic properties.

Acknowledgements We gratefully acknowledge the financial support of the Australian Research Council. Part of the research reported was undertaken at the macromolecular crystallography beamline at the Australian Synchrotron, Victoria, Australia. R.W.E. and A.L.S. gratefully acknowledge the receipt of Australian Postgraduate Awards from the Australian Government.

Supporting Information Syntheses, XRD and selected figures; crystallographic information files (CIF). This material is available free of charge via the Internet at http://pubs.acs.org.


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References 1.

D. Acker and W. Hertler, J. Am. Chem. Soc., 1962, 84, 3370–3374.

2.

J. Ferraris, D. O. Cowan, V. Walatka and J. H. Perlstein, J. Am. Chem. Soc., 1973, 95, 948– 949.

3.

S. A. O’Kane, R. Clérac, H. Zhao, X. Ouyang, J. R. Galán-Mascarós, R. Heintz and K. R. Dunbar, J. Solid State Chem., 2000, 152, 159–173.

4.

H. Zhao, M. J. Bazile, J. R. Galán-Mascarós and K. R. Dunbar, Angew. Chem. Int. Ed. Engl., 2003, 42, 1015–1018.

5.

L. Shields, J. Chem. Soc. Faraday Trans. 2, 1985, 81, 1-9.

6.

R. Robson, Comprehensive Supramolecular Chemistry, Volume 6, Pergamon Press, U.K., 1996.

7.

R. A. Heintz, H. Zhao, X. Ouyang, G. Grandinetti, J. Cowen and K. R. Dunbar, Inorg. Chem. 1999, 38, 144-156.

8.

E. B. Vickers, I. D. Giles and J. S. Miller, Chem. Mater., 2005, 17, 1667–1672.

9.

B. F. Abrahams, T. A. Hudson and R. Robson, Cryst. Growth Des., 2008, 8, 1123–1125.

10.

B. F. Abrahams, R. W. Elliott, T. A. Hudson and R. Robson, Cryst. Growth Des., 2010, 10, 2860–2862.

11.

B. F. Abrahams, R. W. Elliott, T. A. Hudson and R. Robson, CrystEngComm, 2012, 14, 351354.

12.

B. F. Abrahams, R. W. Elliott, T. A. Hudson and R. Robson, Cryst. Growth Des., 2013, 13, 3018–3027.

13.

M. R. Saber, A. V Prosvirin, B. F. Abrahams, R. W. Elliott, R. Robson and K. R. Dunbar, Chem. – A Eur. J., 2014, 20, 7593-7597.

14.

B. F. Abrahams, R. W. Elliott, and R. Robson, Aust J. Chem., 2014, 67, 1871-1877.

15.

T. Le, A. Nafady, N. Vo, R. W. Elliott, T. A. Hudson, R. Robson, B. F. Abrahams, L. L. Martin, and A. M. Bond, Inorg. Chem., 2014, 53, 3230–3242.

16.

E. L. Martin, Fluoro and Cyano-Substituted 7,7,8,8-Tetracyanoquinodimethans and Intermediates Thereto, U.S. Patent 3,558,671, Jan. 26, 1971.

17.

Sheldrick, G. M., SHELX97-Programs for Crystal Structure Analysis, release 97-2; Institut fur Anorganische Chemie der Universitat Gottingen: Gottingen, Germany, 1998.

18.

L. J. Farrugia, J. Appl. Crystallogr. 1999, 32, 837-838.

19.

B. F. Abrahams, B. F. Hoskins and R. Robson, Chem. Comm., 1989, 60-61.



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I

II

Figure 1. The strip-like structure common to a number of CuI2(TCNQ-II) and CuI2(F4TCNQ-II) coordination polymers. The four H or F substituents of the C6 rings have been omitted. Various coligands, not shown here, are attached to the CuI centers.


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a)

b

Figure

2.

Two

interdigitating

strips

in

a)

CuI2(TCNQ-II)(4-phenylpyridine)2,

CuI2(F4TCNQ-II)(quinoline)2.


and

b)


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Figure 3. Representation of the way the (dpb)2+ cation binds strip to strip in [CuI2(TCNQ-II)(Br)2]2(dpb)2+ .


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Figure 4. Two strips in CuI(TCNQ-II)(2,2’-bipyridine)2 showing the interdigitating bipyridine units.



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Figure 5. A view of one strip in CuI2(TCNQ-II)(5,5’-dimethyl-2,2’-bipyridine)2 together with four others that interdigitate with it. The normal to the central strip is perpendicular to those of the four interdigitating strips.


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Figure 6. A space-filling representation of a strip in CuI2(TCNQ-II)(Me4en)2 revealing that the space between Me4en co-ligands is too small to allow interdigitation.



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Figure 7. The undulating strip in the strip form of CuI2(TCNQ-II)(Me4en)2.


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Figure 8. Two interdigitating strips in CuI2(TCNQ-II)(terpy).



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Figure 9. The structure of the 3D coordination polymer CuI2(TCNQ-II)(2-aminopyrazine)2.


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Figure 10. The structure of CuI2(F4TCNQ-II)[P(C6H5)3]3.



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a)

b)

Figure 11. a) The 2D sheet structure of CuI2(F4TCNQ-II)[P(C6H5)3]4 viewed almost perpendicular to the average plane of the sheet. For clarity only four P(C6H5)3 ligands are shown here, a pair above the CuI2(F4TCNQ-II) system attached to the same Cu(I) center and a pair below. CuI2(F4TCNQ-II)[P(C6H5)3]4 sheets viewed edge-on.


b) Two

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a)

b )

Figure 12. a) The CuI2(TCNQ-II) coordination network in CuI2(TCNQ-II)[quinuclidine]4, from which the quinuclidine components have been omitted for clarity. b) The highly corrugated structure of CuI2(TCNQ-II)[quinuclidine]4 seen here almost edge-on.



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a)

b )

Figure 13.

a) The 2D CuI2(TCNQ-II) coordination network in the sheet form of

CuI2(TCNQ-II)(Me4en)2 showing a central ring which is surrounded by six others. The Me4en ligands are omitted for clarity. b) The central ring in a) seen from the same angle but with the Me4en ligands now included. All rings are equivalent.


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Figure 14. The structure of a sheet in CuI2(TCNQ-II)(Me2pz).



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Figure 15.

The hypothetical, geometrically most symmetrical form of the CuI2(TCNQ-II) {or

CuI2(F4TCNQ-II)} coordination network topology underlying those present in CuI2(F4TCNQII

)[P(C6H5)3]4, CuI2(TCNQ-II)[quinuclidine]4, CuI2(TCNQ-II)( Me4en )2 and CuI2(TCNQ-II)(Me2pz).


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Figure 16.

A wide range of 3D PtS-related networks of composition X+[CuI(TCNQ-II)]-1 or

X+[CuI(F4TCNQ-II)]-1 contain strips of the type seen in Figure 1 in which every Cu center is shared by two strips.



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For Table of Contents use only

New CuI2(TCNQ-II) and CuI2(F4TCNQ-II) coordination polymers Brendan F. Abrahams,* Robert W. Elliott, Timothy A. Hudson, Richard Robson* and Ashley L. Sutton School of Chemistry, University of Melbourne, Victoria 3010, Australia.

Synopsis

In a wide range of CuI2(TCNQ-II) or CuI2(F4TCNQ-II) coordination polymers with various co-ligands, two simple topological motifs, strips and sheets, are seen, in all of which Cu centers are bound to a pair of tetracyano groups which in turn are bound to four Cu(I) centers.

TOC graphic


Coordination Polymers - American Chemical Society

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