Electrocrystallization and structural and physical properties of charge-transfer complexes derived from [(η6-C6Me6)2M]2+ (M = Fe, Ru) and TCNQ (TCNQ = tetracyanoquinodimethane)

Michael Ward, D. C. Johnson

Research output: Contribution to journalArticle

Abstract

Charge-transfer complexes [(η6-C6Me6)2M][TCNQ]x (M = Fe, Ru; x = 2, 4; TCNQ = tetracyanoquinodimethane) and [(η6-C6Me6)2M][TCNQ′] 2 (M = Fe, Ru; TCNQ′ = (TCNQ)Cl2, (TCNQ)F4) are prepared with electrocrystallization techniques by reduction of TCNQ or TCNQ′ in the presence of [(η6-C6Me6)2M]2+. Selectivity toward the TCNQ phases can be directed electrochemically by control of the electrode potential during electrocrystallization. At very negative potentials a poorly conducting 1:2 phase is formed as a deep purple crystalline solid, whereas more positive potentials favor a black, conducting 1:4 phase. The selectivity is determined by the potential-dependent concentrations of TCNQ and TCNQ- at the electrode. Complexes with anions possessing halogen substituents (e.g., (TCNQ)Cl2, (TCNQ)F4) only crystallize as 1:2 phases, presumably due to decreased Coulombic repulsion between associated anions. Conversely, only conducting phases are observed with derivatives possessing electron-donating substituents (e.g., (TCNQ)Me2, TCNQ(OMe)2). The single-crystal X-ray structures of the 1:2 phases, which all crystallize in the triclinic P1 space group, are reported. For [(η6-C6Me6)2M][TCNQ] 2, for M = Fe [Ru], a = 10.167 (2) [11.350 (7)] Å, b = 11.281 (3) [9.163 (3)] Å, c = 9.187 (1) [10.184 (5)] Å, α = 111.08 (2) [91.82 (5)]°, β = 98.10 (1) [110.89 (4)]°, γ = 92.37 (2) [98.19 (3)]°, V = 968.5 [976 (2)] Å3, Z = 1 [1], d = 1.35 [1.42] g cm-3, Ru = 0.046 [0.039], and Rw = 0.052 [0.043]. For [(η6-C6Me6)2M][(TCNQ)F 4]2, for M = Fe [Ru], a = 10.140 (3) [10.143 (8)] Å, 6 = 10.907 (4) [10.830 (2)] Å, c = 10.056 (4) [10.092 (5)] Å, α = 95.74 (3) [92.11 (4)]°, β = 93.72 (3) [96.40 (3)]°, γ = 92.35 (3) [94.40 (5)]°, V = 1103.0 [1097 (2)] Å3, Z = 1 [1], d = 1.50 [1.57] g cm-3, Ru = 0.068 [0.065], and Rw = 0.082 [0.073]. For [(η6-C6Me6)2M][(TCNQ)Cl 2]2, for M = Fe [Ru], a = 9.985 (6) [9.993 (11)] Å, b = 11.116 (5) [11.225 (10)] Å, c = 9.725 (7) [9.838 (6)] Å, α = 104.28 (7) [89.21 (8)]°, β = 98.07 (5) [75.36 (7)]°, γ = 89.88 (6) [81.98 (7)]°, V = 1035 (2) [1057 (2)] Å3, Z = 1 [1], d = 1.49 [1.42] g cm-3, Ru = 0.078 [0.069], and Rw = 0.097 [0.075]. The structures of the [(η6-C6Me6)2M]2+ cations are reported here for the first time; the average Fe-C, C-C, and C-Me distances are 2.156, 1.411, and 1.505 Å, respectively, whereas the average Ru-C, C-C, and C-Me distances are 2.257, 1.426, and 1.501 Å, respectively. The 1:2 phases possess dimer dianions that exhibit ring-ring overlap and intradimer separations (Å) decreasing in the order TCNQ (3.23) > (TCNQ)Cl2 (3.21) > (TCNQ)F4 (3.17). The [TCNQ]2 2- dimer forms mixed-stack linear chains with the organometallic dications, i.e., ...DAADAADAA..., with the molecular planes of the [TCNQ]2 2- dimer parallel to the hexamethylbenzene rings of the cations. The interplanar separations between the hexamethylbenzene ligand and the nearest TCNQ anion are greater than 3.6 A. Extended mixed-stack linear chains are also observed when TCNQ′ = (TCNQ)Cl2 or (TCNQ)F4; however, the [TCNQ′]2 2- dimer is stacked "end on" between the cations with the long molecular axes of the TCNQ anions roughly parallel to the linear-chain axes. Close intermolecular contacts between the cyano nitrogen atoms and the ring carbons of the cation that are significantly less than the sum of the van der Waals radii are observed, suggesting a unique type of donor-acceptor interaction. The compounds with 1:2 stoichiometry have relatively low conductivities (σ300 K < 10-7 Ω-1 cm-1) and diamagnetic, temperature-independent magnetic susceptibilities. In contrast, the 1:4 phases exhibit much higher conductivity (σ300 K = 0.1 Ω-1 cm-1) with temperature dependence indicating semiconducting behavior (EA = 0.06 eV), which is explained in terms of electron localization along extended TCNQ arrays as a result of Coulombic repulsion. The 1:4 phases exhibit temperature-dependent paramagnetic susceptibilities consistent with the random exchange Heisenberg antiferromagnetic exchange (REHAC) model.

Original languageEnglish (US)
Pages (from-to)4213-4227
Number of pages15
JournalInorganic Chemistry
Volume26
Issue number25
StatePublished - 1987

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Charge transfer
Structural properties
Physical properties
physical properties
dimers
charge transfer
anions
cations
rings
conduction
selectivity
magnetic permeability
low conductivity
electrodes
halogens
nitrogen atoms
stoichiometry
electrons
conductivity
temperature dependence

ASJC Scopus subject areas

  • Inorganic Chemistry

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@article{7e1dff4005694a8fbbe043a95cdf2ec5,
title = "Electrocrystallization and structural and physical properties of charge-transfer complexes derived from [(η6-C6Me6)2M]2+ (M = Fe, Ru) and TCNQ (TCNQ = tetracyanoquinodimethane)",
abstract = "Charge-transfer complexes [(η6-C6Me6)2M][TCNQ]x (M = Fe, Ru; x = 2, 4; TCNQ = tetracyanoquinodimethane) and [(η6-C6Me6)2M][TCNQ′] 2 (M = Fe, Ru; TCNQ′ = (TCNQ)Cl2, (TCNQ)F4) are prepared with electrocrystallization techniques by reduction of TCNQ or TCNQ′ in the presence of [(η6-C6Me6)2M]2+. Selectivity toward the TCNQ phases can be directed electrochemically by control of the electrode potential during electrocrystallization. At very negative potentials a poorly conducting 1:2 phase is formed as a deep purple crystalline solid, whereas more positive potentials favor a black, conducting 1:4 phase. The selectivity is determined by the potential-dependent concentrations of TCNQ and TCNQ- at the electrode. Complexes with anions possessing halogen substituents (e.g., (TCNQ)Cl2, (TCNQ)F4) only crystallize as 1:2 phases, presumably due to decreased Coulombic repulsion between associated anions. Conversely, only conducting phases are observed with derivatives possessing electron-donating substituents (e.g., (TCNQ)Me2, TCNQ(OMe)2). The single-crystal X-ray structures of the 1:2 phases, which all crystallize in the triclinic P1 space group, are reported. For [(η6-C6Me6)2M][TCNQ] 2, for M = Fe [Ru], a = 10.167 (2) [11.350 (7)] {\AA}, b = 11.281 (3) [9.163 (3)] {\AA}, c = 9.187 (1) [10.184 (5)] {\AA}, α = 111.08 (2) [91.82 (5)]°, β = 98.10 (1) [110.89 (4)]°, γ = 92.37 (2) [98.19 (3)]°, V = 968.5 [976 (2)] {\AA}3, Z = 1 [1], d = 1.35 [1.42] g cm-3, Ru = 0.046 [0.039], and Rw = 0.052 [0.043]. For [(η6-C6Me6)2M][(TCNQ)F 4]2, for M = Fe [Ru], a = 10.140 (3) [10.143 (8)] {\AA}, 6 = 10.907 (4) [10.830 (2)] {\AA}, c = 10.056 (4) [10.092 (5)] {\AA}, α = 95.74 (3) [92.11 (4)]°, β = 93.72 (3) [96.40 (3)]°, γ = 92.35 (3) [94.40 (5)]°, V = 1103.0 [1097 (2)] {\AA}3, Z = 1 [1], d = 1.50 [1.57] g cm-3, Ru = 0.068 [0.065], and Rw = 0.082 [0.073]. For [(η6-C6Me6)2M][(TCNQ)Cl 2]2, for M = Fe [Ru], a = 9.985 (6) [9.993 (11)] {\AA}, b = 11.116 (5) [11.225 (10)] {\AA}, c = 9.725 (7) [9.838 (6)] {\AA}, α = 104.28 (7) [89.21 (8)]°, β = 98.07 (5) [75.36 (7)]°, γ = 89.88 (6) [81.98 (7)]°, V = 1035 (2) [1057 (2)] {\AA}3, Z = 1 [1], d = 1.49 [1.42] g cm-3, Ru = 0.078 [0.069], and Rw = 0.097 [0.075]. The structures of the [(η6-C6Me6)2M]2+ cations are reported here for the first time; the average Fe-C, C-C, and C-Me distances are 2.156, 1.411, and 1.505 {\AA}, respectively, whereas the average Ru-C, C-C, and C-Me distances are 2.257, 1.426, and 1.501 {\AA}, respectively. The 1:2 phases possess dimer dianions that exhibit ring-ring overlap and intradimer separations ({\AA}) decreasing in the order TCNQ (3.23) > (TCNQ)Cl2 (3.21) > (TCNQ)F4 (3.17). The [TCNQ]2 2- dimer forms mixed-stack linear chains with the organometallic dications, i.e., ...DAADAADAA..., with the molecular planes of the [TCNQ]2 2- dimer parallel to the hexamethylbenzene rings of the cations. The interplanar separations between the hexamethylbenzene ligand and the nearest TCNQ anion are greater than 3.6 A. Extended mixed-stack linear chains are also observed when TCNQ′ = (TCNQ)Cl2 or (TCNQ)F4; however, the [TCNQ′]2 2- dimer is stacked {"}end on{"} between the cations with the long molecular axes of the TCNQ anions roughly parallel to the linear-chain axes. Close intermolecular contacts between the cyano nitrogen atoms and the ring carbons of the cation that are significantly less than the sum of the van der Waals radii are observed, suggesting a unique type of donor-acceptor interaction. The compounds with 1:2 stoichiometry have relatively low conductivities (σ300 K < 10-7 Ω-1 cm-1) and diamagnetic, temperature-independent magnetic susceptibilities. In contrast, the 1:4 phases exhibit much higher conductivity (σ300 K = 0.1 Ω-1 cm-1) with temperature dependence indicating semiconducting behavior (EA = 0.06 eV), which is explained in terms of electron localization along extended TCNQ arrays as a result of Coulombic repulsion. The 1:4 phases exhibit temperature-dependent paramagnetic susceptibilities consistent with the random exchange Heisenberg antiferromagnetic exchange (REHAC) model.",
author = "Michael Ward and Johnson, {D. C.}",
year = "1987",
language = "English (US)",
volume = "26",
pages = "4213--4227",
journal = "Inorganic Chemistry",
issn = "0020-1669",
publisher = "American Chemical Society",
number = "25",

}

TY - JOUR

T1 - Electrocrystallization and structural and physical properties of charge-transfer complexes derived from [(η6-C6Me6)2M]2+ (M = Fe, Ru) and TCNQ (TCNQ = tetracyanoquinodimethane)

AU - Ward, Michael

AU - Johnson, D. C.

PY - 1987

Y1 - 1987

N2 - Charge-transfer complexes [(η6-C6Me6)2M][TCNQ]x (M = Fe, Ru; x = 2, 4; TCNQ = tetracyanoquinodimethane) and [(η6-C6Me6)2M][TCNQ′] 2 (M = Fe, Ru; TCNQ′ = (TCNQ)Cl2, (TCNQ)F4) are prepared with electrocrystallization techniques by reduction of TCNQ or TCNQ′ in the presence of [(η6-C6Me6)2M]2+. Selectivity toward the TCNQ phases can be directed electrochemically by control of the electrode potential during electrocrystallization. At very negative potentials a poorly conducting 1:2 phase is formed as a deep purple crystalline solid, whereas more positive potentials favor a black, conducting 1:4 phase. The selectivity is determined by the potential-dependent concentrations of TCNQ and TCNQ- at the electrode. Complexes with anions possessing halogen substituents (e.g., (TCNQ)Cl2, (TCNQ)F4) only crystallize as 1:2 phases, presumably due to decreased Coulombic repulsion between associated anions. Conversely, only conducting phases are observed with derivatives possessing electron-donating substituents (e.g., (TCNQ)Me2, TCNQ(OMe)2). The single-crystal X-ray structures of the 1:2 phases, which all crystallize in the triclinic P1 space group, are reported. For [(η6-C6Me6)2M][TCNQ] 2, for M = Fe [Ru], a = 10.167 (2) [11.350 (7)] Å, b = 11.281 (3) [9.163 (3)] Å, c = 9.187 (1) [10.184 (5)] Å, α = 111.08 (2) [91.82 (5)]°, β = 98.10 (1) [110.89 (4)]°, γ = 92.37 (2) [98.19 (3)]°, V = 968.5 [976 (2)] Å3, Z = 1 [1], d = 1.35 [1.42] g cm-3, Ru = 0.046 [0.039], and Rw = 0.052 [0.043]. For [(η6-C6Me6)2M][(TCNQ)F 4]2, for M = Fe [Ru], a = 10.140 (3) [10.143 (8)] Å, 6 = 10.907 (4) [10.830 (2)] Å, c = 10.056 (4) [10.092 (5)] Å, α = 95.74 (3) [92.11 (4)]°, β = 93.72 (3) [96.40 (3)]°, γ = 92.35 (3) [94.40 (5)]°, V = 1103.0 [1097 (2)] Å3, Z = 1 [1], d = 1.50 [1.57] g cm-3, Ru = 0.068 [0.065], and Rw = 0.082 [0.073]. For [(η6-C6Me6)2M][(TCNQ)Cl 2]2, for M = Fe [Ru], a = 9.985 (6) [9.993 (11)] Å, b = 11.116 (5) [11.225 (10)] Å, c = 9.725 (7) [9.838 (6)] Å, α = 104.28 (7) [89.21 (8)]°, β = 98.07 (5) [75.36 (7)]°, γ = 89.88 (6) [81.98 (7)]°, V = 1035 (2) [1057 (2)] Å3, Z = 1 [1], d = 1.49 [1.42] g cm-3, Ru = 0.078 [0.069], and Rw = 0.097 [0.075]. The structures of the [(η6-C6Me6)2M]2+ cations are reported here for the first time; the average Fe-C, C-C, and C-Me distances are 2.156, 1.411, and 1.505 Å, respectively, whereas the average Ru-C, C-C, and C-Me distances are 2.257, 1.426, and 1.501 Å, respectively. The 1:2 phases possess dimer dianions that exhibit ring-ring overlap and intradimer separations (Å) decreasing in the order TCNQ (3.23) > (TCNQ)Cl2 (3.21) > (TCNQ)F4 (3.17). The [TCNQ]2 2- dimer forms mixed-stack linear chains with the organometallic dications, i.e., ...DAADAADAA..., with the molecular planes of the [TCNQ]2 2- dimer parallel to the hexamethylbenzene rings of the cations. The interplanar separations between the hexamethylbenzene ligand and the nearest TCNQ anion are greater than 3.6 A. Extended mixed-stack linear chains are also observed when TCNQ′ = (TCNQ)Cl2 or (TCNQ)F4; however, the [TCNQ′]2 2- dimer is stacked "end on" between the cations with the long molecular axes of the TCNQ anions roughly parallel to the linear-chain axes. Close intermolecular contacts between the cyano nitrogen atoms and the ring carbons of the cation that are significantly less than the sum of the van der Waals radii are observed, suggesting a unique type of donor-acceptor interaction. The compounds with 1:2 stoichiometry have relatively low conductivities (σ300 K < 10-7 Ω-1 cm-1) and diamagnetic, temperature-independent magnetic susceptibilities. In contrast, the 1:4 phases exhibit much higher conductivity (σ300 K = 0.1 Ω-1 cm-1) with temperature dependence indicating semiconducting behavior (EA = 0.06 eV), which is explained in terms of electron localization along extended TCNQ arrays as a result of Coulombic repulsion. The 1:4 phases exhibit temperature-dependent paramagnetic susceptibilities consistent with the random exchange Heisenberg antiferromagnetic exchange (REHAC) model.

AB - Charge-transfer complexes [(η6-C6Me6)2M][TCNQ]x (M = Fe, Ru; x = 2, 4; TCNQ = tetracyanoquinodimethane) and [(η6-C6Me6)2M][TCNQ′] 2 (M = Fe, Ru; TCNQ′ = (TCNQ)Cl2, (TCNQ)F4) are prepared with electrocrystallization techniques by reduction of TCNQ or TCNQ′ in the presence of [(η6-C6Me6)2M]2+. Selectivity toward the TCNQ phases can be directed electrochemically by control of the electrode potential during electrocrystallization. At very negative potentials a poorly conducting 1:2 phase is formed as a deep purple crystalline solid, whereas more positive potentials favor a black, conducting 1:4 phase. The selectivity is determined by the potential-dependent concentrations of TCNQ and TCNQ- at the electrode. Complexes with anions possessing halogen substituents (e.g., (TCNQ)Cl2, (TCNQ)F4) only crystallize as 1:2 phases, presumably due to decreased Coulombic repulsion between associated anions. Conversely, only conducting phases are observed with derivatives possessing electron-donating substituents (e.g., (TCNQ)Me2, TCNQ(OMe)2). The single-crystal X-ray structures of the 1:2 phases, which all crystallize in the triclinic P1 space group, are reported. For [(η6-C6Me6)2M][TCNQ] 2, for M = Fe [Ru], a = 10.167 (2) [11.350 (7)] Å, b = 11.281 (3) [9.163 (3)] Å, c = 9.187 (1) [10.184 (5)] Å, α = 111.08 (2) [91.82 (5)]°, β = 98.10 (1) [110.89 (4)]°, γ = 92.37 (2) [98.19 (3)]°, V = 968.5 [976 (2)] Å3, Z = 1 [1], d = 1.35 [1.42] g cm-3, Ru = 0.046 [0.039], and Rw = 0.052 [0.043]. For [(η6-C6Me6)2M][(TCNQ)F 4]2, for M = Fe [Ru], a = 10.140 (3) [10.143 (8)] Å, 6 = 10.907 (4) [10.830 (2)] Å, c = 10.056 (4) [10.092 (5)] Å, α = 95.74 (3) [92.11 (4)]°, β = 93.72 (3) [96.40 (3)]°, γ = 92.35 (3) [94.40 (5)]°, V = 1103.0 [1097 (2)] Å3, Z = 1 [1], d = 1.50 [1.57] g cm-3, Ru = 0.068 [0.065], and Rw = 0.082 [0.073]. For [(η6-C6Me6)2M][(TCNQ)Cl 2]2, for M = Fe [Ru], a = 9.985 (6) [9.993 (11)] Å, b = 11.116 (5) [11.225 (10)] Å, c = 9.725 (7) [9.838 (6)] Å, α = 104.28 (7) [89.21 (8)]°, β = 98.07 (5) [75.36 (7)]°, γ = 89.88 (6) [81.98 (7)]°, V = 1035 (2) [1057 (2)] Å3, Z = 1 [1], d = 1.49 [1.42] g cm-3, Ru = 0.078 [0.069], and Rw = 0.097 [0.075]. The structures of the [(η6-C6Me6)2M]2+ cations are reported here for the first time; the average Fe-C, C-C, and C-Me distances are 2.156, 1.411, and 1.505 Å, respectively, whereas the average Ru-C, C-C, and C-Me distances are 2.257, 1.426, and 1.501 Å, respectively. The 1:2 phases possess dimer dianions that exhibit ring-ring overlap and intradimer separations (Å) decreasing in the order TCNQ (3.23) > (TCNQ)Cl2 (3.21) > (TCNQ)F4 (3.17). The [TCNQ]2 2- dimer forms mixed-stack linear chains with the organometallic dications, i.e., ...DAADAADAA..., with the molecular planes of the [TCNQ]2 2- dimer parallel to the hexamethylbenzene rings of the cations. The interplanar separations between the hexamethylbenzene ligand and the nearest TCNQ anion are greater than 3.6 A. Extended mixed-stack linear chains are also observed when TCNQ′ = (TCNQ)Cl2 or (TCNQ)F4; however, the [TCNQ′]2 2- dimer is stacked "end on" between the cations with the long molecular axes of the TCNQ anions roughly parallel to the linear-chain axes. Close intermolecular contacts between the cyano nitrogen atoms and the ring carbons of the cation that are significantly less than the sum of the van der Waals radii are observed, suggesting a unique type of donor-acceptor interaction. The compounds with 1:2 stoichiometry have relatively low conductivities (σ300 K < 10-7 Ω-1 cm-1) and diamagnetic, temperature-independent magnetic susceptibilities. In contrast, the 1:4 phases exhibit much higher conductivity (σ300 K = 0.1 Ω-1 cm-1) with temperature dependence indicating semiconducting behavior (EA = 0.06 eV), which is explained in terms of electron localization along extended TCNQ arrays as a result of Coulombic repulsion. The 1:4 phases exhibit temperature-dependent paramagnetic susceptibilities consistent with the random exchange Heisenberg antiferromagnetic exchange (REHAC) model.

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M3 - Article

VL - 26

SP - 4213

EP - 4227

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 25

ER -