TTF–TCNE a charge transfer π–molecular crystal with partial ionic ground state: Optical properties and electron-molecular vibrations interaction

Meneghetti, Moreno; Pecile, Cesare

doi:10.1063/1.471916

Cited by 13 publications

(18 citation statements)

References 33 publications

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“…The a and b polymorphs of [TTF]A C H T U N G T R E N N U N G [TCNE] have been reported previously, [18,19] although we were only successful in isolating pure b-…”

Section: + a C H T U N G T R E N N U N G [Tcne]mentioning

confidence: 65%

“…[18,19] In contrast, the d polymorph possesses a ···ABABABAB··· alternating sequence, whereas the g polymorph possesses parallel segregated ···AAAA··· and ···BBBB··· chains. The specific details and differences are described below.…”

Section: D-[ttf]a C H T U N G T R E N N U N G [Tcne] Polymorphs and mentioning

confidence: 84%

“…Magnetic susceptibilities were measured above 250 K in a 1000 Oe applied field on a Quantum Design MPMS superconducting quantum interference device (SQUID) magnetometer as previously reported. [20] The diamagnetic correction for [18,19] have been reported previously, but we were only successful in isolating pure b-…”

Section: Methodsmentioning

confidence: 94%

“…The ñ CN IR absorptions have been reported previously to occur at 2218 (m), 2200 (s), 2186 (m), and 2177 cm À1 (w). [19] b …”

Section: Methodsmentioning

confidence: 98%

“…[18,19] Likewise, TCNE is reduced to [TCNE]C À . The central CÀC bond is 1.397(3), 1.40(1), 1.41(3), and 1.404(3) , respectively, for the a-, b-, g-, and d-polymorphs.…”

Section: The Nature Of the Ttf And Tcne Moieties: In Each Of The Fourmentioning

confidence: 98%

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Unusually Long, Multicenter, Cation^δ+⋅⋅⋅Anion^δ−Bonding Observed for Several Polymorphs of [TTF][TCNE]

Capdevila‐Cortada

Novoa

Bell

et al. 2011

Chemistry A European J

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The α, β, and δ polymorphs of [TTF][TCNE] (TTF=tetrathiafulvalene; TCNE=tetracyanoethylene) exhibit a new type of long, multicenter bonding between the [TTF](δ+) and [TCNE](δ-) moieties, demonstrating the existence of long, hetero-multicenter bonding with a cationic(δ+)···anionic(δ-) zwitterionic-like structure. These diamagnetic π-[TTF](δ+) [TCNE](δ-) heterodimers exhibit a transfer of about 0.5 e(-) from the TTF to the TCNE fragments, as observed from experimental studies, in accord with theoretical predictions, that is, [TTF(δ+)···TCNE(δ-)] (δ≅0.5). They have several interfragment distances <3.4 Å, and a computed interaction energy of -21.2 kcal mol(-1), which is typical of long, multicenter bonds. The lower stability of [TTF](δ+) [TCNE](δ-) with respect to typical ionic bonds is due, in part, to the partial electron transfer that reduces the electrostatic bonding component. This reduced electrostatic interaction, and the large interfragment dispersion stabilize the long, heterocationic/anionic multicenter interaction, which in [TTF(δ+)···TCNE(δ-)] always involves two electrons, but have ten, eight, and eight bond critical points (bcps) involving C-C, N-S, and sometimes C-S and C-N components for the α, β, and δ polymorphs, respectively. In contrast, γ-[TTF][TCNE] possesses [TTF](2)(2+) and [TCNE](2)(2-) dimers, each with long, homo-multicenter 2e(-)/12c (c=center, 2 C+4 S) [TTF](2)(2+) cationic(+)···cationic(+) bonds, as well as long, homo-multicenter 2e(-)/4c [TCNE](2)(2-) anionic(-)···anionic(-) bonding. The MO diagrams for the α, β, and δ polymorphs have all of the features found for conventional covalent C-C bonds, and for all of the previously studied multicenter long bonds, for example, π-[TTF](2)(2+) and π-[TCNE](2)(2-). The HOMOs for α-, β-, and δ-[TTF][TCNE] have 2c C-S and 3c C-C-C orbital-overlap contributions between the [TTF](δ+-) and [TCNE](δ-) moieties; these are the shortest intra [TTF···TCNE] separations. Thus, from an orbital-overlap perspective, the bonding has 2c and 3c components residing over one S and four C atoms.

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“…The a and b polymorphs of [TTF]A C H T U N G T R E N N U N G [TCNE] have been reported previously, [18,19] although we were only successful in isolating pure b-…”

Section: + a C H T U N G T R E N N U N G [Tcne]mentioning

confidence: 65%

Section: D-[ttf]a C H T U N G T R E N N U N G [Tcne] Polymorphs and mentioning

confidence: 84%

Section: Methodsmentioning

confidence: 94%

“…The ñ CN IR absorptions have been reported previously to occur at 2218 (m), 2200 (s), 2186 (m), and 2177 cm À1 (w). [19] b …”

Section: Methodsmentioning

confidence: 98%

“…[18,19] Likewise, TCNE is reduced to [TCNE]C À . The central CÀC bond is 1.397(3), 1.40(1), 1.41(3), and 1.404(3) , respectively, for the a-, b-, g-, and d-polymorphs.…”

Section: The Nature Of the Ttf And Tcne Moieties: In Each Of The Fourmentioning

confidence: 98%

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Unusually Long, Multicenter, Cation^δ+⋅⋅⋅Anion^δ−Bonding Observed for Several Polymorphs of [TTF][TCNE]

Capdevila‐Cortada

Novoa

Bell

et al. 2011

Chemistry A European J

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Solid‐State ¹³C NMR Evidence for Long Multicenter Intradimer Bonding in Zwitterion‐like Structures

Elliott

Versfeld

Halling

et al. 2019

Chemistry A European J

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The principal values of the 13C chemical shift tensor for the β and δ polymorphs of π‐[TTF⋅⋅⋅TCNE] (TTF=tetrathiafulvalene; TCNE=tetracyanoethylene) have been analyzed to understand the abnormally long intra‐dimer bonding of singlet π‐[TTFδ+⋅⋅⋅TCNEδ−]. These structures possess 12 intradimer contacts <3.40 Å, with the shortest intra π‐[TTF⋅⋅⋅TCNE] separations involving 2‐center (2c) C−S and 3c C−C−C orbital overlap contributions between the [TTF]δ+ and [TCNE]δ−. This solid‐state NMR study compares the [TTF⋅⋅⋅TCNE] 13C tensor data against previously reported π‐[TTF]22+ and π‐[TCNE]22− homo‐dimers to determine how the tensor principal values change as a function of electronic structure for both TTF and TCNE moieties. In the β and δ phases of [TTF⋅⋅⋅TCNE], the TCNE ethylenic 13C shift tensors predict TCNE oxidation states of −0.46 and −0.73, respectively. The TTF sites are less similar to benchmark 13C data with the β‐phase differing primarily in the ethylenic π‐electrons. The δ form differs significantly from the homo‐dimer data at all principal values at both the ethylenic and CH sites, indicating changes to both the π‐electrons and σ‐bonds. In both hetero‐dimer phases, the NMR changes supports long bond formation at nitrile and CH sites not observed in homo‐dimers.

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Structural Studies of the 1:1 Complex of o-3,4-Dimethyltetrathiafulvalene (o-Me2TTF) and 1,2,4,5-Tetracyanobenzene (TCNB)

2010

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TTF–TCNE a charge transfer π–molecular crystal with partial ionic ground state: Optical properties and electron-molecular vibrations interaction

Cited by 13 publications

References 33 publications

Unusually Long, Multicenter, Cation^δ+⋅⋅⋅Anion^δ−Bonding Observed for Several Polymorphs of [TTF][TCNE]

Unusually Long, Multicenter, Cation^δ+⋅⋅⋅Anion^δ−Bonding Observed for Several Polymorphs of [TTF][TCNE]

Solid‐State ¹³C NMR Evidence for Long Multicenter Intradimer Bonding in Zwitterion‐like Structures

Structural Studies of the 1:1 Complex of o-3,4-Dimethyltetrathiafulvalene (o-Me2TTF) and 1,2,4,5-Tetracyanobenzene (TCNB)

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TTF–TCNE a charge transfer π–molecular crystal with partial ionic ground state: Optical properties and electron-molecular vibrations interaction

Cited by 13 publications

References 33 publications

Unusually Long, Multicenter, Cationδ+⋅⋅⋅Anionδ−Bonding Observed for Several Polymorphs of [TTF][TCNE]

Unusually Long, Multicenter, Cationδ+⋅⋅⋅Anionδ−Bonding Observed for Several Polymorphs of [TTF][TCNE]

Solid‐State 13C NMR Evidence for Long Multicenter Intradimer Bonding in Zwitterion‐like Structures

Structural Studies of the 1:1 Complex of o-3,4-Dimethyltetrathiafulvalene (o-Me2TTF) and 1,2,4,5-Tetracyanobenzene (TCNB)

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Product

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Unusually Long, Multicenter, Cation^δ+⋅⋅⋅Anion^δ−Bonding Observed for Several Polymorphs of [TTF][TCNE]

Unusually Long, Multicenter, Cation^δ+⋅⋅⋅Anion^δ−Bonding Observed for Several Polymorphs of [TTF][TCNE]

Solid‐State ¹³C NMR Evidence for Long Multicenter Intradimer Bonding in Zwitterion‐like Structures