Competition between the C鈥揌路路路N Hydrogen Bond and C鈥揑路路路N Halogen Bond in TCNQFn (n = 0, 2, 4) Salts with Variable Charge Transfer

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• 作者：Julien Lieffrig ; Olivier Jeannin ; Thierry Guizouarn ; Pascale Auban-Senzier ; Marc Fourmigu茅
• 刊名：Crystal Growth & Design
• 出版年：2012
• 出版时间：August 1, 2012
• 年：2012
• 卷：12
• 期：8
• 页码：4248-4257
• 全文大小：593K
• 年卷期：v.12,no.8(August 1, 2012)
• ISSN：1528-7505

文摘

The formation of charge-transfer salts with an iodinated tetrathiafulvalene derivative, EDT-TTF-I (1), has been investigated with a series of TCNQ acceptors of different oxidative strengths, namely, TCNQ, TCNQF, TCNQF₂, and TCNQF₄. These series of compounds have been prepared in order to investigate the effect of the charge in these complexes on the C鈥揑路路路N鈮 halogen bond interactions which can take place between 1 and the various TCNQs. With the most oxidizing TCNQF₄ acceptor, a 1:1 compound formulated as (1)(TCNQF₄) was obtained with a charge 蟻₍₁₎ = +1 on 1, while with TCNQF₂, a 2:1 conducting salt formulated as (1)₂(TCNQF₂) was characterized with 蟻₍₁₎ 鈮?+0.5. With TCNQ itself, both a 1:1 conducting phase, (1)(TCNQ) with 蟻₍₁₎ 鈮?+0.5, and a 2:1 (1)₂(TCNQ) compound with 蟻₍₁₎ = 0 were crystallized. Transport and magnetic properties were rationalized, based on the 蟻₍₁₎ value and band structure calculations. C_TTF鈥揑路路路N鈮 halogen bond interactions were observed in the mixed valence [蟻₍₁₎ = +0.5] salts and even in the neutral [蟻₍₁₎ = 0] compound, while they are surprisingly absent from the full charge transfer TCNQF₄ salt. It is shown that TTF oxidation also activates the TTF sp₂ hydrogen atom located 伪 to the iodine atom, toward the preferential formation of C_TTF鈥揌_伪路路路N鈮 hydrogen bonds, also present in the mixed-valence salts. These series provide an opportunity to evaluate the relative strength of competing C鈥揌路路路N hydrogen and C鈥揑路路路N halogen bonds and their relative sensitivity to charge.