Thin Single Crystals of Organic Insulators, Metals, and Superconductors by Confined Electrocrystallization

Abstract

The confined electrocrystallization technique, first described by Thakur et al., involves forcing electrocrystallization to occur within the interface of two opposite substrates. This technique is further demonstrated and extended herein to the synthesis of a variety of thin crystalline films of conducting and insulating molecular materials alike, regardless of their structural dimensionality and shape, form, or habit of the corresponding bulk phases grown independently by standard electrocrystallization in solution. Given that in a confined environment the molecular species will progress much more slowly, or barely at all, to the vicinity of the active electrode, the deposition of neutral π‐donor molecules in the form of a 1 μm thick layer on the surface of a glass slide, by sublimation under vacuum, proved to be a major experimental improvement, and also yielded better crystal quality in more reasonable amounts of time. The effect of temperature and the typically high current densities commonly achieved under these conditions, are discussed along with the experimental conditions used to grow thin crystals of (TMTTF)2ReO4 and (TMTSF)2ReO4, κ‐(BEDT–TTF)2Cu(NCS)2 (25 °C), (BEDT–TTF)Cu2(NCS)3 (60 °C), (EDT–TTF)3[PW12O40]·(CH3CN)· (CH2Cl–CHCl2), β″‐(BEDT–TTF)4·(guest)·[Re6Se6Cl8] and β″‐(BEDT–TTF)4·(guest)·[Mo6Cl14]. It is concluded that the confined electrocrystallization technique appears to be suitable for growing thin crystals of radical ion salts of essentially all the phases previously obtained in bulk crystal form by classical electrocrystallization in solution.

Substituted BEDT‐TTF Derivatives: Synthesis, Chirality, Properties and Potential Applications

“…118 New approaches to electrocrystallisation will also aid the preparation of radical cation salts. 119 Indeed, it can be expected that the charge transfer interactions of the donors and the conductivities of their radical cation salts will find increasing applications now that the important functionalized building blocks are available, and they will play an important role in the development of new multi-functional materials. …”

Nanowires of Molecule-Based Conductors

“…Charge-transfer based conductors (exhibiting a semiconducting behaviour, a metal-like conductivity, or a transition to a superconducting state) are more commonly prepared and studied as macroscopic single crystals (prepared by using slow diffusion in organic solution or electrocrystallisation techniques). Micrometer-sized crystals have nevertheless been obtained (Deluzet et al, 2002;Kobayashi et al, 2008;Mas-Torrent & Hadley, 2005). Chargetransfer conductors at the nanoscale have received broad attention in recent years because of their novel properties and potential applications for future electronic devices.…”

Perspectives on Thin Molecular Organic Films

“…[79±81] Recently, the preparation of thin single crystals by confined electrocrystallization has also been reported. [82] 1604 …”