Crystal Structures and Physical Properties of (M⁺)(Crown Ethers)_x(TCNQ)_y Salts with M⁺ = Li⁺, Na⁺, K⁺, Rb⁺, and Cs⁺

Abstract

Highly designable M+(crown ether) x supramolecular cations were introduced into electrically conducting anion radical salts of 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) as counter cations. Alkali metal cations of M+ = Li+, Na+, K+, Rb+, and Cs+ were combined with crown ethers of [12]­crown-4, [15]­crown-5, and [18]­crown-6, forming 18 types of single crystals of M+(crown ether) x (TCNQ) y (x = 1 or 2 and y = 2, 1.5, 2.5 or 3). Single-crystal X-ray structural analyses of all of the compounds revealed a variation in the supramolecular cation of M+(crown ether) x and the TCNQ arrangements. A smaller size of Li+ than the [18]­crown-6 cavity formed a dynamic cation environment, whereas the size-compatible K+([18]­crown-6) supramolecule exhibited a planar disc-shaped structure. When the size of M+ was larger than the crown ether cavity, sandwich-type M+(crown ether)2 and cone-type M+(crown ether) structures were observed in the TCNQ salts. K+([12]­crown-4)2 and Cs+([15]­crown-5) structures are typical examples of sandwich- and cone-type supramolecules, respectively. Both cation structures were observed in K+([12]­crown-4) x and Rb+([12]­crown-4) x with x = 1 and 2, and the cone-type structures were also confirmed in M+([15]­crown-5) for M+ = Rb+ and Cs+. Depending on the type of the supramolecular cation, the π-stacking arrangements of TCNQs changed from 1D dimer to 1D dimer + monomer, 1D trimer, 1D trimer, 2D dimer, 2D tetramer, 2D spanning-overlap, and 1D trimer + monomer arrangements. The systematic study of all of the combinations of alkali metal ions and crown ethers enables the formation of various types of intermolecular interactions, electrical conductivity, phase transition, and magnetic properties. Among all of the crystals, the sandwich-type M+([12]­crown-4)2 with M+ = Na+, K+, and K+([15]­crown-5)2 supramolecules demonstrated a thermally activated rotation of crown ethers in the high-temperature phase, whereas the motional freedom of Li+ and Na+ in [15]­crown-5 or [18]­crown-6 coupled to the phase transition behavior and dielectric response in the TCNQ salts.

Coordination Chemistry and Spectroscopic Properties of Eu(II), Sm(II), and Yb(II) with 12-Crown-4

“…The Yb 2+ metal center is fully encapsulated by two tetradentate 12c4 molecules, without any coordinating solvent molecules (see Figure ). This is a rather commonly observed motif for homoleptic 12-crown-4 sandwiches with alkali, , select alkaline earth, , divalent transition metals and Ag + , , as well as p-block metals such as Ge 2+ , Sn 2+ , In 3+ , and Tl + all forming [M­(12c4) 2 ] m + ( m = 1, 2, 3) cations with various outer-sphere anions . Despite the common cation assembly, the asymmetric unit of this structure contains two [Yb­(12c4) 2 ] 2+ and four [Ph 4 B] − ions, which are all crystallographically distinct.…”

Direct Extraction of Sodium Hydroxide by Calix[4]pyrrole-Based Ion-Pair Receptors

“…Previous research with crown ethers led to an appreciation that the stability of Na + in appropriately designed sandwich complexes is greater than in the corresponding monomeric complex due to the approximately twofold increase in ion–dipole interactions. , We thus envisioned that the conjugation of a calix[4]­pyrrole core with two benzo-12-crown-4 subunits, which are known to form sandwich complexes with the Na + ion, − would allow us to create an ion pair receptor capable of recognizing and extracting NaOH. The calix[4]­pyrrole-based ion pair receptors cis / trans - 1 and cis / trans - 2 (Figure ) were designed to test this hypothesis.…”

Tetranitro- and tetraamino-dibenzo[18]crown-6-ether derivatives: complexes for alkali metal ions, redox potentials, crystal structures, molecular sorption, and proton conducting behaviours

“…14,15,38,39 For instance, the ionic channel of [ (Li + ) x ( [18]crown-6)] ∞ and [(Na + ) x ([18]crown-6)] ∞ have been introduced into the electrically conductive [Ni(dmit) 2 ] (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate) and TCNQ salts as a countercation structure to compensate the total charge valance of the crystals. 14,15,[40][41][42] The motional freedom of Li + and Na + in the ionic channels influenced the freedom of conduction electrons on the π-stacking column of [Ni(dmit) 2 ]. 14,15 The coexistence of two different dynamics for the M + and electron can produce hybrid ion-electron transport materials, which can be utilized for the feature electronic device and the electrode materials of the secondary battery.…”

“…The coupling between the dynamics of M + (inside the cavity of the crown ether) and the electronic properties has been reported in the phase transition and dielectric behaviors of M + (crown ether)(TCNQ) x crystals. [40][41][42] The coexistence of a dynamic M + environment and redox active structural unit is one possible approach to design the outer stimuli responsible for multifunctional molecular materials. [56][57][58] Simple redox-active crown ethers of tetranitoro-dibenzo[18] crown-6 (1) and tetraamino-dibenzo [18]crown-6 (2) become electron-accepting and electron-donating molecules (Scheme 1), respectively; these have already been reported as reaction intermediates.…”

“…The coupling between the dynamics of M + (inside the cavity of the crown ether) and the electronic properties has been reported in the phase transition and dielectric behaviors of M + (crown ether)(TCNQ) x crystals. 40–42 The coexistence of a dynamic M + environment and redox active structural unit is one possible approach to design the outer stimuli responsible for multifunctional molecular materials. 56–58…”