An organometallic half-sandwich supramolecular complex {K(18-Crown-6)(ηⁿ-C₆H₅B(C₆H₅)₃)} (n = 1–6) exhibiting a reversible breaking-symmetry phase transition and switchable dielectric behaviour

Abstract

An organometallic supramolecular crystal of {K(18-crown-6)(ηn-C6H5B(C6H5)3)} (n = 1–6) has a half-sandwich structure and exhibits a reversible breaking-symmetry phase transition and switchable dielectric behavior.

Tunable thermotropic phase transition triggering large dielectric response and superionic conduction in lead halide perovskites

“…Typically, in these 3D lead halide perovskites, the Pb 2+ ions are coordinated by six halogen anions to give PbX 6 octahedra, and the organic cations are accommodated in the interstices between PbX 6 octahedrons. Notably, the organic cations are highly flexible, 16 which may have considerable freedom of motion; as a result, the organic cations often undergo order-to-disorder transformations [17][18][19] as induced by temperature, thereby leading lead halide perovskites to undergo structural phase transitions. To date, many 3D, 2D and 1D lead halide perovskites with structural phase transitions have been reported [20][21][22][23][24][25][26] owing to the diversity of organic cations and variability of concomitant structures; more importantly, phase transition along with the simultaneous physical properties of lead halide perovskites are tunable through structure modification, and it is favorable for design of ideal multifunctional materials.…”

Manipulation of Crystal Structures and Properties by the Variation of Halides for Two Organic–Inorganic Hybrids [(C6H15ClNO)2CoX4] (X = Cl or Br)

“…C 11 H 22 Cl 4 MnN 2 obtained from 1-(cyclopentyl)-4-aza-1-azonia-bicyclo[2.2.2]­octane and MnCl 2 is not only a dielectric switch at 170 K but also a luminescent compound with high quantum yield . Diisopropylamine is used to react with HCl, HBr, and HI to obtain DIPAC, DIPAB, and DIPAI, respectively, which have obvious differences not only in T c temperature but also in ferroelectric and/or dielectric properties. − Although more and more switchable dielectric organic–inorganic hybrids have been reported, which show different T c or contrast between high and low dielectric states, − how to manipulate is still a great challenge.…”

A Rotorlike Supramolecular Assembly, {[K(18-crown-6)]PbI3}∞, with a Reversible Breaking-Symmetry Phase Transition near Room Temperature

“…In the LTP, the crystal of 1 belongs to the space group P2 1 /n. As displayed in Figure 1a, its S3), 16,24,25 Each disordered [K(18-crown-6)] + cation, the K1−I1 bond, and the {PbI 3 } ∞ chain look like the rotator, the spinning axis, and the stator in a rotor system, respectively. Thus, 1 is a novel rotorlike supramolecular hybrid.…”

“…Generally, a one-step or multistep phase transition occurs in the crystals with high-symmetry molecule architectures, including the globular shape ClO 4 – , N­(CH 3 ) 4 + , SO 4 2– , SeO 4 2– , and PO 4 2– species, etc., and the highly symmetric molecules or ions, e.g., C­(NH 2 ) 3 + , CH 3 C­(NH 2 ) 2 + , (CH 3 ) 2 NH 2 + , imidazolium, and crown ethers, − because they show a low rotational energy barrier, resulting in easy disorder-to-order orientation transformations. , …”

“…The Pb 2+ ion is bound with six I – ions to build a distorted PbI 6 coordination octahedron, in which the Pb–I lengths fall in 3.1527(13)–3.3598(16) Å, the I–Pb–I cis angles are in 81.42(4)–100.47(4)°, deviating from 90°, and the I–Pb–I trans angles in 176.97(4)–179.79(3)°, being close to 180°, at 293 K. The bond lengths and bond angles in the PbI 6 coordination octahedron of 1 are comparable with those in other iodioplumbates. , Three different I – ions connect to two neighboring Pb 2+ ions in the μ 2 -bridged model, leading Pb 2+ and I – ions to build a straight face-sharing octahedral chain of {PbI 3 } ∞ along the b axis (Figure b). The dynamically disordered 18-crown-6 molecule shows two sets of possible positions with a site occupancy of 0.57/0.43 at 293 K. The K + ion is not only coordinated to the O atoms in the 18-crown-6 molecule to form the [K­(18-crown-6)] + cation (Figure a,c) with normal K–O lengths (Table S3), ,, but also further fastened to the {PbI 3 } ∞ chain via the formation of a K1–I1 bond [K–I = 3.514(4) Å]. Formation of the K1–I1 bond weakens the Pb1–I1 bond, leading to it being slightly longer [3.3598(16) Å] than other Pb–I bonds in the {PbI 3 } ∞ chain.…”