Reversible Luminescence Vapochromism and Crystal-to-Amorphous-to-Crystal Transformations of Pseudopolymorphic Cu(I) Coordination Polymers

Abstract

Four solvent-responsive one-dimensional copper(I) coordination polymers (CPs), namely, {[Cu 4 I 4 L(MeCN) 2 ]·CH 2 Cl 2 } n (1), {[Cu 4 I 4 L(MeCN) 2 ]·CHCl 3 } n (2), {[Cu 4 I 4 L(MeCN) 2 ]·0.5p-xylene} n (3), and [Cu 4 I 4 L(MeCN) 2 ] n (4), were prepared by reaction of CuI with N,N′-bis[2-(cyclohexylthio)ethyl]pyromellitic diimide (L) via self-assembly under varying solvent conditions. CPs 1−4, which are pseudopolymorphic supramolecular isomers derived from solvent molecules, are composed of Cu 4 I 4 cubane clusters. The ligands in CPs 1−3 adopted a synconformation, whereas in CP 4 they were observed in the anticonformation. This occurred via syn to anti transitions upon heating, followed by exposure to MeCN vapor. In addition, a reversible anti to syn transition was achieved by agitating in mixed organic solvents. It was shown that ligand transition from the syn-to the anti-conformation occurred through crystal-to-amorphous-to-crystal transformations. Furthermore, CPs 1−3 exhibited reversible solvent exchange and crystal transformation by exposure to vapors from volatile organic compounds.C oordination polymers (CPs) have recently received a great amount of attention, with studies focusing on the control of geometric structures of compounds formed by coordination between well-designed ligands and metal cations. Furthermore, the production of compounds exhibiting useful functionalities has also been investigated. CPs have the potential for use in various fields, such as catalysis, 1−3 ion exchange, 4,5 selective adsorption, 6−8 hydrogen storage, 9,10 sensors, 11,12 and magnetism-based applications. 13,14 Moreover, a number of studies are currently underway regarding the crystal transformation of CPs by control of anionic, solvent, ligand, and metal cationic molar ratios. Predicting such structural changes is not easy; hence, many chemists have invested effort in identifying and controlling the influences of the factors that induce structural changes. Our aim was to focus on reversible/nonreversible structural transformations in copper(I) CPs by variation of temperature and solvent. Furthermore, we wished to investigate their emission changes under the above conditions. We expect that a number of structural transformations will be related to conformational changes of the sulfur-containing organic ligands and the labile Cu−S coordination bond. 15−17 We investigated the preparation of four CPs by reaction of CuI with a dithioether ligand bearing a pyromellitic diimide spacer. We found that by varying the ligand to metal ratio, complexes with different structures were formed, including rhomboid dimers and stair-step polymers. Although acetonitrile and dichloromethane were used as solvents and structural transformations were induced by controlling the ligand/metal ratio, some reversible crystal transformations were also observed. 15 We later reported the preparation of four CPs containing Cu 2 I 2 clusters by reaction of CuI with a ligand bearing both pyrazine and sulfur moieties. In addition, we reported a contr...

Crystal structure of 2,6-dibenzylpyrrolo[3,4-f]isoindole-1,3,5,7(2H,6H)-tetrathione

“…We have reported copper(I) coordination polymers based on pyromellitic diimide derivatives (Park et al, 2011), which showed colour change owing to intermolecular halogen-interactions. In addition, we have found that reversible solvent exchange and crystal transformations were possible in the crystals (Kang et al, 2015). In an extension of previous research, we have synthesized the pyromellitic diimide in which the O atoms are replaced with S atoms, by the reaction of N,N 0 -dibenzylpyromellitic diimide with Lawesson's reagent, and report its crystal structure here.…”

Crystal structure ofN-[2-(cyclohexylsulfanyl)ethyl]quinolinic acid imide

“…evaporated to give a crude solid. The reaction mixture was then concentrated and purified by chromatography on silica gel (MeCOOEt/n-C 6 H 14 = 30/70 v/v, R F = 0.28) (Kang et al, 2015). Colourless plates were obtained by slow evaporation of a hexane solution of the title compound.…”

Reversible Specific Vapoluminescence Behavior in Pure Organic Crystals through Hydrogen‐Bonding Docking Strategy

“…This is mainly because the intermolecular interactions (e. g., weak M–M interactions, metallophilic interactions, π‐stacking, and coordination modes) in transition‐metal assemblies can easily be perturbed with uptaking certain vapors into the crystal lattice, thereby inducing dramatic changes in emission color . Moreover, relevant researches evidenced that isomer conversion of metal‐complexes with remarkable emission color change can also be controlled through exposure to different vapor, which rendered a new approach to access great vapoluminescent materials . Still and all, the metal‐containing vapoluminescent compounds are generally expensive, difficult to synthesis, and environmentally unfriendly, thus limits their practical application.…”