Halogen Bond Effect for Single-Crystal-to-Single-Crystal Transformation: Topochemical Polymerization of Substituted Quinodimethane

Abstract

S Supporting Information ■ INTRODUCTIONTopochemical polymerization is counted as a specific case in the solid-state polymerizations, and it proceeds with no movement of a center of gravity of the monomer molecule and only slight rotation of the monomer molecule around the center of gravity, indicating that the crystallographic position and symmetry of the monomer crystals are retained in the resulting polymer crystals. X-ray single-crystal structure determination of monomer and especially polymer crystals can provide directly an experimental evidence to prove the topochemical polymerization. Such direct proofs are available for the polymerizations of derivatives of diacetylenes, 1 distyrylpyrazines and phenylene diacrylates, 2 trienes and triacetylenes, 3 muconic and sorbic acids, 4 and [2,2′-bi-1H-indene]-1,1′-dione-3,5-diyldialkyl carboxylate. 5 Previously, we investigated photochemical and thermal polymerizations of 7,7,8,8-tetrakis(alkoxycarbonyl)quinodimethanes with various alkoxy groups in the solid state 6 and found that 7,7,8,8-tetrakis(alkoxycarbonyl)quinodimethane monomers with methoxy, chloroethoxy, and bromoethoxy groups afford their highly crystalline polymers (Scheme 1).Unfortunately, photochemical and thermal polymerizations of these quinodimethanes in the solid state did not afford the polymer crystals suitable for single-crystal structure determination. Therefore, on the basis of the indirect experimental evidence such as infrared, elemental analysis, and powder X-ray analysis for the monomers and the corresponding polymers, we concluded that solid-state polymerizations of these monomers might proceed via a topochemical reaction mechanism. On photochemical polymerization in the solid state, UV light is absorbed mainly by the molecules present at the surface of the crystals, and the strength of the UV light is weakened rapidly inside of the crystals. That is, polymerization rate is significantly different between the surface and inside of the crystals. It is therefore considered that the difference in the polymerization rate induces defects or cracks in the crystals, resulting in polymer single crystals with poor quality. Moreover, when the crystals of these quinodimethanes were kept at room temperature in dark for 6 months, their solid-state polymerizations took place slowly, and white polymer crystals, indicating the presence of cracks, were formed. It is considered that it is difficult to obtain their polymer crystals suitable for Xray single-crystal structure analysis on the thermal polymerization. To obtain the polymer crystals suitable for X-ray singlecrystal determination, polymerization reaction is required to proceed rapidly and homogeneously in the crystal. As X-ray, γ-ray, and electron beam have generally excellent penetration ability, solid-state polymerization reactions under their irradiation are expected to take place rapidly and homogeneously and to provide polymer crystals with fewer defects. It is reported that the solid-state polymerizations of diacetylene and diene derivatives ...

Formation of Bundle Assemblies of Stereoregular Polymers in Thermal Solid-State Polymerization of 7,7,8,8-Tetrakis(aryloxycarbonyl)-p-quinodimethanes

“…For the past decades, we investigated thermal and photochemical polymerizations of substituted quinodimethanes and substituted quinone methides in the solid state. We found that 7,7,8,8-tetrakis­(alkoxy­carbonyl)- p -quino­dimethanes with an alkoxy group such as methoxy, 2′-chloro­ethoxy, and 2′-bromo­ethoxy undergo the trans -type topochemical polymerization and cis -specific topochemical alternating copolymerization with 7,7,8,8-tetracyano­quino­dimethane and that the 2-fold helical polymerizations as a novel polymerization mode take place in the thermal solid-state polymerization of 7-cyano-7-(2′-halo­ethoxy­carbonyl)- p -benzo­quinone methides . And also, we proposed a general rule to predict the polymerization reactivity for the topochemical polymerization of substituted quinodimethane monomers in the solid state .…”

“…Recently, topochemical polymerizations impressed us great advantages for preparing attractive shapes and structures such as nanotubes, nanorods, and two-dimensional sheet . However, strict requirements for topochemical polymerizations so far afforded only a limited number of monomers such as diacetylene derivatives, 2,5-distyrylpyridine derivatives, triene and triacetylene derivatives, diene derivatives such as muconic acid and sorbic acid, [2,2′-bi-1 H -indene]-1,1′-dione-3,5-diyl­dialkyl­carboxylate, and substituted quinodimethanes such as 7,7,8,8-tetrakis­(alkoxy­carbonyl)- p -quino­dimethane …”

Phosphine Oxides as Spectroscopic Halogen Bond Descriptors: IR and NMR Correlations with Interatomic Distances and Complexation Energy

“…The formation of halogen bonds can be detected in solids [9][10][11][12][13], in liquids and solutions [14][15][16][17][18] and in gas phase [19][20][21]. Halogen bonding is being actively studied, and it has been demonstrated that it plays a significant role in biochemistry [22,23], in crystal design and design of functional materials (liquid crystals, molecular receptors, conductors, luminescence emitters, non-linear optical materials, etc.)…”

“…Correlation between the normalized distance parameter R = r/(R O + R X ), where r is X···O distance and R O and R X are van der Waals radii of oxygen and halogen atoms, respectively, and the 31 P NMR chemical shift upon complexation, ∆δP, for R-X···O=PMe 3 halogen-bonded complexes studied in this work (X = F, Cl, Br, I, At). The solid line corresponds to Equation(9). R 2 (coefficient of determination) of the fitted curve equals to 0.933.…”

Lighting up solid states using a rubber

“…In recent decades, various solid-state reaction methods have been developed, most of which rely on the principle of topochemical reactions for creating new substances and materials [32][33][34] . The preorganization of the reactants for minimal atom displacement during the breaking and making of bonds is key to topochemistry, and so highly ordered circumstances or systems with complex technical efforts are necessary 35 . On the other hand, in solid-state reactions, the accumulation of byproducts and the irreversibility of reactions are also aggravating effects that prohibit their further use for the design of materials with certain properties 36,37 .…”