Crystal and Electronic Structures of Hydrogen-Bonded 2,5-Diamino-3,6-dihydroxy-<i>p</i>-benzoquinone

Shiny green-colored single crystals of 2,5-diamino-3,6-dihydroxy-p-benzoquinone (1) were prepared from 2,3,5,6-tetrahydroxy-p-phenylenediammonium dichloride. X-ray crystal structural analysis and ab initio calculations revealed that the molecular structure of 1, a highly polarized zwitterionic structure, was similar to that of p-benzoquinone rather than that of p-quinodiimine. Furthermore, a regular π-stack and an intermolecular two-dimensional hydrogen-bonding network were observed within the crystals of 1. The green color in the solid state was attributable to the intermolecular charge-transfer interactions

Crystal and Electronic Structures of Hydrogen-Bonded 2,5-Diamino-3,6-dihydroxy-<i>p</i>-benzoquinone

Shiny green-colored single crystals of 2,5-diamino-3,6-dihydroxy-p-benzoquinone (1) were prepared from 2,3,5,6-tetrahydroxy-p-phenylenediammonium dichloride. X-ray crystal structural analysis and ab initio calculations revealed that the molecular structure of 1, a highly polarized zwitterionic structure, was similar to that of p-benzoquinone rather than that of p-quinodiimine. Furthermore, a regular π-stack and an intermolecular two-dimensional hydrogen-bonding network were observed within the crystals of 1. The green color in the solid state was attributable to the intermolecular charge-transfer interactions

Crystal and Electronic Structures of Hydrogen-Bonded 2,5-Diamino-3,6-dihydroxy-<i>p</i>-benzoquinone

Shiny green-colored single crystals of 2,5-diamino-3,6-dihydroxy-p-benzoquinone (1) were prepared from 2,3,5,6-tetrahydroxy-p-phenylenediammonium dichloride. X-ray crystal structural analysis and ab initio calculations revealed that the molecular structure of 1, a highly polarized zwitterionic structure, was similar to that of p-benzoquinone rather than that of p-quinodiimine. Furthermore, a regular π-stack and an intermolecular two-dimensional hydrogen-bonding network were observed within the crystals of 1. The green color in the solid state was attributable to the intermolecular charge-transfer interactions

Thermal Conductivities and Figures of Merit of Tetracyanoquinodimethane-Based Thermoelectric Materials Consisting of Cations Exhibiting Order–Disorder Transitions

A reduction in thermal conductivity is a common challenge in the development of thermoelectric materials. The thermal conductivity of molecule-based crystals can be reduced by vibrating or disordered counter ions that scatter the heat-transporting phonons. In this work, the thermoelectric properties of five 1:2 salts of tetracyanoquinodimethane (TCNQ) were examined to study the effect of counter ions on the order–disorder transitions in thermal conductivity and on the thermoelectric figure of merit. The tetraethylammonium (TEA+) and dipropylammonium (DPA+) salts of TCNQ0.5–, which undergo the order–disorder transitions above 200 K, exhibited significantly low thermal conductivities compared to the quinolinium (Q+) salt, which does not undergo any order–disorder transition. Methyltriphenylphosphonium (MTPP+) and methyltriphenylarsenium (MTPAs+) salts also showed lower thermal conductivities than the Q+ salt, presumably because of the heavy P and As atoms. Despite the wide variation in thermal conductivities, the product of the phonon velocity v and mean free path l was minimized at similar temperatures, presumably because of the common vibronic property exhibited by the TCNQ0.5– stacks. A comparison between the power factors Pmax and zT revealed the improvement of the conversion efficiency by the vibrating counter cations. The Pmax value for the DPA+ salt was approximately 23 times smaller than that for Q+; however, the thermal conductivity of the DPA+ salt in the disordered phase was approximately a quarter that of Q+, and the zT value for DPA+ remained 7 times smaller than that for Q+

Preparation, Structure, and Redox Behavior of Bis(diarylmethylene)dihydrothiophene and Its π‑Extended Analogues

The preparation, X-ray structure, and optoelectronic properties of bis­(diarylmethylene)­dihydrothiophene <b>1</b> and its π-extended analogues <b>2</b> are described. The development of a simple, short-step synthetic route allowed us to prepare derivatives with different aryl units. X-ray crystallographic analysis of <b>1b</b> and <b>2b</b> revealed their quinoidal structures, which exhibit strong electronic absorption in the visible region. Cyclic voltammetry measurements revealed their strong electron-donating properties. <b>1b</b> showed two-step electrochromic behavior between the corresponding radical cation and dication

Preparation, Structure, and Redox Behavior of Bis(diarylmethylene)dihydrothiophene and Its π‑Extended Analogues

The preparation, X-ray structure, and optoelectronic properties of bis­(diarylmethylene)­dihydrothiophene <b>1</b> and its π-extended analogues <b>2</b> are described. The development of a simple, short-step synthetic route allowed us to prepare derivatives with different aryl units. X-ray crystallographic analysis of <b>1b</b> and <b>2b</b> revealed their quinoidal structures, which exhibit strong electronic absorption in the visible region. Cyclic voltammetry measurements revealed their strong electron-donating properties. <b>1b</b> showed two-step electrochromic behavior between the corresponding radical cation and dication

Hydrophilic and Hydrophobic Channels of Flexible Crystal Lattice: (Guanidinium)₂(Benzene-1,4-disulfonate)·<i>n</i>(XC₆H₅)

The −NH2···[SO3–]– electrostatic hydrogen bonding interaction between guanidinium (G+) and benzene-1,4-disulfonate (BS2–) formed the two-dimensional hydrogen-bonding network linked by benzene pillars, which formed a host–guest crystal with a halobenzene derivative (XC6H5) as a guest. When X = F, the (G+)2(BS2–)·3(FC6H5) crystals were obtained in the same type as the benzene inclusion (G+)2(BS2–)·3(C6H6) crystals. On the contrary, the size of the guest molecule increases for X = Cl and Br, and a hydrophilic channel with nine H2O molecules and a hydrophobic channel with two XC6H5 molecules coexist in (G+)2(BS2–)·2(XC6H5)·9(H2O) crystals. The crystal structure with X = I returned to that of the crystals with FC6H5 as the guest, and the number of guest molecules decreased from three to two. Crystals with hydrophilic channels in a highly symmetric hexagonal lattice appear at X = Cl and Br, which are the boundary region between X = F and I. (G+)2(BS2–)·2(ClC6H5)·9(H2O) crystals changed to guest-free crystals by heat at 373 K, which showed only gate H2O adsorption–desorption behavior at 298 K. The original host–guest crystals were recovered by the vapor diffusion of the ClC6H5–H2O mixture. However, once the crystal is heated to 420 K, it changes to a different host crystal (G+)2(BS2–), where XC6H5 cannot be adsorbed again

Dynamic Motion of Twisted π System-Induced Temperature-Dependent Dielectric Response in the Neat Liquid State

Molecular assemblies of twisted π molecules of tetraphenylene with long alkoxy chains (1) and tetra­[2,3]­thienylene with long alkylamide chains (2) or long alkoxy chains (3) and their dielectric properties were investigated. Different degrees of intermolecular interaction of 1–3 afforded different molecular assemblies, including an ordered columnar structure, disordered columnar, and lamellar structures. The introduction of long alkyl chains enabled us to create thermally stable liquid crystalline or liquid states. Temperature-dependent dielectric measurement revealed that the dynamic flipping motion of the tetra­[2,3]­thienylene core of 3 induced a temperature- and frequency-dependent dielectric anomaly in the neat liquid phase. This flipping motion of the central tetra­[2,3]­thienylene π core occurred relatively easily in the liquid state with a high degree of freedom of molecular motion