Isophthalate Groups Research Articles

A Ni(salen)‐Based Metal–Organic Framework: Synthesis, Structure, and Catalytic Performance for CO2 Cycloaddition with Epoxides

A three‐dimensional (3D) chiral metal–organic framework [Cd2{Ni(salen)}(DMF)3]·4DMF·7H2O (1) based on a new enantiopure tetracarboxyl‐functionalized metallosalen Ni(H4salen) {where H6salen is (R,R)‐N,N′‐bis[3‐tert‐butyl‐5‐(3,5‐dicarboxybenzyl)salicylidene]‐1,2‐diphenylethylenediame} was synthesized and characterized by infrared spectroscopy, thermogravimetric analysis, nitrogen and carbon dioxide adsorption, and powder and single‐crystal X‐ray diffractions. In 1, the dinuclear Cd2 cluster [Cd2(COO)4(DMF)3] as a node is cross‐linked by four isophthalate groups on the salen ligands, forming a 2D lamellar structure, which are further linked by Ni(salen) into the 3D network with a 1D open channel (ca. 7.0 × 8.0 Å2) along the a axis. On account of its porosity, Lewis acid sites, and moderate uptake for CO2, 1 can be used as an efficient heterogeneous catalyst for the CO2 cycloaddition with epoxides under relatively mild conditions. Moreover, the bulky epoxide shows a decrease in activity with an increase in the alkyl chain length of the substrate as a result of the confinement effect of 1, showing size‐dependent selectivity.

One-Step Assembly of Visible and Near-Infrared Emitting Metallacrown Dimers Using a Bifunctional Linker.

A family of dimeric LnIII [12-MCGa(III)N(shi) -4] metallacrowns (MCs) (LnIII =Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) was synthesized using the isophthalate group (ip2- ) as a linker. The [LnGa4 ]2 complexes exhibit remarkable photophysical properties, with large molar absorptivities of ≈4×104 m-1 cm-1 , high quantum yields and long luminescence lifetimes with values of (i) 31.2(2)% and 1.410(1) ms, respectively for the visible-emitting [TbGa4 ]2 complex and (ii) 2.43(6)% and 30.5(1) μs for the near-infrared (NIR) emitting [YbGa4 ]2 in the solid state. The NIR emission was obtained not only from Yb, Nd, and Er complexes but also from the less frequently observed emitters such as Pr and Ho. In addition, emission in both visible and NIR domains could be detected for Dy and Sm MCs. ESI-MS and UV/Vis data revealed that the complexes are highly stable in dimethylsulfoxide (DMSO) solution with the 1 H- and COSY-NMR spectra of the diamagnetic [YGa4 ]2 analogue providing evidence for long-term solution stability. This new approach allows one to construct a basis for highly luminescent MCs that may be further modified to be adapted for applications such as optical imaging.

Extended Ensemble Approach to Transferable Potentials for Low-Resolution Coarse-Grained Models of Ionomers.

We develop an extended ensemble method for constructing transferable, low-resolution coarse-grained (CG) models of polyethylene-oxide (PEO)-based ionomer chains with varying composition at multiple temperatures. In particular, we consider ionomer chains consisting of 4 isophthalate groups, which may be neutral or sulfonated, that are linked by 13 PEO repeat units. The CG models represent each isophthalate group with a single CG site and also explicitly represent the diffusing sodium counterions but do not explicitly represent the PEO backbone. We define the extended ensemble as a collection of equilibrium ensembles that are obtained from united atom (UA) simulations at 2 different temperatures for 7 chemically distinct ionomers with varying degrees of sulfonation. We employ a global force-matching method to determine the set of interaction potentials that, when appropriately combined, provide an optimal approximation to the many-body potential of mean force for each system in the extended ensemble. This optimized xn force field employs long-ranged Coulomb potentials with system-specific dielectric constants that systematically decrease with increasing sulfonation and temperature. An empirical exponential model reasonably describes the sensitivity of the dielectric to sulfonation, but we find it more challenging to model the temperature-dependence of the dielectrics. Nevertheless, given appropriate dielectric constants, the transferable xn force field reasonably describes the ion pairing that is observed in the UA simulations as a function of sulfonation and temperature. Remarkably, despite eliminating any explicit description of the PEO backbone, the CG model predicts string-like ion aggregates that appear qualitatively consistent with the ionomer peak observed in X-ray scattering experiments and, moreover, with the temperature dependence of this peak.

Solid state nuclear magnetic resonance investigation of polymer backbone dynamics in poly(ethylene oxide) based lithium and sodium polyether-ester-sulfonate ionomers

Polymer backbone dynamics of single ion conducting poly(ethylene oxide) (PEO)-based ionomer samples with low glass transition temperatures (T(g)) have been investigated using solid-state nuclear magnetic resonance. Experiments detecting (13)C with (1)H decoupling under magic angle spinning (MAS) conditions identified the different components of the polymer backbone (PEO spacer and isophthalate groups) and their relative mobilities for a suite of lithium- and sodium-containing ionomer samples with varying cation contents. Variable temperature (203-373 K) (1)H-(13)C cross-polarization MAS (CP-MAS) experiments also provided qualitative assessment of the differences in the motions of the polymer backbone components as a function of cation content and identity. Each of the main backbone components exhibit distinct motions, following the trends expected for motional characteristics based on earlier Quasi Elastic Neutron Scattering and (1)H spin-lattice relaxation rate measurements. Previous (1)H and (7)Li spin-lattice relaxation measurements focused on both the polymer backbone and cation motion on the nanosecond timescale. The studies presented here assess the slower timescale motion of the polymer backbone allowing for a more comprehensive understanding of the polymer dynamics. The temperature dependences of (13)C linewidths were used to both qualitatively and quantitatively examine the effects of cation content and identity on PEO spacer mobility. Variable contact time (1)H-(13)C CP-MAS experiments were used to further assess the motions of the polymer backbone on the microsecond timescale. The motion of the PEO spacer, reported via the rate of magnetization transfer from (1)H to (13)C nuclei, becomes similar for T≳1.1 T(g) in all ionic samples, indicating that at similar elevated reduced temperatures the motions of the polymer backbones on the microsecond timescale become insensitive to ion interactions. These results present an improved picture, beyond those of previous findings, for the dependence of backbone dynamics on cation density (and here, cation identity as well) in these amorphous PEO-based ionomer systems.

Segmental Dynamics and Ion Association in PEO-Based Single Ion Conductors

We use quasi-elastic neutron scattering (QENS) to characterize polymer dynamics in solid polymer electrolytes (SPEs) that function as single ion conductors. In this case, the SPE combines a PEO spacer with a comonomer that introduces an acid group that serves as the anion. In these single ion conductors (ionomers), only the cation is not covalently bonded to the polymer chain. We study polymer dynamics as a function of ion content, as controlled by varying the ratio of nonionized to ionized comonomers. Even in nonionic polymers (no acid groups), we observe two segmental processes, which we interpret as motion of PEO segments in the spacer midpoint and near the isophthalate groups. In ionized samples, cross-linking between ionic groups considerably slows the dynamics of PEO segments near the isophthalate group. We compare the results to the PEO/LiClO4 system by comparing both polymer dynamics and conductivity as a function of ion content. The optimal ion content for ionomers is half that of the salt system, which we explain based on the differing behavior of polymer dynamics in the two systems.

Designed Synthesis of Multi-Electrochromic Systems Bearing Diaryl Ketone and Isophthalates

New multi-electrochromic systems have been developed through the combination of a diaryl ketyl radical system with isophthalate-based electrochromic materials. The location of the isophthalate group in compounds is very critical to obtaining different colors in the multi-electrochromism.

Synthesis of triazole dendrimers with a dimethyl isophthalate surface group and their application to dye-sensitized solar cells

Dendritic architectures with 1,2,3-triazole as the building unit and dimethyl isophthalate as the surface group are synthesized through a convergent approach employing click chemistry and tested for their application in dye-sensitized solar cells (DSSCs). The studies revealed that the presence of triazole and isophthalate groups in dendritic structures significantly altered the absorption, electrochemical and DSSC behaviors. In DSSCs, the dendritic structures exhibited higher Voc values and higher power conversion efficiency (η) in the I−/I3− redox couple under simulated conditions at 40 mW cm−2.

Molecular Design and Preparation of Bis-isophthalate Electrochromic Systems having Controllable Color and Bistability

New electrochromic systems based on bis-isophthalates were designed and prepared. They showed electrochromism behavior by two-electron reduction. The displayed colors showed greatly enhanced bistability and were dependent on the length of the conjugated bridge between the two isophthalate groups. We believe that the connection of two electrochromic systems with a conjugated bridge is a good basic strategy to obtain new bistable electrochromic systems.

Hydrothermal Synthesis and Crystal Structure of [Mn(phen)‐(m‐phth)]n (phen=1, 10‐phenanthroline, m‐phth=isophthalate)

AbstractHydrothermal reaction of1,2,4‐benzenetricarboxylic acid, and MnCl24H2O with1,10‐phenanthroline gave the title complex, [Mn(phen)(m‐phth)]n, which crystallizes in the monoclinic system, space group P2/c with a= 0.83582(3) nm, b=1.04246(4) nm, c=1.87777(7) nm, β= 100.314(2), V=1.60%8(10) nm3, Z=4, and the final R =0.0576, wR =0.1294. In the complex, each Mn(II) ion is coordinated to four O atoms of carboxylate groups and two N atoms of phen. Isophthalate was generated in situ through the loss of one carboxylate group of1,2,4‐benzenetricarboxylic acid under the hydrothermal condition. Each isophthalate is bound to three manganese atoms through O atom of carboxylate in bridging and chelating fashion, affording manganese(II) pairs that are linked by the isophthalate group to yield a zig‐zag chain along the c‐axis.

Aqua(benzene-1,3-dicarboxylato)zinc(II).

The title compound, poly[[aquazinc(II)]-mu-benzene-1,3-dicarboxylato-O1:O1':O2], [Zn(C8H4O4)(H2O)]n, forms a metal-organic coordination network that consists of tetrahedral Zn atoms bonded to one water molecule and three carboxylate groups. Isophthalate groups bridge the four-coordinate Zn centers to generate two-dimensional architectures in the ac plane. These planar zinc isophthalate motifs are linked by infinite C=O...H-O-H interactions along the a axis to form a chiral framework. The observed polar structural pattern originates due to the distorted tetrahedral Zn centers [O-Zn-O 100.7 (2)-136.0 (1) degrees ] and the alignment of the water molecules. Bridging isophthalate groups align to form approximate centrosymmetric motifs.

Synthesis, crystal structure and magnetic properties of an isophthalate-bridged manganese(II) chain complex

An isophthalate-bridged manganese(II) chain complex of [Mn 2(phen) 4( m-phth)] n [ClO 4] 2 n ·2 nH 2O, where phen is 1,10- phenanthroline and m-phth is isophthalate (dianion of benzene-1,3-dicarboxylic acid), has been prepared and characterized by X-ray crystallography and magnetic measurements. It crystallizes in the triclinic system, space group P 1 ̄ , with a=14.651(1), b=16.679(7), c=13.561(4) Å, α=101.46(3), β=113.91(2), δ=65.52(3)° and Z=2. The structure consists of cationic isophthalate-bridged [Mn 2(phen) 4( m-phth)] 2+ chains, non-coordinated perchlorate anions and crystallized water molecules. Each isophthalate is bound to four manganese atoms through carboxylate oxygens with the syn–syn bridging mode, affording manganese(II) pairs which are linked by the isophthalate group to yield a one-dimensional chain running along the a axis. The intrachain Mn⋯Mn separations are 4.86 and 4.66 Å (through the double carboxylate bridges) and 7.16 Å (the shortest distance through the bridging isophthalate), respectively. The manganese(II) ion displays a distorted octahedral coordination being linked to four nitrogen atoms of two phen ligands and two oxygen atoms of two carboxylate groups from two isophthalate ligands. The variable temperature magnetic susceptibility of the title complex in the temperature range 1.5–300 K has been interpreted in terms of an Mn(II) dimer with a molecular field approximation, the values obtained for J, g(fixed) and z J′ being 3.23 cm −1, 2.00 and −0.35 cm −1, respectively, indicating a weakly ferromagnetic exchange coupling within the Mn(II) dimer with double carboxylates in syn–syn conformation.

Synthesis, crystal structure and magnetic properties of an isophthalate-bridged manganese(II) chain complex

An isophthalate-bridged manganese(II) chain complex of the formula [Mn 2(bipy) 4( m-phth)] n -[ClO 4] 2 n ·4 nH 2O, where bipy is 2,2′-bipyridine and m-phth is isophthalate (dianion of benzene-1,3-dicarboxylic acid), has been prepared and characterized by X-ray crystallography and magnetic measurements. The structure consists of cationic isophthalate-bridged [Mn 2(bipy) 4( m-phth)] 2+ chains, non-coordinated perchlorate anions and water molecules of crystallization. Each isophthalate ligand is bound to four manganese atoms through carboxylase oxygens with the syn-syn bridging mode, affording manganese(II) pairs that are linked by the isophthalate group to yield a one-dimensional chain running along the c-axis. The manganese(II) ion displays a distorted octahedral coordination being linked to four nitrogen atoms of two bipy ligands and two oxygen atoms of two carboxylate groups from two isophthalate ligands. The variable temperature magnetic susceptibility of the title complex in the temperature range 4–300 K has been interpreted in terms of Mn II dimer with a molecular field approximation, and the values obtained for J, g(fixed) and zJ′ being −0.98 cm −1, 2.00 and − 0.03 cm −1, respectively, indicating a weakly antiferromagnetic exchange coupling between the Mn II ions.

Synthesis of polyesters containing an aromatic Triad mesogen

Thermotropic liquid crystalline polymers containing bis( p-oxybenzoyl terephthalate) (Triad) mesogen units linked by flexible polymethylene units were prepared by melt and solution polymerization reactions. Analogous Triad polymers based on a central isophthalate group were also prepared, but these polymers, which contained non-linear rigid segments, did not exhibit liquid crystalline behaviour. Copolymers composed of a mixture of linear and non-linear Triad units were also evaluated. In addition, a series of random Triad copolymers that contained butylene terephthalate (BT) units were also synthesized in solution. The liquid crystalline behaviour of these copolymers depended on the relative number of BT moieties present.