Acetylenedicarboxylate as a linker in the engineering of coordination polymers and metal-organic frameworks: challenges and potential

Despite its simplicity as a short and rod-like linear linker, acetylenedicarboxylate (ADC) has for a long time been somewhat overlooked in the engineering of coordination polymers (CPs) and especially in the construction of porous metal-organic frameworks (MOFs). This situation seems to be stemming from the thermosensitivity of the free acid (H(2)ADC) precursor and its dicarboxylate, which makes the synthesis of their CP- and MOF-derivatives, as well as the evacuation of guest molecules from their pores, challenging. However, an increasing number of publications dealing with the synthesis, structural characterization and properties of ADC-based CPs and MOFs, disclose ways to tackle this obstacle. In this regard, using mostly room temperature solution synthesis or mechanochemical synthesis, and very rarely solvothermal synthesis, the ADC linker has successfully been used to form one-, two-, and three-dimensional CPs with metal cations from almost all groups of the periodic table of the elements, whereby its carboxylate groups adopt mainly all types of known coordination modes. ADC-based CPs feature properties, including negative thermal expansion, formation of non-centrosymmetric networks, long-range magnetic ordering, and solid-state polymerization. The first ADC-based microporous MOFs were obtained with Ce(IV), Hf(IV) and Zr(IV), in which the presence of the -C=C- triple-bond within their backbone results in high hydrophilicity, high CO2 adsorption capacity and enthalpy, as well as the uptake of halogen vapors. This discloses the potential of ADC-MOFs for gas storage/separation and water adsorption-based applications. Furthermore, H(2)ADC/ADC was discovered to undergo facile in situ hydrohalogenation to yield halogen-functionalized fumarate-based CPs/MOFs. This review surveys investigations on ADC-based coordination polymers and metal-organic frameworks, and is intended to stimulate interest on this linker in chemists working in the fields of crystal chemistry or materials science

Halide coordinated homoleptic [Fe4S4X4](2-) and heteroleptic [Fe4S4X2Y2](2-) clusters (X, Y = Cl, Br, I)-alternative preparations, structural analogies and spectroscopic properties in solution and solid state

New facile methods to prepare iron sulphur halide clusters [Fe4S4X4](2-) from [Fe(CO)(5)] and elemental sulphur were elaborated. Reactions of ferrous precursors like tetrahalidoferrates(II) or simple ferrous halides with [Fe(CO)(5)] and sulphur turned out to be efficient methods to prepare homoleptic [Fe4S4X4](2-) (X = Cl, Br) and heteroleptic clusters [Fe4S4X4-nYn](2-) (X = Cl, Br; Y = Br, I). Solid materials were obtained as salts of BTMA(+) (= benzyltrimethylammonium); the new compounds containing [Fe4S4Br4](2-) and [Fe4S4X2Y2](2-) (X, Y = Cl, Br, I) were all isostructural to (BTMA)(2)[Fe4S4I4] (monoclinic, Cc) as inferred from synchrotron X-ray powder diffraction. While the solid materials contain defined heteroleptic clusters with a halide X : Y ratio of 2 : 2, dissolving these compounds leads to rapid scrambling of the halide ligands forming mixtures of all five possible [Fe4S4X4-nYn](2-) clusters as could be shown by UHR-ESI MS. The variation of X and Y allowed assignment of the absorption bands in the visible and NIR; the long-wavelength bands around 1100 nm were tentatively assigned to intervalence charge transfer (IVCT) transitions

Eu(O2C-C equivalent to C-CO2): An Eu-II Containing Anhydrous Coordination Polymer with High Stability and Negative Thermal Expansion

Anhydrous Eu-II-acetylenedicarboxylate (EuADC; ADC(2-) = -O2C-C equivalent to C-CO2-) was synthesized by reaction of EuBr2 with K(2)ADC or H(2)ADC in degassed water under oxygen-free conditions. EuADC crystallizes in the SrADC type structure (I4(1)/amd, Z=4) forming a 3D coordination polymer with a diamond-like arrangement of Eu2+ nodes (msw topology including the connecting ADC(2-) linkers). Deep orange coloured EuADC is stable in air and starts decomposing upon heating in an argon atmosphere only at 440 degrees C. Measurements of the magnetic susceptibilities (mu(eff)=7.76 mu(B)) and Eu-151 Mossbauer spectra (delta=-13.25 mm s(-1) at 78 K) confirm the existence of Eu2+ cations. Diffuse reflectance spectra indicate a direct optical band gap of E-g=2.64 eV (470 nm), which is in accordance with the orange colour of the material. Surprisingly, EuADC does not show any photoluminescence under irradiation with UV light of different wavelengths. Similar to SrADC, EuADC exhibits a negative thermal volume expansion below room temperature with a volume expansion coefficient alpha(V)=-9.4(12)x10(-6) K-1

Halide coordinated homoleptic [Fe4S4X4]2- and heteroleptic [Fe4S4X2Y2]2- clusters (X, y = Cl, Br, I) - Alternative preparations, structural analogies and spectroscopic properties in solution and solid state

New facile methods to prepare iron sulphur halide clusters [Fe4S4X4]2- from [Fe(CO)5] and elemental sulphur were elaborated. Reactions of ferrous precursors like tetrahalidoferrates(ii) or simple ferrous halides with [Fe(CO)5] and sulphur turned out to be efficient methods to prepare homoleptic [Fe4S4X4]2- (X = Cl, Br) and heteroleptic clusters [Fe4S4X4-nYn]2- (X = Cl, Br; Y = Br, I). Solid materials were obtained as salts of BTMA+ (= benzyltrimethylammonium); the new compounds containing [Fe4S4Br4]2- and [Fe4S4X2Y2]2- (X, Y = Cl, Br, I) were all isostructural to (BTMA)2[Fe4S4I4] (monoclinic, Cc) as inferred from synchrotron X-ray powder diffraction. While the solid materials contain defined heteroleptic clusters with a halide X : Y ratio of 2 : 2, dissolving these compounds leads to rapid scrambling of the halide ligands forming mixtures of all five possible [Fe4S4X4-nYn]2- clusters as could be shown by UHR-ESI MS. The variation of X and Y allowed assignment of the absorption bands in the visible and NIR; the long-wavelength bands around 1100 nm were tentatively assigned to intervalence charge transfer (IVCT) transitions.Fil: Schüren, Andreas Oskar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universität zu Köln; AlemaniaFil: Gramm, Verena K.. Universität zu Köln; AlemaniaFil: Dürr, Maximilian. Friedrich-Alexander-Universität Erlangen-Nürnberg; AlemaniaFil: Foi, Maria Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Ivanovic Burmazovic, Ivana. Friedrich-Alexander-Universität Erlangen-Nürnberg; AlemaniaFil: Doctorovich, Fabio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Ruschewitz, Uwe. Universität zu Köln; AlemaniaFil: Klein, Axel. Universität zu Köln; Alemani

Structural insight into halide-coordinated [Fe4S4XnY4-n](2-) clusters (X, Y = Cl, Br, I) by XRD and Mossbauer spectroscopy

Iron sulphur halide clusters [Fe4S4Br4](2-) and [Fe4S4X2Y2](2-) (X, Y = Cl, Br, I) were obtained in excellent yields (77 to 78%) and purity from [Fe(CO)(5)], elemental sulphur, I-2 and benzyltrimethylammonium (BTMA(+)) iodide, bromide and chloride. Single crystals of (BTMA)(2)[Fe4S4Br4] (1), (BTMA)(2)[Fe4S4Br2Cl2] (2), (BTMA)(2)[Fe4S4Cl2I2] (3), and (BTMA)(2)[Fe4S4Br2I2] (4) were isostructural to the previously reported (BTMA)(2)[Fe4S4I4] (5) (monoclinic, Cc). Instead of the chloride cubane cluster [Fe4S4Cl4](2-), we found the prismane-shaped cluster (BTMA)(3)[Fe6S6Cl6] (6) (P1). Fe-57 Mossbauer spectroscopy indicates complete delocalisation with Fe2.5+ oxidation states for all iron atoms. Magnetic measurements showed small chi T-M values at 298 K ranging from 1.12 to 1.54 cm(3) K mol(-1), indicating the dominant antiferromagnetic exchange interactions. With decreasing temperature, the chi T-M values decreased to reach a plateau at around 100 K. From about 20 K, the values drop significantly. Fitting the data in the Heisenberg-Dirac-van Vleck (HDvV) as well as the Heisenberg Double Exchange (HDE) formalism confirmed the delocalisation and antiferromagnetic coupling assumed from Mossbauer spectroscopy

Structural insight into halide-coordinated [Fe4_4S4_4Xn_n Y4−n_{4− n}]2−^{2−} clusters (X, Y = Cl, Br, I) by XRD and Mössbauer spectroscopy

Iron sulphur halide clusters [Fe$_4$S$_4$Br$_4$]$^{2−}$ and [Fe$_4$S$_4$X$_2$Y$_2$]$^{2−}$ (X, Y = Cl, Br, I) were obtained in excellent yields (77 to 78%) and purity from [Fe(CO)$_5$], elemental sulphur, I$_2$ and benzyltrimethylammonium (BTMA$^+$) iodide, bromide and chloride. Single crystals of (BTMA)$_2$[Fe$_4$S$_4$Br$_4$] (1), (BTMA)$_2$[Fe$_4$S$_4$Br$_2$Cl$_2$] (2), (BTMA)$_2$[Fe$_4$S$_4$Cl$_2$I$_2$] (3), and (BTMA)$_2$[Fe$_4$S$_4$Br$_2$I$_2$] (4) were isostructural to the previously reported (BTMA)$_2$[Fe$_4$S$_4$I$_4$] (5) (monoclinic, Cc). Instead of the chloride cubane cluster [Fe$_4$S$_4$Cl$_4$]$^{2−}$, we found the prismane-shaped cluster (BTMA)$_3$[Fe$_6$S$_6$Cl$_6$] (6) (P$\bar{1}$). $^{57}$Fe Mössbauer spectroscopy indicates complete delocalisation with Fe$^{2.5+}$ oxidation states for all iron atoms. Magnetic measurements showed small χ$_M$T values at 298 K ranging from 1.12 to 1.54 cm$^3$ K mol$^{−1}$, indicating the dominant antiferromagnetic exchange interactions. With decreasing temperature, the χ$_M$T values decreased to reach a plateau at around 100 K. From about 20 K, the values drop significantly. Fitting the data in the Heisenberg–Dirac–van Vleck (HDvV) as well as the Heisenberg Double Exchange (HDE) formalism confirmed the delocalisation and antiferromagnetic coupling assumed from Mössbauer spectroscopy