Synthesis of Multisubstituted 1,2,3-Triazoles: Regioselective Formation and Reaction Mechanism.

A synthetically useful approach to functionalized triazoles is described via the reaction of ß-carbonyl phosphonates and azides. 1,4- and 1,5-disubstituted and 1,4,5-trisubstituted triazoles can be regio- and chemoselectively accessed under mild conditions in good to excellent yields (31 examples, up to 99%). A mechanism is proposed that rationalizes the avoidance of the 4-phosphonate byproducts, which is aligned with crystallographic and experimental evidence.

A Linear Two-Coordinate Cr(II) Complex: Synthesis, Characterization, and Reactivity.

The synthesis and characterization of a linear two-coordinate Cr(II) amido complex, Cr{N(t Bu)Dipp}2 (Dipp=2,6-diisopropylphenyl), from the reaction of 1 molar equivalent (equiv) of CrCl2 and 2 equiv. of LiN(t Bu)Dipp is reported. Single-crystal X-ray diffractometry (SC-XRD) analysis revealed that it has a short Cr-N bond distance of 1.8878(9) Å, which could be attributed to the relatively less bulky nature of the amido ligand compared with reported systems. Furthermore, the oxidation reaction of the two-coordinate Cr(II) complex was explored. The oxidation reaction of Cr{N(t Bu)Dipp}2 with the one-electron oxidants AgOTf and [FeCp2 ][BArF 4 ] (BArF 4 - =[B{C6 H3 -3,5-(CF3 )2 }4 ]- ) afforded the trigonal planar three- and bent two-coordinate Cr(III) complexes Cr{N(t Bu)Dipp}2 (OTf) and [Cr{N(t Bu)Dipp}2 ][BArF 4 ], respectively. The reaction of Cr{N(t Bu)Dipp}2 with 1 equiv. of the organic azides AdN3 (Ad=1-adamantyl) and PhN3 afforded the three-coordinate Cr(IV) imido complexes Cr{N(t Bu)Dipp}2 (NAd) and Cr{N(t Bu)Dipp}2 (NPh), respectively. The reaction of Cr{N(t Bu)Dipp}2 and two equiv. of Me3 NO afforded the Cr(VI) dioxo complex Cr{N(t Bu)Dipp}2 (O)2 . The reaction of Cr{N(t Bu)Dipp}2 with 1 equiv. of CyN=C=NCy resulted in the insertion of the carbodiimide into the Cr-N bond, with the formation of a three-coordinate Cr(II) complex. Finally, density functional theory (DFT) calculations were used to elucidate the electronic structure of these complexes.

Mixed-Valence CuI /CuIII Metal-Organic Frameworks with Non-innocent Ligand for Multielectron Transfer.

We report two novel three-dimensional copper-benzoquinoid metal-organic frameworks (MOFs), [Cu4 L3 ]n and [Cu4 L3 ⋅ Cu(iq)3 ]n (LH4 =1,4-dicyano-2,3,5,6-tetrahydroxybenzene, iq=isoquinoline). Spectroscopic techniques and computational studies reveal the unprecedented mixed valency in MOFs, formal Cu(I)/Cu(III). This is the first time that formally Cu(III) species are witnessed in metal-organic extended solids. The coordination between the mixed-valence metal and redox-non-innocent ligand L, which promotes through-bond charge transfer between Cu metal sites, allows better metal-ligand orbital overlap of the d-π conjugation, leading to strong long-range delocalization and semiconducting behavior. Our findings highlight the significance of the unique mixed valency between formal Cu(I) and highly-covalent Cu(III), non-innocent ligand, and pore environments of these bench stable Cu(III)-containing frameworks on multielectron transfer and electrochemical properties.

Ba3.5Cu7.55In1.15Se9: A Wide-Bandgap Copper Indium Selenide Reveals Strong Luminescence and Third-Harmonic Generation.

A new copper indium selenide, Ba3.5Cu7.55In1.15Se9, was synthesized by the KBr flux reaction at 800 °C. The compound crystallizes with orthorhombic Pnma, a = 46.1700(12) Å, b = 4.26710(10) Å, c = 19.8125(5) Å, and Z = 8. The structural framework mainly consists of four sites of cubane-type defective M4Se3 (M = Cu, Cu/In) units with disordered Cu+/In3+ ions present at the part corner of each unit. The single crystal emits intense photoluminescence at 657 nm with a relative quantum yield (RQY) 0.2 times that of rhodamine 6G powder. The compound belongs to a direct band gap at 1.91 eV, analyzed by Tauc's plot, and the energy is close to the PL position. The Hall effect measurement on a pressed pellet reveals an n-type conductivity with a carrier concentration of 3.358 × 1017 cm-3 and a mobility of 24.331 cm2 V-1 s-1. Furthermore, the compound produces a strong nonlinear third-harmonic generation (THG), with an χS(3) value of 1.3 × 105 pm2/V2 comparable to 1.6 × 105 pm2/V2 for AgGaSe2 measured at 800 nm.

Reversible Conversion of Disulfide/Dithiolate Occurring at a Vanadium(IV) Center: A Biomimetic System for Redox Exchange in Vanabin.

Ascidians use a class of cysteine-rich proteins generally referred to as vanabins to reduce vanadium ions, one of the many biological processes that involve the redox conversion between disulfide and dithiolate mediated by transition-metal ions. To further understand the nature of disulfide/dithiolate exchange facilitated by a vanadium center, we report herein a six-coordinate non-oxido VIV complex containing an unbound disulfide moiety, [VIV(PS3″)(PS1″S-S)] (1) (PS3″ = [P(C6H3-3-Me3Si-2-S)3]3-, where PS1″S-S is a disulfide form of PS3″). Complex 1 is obtained from a reaction of previously reported [VV(PS3″)(PS2″SH)] (2) (PS2″SH = [P(C6H3-3-Me3Si-2-SH)(C6H3-3-Me3Si-2-S)2] with TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidin-1-yl)oxyl) via hydrogen atom transfer. Importantly, complex 1 can be reduced by two electrons to form an eight-coordinate VIV complex, [VIV(PS3″)2]2- (4). The reaction can be reversed through a two-electron oxidation process to regenerate complex 1. The redox pathways both proceed through a common intermediate, [V(PS3″)2]- (3), that has been previously reported as a resonance form of VV-dithiolate and a VIV-(thiolate)(thiyl-radical) species. This work demonstrates an unprecedented example of reversible disulfide/dithiolate interconversion mediated by a VIV center, as well as provides insights into understanding the function of VV reductases in vanabins.

Stabilization of a high-spin three-coordinate Fe(iii) imidyl complex by radical delocalization.

High-spin, late transition metal imido complexes have attracted significant interest due to their group transfer reactivity and catalytic C-H activation of organic substrates. Reaction of a new two-coordinate iron complex, Fe{N( t Bu)Dipp}2 (1, Dipp = 2,6-diisopropylphenyl), with mesitylazide (MesN3) afforded a three-coordinate Fe-imidyl complex, Fe{N( t Bu)Dipp}2([double bond, length as m-dash]NMes) (2). X-ray crystallographic characterization of single crystals of 2 showed a long Fe-N distance of 1.761(1) Å. Combined magnetic and spectroscopic (Mössbauer and X-ray absorption near edge structure spectroscopy, XANES) characterization of 2 suggests that it has an S = 2 ground state comprising an S = 5/2 Fe(iii) center antiferromagnetically coupled to an S = 1/2 imidyl ligand. Reaction of 1 and 1-azidoadamantane (AdN3) generated a putative, transient Fe{N( t Bu)Dipp}2([double bond, length as m-dash]NAd) (3') complex that yielded an intramolecular C-H amination product, Fe{N( t Bu)Dipp}{κ2-N,N'-_N(CMe2CH2̲NHAd)Dipp} (3). Quantum mechanical calculations further confirmed the spectroscopic assignment of 2 and 3', as well as the differences in their stability and reactivity. Importantly, imidyl radical delocalization onto the mesityl ring significantly increased the stability of 2 and reduced its reactivity toward potential hydrogen atom transfer (HAT) reagents. In contrast, quantum mechanical calculations of 3' revealed that the radical was solely localized on the imidyl N, leading to a high reactivity toward the proximal C-H bond of the N( t Bu)Dipp- ligand.

A thio-functionalized zinc phosphite with a large-channel framework and enhanced removal ability of mercury ion from aqueous solutions.

The first example of a thio-functionalized zincophosphite material (NTOU-2S) incorporating the 2,5-thiophenedicarboxylate (TPDC) ligands was synthesized using a hydro(solvo)thermal method and structurally characterized by single-crystal X-ray diffraction. Interestingly, the perspective view of the crystal structure for NTOU-2S is similar to our previous report of NTOU-2 but the carboxylate organic ligands (TPDC for NTOU-2S; 1,4-benzenedicarboxylate, BDC, for NTOU-2) in both compounds adopt different types of bis-monodentate coordination models (the unusual cis bonding versus a trans linkage) to bridge the metal atoms of inorganic tubes in the formation of large-channel zincophosphite frameworks, resulting in structural and functional diversities. The thiophene-based compound also displayed higher thermal stability and removal ability for the softer Hg2+ cations from water solutions than the performance of sulfur-free NTOU-2. In addition, the synthesis, structural characteristics, removal properties of heavy metal cations, and thermal and chemical stabilities for both compounds were also reported.

High-temperature, high-pressure hydrothermal synthesis, crystal structure, and infrared and NMR spectroscopy of a barium lead borate with a 2D layer structure: [Ba3Pb(H2O)][B11O19(OH)3].

With a high-temperature, high-pressure hydrothermal technique, a new barium lead borate, [Ba3Pb(H2O)][B11O19(OH)3] (1), has been synthesized and characterized by single-crystal X-ray diffraction, and infrared and solid-state NMR spectroscopy. The structure of 1 contains planar thick layers of borates with the Ba2+ cations at sites in the inter- and intralayer space. Each layer consists of three single sheets. The central sheet is very corrugated and is built up from the fundamental building block (FBB) 2Δ3□:Δ2□-Δ2□. On both sides of the central sheet there are borate single chains formed of the very rare FBB 2Δ4□:Δ2□-3â–¡Δ via corner-sharing. This FBB was first observed in a high-pressure polymorph of CaB2O4. These chains are linked into a sheet by PbO5(H2O) polyhedra, which are further linked to the central sheet by sharing vertices between triangles and tetrahedra to form a thick layer. The IR spectrum shows the presence of hydroxyl groups of HBO4, water molecules, BO3 triangles, and BO4 tetrahedra. The presence of BO3 and BO4 polyhedra was also confirmed by 11B MAS NMR spectroscopy.

High-Temperature, High-Pressure Hydrothermal Synthesis, Crystal Structure, Thermal Stability, and Solid State NMR Spectroscopy of an Aluminum Borate, Ba[AlB4O8(OH)].

A new aluminum borate, Ba[AlB4O8(OH)], has been synthesized under high-temperature, high-pressure hydrothermal conditions at 550 °C and 1400 bar and its structure characterized by single-crystal X-ray diffraction, IR, and MAS 11B, and 27Al NMR spectroscopy. It crystallizes in the monoclinic space group P21/n with a = 7.0695(5) Å, b = 15.108(1) Å, c = 7.0746(5) Å, ß = 93.593(2)°, and Z = 4. Its 2D layer structure is formed of corner-sharing B4O8(OH) clusters and AlO4 tetrahedra with the charge-compensating Ba2+ cations between the layers. While the same in the framework composition, the title compound and the hydrate, Ba[AlB4O8(OH)]·H2O, differ greatly in structure. Although the title compound contains an OH group, it is thermally stable up to 740 °C and then decomposes into Ba2Al2B8O17, as indicated by high-temperature DSC/TG analysis and powder X-ray diffraction.

A Mixed-Valent Uranium Phosphonate Framework Containing U(IV) , U(V) , and U(VI).

It is shown that U(V) O2 (+) ions can reside at U(VI) O2 (2+) lattice sites during mild reduction and crystallization process under solvothermal conditions, yielding a complicated and rare mixed-valent uranium phosphonate compound that simultaneously contains U(IV) , U(V) , and U(VI) . The presence of uranium with three oxidation states was confirmed by various characterization techniques, including X-ray crystallography, X-ray photoelectron, electron paramagnetic resonance, FTIR, UV/Vis-NIR absorption, and synchrotron radiation X-ray absorption spectroscopy, and magnetism measurements.

K2Ca4[(UO2)(Si2O7)2]: A Uranyl Silicate with a One-Dimensional Chain Structure.

A new uranyl silicate, K2Ca4[(UO2)(Si2O7)2], with a 1D chain structure has been synthesized from a solution of mixed alkali- and alkaline-earth-metal cations under hydrothermal conditions at 550 °C and 1400 bar and characterized by single-crystal X-ray diffraction and photoluminescence spectroscopy. It crystallizes in the triclinic space group P1̅ (No. 2) with a = 6.6354(2) Å, b = 6.6791(2) Å, c = 9.6987(3) Å, α = 98.324(2)°, ß = 93.624(2)°, γ = 112.310(2)°, and Z = 1. Its crystal structure consists of a 1D chain of uranyl disilicate formed of corner-sharing UO6 tetragonal bipyramids and Si2O7 double groups. The adjacent chains are separated by K(+) and Ca(2+) cations. It is the first example of uranyl silicate with a 1D chain structure.

High-temperature, high-pressure hydrothermal synthesis, characterization, and structural relationships of layered uranyl arsenates.

Five new uranyl arsenates, Na14[(UO2)5(AsO4)8]·2H2O (1), K6[(UO2)5O5(AsO4)2] (2a), K4[(UO2)3O2(AsO4)2] (2b), Rb4[(UO2)3O2(AsO4)2] (3), and Cs6[(UO2)5O2(AsO4)4] (4), were synthesized by high-temperature, high-pressure hydrothermal reactions at about 560 °C and 1440 bar and were characterized by single-crystal X-ray diffraction, thermogravimetric analysis, and photoluminescence spectroscopy. Crystal data for compound 1: triclinic, P1, a = 7.0005(3) Å, b = 12.1324(4) Å, c = 13.7428(5) Å, α = 64.175(2)°, ß = 89.092(2)°, γ = 85.548(2)°, V = 1047.26(7) Å(3), Z = 1, R1 = 0.0185; compound 2a: monoclinic, P21/c, a = 6.8615(3) Å, b = 24.702(1) Å, c = 7.1269(3) Å, ß = 98.749(2)°, V = 1193.89(9) Å(3), Z = 2, R1 = 0.0225; compound 2b: monoclinic, P21/c, a = 6.7852(3) Å, b = 17.3640(8) Å, c = 7.1151(3) Å, ß = 98.801(3)°, V = 828.42(6) Å(3), Z = 2, R1 = 0.0269; compound 3: monoclinic, P21/m, a = 6.9783(3) Å, b = 17.4513(8) Å, c = 7.0867(3) Å, ß = 90.808(3)°, V = 862.94(7) Å(3), Z = 2, R1 = 0.0269; compound 4: triclinic, P1, a = 7.7628(3) Å, b = 9.3324(4) Å, c = 11.9336(4) Å, α = 75.611(2)°, ß = 73.136(2)°, γ = 86.329(2)°, V = 801.37(5) Å(3), Z = 1, R1 = 0.0336. The five compounds have layer structures consisting of uranyl square, pentagonal, and hexagonal bipyramids as well as AsO4 tetrahedra. Compound 1 contains chains of discrete uranyl square and pentagonal bipyramids, 2a contains three-polyhedron-wide ribbons of edge- and corner-sharing uranyl square and pentagonal bipyramids, 2b and 3 contain dimers of edge-shairing pentagonal bipyramids that share edges with hexagonal bipyramids to form chains, and 4 contains one-polyhedron-wide zigzag chains of edge-sharing uranyl polyhedra. The double sheet structure of 1 is new, but the chain topology has been observed in an organically templated uranyl sulfate. Compound 2b is a new geometrical isomer of the phosphuranylite group. The sheet anion topologies of 2a and 4 can be obtained by splitting the ß-U3O8-type sheet into complex chains and connecting the chains by arsenates.

High-temperature, high-pressure hydrothermal synthesis and characterization of an open-framework uranyl silicate with nine-ring channels: Cs2UO2Si10O22.

A new uranium(VI) silicate, Cs(2)UO(2)Si(10)O(22), has been synthesized by a high-temperature, high-pressure hydrothermal method and characterized by single-crystal X-ray diffraction, luminescence, and solid state NMR spectroscopy. It crystallizes in the monoclinic space group P2(1)/c (No. 14) with a = 12.2506(4) Å, b = 8.0518(3) Å, c = 23.3796(8) Å, ß = 90.011(2)°, and Z = 4. Its structure consists of silicate double layers in the ab plane which are connected by UO(6) tetragonal bipyramids via four equatorial oxygen atoms to form a 3D framework with nine-ring channels parallel to the b axis where the Cs(+) cations are located. The photoluminescence emission spectrum at room temperature consists of one broad structured band which is typical of uranyl. The (29)Si MAS NMR spectrum is consistent with the crystal structure as determined from X-ray diffraction, and the resonances in the spectrum are assigned. A comparison of related uranyl silicate structures is made.

Cs2USi6O15: a tetravalent uranium silicate.

A uranium(IV) silicate has been synthesized under high-temperature, high-pressure hydrothermal conditions. The structure consists of unbranched dreier single layers with the composition [Si(2)O(5)] that are connected by UO(6) octahedra to form a 3D framework with 7-ring channels where the Cs(+) cations are located. Each UO(6) octahedron spans four neighboring dreier single chains and, therefore, introduces a high degree of corrugation in the silicate layers. The U 4f X-ray photoelectron spectroscopy spectrum was measured to confirm the valence state of the uranium. A comparison of related metal silicate structures is made. After the synthesis of this compound, all members in the family of uranium silicates and germanates with oxidation states of uranium from 4+ to 6+ have been observed.

Cs8U(IV)(U(VI)O2)3(Ge3O9)3·3H2O: a mixed-valence uranium germanate with 9-ring channels.

A mixed-valence uranium(IV,VI) germanate has been synthesized under high-temperature, high-pressure hydrothermal conditions. The structure contains discrete U(IV)O(6) octahedra and U(VI)O(6) tetragonal bipyramids, which are connected by three-membered single-ring Ge(3)O(9)(6-) anions to form a three-dimensional framework with 9-ring channels. The U 4f X-ray photoelectron spectroscopy spectrum was measured to identify the valence states of the uranium.

Poly[(µ(6)-benzene-1,3,5-tricarboxyl-ato-κO:O:O:O:O:O)tris-(N,N-dimethyl-formamide-κO)tris-(µ(3)-formato-κO:O')trimagnesium(II)].

The title complex, [Mg(3)(CHO(2))(3)(C(9)H(3)O(6))(C(3)H(7)NO)(3)](n), exhib-its a two-dimensional structure parallel to (001), which is built up from the Mg(II) atoms and bridging carboxyl-ate ligands (3 symmetry). The Mg(II) atom is six-coordinated by one O atom from a dimethyl-formamide mol-ecule, two O atoms from two µ(6)-benzene-1,3,5-tricarboxyl-ate ligands and three O atoms from three µ(3)-formate ligands in a distorted octa-hedral geometry.

Poly[diaqua-µ(4)-biphenyl-4,4'-dicarboxyl-ato-magnesium(II)].

The solvothermal reaction of magnesium nitrate with bi-phenyl-4,4'-dicarboxylic acid in N,N-dimethyl-formamide and water leads to the formation of crystals of the title complex, [Mg(C(14)H(8)O(4))(H(2)O)(2)](n). In the crystal structure, the Mg cations are coordinated by six O atoms from two water mol-ecules and four symmetry-related biphenyl-4,4'-dicarboxyl-ate anions within slightly distorted octa-hedra. The Mg cations are located on a center of inversion, the biphenyl-4,4'-dicarboxyl-ate anions around a twofold rotation axis and the water mol-ecule in a general position. The Mg cations are linked by the anions into a three-dimensional framework.