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The complex metal oxide SrCo0.5Ru0.5O3-δ possesses a slightly distorted perovskite crystal structure. Its insulating nature infers a well-defined charge distribution, and the six-fold coordinated transition metals have the oxidation states +5 for ruthenium and +3 for cobalt as observed by X-ray spectroscopy. We have discovered that Co3+ ion is purely high-spin at room temperature, which is unique for a Co3+ in an octahedral oxygen surrounding. We attribute this to the crystal field interaction being weaker than the Hund's-rule exchange due to a relatively large mean Co-O distances of 1.98(2) Å, as obtained by EXAFS and X-ray diffraction experiments. A gradual high-to-low spin state transition is completed by applying high hydrostatic pressure of up to 40 GPa. Across this spin state transition, the Co Kβ emission spectra can be fully explained by a weighted sum of the high-spin and low-spin spectra. Thereby is the much debated intermediate spin state of Co3+ absent in this material. These results allow us to draw an energy diagram depicting relative stabilities of the high-, intermediate-, and low-spin states as functions of the metal-oxygen bond length for a Co3+ ion in an octahedral coordination. [ABSTRACT FROM AUTHOR]

Two new two-dimensional (2D) heterometal coordination polymers [Cu2M(tzdc)2(H2O)2]∙2H2O [M = Fe2+ (1) or Mn2+ (2); tzdc3- = 1,2,3-triazole-4,5-dicarboxylate] were assembled by using the tzdc3-, Cu2+, and Fe2+/Mn2+ ions. Single-crystal X-ray analysis reveals that the two compounds consist of mixed-spin microporous Kagomé layers, which are packed into three-dimensional structures by hydrogen bonding and interlayer weak Cu⋯O interactions. When heated, they can release in a stepwise manner the uncoordinated and coordinated water molecules to produce dehydrated phases (1′ and 2′), respectively, which are stable up to ~300 °C. The structures of 1′ and 2′ were determined by powder X-ray diffraction analysis, which reveals a change in the coordination sphere of Fe2+/Mn2+ ions from an octahedron to an elongated 4+2 form, and a microporous-to-nonporous structural transformation involving intralayer wrinkling and interlayer superimposition. When the dehydrated samples are exposed to air, they can return to the hydrated phases quickly by adsorption of water molecules. Accordingly, a reversible change in magnetism between the ferrimagnetic character of the hydrated samples and the suppressed ferrimagnetic character of the dehydrated samples was found in this reversible dehydration and rehydration. These facts indicate these 2D heterometal coordination polymers are unique flexible 2D dynamic magnetic materials. [ABSTRACT FROM AUTHOR]

In organic field-effect transistors (OFETs), the quality of charge-transport pathway, controlled by crystal structures of organic semiconductors (OSCs), strongly affects the performance of the device. To achieve higher charge mobility, solution-processed single-crystal (SPSC) techniques have been used to decrease crystal defects by aligning the crystals of OSCs in the in-plane direction. Nonetheless, through SPSC techniques, whether the crystalline lattices are well-aligned in the out-of-plane direction and how the out-of-plane lattice misorientaion affects OFET performances remain unclear. Here, a characterization protocol based on polarized optical microscope, X-ray diffraction, and electron diffraction is established to identify the lattice structure, the in-plane and out-of-plane lattice alignment in the crystal array of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-PEN). Regardless of the solvents used in the PDMS-assisted crystallization, the characterization protocol confirms that all the crystal arrays share the same lattice structure (form I phase), and have similar in-plane lattice alignment. However, TIPS-PEN molecules have sufficient time to unify their out-of-plane orientation and prevent the formation of low angle grain boundary (LAGB) during crystal growth if high boiling temperature solvents are used. The improved out-of-plane lattice alignment increases the hole mobility and decreases the performance fluctuations of devices. The results confirm that the out-of-plane lattice alignment significantly impacts the performance of the devices and the reproducibility of the solution-processed TIPS-PEN OFETs. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of Cu(NO3)2 and 2-isopropylimidazole (Hipim) in different solvents/templates gave three supramolecular isomers: α-[Cu(ipim)] (1), β-[Cu(ipim)] (2), and γ-[Cu(ipim)]·1/3C6H6 (3). Single-crystal X-ray diffraction analyses showed that 1, 2, and 3 are parallel-packed wavy chains, triple-stranded helices, and cubic-orthogonal-packed helical chains consisting of alternatively interconnected two-coordinated Cu(I) ions and ipim- ligands. Because of the different intermolecular interactions, 1, 2, and 3 show different phosphorescence properties with emission maxima at 555, 540, and 530 nm, respectively. More interestingly, [Cu(ipim)] can melt at high temperature without decomposition. Compounds 1 and 2 melt above 185 and 146 °C, respectively; this liquid solidifies below 117 °C to form 1 again. However, 3 loses the benzene guest molecules above 90 °C and transforms to 1 in a crystal-to-crystal manner. [ABSTRACT FROM AUTHOR]

Using a bis-triazolate ligand and tetrahedral Zn(II) ion, we synthesized a flexible porous coordination polymer functionalized with pairs of uncoordinated triazolate N-donors that can be used as guest chelating sites to give very high CO2 adsorption enthalpy and CO2/N2 selectivity. The dynamic CO2 sorption behavior could be monitored well by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

The reaction of commercially available 3-animo-1,2,4-triazole (Hatz) and Zn(OH)2 at room temperature produced a porous zeolite-like metal azolate framework, [Zn(atz)2] (MAF-66). Single-crystal X-ray diffraction studies of MAF-66 showed that atz- served as an imidazolate-type ligand, linking tetrahedral ZnII ions to form a noninterpenetrated dia framework, which contains a narrow, three-dimensional intersecting channel system (void = 49.8%) functionalized by amino groups and uncoordinated triazolate N atoms on the pore surface. Gas-sorption measurements of MAF-66 revealed high CO2 uptakes (27.6/19.4 wt % at 273/298 K and 1 atm) and high Henry's law CO2/N2 selectivity (403/225 at 273/298 K). The host-guest interactions between CO2 and the pore surface were also studied by in situ IR absorption spectroscopy and powder X-ray diffraction measurements. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of metal salts, benzenedicarboxylic acids, and 4,4′-azopyridine (azpy) in different conditions produced four coordination polymers, namely, [Zn3(bdc)3(bphy)3]·2DMF·10H2O (3; H2bdc = 1,4-benzenedicarboxylic acid, bphy = 1,2-bis(4-pyridyl)hydrazine, and DMF = N,N-dimethylformamide), [Ni(bdc)(bphy)]·DMF·3.5H2O (4), [Zn(nipa)(bphy)]·EtOH (5; H2nipa = 5-nitroisophthalic acid), and [CoBr(bdc)0.5(bphy)]·2DMA·H2O (6; DMA = N,N-dimethylacetamide), in which the azpy ligand was in situ reduced. Structural determination reveals that 3-5 consist of the same metal/ligand ratio and similar coordination modes, as well as similar two-dimensional square-grid networks, but differ from their packing/interpenetration modes. 3 consists of alternately arranged single layers and interweaved double layers. Single layers in 4 directly stack in an offset fashion, while 5 is constructed of interdigitated double layers. 6 is a one-dimensional ladderlike structure, which could be regarded as that half of the bridging benzenedicarboxylate ligands in 3-5 are replaced by monodentate bromide ions. Interestingly, the crystal structures of these low-dimensional coordination polymers contain considerable solvent-accessible voids. Thermogravimetric curves, powder X-ray diffraction, and gas sorption experiments were used to study the potential porosity of these structures, which indicated that they can all reversibly desorb and adsorb solvent molecules. In particular, 4 showed gated sorption behavior and high CO2/CH4 selectivity because of its flexible structure. [ABSTRACT FROM AUTHOR]

Self-assembly of silver(I) ion with 3-alkyl-1,2,4-triazoles in different solvents yielded four new metal azolate frameworks (MAFs), namely, [Ag(mtz)] (1, Hmtz = 3-methyl-1,2,4-triazole), [Ag(etz)] (2, Hetz = 3-ethyl-1,2,4-triazole), [Ag4(etz)4]·H2O (3·H2O), and [Ag4(ptz)4] (4, Hptz = 3-propyl-1,2,4-triazole). Single-crystal X-ray diffraction revealed that Ag(I) ions and triazolates in these MAFs are all three-coordinated to give rare 3-connected framework topologies. Although 1and 2possess the same uniform (10,3)-d (utp) topology, variation of the alkyl groups renders substantially different coordination structures. On the other hand, 3·H2O and 4, also bearing different alkyl substituents, are isomorphours, and can be simplified as the same uninodal sqc5603 topology (point and vertex symbols are 82.10 and 8.82.12, respectively). Due to the relatively short alkyl length, the coordination framework of 3·H2O contains one-dimensional narrow channels. According to thermogravimetry and single-crystal X-ray diffraction, 3·H2O can be dehydrated without framework collapse. Although guest-free 3does not adsorb N2at 77 K, 3·H2O can undergo guest exchange, and 3can adsorb solvent vapor, to give CH2Cl2- and CH3CN-included crystals. Comparing the single-crystal structures of 3·H2O, 3, 3·CH2Cl2, and 3·CH3CN reveals the framework flexibility of 3. These materials also show interesting structure- and guest-dependent photoluminescent properties. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of equimolar zinc acetate, lithium acetate, and 1,3,5-benzenelricarboxylic acid (H3btc) in different mixed solvents yielded isostnictural three-dimensional frameworks [UZn(btc)()) - IG leG and IG denote coordinated and lattice guests, respectively; cG=(nmp)0.5(H2O)0.5, IG=(EtOH)0.5 (1a); cG=H2O, IG= EtOH (1b); nmp=N-methyl-2-pyrrolidone] with one-dimensional channels occupied by guest molecules and solvent-coordinated, extrusive Li+ ions. Thermogravimetry analyses and powder X-ray diffraction measurements revealed that both la and lb can lose all lattice and coordinated guests to torn', a desolvaled phase [LiZn(btc)] (MCF-27, 1) and almost retains the original framework structure. Gas adsorption measurements on 1 confirmed its permanent porosity but suggested a structural transformation horn 1a/1b 101.11 is noteworthy that only la can undergo a single-ctystal 10 single-crystal (SCSC) transformation into 1 upon desolvation. The crystal structure of 1 revealed that Ihe Li+ ions were retracted into the channel walls via complementary coordination to the carboxylate oxygen atoms in the framework rather than being exposed on the pore surface. Single-crystal X-ray diffraction analyses were also performed for N2- and CO2-loaded samples of 1, revealing that the framework remained unchanged when the gases were adsorbed. Although the gas molecules could not be modeled, the residue electrons inside the channels demonstrated that the retracted Li+ ions still behave as the primary interacting site for CO2 molecules. Nevertheless, solvent molecules such as H2O can readily compete with the framework oxygen atom to retrieve the extrusive Li+ ions, accompanying the reverse structural transformation, i.e., from 1 to 1a/1b. [ABSTRACT FROM AUTHOR]

The anionic syn-/anti-[Fe(μ-SEt)(NO)2]2- (2a) were synthesized and characterized by IR, UV-vis, EPR, and X-ray diffraction. The geometry of the [Fe(μ-S)2Fe] core is rearranged in going from [{Fe(NO)2}9-{Fe(NO)2}9J Roussin's red ester [Fe(μ-SEt)(NO)2]2 (la) (Feߪ Fe distance of 2.7080(5) Å) to the [{Fe(NO)2}9-{Fe(NO)2}10] complex 2a (Fe ߪ Fe distance of 2.8413(6) Å) to minimize the degree of Fe ߪ Fe interaction to stabilize complex 2a. On the basis of X-ray absorption (Fe K- and L-edge), EPR and SQUID, complex 2a is best described as the anionic [{Fe(NO)2}9-{Fe(NO)2}10] Roussin's red ester with the fully delocalized mixed-valence core. The complete bridged- thiolate cleavage yielded DNIC [(EtS)2Fe(NO)2]- (3a) in the reaction of 2 equiv of [EtS]- and complex 1a, whereas reaction of 2 equiv of [tBuS]- with [Fe(μ-StBu)(NO)2]2 (1b) gave DNIC [(tBuS)2Fe(NO)2]- (3b) and the anionic Roussin's red ester [Fe(μ-StBu)(NO)2]2- (2b) through bridged-thiolate cleavage in combination with reduction. In contrast to the inertness of DNIC 3b toward complex 1b, nucleophile DNIC 3a induces the reduction of complex la to produce the anionic Roussin's red ester 2a. Interestingly, dissolution of complex 3a in MeOH at 298 K finally led to the formation of a mixture of complexes 2a and 3a, in contrast to the dynamic equilibrium of complexes 3b and lb observed in dissolution of complex 3b in MeOH. These results illustrate the aspect of how the steric structures of nucleophiles ([EtS]- vs [tBuS]- and [(EtS)2Fe(NO)2]- vs [(tBuS)2Fe(NO)2]-) function to determine the reaction products. [ABSTRACT FROM AUTHOR]

The neutral trinuclear iron-thiolate-nitrosyl, [(ON)Fe(μ-S,S-C6H4)]3 (1), and its oxidation product, [(ON)Fe(μ-S,S-C6H4)]3[PF6] (2), were synthesized and characterized by IR, X-ray diffraction, X-ray absorption, electron paramagnetic resonance (EPA), and magnetic measurement. The five-coordinated, square pyramidal geometry around each iron atom in complex 1 remains intact when complex 1 is oxidized to yield complex 2. Magnetic measurements and EPA results show that there is only one unpaired electron in complex 1 (Stotal = 1/2) and no unpaired electron (Stotal = 0) in 2. The detailed geometric comparisons between complexes 1 and 2 provide understanding of the role that the unpaired electron plays in the chemical bonding of this trinuclear complex. Significant shortening of the Fe-Fe, Fe-N, and Fe-S distances around Fe(1) is observed when complex 1 is oxidized to 2. This result implicates that the removal of the unpaired electron does induce the strengthening of the Fe-Fe, Fe-N, and Fe-S bonds in the Fe(1) fragment. A significant shift of the νNO stretching frequency from 1751 cm-1 (1) to 1821, 1857 cm-1 (2) (KBr) also indicates the strengthening of the N-a bonds in complex 2. The EPA, X-ray absorption, magnetic measurements, and molecular orbital calculations lead to the conclusion that the unpaired electron in complex 1 is mainly allocated in the Fe(1) fragment and is best described as {Fe(1)NO}7, so that the unpaired electron is delocalized between Fe and NO via d-π* orbital interaction; some contributions from [Fe(2)NO] and [Fe(3)NO] as well as the thiolates associated with Fe (1) are also realized. According to MO calculations, the spin density of complex 1 is predominately located at the Fe atoms with 0.60, -0.15, and 0.25 at Fe(1), Fe(2), and Fe(3), respectively. [ABSTRACT FROM AUTHOR]

Two new isostructural complexes [M(H2biim)3][M(btc)(Hbiim)]•2H2O (M = Co, (1); M = Ni, (2)) (btc = 1,3,5-benzenetricarboxylate; H2biim = 2,2′-biimidazole) have been synthesized and characterized by single-crystal X-ray diffraction. They present a unique structure consisting of two distinct units: the monomeric cations [M(H2biim)3]2+ and the two-dimensional (2D) anionic polymer [M(Hbiim)(btc)]2-. In the anionic moiety, the Hbiim monoanion is simultaneously coordinated to one metal atom in a bidentate mode and further to another metal atom in a monodentate mode. The imidazolate groups bridge the two adjacent metal ions into a helical chain which is further arranged in left- and right-handed manners. These chains are bridged by btc ligands into a 2D brick wall structure. The most interesting aspect is that the [M(H2biim)3]2+ cations act as pillars and link the anionic layers via robust heteromeric hydrogen-bonded synthons R²2(9) and R¹2(7) formed by the uncoordinated oxygen atoms of carboxylate groups and the H2biim ligands, resulting in a microporous metal-organic framework with one-dimensional (1D) channels (ca. 11.85 Å ⊗ 11.85 Å for 1 and 11.43 Å ⊗ 11.43 Å for 2). Magnetic properties of these two complexes have also been studied in the temperature range of 2–300 K, and their magnetic susceptibilities obey the Curie-Weiss law in the temperature range of 20–300 K (for 1) and 2–300 K (for 2), respectively, showing anti-ferromagnetic coupling through imidazolate bridging. Taking into consideration the Heisenberg infinite chain model as well as the possibility of chain-to-chain and chain-to-cation interactions, the anti-ferromagnetic exchange of 2 is analyzed via a correction for the molecular field, giving the values of gcat = 2.296, gNi = 2.564, J = -13.30 cm-1, and zJ′ = -0.017 cm-1. The microporous frameworks are stable at ca. 350 °C. They do not collapse after removal of the guest water molecules in the channels, and they adsorb methanol molecules selectively. [ABSTRACT FROM AUTHOR]