Multistability at Room Temperature in a Bent-Shaped Spin-Crossover Complex Decorated with Long Alkyl Chains.

An iron(II) pyridyl-benzohydrazonate-based complex decorated with long alkyl chains is reported as a rare spin-crossover compound displaying a wide thermal hysteresis spanning room temperature. On heating, this compound exhibits a spin transition between a LS ground state and an ordered HS-LS phase with symmetry breaking from monoclinic P21/n into orthorhombic P21212 space groups. During cooling, the compound first transits into a magnetically distinguishable HS-LS phase with monoclinic P21 symmetry before returning into the LS phase. Interconversion between the two distinct HS-LS phases is the result of subtle structural changes in the alkyl chains and produces a second minor thermal hysteresis that superposes to the large one. This unprecedented result shows that the combination of a conventional cooperative spin transition and ligand-driven magnetic changes can promote magnetic tristability at room temperature.

Synthesis and lanthanide coordination chemistry of phosphine oxide decorated dibenzothiophene and dibenzothiophene sulfone platforms.

Syntheses for new ligands based upon dibenzothiophene and dibenzothiophene sulfone platforms, decorated with phosphine oxide and methylphosphine oxide donor groups, are described. Coordination chemistry of 4,6-bis(diphenylphosphinoylmethyl)dibenzothiophene (8), 4,6-bis(diphenylphosphinoylmethyl)dibenzothiophene-5,5-dioxide (9) and 4,6-bis(diphenylphosphinoyl)dibenzothiophene-5,5-dioxide (10) with lanthanide nitrates, Ln(NO3)3·(H2O)n is outlined, and crystal structure determinations reveal a range of chelation interactions on Ln(III) ions. The nitric acid dependence of the solvent extraction performance of 9 and 10 in 1,2-dichloroethane for Eu(III) and Am(III) is described and compared against the extraction behavior of related dibenzofuran ligands (2, 3; R = Ph) and n-octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (4) measured under identical conditions.

Synthesis, lanthanide coordination chemistry, and liquid-liquid extraction performance of CMPO-decorated pyridine and pyridine N-oxide platforms.

Syntheses for a set of new ligands containing one or two carbamoylmethylphosphine oxide (CMPO) fragments appended to pyridine and pyridine N-oxide platforms are described. Molecular mechanics analyses for gas phase lanthanide-ligand interactions for the pyridine N-oxides indicate that the trifunctional NOPOCO molecules, 2-{[Ph2P(O)][C(O)NEt2]C(H)}C5H4NO (7) and 2-{[Ph2P(O)][C(O)NEt2]CHCH2}C5H4NO (8), and pentafunctional NOPOP'O'COC'O' molecules, 2,6-{[Ph2P(O)][C(O)NEt2]C(H)}2C5H3NO (9) and 2,6-{[Ph2P(O)][C(O)NEt2]CHCH2}2C5H3NO (10), should be able to adopt, with minimal strain, tridentate and pentadentate chelate structures, respectively. As a test of these predictions, selected lanthanide coordination chemistry of the N-oxide derivatives was explored. Crystal structure analyses reveal the formation of a tridentate NOPOCO chelate structure for a 1:1 Pr(III) complex containing 7 while 8 adopts a mixed bidentate/bridging monodentate POCO/NO binding mode with Pr(III). Tridentate and tetradentate chelate structures are obtained for several 1:1 complexes of 9 while a pentadentate chelate structure is observed with 10. Emission spectroscopy for one complex, [Eu(9)(NO3)3], in methanol, shows that the Eu(III) ion resides in a low-symmetry site. Lifetime measurements for methanol and deuterated methanol solutions indicate the presence of four methanol molecules in the inner coordination sphere of the metal ion, in addition to the ligand, with the nitrate anions most likely dissociated. The solvent extraction performance of 7-10 in 1,2-dichloroethane for Eu(III) and Am(III) in nitric acid solutions was analyzed and compared with the performance of 2,6-bis(di-n-octylphosphinoylmethyl)pyridine N-oxide (TONOPOP'O') and n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (OPhDiBCMPO) measured under identical conditions.

Synthesis and coordination chemistry of phosphine oxide decorated dibenzofuran platforms.

A four-step synthesis for 4,6-bis(diphenylphosphinoylmethyl)dibenzofuran (4) from dibenzofuran and a two-step synthesis for 4,6-bis(diphenylphosphinoyl)dibenzofuran (5) are reported along with coordination chemistry of 4 with In(III), La(III), Pr(III), Nd(III), Er(III), and Pu(IV) and of 5 with Er(III). Crystal structure determinations for the ligands, 4·CH(3)OH and 5, the 1:1 complexes [In(4)(NO(3))(3)], [Pr(4)(NO(3))(3)(CH(3)CN)]·0.5CH(3)CN, [Er(4)(NO(3))(3)(CH(3)CN)]·CH(3)CN, [Pu(4)Cl(4)]·THF and the 2:1 complex [Nd(4)(2)(NO(3))(2)](2)(NO(3))(2)·(H(2)O)·4(CH(3)OH) are described. In these complexes, ligand 4 coordinates in a bidentate POP'O' mode via the two phosphine oxide O-atoms. The dibenzofuran ring O-atom points toward the central metal cations, but in every case it is more than 4 Å from the metal. A similar bidentate POP'O' chelate structure is formed between 5 and Er(III) in the complex, {[Er(5)(2)(NO(3))(2)](NO(3))·4(CH(3)OH)}(0.5), although the nonbonded Er···O(furan) distance is reduced to ∼3.6 Å. The observed bidentate chelation modes for 4 and 5 are consistent with results from molecular mechanics computations. The solvent extraction performance of 4 and 5 in 1,2-dichloroethane for Eu(III) and Am(III) in nitric acid solutions is described and compared against the extraction behavior of n-octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (OΦDiBCMPO) measured under identical conditions.

Dendron-functionalized core-shell superparamagnetic nanoparticles: magnetically recoverable and reusable catalysts for suzuki C--C cross-coupling reactions.

A metallodendron functionalized with dicyclohexyldiphosphino palladium complex was synthesized. The metallodendron was grafted onto core-shell superparamagnetic nanoparticles (gamma-Fe(2)O(3)/polymer, 200-500 nm) to give optimal catalytic reactivity in cross-coupling reactions. The grafted nanoparticles were used as recoverable and reusable catalysts for Suzuki C--C cross-coupling reactions. They showed remarkable reactivity towards iodo- and bromoarenes under mild conditions, and unprecedented reactivity towards chloroarenes. On completion of the catalytic reaction, the catalysts were readily recovered by using a simple magnet to attract the superparamagnetic grafted nanoparticles. Catalysts were recovered more than 25 times with almost no discernable loss of reactivity.

Molecule-based microelectromechanical sensors.

Incorporating functional molecules into sensor devices is an emerging area in molecular electronics that aims at exploiting the sensitivity of different molecules to their environment and turning it into an electrical signal. Among the emergent and integrated sensors, microelectromechanical systems (MEMS) are promising for their extreme sensitivity to mechanical events. However, to bring new functions to these devices, the functionalization of their surface with molecules is required. Herein, we present original electronic devices made of an organic microelectromechanical resonator functionalized with switchable magnetic molecules. The change of their mechanical properties and geometry induced by the switching of their magnetic state at a molecular level alters the device's dynamical behavior, resulting in a change of the resonance frequency. We demonstrate that these devices can be operated to sense light or thermal excitation. Moreover, thanks to the collective interaction of the switchable molecules, the device behaves as a non-volatile memory. Our results open up broad prospects of new flexible photo- and thermo-active hybrid devices for molecule-based data storage and sensors.

Synthesis and f-element ligation properties of NCMPO-decorated pyridine N-oxide platforms.

Stepwise syntheses of 2-{[2-(diphenylphosphoryl)acetamido]methyl}pyridine 1-oxide, 2-[Ph2P(O)CH2C(O)N(H)CH2]C5H4NO (6), 2-{[2-(diphenylphosphoryl)acetamido]methyl}-6-[(diphenylphosphoryl)methyl]pyridine 1-oxide, 2-[Ph2P(O)CH2C(O)N(H)CH2]-6-[Ph2P(O)CH2]C5H3NO (7) and 2,6-bis{[2-(diphenylphosphoryl)acetamido]methyl}pyridine 1-oxide, 2,6-[Ph2P(O)CH2C(O)N(H)CH2]2C5H3NO (8), are reported along with spectroscopic characterization data and single crystal X-ray diffraction structure determination for 6·2H2O, 7 and 2,6-[Ph2P(O)CH2C(O)N(H)CH2]2C5H3N·MeOH 18·MeOH, the pyridine precursor of 8. Molecular mechanics computations indicate that 6, 7 and 8 should experience minimal steric hindrance to donor group reorganization that would permit tridentate, tetradentate and pentadentate docking structures for the respective ligands on lanthanide cations. However, crystal structure determination for the lanthanide complexes, {[Yb(6)(NO3)3]·(MeOH)}n, {[Lu(6)(NO3)3]·(MeOH)}n, [Er(6)2(H2O)2](NO3)3·(H2O)4}n, {[La(13)(NO3)3(MeOH)]·(MeOH)}n, {[Eu(7)(NO3)2(EtOAc)0.5(H2O)0.5](NO3)}2·MeOH and [Dy3(7)4(NO3)4(H2O)2](NO3)5·(MeOH)5·(H2O)2 reveal solid-state structures with mixed chelating/bridging ligand : Ln(III) interactions that employ lower than the maximal denticity. The binding of 6 and 7 with Eu(III) in the solid state and in MeOH solutions is also accessed by emission spectroscopy. The acid dependence for solvent extractions with 6 and 7 in 1,2-dichloroethane for Eu(III) and Am(III) in nitric acid solutions is described and compared with the behavior of n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (OPhDiBCMPO, 1b) and 2-[(diphenyl)phosphinoylmethyl]pyridine N-oxide (DPhNOPO, 4a).

Enhanced catalyst recovery in an aqueous copper-free Sonogashira cross-coupling reaction.

We report the synthesis of a superparamagnetic nanoparticle MNP (γ-Fe(2)O(3)/polymer) supported dendritic catalyst based on a bulky electron-rich phosphine Pd(II) complex. The high reactivity of this catalyst is described in a copper-free Sonogashira C-C cross-coupling reaction in water, and the significant role of surfactant additives is highlighted in the recovery study.