Control of the Speed of a Light-Induced Spin Transition through Mesoscale Core-Shell Architecture.

The rate of the light-induced spin transition in a coordination polymer network solid dramatically increases when included as the core in mesoscale core-shell particles. A series of photomagnetic coordination polymer core-shell heterostructures, based on the light-switchable Rb aCo b[Fe(CN)6] c· mH2O (RbCoFe-PBA) as core with the isostructural K jNi k[Cr(CN)6] l· nH2O (KNiCr-PBA) as shell, are studied using temperature-dependent powder X-ray diffraction and SQUID magnetometry. The core RbCoFe-PBA exhibits a charge transfer-induced spin transition (CTIST), which can be thermally and optically induced. When coupled to the shell, the rate of the optically induced transition from low spin to high spin increases. Isothermal relaxation from the optically induced high spin state of the core back to the low spin state and activation energies associated with the transition between these states were measured. The presence of a shell decreases the activation energy, which is associated with the elastic properties of the core. Numerical simulations using an electro-elastic model for the spin transition in core-shell particles supports the findings, demonstrating how coupling of the core to the shell changes the elastic properties of the system. The ability to tune the rate of optically induced magnetic and structural phase transitions through control of mesoscale architecture presents a new approach to the development of photoswitchable materials with tailored properties.

Sulfonium as a Surrogate for Ammonium: A New α7 Nicotinic Acetylcholine Receptor Partial Agonist with Desensitizing Activity.

Weak partial agonists that promote a desensitized state of the α7 nicotinic acetylcholine receptor (nAChR) have been associated with anti-inflammatory effects. Exemplar compounds feature a tertiary or quaternary ammonium group. We report the synthesis, structure, and electrophysiological evaluation of 1-ethyl-4-phenylthiomorpholin-1-ium triflate, a weak partial agonist with a sulfonium isostere of the ammonium pharmacophore. These results offer new insights in understanding nAChR-ligand interactions and provide a new chemical space to target the α7 nAChR.

Crystal structure of aqua-trans-bis-(dimethyl sulfoxide-κO)(pyridine-2,6-di-carboxyl-ato-κ3O2,N,O6)nickel(II).

In the title complex, [Ni(C7H3NO4)(C2H6OS)2(H2O)], the NiII cation is situated on a twofold rotation axis and exhibits a distorted octa-hedral NO5 coordination environment defined by a tridentate pyridine-2,6-di-carb-oxy-lic acid dianion (dpa2-), two dimethyl sulfoxide (DMSO) mol-ecules, and a water mol-ecule. In the crystal, the complex mol-ecules are linked by O-H⋯O and C-H⋯O hydrogen bonds into a three-dimensional network whereby DMSO mol-ecules from neighboring complexes overlap to form layers parallel to (001), alternating with layers of NiII-dpa2- moieties. The title complex is isotypic with its cobalt(II) analogue.

Synergistic photomagnetic effects in coordination polymer heterostructure particles of Hofmann-like Fe(4-phenylpyridine)2[Ni(CN)4]·0.5H2O and K0.4Ni[Cr(CN)6]0.8·nH2O.

New nanometer scale heterostructure particles of the two-dimensional Hofmann-like Fe(ii) spin-crossover network, Fe(phpy)2[Ni(CN)4]·0.5H2O {phpy = 4-phenylpyridine}, and the Prussian blue analogue K0.4Ni1.0[Cr(CN)6]0.8·nH2O (NiCr-PBA) have been developed, exhibiting synergistic photomagnetic effects, whereby the LIESST (light-induced electron spin-state trapping) effect in the Hofmann-like material induces a magnetization change in the NiCr-PBA. A variety of microscopic and spectroscopic techniques demonstrate the heterogeneous growth of the NiCr-PBA on the Hofmann seed particles and show the Hofmann compound retains its thermal and photoinduced spin transition properties in the heterostructure. The photoinduced magnetization change in the NiCr-PBA network arises from coupling of the two lattices despite dissimilar structure types. Isothermal magnetization minor hysteresis loop studies at 5 K show light absorption leads to changes in the local anisotropy of NiCr-PBA magnetic domains, providing direct evidence for a general magnetomechanical mechanism of light-switchable magnetism in coordination polymer heterostructures combining a photoactive material with a magnet.

Crystal structure of catena-poly[[(dimethyl sulfoxide-κO)(pyridine-2,6-di-carboxyl-ato-κ(3) O,N,O')nickel(II)]-µ-pyrazine-κ(2) N:N'].

The title coordination polymer, [Ni(C7H3NO4)(C4H4N2)(C2H6OS)] n , consists of [010] chains composed of Ni(II) ions linked by bis-monodentate-bridging pyrazine mol-ecules. Each of the two crystallographically distinct Ni(II) ions is located on a mirror plane and is additionally coordinated by a dimethyl sulfoxide (DMSO) ligand through the oxygen atom and by a tridentate 2,6-pyridine-di-carb-oxy-lic acid dianion through one of each of the carboxyl-ate oxygen atoms and the pyridine nitro-gen atom, leading to a distorted octa-hedral coordination environment. The title structure exhibits an inter-esting complementarity between coordinative bonding and π-π stacking where the Ni-Ni distance of 7.0296 (4) Šacross bridging pyrazine ligands allows the pyridine moieties on two adjacent chains to inter-digitate at halfway of the Ni-Ni distance, resulting in π-π stacking between pyridine moieties with a centroid-to-plane distance of 3.5148 (2) Å. The double-chain thus formed also exhibits C-H⋯π inter-actions between pyridine C-H groups on one chain and pyrazine mol-ecules on the other chain. As a result, the inter-ior of the double-chain structure is dominated by π-π stacking and C-H⋯ π inter-actions, while the space between the double-chains is occupied by a C-H⋯O hydrogen-bonding network involving DMSO ligands and carboxyl-ate groups located on the exterior of the double-chains. This separation of dissimilar inter-actions in the inter-ior and exterior of the double-chains further stabilizes the crystal structure.

Crystal structure of catena-poly[[[trans-bis(aceto-nitrile-κN)diaquacobalt(II)]-µ-pyrazine-κ(2) N:N'] dinitrate].

The central structural motif of the title coordination polymer, [Co(NO3)2(C4H4N2)(CH3CN)2(H2O)2] n , is a chain composed of Co(II) ions linked by bis-monodentate bridging pyrazine ligands through their N atoms. The Co(II) ion is located on an inversion center and is additionally coordinated by two O atoms of water mol-ecules and two N atoms of aceto-nitrile mol-ecules. The resultant N4O2 coordination sphere is distorted octa-hedral. The linear cationic chains extend parallel to the a axis and are aligned into layers parallel to the ac plane. Nitrate anions are situated in the space between the Co(II) chains and form O-H⋯O hydrogen bonds with the coordinating water mol-ecules, leading to a three-dimensional network structure. Weak C-H⋯O hydrogen bonds are also present between pyrazine or aceto-nitrile mol-ecules and the nitrate anions.