Szymon Chorazy

Multifunctionality in Bimetallic LnIII[WV(CN)8]3− (Ln=Gd, Nd) Coordination Helices: Optical Activity, Luminescence, and Magnetic Coupling

Two chiral luminescent derivatives of pyridine bis(oxazoline) (Pybox), (SS/RR)-iPr-Pybox (2,6-bis[4-isopropyl-2-oxazolin-2-yl]pyridine) and (SRSR/RSRS)-Ind-Pybox (2,6-bis[8H-indeno[1,2-d]oxazolin-2-yl]pyridine), have been combined with lanthanide ions (Gd(3+), Nd(3+)) and octacyanotungstate(V) metalloligand to afford a remarkable series of eight bimetallic CN(-)-bridged coordination chains: {[Ln(III)(SS/RR-iPr-Pybox)(dmf)4]3[W(V)(CN)8]3}n ⋅dmf⋅4u2009H2O (Ln = Gd, 1-SS and 1-RR; Ln = Nd, 2-SS and 2-RR) and {[Ln(III)(SRSR/RSRS-Ind-Pybox)(dmf)4][W(V)(CN)8]}n⋅5u2009MeCN⋅4u2009MeOH (Ln = Gd, 3-SRSR and 3-RSRS; Ln = Nd, 4-SRSR and 4-RSRS). These materials display enantiopure structural helicity, which results in strong optical activity in the range 200-450u2005nm, as confirmed by natural circular dichroism (NCD) spectra and the corresponding UV/Vis absorption spectra. Under irradiation with UV light, the Gd(III)-W(V) chains show dominant ligand-based red phosphorescence, with λmax ≈660u2005nm for 1-(SS/RR) and 680u2005nm for 3-(SRSR/RSRS). The Nd(III)-W(V) chains, 2-(SS/RR) and 4-(SRSR/RSRS), exhibit near-infrared luminescence with sharp lines at 986, 1066, and 1340u2005nm derived from intra-f (4)F3/2 → (4)I9/2,11/2,13/2 transitions of the Nd(III) centers. This emission is realized through efficient ligand-to-metal energy transfer from the Pybox derivative to the lanthanide ion. Due to the presence of paramagnetic lanthanide(III) and [W(V)(CN)8](3-) moieties connected by cyanide bridges, 1-(SS/RR) and 3-(SRSR/RSRS) are ferrimagnetic spin chains originating from antiferromagnetic coupling between Gd(III) (SGd = 7/2) and W(V) (SW = 1/2) centers with J1-(SS) = -0.96(1)u2005cm(-1), J1-(RR) =-0.95(1)u2005cm(-1), J3-(SRSR) = -0.91(1)u2005cm(-1), and J3-(RSRS) =-0.94(1)u2005cm(-1). 2-(SS/RR) and 4-(SRSR/RSRS) display ferromagnetic coupling within their Nd(III)-NC-W(V) linkages.

White Light Emissive DyIII Single‐Molecule Magnets Sensitized by Diamagnetic [CoIII(CN)6]3− Linkers

The self-assembly of Dy(III) -3-hydroxypyridine (3-OHpy) complexes with hexacyanidocobaltate(III) anions in water produces cyanido-bridged {[Dy(III) (3-OHpy)2 (H2 O)4 ] [Co(III) (CN)6 ]}⋅H2 O (1) chains. They reveal a single-molecule magnet (SMM) behavior with a large zero direct current (dc) field energy barrier, ΔE=266(12) cm(-1) (≈385u2005K), originating from the single-ion property of eight-coordinated Dy(III) of an elongated dodecahedral geometry, which are embedded with diamagnetic [Co(III) (CN)6 ](3-) ions into zig-zag coordination chains. The SMM character is enhanced by the external dc magnetic field, which results in the ΔE of 320(23) cm(-1) (≈460u2005K) at Hdc =1u2005kOe, and the opening of a butterfly hysteresis loop below 6u2005K. Complex 1 exhibits white Dy(III) -based emission realized by energy transfer from Co(III) and 3-OHpy to Dy(III) . Low temperature emission spectra were correlated with SMM property giving the estimation of the zero field ΔE. 1 is a unique example of bifunctional magneto-luminescent material combining white emission and slow magnetic relaxation with a large energy barrier, both controlled by rich structural and electronic interplay between Dy(III) , 3-OHpy, and [Co(III) (CN)6 ](3-) .

FeII Spin‐Crossover Phenomenon in the Pentadecanuclear {Fe9[Re(CN)8]6} Spherical Cluster

The self-assembly of iron(II) ions with rare octacyanidorhenate(V) metalloligands in a methanolic solution results in the formation of a nanometric pentadecanuclear {Fe(II) 9 [Re(V) (CN)8 ]6 (MeOH)24 }⋅10u2009MeOH (1) molecule with a six-capped body-centered cubic topology. The cluster demonstrates a thermally-induced spin-crossover phase transition at T1/2 =195u2005K which occurs selectively for a single Fe(II) u2005ion embedded in the center of a cluster core.

SHG-active LnIII–[MoI(CN)5(NO)]3− (Ln = Gd, Eu) magnetic coordination chains: a new route towards non-centrosymmetric molecule-based magnets

The rare heteroligand pentacyanidonitrosylmolybdate(I) anion was employed in the construction of d–f bimetallic cyanido-bridged {[LnIII(dmf)6][MoI(CN)5(NO)]} (Ln = Gd, 1; Eu, 2) chains crystallizing in the non-centrosymmetric Pna21 space group. 1 exhibits Gd–Mo antiferromagnetic coupling giving rise to the ferrimagnetic spin chain behaviour with the onset of magnetic ordering below 2 K, and shows high second harmonic generation (SHG) activity with SH susceptibility of 1.2 × 10−10 esu, opening a novel family of non-centrosymmetric molecule-based magnets.

The solvent effect on the structural and magnetic features of bidentate ligand-capped {CoII9[WV(CN)8]6} single-molecule magnets

Cyanido-bridged {CoII9[WV(CN)8]6} Single-Molecule Magnets grow spontaneously from the methanolic solution of Co2+ and [WV(CN)8]3− ions. Here, these molecules were combined with the 2,2′-bipyridine N-oxide (2,2′-bpmo) ligand resulting in three novel crystalline phases: {CoII[CoII(2,2′-bpmo)(MeOH)]6[CoII(2,2′-bpmo)(MeCN)]2[WV(CN)8]6}·8H2O·2MeCN·2MeOH (1) and {CoII[CoII(2,2′-bpmo)(MeOH)]8[WV(CN)8]6}·H2O·8.5MeCN·11.5MeOH (2) which grow from the MeOH–MeCN solution, and {CoII[CoII(2,2′-bpmo)(EtOH)]8[WV(CN)8]6}·3H2O·5.5MeCN·5EtOH (3) which crystallizes from the EtOH–MeCN mixture. They are constructed by {CoII9WV6} clusters of a six-capped body-centered cube topology, coordinating 2,2′-bpmo ligands at the external CoII sites. 1–3 exhibit different composition and geometrical arrangement in their outer fac-[CoII(μ-NC)3(2,2′-bpmo)(solvent)]− moieties, and different solvent organization in the intercluster space. This results in a well pronounced geometrical isomerism of cluster cores being further related to the diverse non-covalent interaction schemes governing the supramolecular arrangement of the molecules. 1, 2, and 3 reveal ferromagnetic coupling within Co–NC–W linkages leading to a high-spin ground state of 15/2, and slow magnetic relaxation at low temperatures. The single-molecule magnet characteristics are only slightly modulated by the solvent-dependent variation of the structural features.

High thermal durability of a layered Cs4CoII[WV(CN)8]Cl3 framework: crystallographic and 133Cs NMR spectroscopic studies

Temperature-variable single-crystal synchrotron X-ray diffraction and 133Cs NMR studies were performed for a cyanido-bridged layered metamagnet, Cs4CoII[WV(CN)8]Cl3 (1), to elucidate the origin of its unusually high thermal durability up to ca. 523 K (250 °C). 1 reveals a layered structure composed of negatively charged two-dimensional cyanido-bridged Co–W layers ({CoII[WV(CN)8]Cl3}4−) and cesium ions between and within the layers, where there is a lack of both non-coordinated and coordinated solvent molecules that is an important and characteristic feature of the crystal structure. The cesium ions are surrounded by chlorides and cyanides of the coordination layers, and some Cs+⋯Cl−, Cs+⋯N, and Cs+⋯C distances are shorter than the estimated sums of an ionic radius of Cs+ and ionic or van der Waals radii of Cl−/CN−. These short distances suggest strong interactions between Cs+ and Cl−/CN−, which stabilize the crystal structure by connecting the layers. The temperature-dependent single-crystal structural analyses show that there is no significant structural change upon heating up to 473 K, and indicate that the short distances between Cs+ and Cl−/CN− still remain. Thus, the high thermal durability of 1 is due to not only the absence of solvent molecules but also the existence of strong Cs+⋯Cl− and Cs+⋯−NC interactions. The 133Cs NMR spectrum shows four peaks assignable to the four independent Cs+ ions in the crystal structure. The observed peaks were located in high ppm owing to the hyperfine interactions between the nuclear spin of Cs and electron spins from the magnetic centers CoII and WV. As temperature increased, the peaks moved to low ppm, and the shifts of the peaks are expressed by the Curie–Weiss law indicating no large structural changes around Cs+ ions, that is, the Cs+ ions are fixed at the same positions. This proves the presence of strong interactions involving Cs+ and terminal ligands of cyanido-bridged layers of 1 being responsible for its high thermal stability.

TbCo and Tb0.5Dy0.5Co layered cyanido-bridged frameworks for construction of colorimetric and ratiometric luminescent thermometers

Heterometallic cyanido-bridged networks are versatile molecular platforms for diverse optical, magnetic and electronic functionalities. We present a pioneering synthetic route which employs polycyanidometallates in the preparation of unique d–f coordination systems revealing multi-stimuli responsive multi-coloured photoluminescence with potential application in colorimetric and ratiometric temperature sensing. We report two layered cyanido-bridged frameworks, bimetallic {[TbIII(4-OHpy)2(H2O)3][CoIII(CN)6]}·0.5H2O (1) (4-OHpy = 4-hydroxypyridine), and trimetallic {[TbIII0.5DyIII0.5(4-OHpy)2(H2O)3][CoIII(CN)6]}·0.5H2O (2), along with their structural and full physicochemical characterization. They exhibit room temperature visible photoluminescence within an extensive colour range, including white light emission, tunable through the applied lanthanide ions, and switchable by excitation with light through selective excitation of the green emissive TbIII, yellow emissive DyIII, blue luminescent 4-OHpy, and red luminescent [Co(CN)6]3− components. The emission properties of 1 and 2, including the energy transfer from organic ligands and cyanide complexes towards lanthanide ions, are strongly modulated by the change of temperature in the broad 120–300 K range. As a result, colorimetric luminescent temperature sensing exploiting a wide emission colour range was achieved for both 1 and 2. Moreover, 2 reveals the temperature dependent ratio between the intensities of sharp emission lines of TbIII and DyIII which can be used as a thermometric parametric for ratiometric luminescent detection of temperature. The related thermometer perfomance was examined for various excitation wavelengths, and the best parameters of relative thermal sensitivity, Sr > 1% K−1, with the maximal value 2.2(3)% K−1, and temperature uncertainty, δT < 1 K, are detected for 270 nm excitation in the range 120–200 K.