Binary and Ternary Core–Shell Crystals of Polynuclear Coordination Clusters via Epitaxial Growth

For the first time, an abundant series of 12 colorful binary and ternary millimeter-sized core–shell composite crystals, representative of hierarchical crystalline species, were designed and prepared from functional magnetic polynuclear clusters phases using the epitaxial growth method. The synthesis is based on isomorphous (space group C2/c) crystalline phases composed of 15 nuclear clusters {M9[WV(CN)8]6(MeOH)24} (M9W6) (M, color = MnII, pale brown; FeII, green; CoII, red; NiII yellow; and an Fe/Co 2:1 mixture, dark brown, respectively) of six-capped body-centered-cubic topology, revealing appealing magnetic properties such as a high spin in the ground state, slow magnetic relaxation, and structural spin-phase transitions. A series of 11 binary core–shell composites and 1 ternary composite have been reproducibly synthetized and carefully characterized from a structural and composition point of view. Phase composition agreement and the size of the interface of ca. 10 μm were assessed using microscopic observations, single-crystal X-ray diffration, and scanning electron microscopy─energy-dispersive spectroscopy. SQUID measurements reveal an active spin transition Fe6Co3W6 seed compound enveloped within the paramagnetic Mn9W6 crystalline shell, providing a rare example of a millimeter-sized hierarchical crystalline architecture, Fe6Co3W6@Mn9W6, with a switchable function

Site Selectivity for the Spin States and Spin Crossover in Undecanuclear Heterometallic Cyanido-Bridged Clusters

Polynuclear molecular clusters offer an opportunity to design new hierarchical switchable materials with collective properties, based on variation of the chemical composition, size, shapes, and overall building blocks organization. In this study, we rationally designed and constructed an unprecedented series of cyanido-bridged nanoclusters realizing new undecanuclear topology: FeII[FeII(bzbpen)]6[WV(CN)8]2[WIV(CN)8]2·18MeOH (1), NaI[CoII(bzbpen)]6[WV(CN)8]3[WIV(CN)8]·28MeOH (2), NaI[NiII(bzbpen)]6[WV(CN)8]3[WIV(CN)8]·27MeOH (3), and CoII[CoII(R/S-pabh)2]6[WV(CN)8]2[WIV(CN)8]2·26MeOH [4R and 4S; bzbpen = N1,N2-dibenzyl-N1,N2-bis(pyridin-2-ylmethyl)ethane-1,2-diamine; R/S-pabh = (R/S)-N-(1-naphthyl)-1-(pyridin-2-yl)methanimine], of size up to 11 nm3, ca. 2.0 × 2.2 × 2.5 nm (1–3) and ca. 1.4 × 2.5 × 2.5 nm (4). 1, 2, and 4 exhibit site selectivity for the spin states and spin transition related to the structural speciation based on subtle exogenous and endogenous effects imposed on similar but distinguishable 3d metal-ion-coordination moieties. 1 exhibits a mid-temperature-range spin-crossover (SCO) behavior that is more advanced than the previously reported SCO clusters based on octacyanidometallates and an onset of SCO behavior close to room temperature. The latter feature is also present in 2 and 4, which suggests the emergence of CoII-centered SCO not observed in previous bimetallic cyanido-bridged CoII–WV/IV systems. In addition, reversible switching of the SCO behavior in 1 via a single-crystal-to-single-crystal transformation during desolvation was also documented

New Dinuclear Macrocyclic Copper(II) Complexes as Potentially Fluorescent and Magnetic Materials

Two dinuclear copper(II) complexes with macrocyclic Schiff bases K1 and K2 were prepared by the template reaction of (R)-(+)-1,1′-binaphthalene-2,2′-diamine and 2-hydroxy-5-methyl-1,3-benzenedicarboxaldehyde K1, or 4-tert-butyl-2,6-diformylphenol K2 with copper(II) chloride dihydrate. The compounds were characterized by spectroscopic methods. X-ray crystal structure determination and DFT calculations confirmed their geometry in solution and in the solid phase. Moreover, intermolecular interactions in the crystal structure of K2 were analyzed using 3D Hirshfeld surfaces and the related 2D fingerprint plots. The magnetic study revealed very strong antiferromagnetic CuII-CuII exchange interactions, which were supported by magneto-structural correlation and DFT calculations conducted within a broken symmetry (BS) framework. Complexes K1 and K2 exhibited luminescent properties that may be of great importance in the search for new OLEDs. Both K1 and K2 complexes showed emissions in the range of 392–424 nm in solutions at various polarities. Thin materials of the studied compounds were deposited on Si(111) by the spin-coating method or by thermal vapor deposition and studied by scanning electron microscopy (SEM/EDS), atomic force microscopy (AFM), and fluorescence spectroscopy. The thermally deposited K1 and K2 materials showed high fluorescence intensity in the range of 318–531 nm for K1/Si and 326–472 nm for the K2/Si material, indicating that they could be used in optical devices

Cyanido-Bridged Clusters with Remote N‑Oxide Groups for Branched Multimetallic Systems

The combination of [W^V(CN)₈]^3– anions with 3d metal cations M^II in MeOH leads to the formation of pentadecanuclear spherical cyanido-bridged clusters {M­[M­(solv)₃]₈[M′(CN)₈]₆}, <b>M</b>_<b>9</b><b>M′</b>_<b>6</b>. By decorating their surface with organic ligands or/and by installation of different ions in their coordination skeleton, one could tune high spin in the ground state, slow relaxation of magnetization, or structural/spin phase transition. In this work we present the extended molecular high spin (<i>S</i>_GS = ¹⁵/₂, <i>g</i>_eff = 3.4) clusters or chains of clusters {Co₉W₆(<i>N</i>,<i>O</i>-L)_<i>x</i>} (<i>N</i>,<i>O</i>-L – pyrazine mono-N-oxide, <i>pzmo</i>; 4,4-bipyridine mono-N-oxide – 4,4′-<i>bpmo</i>) equipped with the structurally ordered remote (2–2.5 nm) N-oxide functions, as a result of deliberate combination of solvated Co₉W₆ supercomplexes with asymmetric <i>N</i>,<i>O</i>-donor linkers L. The systematic occurrence of such motifs in the series <b>1</b>–<b>3</b> is a result of preference for the Co–N_L coordination over the Co–O_L coordination, controlled also by strongly competing supramolecular interactions including simple hydrogen bonding {_LNO···H-donor} as well as cooperative π-costacked hydrogen bonding in double cyclic synthons {Co–O–H_MeOH···O–N_bpmoN−}₂. The observed coordination backbones are discussed in terms of the potential to bind the specific external molecular units and create the new type of branched molecular organization. The magnetic properties are confronted with structural differences along <b>1</b>–<b>3</b>, considering coordination polyhedra, Co–N bond lengths, Co–N–C angles, and hydrogen bonds. The diversity of slow magnetic relaxation images for the known Co₉W₆ based phases are discussed in terms of local deformation of Co coordination polyhedra and global deformation of cyanide bridged backbones