Lanthanide Hexacyanidoruthenate Frameworks for Multicolor to White-Light Emission Realized by the Combination of d-d, d-f, and f-f Electronic Transitions.

We report an effective strategy toward tunable room-temperature multicolor to white-light emission realized by mixing three different lanthanide ions (Sm3+, Tb3+, and Ce3+) in three-dimensional (3D) coordination frameworks based on hexacyanidoruthenate(II) metalloligands. Mono-lanthanide compounds, K{LnIII(H2O)n[RuII(CN)6]}·mH2O (1, Ln = La, n = 3, m = 1.2; 2, Ln = Ce, n = 3, m = 1.3; 3, Ln = Sm, n = 2, m = 2.4; 4, Ln = Tb, n = 2, m = 2.4) are 3D cyanido-bridged networks based on the Ln-NC-Ru linkages, with cavities occupied by K+ ions and water molecules. They crystallize differently for larger (1, 2) and smaller (3, 4) lanthanides, in the hexagonal P63/m or the orthorhombic Cmcm space groups, respectively. All exhibit luminescence under the UV excitation, including weak blue emission in 1 due to the d-d 3T1g → 1A1g electronic transition of RuII, as well as much stronger blue emission in 2 related to the d-f 2D3/2 → 2F5/2,7/2 transitions of CeIII, red emission in 3 due to the f-f 4G5/2 → 6H5/2,7/2,9/2,11/2 transitions of SmIII, and green emission in 4 related to the f-f 5D4 → 7F6,5,4,3 transitions of TbIII. The lanthanide emissions, especially those of SmIII, take advantage of the RuII-to-LnIII energy transfer. The CeIII and TbIII emissions are also supported by the excitation of the d-f electronic states. Exploring emission features of the LnIII-RuII networks, two series of heterobi-lanthanide systems, K{SmxCe1-x(H2O)n[Ru(CN)6]}·mH2O (x = 0.47, 0.88, 0.88, 0.99, 0.998; 5-9) and K{TbxCe1-x(H2O)n[Ru(CN)6]}·mH2O (x = 0.56, 0.65, 0.93, 0.99, 0.997; 10-14) were prepared. They exhibit the composition- and excitation-dependent tuning of emission from blue to red and blue to green, respectively. Finally, the heterotri-lanthanide system of the K{Sm0.4Tb0.599Ce0.001(H2O)2[Ru(CN)6]}·2.5H2O (15) composition shows the rich emission spectrum consisting of the peaks related to CeIII, TbIII, and SmIII centers, which gives the emission color tuning from blue to orange and white-light emission of the CIE 1931 xy parameters of 0.325, 0.333.

Octacyanidorhenate(V) Ion as an Efficient Linker for Hysteretic Two-Step Iron(II) Spin Crossover Switchable by Temperature, Light, and Pressure.

A two-step hysteretic FeII spin crossover (SCO) effect was achieved in programmed layered Cs{[Fe(3-CNpy)2 ][Re(CN)8 ]}⋅H2 O (1) (3-CNpy=3-cyanopyridine) assembly consisting of cyanido-bridged FeII -ReV square grid sheets bonded by Cs+ ions. The presence of two non-equivalent FeII sites and the conjunction of 2D bimetallic coordination network with non-covalent interlayer interactions involving Cs+ , [ReV (CN)8 ]3- ions, and 3-CNpy ligands, leads to the occurrence of two steps of thermal SCO with strong cooperativity giving a double thermal hysteresis loop. The resulting spin-transition phenomenon could be tuned by an external pressure giving the room-temperature range of SCO, as well as by visible-light irradiation, inducing an efficient recovery of the high-spin FeII state at low temperatures. We prove that octacyanidorhenate(V) ion is an outstanding metalloligand for induction of a cooperative multistep, multiswitchable FeII SCO effect.

Connecting Visible Photoluminescence and Slow Magnetic Relaxation in Dysprosium(III) Octacyanidorhenate(V) Helices.

Functional crystalline materials based on bimetallic cyanido-bridged {[DyIII(4-Mephen)(dmf)4][MV(CN)8]}·0.5H2O (M = Re, 1; Mo, 2; W, 3; 4-Mephen = 4-methyl-1,10-phenanthroline) helices have been prepared. 1 is the first heterometallic coordination polymer incorporating an unexplored [ReV(CN)8]3- ion. Implementation of the ReV-based diamagnetic analogue of broadly investigated paramagnetic [MoV(CN)8]3- and [WV(CN)8]3- ions into the d-f coordination framework results in yellow photoluminescence originating from 4F9/2 → 6H J f-f electronic transitions of DyIII sensitized by 4-Mephen, and field-induced slow magnetic relaxation related to the single-ion anisotropy of the dysprosium(III) complexes. We prove that [ReV(CN)8]3- can work as a noninnocent metalloligand in the preparation of emissive 4f-metal-based single-molecule magnets.

Hybrid organic-inorganic connectivity of NdIII(pyrazine-N,N'-dioxide)[CoIII(CN)6]3- coordination chains for creating near-infrared emissive Nd(iii) showing field-induced slow magnetic relaxation.

A near-infrared emissive and magnetically anisotropic Nd(iii) complex is formed within a hybrid organic-inorganic {[NdIII(pzdo)(H2O)4][CoIII(CN)6]}·0.5(pzdo)·4H2O (1) (pzdo = pyrazine-N,N'-dioxide) ladder chain built of coexisting Nd-pzdo-Nd and Nd-NC-Co molecular bridges. 1 reveals two NdIII-centered properties, a field-induced slow magnetic relaxation of a single-ion origin with a thermal energy barrier of ΔE/kB = 51(2) K at Hdc = 1 kOe, and a near-infrared fluorescence sensitized by organic and inorganic linkers.