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

Europium(III) Photoluminescence Governed by d⁸–d¹⁰ Heterometallophilic Interactions in Trimetallic Cyanido-Bridged Coordination Frameworks

We report an efficient pathway toward sensitization of red room temperature EuIII emission by the charge-transfer (CT) states related to d8–d10 heterometallophilic interactions achieved by the simultaneous application of tetracyanidometallates of PtII/PdII and dicyanidometallates of AuI/AgI in the construction of a trimetallic d–d–f assembly. The combination of Eu3+, [MII(CN)4]2– (M = Pt, Pd), and [MI(CN)2]− (M = Au, Ag) ions along with 4,4′-bipyridine N,N′-dioxide (4,4′-bpdo) results in four novel isostructural 2D {[EuIII(4,4′-bpdo)­(H2O)2]­[MII(CN)4]}·[MI(CN)2]·H2O (MII/MI = Pt/Au, 1; Pt/Ag, 2; Pd/Au, 3; Pd/Ag, 4) coordination networks. They are built of hybrid coordination layers, based on cyanido-bridged {EuIII[MII(CN)4]}n square grids coexisting with metal–organic {EuIII(4,4′-bpdo)}n chains, with the further attachment of [MI(CN)2]− ions through metallophilic {MII–MI} interactions. This results in dinuclear {MIIMI} units generating an orange emissive metal-to-metal-to-ligand charge-transfer (MMLCT) state, whose energy is tuned by the applied d8–d10 metal centers. Thanks to these CT states, 1–4 exhibit room temperature red EuIII photoluminescence enhanced by energy transfer from {MIIMI} units, with the additional role of 4,4′-bpdo also transferring the energy to lanthanides. These donor CT states lying in the visible range successfully broaden the available efficient excitation range up to 500 nm. The overall emission quantum yield ranges from 8(1)% for 4 to 15(2)% for 1, with the intermediate values for 2 and 3 relatively high among the reported EuIII-based compounds with tetracyanido- and dicyanidometallates. We found that the sensitization efficiency is equally high for all compounds because of the similar energies of the CT states, while the main differences are related to the observed emission lifetimes ranging from ca. 80 μs for 4 to 120–130 μs for 2 and 3 to ca. 180 μs for 1. This phenomenon was correlated with the energies of the vibrational states, e.g., cyanide stretching vibrations, responsible for nonradiative deactivation of EuIII excited states, which are the highest for the Pd/Ag pair of 4 and the lowest for the Pt/Au pair in 1. Thus, the heaviest pair of PtII/AuI cyanide metal complexes is proven to be the best candidate for the sensitization of room temperature EuIII luminescence

Near-Infrared Photoluminescence in Hexacyanido-Bridged Nd–Cr Layered Ferromagnet

Hexacyanidochromate­(III) anion is here explored as the building block for the construction of bimetallic 3d-4f coordination polymers that combine spin ordering and luminescence. We report the two-dimensional cyanido-bridged {[NdIII(pmmo)2­(H2O)3]­[CrIII(CN)6]} (1) layered framework obtained by the spontaneous crystallization from the aqueous solution of Nd3+, pyrimidine N-oxide (pmmo), and [CrIII(CN)6]3–. 1 crystallizes as light green plates in the orthorhombic Pbca space group and reveals a topology of a square grid built of nine-coordinated [NdIII(μ-NC)4­(H2O)3­(pmmo)2]− complexes of a nearly capped square antiprism geometry, and six-coordinated octahedral [CrIII(CN)6]3– moieties. Because of the presence of cyanide-mediated ferromagnetic coupling between paramagnetic NdIII (J = 9/2) and CrIII (S = 3/2) centers, 1 exhibits a long-range ferromagnetic ordering below Curie temperature of 2.8 K, with a tiny magnetization-field hysteresis loop detected at 1.8 K. Under the UV light irradiation, 1 shows the near-infrared fluorescence originated from the 4F3/2 → 4I9/2 (λmax = 895 nm) and 4F3/2 → 4I11/2 (λmax = 1060 nm) electronic transitions of NdIII. The near-infrared emission is realized through the energy transfer from [CrIII(CN)6]3– anions and pmmo ligands to NdIII centers which was possible due to the spectral overlap between the visible-light and near-infrared emission bands of CrIII and pmmo, and the absorption bands of NdIII. Thus, 1 can be considered as a novel type of bifunctional magneto-luminescent layered material taking advantage of the fruitful electronic and magnetic interplay between NdIII(pmmo) and [CrIII(CN)6]3– complexes

Reversible Guest-Induced Magnetic and Structural Single-Crystal-to-Single-Crystal Transformation in Microporous Coordination Network {[Ni(cyclam)]₃[W(CN)₈]₂}<i>_n</i>

Planar honeycomb-like coordination network {[Ni(cyclam)]3[W(CN)8]2}n (cyclam = 1,4,8,11-tetraazacyclotetradecane) was obtained in the self-assembly reaction of [Ni(cyclam)]2+ and [W(CN)]83-. Its structure is characterized by void channels along the a axis. The compound shows reversible water adsorption in the temperature range of 25−40 °C with the formation of {[Ni(cyclam)]3[W(CN)8]2}n·16nH2O, accompanied by single-crystal-to-single-crystal transformation. The structural transformation significantly changes the character of intraplane magnetic exchange interactions

Testing the High Spin Mn^II₉W^V₆ Cluster as Building Block for Three-Dimensional Coordination Networks

Pentadecanuclear high spin cyano-bridged {M′II9M′′V6(CN)48(solv)24} (M′ = 3d metal ions; M′′ = Mo, W; solv = H2O, alcohol) clusters are considered as building blocks for three-dimensional open networks. Self-assembly of MnII9WV6 clusters (S = 39/2) with 4,4′-bipyridine leads to their organization into an organic−inorganic hybrid coordination network {MnII9(4,4′-bpy)4[WV(CN)8]6(EtOH)12(H2O)4}·10EtOH 1 (System, triclinic; space group: P1̅, a = 17.1569(2) Å, b = 17.3835(2) Å, c = 19.2530(2) Å, α = 103.5520(10)°, β = 115.3950(10)°, γ = 98.3060(10)°, Z = 1). The clusters are connected through 4,4′-bpy spacers into a two-dimensional square-grid coordination framework extended in the ab crystallographic plane with the smallest intercluster separation along the a (Mn···W = 7.12 Å) and b (Mn···W = 7.15 Å) directions significantly lower than that along the c crystallographic direction (Mn···W = 8.64 Å). Direct current magnetic measurements suggest strong dominance of intracluster antiferromagnetic MnII−WV coupling over a very weak intercluster antiferromagnetic interaction

Grid-Type Two-Dimensional Magnetic Multinuclear Metal Complex: Strands of {[Cu^II(μ-4,4‘-bpy)]²⁺}<i>_n</i> Cross-Linked by Octacyanotungstate(V) Ions

Reaction of the preorganized strands of {[CuII(μ-4,4‘-bpy)]2+}n (4,4‘-bpy = 4,4‘-bipyridine) with [WV(CN)8]3- leads to a novel cyano-bridged CuII3WV2 complex [Cu(μ-4,4‘-bpy)(DMF)2][Cu(μ-4,4‘-bpy)(DMF)]2[WV(CN)8]2·2DMF· 2H2O 1. The structure of 1 consists of the expected 2-dimensional grid-type network which is built of infinite {[CuII(μ-4,4‘-bpy)]2+}n chains cross-linked by octacyanotungstate units. The CuII−NC−WV−CN−CuII linkage exhibits the topology of a 3,2-chain. The skeleton of the layer is additionally stabilized by a hydrogen bond network formed by terminal cyano ligands of the [W(CN)8]3- moiety and water molecules. The distance between the adjacent Cu3IIW2V chains within the layer is 11.12 Å along the a axis. The layers are connected by H-bonds of NCN−NDMF−NCN linkages into 3-D supramolecular architecture. The magnetic properties correspond to a dominant ferromagnetic coupling within the CuII3WV2 pentamer units (J = +35(4) cm-1) and much weaker effective AF interunit coupling which include both intra- and inter-3,2-chain interactions between pentamers (J‘ = −0.05(1) cm-1)

Testing the High Spin Mn^II₉W^V₆ Cluster as Building Block for Three-Dimensional Coordination Networks

Pentadecanuclear high spin cyano-bridged {M′II9M′′V6(CN)48(solv)24} (M′ = 3d metal ions; M′′ = Mo, W; solv = H2O, alcohol) clusters are considered as building blocks for three-dimensional open networks. Self-assembly of MnII9WV6 clusters (S = 39/2) with 4,4′-bipyridine leads to their organization into an organic−inorganic hybrid coordination network {MnII9(4,4′-bpy)4[WV(CN)8]6(EtOH)12(H2O)4}·10EtOH 1 (System, triclinic; space group: P1̅, a = 17.1569(2) Å, b = 17.3835(2) Å, c = 19.2530(2) Å, α = 103.5520(10)°, β = 115.3950(10)°, γ = 98.3060(10)°, Z = 1). The clusters are connected through 4,4′-bpy spacers into a two-dimensional square-grid coordination framework extended in the ab crystallographic plane with the smallest intercluster separation along the a (Mn···W = 7.12 Å) and b (Mn···W = 7.15 Å) directions significantly lower than that along the c crystallographic direction (Mn···W = 8.64 Å). Direct current magnetic measurements suggest strong dominance of intracluster antiferromagnetic MnII−WV coupling over a very weak intercluster antiferromagnetic interaction

Reversible Guest-Induced Magnetic and Structural Single-Crystal-to-Single-Crystal Transformation in Microporous Coordination Network {[Ni(cyclam)]₃[W(CN)₈]₂}<i>_n</i>

Planar honeycomb-like coordination network {[Ni(cyclam)]3[W(CN)8]2}n (cyclam = 1,4,8,11-tetraazacyclotetradecane) was obtained in the self-assembly reaction of [Ni(cyclam)]2+ and [W(CN)]83-. Its structure is characterized by void channels along the a axis. The compound shows reversible water adsorption in the temperature range of 25−40 °C with the formation of {[Ni(cyclam)]3[W(CN)8]2}n·16nH2O, accompanied by single-crystal-to-single-crystal transformation. The structural transformation significantly changes the character of intraplane magnetic exchange interactions

Testing the High Spin Mn^II₉W^V₆ Cluster as Building Block for Three-Dimensional Coordination Networks

Pentadecanuclear high spin cyano-bridged {M′II9M′′V6(CN)48(solv)24} (M′ = 3d metal ions; M′′ = Mo, W; solv = H2O, alcohol) clusters are considered as building blocks for three-dimensional open networks. Self-assembly of MnII9WV6 clusters (S = 39/2) with 4,4′-bipyridine leads to their organization into an organic−inorganic hybrid coordination network {MnII9(4,4′-bpy)4[WV(CN)8]6(EtOH)12(H2O)4}·10EtOH 1 (System, triclinic; space group: P1̅, a = 17.1569(2) Å, b = 17.3835(2) Å, c = 19.2530(2) Å, α = 103.5520(10)°, β = 115.3950(10)°, γ = 98.3060(10)°, Z = 1). The clusters are connected through 4,4′-bpy spacers into a two-dimensional square-grid coordination framework extended in the ab crystallographic plane with the smallest intercluster separation along the a (Mn···W = 7.12 Å) and b (Mn···W = 7.15 Å) directions significantly lower than that along the c crystallographic direction (Mn···W = 8.64 Å). Direct current magnetic measurements suggest strong dominance of intracluster antiferromagnetic MnII−WV coupling over a very weak intercluster antiferromagnetic interaction

Testing the High Spin Mn^II₉W^V₆ Cluster as Building Block for Three-Dimensional Coordination Networks

Pentadecanuclear high spin cyano-bridged {M′II9M′′V6(CN)48(solv)24} (M′ = 3d metal ions; M′′ = Mo, W; solv = H2O, alcohol) clusters are considered as building blocks for three-dimensional open networks. Self-assembly of MnII9WV6 clusters (S = 39/2) with 4,4′-bipyridine leads to their organization into an organic−inorganic hybrid coordination network {MnII9(4,4′-bpy)4[WV(CN)8]6(EtOH)12(H2O)4}·10EtOH 1 (System, triclinic; space group: P1̅, a = 17.1569(2) Å, b = 17.3835(2) Å, c = 19.2530(2) Å, α = 103.5520(10)°, β = 115.3950(10)°, γ = 98.3060(10)°, Z = 1). The clusters are connected through 4,4′-bpy spacers into a two-dimensional square-grid coordination framework extended in the ab crystallographic plane with the smallest intercluster separation along the a (Mn···W = 7.12 Å) and b (Mn···W = 7.15 Å) directions significantly lower than that along the c crystallographic direction (Mn···W = 8.64 Å). Direct current magnetic measurements suggest strong dominance of intracluster antiferromagnetic MnII−WV coupling over a very weak intercluster antiferromagnetic interaction