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

[Image: see text] We report an effective strategy toward tunable room-temperature multicolor to white-light emission realized by mixing three different lanthanide ions (Sm(3+), Tb(3+), and Ce(3+)) in three-dimensional (3D) coordination frameworks based on hexacyanidoruthenate(II) metalloligands. Mono-lanthanide compounds, K{Ln(III)(H(2)O)(n)[Ru(II)(CN)(6)]}·mH(2)O (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 P6(3)/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 (3)T(1g) → (1)A(1g) electronic transition of Ru(II), as well as much stronger blue emission in 2 related to the d-f (2)D(3/2) → (2)F(5/2,7/2) transitions of Ce(III), red emission in 3 due to the f-f (4)G(5/2) → (6)H(5/2,7/2,9/2,11/2) transitions of Sm(III), and green emission in 4 related to the f-f (5)D(4) → (7)F(6,5,4,3) transitions of Tb(III). The lanthanide emissions, especially those of Sm(III), take advantage of the Ru(II)-to-Ln(III) energy transfer. The Ce(III) and Tb(III) emissions are also supported by the excitation of the d-f electronic states. Exploring emission features of the Ln(III)–Ru(II) networks, two series of heterobi-lanthanide systems, K{Sm(x)Ce(1–x)(H(2)O)(n)[Ru(CN)(6)]}·mH(2)O (x = 0.47, 0.88, 0.88, 0.99, 0.998; 5–9) and K{Tb(x)Ce(1–x)(H(2)O)(n)[Ru(CN)(6)]}·mH(2)O (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{Sm(0.4)Tb(0.599)Ce(0.001)(H(2)O)(2)[Ru(CN)(6)]}·2.5H(2)O (15) composition shows the rich emission spectrum consisting of the peaks related to Ce(III), Tb(III), and Sm(III) 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.