The synthesis of three different europium tetracyanoplatinates all incorporating 2,2':6',2''-terpyridine (terpy) have been carried out in acetonitrile/water mixtures by reaction of Eu(3+) salts with terpy and potassium tetracyanoplatinate. The use of different Eu(3+) sources results in the isolation of Eu(C(15)H(11)N(3))(H(2)O)(2)(NO(3))(Pt(CN)(4)) x CH(3)CN (1), {Eu(C(15)H(11)N(3))(H(2)O)(3)}(2)(Pt(CN)(4))(3) x 2 H(2)O (2), or [Eu(C(15)H(11)N(3))(H(2)O)(2)(CH(3)COO)(2)](2)Pt(CN)(4) x 3 H(2)O (3) for the nitrate, triflate, or acetate salts, respectively. All three compounds have been prepared as colorless crystals, and single-crystal X-ray diffraction has been used to investigate their structural features. Crystallographic data (MoK alpha, lambda = 0.71073 A, T = 290 K): 1, monoclinic, space group P2(1)/c, a = 12.835(1), b = 15.239(1), c = 13.751(2) A, beta = 105.594(9) degrees, V = 2590.8(5) A(3), Z = 4; 2, triclinic, space group P1, a = 9.1802(8) A, b = 10.8008(9) A, c = 13.5437(9) A, alpha = 84.491(6) degrees, beta = 75.063(7) degrees, gamma = 79.055(7) degrees, V = 1272.4(2) A(3), Z = 1; 3, triclinic, space group P1, a = 12.110(3) A, b = 12.7273(11) A, c = 18.7054(16) A, alpha = 92.859(7) degrees, beta = 92.200(11) degrees, gamma = 118.057(10) degrees, V = 2534.8(7) A(3), Z = 2. Variation of the counteranions in these systems provides the opportunity to modify the structures and coordination environment of Eu(3+) for 1-3. Compounds 1 and 2 are both one-dimensional, polymeric compounds that contain Eu(3+) ions chelated by terpy and bridged by tetracyanoplatinate anions. 3 is a zero-dimensional complex salt in which Eu(3+) is coordinated by terpy, acetate, and water, but not tetracyanoplatinate. The structural differences result in varying sensitization phenomena for the three compounds. Compounds 1 and 2 display efficient donor-acceptor intramolecular energy transfer (IET) where dual donor species, terpyridine and tetracyanoplatinate, simultaneously enhance the acceptor Eu(3+) emission. In both compounds the donor species are directly coordinated to the acceptor ion, and hence a highly efficient dual-donor effect is exhibited for the IET mechanisms. In 3 where only the terpy ligand is directly coordinated to Eu(3+), the sensitization involves only one donor species. The Pt(CN)(4)(2-) unit in 3, which lacks direct bonding to Eu(3+), exhibits strong emission indicating the lack of cooperative enhancement of the lanthanide emission.

The highly luminescent bimetallic cyanide materials, Gd(terpy)(H(2)O)(NO(3))(2)M(CN)(2) (M = Au, Ag; GdAu and GdAg, respectively) are quick and easy to synthesize under ambient conditions. A characteristic feature exhibited by both solid-state compounds is an intense red emission when excited with UV light. Additionally, GdAu exhibits a broad-band green emission upon excitation in the near UV region. A combination of structural and spectroscopic results for the compounds helps explain the underlying conditions responsible for their unique properties. Single-crystal X-ray diffraction experiments expose their structural features, including the fact that they are isostructural. Crystallographic data for the representative GdAu compound (Mo K(α), λ = 0.71073 Å, T = 290 K): triclinic, space group P ̅1, a = 7.5707(3) Å, b = 10.0671(4) Å, c = 15.1260(4) Å, α = 74.923(3)°, β = 78.151(3)°, γ = 88.401(3)°, V = 1089.04(7) Å(3), and Z = 2. Although the compounds crystallize as dimers containing M···M distances smaller than the sum of their van der Waals radii, the Au···Au (3.5054(4) Å) and/or the Ag···Ag (3.6553(5) Å) interactions are relatively weak and are not responsible for the low energy red emission. Rather, the green emission in GdAu presumably originates from the [Au(CN)(2)(-)](2) dimeric excimer, while the [Ag(CN)(2)(-)](2) dimers in GdAg do not display visible emission at either 290 or 77 K. The unusual red emission exhibited by both compounds likely originates from the formation of an excited state exciplex that involves intermolecular π-stacking of 2,2':6',2"-terpyridine ligands. The room-temperature and low-temperature steady-state photoluminescent properties, along with detailed time-dependent, lifetime, and quantum yield spectroscopic data provide evidence regarding the sources of the multiple visible emissions exhibited by these complexes.

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