Emission Enhancement through Dual Donor Sensitization: Modulation of Structural and Spectroscopic Properties in a Series of Europium Tetracyanoplatinates

Abstract

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.

New dyes with enhanced two-photon absorption cross-sections based on the Cd(II) and 4′-(4-[4-(imidazole)styryl]phenyl)-2,2′ : 6′,2″-terpyridine

“…Two-photon absorption dyes 2995 dye 3 formed a 2-D framework through π-π stacking interactions (green dashed line, the shortest distance is 3.475 Å, plum dashed line, the shortest distance is 3.035 Å) between the neighboring dimers along the c-axis. In addition, C-HÁ Á ÁI interactions (d (H33Á Á ÁI2) [15], which is assigned to π-π ⁄ transitions [16]. The absorption profile and maxima of all of the compounds are almost identical in different solvents, suggesting that ground state electronic structures are independent of solvent polarity and small dipole moments associated with the ICT transitions.…”

Lanthanide Photoluminescence in Heterometallic Polycyanidometallate-Based Coordination Networks

“…Following the promising optical properties of 3D Ln III –[Pt II (CN) 4 ] 2− networks, a considerable number of the related d–f cyanido-bridged coordination polymers revealing photoluminescent functionalities were reported (Table 2) [80,81,82,83,84,85,86,87,88]. The insertion of 2,2’:6’2”-terpyridine (terpy) into the self-assembled Ln III –Pt II system resulted in the one-dimensional [Ln III (terpy)(H 2 O) 2 (NO 3 )][Pt II (CN) 4 ]· n (solvent) (Ln = Eu, Tb) zig-zag chains (Figure 4a) [81,87].…”

“…The crucial role of direct coordination of both terpy and [Pt II (CN) 4 ] 2− ions to the 4f metal centre was precisely investigated for the Eu III –terpy–Pt II system, for which three different crystalline phases, two cyanido-bridged chains, a zig-zag-type [Eu III (terpy)(H 2 O) 2 (NO 3 )][Pt II (CN) 4 ]·MeCN, and a ladder-type [Eu III (terpy)(H 2 O) 3 ] 2 [Pt II (CN) 4 ] 3 ·2H 2 O, along with an ionic salt, [Eu III (terpy)(H 2 O) 2 (CH 3 COO) 2 ] 2 ·{Pt II (CN) 4 }·3H 2 O, were obtained. For the EuPt one-dimensional coordination polymers, both terpy and cyanide complex are directly bonded to Eu III giving the efficient energy transfer, while the ionic EuPt salt reveals only terpy-to-Eu 3+ energy transfer, with the additional green luminescence related to the non-coordinated [Pt II (CN) 4 ] 2− ions [82]. The similar effect was also presented for the Tb III –Pt II systems with terpy and its 4’-chloro-2,2’:6’2”-terpyridine (terpyCl) derivative.…”

Dichloridobis(methanol-κO)[cis-(±)-2,4,5-tris(pyridin-2-yl)-2-imidazoline-κ3 N 2,N 3,N 4]ytterbium(III) chloride

“…For related Yb (III) complexes, see: Li et al (2007); Xu et al (2009); Stojanovic et al (2010); Okawara et al (2012). For potential applications of polypyridyl chelating ligands in magnetic, electronic and luminescent devices, see: Freidzon et al (2011); Maynard et al (2009); Thomas et al (2012).…”