A simple change of the substituents in the bridging ligand allows tuning of the ordering temperatures, Tc, in the new family of layered chiral magnets A[M(II)M(III)(X2An)3]·G (A = [(H3O)(phz)3](+) (phz = phenazine) or NBu4(+); X2An(2-) = C6O4X2(2-) = 2,5-dihydroxy-1,4-benzoquinone derivative dianion, with M(III) = Cr, Fe; M(II) = Mn, Fe, Co, etc.; X = Cl, Br, I, H; G = water or acetone). Depending on the nature of X, an increase in Tc from ca. 5.5 to 6.3, 8.2, and 11.0 K (for X = Cl, Br, I, and H, respectively) is observed in the MnCr derivative. Furthermore, the presence of the chiral cation [(H3O)(phz)3](+), formed by the association of a hydronium ion with three phenazine molecules, leads to a chiral structure where the Δ-[(H3O)(phz)3](+) cations are always located below the Δ-[Cr(Cl2An)3](3-) centers, leading to a very unusual localization of both kinds of metals (Cr and Mn) and to an eclipsed disposition of the layers. This eclipsed disposition generates hexagonal channels with a void volume of ca. 20% where guest molecules (acetone and water) can be reversibly absorbed. Here we present the structural and magnetic characterization of this new family of anilato-based molecular magnets.

Covalent Organic Frameworks (COFs), an emerging class of crystalline porous materials,are proposed as anew type of support for grafting lanthanide ions (Ln 3+ )a nd employing these hybrid materials as ratiometric luminescent thermometers.ATpBpy-COF-prepared from 1,3,5-triformylphloroglucinol (Tp) and 2,2'-bipyridine-5,5'-diamine (Bpy) grafted with Eu/Tb and Dy acetylacetone (acac) complexes can be successfully used as al uminescent thermometer in the 10-360 K( Eu) and 280-440 K( Tb) ranges with good sensing properties (thermal sensitivity up to 1.403 %K À1 ,t emperature uncertainty dT < 1Kabove110 K). Forthe Eu/Tb systems,we observe an unusual and rarely reported behavior,t hat is,n o thermal quenching of the Tb 3+ emission, aresult of the absence of ion-to-ligand/host energy back-transfer.T he LnCOF materials proposed here could be anew class of materials employed for temperature-sensing applications following up on the wellknownluminescent metal-organic framework thermometers.

We report the first combined optical and structural investigation of the water free Er-quinolinolate complex, an organo-lanthanide system of interest for 1.5-microm telecom applications. Structural data demonstrate that the complex has a trinuclear structure (Er3Q9) which provides the Er metals with an octa-coordination by the organic ligand and prevents solvent and water molecules from entering the lanthanide coordination sphere. The results of the structural analysis allow us to infer that the strong Er luminescence quenching exhibited by the Er3Q9 complex is due uniquely to resonant energy transfer to the aromatic C-H vibrations of the ligand, providing the correct tools to design more efficient emitters.

Here we report on new tris(haloanilato)metallate(III) complexes with general formula [A]3[M(X2An)3] (A = (n-Bu)4N(+), (Ph)4P(+); M = Cr(III), Fe(III); X2An = 3,6-dihalo derivatives of 2,5-dihydroxybenzoquinone (H4C6O4), chloranilate (Cl2An(2-)), bromanilate (Br2An(2-)) and iodanilate (I2An(2-))), obtained by a general synthetic strategy, and their full characterization. The crystal structures of these Fe(III) and Cr(III) haloanilate complexes consist of anions formed by homoleptic complexes formulated as [M(X2An)3](3-) and (Et)3NH(+), (n-Bu)4N(+), or (Ph4)P(+) cations. All complexes exhibit octahedral coordination geometry with metal ions surrounded by six oxygen atoms from three chelate ligands. These complexes are chiral according to the metal coordination of three bidentate ligands, and both Λ and Δ enantiomers are present in their crystal lattice. The packing of [(n-Bu)4N]3[Cr(I2An)3] (5a) shows that the complexes form supramolecular dimers that are held together by two symmetry related I···O interactions (3.092(8) Å), considerably shorter than the sum of iodine and oxygen van der Waals radii (3.50 Å). The I···O interaction can be regarded as a halogen bond (XB), where the iodine behaves as the XB donor and the oxygen atom as the XB acceptor. This is in agreement with the properties of the electrostatic potential for [Cr(I2An)3](3-) that predicts a negative charge accumulation on the peripheral oxygen atoms and a positive charge accumulation on the iodine. The magnetic behaviour of all complexes, except 5a, may be explained by considering a set of paramagnetic non-interacting Fe(III) or Cr(III) ions, taking into account the zero-field splitting effect. The presence of strong XB interactions in 5a are able, instead, to promote antiferromagnetic interactions among paramagnetic centers at low temperature, as shown by the fit with the Curie-Weiss law, in agreement with the formation of halogen-bonded supramolecular dimers.

CsPb(Cl 1−x Br x ) 3 perovskite nanocrystals (NCs) doped with Yb 3+ ions have recently attracted large attention for their applications in photovoltaics in view of the high quantum yield, exceeding 100% of Yb 3+ emission at ∼1 μm. In contrast, the particularly relevant Er 3+ emission at 1.5 μm in the third telecommunication window, of high interest in silicon integrated photonics, has been so far largely neglected in view of the weak emission performance displayed by Er 3+ -doped NCs. Comprehensive steady-state and time-resolved spectroscopic measurements provide insights into the underlying mechanisms of Yb 3+ and Er 3+ sensitization to rationalize the anomalous different behavior of these two emitters in singly doped NCs. We propose that single-photon excitation of two Yb 3+ ions possibly occurs through a transient internal redox mechanism in the perovskite host, while this pathway is unviable for Er 3+ . In turn, Yb 3+ -bridged Er 3+ sensitization, boosts the Er 3+ luminescence at ∼1.5 μm by 10 4 -fold compared to Er 3+ singly doped NCs, and a relative high quantum yield of ∼6% and extremely long lifetime (∼3 ms) are obtained. The resulting high Er 3+ excited state densities, combined with the large absorption cross-sections of the semiconducting CsPbCl 3 matrix make Er 3+ -doped perovskite promising innovative materials to realize photonic devices operating at telecommunication wavelengths.

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We investigate the quenching of the near infrared light emission in Er 3+ complexes induced by the resonant dipolar interaction between the rare-earth ion and high frequency vibrations of the organic ligand. The nonradiative decay rate of the lanthanide ion is discussed in terms of a continuous medium approximation, which depends only on a few, easily accessible spectroscopic and structural data. The model accounts well for the available experimental results in Er 3+ complexes, and predicts an ϳ100% light emission quantum yield in fully halogenated systems. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2177431͔The research on low-cost materials emitting in the near infrared ͑NIR͒ is receiving a great deal of renewed interest for their potential in local and premise optical communication networks, and imaging and sensing applications. Among these materials, organolanthanides are very promising candidates as they combine the well-established NIR emission properties of Ln 3+ ions with the unique optical 1,2 and electrical response 3 of organic semiconductors, coupled with their easy processability.Excitation processes in lanthanide complexes differ considerably from those in inert glasses doped with transition metals. Due to the large absorption cross section of the allowed − * optical transitions, the organic ligand acts as an efficient light harvester in the ultraviolet-visible spectral window. From the organic photonic antenna the electronic excitations are quickly transferred to the rare-earth ion. The twostep excitation process permits the achievement of a large excited-state population using light fluences four to five orders of magnitude lower than those required for bare ions. Ligands also prevent deleterious formation of metal clusters, allowing the deposition of thin films with Ln 3+ densities as large as 10 21 ions/ cm 3 . All these properties make organolanthanides very attracting for the development of low-cost light sources and infrared amplifiers to integrate in planar photonic circuits for optical communications, where light signals can be generated, amplified, and processed. [1][2][3][4][5] The major drawback of these materials is related to the presence of efficient nonradiative deactivation channels, which shorten the erbium population lifetime from milliseconds to microseconds. 1,2 NIR emission quenching mainly results from the coupling of the excited state of the Ln 3+ ion with high frequency vibrations of CH and OH groups. 6 Substitution of hydrogen with heavier halogen atoms lowers the vibration frequencies and, hence, represents a possible strategy to reduce the induced emission quenching. Investigations on halogenated systems show an unambiguous improvement of the NIR light emission. 7,8 The best performances have been obtained in perfluorinated ͑PF͒ systems, which show nonradiative decay times in the submillisecond timescale. 9 NIR emission quantum yield has been drastically enhanced, but remains, however, rather low, around a few percent. Whether these results can be further impro...