Counterfeit goods represent a major problem to companies, governments, and customers, affecting the global economy. In order to protect the authenticity of products and documents, optical anti‐counterfeit technologies have widely been employed via the use of discrete molecular species, extended metal–organic frameworks (MOFs), and nanoparticles. Herein, for the first time we demonstrate the potential use of molecular cluster‐aggregates (MCA) as optical barcodes via composition and energy transfer control. The tuneable optical properties for the [Ln20(chp)30(CO3)12(NO3)6(H2O)6], where chp−=deprotonated 6‐chloro‐2‐pyridinol, allow the fine control of the emission colour output, resulting in high‐security level optical labelling with a precise read‐out. Moreover, a unique tri‐doped composition of GdIII, TbIII, and EuIII led to MCAs with white‐light emission. The presented methodology is a unique approach to probe the effect of composition control on the luminescent properties of nanosized molecular material.

(1c), were prepared and the electronic structure of the oneelectron oxidized species [1a-c] + were investigated in solution. The solid-state structures of 1a and 1b were solved by X-ray crystallography, and in the case of 1b an asymmetric UO2 2+ unit was found due to an intermolecular hydrogen bonding interaction. Electrochemical investigation of 1a-c by cyclic voltammetry showed that each complex exhibited at least one quasi-reversible redox process assigned to the oxidation of the phenolate moieties to phenoxyl radicals. The trend in redox potentials matches the electron-donating ability of the para-phenolate substituents. The electron paramagnetic resonance spectra of cations

Amidine-based ligand frameworks were employed to isolate a series of mononuclear lanthanide complexes. The employed N-2-pyridyl­imidoyl-2-pyridyl­amidine (Py2ImAm) undergoes metal-assisted hydrolysis yielding the ligand 2-amidino­pyridine (PyAm), which coordinates to the lanthanide ions affording [Ln­(acac)3(PyAm)], where Ln = Eu­(III) (1), Gd­(III) (2), Tb­(III) (3), Dy­(III) (4) along with the Y­(III) analogue (5). The Eu­(III), Tb­(III), and Dy­(III) congeners exhibit characteristic emissions of red, green, and yellow light, respectively, with emission quantum yields of 3, 65, and 8%, respectively. Due to changes in the thermal population of the Stark sublevels, the Tb­(III) and Dy­(III) complexes can be used as efficient optical thermometers with maximum relative sensitivities of 1.57 and 2.03% K–1 for 3 and 4, respectively. These results demonstrate the viability of PyAm as an antenna for the sensitization of lanthanide ions.

Trivalent lanthanide ions (Ln 3+ ) are used to prepare a plethora of coordination compounds; metal-organic frameworks (MOFs) being amongst the most sought-after in recent years. The porosity of Ln-MOFs is often complemented by the luminescence imparted by the metal centers, making them attractive multifunctional materials. Here, we report a class of 3D MOFs obtained from solvothermal reaction between 2,6-naphtalenedicarboxylic acid (H 2 NDC) and lanthanide chlorides yielding three types of compounds depending on the chosen lanthanide: [LnCl(NDC)(DMF)] for Ln 3+ = La 3+ , Ce 3+ , Pr 3+ , Nd 3+ , Sm 3+ (type 1), [Eu(NDC) 1.5 (DMF)]•0.5DMF (type 2), and [Ln 2 (NDC) 3 (DMF) 2 ] (type 3) for Ln 3+ = Tb 3+ , Dy 3+ , Y 3+ , Er 3+ , Yb 3+ . Photoluminescent properties of selected phases were explored at room temperature. The luminescence thermometry capability of Yb 3+ -doped Nd-MOF was fully investigated in the 15-300 K temperature range under 365 and 808 nm excitation. To describe the optical behavior of the isolated MOFs, we introduce the total energy transfer balance model. Therein, the sum of energy transfer rates is considered along with its dependence upon the temperature: sign, magnitude, and variation of this parameter, permitting to afford a thorough interpretation of the observed behavior of the luminescent species of all materials presented here. The combination of novel theoretical and experimental studies presented herein to describe energy transfer processes in luminescent materials can pave the way towards the design of MOF-based chemical and physical sensors working in an optical range of interest for biomedical applications.

The [(n)Bu(4)N][AuX(2)(CN)(2)] (X = Br, I) salts were synthesized and structurally characterized. Both feature square-planar [AuX(2)(CN)(2)](-) anions, with trans cyano and halo ligands, which aggregate via halogen-halogen interactions. The aggregation of [AuX(2)(CN)(2)](-) units results in the parallel alignment of all of the Br-Au-Br moieties in the anions along the [110] and [110] directions. Two crystal habits of [(n)Bu(4)N][AuBr(2)(CN)(2)] were grown: with (110) and (001) as the primary faces. The birefringence in the (110) plane was found to be Δn = 0.051(4) and was <0.03 in the (001) plane. Using the [AuBr(2)(CN)(2)](-) unit, [M(phen)(2)][AuBr(2)(CN)(2)](2) (M = Fe, Ni), [Ni(terpy)(2)][AuBr(2)(CN)(2)](2), [Fe(terpy)(2)][AuBr(2)(CN)(2)][ClO(4)], and [Cu(phen)(2)(NO(3))][AuBr(2)(CN)(2)] (phen = 1,10-phenanthroline, terpy = 2,2';6',2''-terpyridine) were synthesized and structurally characterized: they formed ionic structures with coordinatively saturated metal cations and structurally aligning Br···Br interactions between the [AuBr(2)(CN)(2)](-) anions. A molecular complex, Cu(terpy)[AuBr(2)(CN)(2)](2), was prepared, as well as the coordination polymer, [Ni(en)(2)(AuBr(2)(CN)(2))][AuBr(2)(CN)(2)]·MeOH (en = ethylenediamine). The structure consists of layers of chains of Ni(en)(2)(AuBr(2)(CN)(2))(+) units and chains of unbound [AuBr(2)(CN)(2)](-) units formed via Br···Br interactions; a Δn = 0.131(3) was measured. The Δn values were related to the supramolecular structures in terms of the relative intermolecular alignment of Br-Au-Br and NC-Au-CN bonds. These measurements both demonstrate the utility of the Au-Br bonds in enhancing birefringence and show that the contribution of the M-CN units to the overall birefringence of cyanometallate coordinations polymers is non-negligible.